Seasonal Aspects of Radiative and Advective Air Temperature Populations: A Canadian Perspective

Abstract

Canadian high-frequency temperature time series exhibit physical heterogeneity in the coexistence of radiative and advective populations in the total air temperature sample. This work examines forty-five Canadian hourly air temperature records to study seasonal characteristics and variability of radiative and advective population counts and their corresponding temperature biases and trends. The Linear Pattern Discrimination algorithm, conceptualized in a previous study, was adjusted to seasonal analysis on the equinox-to-equinox time scale. Count analysis of radiative and advective days supports the existence of two distinct thermal regimes, Spring–Summer and Fall–Winter. Further, seasonal advective counts for the majority of examined stations typically decrease in numbers. The consistently warmer winter radiative temperature extrema points to the critical role of the advective population in control of the overall temperature magnitude. Canadian northwest warming trends are found to be the highest, indicating the amplifying effect of decreasing advective counts with rapidly increasing temperatures that weaken the advective population’s moderating ability to control the magnitude of the total temperature population.

1. Introduction

The observed increase in global air temperature, complicated by intensified changes in weather patterns, presents a complex climatological construct for analysis [1,2]. While the clear demarcation of climate from the weather is far from reach, the apparent changes in daily temperature variation lend themselves to the delimitation of homogeneous air temperature populations within the temperature time series.

The identification of different populations within temperature time series is of great importance for the analysis of climatic variation apart from weather anomalies. There has not been a known attempt until recently, to divide the total temperature sample based on the diurnal temperature pattern. Although a notion of a diurnal temperature pattern (DTP) deduced from daily extrema exists [3,4], the correlation of a DTP with common atmospheric drivers of daily air temperature variation presents a novel concept initially introduced in [5].

The previous research has extensively examined a typical temperature variation for the purpose of temperature modeling covering various scientific fields and applications [6,7,8,9,10,11,12,13]. Additionally, the majority of works related to the quality of air temperature time series focus on the identification and elimination of artificial inhomogeneities [14,15,16,17,18,19,20,21]. A traditional approach to the elimination of non-climatic effects from an air temperature time series routinely overlooks the coexistence of different temperature populations. However, variation in the shape of the daily temperature curve between the commonly encountered sinusoidal and less frequent, quasi-linear diurnal temperature distribution provides convincing evidence for the presence of physically different air temperature populations within the temperature time series.

Physical heterogeneity of the Long-Term High-Frequency (LTHF) time series refers to the presence of more than one population characterized by a unique DTP that reflects the dominant daily heat exchange mechanism. Radiative and advective air temperature populations within the LTHF time series represent, therefore, the homogeneous parts of the total temperature sample consisting only of days with orderly or distorted DTP.

This study builds on an earlier implementation of the Linear Pattern Discrimination (LPD) algorithm in [5] preliminary used for the separation of temperature time series to physically homogeneous populations. While the initial study [5] reported on the design and implementation of the LPD algorithm and annual analysis of radiative and advective populations, the unique aspect of this study is the alteration of the annual algorithm to accommodate the seasonal analysis of extrema time series. The alteration consists of an adjustment to the astronomical calendar for identifying radiative and advective days on the equinox-to-equinox time scale for seasonal and semi-annual time steps.

This work aims to identify the main thermal characteristics of seasonal temperature populations through analysis of radiative and advective day counts and trend analysis of radiative and advective temperature populations within major Canadian climate regions.

Seasonal analysis of the Canadian radiative and advective extrema series identified large positive temperature trends across the stations. Time evolution of air temperature population counts and particularly high warming rates at Canadian northwest stations indicate an increase in atmospheric heat retention based on the fact that the most intense changes are observed on orderly, radiative days. Additionally, the consistently warmer Fall–Winter radiative extrema indicate the diminishment of the critical “cooling” role of the advective population in controlling the magnitude of the total temperature sample.

2. Materials and Methods

Forty-five long-term records of air temperature data used in this work were obtained from the archive maintained by Environment and Climate Canada [22] (https://climate.weather.gc.ca/historical_data (accessed on 10 April 2022)). Hourly air temperature time series, recorded at international and local airports (Environment and Climate Change Canada, 2022) were chosen for their availability of unaltered high-frequency records. The climate stations identified in Figure 1 were selected to represent the majority of Canadian climate regions presented in Figure 2.

Table 1. List of climate stations with latitude, longitude, data range, and percentage of missing data. “PD” represents “political division”. AB—Alberta, BC—British Columbia, MB–Manitoba, NB—New Brunswick, NL—Newfoundland and Labrador, NS—Nova Scotia, NT—Northwest Territories, NU—Nunavut, ON—Ontario, PE—Prince Edward Island, QC—Quebec, SK—Saskatchewan, and YU—Yukon.

#	PD	Station Name	Latitude (°N)	Longitude (°W)	Data Range	Missing Data (%)
1	AB	Calgary	51.11	114.02	1953–2021	0.04
2		Cold Lake	54.42	110.28	1955–2021	0.10
3		Fort McMurray	56.65	111.22	1953–2021	0.35
4	BC	Abbotsford	49.03	122.36	1953–2021	0.14
5		Comox	49.72	124.90	1953–2021	0.05
6		Fort Nelson	58.84	122.60	1953–2021	0.10
7		Port Hardy	50.68	127.37	1953–2021	0.08
8		Vancouver	49.20	123.18	1953–2021	0.03
9		Victoria	48.65	123.43	1953–2021	0.07
10	MB	Churchill	58.74	94.07	1953–2021	0.17
11		The Pas	53.97	101.09	1953–2021	0.12
12		Winnipeg	49.92	97.23	1953–2021	0.06
13	NB	Fredericton	45.88	66.53	1953–2021	0.13
14		Moncton	46.11	64.68	1953–2021	0.03
15		Saint John	45.32	65.89	1953–2021	0.06
16	NL	Gander	48.95	54.58	1953–2021	0.03
17		Goose	53.71	57.04	1953–2021	0.06
18		St. John’s	47.62	52.74	1959–2021	0.05
19	NS	Greenwood	44.98	64.92	1953–2021	0.05
20		Yarmouth	43.83	66.09	1953–2021	0.16
21	NT	Fort Smith	60.02	111.96	1953–2021	0.10
22		Hay River	60.84	115.78	1953–2021	0.15
23		Norman Wells	65.28	126.80	1956–2021	0.13
24		Yellowknife	62.27	114.26	1953–2021	0.05
25	NU	Baker Lake	64.30	96.08	1963–2021	0.71
26		Iqaluit	63.75	69.10	1953–2021	0.13
27	ON	Kapuskasing	49.41	82.47	1953–2021	0.13
28		Kenora	49.79	94.37	1953–2021	0.12
29		Ottawa	45.32	75.67	1953–2021	0.05
30		Sioux Lookout	50.12	91.90	1953–2021	0.13
31		Toronto	43.68	79.63	1953–2021	0.03
32		Trenton	44.12	77.53	1953–2021	1.49
33		Wiarton	44.75	81.11	1953–2021	0.31
34		Windsor	42.28	82.96	1953–2021	0.09
35	PE	Charlottetown	46.17	63.07	1953–2021	0.13
36	QC	Bagotville	48.33	71.00	1953–2021	0.04
37		Kuujjuaq	58.10	68.42	1953–2021	0.05
38		Montreal	45.28	73.44	1953–2021	0.03
39	SK	Estevan	49.22	102.97	1953–2021	0.07
40		Prince Albert	53.22	105.67	1953–2021	0.10
41		Regina	50.43	104.67	1953–2021	0.03
42		Saskatoon	52.17	106.72	1953–2021	0.06
43		Yorkton	51.27	102.46	1953–2021	0.21
44	YU	Watson Lake	60.12	128.82	1953–2021	0.39
45		Whitehorse	60.71	135.07	1953–2021	0.04

lists the station’s geographic coordinates, data ranges, and percentages of missing data. Locations of stations range from 42.3° N (Windsor) to 65.3° N (Norman Wells) in latitude and from 52.3° W (St. John’s) to 135.1° W (Whitehorse) in longitude. The majority of temperature records span over 69 years in length except for Baker Lake, St. John’s, Norman Wells, and Cold Lake stations with records ranging between 58 and 66 years. The percent of missing data for the stations used varied from 0.03 (Gander, Moncton, Toronto, Regina, Vancouver) to 1.49 (Trenton) percent of hourly temperature measurements.

Data processing, statistical analysis and graphical presentation were conducted in R programming environment using ‘dplyr’, ‘stringr’, ‘Kendall’, ‘ggplot2′, and ‘gridExtra’ packages [23].

The following subsection briefly describes the methodology previously used in [5] applied in this work to seasonal analysis and an extended number of stations.

Framework for Seasonal Analysis of Homogeneous Air Temperature Populations

The seasonal analysis of physically homogeneous temperature populations consists of several procedures presented in Figure 3. Daily mathematical minima and maxima are derived from hourly records using the Climatological Observing Window_Night-Day (COW_ND), a time frame for extrema identification conceptualized in [24]. Daily minima and maxima pairs (t, T), which consist of timing and temperature of a nighttime minimum (Nt_n, NT_n) and timing and temperature of a daily maximum (Dt_x, DT_x), were identified at points on the air temperature–time curve where daily temperature trend changes its sign, and the derivative of temperature function equals zero [24].

Identified mathematical extrema form a chronologically ordered sequence of daily temperature–time extrema pairs that is subsequently subjected to the LPD algorithm.

A radiatively-driven daily air temperature variation is represented by a sinusoidal diurnal temperature pattern that is compliant with the daily solar cycle and characterized by a nighttime minimum and daytime temperature maximum. An advectively driven temperature variation is, on the other hand, represented by a quasi-linear temperature pattern, caused by the horizontal transport of cold or warm air. Typical advective days are characterized by either nearly equal diurnal extrema timing identified at sunrise or sunset delineations (1 to 4 h apart) or diametrically distant points (more than 20 h apart) at end-of-day intervals.

The identification of a Diurnal Temperature Pattern (DTP) with the LPD algorithm is performed through the evaluation of extrema pairs at each transition between consecutive daytime and nighttime periods. In this methodology, the DTP serves as a separation tool for delineation of “orderly”, i.e., radiatively-driven days from days with a DTP distorted by thermal advection. Timing (t) of daily extrema is used as the main criterion for the DTP identification and partitioning of advective days from the total temperature population. The LPD algorithm identifies four common theoretical cases of advectively driven daily air temperature variation conceptualized in [5], Case 11, Case 12, Case 21, and Case 22, each describing a specific type of a quasi-linear DTP characterizing an advective day. The timing criterion (dt) for the separation of radiative and advective temperature populations is 4 h. Contrary to advective days, radiative days as a rule exhibit an orderly DTP with a clear separation in the timing of a minimum and maximum. The LPD algorithm selects the days with minima and maxima that are found within the time interval of 4 h apart and feeds them into the advective population while labeling the remaining days with daily extrema with 4 to 20 h apart as radiative (Case 0) to assign them to the radiative population (Figure 3).

The chronological series of radiative and advective days are identified according to the astronomical calendar. Seasonal demarcation for the identification of temperature populations is based on the exact solstice and equinox times.

Aspects of seasonal analysis in this study encompass the evolution of population counts and identification of radiative and advective temperature population trends and biases. The examination of total and individual homogeneous air temperature population trends involves the nonparametric Mann–Kendall (MK) trend test in the R programming language. The MK test is commonly used for assessing the significance of monotonic trends in variables with no assumption on the data to be normally distributed.

The scope of the assessment includes the analysis of seasonally averaged population counts followed by the analysis of total, radiative and advective populations of minimum and maximum temperatures.

3. Results

The results of the seasonal analysis of population counts and temperature biases and trends are presented in this section by climate regions.

Section 3.1 consists of a brief discussion of seasonal radiative and advective counts at individual stations, while Section 3.2 looks at the time evolution of seasonally averaged trends of population counts. Section 3.3 analyzes the magnitude of air temperature bias between homogeneous temperature populations and discusses radiative and advective temperature trends.

Table 2. Radiative population counts, radiative population participation, and radiative population slope of counts reported per century (#/c.) “m” represents “slope”. RPC—Radiative Population Count, RPP—Radiative Population Participation, and mRP_c—Slope of Radiative Population Count. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Station Name	Annual			Spring			Summer			Fall			Winter
		RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)
ATL	Charlottetown	19,705	78.2	0	5695	89.7	0	6061	95.4	0	4267	67.8	0	3682	59.4	0
ATL	Fredericton	22,201	88.1	7	6062	95.5	−2	6209	97.7	1	5144	81.7	3	4786	77.2	5
ATL	Gander	18,337	81.0	10	451	7.9	4 *	332	5.8	0	1663	29.4	4	1865	33.3	2
ATL	Greenwood	21,185	84.1	15 *	5969	94.2	0	6187	97.4	2	4831	76.7	6	4198	67.7	7
ATL	Moncton	21,505	85.4	14 *	5913	93.2	3	6183	97.3	1	4923	78.3	2	4486	72.4	8 *
ATL	Saint John	21,173	84.0	3	5874	92.5	1	6061	95.5	0	4751	75.5	−2	4487	72.4	4
ATL	St. John’s	17,009	75.1	14	4985	87.5	0	5202	91.0	2	3623	64.3	7	3199	57.2	5
ATL	Yarmouth	20,042	80.0	5	5765	91.0	2	5998	94.4	3	4496	71.5	−3	3783	61.0	3
GRL	Montreal	21,054	83.6	6	5955	93.9	1	6166	97.1	2	4822	76.5	3	4111	66.3	0
GRL	Ottawa	21,661	86.0	10	6000	94.6	0	6202	97.7	2 *	5028	80.0	3	4431	71.4	5
GRL	Toronto	21,568	85.6	0	5942	93.7	−1	6198	97.6	0	5023	80.0	−2	4405	71.0	3
GRL	Trenton	21,575	85.6	−3	5964	93.9	−4	6120	96.4	−2	4988	79.2	1	4503	72.7	2
GRL	Wiarton	19,637	78.0	19 *	5578	88.0	0	5982	94.2	3 *	4366	69.4	7	3711	60.0	9 *
GRL	Windsor	21,697	86.1	−1	5885	92.8	0	6192	97.4	0	5135	81.6	0	4485	72.3	−1
NEF	Bagotville	20,766	82.4	10	5984	94.3	3	6109	96.1	1	4487	71.2	4	4186	67.6	2
NEF	Churchill	18,107	71.1	48 *	5314	82.7	7 *	5514	85.9	13 *	3638	57.3	16 *	3641	58.1	12
NEF	Goose	20,866	82.8	23 *	5911	93.2	0	6008	94.6	3	4619	73.4	12 *	4328	69.8	8
NEF	Kapuskasing	21,301	84.6	11 *	5955	93.8	4 *	6111	96.2	0	4614	73.4	8 *	4621	74.6	−1
NEF	Kenora	21,388	84.9	12 *	6007	94.6	4 *	6150	96.7	1	4612	73.3	2	4619	74.5	5
NEF	Sioux Lookout	21,218	84.2	22 *	5967	94.0	4 *	6071	95.6	3	4527	72.0	8 *	4653	75.1	7
NWF	Cold Lake	21,790	89.1	16 *	5990	97.2	0	6046	98.1	2 *	5076	83.0	6 *	4678	77.8	8
NWF	Fort McMurray	22,031	87.5	14 *	6166	97.1	2	6252	98.5	2 *	4951	78.5	5	4662	75.3	5
NWF	Fort Nelson	21,912	87.0	4	6156	97.0	−1	6222	98.0	1	4862	77.2	3	4672	75.4	1
NWF	The Pas	21,168	84.0	17 *	5924	93.3	1	6085	95.8	1	4631	73.6	7 *	4528	73.1	8
PRA	Calgary	22,539	89.5	16 *	6095	96.0	−1	6183	97.4	3 *	5317	84.5	3	4944	79.7	11 *
PRA	Estevan	22,113	87.8	7	6054	95.5	3	6251	98.5	2 *	5262	83.5	1	4546	73.3	1
PRA	Prince Albert	22,172	88.0	4	6087	96.0	1	6246	98.3	0	5149	81.7	1	4690	75.7	2
PRA	Regina	22,029	87.5	14 *	6069	95.7	3 *	6241	98.3	1 *	5224	82.9	−1	4495	72.5	11
PRA	Saskatoon	22,035	87.5	11	6096	96.2	2	6269	98.7	1	5168	82.0	1	4502	72.6	7
PRA	Winnipeg	21,219	84.2	11 *	5988	94.4	4	6226	98.0	1	4835	76.8	1	4170	67.2	5
PRA	Yorkton	21,663	86.0	9	6037	95.3	2	6251	98.5	1	5009	79.5	2	4366	70.4	4
SBC	Abbotsford	22,778	90.4	22 *	6194	97.7	1	6287	98.9	0	5254	83.5	6 *	5043	81.3	15 *
PAC	Comox	22,360	88.8	18 *	6135	96.8	3 *	6240	98.2	2 *	5064	80.4	7 *	4921	79.4	6
PAC	Port Hardy	22,061	87.6	19 *	6136	96.9	0	6149	96.7	2	4891	77.7	6 *	4885	78.7	11 *
PAC	Vancouver	22,616	89.8	14 *	6193	97.6	2	6243	98.2	1	5155	81.9	6 *	5025	81.0	5
PAC	Victoria	22,799	90.5	17 *	6192	97.7	0	6231	98.0	2 *	5257	83.6	4	5119	82.5	11 *
NBC	Watson Lake	21,269	84.4	13 *	6225	98.2	0	6263	98.6	0	4481	71.1	10 *	4300	69.4	3
NBC	Whitehorse	20,703	82.2	17 *	6276	98.9	1	6283	98.9	0	4131	65.6	5	4013	64.8	11 *
MCD	Fort Smith	20,650	82.0	19 *	6107	96.3	2	6192	97.5	1	4248	67.3	8 *	4103	66.3	8 *
MCD	Hay River	19,657	78.0	21 *	5682	89.6	6 *	6004	94.6	4 *	4167	66.0	10 *	3804	61.4	1
MCD	Norman Wells	18,611	77.2	9	5738	94.6	−1	5741	94.5	−1	3694	61.3	8 *	3438	57.9	3
MCD	Yellowknife	19,388	77.0	17 *	6003	94.6	5 *	6068	95.6	0	3620	57.4	7	3697	59.7	5
ART	Baker Lake	17,106	75.5	20 *	5142	90.2	2	5480	95.9	3	3290	58.2	8 *	3194	57.2	7
ART	Kuujjuaq	19,613	77.9	22 *	5693	89.7	4 *	6014	94.7	0	4068	64.6	7 *	3838	61.9	11 *
ARM	Iqaluit	19,337	76.8	9	5806	91.6	−1	6004	94.4	0	3860	61.4	5	3667	59.1	5

* Statistically significant trends.

and

Table 3. Advective population counts, advective population participation, and advective population slope of counts reported per century (#/c.) “m” represents “slope”. APC—Advective Population Count, APP—Advective Population Participation, and mAP_c—Slope of Advective Population Count. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Station Name	Annual			Spring			Summer			Fall			Winter
		APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)
ATL	Charlottetown	5486	21.8	0	651	10.3	0	295	4.6	0	2026	32.2	0	2514	40.6	0
ATL	Fredericton	2990	11.9	−7	283	4.5	2	144	2.3	−1	1151	18.3	−3	1412	22.8	−5
ATL	Gander	4311	19.0	−10	451	7.9	−4 *	332	5.8	0	1663	29.4	−4	1865	33.3	−2
ATL	Greenwood	4006	15.9	−15 *	368	5.8	0	168	2.6	−2	1465	23.3	−6	2005	32.3	−7
ATL	Moncton	3686	14.6	−14 *	432	6.8	−3	171	2.7	−1	1370	21.8	−2	1713	27.6	−8 *
ATL	Saint John	4018	16.0	−3	478	7.5	−1	287	4.5	0	1542	24.5	2	1711	27.6	−4
ATL	St. John’s	5638	24.9	−14	711	12.5	0	516	9.0	−2	2016	35.7	−7	2395	42.8	−5
ATL	Yarmouth	5150	20.0	−5	585	9.2	−2	353	5.6	−3	1793	28.5	3	2419	39.0	−3
GRL	Montreal	4137	16.4	−6	387	6.1	−1	181	2.8	−2	1482	23.5	−3	2087	33.7	0
GRL	Ottawa	3529	14.0	−10	342	5.4	0	148	2.3	−2 *	1266	20.1	−3	1773	28.6	−5
GRL	Toronto	3622	14.4	0	401	6.3	1	150	2.4	0	1272	20.2	2	1799	29.0	−3
GRL	Trenton	3615	14.3	3	387	6.1	4	225	3.5	2	1310	20.8	−1	1693	27.3	−2
GRL	Wiarton	5553	22.0	−19 *	761	12.0	0	370	5.8	−3 *	1923	30.6	−7	2499	40.2	−9 *
GRL	Windsor	3494	13.9	1	454	7.2	0	165	2.6	0	1157	18.4	0	1718	27.7	1
NEF	Bagotville	4424	17.6	−10	362	5.7	−3	247	3.9	−1	1813	28.8	−4	2002	32.4	−2
NEF	Churchill	7359	28.9	−48 *	1108	17.3	−7 *	904	14.1	−13 *	2716	42.7	−16 *	2631	41.9	−12
NEF	Goose	4324	17.2	−23 *	429	6.8	0	343	5.4	−3	1677	26.6	−12 *	1875	30.2	−8
NEF	Kapuskasing	3889	15.4	−11 *	392	6.2	−4 *	244	3.8	0	1676	26.6	−8 *	1577	25.4	1
NEF	Kenora	3803	15.1	−12 *	340	5.4	−4 *	208	3.3	−1	1676	26.7	−2	1579	25.5	−5
NEF	Sioux Lookout	3972	15.8	−22 *	382	6.0	−4 *	283	4.5	−3	1761	28.0	−8 *	1546	24.9	−7
NWF	Cold Lake	2671	10.9	−16 *	173	2.8	0	120	1.9	−2 *	1043	17.0	−6 *	1335	22.2	−8
NWF	Fort McMurray	3159	12.5	−14 *	181	2.9	−2	97	1.5	−2 *	1353	21.5	−5	1528	24.7	−5
NWF	Fort Nelson	3278	13.0	−4	189	3.0	1	128	2.0	−1	1436	22.8	−3	1525	24.6	−1
NWF	The Pas	4023	16.0	−17 *	423	6.7	−1	269	4.2	−1	1663	26.4	−7 *	1668	26.9	−8
PRA	Calgary	2652	10.5	−16 *	252	4.0	1	162	2.6	−3 *	977	15.5	−3	1261	20.3	−11 *
PRA	Estevan	3077	12.2	−7	286	4.5	−3	98	1.5	−2 *	1037	16.5	−1	1656	26.7	−1
PRA	Prince Albert	3018	12.0	−4	256	4.0	−1	109	1.7	0	1150	18.3	−1	1503	24.3	−2
PRA	Regina	3161	12.5	−14 *	271	4.3	−3 *	107	1.7	−1 *	1074	17.1	1	1709	27.5	−11
PRA	Saskatoon	3155	12.5	−11	243	3.8	−2	85	1.3	−1	1131	18.0	−1	1696	27.4	−7
PRA	Winnipeg	3971	15.8	−11 *	353	5.6	−4	125	2.0	−1	1461	23.2	−1	2032	32.8	−5
PRA	Yorkton	3527	14.0	−9	300	4.7	−2	98	1.5	−1	1294	20.5	−2	1835	29.6	−4
SBC	Abbotsford	2412	9.6	−22 *	146	2.3	−1	69	1.1	0	1036	16.5	−6 *	1161	18.7	−15 *
PAC	Comox	2831	11.2	−18 *	204	3.2	−3 *	113	1.8	−2 *	1234	19.6	−7 *	1280	20.6	−6
PAC	Port Hardy	3129	12.4	−19 *	196	3.1	0	209	3.3	−2	1405	22.3	−6 *	1319	21.3	−11 *
PAC	Vancouver	2574	10.2	−14 *	150	2.4	−2	112	1.8	−1	1137	18.1	−6 *	1175	19.0	−5
PAC	Victoria	2392	9.5	−17 *	148	2.3	0	126	2.0	−2 *	1033	16.4	−4	1085	17.5	−11 *
NBC	Watson Lake	3923	15.6	−13 *	117	1.8	0	91	1.4	0	1819	28.9	−10 *	1896	30.6	−3
NBC	Whitehorse	4488	17.8	−17 *	68	1.1	−1	71	1.1	0	2165	34.4	−5	2184	35.2	−11 *
MCD	Fort Smith	4541	18.0	−19 *	236	3.7	−2	156	2.5	−1	2062	32.7	−8 *	2087	33.7	−8 *
MCD	Hay River	5534	22.0	−21 *	657	10.4	−6 *	341	5.4	−4 *	2142	34.0	−10 *	2394	38.6	−1
MCD	Norman Wells	5495	22.8	−9	329	5.4	1	336	5.5	1	2334	38.7	−8 *	2496	42.1	−3
MCD	Yellowknife	5803	23.0	−17 *	340	5.4	−5 *	282	4.4	0	2688	42.6	−7	2493	40.3	−5
ART	Baker Lake	5539	24.5	−20 *	559	9.8	−2	235	4.1	−3	2360	41.8	−8 *	2385	42.7	−7
ART	Kuujjuaq	5577	22.1	−22 *	653	10.3	−4 *	339	5.3	0	2226	35.4	−7 *	2359	38.1	−11 *
ARM	Iqaluit	5854	23.2	−9	529	8.4	1	353	5.6	0	2431	38.6	−5	2541	40.9	−5

* Statistically significant trends.

display radiative and advective population counts while

Table 4. Temperature Minima Slopes reported in degrees Celsius per century (°C/c.) “m” represents “slope”. mTT_n—Slope of Total Temperature Minimum, mRT_n—Slope of Radiative Temperature Minimum, and mAT_n—Slope of Advective Temperature Minimum. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Station Name	Annual			Spring			Summer			Fall			Winter
		mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)
ATL	Charlottetown	1.6 *	1.5 *	2.2 *	1.3 *	1.2 *	1.9	2.6 *	2.6 *	3.9 *	1.5 *	1.0	2.6 *	1.4	1.0	2.1
ATL	Fredericton	1.4 *	1.1 *	2.9 *	1.1 *	1.1	3.1	1.8 *	1.8 *	2.1	1.5 *	0.9	3.8 *	1.3	1.0	2.6
ATL	Gander	1.6 *	1.7 *	0.5	0.6	0.6	1.1	2.7 *	2.8 *	1.0	1.8 *	2.2 *	0.4	1.5	1.5	1.5
ATL	Greenwood	2.2 *	2.1 *	1.0	2.0 *	2.1 *	1.9	3.6 *	3.6 *	4.3	1.8 *	1.7 *	1.4	1.5	1.6	1.3
ATL	Moncton	1.8 *	1.6 *	1.6	1.5 *	1.3 *	3.7	3.0 *	3.0 *	3.7	1.6 *	1.6 *	1.5	1.2	1.6	1.0
ATL	Saint John	0.7	0.4	1.9	0.6	0.5	1.4	0.9 *	0.9 *	2.2	0.4	−0.1	1.9	0.9	0.8	1.8
ATL	St. John’s	1.5 *	1.6 *	0.8	0.8	0.6	1.1	2.6 *	2.7 *	1.0	1.4 *	2.0 *	0.0	1.3	1.0	1.9
ATL	Yarmouth	1.8 *	1.8 *	1.5 *	1.6 *	1.5 *	3.0	2.9 *	2.9 *	4.2 *	1.8 *	1.8 *	1.9 *	1.2	1.0	1.2
GRL	Montreal	2.8 *	2.9 *	1.7 *	2.4 *	2.3 *	1.4	3.4 *	3.3 *	6.5 *	2.1 *	2.2 *	1.7	3.7 *	3.7 *	3.3 *
GRL	Ottawa	1.8 *	1.5 *	1.4	1.3	1.3	2.3	1.5 *	1.5 *	1.7	1.4	1.3	1.3	3.1 *	3.2 *	2.7
GRL	Toronto	4.5 *	4.5 *	4.5 *	4.1 *	4.1 *	4.9 *	5.6 *	5.6 *	1.0	3.9 *	3.8 *	4.7 *	4.4 *	4.6 *	4.1 *
GRL	Trenton	1.9 *	1.3 *	4.6 *	1.7	1.4	2.7	2.2 *	2.1 *	3.0	1.0	0.5	2.5	2.6 *	2.2	4.1 *
GRL	Wiarton	1.6	1.0	2.3 *	1.4	1.2	2.6	1.4 *	1.4 *	1.9	1.1	0.1	2.5 *	2.9 *	2.7 *	3.0 *
GRL	Windsor	2.4 *	2.4 *	3.0 *	2.5 *	2.4 *	2.8	2.9 *	2.8 *	5.8 *	2.1 *	1.7	3.2 *	2.4	2.3	2.5
NEF	Bagotville	2.4 *	2.3 *	1.4	1.6 *	1.7 *	−3.3	3.0 *	3.0 *	3.8	2.1 *	2.2 *	1.6	3.0 *	2.8 *	3.7
NEF	Churchill	4.2 *	3.8 *	1.9	3.3 *	3.2 *	3.2	2.4 *	2.1 *	2.3	4.6 *	3.1	2.9	4.5 *	4.4 *	4.8 *
NEF	Goose	1.8	1.3	1.9	1.3	1.1	5.2 *	2.5 *	2.5 *	1.9	2.8 *	2.5 *	2.3	0.6	0.5	1.6
NEF	Kapuskasing	2.5 *	2.3 *	2.4 *	1.5	1.4	0.6	2.9 *	2.9 *	2.5	2.1	1.5	2.3	4.0 *	2.9	6.8 *
NEF	Kenora	2.9 *	2.6 *	2.7 *	2.4 *	2.2 *	3.7	2.8 *	2.8 *	1.3	2.1	2.0	2.4	4.8 *	4.7 *	5.4 *
NEF	Sioux Lookout	2.6 *	2.3 *	1.3	1.9	1.5	4.3	2.0 *	2.0 *	1.2	2.2	2.3	1.1	4.8 *	5.2 *	4.8 *
NWF	Cold Lake	2.9 *	2.2 *	4.3 *	1.4 *	1.4	4.2	2.0 *	2.0 *	−0.7	2.3	1.5	3.3	6.2 *	6.2 *	6.4 *
NWF	Fort McMurray	3.9 *	3.5 *	3.3 *	3.3 *	3.3 *	2.9	3.0 *	2.9 *	3.5	2.1	2.2	1.1	7.3 *	7.1 *	8.8 *
NWF	Fort Nelson	3.1 *	2.8 *	5.1 *	2.0 *	1.9 *	5.8	1.3 *	1.3 *	4.9	2.8 *	2.4 *	3.3	6.6 *	6.4 *	7.7 *
NWF	The Pas	3.0 *	2.4 *	3.3 *	1.8	1.6	2.9	2.4 *	2.3 *	3.8	1.8	1.8	0.4	6.4 *	6.7 *	6.3 *
PRA	Calgary	2.9 *	2.3 *	3.9 *	2.0 *	2.0 *	1.7	2.4 *	2.3 *	−0.1	2.4 *	1.7	4.6	5.0 *	4.7 *	4.2
PRA	Estevan	0.0	−0.1	−0.1	−0.1	−0.3	0.9	−0.3	−0.4	2.3	−0.9	−1.0	−0.8	1.8	1.2	3.6 *
PRA	Prince Albert	3.8 *	3.6 *	4.2	2.7 *	2.7 *	6.1	2.5 *	2.4 *	6.8 *	2.6 *	2.6 *	2.9	7.5 *	7.9 *	6.2 *
PRA	Regina	1.6 *	0.8	3.3	0.7	0.5	−0.7	0.6	0.5	3.6	1.1	0.8	2.6	4.1	3.8	4.8 *
PRA	Saskatoon	1.6 *	0.9	3.3	0.6	0.3	1.6	0.7	0.6	3.1	0.5	0.3	1.6	4.8 *	4.5 *	5.8 *
PRA	Winnipeg	1.8 *	1.3	1.8	0.9	0.7	1.1	0.7	0.5	3.3	0.9	0.9	1.0	4.9 *	5.2 *	4.2 *
PRA	Yorkton	2.7 *	2.3 *	3.4	1.5	1.3	0.8	1.8 *	1.7 *	6.1 *	1.5	1.2	1.6	6.4 *	6.4 *	6.2 *
SBC	Abbotsford	3.1 *	3.0 *	2.3	3.6 *	3.7 *	1.5	4.6 *	4.6 *	2.6	2.1 *	2.1 *	2.2 *	2.2 *	2.7 *	1.6
PAC	Comox	2.7 *	2.8 *	1.7	3.0 *	2.9 *	5.2 *	4.0 *	4.0 *	1.8 *	1.8 *	2.0 *	1.1	2.3 *	2.3 *	2.6 *
PAC	Port Hardy	1.4 *	1.2 *	1.8	1.7 *	1.7 *	0.0	1.7 *	1.7 *	0.4	0.6	0.4	1.2	1.5	1.4	2.6 *
PAC	Vancouver	2.0 *	1.9 *	1.7	2.1 *	2.0 *	3.7 *	2.9 *	2.9 *	2.7 *	1.3 *	1.3 *	1.3	1.8 *	1.6 *	2.8 *
PAC	Victoria	1.5 *	1.4 *	1.5	1.5 *	1.5 *	3.1	2.2 *	2.2 *	2.7	1.1 *	0.9 *	1.2	1.5 *	1.6 *	1.5
NBC	Watson Lake	3.4 *	2.4 *	5.9	2.9 *	2.8 *	3.4	1.6 *	1.6 *	1.2	2.7 *	1.3	3.3	7.0 *	6.0 *	9.5 *
NBC	Whitehorse	3.3 *	2.1 *	6.0	3.0 *	3.0 *	4.8	2.2 *	2.2 *	5.4	2.5	1.4	3.6	5.7 *	4.7	8.3 *
MCD	Fort Smith	4.5 *	3.7 *	4.6	3.2 *	3.1 *	5.0	3.1 *	3.1 *	2.5	3.4 *	3.5 *	1.2	8.6 *	8.2 *	9.6 *
MCD	Hay River	3.3 *	2.8 *	2.0	2.6 *	2.7 *	−0.3	1.3 *	1.2 *	0.9	2.5	2.1	1.2	7.0 *	6.1 *	8.3 *
MCD	Norman Wells	3.9 *	2.6 *	6.2	3.6 *	3.7 *	1.1	1.7 *	1.6 *	2.2	3.7 *	1.5	5.7	6.2 *	6.0 *	6.8 *
MCD	Yellowknife	3.3 *	2.3 *	3.7	2.7 *	2.4 *	3.7	1.3	1.3	2.2 *	3.3 *	3.1	2.0	6.3 *	5.6 *	7.2 *
ART	Baker Lake	4.2 *	3.2 *	3.8	3.6 *	3.5 *	2.6	1.4 *	1.3 *	1.6	5.9 *	6.0 *	4.4 *	6.0 *	6.1 *	5.9 *
ART	Kuujjuaq	2.1 *	1.3	2.7	1.6	1.3	2.7	2.2 *	2.3 *	0.0	3.7 *	3.6 *	3.2	1.0	1.2	1.5
ARM	Iqaluit	2.6	1.9	3.9	2.4 *	2.3 *	1.9	0.7	0.6	1.3	5.6 *	5.1 *	5.1 *	1.5	0.7	2.9

* Statistically significant trends.

and

Table 5. Temperature Maxima Slopes reported in degrees Celsius per century (°C/c.) “m” represents “slope”. mTT_x—Slope of Total Temperature Maximum, mRT_x—Slope of Radiative Temperature Maximum, and mAT_x—Slope of Advective Temperature Maximum. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Station Name	Annual			Spring			Summer			Fall			Winter
		mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)
ATL	Charlottetown	2.0 *	2.1 *	2.4 *	2.1 *	2.1 *	1.7	2.7 *	2.7 *	3.9 *	2.0 *	1.6	3.2 *	1.5	1.8	2.0 *
ATL	Fredericton	1.5 *	1.2 *	3.4 *	1.4	1.5	2.7	2.0 *	2.0 *	3.6	1.6 *	1.1	3.8 *	1.2	1.1	3.0 *
ATL	Gander	1.8 *	2.0 *	0.6	1.6	1.4	2.1	2.7 *	2.8 *	1.0	2.0 *	2.7 *	0.4	1.2	1.3	1.6
ATL	Greenwood	1.9 *	1.5 *	1.5 *	1.6 *	1.6 *	1.9	2.7 *	2.7 *	1.4	1.7 *	1.5	1.6	1.7 *	1.5	2.5 *
ATL	Moncton	1.9 *	1.6 *	2.3 *	2.0 *	1.6 *	3.2	2.9 *	2.8 *	6.8 *	1.6 *	1.7	1.9	1.4	1.6	1.8
ATL	Saint John	2.3 *	2.2 *	2.7 *	2.2 *	2.1 *	1.9	3.1 *	3.1 *	4.3 *	2.3 *	2.4 *	2.6 *	1.6 *	1.6	2.7 *
ATL	St. John’s	2.1 *	2.2 *	1.0	2.0 *	1.9 *	1.7	3.1 *	3.1 *	1.3	2.1 *	3.0 *	0.0	1.4	1.3	1.9 *
ATL	Yarmouth	1.9 *	2.0 *	1.6 *	1.4 *	1.3 *	1.3	3.1 *	3.1 *	2.5 *	1.8 *	2.1 *	1.7 *	1.4 *	1.4	2.4 *
GRL	Montreal	2.1 *	2.1 *	1.4	1.9 *	1.9 *	−0.6	2.2 *	2.0 *	5.5 *	1.7 *	1.4	2.0	2.8 *	3.1 *	3.2 *
GRL	Ottawa	2.1 *	1.9 *	1.7	1.7	1.7	3.9	2.2 *	2.1 *	3.3 *	1.7 *	1.9	1.4	3.1 *	3.2 *	3.1 *
GRL	Toronto	2.1 *	1.9 *	3.7 *	1.7 *	1.7 *	3.8	1.8 *	1.8 *	−0.3	1.6	1.4	4.1 *	3.4 *	3.5 *	3.2 *
GRL	Trenton	1.7 *	1.3 *	4.2 *	1.5	1.5	1.3	1.5 *	1.5 *	2.3	1.2	0.8	2.6	2.6 *	2.6 *	4.0 *
GRL	Wiarton	1.8 *	1.1	1.9 *	1.8 *	1.6	1.9	1.8 *	1.6 *	3.5	1.2	0.2	2.3	2.6 *	2.7	2.3 *
GRL	Windsor	1.8 *	1.7 *	2.5 *	2.0 *	2.1 *	1.6	1.5 *	1.4 *	2.7	1.2	0.7	3.1 *	2.6	2.8	2.3
NEF	Bagotville	2.0 *	2.0 *	0.8	1.5	1.3	−1.3	3.1 *	3.0 *	3.6 *	1.7 *	2.1 *	1.2	2.0 *	1.9	2.3
NEF	Churchill	4.8 *	4.5 *	2.0	4.2 *	4.1 *	4.9 *	3.4 *	2.7 *	2.3 *	4.4 *	3.2	2.7	4.8 *	5.0 *	4.9 *
NEF	Goose	2.1 *	1.4	2.2	2.0	1.7	6.2 *	2.6 *	2.5 *	2.0	3.0 *	2.9 *	1.9	0.9	0.5	2.3
NEF	Kapuskasing	2.1 *	2.0 *	0.7	2.0	1.9	0.7	2.6 *	2.6 *	1.1	1.5	1.0	1.3	2.5 *	2.1	3.9 *
NEF	Kenora	2.1 *	1.8 *	1.3	2.3 *	1.9	4.0	2.0 *	2.0 *	−0.5	1.0	0.9	1.3	3.4 *	3.3	3.5 *
NEF	Sioux Lookout	2.1 *	1.7	0.2	2.3 *	1.8	3.0	2.1 *	2.1 *	1.3	1.4	1.3	0.3	3.1	3.1	3.0 *
NWF	Cold Lake	2.5 *	1.8 *	3.2 *	1.2	1.2	6.6	2.4 *	2.2 *	−0.3	1.4	0.4	2.3	5.3 *	5.3 *	4.9 *
NWF	Fort McMurray	2.8 *	2.4 *	2.1	2.4 *	2.4 *	−0.9	2.3 *	2.1 *	3.5	1.0	0.9	0.5	5.9 *	5.6 *	7.8 *
NWF	Fort Nelson	2.9 *	2.7 *	4.4 *	2.8 *	2.8 *	4.4	1.7 *	1.7 *	−0.2	1.7	1.5	1.6	6.0 *	5.7 *	7.8 *
NWF	The Pas	2.6 *	1.9 *	2.8 *	2.3 *	2.0	1.9	2.1 *	2.1 *	1.5	1.1	1.1	−0.2	5.3 *	5.0 *	6.1 *
PRA	Calgary	2.4 *	1.9 *	3.1	2.0	2.2	2.1	1.8 *	1.5	−3.6	0.9	0.3	2.2	5.3 *	5.2 *	4.4
PRA	Estevan	0.8	0.7	−0.2	1.4	1.1	2.4	0.1	−0.1	5.9	−0.5	−0.5	−0.9	2.4	2.2	3.4
PRA	Prince Albert	2.1 *	2.0 *	2.4 *	2.0	1.9	7.3	1.2	1.2	4.6	0.5	0.7	0.1	5.2 *	5.3 *	4.4 *
PRA	Regina	1.7	0.8	2.3	2.1	1.8	1.7	0.6	0.4	2.0	0.5	0.4	0.6	3.8	3.0	4.6 *
PRA	Saskatoon	2.1 *	1.5 *	2.4	2.2	2.0	1.9	1.0	0.9	0.2	0.6	0.5	0.8	4.8 *	4.6 *	4.9 *
PRA	Winnipeg	2.2 *	1.9 *	1.2	2.5 *	2.2	1.0	1.7 *	1.5	4.3	0.8	0.7	1.1	4.1 *	4.7 *	3.1
PRA	Yorkton	2.1 *	1.8 *	2.5	2.5	2.4	4.5	1.0	0.9	3.4	0.8	0.5	1.3	4.7 *	4.4 *	5.1 *
SBC	Abbotsford	2.2 *	1.7 *	2.1 *	2.0 *	2.1 *	0.8	3.7 *	3.7 *	0.3	0.9	0.4	1.9	2.2 *	2.2	1.2
PAC	Comox	1.5 *	1.4 *	0.4	1.4	1.2	3.6	2.8 *	2.7 *	4.1 *	0.8	0.7	0.1	1.3	1.3	1.1
PAC	Port Hardy	1.5 *	1.3 *	1.5 *	1.5	1.6	0.7	2.1 *	2.1 *	0.2	0.8	0.6	0.9	1.9 *	1.7 *	2.2 *
PAC	Vancouver	1.4 *	1.2 *	1.1	1.1 *	1.0 *	3.3	2.3 *	2.3 *	1.3	0.7	0.5	0.9	1.6 *	1.5	1.9
PAC	Victoria	1.7 *	1.5 *	1.5	1.8 *	1.8 *	3.5	2.7 *	2.7 *	2.0	0.8	0.6	1.5	1.7 *	1.5 *	1.4
NBC	Watson Lake	2.3 *	1.4	4.0 *	2.0 *	2.1 *	−2.7	0.7	0.7	3.7	1.3	−0.1	1.4	5.6 *	5.0 *	7.4 *
NBC	Whitehorse	2.6 *	1.5	4.5 *	3.0 *	2.9 *	5.1	1.2	1.2	2.1	1.5	0.7	2.0	5.1 *	4.0	7.1 *
MCD	Fort Smith	3.1 *	2.4 *	2.7 *	2.8 *	2.7 *	4.1	2.1 *	2.0 *	2.2	1.7	1.7	−0.3	6.3 *	6.2 *	7.2 *
MCD	Hay River	3.0 *	2.8 *	0.9	3.1 *	2.8 *	0.2	2.5 *	2.3 *	1.0	1.6	1.2	0.2	5.5 *	5.4 *	6.4 *
MCD	Norman Wells	3.9 *	2.7 *	7.0 *	3.7 *	3.7 *	4.9	1.8 *	1.7 *	4.6 *	4.6 *	2.3	6.4 *	6.5 *	6.2 *	7.4 *
MCD	Yellowknife	3.3 *	2.5 *	3.3 *	3.2 *	2.9 *	5.2	1.7 *	1.6 *	4.4 *	2.8 *	3.0	1.4	6.2 *	5.8 *	7.1 *
ART	Baker Lake	4.7 *	4.0 *	4.1 *	3.5 *	3.5 *	3.4	3.6 *	3.6 *	1.4	6.0 *	6.6 *	4.2 *	6.3 *	6.5 *	6.1 *
ART	Kuujjuaq	3.1 *	2.3 *	3.3 *	3.1 *	2.7 *	5.3 *	3.2 *	3.3 *	0.8	4.3 *	4.7 *	3.1	1.7	1.7	2.3
ARM	Iqaluit	1.8 *	1.3	3.6 *	1.0	1.0	0.9	0.8	0.7	0.4	5.3 *	5.0 *	5.4 *	0.8	0.3	2.4

* Statistically significant trends.

show slopes of the total, radiative, and advective temperature trends. Section 3.4 summarizes regional counts of radiative and advective annual and seasonal populations (

Table 6. Regional radiative population counts, radiative population participation, and radiative population slope of counts reported per century (#/c.) “m” represents “slope”. RPC—Radiative Population Count, RPP—Radiative Population Participation, and mRP_c—Slope of Radiative Population Count. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Annual			Spring			Summer			Fall			Winter
	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)	RPC (#)	RPP (%)	mRPC (#/c.)
ATL	20,145	82	9	5089	81	1	5279	84	1	4212	68	2	3811	63	4
GRL	21,199	84	5	5887	93	−1	6143	97	1	4894	78	2	4274	69	3
NEF	20,608	82	21	5856	92	4	5994	94	4	4416	70	8	4341	70	6
NWF	21,725	87	13	6059	96	1	6151	98	2	4880	78	5	4635	75	6
PRA	21,967	87	10	6061	96	2	6238	98	1	5138	82	1	4530	73	6
SBC	22,778	90.4	22	6194	97.7	1	6287	98.9	0	5254	83.5	6	5043	81.3	15
PAC	22,459	89	17	6164	97	1	6216	98	2	5092	81	6	4988	80	8
NBC	20,986	83	15	6251	99	1	6273	99	0	4306	68	8	4157	67	7
MCD	19,577	79	17	5883	94	3	6001	96	1	3932	63	8	3761	61	4
ART	18,685	77	17	5547	91	2	5833	95	1	3739	61	7	3566	59	8
ARM	19,337	76.8	9	5806	91.6	−1	6004	94.4	0	3860	61.4	5	3667	59.1	5

and

Table 7. Regional advective population counts, advective population participation, and advective population slope of counts reported per century (#/c.) “m” represents “slope”. APC—Advective Population Count, APP—Advective Population Participation, and mAP_c—Slope of Advective Population Count. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Annual			Spring			Summer			Fall			Winter
	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)	APC (#)	APP (%)	mAPC (#/c.)
ATL	4411	18	−9	495	8	−1	283	5	−1	1628	27	−2	2004	33	−4
GRL	3992	16	−5	455	7	1	207	3	−1	1402	22	−2	1928	31	−3
NEF	4629	18	−21	502	8	−4	372	6	−4	1887	30	−8	1868	30	−6
NWF	3283	13	−13	242	4	−1	154	2	−2	1374	22	−5	1514	25	−6
PRA	3223	13	−10	280	4	−2	112	2	−1	1161	18	−1	1670	27	−6
SBC	2412	9.6	−22	146	2.3	−1	69	1.1	0	1036	16.5	−6	1161	18.7	−15
PAC	2732	11	−17	175	3	−1	140	2	−2	1202	19	−6	1215	20	−8
NBC	4206	17	−15	93	1	−1	81	1	0	1992	32	−8	2040	33	−7
MCD	5343	21	−17	391	6	−3	279	4	−1	2307	37	−8	2368	39	−4
ART	5558	23	−21	606	10	−3	287	5	−2	2293	39	−8	2372	40	−9
ARM	5854	23.2	−9	529	8.4	1	353	5.6	0	2431	38.6	−5	2541	40.9	−5

) while Section 3.5 summarizes regional changes in extrema temperature trends of the total, radiative, and advective temperature populations (

Table 8. Regional temperature minima slopes reported in degrees Celsius per century (°C/c.) “m” represents “slope”. mTT_n—Slope of Total Temperature Maximum, mRT_n—Slope of Radiative Temperature Maximum, and mAT_n—Slope of Advective Temperature Maximum. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Annual			Spring			Summer			Fall			Winter
	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)	mTTn (°C/c.)	mRTn (°C/c.)	mATn (°C/c.)
ATL	1.6	1.5	1.6	1.2	1.1	2.2	2.5	2.5	2.8	1.5	1.4	1.7	1.3	1.2	1.7
GRL	2.5	2.3	2.9	2.2	2.1	2.8	2.8	2.8	3.3	1.9	1.6	2.7	3.2	3.1	3.3
NEF	2.7	2.4	1.9	2.0	1.9	2.3	2.6	2.6	2.2	2.7	2.3	2.1	3.6	3.4	4.5
NWF	3.2	2.7	4.0	2.1	2.1	4.0	2.2	2.1	2.9	2.3	2.0	2.0	6.6	6.6	7.3
PRA	2.1	1.6	2.8	1.2	1.0	1.6	1.2	1.1	3.6	1.2	0.9	1.9	4.9	4.8	5.0
SBC	3.1	3	2.3	3.6	3.7	1.5	4.6	4.6	2.6	2.1	2.1	2.2	2.2	2.7	1.6
PAC	1.9	1.8	1.7	2.1	2.0	3.0	2.7	2.7	1.9	1.2	1.2	1.2	1.8	1.7	2.4
NBC	3.4	2.3	6.0	3.0	2.9	4.1	1.9	1.9	3.3	2.6	1.4	3.5	6.4	5.4	8.9
MCD	3.8	2.9	4.1	3.0	3.0	2.4	1.9	1.8	2.0	3.2	2.6	2.5	7.0	6.5	8.0
ART	3.2	2.3	3.3	2.6	2.4	2.7	1.8	1.8	0.8	4.8	4.8	3.8	3.5	3.7	3.7
ARM	2.6	1.9	3.9	2.4	2.3	1.9	0.7	0.6	1.3	5.6	5.1	5.1	1.5	0.7	2.9

and

Table 9. Regional temperature maxima slopes reported in degrees Celsius per century (°C/c.) “m” represents “slope”. mTT_x—Slope of Total Temperature Maximum, mRT_x—Slope of Radiative Temperature Maximum, and mAT_x—Slope of Advective Temperature Maximum. “CR” represents “climate region”. ATL—Atlantic Canada, GRL—Great Lakes/St. Lawrence Lowlands, NEF—Northeastern Forest, NWF—Northwestern Forest, PRA—Prairies, SBC—South British Columbia Mountains, PAC—Pacific Coast, NBC—North British Columbia Mountains/Yukon Territory, MCD—Mackenzie District, ART—Arctic Tundra, and ARM—Arctic Mountains and Fiords.

CR	Annual			Spring			Summer			Fall			Winter
	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)	mTTx (°C/c.)	mRTx (°C/c.)	mATx (°C/c.)
ATL	1.9	1.9	1.9	1.8	1.7	2.1	2.8	2.8	3.1	1.9	2.0	1.9	1.4	1.5	2.2
GRL	1.9	1.7	2.6	1.8	1.8	2.0	1.8	1.7	2.8	1.4	1.1	2.6	2.9	3.0	3.0
NEF	2.5	2.2	1.2	2.4	2.1	2.9	2.6	2.5	1.6	2.2	1.9	1.5	2.8	2.7	3.3
NWF	2.7	2.2	3.1	2.2	2.1	3.0	2.1	2.0	1.1	1.3	1.0	1.1	5.6	5.4	6.7
PRA	1.9	1.5	2.0	2.1	1.9	3.0	1.1	0.9	2.4	0.5	0.4	0.7	4.3	4.2	4.3
SBC	2.2	1.7	2.1	2.0	2.1	0.8	3.7	3.7	0.3	0.9	0.4	1.9	2.2	2.2	1.2
PAC	1.5	1.4	1.1	1.5	1.4	2.8	2.5	2.5	1.9	0.8	0.6	0.9	1.6	1.5	1.7
NBC	2.5	1.5	4.3	2.5	2.5	1.2	1.0	1.0	2.9	1.4	0.3	1.7	5.4	4.5	7.3
MCD	3.3	2.6	3.5	3.2	3.0	3.6	2.0	1.9	3.1	2.7	2.1	1.9	6.1	5.9	7.0
ART	3.9	3.2	3.7	3.3	3.1	4.4	3.4	3.5	1.1	5.2	5.7	3.7	4.0	4.1	4.2
ARM	1.8	1.3	3.6	1.0	1.0	0.9	0.8	0.7	0.4	5.3	5	5.4	0.8	0.3	2.4

).

3.1. Seasonal Radiative and Advective Day Count Averages

Seasonal counts of radiative and advective air temperature populations indicate the existence of two distinct climatological periods, Spring–Summer (SS) extending between the Vernal and Autumn Equinox, and Fall–Winter (FW) extending between the Autumn and Vernal Equinox. The SS period is characterized by a high count of radiative days (~10,000–12,000) and a small number of advective days (~150–1000), while the FW period exhibits much higher counts of advective days (~2000–5000) and proportionally smaller counts of radiative days (~7500–10,500).

A systematic increase and large variability in counts of the radiative population are observed during the FW period along with the simultaneous decrease in advective counts at the majority of stations. During the SS period, radiative and advective counts maintain their ratios and low seasonal variability.

3.2. Time Evolution of Seasonally Averaged Trends of Radiative and Advective Day Counts

Table 2 lists radiative population counts (RPC), radiative population participation (RPP) and population rates of change denoted as slopes (m) of radiative population counts (RP_c) reported in counts per century (#/c.). All radiative population count changes refer to a number of added radiative days at the expense of diminishing advective days from the total temperature population. Table 3 is a mirrored image of Table 2 values presented separately for evaluation of advective population counts, overall participation, and time evolution of trends in advective day counts. The values in Table 2, Table 3, Table 4 and Table 5 with an asterisk indicate statistically significant slopes of temperature populations assessed using the Mann–Kendall (MK) test for the identification of monotonic upward and downward trends.

Seasonal values of the RPC rates range between −1 and 22 counts per century (/c.) While an RPC range between 7 and 9/c. is considered substantial during the FW seasons, the RPC value of 3/c. during the SS season is considered elevated.

3.2.1. Atlantic Canada (ATL)

The rates of change in radiative and advective populations of the ATL region rank second to the lowest in Canada with an annual average of 9/c. The RPC rate of change is highest in the winter while other seasonal averages are low (Table 2). Low rates of the APC are observed at Saint John during fall and at Fredericton, during the spring (2/c.) The highest overall rate of change is observed at Greenwood and Moncton stations due to intense winter changes in radiative counts. The absence of any seasonal rate of change in RPC and APC is observed at Charlottetown (0/c.). Statistically significant rates of change in annual RPC are observed at Greenwood and Moncton as well as in seasonal RPC at Gander (4/c.) during spring.

3.2.2. Great Lakes/St. Lawrence Lowlands (GRL)

The rates of change in radiative temperature population are lowest in Canada in the GRL region (5/c.). Although generally low, the highest statistically significant annual rate in RPC among the GRL group is observed at Wiarton (19/c.) (Table 2 and Figure 4a). The RPC rates in summer (3/c.) and winter (9/c.) also display statistical significance. Since the increase in the RPC occurs at the expense of the APC (Table 3) the highest significant rate of change in the advective temperature population is observed at Wiarton (−19/c.).

3.2.3. Northeastern Forest (NEF)

The highest statistically significant annual RPC rates in Canada are observed in the NEF climate region (21/c.) identified at Churchill (16/c.), Goose (12/c.), and Kenora (8/c.). The NEF region is also characterized by the highest summer RPC average (8.3/c.) due to the highest RPC rate observed at Churchill (13/c.) (Table 2). The RPC averages of the NEF stations (Figure 4b and Figure 5a) during the fall season range from anomalously high to high. The NEF stations are also characterized by large winter RPC counts that are statistically non-significant.

3.2.4. Northwestern Forest (NWF)

The NWF region is characterized by high statistically significant RPC annual rates. The highest overall rate of change is observed at The Pas (17/c.) followed by Cold Lake (16/c.) and Fort Mc Murray (14/c.). High positive RPC and negative APC rates at Cold Lake, and The Pas during the fall season as well as moderate summer rates at Cold Lake and McMurray are supported by statistical significance.

3.2.5. Prairies (PRA)

The PRA climate region is characterized by high annual statistically significant rates at Calgary (16/c.), Regina (14/c.), and Winnipeg (11/c.). The seasonal features of radiative and advective population counts of the PRA stations during the SS period are moderate to high spring RPC rates statistically significant only at Regina, and statistically significant moderate summer rates observed at Calgary, Estevan, and Regina. The FW period is characterized by the non-significant low RPC rates during the fall season, and high winter RPC rates with statistical significance observed at Calgary (11/c.) (Figure 5b).

3.2.6. South British Columbia Mountains (SBC)

The SBC climate region is represented in this study with one station. The majority of Abbotsford’s substantial RPC (22/c.) is due to the highest rates of change observed during the winter (15/c.) and, to a lesser degree, fall (6/c.) seasons (Figure 6a). The APC decline rate is likewise among the highest statistically significant rates of change observed across the studied data sets.

3.2.7. Pacific Coast (PAC)

Members of the PAC climate group exhibit very high statistically significant RPC and APC rates of change at all stations. The highest annual RPC rates are observed at Port Hardy (19/c.) (Figure 6b), followed by Comox (18/c.), Victoria (17/c.), and Vancouver (14/c.) stations. Statistically significant positive RPC and negative APC rates are observed at Comox during spring, at Comox and Victoria during summer, at all stations except Victoria during the fall season, and at Port Hardy and Victoria during winter.

3.2.8. North British Columbia Mountains/Yukon Territory (NBC)

The NBC climate region is presented in this study by two stations with high RPC rates of change. Watson Lake is characterized by a high significant fall RPC rate (10/c.) while Whitehorse exhibits a high significant winter RPC rate (11/c.). The NBC members are characterized by the absence of summer changes (0/c.) or the significance of changes in the RTP and ATP rates during the spring season.

3.2.9. Mackenzie District (MCD)

The MCD group exhibits the second-highest statistically significant annual rates of change in the RPC and the ATC originating from large changes introduced during the fall rather than the winter season. High statistically significant RPC rate at Hay River (6/c.) (Figure 7a) during the spring and summer season and at Yellowknife (5/c.) during spring contribute to the overall magnitude of the RPC and APC change in the MCD region.

3.2.10. Arctic Tundra (ART)

The ART region is represented by two high latitude stations, Baker Lake (64.3° N) and Kuujjuaq (58.1° N) (Figure 7b) both characterized by high, statistically significant RPC rates (20/c. and 22/c.). Substantial changes in the RPC and APC rates in the ART region result from large, statistically significant fall rates in addition to a high winter (11/c.) and spring rate (4/c.) at Kuujjuaq.

3.2.11. Arctic Mountains and Fiords (ARM)

A single high latitude representative of the ARM climate region, the Iqaluit station (63.7° N) is characterized by statistically non-significant mid-range winter and fall RPC rates (5/c.), a low spring APC rate (1/c.), and the absence of any RPC or APC changes during the summer season.

3.3. Seasonal Biases and Trends of Total, Radiative, and Advective Temperature Populations

This section discusses seasonal bias between homogeneous temperature populations and the time evolution of their seasonal temperature trends. Table 4 and Table 5 present annual and seasonal slopes of total, radiative and advective minima and maxima temperature trends. Annually and seasonally averaged advective minima and maxima are substantially cooler than the radiative and total temperature populations. Figure 8, Figure 9, Figure 10, Figure 11, Figure 12 and Figure 13 present total, radiative and advective minima, and maxima air temperature populations at Saint John, Toronto, Churchill, Port Hardy, Norman Wells, and Baker Lake. The top graphs present the total temperature population of minima (TT_n) (green), radiative temperature minima (TR_n) (blue), and advective temperature minima (TA_n) (pink). The lower graphs display the total temperature population of maxima (TT_x) (brown), radiative temperature maxima (TR_x) (orange), and advective temperature maxima (TA_x) (purple).

The most apparent observation in Figure 8, Figure 9, Figure 10, Figure 11, Figure 12 and Figure 13 is the separation in the magnitude of radiative and advective maxima temperatures during the spring, summer, and fall. The total temperature maxima are, except for the fall season, mainly found in the proximity of radiative maxima. Radiative maxima consistently display a warm bias against maxima populations of the total and advective population except in certain cases during the winter season (Figure 8b and Figure 13b) when radiative and advective maxima, as well as minima, exhibit similar temperature magnitudes.

The variability of advective minima is visibly larger than that of other temperature populations during spring, summer, and fall. Advective minima bias is apparent in these three seasons in Figure 9, Figure 10, Figure 12 and Figure 13. The exceptions are summer minima at Saint John in Atlantic Canada where the advective warm bias is apparent in Figure 8a, and spring, summer, and fall minima at Port Hardy on the Pacific Coast exemplifying the range of advective minima peculiarities affected by the local climate (Figure 11a).

Maxima of the advective population display obvious cold bias during the spring, summer, and fall seasons. Advective maxima bias individually varies but overall seems more prominent and persistent than the advective minima bias. The winter advective bias however indicates a different thermal regime in the minima population at the majority of stations. While the maxima bias is consistently moderately negative when compared to the total population, the advective minima bias is either already positive or switches from negative to positive at the midpoint of the data set time scale corresponding to the 1990s.

Statistically significant upward trends can be observed in annually-averaged minima at all stations except for Saint John, Wiarton, Goose, Estevan, and Iqaluit (Table 4). The significance of temperature warming rates of the annual radiative and the majority of the advective population is generally consistent with the total sample, particularly during summer and winter. The exceptions are particular regions such as the Prairies (PRA) in summer and Atlantic Canada (ATL) region in winter. The statistical significance of spring maxima is more sporadic during the spring and in particular during the fall seasons.

Statistically significant upward trends can be observed in annually-averaged maxima at all stations except for Estevan and Regina (Table 5). The significance of temperature warming rates of the annual radiative and the majority of the advective population is the most consistent with summer and winter populations. The loss of statistical significance is most apparent during the fall season for all maxima populations while during spring it affects most of the advective temperature maxima.

The largest statistically significant warming trends in seasonal minima are observed in winter advective populations of the Mackenzie District (9.6 °C), North British Columbia Mountains/Yukon Territory (9.5 °C), and Northwestern Forest (8.8 °C).

3.4. Regional Summaries of Changes in Population Counts

The Canadian climate region with the highest radiative population participation (RPP) annually is the South British Columbia Mountains/Yukon Territory (90.4%) (Table 6). The radiative population count (RPC) of this region also exhibits the largest upward trend (22/c.) and inversely the lowest advective population count (APC) rate (Table 7). The regional spring and summer RPCs, as well as fall and winter RPCs, are similar and as such support the grouping into two, Spring–Summer (SS) and Fall–Winter (FW) seasons. The smallest regional annual RPP is observed in Arctic Tundra (77%) with a substantial RPC rate of 17/c., typical of northwest Canada. The highest seasonal RPC rates among the studied stations are observed in the South British Columbia Mountains/Yukon Territory during winter while the smallest seasonal RPC rates are a characteristic of spring and summer seasons across the stations.

3.5. Regional Summaries of Changes in Extrema Temperature Trends

Analysis of regional total, radiative, and advective daily temperature extrema trends reveal an overall average increase in minima of 2.7 °C in total air temperature, 2.2 °C in radiative, and 3.1 °C in advective temperature population, as well as an average increase in maxima of 2.4 °C in total, 1.9 °C in radiative, and 2.6 °C in the advective population (Table 8 and Table 9). The smallest magnitude of changes in minima trends per century was observed in spring radiative temperature populations of the Prairies and Atlantic Canada regions. On the contrary, the largest overall changes in daily minima trends are identified during the winter season averaging 3.8 °C in total, 3.6 °C in radiative, and 4.5 °C in the advective temperature population. The highest observed minima trends among climate regions are displayed by Mackenzie District, Northwestern Forest, and North British Columbia Mountains/Yukon Territory stations (Table 8).

Averages of daily maxima trends exhibit a slightly smaller seasonal increase than the minima. Winter averages of the total, radiative and advective maxima at the Mackenzie District, and North British Columbia Mountains/Yukon Territory present the largest seen seasonal warming rates (Table 9).

4. Discussion

In this work we analyzed forty-five Canadian temperature time series, spanning 69 years in length and encompassing a range of 23° in latitudes and 82° in longitudes. The previous study [3] established the main criterion for the characterization of radiative and advective days using the diurnal temperature pattern concept and introduced the method for the delineation of temperature populations.

This study examined changes in two aspects of seasonal temperature populations: the change in the number of radiative and advective days, and the change in individual temperature trends. Using the derived mathematical extrema [24] and following examples of similar studies [25,26,27,28], we explored radiative and advective thermal regimes.

Warming temperature trends were observed in all annually-averaged maxima of the total populations with only two stations in the Prairies region, Estevan, and Regina not displaying statistical significance. Upward trends of the radiative population generally displayed consistency with the total population in their statistical significance.

Seasonal maxima warming rates were observed at all stations with the exception of Estevan during the spring, summer, and fall seasons. Spring and fall warming rates showed similarities in the absence of statistical significance in their temperature trends. On the other hand, the majority of summer and winter maxima rates of total and radiative air temperature populations displayed statistical significance.

Advective maxima rates differ in statistical significance between the seasons. The majority of winter advective maxima exhibit statistical significance, including some anomalously high upward trends in northwestern Canada.

Increasing trends of annually-averaged minima are present at the majority of stations with forty out of forty-five being statistically significant. Similar to maxima, the radiative minima closely follow the magnitude and the statistical significance of trends in the total temperature population. Approximately two-thirds of advective winter minima display statistical significance with the apparent exception of Atlantic Canada, Arctic Mountains, and the Fiords regions.

Summer minima warming trends are moderate with the majority of extrema time series displaying statistical significance (86.7%) (Table 4). Winter minima trends exhibit statistical significance at 75% of stations. However, the statistical significance of spring and fall radiative and advective minima amount to 64% and 20%, respectively.

Analysis of seasonal radiative and advective counts supports the concept of Spring–Summer and Fall–Winter climatological seasons. The steady increase in radiative days at the expense of advective days reveals an already distorted balance between these two temperature populations.

Large observed radiative and advective warming trends provide strong evidence of pan-Canadian warming, particularly pronounced in the northwest region. Based on the results of this study and the analysis in [5] we speculate that the population of advective days acts as a climate moderator in the midlatitudes.

Radiative and advective thermal regimes seem to be influenced by large-scale low-frequency variability modes affecting the Canadian climate [29,30]. The weakening of the advective cooling effect of the total temperature population appears to be related to the declining frequency of dry polar air [31].

We suggest that the increase in the overall temperature magnitude and decrease in cooling advective counts translates into the loss of the moderating capacity in atmospheric thermal exchanges between major temperature populations.

The following future work recommendations present research challenges that would contribute to the understanding of the aspects of radiative and advective thermal regimes. Event-based analysis of advective heating and cooling episodes could potentially reveal additional hidden patterns of temperature variability. On the other hand, the analysis of sub-daily variations in the advective temperature regime could aid the identification of potential physical drivers operating on a smaller time scale. Urban heat island (UHI) study of radiative and advective extrema is also suggested for gaining insights into the specific UHI contributions to daily temperature variability. Finally, the correlation of changes in advective temperature extrema with changes in the population of air masses [31] is needed to examine the link between the recent Arctic amplification and rapid changes in the advective regime at sub-Arctic latitudes. In the light of significant warming trends of radiative temperature and loss of moderating ability of advective temperature, exploring the evolution of diurnal extrema timing presents the key aspect of future research that would provide the vital information necessary for the addition of the forecasting features to the LPD algorithm [32].

5. Conclusions

This study presents significant indicators of Canadian temperature changes derived from the features of two homogeneous air temperature populations: the change in the number of radiative and advective days, and the change in their temperature trends.

Seasonal radiative and advective count analysis demonstrates the existence of two predominant thermal regimes: a stable Spring–Summer period, dominated by a radiative day count, and the unstable Fall–Winter period characterized by a sizeable and a reducing advective temperature population.

Seasonal temperature analysis reveals the contrast between radiative and advective temperature regimes. The analysis of radiative and advective trends provides quantitative evidence of the magnitude of changes in these individual temperature populations. The high incidence of large and statistically significant summer minima and maxima trends in a predominantly radiative population suggests an increase in atmospheric ability to retain heat. Anomalously large, statistically significant winter warming trends observed in all temperature populations of the Canadian northwest provide evidence for the weakening of the advective temperature population’s “cooling effect” on the magnitude of the total temperature.

The significance of this work lies in the sufficiency of the presented method in the delineation of the total temperature sample for analysis of radiative and advective thermal regimes based on air temperature records alone.