Figure 1.
Location of the 22 large lakes included in this study. Lake abbreviations are explained in
Table 1.
Figure 1.
Location of the 22 large lakes included in this study. Lake abbreviations are explained in
Table 1.
Figure 2.
The methodological workflow of this study. All abbreviations are explained in
Section 3.
Figure 2.
The methodological workflow of this study. All abbreviations are explained in
Section 3.
Figure 3.
Variations in Tb for different polarizations and orbits, air temperature, ice thickness [
83] in a hydrological year (2014/2015) in Qinghai Lake. Tb is shown with the acronym H and V, which represent horizontal and vertical polarization, while A and D represent ascending and descending orbits. Air temperature is depicted as the daily average air temperature (TAVG) of the nearby meteorological station GANGCHA. Only the monthly average values of ice thickness in the first three months of the year (January, February, March) are available. The lake ice phenology parameters are denoted in black vertical lines. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 3.
Variations in Tb for different polarizations and orbits, air temperature, ice thickness [
83] in a hydrological year (2014/2015) in Qinghai Lake. Tb is shown with the acronym H and V, which represent horizontal and vertical polarization, while A and D represent ascending and descending orbits. Air temperature is depicted as the daily average air temperature (TAVG) of the nearby meteorological station GANGCHA. Only the monthly average values of ice thickness in the first three months of the year (January, February, March) are available. The lake ice phenology parameters are denoted in black vertical lines. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 4.
Interannual variations in mean lake ice phenology of 22 lakes from 1979 to 2018. (A) FUS means freeze-up start date; (B) FUE means freeze-up end date; (C) BUS means break-up start date; (D) BUE means break-up end date; (E) ID means ice duration, which is the number of days between FUS and BUE; (F) CID means complete ice duration, which is the number of days between FUE and BUS. The unit of (A–D) is the date of a month; (E,F) is days. The standard deviation is shown in the grey shadowed area.
Figure 4.
Interannual variations in mean lake ice phenology of 22 lakes from 1979 to 2018. (A) FUS means freeze-up start date; (B) FUE means freeze-up end date; (C) BUS means break-up start date; (D) BUE means break-up end date; (E) ID means ice duration, which is the number of days between FUS and BUE; (F) CID means complete ice duration, which is the number of days between FUE and BUS. The unit of (A–D) is the date of a month; (E,F) is days. The standard deviation is shown in the grey shadowed area.
Figure 5.
Annual change rate of lake ice phenology of 22 large lakes during the period 1979–2018. Each lake ice phenology (LIP) parameter is described in one color. Pink, blue, green, yellow, orange, and red denote the annual change rate of FUS, FUE, BUS, BUE, ID, and CID, respectively. The LIP parameters that pass the significance test (p < 0.05) are shown with a slash pattern. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 5.
Annual change rate of lake ice phenology of 22 large lakes during the period 1979–2018. Each lake ice phenology (LIP) parameter is described in one color. Pink, blue, green, yellow, orange, and red denote the annual change rate of FUS, FUE, BUS, BUE, ID, and CID, respectively. The LIP parameters that pass the significance test (p < 0.05) are shown with a slash pattern. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 6.
Variation in lake ice phenology of Lake Baikal, 1979–2018. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 6.
Variation in lake ice phenology of Lake Baikal, 1979–2018. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 7.
Spatial distribution of Tb retrieval points and adjacent weather stations of Lake Baikal. Eighteen points were selected to quantify the spatio-temporal variability of lake ice phenology. The grey points were unused because of land interference.
Figure 7.
Spatial distribution of Tb retrieval points and adjacent weather stations of Lake Baikal. Eighteen points were selected to quantify the spatio-temporal variability of lake ice phenology. The grey points were unused because of land interference.
Figure 8.
Spatial variation of lake ice phenology on Lake Baikal based on 18 retrieved Tb points. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 8.
Spatial variation of lake ice phenology on Lake Baikal based on 18 retrieved Tb points. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 9.
R2 heatmap of the lake ice phenology regression analysis results of driving factors, including five geo-based factors and four factors related to air temperature, including freezing degree days (FDD). The asterisk indicates that the parameter passes the significance in the F-test. * p < 0.05, ** p < 0.01, *** p < 0.001. Ice phenology parameters and climate factors are shown with the abbreviations. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration. TAVG, annual average air temperature; TMAX, annual maximum air temperature; TMIN, annual minimum air temperature; FDD, freezing degree days; PRCP, annual average precipitation.
Figure 9.
R2 heatmap of the lake ice phenology regression analysis results of driving factors, including five geo-based factors and four factors related to air temperature, including freezing degree days (FDD). The asterisk indicates that the parameter passes the significance in the F-test. * p < 0.05, ** p < 0.01, *** p < 0.001. Ice phenology parameters and climate factors are shown with the abbreviations. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration. TAVG, annual average air temperature; TMAX, annual maximum air temperature; TMIN, annual minimum air temperature; FDD, freezing degree days; PRCP, annual average precipitation.
Figure 10.
Interannual variations of lake ice phenology of Lake Baikal from 1979 to 2100. The black line (History) represents the lake ice phenology data retrieved from Tb data of SMMR, SSM/I, and SSMIS (1979–2018), the red line (His-Fit) represents the regression fitting line of lake ice phenology and monthly maximum temperature from CMIP5 historical data (1979–2018). Lines in cyan, rose, green, and blue represent the predicted lake ice phenology values of RCP 2.6, 4.5, 6.0, and 8.5 in 2019–2100, respectively; the solid line represents the mean value predicted by six models, while the shaded range represents the range between maximum and minimum predicted lake ice phenology values by six models for each year. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 10.
Interannual variations of lake ice phenology of Lake Baikal from 1979 to 2100. The black line (History) represents the lake ice phenology data retrieved from Tb data of SMMR, SSM/I, and SSMIS (1979–2018), the red line (His-Fit) represents the regression fitting line of lake ice phenology and monthly maximum temperature from CMIP5 historical data (1979–2018). Lines in cyan, rose, green, and blue represent the predicted lake ice phenology values of RCP 2.6, 4.5, 6.0, and 8.5 in 2019–2100, respectively; the solid line represents the mean value predicted by six models, while the shaded range represents the range between maximum and minimum predicted lake ice phenology values by six models for each year. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date; ID, ice duration; CID, complete ice duration.
Figure 11.
Spatial distribution of Tb retrieval points and adjacent weather stations of three well-known lakes: Qinghai Lake, Lake Winnipeg, and Great Slave Lake. Red dots denote Tb retrieval points; black dots denote the adjacent lake ice observation site. The coordinate system of each lake is WGS-84.
Figure 11.
Spatial distribution of Tb retrieval points and adjacent weather stations of three well-known lakes: Qinghai Lake, Lake Winnipeg, and Great Slave Lake. Red dots denote Tb retrieval points; black dots denote the adjacent lake ice observation site. The coordinate system of each lake is WGS-84.
Figure 12.
MODIS images (MOD09GA) of lake ice freeze-up and break-up of Qinghai Lake in 2015/2016. Red dots in the first image of each figure denote the coordinates of Tb retrieving points of each lake. A 6-2-1 band combination is shown in RGB view. The abbreviations are as follows: FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date. “MW” denotes that this image was from microwave remote sensing in this study; “MODIS” means that the result was obtained from the MODIS surface reflectance product.
Figure 12.
MODIS images (MOD09GA) of lake ice freeze-up and break-up of Qinghai Lake in 2015/2016. Red dots in the first image of each figure denote the coordinates of Tb retrieving points of each lake. A 6-2-1 band combination is shown in RGB view. The abbreviations are as follows: FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date. “MW” denotes that this image was from microwave remote sensing in this study; “MODIS” means that the result was obtained from the MODIS surface reflectance product.
Table 1.
Specifications of the lakes selected in this study. The latitude and longitude are the coordinates of the Tb-retrieving point of each lake.
Table 1.
Specifications of the lakes selected in this study. The latitude and longitude are the coordinates of the Tb-retrieving point of each lake.
No. | Lake Name | Abbreviation | Country | Latitude | Longitude | Area (km2) | Altitude (m.a.s.l.) | Adjacent Weather Station ID |
---|
1 | Baikal | BK | Russia | 54.321° N | 109.006° E | 31,924.6 | 456 | RSM00030636 |
2 | Great Bear | GB | Canada | 66.614° N | 120.829° W | 30,530.1 | 186 | CA002300902 |
3 | Great Slave | GS | Canada | 62.151° N | 114.561° W | 27,816.3 | 156 | CA002202400 |
4 | Winnipeg | WI | Canada | 50.733° N | 96.710° W | 23,809.3 | 217 | CA005022791 |
5 | Balkhash | BA | Kazakhstan | 46.376° N | 74.600° E | 17,458.8 | 341 | KZ000035796 |
6 | Onega | ON | Russia | 61.582° N | 35.668° E | 9608.1 | 35 | RSM00022831 |
7 | Athabasca | AT | Canada | 59.254° N | 109.432° W | 7781.6 | 213 | CA004063755 |
8 | Khanka | KK | China and Russia | 45.007° N | 132.416° E | 4088.1 | 69 | RSM00031921 |
9 | Qinghai | QH | China | 36.921° N | 100.143° E | 4449.7 | 3196 | CHM00052754 |
10 | Khuvsgul | KH | Mongolia | 51.108° N | 100.516° E | 2741.4 | 1645 | MGM00044207 |
11 | Uvs | UV | Mongolia | 50.302° N | 92.711°E | 3421.5 | 759 | MG000044212 |
12 | Melville | ME | Canada | 53.678° N | 59.632° W | 3069.0 | −1 | CA008501900 |
13 | Rybinksk | RY | Russia | 58.414°N | 38.491° E | 3926.6 | 102 | RSM00027037 |
14 | Alakol | AL | Kazakhstan | 46.117° N | 81.746° E | 2802.1 | 347 | KZ000036729 |
15 | Nam Co | NM | China | 30.666° N | 90.527° E | 1933.6 | 4718 | CHM00055279 |
16 | Selin Co | SL | China | 31.739° N | 89.114° E | 1640.9 | 4530 | CHM00055279 |
17 | Nettilling | NE | Canada | 66.582° N | 70.852° W | 5064.7 | 30 | CA002401030 |
18 | Amadjuak | AM | Canada | 64.898° N | 71.217° W | 3033.7 | 113 | CA002403049 |
19 | Dubawnt | DU | Canada | 63.113° N | 101.540° W | 3628.5 | 236 | CA002300500 |
20 | Wollaston | WO | Canada | 58.233° N | 103.304° W | 2272.0 | 398 | CA004063755 |
21 | Michikamau | MI | Canada | 54.043° N | 63.974° W | 5610.4 | 460 | CA007117827 |
22 | Teshekpuk | TE | U.S.A. | 70.605° N | 153.632° W | 834.9 | 2 | CA002300902 |
Table 2.
Coupled Model Intercomparison Project (CMIP5) models used in this study and their spatial coverage and availability of Representative Concentration Pathways in each model.
Table 2.
Coupled Model Intercomparison Project (CMIP5) models used in this study and their spatial coverage and availability of Representative Concentration Pathways in each model.
Model | Institute | Nation | Spatial Coverage (°) | Representative Concentration Pathways (RCPs) |
---|
Lon. | Lat. | 2.6 | 4.5 | 6 | 8.5 |
---|
CanESM2 | Canadian Centre for Climate Modelling and Analysis | Canada | 2.7906 | 2.8125 | ✓ | ✓ | × | ✓ |
GFDL-CM3 | Geophysical Fluid Dynamics Laboratory | U.S.A. | 2 | 2.5 | ✓ | ✓ | ✓ | ✓ |
GFDL-ESM2G | Geophysical Fluid Dynamics Laboratory | U.S.A. | 2.0225 | 2 | ✓ | ✓ | ✓ | ✓ |
IPSL-CM5A-LR | Institut Pierre Simon Laplace | France | 1.8947 | 3.75 | ✓ | ✓ | ✓ | ✓ |
MPI-ESM-LR | Max Planck Institute | Germany | 1.8653 | 1.875 | ✓ | ✓ | × | ✓ |
NorESM1-M | Norwegian Climate Centre | Norway | 1.8947 | 2.5 | ✓ | ✓ | × | ✓ |
Table 3.
Error statistics of lake ice phenology dates estimated from passive microwave remote sensing against site observation. FUE, freeze-up end date; BUE, break-up end date (in days).
Table 3.
Error statistics of lake ice phenology dates estimated from passive microwave remote sensing against site observation. FUE, freeze-up end date; BUE, break-up end date (in days).
Lake Name | Station ID | FUE | BUE | Data Period |
---|
RMSE | MAE | MBE | RMSE | MAE | MBE |
---|
Baikal | NG1 | 7.32 | 12.70 | −12.70 | 5.33 | 23.90 | 23.90 | 1979–2005 |
VSV1 | 11.30 | 9.25 | 8.75 | 2.85 | 8.40 | 6.80 | 1982–1987 |
Qinghai | WYK1 | 2.99 | 3.60 | 3.60 | 2.11 | 4.80 | 4.80 | 2002–2006 |
Winnipeg | WRS311 | 7.60 | 5.46 | 0.39 | 4.70 | 8.08 | 7.75 | 1979–1990 |
Great Slave | WRS255 | 4.49 | 21.20 | 21.20 | 8.05 | 13.20 | −8.17 | 1979–1990 |
WRS256 | 11.80 | 20.50 | 16.80 | 5.08 | 9.08 | −8.92 | 1979–1990 |
WRS257 | 3.29 | 17.70 | 17.70 | 8.29 | 7.00 | −0.60 | 1985–1990 |
Average | | 6.97 | 12.92 | 7.96 | 5.20 | 10.64 | 3.65 | |
Table 4.
Error statistics of lake ice phenology and manual identification during the period 2015–2017 from the MODIS surface reflectivity products (MOD09GA). Optical remote sensing products are greatly affected by persistent cloud cover at low solar zenith angles in winter; therefore, the BUS and BUE were interpreted only in four high-latitude lakes, including Great Bear Lake, Great Slave Lake, Lake Baikal, and Lake Winnipeg. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date (in days); NA, not applicable.
Table 4.
Error statistics of lake ice phenology and manual identification during the period 2015–2017 from the MODIS surface reflectivity products (MOD09GA). Optical remote sensing products are greatly affected by persistent cloud cover at low solar zenith angles in winter; therefore, the BUS and BUE were interpreted only in four high-latitude lakes, including Great Bear Lake, Great Slave Lake, Lake Baikal, and Lake Winnipeg. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date (in days); NA, not applicable.
Lake Name | FUS | FUE | BUS | BUE |
---|
MBE | MAE | RMSE | MBE | MAE | RMSE | MBE | MAE | RMSE | MBE | MAE | RMSE |
---|
Qinghai | −0.50 | 2.50 | 2.55 | −2.33 | 2.33 | 2.38 | −1.67 | 1.67 | 2.08 | −1.00 | 1.67 | 2.38 |
Great Bear | NA | NA | NA | NA | NA | NA | −2.33 | 2.33 | 2.52 | −6.50 | 6.50 | 7.38 |
Great Slave | NA | NA | NA | NA | NA | NA | −2.00 | 2.00 | 3.46 | −2.00 | 2.00 | 2.45 |
Baikal | NA | NA | NA | NA | NA | NA | −2.67 | 2.67 | 2.83 | −3.50 | 3.50 | 4.95 |
Winnipeg | NA | NA | NA | NA | NA | NA | −0.11 | 1.22 | 1.50 | −2.67 | 2.67 | 2.75 |
Average | −0.50 | 2.50 | 2.55 | −2.33 | 2.33 | 2.38 | −1.76 | 1.98 | 2.48 | −3.13 | 3.27 | 3.98 |
Table 5.
Error statistics of lake ice phenology from the CIS product and other studies [
71,
85]. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date (in days); NA, not applicable.
Table 5.
Error statistics of lake ice phenology from the CIS product and other studies [
71,
85]. FUS, freeze-up start date; FUE, freeze-up end date; BUS, break-up start date; BUE, break-up end date (in days); NA, not applicable.
Lake Name | FUS | FUE | BUS | BUE | Data Period | Source |
---|
R2 | MBE | MAE | RMSE | R2 | MBE | MAE | RMSE | R2 | MBE | MAE | RMSE | R2 | MBE | MAE | RMSE |
---|
Great Bear | NA | NA | NA | NA | 0.24 | 5.57 | 5.86 | 5.96 | NA | NA | NA | NA | 0.94 | −15.70 | 15.70 | 2.92 | 2000–2006 | CIS [15] |
Great Slave | NA | NA | NA | NA | 0.35 | 14.90 | 14.90 | 9.46 | NA | NA | NA | NA | 0.75 | −27.60 | 27.60 | 7.40 |
Qinghai | 0.18 | −5.35 | 7.03 | 6.11 | 0.69 | −2.35 | 2.78 | 3.13 | 0.81 | −4.00 | 4.32 | 4.43 | 0.77 | −1.32 | 3.21 | 4.52 | 1979–2015 | SMMR, SSM/I [71] |
0.11 | −9.64 | 9.64 | 5.03 | 0.63 | −1.79 | 2.79 | 2.70 | 0.94 | −2.14 | 2.43 | 2.06 | 0.91 | 3.21 | 3.21 | 2.16 | 2002–2015 | AMSRE/2 [85] |