3.1. Absolute Changes and Trends of Temperature Indices
provides the graphical demonstration of annual time series and the linear trends for climatic variables for each irrigation zone as well as for of the whole region of Punjab. The results of linear trends and coefficient of determination of Tmin
data series indicate a clear increasing trend. Meanwhile, the trends and coefficient of Tmax
data series depicted non-significant trends and lower r-squared values in most of the zones except for the Thal zone. On the other hand, the DTR data series showed a higher decreasing trend with higher r-squared values, which can be attributed to the higher rate of the increasing trend in Tmin
than that of Tmax
. The highest value of r-squared in Tmean
data series was observed for Bahawalpur and Multan zone, respectively. Moreover, the highest r-squared value in Tmax
and DTR data series was noticed for Thal and Sargodha zone, respectively. Overall, the linear increase in the Tmin
data series was more conspicuous than that of the Tmax
in most of the zones and for of the overall Punjab region, during the whole study period. The most significant rapid change in temperature’s linear trends was observed during the period 1997–2002 for most of the zones and for the whole Punjab region. According to [19
], the country faced a severe and long lasting drought during this period. The rapid increase in temperature trends during the aforementioned period in Punjab region could be owing to the upshots of severe drought conditions in major parts of the country.
The annual and seasonal absolute change and trends of Tmax
, and DTR for all of Punjab Province obtained by the MW, MK, and Theil–Sen approaches are presented in Table 2
and Table 3
. Meanwhile, the annual and seasonal absolute changes and trends of Tmax
, and DTR for the irrigation zones other than the entire Punjab basin are presented in Tables S2 and S3 in the SI
. The results (MW and MK) indicated that Tmax
exhibited a positive absolute change and increasing trend in the higher elevation Thal zone in the annual, winter, spring, and Rabi seasons, with the highest increase assessed during the spring season with magnitudes of 0.94 °C and 0.29 °C/decade, respectively. However, conflicting signals of insignificant positive and negative trends were observed on a seasonal scale in most zones.
The spatial distribution of the annual and seasonal trends of Tmax
is presented in Figure 3
. The MK trends of the annual Tmax
showed conflicting signals of non-significant positive and negative trends over the whole basin. In particular, the Murree and Islamabad stations, which are located at high altitudes, exhibited a significant increasing trend in Tmax
with magnitudes of 0.55 and 0.24 °C/decade, respectively. In contrast, the highest reduction in Tmax
was observed at Mianwali (−0.16 °C/decade), followed by Sarghoda (−0.13 °C/decade) station. In winter, Tmax
indicated a slight declining trend at most stations except for the higher-altitude Muree and Islamabad stations.
In contrast, the spring season indicated an insignificant increasing trend of Tmax
at most sites. However, a significant increasing trend in Tmax
was observed for the Murree, Islamabad, and Lahore stations, with rates of 0.61, 0.28, and 0.33 °C/decade, respectively. In summer, most of the gauge sites showed an insignificant declining trend except for the Muree, Islamabad, and Bahawalnagar stations, which indicated significant increasing trends. The decrease in Tmax
during the summer season is in agreement with the findings of [57
], who reported a decreasing trend in some parts of the country. The highest declining trend in Tmax
was observed at the Mianwali station with a magnitude of −0.42 °C/decade. Meanwhile, the autumn season revealed a decreasing trend at most sites, with the highest reduction observed at the Mianwali (−0.32 °C/decade) station.
On the other hand, the seasonal (crop growing) Tmax
showed a slight increasing trend at most stations in the Rabi season, while the Kharif season revealed a minor decrease in Tmax
. A significant negative trend was observed at the elevated gauge sites of Muree and Islamabad for the Rabi season, while two gauge sites, Muree and Bahawalnagar, showed negative trends for the Kharif season. Overall, the annual and seasonal Tmax
trends varied from −0.45 to 0.75 °C/decade. The increasing tendency of Tmax
at high altitudes are consistent with the previously reported work, for the northern belt of Pakistan by [58
]. Additionally, the decreasing trend in Tmax
observed in this work is in conformity with the findings of [59
]. Furthermore, our zonal and spatial results are in good agreement with the findings of [17
], where it is reported that the trend of Tmax
at the annual scale increased at a rate of 0.12 °C/decade in Pakistan (country level). The present study highlights a significant increase in Tmax
in the Thal zone at a high elevation compared to that at lower elevations. The increasing trend of Tmax
in the higher elevation zone could have a major impact on water resources and agriculture from different perspectives. Nevertheless, this change could have positive implications, such as shortening the crop growing period, as suggested by [60
], and it may also lead to an accelerated snow melting process and substantial changes in the amount and pattern of precipitation [18
Due to significant changes in precipitation, disproportionate snow melting can cause rivers to overflow, which may consequently cause flooding in the low-elevation zones [61
]. Nonetheless, the seasonal negative variations in Tmax
could be a possible explanation for the westerlies and monsoon periods in the different zones [62
]. In the case of Tmin
, the results indicated the absolute positive change and increasing trends at the annual and seasonal time scales. The maximum positive absolute change and increasing trend were observed in the Bahawalpur zone during the annual and spring seasons with magnitudes of (1.01 and 1.26 °C absolute changes) and (0.35 and 0.48 °C/decade trends), respectively.
Overall, the spring season showed the highest increasing trend for the nighttime temperature in the southern zone. The increasing trend in Tmin
at the annual and seasonal scales strengthened the results of previous studies for different areas of Pakistan [17
]. However, the non-significant magnitude of the increasing trend in the summer season conflicted with the results of [59
], where a sharp increase in trends during the summer season was reported in different zones of the country. The outcomes of the present study are in harmony with the findings of [18
] for the summer season.
The spatial distribution of the annual and seasonal trends in Tmin
is presented in Figure 4
. The spatial MK trends of the annual Tmin
revealed a clear tendency of warming over the entire Punjab basin except at the Barkhan station, which exhibited a significant decreasing trend with a magnitude of −0.12 °C/decade. The highest positive trend in Tmin
was observed for the Sargodha station with a magnitude of 0.46 °C/decade. For the winter season, the Tmin
revealed a clear increasing tendency, except for the insignificant decreasing trend in the Tmin
at the Murree and Barkhan stations.
The warming in the winter season was also reported by [63
] at the country level. Similarly, in the spring season, Tmin
showed a significant increasing behavior at most stations located in central and southern Punjab, except for Barkhan, which had an insignificant decreasing trend. Our results are consistent with the finding of [64
]. The highest increase in Tmin
was observed at the Bahawalnagar station with a magnitude of 0.58 °C/decade. This value was the highest magnitude observed at the annual and seasonal scales. Meanwhile, the trend analysis of the climatic variables in the summer season revealed a conflicting signal of negative and positive slopes at most stations in Punjab. The inclinations in Tmin
indicated an insignificant increasing trend for most stations except D.I. Khan and Barkhan, where significant decreases were observed. The maximum increase in Tmin
was observed at the Khanpur (0.24 °C/decade) station. The variations in the autumn season indicated a clear tendency of a conspicuous increase in Tmin.
The maximum increasing trend in Tmin
was observed at the Khanpur station with a magnitude of 0.59 °C/decade. The results were in accordance with the findings of [16
] for autumn Tmin
over the whole region.
Furthermore, the seasonal (crop growing) trends in Tmin
revealed a very clear tendency of warming at most stations, except for the northwestern stations, which showed slight insignificant decreasing trends. The highest trend magnitude in Tmin
was observed at the Sarghoda (0.51 °C/decade) and Khanpur (0.42 °C/decade) stations in the Rabi and Kharif seasons, respectively. Overall, the annual and seasonal Tmin
trends varied from −0.25 to 0.60 °C/decade. The present results indicated elevated trends in Tmin
with a faster rate than that of Tmax
in the different irrigation zones and stations, except for the high-elevation sites, and this difference could have a serious impact on the evapotranspiration rate and consequently on crop productivity [57
]. In addition to direct effects on plant physiological processes, increases in Tmin
could affect plant growth by changing the duration of the growing season or by changing the soil water availability [65
]. It was also suggested that nighttime warming aggravates the adverse effects of soil water stress, as reported in [66
], and could reduce the productivity of the rice crop by 10% for each 1 °C increase in the growing season [67
]. Overall, there is a need for comprehensive research on the interaction between elevated Tmin
and the ecosystem for the region under study. The interactions between climatic variability and different ecosystem characteristics are not considered in the present work because that is beyond the scope of the study.
The analysis of Tmean
indicated a positive absolute change and warming trends at the annual and seasonal scales, with the exception of the summer season, which showed a decreasing trend. On an annual scale, the maximum absolute change and trend was observed in the Bahawalpur zone with magnitudes of 0.64 and 0.20 °C/decade, respectively. The present results of the annual trends also confirm the findings of [68
], who reported a slope of annual Tmean
of approximately 0.24 °C/decade in Pakistan during 1960–2007. On a seasonal scale, the maximum change and trend were observed in the Faisalabad zone during the spring season with magnitudes of 1 and 0.34 °C/decade, respectively. Meanwhile, the summer season showed a negative trend in the entire Punjab basin. The decreasing trend of Tmean
in the summer season was previously reported for other areas of Pakistan [63
]. The spatial distribution of the annual and seasonal trends of Tmean
is presented in Figure 5
. The MK results for the annual Tmean
showed a warming trend over the entire Punjab basin except for the Barkhan station, which exhibited a significant decreasing trend with a magnitude of −0.05 °C/decade. The highest positive trend in the annual Tmean
was observed for the Muree station with a magnitude of 0.27 °C/decade. These observations contradict the findings of [60
], who reported negative trends in temperature at high-altitude regions in the country.
In winter, the Tmean revealed a clear increasing tendency at most stations except for Muree and Barkhan. Similarly, the spring Tmean showed a significant increasing behavior at most stations, with the highest increase observed at Bahawalnagar with a magnitude of 0.44 °C/decade; however, an insignificant decreasing trend was observed at Barkhan. In contrast, the summer season revealed a conflicting signal of negative and positive slopes at most stations in Punjab, with the highest positive trend observed at Muree and Islamabad at a rate of 0.16 °C/decade. The variations in the autumn season indicated a clear tendency for a conspicuous increase in the Tmin. The maximum increasing trend in the Tmean was observed at the Khanpur station with a magnitude of 0.32 °C/decade.
Similarly, trends in Tmean
during the crop growing seasons revealed a clear tendency of warming at most stations except for those in the northwest, where slight insignificant decreasing trends were observed. The highest trend magnitude in Tmean
was observed at the Bahawalnagar station in the Bahawalpur zone with magnitudes of 0.26 and 0.23 °C/decade in the Rabi and Kharif seasons, respectively. The overall annual and seasonal Tmean
trends varied from −0.25 to 0.45 °C/decade. The increasing trend of Tmean
in different zones and stations has been related to various aspects, such as the concentration of anthropogenic activities, aerosol effects on the climate, increased cloud cover, land-use change, and industrial growth [69
]. It is also suggested that there is a significant effect of urbanization and land-use change on surface warming at the local scale [70
]. The present findings report a higher increasing trend of Tmean
in the Faisalabad zone, which is a highly populated and industrial hub of the country; these findings are associated with the results of previous studies related to warming caused by urbanization and industrial development. [27
] reported similar findings in different industrial and populated cities of Pakistan. In addition, various agricultural practices, such as increased irrigation and different cropping patterns, may have potential impacts on the Tmean
trends in the Indian sub-continent [71
Furthermore, the magnitude of the absolute change and trends of the DTR demonstrated a significant decreasing shift at the annual and seasonal scales for the different zones except those located at higher elevations (e.g., Thal and D.G Khan showed a non-significant increasing trend in the winter, spring, and Rabi seasons). On an annual scale, the highest negative absolute change and trend was observed in the Faisalabad and Bahawalpur zones, with magnitudes of −0.79 and −0.36 °C/decade, respectively. Similarly, on a seasonal scale, the highest declining change and trend was observed in the Sarghoda zone during the autumn season, with magnitudes of −1.45 and −0.57 °C/decade, respectively. Overall, there was a clear decreasing tendency in the DTR data series over the entire study region.
The spatial distribution of the annual and seasonal trends of the DTR is presented in Figure 6
. The spatial MK trends of the annual DTR indicated a declining behavior at most stations except Muree and Barkhan, where a significant increase in the DTR was observed. The maximum increasing and decreasing trends were observed at the Murree (0.55 °C/decade) and Sarghoda (−0.58 °C/decade) stations, respectively. In the winter season, most stations showed significant declining behavior, with the highest fluctuation observed at Muree and Sarghoda, at rates of 0.82 and −0.71 °C/decade, respectively. Similarly, in the spring season, most of the gauge sites showed negative trends except for the high-altitude Murree and Barkhan stations. In contrast, the summer DTR values were characterized by positive and negative trends over the entire Punjab basin, with the highest increase observed at Murree (0.41 °C/decade) and D.G. Khan (0.22 °C/decade), while the greatest reduction was observed at Khanpur station (−0.52 °C/decade).
Moreover, trends in the DTR during the crop growing seasons exhibited a negative change at most stations except those in the northern and northwestern sites, which showed significant increasing trends, particularly at Murree, D.G. Khan, and Barkhan. The overall annual and seasonal DTR trend varied from −0.85 to 0.85 °C/decade in the Rabi and Kharif seasons, respectively. The magnitude of the decrease in the DTR during Rabi was greater than that of the Kharif season. The highest increase and decrease were observed at Murree (0.64 °C/decade) and Sarghoda (−0.69 °C/decade) for the Rabi season, and at Murree (0.43 °C/decade) and Khanpur (−0.56 °C/decade) for the Kharif season. These results are also supported by previous findings in the region [27
]. Several past reports suggest that there is a strong relationship between the cloud cover and DTR. More cloud cover is associated with a decrease in the DTR [72
]. Similarly, the outcomes of the present study, which indicated a decreasing trend in the DTR for the autumn, summer, and Kharif seasons, indicate a negative relationship with cloud cover and the occurrence of significant precipitation during these seasons.
3.2. Annual and Seasonal Trends of Precipitation
The annual time series and linear trends of precipitation for each irrigation zone and for the entire province of Punjab are presented in Figure 7
. The annual average precipitation showed a slight increasing trend in all zones, including the whole basin, during the study period 1967–2017. The corresponding regression line along with r-squared values were also plotted for each irrigation zone and for all of Punjab. The southern zones, including Bahawalpur, Multan, and D.G. Khan, showed an annual precipitation frequency of approximately 100–300 mm. However, the central zone (Faisalabad, Lahore, and Sarghoda) and the northern zone (Thal) indicated precipitation frequencies of approximately 400–700 and ≥ 1000 mm, respectively. Similarly, the entire Punjab basin showed an annual precipitation of approximately 400–500 mm. The highest and lowest r-squared values were noticed in Bahawalpur and Lahore zones, respectively. The highest fluctuation in linear trend was observed in Thal followed by the Lahore zone. In addition, the annual and seasonal precipitation trends and magnitude for the entire Punjab basin obtained by the MK test and the Theil–Sen approach are presented in Table 3
. Meanwhile, the annual and seasonal precipitation trends for irrigation zones other than the entire Punjab basin are presented in Table S3
in the SI. Finally, the spatial distributions of the annual and seasonal precipitation trend of the stations are presented in Figure 8
The results of the MK test indicated the wide variability of precipitation for the annual and seasonal time scales in the majority of the zones during the period 1967–2017. The annual precipitation revealed a significant increasing trend in all irrigation zones, with a magnitude ranging from 15.01 to 34.45 mm/decade. The maximum cumulative increase in annual precipitation was observed in the Thal zone (34.83 mm/decade), followed by Sarghoda (25.55 mm/decade) and Lahore (23.45 mm/decade). Similarly, the spatial distribution of the annual station trends showed that most sites were characterized by non-significant positive trends.
However, considerable positive tendencies were observed at low elevation for the Bahawalnagar, Bahawalpur, Khanpur, and Mianwali stations at rates of 16.4 21.57, 27.09, and 57.73 mm/decade, respectively. In contrast, a decreasing trend was detected for the high altitude Murre station, with a value of −45 mm/decade, in the Thal zone. The increasing trend of annual precipitation in southern Punjab contradicted the results of [73
], who reported a decreasing trend in annual precipitation in this region. In winter precipitation, the negative trends were more obvious over the whole region, particularly in the D.G. Khan and Bahawalpur zones, including the entire Punjab basin. The negative trend in the winter season correlates with the findings of [74
], who reported a decreasing trend of precipitation in different areas of Pakistan. The spatial distribution of the MK results showed that most stations revealed insignificant signs of positive and negative slopes during the winter season. Most of the winter precipitation was due to western disturbances, and consequently, most stations in the study area indicated less precipitation. The maximum decline in winter precipitation was observed at the high-altitude Murree station (−28.5 mm/decade) in the Thal zone.
The zonal trend analysis of spring precipitation showed insignificant negative and positive increases over the whole basin. However, prominent increasing trends were observed in the southern zone, while significant decreasing trends were observed in the northern zones of Punjab. The spatial distribution of the MK trends indicated variable fluctuations for most stations. However, a significant increase was observed for the Bahawalnagar station, at the rate of 4.41 mm/decade. In summer precipitation, the MK trend results illustrated the insignificant positive trends in different irrigation zones and all of Punjab, except for the Bahawalpur zone, which showed a significant increase during summer. The highest increase was assessed in the Lahore and Sargodha zones, with a rate of 11.76 mm/decade. Similarly, the spatial distribution of the station trends indicated an insignificant increasing trend over the entire study area. According to the MK analysis results, 13 stations showed positive trends, while three stations revealed negative tendencies. A significant increasing trend was detected at the Mianwali and Khanpur stations, with magnitudes of 35.68 and 12.14 mm/decade, respectively.
Meanwhile, autumn precipitation revealed a significant increasing trend in all zones, with a magnitude ranging from 0.78 to 9.81 mm/decade, with the highest increase assessed in the Thal zone at a rate of 9.81 mm/decade. The spatial distribution of station trends indicated that 14 out of 16 stations showed a positive trend; Barkhan and Sialkot, which exhibited negative trends, were the two outliers. The highest increasing trend was observed at the Islamabad station (17.26 mm/decade) in the Thal zone.
In addition, the precipitation trends during the crop growing seasons (Rabi and Kharif) indicated non-significant increasing trends in most zones except for the Bahawalpur zone, which showed a significant increase during the Rabi and Kharif seasons, while the entire Punjab basin showed a significant increase during the Kharif season. The highest increase was observed during the crop growing period at Sarghoda in the Rabi and Thal zones in the Kharif season, with rates of 5.22 and 30.92 mm/decade, respectively. The overall zonal trend magnitudes ranged from 1.23 to 5.22 and 11.68 to 30.92 mm/decade during the Rabi and Kharif seasons, respectively. Moreover, the spatial distribution of precipitation trends during the crop growing seasons (Rabi and Kharif) indicated considerable fluctuations at most stations. Furthermore, the station precipitation indicated that the magnitude of the positive trend in Kharif was more pronounced than in the Rabi season. The overall annual and seasonal precipitation trends magnitude ranged from −50 to 60 mm/decade during the Rabi and Kharif seasons, respectively. The findings of the current investigation for summer season contradict the results of [64
], who reported a considerable increase in precipitation during the summer season. Moreover, the entire Punjab basin showed a significant increasing trend of precipitation for the annual and autumn seasons, with magnitudes of 22.24 and 5.23 mm/decade, respectively. Similar results were reported by [21
] in different regions in Pakistan. In addition, the Bahawalpur zone indicated a slight significant increasing trend in precipitation at all time scales except for the winter season. Altogether, the study area exhibited a significant positive shift in annual and autumn precipitation compared with that in the other seasons.
3.3. Annual and Seasonal Elevation-Dependent Trends (EDTs)
The analysis for annual EDT in temperature indices (Tmax
, DTR) and precipitation over the Punjab region is shown in Figure 9
(black dash linear fit). The geographical locations of the available stations in the region of Punjab located between the elevation range of 55–2167 (m a.s.l.) are shown in Table 1
. The EDT result of Tmax
indicates a positive gradient from lower to higher elevation with significant positive trends observed at higher elevation (above 500 m a.s.l.), with the magnitude of 0.55 and 0.24 °C/decade at Murree and Islamabad stations (p =< 0.01). On the contrary, the EDT of Tmin
showed a negative slope from lower to higher elevation with an overall significant positive trend for most of the low elevation stations, except for the higher-altitude Barkhan and Murree stations. Furthermore, the EDT in Tmean
showed a moderate increasing slope from lower to higher altitude with significant positive trends for most of the stations. However, the EDT in DTR showed a steep slope from lower to higher altitude with a significant increase at higher elevation stations above 500 m a.s.l. On the other hand, the EDT analysis for precipitation indicates a negative gradient from lower to higher altitude, with overall positive trend at most of the stations at lower elevation and significant negative or no trend for the high-altitude stations, particularly Murree and Barkhan (above 1000 m a.s.l.). Overall, the results indicate an increase in the amount of precipitation at low-elevation stations, whereas, a decrease in amount of precipitation was noticed for higher-elevation stations. A decrease in precipitation for higher elevation (above 4000 m a.s.l) was also reported by [22
] for different sub-basin levels in Upper Indus Basin by assembling different reanalysis products, during the period 1997–2014. As a consequence, decline in river flows was reported for different sub-basins in the UIB. Similarly, the results of EDTs for temperature indices and precipitation, obtained in this study, concur well with the findings of [75
] who reported a similar increasing trend in Tmax
and DTR, as well as a decrease in Tmin
and precipitation trends, with a moderate positive slope in Tmean
from lower to higher gradient across the longitudinal extension of Nepal. However, for the region of Punjab, most stations are located at less elevation, yet the results obtained from the EDT analysis are highly significant, particularly for the futuristic studies related to the elevation-dependence warming over the region under study.
The EDT analysis presented in Figure 9
(black dash linear fit) deals with the 16 stations located between the elevation range of 55–2167 m a.s.l. However, most of the stations in this range are located below 500 m a.s.l., in exception to three stations (Murree, Islambad, and Barkhan) that are located above the said elevation. Generally, a chance of uncertainty could exist if such a smaller number of stations (above 500 m a.s.l) are utilized to perform EDT analysis,. Under such scenario, the uncertainty of the gauge data can be minimized by assembling different atmospheric reanalysis products. For instance, [22
] quantified the uncertainty of climatic variables by using six atmospheric reanalysis products for cross validation of river flow data for poorly gauged regions. Meanwhile, another way to deal with such scenarios, where there are lesser number of stations involved, is to extend the analysis by incorporating data from a greater number of stations (if available) and compare the outcomes with the results obtained for analysis performed for fewer number of stations. Therefore, in order to address any ambiguities related to the results of our analysis for elevation-dependent temperature indices (Tmax
, DTR) and precipitation trends, we performed the additional EDT analysis by including a greater number of higher elevation meteorological stations (Table 4
). The stations that cover the continuous elevation range above 500–2167 m a.s.l. were incorporated in the EDT extension analysis, as can be seen through Figure 9
(red linear fit). The outcome of EDT analysis, which included the additional stations, indicated a similar linear trends in the precipitation and the temperature indices, as was observed for the stations under the scope of this study (the trend is presented as black dash linear fit). Moreover, the additional stations in EDT extension analysis confirmed an analogous trend pattern, and data quality with overall higher range of magnitude and better statistical significance along the extension gradient of the Punjab and surrounding region at higher elevation.
The spatial and seasonal distributions of EDT of temperature indices (Tmax
, DTR) and precipitation over the Punjab region are shown in Figure 3
, Figure 4
, Figure 5
, Figure 6
and Figure 8
. Significant positive trends in Tmax
were noticed at higher-elevation (above 500 m a.s.l.) sites in Thal and D.G. Khan zones, while low-elevation sites did not show any trend or negative slopes at the seasonal scale. The highest positive trends were observed in the winter season at higher-elevation Murree, Islamabad, and Barkhan sites, with the magnitude of 0.74, 0.47, and 0.48 °C/decade, respectively. The trend in Tmax
is highly sensitive with respect to the elevation and can be easily detected by spatial distribution of trends. The current findings of Tmax
trends are in consistence with the results of [75
], wherein higher trends in temperature in Nepal at elevations above 1000 m a.s.l. were reported and were said to be homogenous for all seasons. Similarly, [77
] reported the increasing trends of Tmax
at higher elevation in Nepal during the 1990s, without finding any further significant dependence of these trends on the elevation levels.
Further, in our study, EDT in Tmin
revealed positive slopes for most of the sites at low elevation, while negative or no trends in Tmin
were observed for all seasons at high-elevation (above 500 m a.s.l) sites. In accordance with Tmin
trends, the seasonal and spatial EDT of Tmean
indicates the positive significant slopes in all seasons except summer. However, the higher-altitude Islamabad and Murree stations in the Thal zone showed an increasing trend during the summer season. In case of DTR, the higher-altitude (above 500 m a.s.l.) sites (i.e., Murree, Islamabad, and Barkhan stations) showed positive slopes in all seasons, while the highest trends were observed in the winter season with the magnitude of 0.82, 0.23, and 0.56 °C/decade, respectively. In addition, the low-elevation sites (less than 500 m a.s.l.) indicated negative DTR trends at the seasonal scale. The results of increasing trends in Tmax
and DTR are related to the decrease in the cloud cover, while the precipitation at higher elevation are consistent with the previous findings by [78
] for Central Asia and [79
] for India, where similar results were reported, owing to a decrease in cloud cover and precipitation, with the increase in temperature trends. The seasonal and spatial EDT of precipitation showed the positive slopes at low elevation sites in all seasons, with an exception for the winter season where negative trends were observed for most of the sites. Moreover, the higher-elevation sites (above 1000 m a.s.l.) showed a negative pattern, which resulted in a negative gradient in precipitation amounts from lower to higher elevation across the Punjab region. The outcomes of this study regarding the increase in amounts of precipitation for lower-elevation regions are consistent with the findings of [80
], wherein the increase in precipitation amounts and its impact on the increase in Tmin
trends were discussed. The results of the higher decreasing trend of precipitation at annual and seasonal scale at higher elevation, and particularly results of Murree station (above 2000 m a.s.l), are associated with findings of [75
], which reported a decreasing trend in annual precipitation from lower to higher elevation. The possible explanation of decreasing precipitation at higher elevation could be linked with the decrease in cloud cover and soil moisture and, ultimately, increase in day time and decrease in nighttime temperatures (Tmax
]. However, an in-depth investigation is required to explore, in detail, the quantitative relationship between precipitation and temperature indices and to learn about the main driving factors for such asymmetric trends of temperature and precipitation for Punjab, which is a highly worthwhile region with respect to the agriculture and economy of Pakistan.