Analysis Of Hydro-Climatic Trends And Associated Teleconnection Over Pakistan

Temperature and precipitation is a critical necessity for the long-term development of ecosystems and communities in dry regions that are sensitive to the effects of climate change.Pakistan has been struck by extreme flooding and droughts over the past decade.Such,variation in climate is expected to impact the glaciological processes and river runoff in the high altitude of the Himalayas.The Glacio-hydrology of mountainous areas has significant implications for the socio-economic profile of downstream regions under climate change.Therefore,understanding the coherent variability of precipitation and runoff with the regional environmental parameters and global Oceanic indices like,the ISMI,IOD,ENSO,PDO,SOI,NAO,AMO and AO over Pakistan.In first study,the results show a widespread warming trend of 0.04 ^oC/decade for T_max but a cooling trend of-0.02 ^oC/decade for T_min although non-significant during 1955–2016 for the whole UIB,and larger spatial heterogeneity is observed for T_min.Seasonally,warming in T_max are much stronger in winter and spring,while the cooling in T_min are greater in summer and autumn.Precipitation exhibit no significant changes for the whole UIB,but with the most significant trend of 2.3 mm/decade being detected in winter and the only decreasing trend being observed in spring.Temperature and precipitation variations also exhibit obvious changes in different phases.The warming in T_max and the increase in precipitation are more distinct since the mid-1990s,while the cooling in T_min is dominated in the UIB from the mid-1980s.The impacts of elevation variation on climate are very obvious.Warming in the middle and higher altitude gradients（1500–2800 m and>2800 m）are much stronger,and besides precipitation,increase is more obvious in regions with elevation>2800 m in the UIB.The second study assesses spatial and temporal trends in seasonal and annual precipitation in Pakistan between 1960 and 2016 at an interannual scale.In general,increasing precipitation trends between 1960 and 2016 were evident.Results indicated increasing precipitation in winter,autumn,summer,and annual scale at the rates of 0.20,2.18,5.16,10.89 mm/decade,respectively.In spring,the precipitation trend shows a decreasing trend at-0.67 mm/decade.Moreover,a significant decreasing trend occurred in winter in southern Pakistan.The overall increasing trends were more noticeable between 1960 and 1988,compared to the declining precipitation during 1989–2016.SQMK analysis indicates a clear downward trend in most regions during 1989–2016,except in autumn.Annual precipitation has increased topographically except at 500 m and 1500 m during 1960–2016 with a significant increase of 1.37 mm/decade at elevation<250 m.Results indicate a negative correlation in seasonal and annual precipitation with elevation and a positive correlation in winter.The seasonal and annual precipitation trends exhibit increasing and decreasing trends before and after 1990,respectively,in most sub-regions.The notable finding based on the outcomes of this study is that:the whole country observed an increasing trend during 1960–1988,followed by a decreasing trend in during 1989–2016,this decreasing tendency is particularly pronounced between 1985 and 1995,except in autumn.Agriculture production is largely reliant on precipitation in many regions.In third study,the wavelet coherence analysis has been utilized,a time-frequency domain methodology for comparing the spectral features of two independent time series superior to linear approaches.This technique is used to capture the significant modes of variabilities in the ISMI,IOD,ENSO,PDO,SOI,NAO,AMO and AO over Pakistan.In general,the ISMI displayed the most coherences（except in the UIB）compared to the large-scale CIs over various regions on an inter-annual scale.The dominant influence of ISMI is observed in R-II and III.The significant coherences in R-II ranged from～8–32 months（～0.8–2.8 years）through the entire period.Whereas the remaining CIs have an almost similar pattern of inter-annual coherences over various regions.However,IOD and NAO had major coherences compared to the remaining large-scale CIs ranging from～16–64 months（1.3–5.3 years）.The AO had the most significant coherences observed in R-II,III,and VI throughout the study on the decadal/inter-decadal scale from 128 months and above（almost 10–15 years）.However,these observed coherences are not that significant to observed coherences in the AO.On a 1.0-year time scale,all areas demonstrated strong but intermittent coherence in all CIs over Pakistan.Fourth study explores the relationship of the SRIR runoff with the regional environmental factors and oceanic indices.Monthly runoff from all sub-basins shows increasing tends from October to March,while decreasing from April to September,except for western tributaries.Most sub-basins in the SRIR are experiencing significant increases in winter,while decreases in summer.The trends in annual runoff are increasing after 2000 from the Kabul River Basin（KRB）.However,contrasting results are evident in the Upper Indus Basin（UIB）.Furthermore,the Jhelum River Basin（JRB）shows a significant decline trend from the mid-1990s.Annual runoff（3.19 m³/s）,precipitation（0.24 mm/year）,temperature（0.011 ^oC/year）,and NDVI（0.002）increased in the SRIR,whereas,PET（-0.020 mm/year）and NDSI（-0.003）declined during 1970–2016.Overall,all the factors displayed a positive correlation with the runoff.However,NAO,AO,and ISMI shared a significant correlation.Generally,runoff has a stronger association with regional environmental factors than global ones,as evident in correlation and wavelet analysis,which implies that local factors had a more significant effect on runoff.