Temporal and Spatial Characteristics of Precipitation and Temperature in Punjab, Pakistan

Abstract

Identifying the changes in precipitation and temperature at a regional scale is of great importance for the quantification of climate change. This research investigates the changes in precipitation and surface air temperature indices in the seven irrigation zones of Punjab Province during the last 50 years; this province is a very important region in Pakistan in terms of agriculture and irrigated farming. The reliability of the data was examined using double mass curve and autocorrelation analysis. The magnitude and significance of the precipitation and temperature were visualized by various statistical methods. The stations’ trends were spatially distributed to better understand climatic variability across the elevation gradient of the study region. The results showed a significant warming trend in annual Tmin (minimum temperature) and Tmean (mean temperature) in different irrigation zones. However, Tmax (maximum temperature) had insignificant variations except in the high elevation Thal zone. Moreover, the rate of Tmin increased faster than that of Tmax, resulting in a reduction in the diurnal temperature range (DTR). On a seasonal scale, warming was more pronounced during spring, followed by that in winter and autumn. However, the summer season exhibited insignificant negative trends in most of the zones and gauges, except in the higher-altitude Thal zone. Overall, Bahawalpur and Faisalabad are the zones most vulnerable to warming annually and in the spring, respectively. Furthermore, the elevation-dependent trend (EDT) indicated larger increments in Tmax for higher-elevation (above 500 m a.s.l.) stations, compared to the lower-elevation ones, on both annual and seasonal scales. In contrast, the Tmin showed opposite trends at higher- and lower-elevation stations, while a moderate increase was witnessed in Tmean trends from lower to higher altitude over the study region. An increasing trend in DTR was observed at higher elevation, while a decreasing trend was noticed at the lower-elevation stations. The analysis of precipitation data indicated wide variability over the entire region during the study period. Most previous studies reported no change or a decreasing trend in precipitation in this region. Conversely, our findings indicated the cumulative increase in annual and autumn precipitation amounts at zonal and regional level. However, EDT analysis identified the decrease in precipitation amounts at higher elevation (above 1000 m a.s.l.) and increase at the lower-elevation stations. Overall, our findings revealed unprecedented evidence of regional climate change from the perspectives of seasonal warming and variations in precipitation and temperature extremes (Tmax and Tmin) particularly at higher-elevation sites, resulting in a variability of the DTR, which could have a significant influence on water resources and on the phenology of vegetation and crops at zonal and station level in Punjab.

Analysis of spatial changes of extreme precipitation and temperature in Iran over a 50‐year period

“…In another study in Pakistan (eastern neighbour of Iran), Nawaz et al . (2019) found that the rate of Tmin increased faster than Tmax, which is in line with our findings. Some studies have been conducted on the global scale, which are somewhat in good agreement with this study.…”

“…In contrast to the decreasing precipitation in the present research, Nawaz et al . (2019) found a cumulative increase in amounts of annual precipitation in Punjab, Pakistan. Moreover, reports provided from studies by Supari et al .…”

Future Changes in Seasonal Temperature Over Pakistan in CMIP6

“…The warming tendency across central Pakistan in this study yielded higher warming in the near and far future DJF season than in JJA under all SSP scenarios (Figures 3 and 4). The region consists of mostly plain terrain (Indus plains), deserts and hilly regions in western edges and over northern parts (Nawaz et al, 2019). This region accommodates most of country's population with vast glacier water irrigated lands and is major industrial hub of the country (Abbas, 2013).…”

Evaluation of Historical CMIP6 Model Simulations of Seasonal Mean Temperature over Pakistan during 1970–2014

“…Further, in the study, CMIP6 models and CRU datasets showed a significant increase in mean temperature trends in this study, particularly higher over the north during DJF over Pakistan. Many studies [12][13][14]64] identified increasing trends in winter and summer (0.17 • C-0.37 • C/decade) over Pakistan's central and northern regions. Babar et al [35] discovered a higher (0.21 • C/decade) winter mean temperature rise than in summer (0.21 • C/decade) for CRU; 0.11 • C-0.06 • C/decade in UDEL dataset and 0.10 • C-0.09 • C/decade in CMIP5 ensemble.…”