Spatiotemporal changes of evaporation in Golestan province based on quantile regressions

Abstract

The results reveal statistically significant trends with distinct slopes in distinct quantiles for each station and season so that the changes in the trend of high values (quantile 0.9) of evaporation were more than low values (quantile 0.1). In the spring, medium and high evaporation rates increased in the northern regions of the province (the highest trend slope, 0.15 mm/decade in the northeast), while they fell (with a slope of −0.15 mm/decade) in the southern regions. But the high values of evaporation in summer have increased in most of the stations (the highest trend slope, 0.15 mm/decade). In contrast, high levels of evaporation in autumn and winter grew at a rapid rate in the eastern part of the province (the highest slope according to season, 0.15 and 0.2 mm/decade), but they declined in the western half (the highest slope, −0.1 and −0.15 mm/decade, respectively). In general, there was a significant decreasing trend for evaporation, mostly in the western half, but there was an increasing trend, mostly in the eastern half of the province. Significant increases in daily evaporation, particularly during the dry season, will diminish water supplies, destabilize the agricultural sector, and eventually desertify the area. HIGHLIGHTS The trend of evaporation pan was investigated by the quantile regression method.; The amount of change in different quantiles of evaporation pan was estimated.; The high values of evaporation increased in different seasons.; The slope of the trend was different for different amounts of evaporation.;

Keywords

• evaporation
• extreme values
• golestan
• quantile regression
• spatiotemporal trends