Trend analysis of evapotranspiration over India: Observed from long-term satellite measurements

Abstract

Owing to the lack of consistent spatial time series data on actual evapotranspiration (ET), very few studies have been conducted on the long-term trend and variability in ET at a national scale over the Indian subcontinent. The present study uses biome specific ET data derived from NOAA satellite's advanced very high resolution radiometer to investigate the trends and variability in ET over India from 1983 to 2006. Trend analysis using the non-parametric Mann-Kendall test showed that the domain average ET decreased during the period at a rate of 0.22 mm year −1. A strong decreasing trend (m = −1.75 mm year −1 , F = 17.41, P <0.01) was observed in forest regions. Seasonal analyses indicated a decreasing trend during southwest summer monsoon (m = −0.320 mm season −1 year −1) and post-monsoon period (m = −0.188 mm season −1 year −1). In contrast, an increasing trend was observed during northeast winter monsoon (m = 0.156 mm season −1 year −1) and pre-monsoon (m = 0.068 mm season −1 year −1) periods. Despite an overall net decline in the country, a considerable increase (>4 mm year −1) was observed over arid and semi-arid regions. Grid level correlation with various climatic parameters exhibited a strong positive correlation (r > 0.5) of ET with soil moisture and precipitation over semi-arid and arid regions, whereas a negative correlation (r<−0.5) occurred with temperature and insolation in dry regions of western India. The results of this analysis are useful for understanding regional ET dynamics and its relationship with various climatic parameters over India. Future studies on the effects of ET changes on the hydrological cycle, carbon cycle, and energy partitioning are needed to account for the feedbacks to the climate.

Onset of summer monsoon in Northeast India is preceded by enhanced transpiration

“…Goroshi et al . 8 found a strong positive correlation between ET and insolation in NE India implying that insolation and ambient air temperature are major stress factors affecting ET in this region. Correct quantification of evaporation and transpiration in any hydrological model is necessary to reduce uncertainties in the hydrological budget.…”

Improving the Representation of Long‐Term Storage Variations With Conceptual Hydrological Models in Data‐Scarce Regions

“…It would therefore be interesting to look into alternative, potentially more accurate estimation methods. In addition, long-term fluctuations in the actual evaporation were observed depending on the satellite product due to the different underlying assumptions and input data (Bai et al, 2019;Feng et al, 2019;Goroshi et al, 2017;Wang et al, 2018). As shown in a previous study by and in Figure S24 in the Supplementary Material, the basin-averaged evaporation was modeled well and incorporating this flux in the calibration procedure did not improve the modeled long-term storage variabilities.…”

Effect of de-trending climatic parameters on temporal changes of reference evapotranspiration in the eastern Himalayan region of Sikkim, India

“…stated that the decrease in SSH has a positive relationship with the diurnal temperature range (DTR) and evaporation, leading to a reduction in evapotranspiration in Northeast India. Goroshi et al (2017), in a study of evapotranspiration over India, also reported a decreasing trend in ET 0 over northeast India. Patle et al (2019), using sensitivity analysis for Gangtok, East Sikkim, concluded that ET 0 changes positively related to SSH and T factors.…”

“…Significant increasing trends of ET 0 were reported in the Korean Peninsula (Ghafouri-Azar et al 2018), in Iran (Azizzadeh & Javan 2015), in central Europe (Zaninović& Gajic-Čapka 2000), and China (Niu et al 2019). The strong decreasing trend in ET 0 was observed in Canada (Burn & Hesch 2007), in the United States (Golubev et al 2001), in Australia (Donohue et al 2010), in India (Verma et al 2008;Jhajharia et al 2012;Yadav et al 2016;Goroshi et al 2017), and in China (Niu et al 2019).…”