Spatiotemporal variability of rainfall erosivity and its teleconnection with atmospheric circulation in monsoon-driven climate region

Abstract

Understanding the spatiotemporal variability of annual, monthly, and seasonal rainfall erosivity (RE) is crucial for determining the risk of soil erosion and developing soil conservation plans. However, little knowledge is available on RE at the monthly, seasonal, and annual scales in monsoon-driven climate regions like Bangladesh. Therefore, we aimed to assess the spatiotemporal variability of RE in Bangladesh from 1980 to 2017 and analyze teleconnection of RE with large-scale atmospheric circulation indices. The detrended fluctuation analysis (DFA) and cross wavelet analysis were employed to evaluate the potential future trends and interpret the periodic cycles in the RE, respectively. The results demonstrate that mean annual RE values fluctuated from 12574.16 MJ.mm.ha-1.h-1 to 123914.76 MJ.mm.ha-1.h-1, while RE has been lower in recent decades than in the earlier decades. The mean annual RE is decreasing all over the country, and significant abrupt change points occurred in the early 2000 s. The highest mean annual RE was observed in the southernmost part of Bangladesh and the lowest in the western part of the country. The results of DFA indicated that the RE trend would sustain its present trend in the upcoming period, except for May and July. The effects of Niño3.4 SST and IOD, SASMI, and EASMI have almost no to minimal influence on the RE trend in Bangladesh. However, a noticeable impact was found on the monthly scale, which could be why the observed intra-annual variability of RE was observed. We found that the average RE has reduced significantly with increasing distance from the sea, latitude, and elevation in Bangladesh. The study found that increasing geopotential height in the summer and decreasing geopotential height in the winter with enough moisture divergence, decreasing convective precipitation, decreasing large-scale rain rate, decreasing specific cloud liquid water content, and decreasing explicit rainwater content all contributed to RE variability and change in the country.