FREQUENCY ANALYSIS OF COMPOUND HEAT AND WET EXTREMES OVER NEPAL

Abstract

Numerous climate-related disasters such as landslides, floods, and droughts affect Nepal and cause large-scale economic losses and negative environmental effects. The susceptibility of the Nation to climate change and its geographic vulnerability exacerbated by extreme weather events poses significant threats to the socioeconomic development of country. Traditionally, extreme events investigation in Nepal is primarily based on univariate analysis. However, occurrence of multiple extreme events become increasingly disastrous, affecting agriculture, food security, and water resources. In this study, for the first time, the observed and climate model simulations are used to analyze compound heat and wet extremes (CHWEs). The changes in the frequency of CHWEs are performed by dividing the observed and model data into two equal halves. The observed data analysis revealed varying trends in heatwaves, extreme precipitation events, and CHWEs in Nepal, with both increases and decreases in different regions, showing mostly increasing CHWEs over the High Himalayas. Different models showed variations in the distributions of heatwaves and wet extremes across Nepal, with some regions experiencing a decrease in heat events. The sensitivity of CHWEs to lag period was evident, with a shift from 15 days to 30 days resulting in a 68% to 79% increase in CHWEs. The findings of this study highlight the complexities of extreme events, with variable trends in heatwaves and extreme precipitation. It emphasizes the increasing occurrences of CHWEs and the need for consideration of compound extremes for effective climate adaptation and mitigation strategies in Nepal.