Analyses of Extreme Weather Indices in the Mountain: A Case Study of the Gandaki River Basin, Nepal

Abstract:

This paper provides the analysis of observed temperature and precipitation extremes in Gandaki River Basin, Nepal. Daily maximum and minimum surface air temperature and precipitation data recorded by Department of Hydrology and Meteorology, Government of Nepal were used for this analysis. Temperature data from 5 stations and precipitation data from 20 stations were used based on quality and long term availability of data. Twenty-seven core extreme indices recommended by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI) were calculated using computer software RClimDex. General increasing trend has been observed in the temperature extremes. Most stations show increase in percentage of warm days and nights whereas the cool nights and cool days are found to be decreasing. The trend is of relatively higher magnitude in mountainous region. Changes in indices of precipitation showed mixed pattern and do not show substantial, spatially coherent trends, unlike the situation for temperature means and extremes. The trends of very wet and extremely wet days have been found to be increasing in majority of stations with decreasing in rainy days. Results also show that, all the stations have positive trend of Consecutive Dry Days (CDD) and 60% of the stations show negative trend of Consecutive Wet Days (CWD). Since increase in extreme weather and climate events have greater negative impacts on human society and natural environments than changes in climate means, this study may be useful for policy makers for the development of climate resilient societies.