Analysis of Heat Wave over Nepal
Date
2022
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Hydrology and Meteorology
Abstract
Climate change imposed negative impact on socio-economic sectors of the
mountainous region like Nepal. The 21
st
century has brought many records breaking
warm year. Such warm periods brought many health-related problems, heat wave is one
among them. Daily maximum temperature data of 46 stations of DHM is used to
calculate the heat wave (HW)patterns over the country. To better understand the
regional pattern of HW all the stations are further classified into 6 different regions:
East Terai, Central Terai, Western Terai, Eastern Mountain, Central Mountain and
Western Mountain based on the 3 large river basins (Koshi, Gandaki and Karnali). The
percentile-based method is used for the calculation of the HW. The 90
th
percentile
values are used as the threshold and HW is declared after the daily maximum
temperature on exceeding the threshold and the normal temperature of the station by 4°
C for at least 3 consecutive days. Based on the criteria, HW’s different characteristics
like the total number of events, total days of HW, longest event, average days in HW,
Maximum deviation of temperature in HW, the onset date of HW and the withdrawal
date of HW are calculated using MATLAB and MS-Excel. The western region records
the highest frequency and total heat wave days. The central and western mountain
region shows the highest maximum temperature deviation than the Terai regions.
Although the HW events are more severe in the mountain region but terai region shows
consistent severe HW in these regions. The average days of heat wave event throughout
the country is 2.6 days. Also, the monsoon event controls the heat wave events. The
ElNino phenomena shows no significant relation with the heat wave but the peak of the
heat wave is found at ElNino+1 year. The criteria used in this study is very easy to
calculate and can be used for the national decision-making process.
Description
Keywords
Heat wave, Climate change