Abstract
The study of spatiotemporal variation in temperature is vital to assess changes in climate, especially in the Himalayan region, where the livelihoods of billions of people living downstream depends on water coming from the melting of snow and glacier ice. To this end, temperature trend analysis is carried out in the Narayani River basin, a major river basin of Nepal, characterized by three climatic regions: tropical, subtropical and alpine. Temperature data from six stations located within the basin were analyzed. The elevation of these stations ranges from 460 to 3800 m a.s.l. and the time period of available temperature data ranges from 1960–2015. Multiple regression and empirical mode decomposition (EMD) methods were applied to fill in missing data and to detect trends. Annual as well as seasonal trends were analyzed and a Mann–Kendall test was employed to test the statistical significance of detected trends. The results indicate significant cooling trends before 1970s, and warming trends after 1970s in the majority of the stations. The warming trends range from 0.028 to 0.035 °C year−1 with a mean increasing trend of 0.03 °C year−1 after 1971. Seasonal trends show the highest warming trends in the monsoon season, followed by winter and the premonsoon and postmonsoon season. However, the difference in warming rates between different seasons was not significant. An average temperature lapse rate of −0.006 °C m−1 with the steepest value (−0.0064 °C m−1) in the premonsoon season and the least negative (−0.0052 °C m−1) in the winter season was observed for this basin. A comparative analysis of the gap-filled data with freely available global climate dataset show reasonable correlation, thus confirming the suitability of the gap filling methods.
Highlights
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.license.Global warming and climate change are widely recognized as the most significant dilemmas the world is experiencing today [1]
Studies based on direct measurements and remote sensing have suggested that higher greenhouse gases in the atmosphere are causing global climate change [2]
Two meter temperature data of The Narayani River basin were obtained from the Department of Hydrology and Meteorology (DHM), Government of Nepal
Summary
Global warming and climate change are widely recognized as the most significant dilemmas the world is experiencing today [1]. Studies based on direct measurements and remote sensing have suggested that higher greenhouse gases in the atmosphere are causing global climate change [2]. Global temperatures have been rising significantly over the last decade, despite year-to-year fluctuations associated with the El Niño–La Niña cycle of tropical ocean temperature [3]. The widespread retreat of glaciers and snow cover due to increasing temperatures has contributed to eustatic sea level rise [2]. This warming will have significant impacts on the hydrological cycle of mountain river basins, affecting the livelihoods of populations living downstream
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