Mountains in the Chaning World, Mountains in the Chaning World

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STATISTICAL ANALYSIS OF LONG-TERM SPATIAL AND TEMPORAL TRENDS IN PRECIPITATION FRON 1951-2014 OF NEPAL
devesh koirala, dibas shrestha, Bikash Nepal

Last modified: 2017-08-31

Abstract


In this study, an investigation has been made to study the spatial and temporal variability of precipitation of Nepal over the period of 64 years (1951-2014) using especial version of APHRODITE NEPAL, having spatial resolution of 5km * 5km on annual, monthly and seasonal basis. Mann-Kendall(MK) test and Cox and Stuart Trend(CST) test were used to detect monotonic trend direction while Sen’s slope estimator were used for magnitude of change over time on annual, monthly and seasonal basis. The Cumulative deviations (Buishand U Test), Standard Normal Homogeinity Test and Pettitt’s test were applied to detect possible change points. Both MK and CST test followed by Sen’s slope estimator shows the presence of significant increasing trend in monthly rainfall for the month of Feb, April and May for all regions ranging from 0.17 mm/yr in High Himalaya (HH) to 1.23 mm/yr in Middle Mountains(MM) at 95% level of significance . Annual precipitation does not show any significant trend neither for Nepal as a whole or any other regions. Seasonal analysis shows significant increasing Pre-monsoon rainfall in all regions (All-Nepal 1.23 mm/yr, High Mountains (HM) 1.13 mm/yr, MM 1.78 mm/yr, and Tarai and Siwalik (TaS) 1.572 mm/yr); while HH shows significant decrease in monsoon precipitation having a slope of -0.87 mm/yr. All three methods of change point detection points that the probable year of change was 1971 for most of the regions.

 

Keywords: Climate Change, APHRODITE, Trend, Change detection, Mann-Kendall test


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