Abstract
Trends in 20 extreme indices of temperature and precipitation are examined for Sri Lanka using high-quality datasets for 19 meteorological stations, for a period between 1980 and 2015. It is evident that annually averaged mean minimum temperatures are increasing across most of Sri Lanka. The difference between maximum and minimum temperatures, diurnal temperature range is decreasing, indicating that the minimum temperature is increasing faster than the maximum temperature. Significant decrease in the annual occurrence of cold nights and increase in the annual occurrence of warm nights are also obvious. When compared with temperature changes, less spatially coherent pattern of change and a lower level of statistical significance were observed in precipitation indices. The annual total precipitation (PRCPTOT) has indicated a significant increasing over 1980-2015. More than 80% of stations showed an increasing trend in precipitation indices. The trends in extreme precipitation events such as maximum one-day precipitation, maximum five-day precipitation, and total precipitation on extreme rainfall days (R95p and R99p) are increasing at most locations, indicating that the intensity of the rainfall is increasing. Increase of precipitation extreme trends indicates that occurrence of extreme rainfall events notably influences total annual precipitation in Sri Lanka. Therefore, the observed increases in total rainfall observed in many locations may be due in part to an increase in of extreme rainfall events. Patterns of change in precipitation extremes are more heavily influencing the climate variability by aggravating the variability, significantly influencing climate sensitive sectors such as agriculture and water resource management.
Highlights
When compared with temperature changes, less spatially coherent pattern of change and a lower level of statistical significance were observed in precipitation indices
The observed increases in total rainfall observed in many locations may be due in part to an increase in of extreme rainfall events
Precipitation and temperature indices developed by the World Meteorological Organization–Commission for Climatology (WMO–CCI)/World Climate Research Program (WCRP)/Climate Variability and Predictability (CLIVAR) project’s Expert Team on Climate Change Detection and Indices (ETCCDI) (Easterling et al [22], Alexander et al [2]) were calculated using daily precipitation, daily maximum temperature and daily Minimum temperature data, from 19 surface weather stations (Figure 1 and Table 1) of the Department of Meteorology, Sri Lanka covering the period 1980-2015
Summary
Using a high resolution daily gridded rainfall data set, Goswami et al [14] showed that there are significant rising trends in the frequency and the magnitude of extreme rain events over central India during the monsoon season. Using 104 years (1901-2004) of high resolution daily gridded rainfall data over central India, Rajeevan et al [15] found that the frequency of extreme rainfall events shows significant inter-annual and inter-decadal variations. Most of the previous studies of observed changes in temperature and precipitation extremes in Sri Lanka were used historical data only up to year 2000 (Malmgren et al [20]; Jayawardena et al [21] and Sheikh et al [13]).
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