Detection of heat wave trends in semi-arid climate of Udaipur, Rajasthan.

摘要

The total number of days affected by heat waves was counted for individual months of the year for a period of 33 years (1977-2009) and for individual 3 decades in Udaipur, Rajasthan, India. The annual frequency of the heat waves over the last 3 decades showed an increase of 5 days in the heat waves' affected days. Furthermore, the last decade had a significant increase in the duration of heat waves compared to the earlier 2 decades. The mean annual duration of heat waves in the decade 1977-86 and 1987-96 was 67 and 62, respectively, whereas the last decade (1997-2009) had 70 days. Thus, the annual frequency of the heat waves' affected days had an increasing linear trend. The number of heat waves' affected days was more than 70 in 5 years during 23-year period (1977-99), whereas this happened in 8 of the past decade (2000-09). A time series of annual heat wave index was generated and then trend was detected by applying Mann-Kendal Test. The computed test-statistic value (-0.05) was within its critical value (+or-1.96) in the case of entire 33-year period time series of annual heat wave index and similarly, for earlier 2 decades (1977-86 and 1987-96), indicating that they were free from any trends. However, the computed test-statistic value (2.62) for the last decade (1997-2009) was not within the critical limits. Thus, a significant increasing trend was present in heat wave index series of the last decade at 5% significance level. Tabulated data on the minimum and maximum temperature over 3 decades are provided.