Heat and Cold Waves
The analysis on heat and cold waves has been made based on daily temperature data of 103 stations for the period 1961-2010.
- 1. During the hot weather season (April-May-June), heat waves are experienced over the north, northwest, central, east India and northeast peninsula. Similarly, during the cold weather season (December-January-February), northern parts of the country including Jammu and Kashmir experience cold waves.
- 2. Significant decadal variation is observed in the frequency, spatial coverage and area of maximum frequency both in heat wave and cold wave.
- 3. Noticeable increase (decrease) in frequency of heat wave days is observed during the El Nino (La Nina) events. Exactly opposite association was observed in case of CW days.
- 4. Significant increasing (decreasing) trends in heat waves (cold waves) are observed during the hot (cold) weather season over most parts of the country.
The analysis on meteorological droughts is made using monthly rainfall data of the period 1901-2010 based on the Standardized Precipitation Index and Standard Precipitation Evapotranspiration Index (SPEI).
- 1. The all-India droughts are observed almost once in five years. More intense droughts are mainly observed over north and northwest India.
- 2. There is a significant increasing trend in the intensity and areal coverage of moderate droughts of various accumulated periods over India during the recent years, since 1950s. This increase could be also linked to warming of the equatorial Indian Ocean.