Observations of Rainfall in Garhwal Himalaya, India during 2008-2013 and its Correlation with TRMM Data

Rainfall variations in the Garhwal Himalaya, Uttarakhand were studied for a period of six years from 2008 to 2013. The rainfall data were obtained through a dense network of rain gauges installed by India Meteorological Department (IMD), New Delhi, are spreaded over seven districts of Uttarakhand, combined with the data from Wadia Institute of Himalayan Geology (WIHG) rain gauge located at Ghuttu, Garhwal Himalaya. The rainfall data of WIHG have a sampling interval of 15 min, while IMD provides district- wise rainfall measurements with monthly temporal resolution. Therefore, extreme events of rainfall which occurred in a short duration of time were observed using the rainfall data of WIHG. Similarly, daily diurnal variations of rainfall were also observed in these data. The seasonal variations and distribution of rainfall in different districts of the Garhwal region were seen in both WIHG and IMD datasets. An increasing trend of rainfall activity was seen from 2008 to 2013. Meterological observations suggest that the isohyet has shifted towards end-September in recent years. Two events of extreme rainfall in the Garhwal Himalaya in 2012 and 2013 caused a major loss of life and property in the region. The rain gauge of WIHG recorded heavy rainfall during both the events. In 2012, ~70 mm rainfall was recorded in 1 h and in 2013 the rain gauge data showed about 250 mm rainfall in 52 h. The daily diurnal records of rainfall show a minimum between 0700 and 1300 h local time (local time = UT + 5.30 h) and diurnal maximum between 2200 and 0300 h local time for all the years. The seasonal variation of rainfall reveals that the peak season of monsoon ranges from June to September in the Garhwal region, which contributes about 50-90% to the annual rainfall. We also compared the observed results of rain gauges with TRMM-derived rainfall data and found a good correlation ranging from 0.6 to 0.9.