Trends in Indian Rainfall
National Climate Centre Research Report No: 2/2006
Trends in the rainfall pattern over India
P. Guhathakurta and M. Rajeevan
National Climate Centre India Meteorological Department PUNE. INDIA 411005 ncc@imdpune.gov.in
Abstract
Monthly, seasonal and annual rainfall time series of 36 meteorological sub-divisions of India were constructed using a fixed but a large network of about 1476 rain-gauge stations. These rainfall series are thus temporally as well as spatially homogenous. Trend analysis was carried out to examine the long-term trends in rainfall over different sub divisions. Also monthly contributions of each of the monsoon months to annual rainfall in each year were computed and the trend analysis was performed. It has been found that the contribution of June, July and September rainfall to annual rainfall is decreasing for few sub-divisions while contribution of August rainfall is increasing in few other subdivisions.
1
1.
Introduction
In the context of climate change, it is pertinent to ascertain whether the
characteristics of Indian summer monsoon also is changing. The Indian summer monsoon (June to September) rainfall is very crucial for the economic development, disaster management, hydrological planning for the country. Earlier, Mooley and Parthasarathy (1984), Parthasarathy et al. (1993), Parthasarathy et al. (1994), constructed all India rainfall series based on 306 uniformly distributed stations. They have also used area weighted method to calculate all India rainfall using rainfall data of the 306 districts outside the hilly regions like Jammu and Kashmir, Himachal Pradesh, Hills of west Uttar Pradesh, Sikkim and Arunachal Pradesh, Bay Islands and Arabian Sea Island. Presently this time series is updated by the Indian Institute of Tropical Meteorology, Pune (www.tropmet.res.in) and this rainfall time series was extensively used by many researchers. At present there are more than 500 districts in the country. Using
Trends in the rainfall pattern over India
P. Guhathakurta and M. Rajeevan
National Climate Centre India Meteorological Department PUNE. INDIA 411005 ncc@imdpune.gov.in
Abstract
Monthly, seasonal and annual rainfall time series of 36 meteorological sub-divisions of India were constructed using a fixed but a large network of about 1476 rain-gauge stations. These rainfall series are thus temporally as well as spatially homogenous. Trend analysis was carried out to examine the long-term trends in rainfall over different sub divisions. Also monthly contributions of each of the monsoon months to annual rainfall in each year were computed and the trend analysis was performed. It has been found that the contribution of June, July and September rainfall to annual rainfall is decreasing for few sub-divisions while contribution of August rainfall is increasing in few other subdivisions.
1
1.
Introduction
In the context of climate change, it is pertinent to ascertain whether the
characteristics of Indian summer monsoon also is changing. The Indian summer monsoon (June to September) rainfall is very crucial for the economic development, disaster management, hydrological planning for the country. Earlier, Mooley and Parthasarathy (1984), Parthasarathy et al. (1993), Parthasarathy et al. (1994), constructed all India rainfall series based on 306 uniformly distributed stations. They have also used area weighted method to calculate all India rainfall using rainfall data of the 306 districts outside the hilly regions like Jammu and Kashmir, Himachal Pradesh, Hills of west Uttar Pradesh, Sikkim and Arunachal Pradesh, Bay Islands and Arabian Sea Island. Presently this time series is updated by the Indian Institute of Tropical Meteorology, Pune (www.tropmet.res.in) and this rainfall time series was extensively used by many researchers. At present there are more than 500 districts in the country. Using