GUWAHATI, Sept 3 – Is the frequency of heavy rainfall days in Assam diminishing? This question is dominating the minds of the environmental scientists here for the past several years considering the phenomenon of climate change. But a conclusive answer to it is still elusive.

Sources in the Regional Meteorological Centre (RMC) here said no significant trend of increase or decrease in the frequency of heavy rainfall days is observed in the State during the past 50 years, particularly during the monsoon season. In matters of persistence of rainy days too, no significant change is observed during the past 50 years in Assam.

However, variability in rainfall pattern has increased specially during the current monsoon season in the NE region. But the factors responsible for this development remain to be convincingly determined. In matters of thunderstorm and squall activities over Guwahati during the pre-monsoon season, sources said no significant change is observed since 1981.

It is believed that rapid urbanization may have some impacts on rainfall variability over Guwahati, sources said.

During this monsoon season, normal rainfall activities have been observed over Assam, Arunachal Pradesh and Tripura till August 30 last. Arunachal Pradesh received (+) 1 per cent, Assam received (+) 1 per cent and Tripura received (-)14 per cent of rainfall during the period between June 1 and August 30.

The four NE states of Manipur (-76 per cent), Meghalaya (-20 per cent), Mizoram (-26 per cent) and Nagaland (-40 per cent) received deficit rainfall during this period.

Out of the 27 districts of Assam, 22 districts received excess or normal rainfall, while the five districts of Darrang (-50 per cent), Dhemaji (-21 per cent), Hailakandi (-37 per cent), Morigaon (-22 per cent) and Nagaon (-32 per cent) recorded deficit rainfall during this period.

Meanwhile, long strides have been made by the India Meteorology Department (IMD) in modernizing its services in NE region. A Doppler Weather Radar (DWR) system has already been commissioned in Agartala, while the DWR in Dibrugarh is operational and the site for the DWR in Guwahati has already been finalised, sources said.