GUWAHATI, Sept 30 – The arrival of the pearly dewdrops in the urban landscape here may be delayed until the summer season gets debilitated in its pre-withdrawal syndrome or it withdraws altogether. Dew is in fact a condensed form of water vapour. According to meteorologists, water vapour condenses into dewdrops depending on the surface temperature. The temperature at which dewdrops form is called the dew point. Dew point is the temperature to which air must be cooled to become saturated with water vapour. When surface temperature drops and finally reaches the dew point, the atmospheric water vapour condenses to form small dewdrops on the surface. Environmental scientists here are of the opinion that summer is getting itself lengthened under the impact of climate change, while urbanisation and rapid loss of virgin forests have been keeping the atmosphere hot.
Environmental scientists and meteorologists here add one more factor for the absence of dewdrops in the urban locales here so far. They opine that usually, the ambient weather conditions during the Durga Puja festival add to the formation of dewdrops. But this time around, the Puja festival was scheduled a little before the usual time.
Professor and Head of the Department of Environmental Science, Gauhati University, Sarbeswar Kalita told this correspondent that under the impact of climate change, extreme weather conditions are occurring frequently in this part of the globe too.
For example, he said thunderstorms are not an usual phenomenon during this season in the NE region. But they have occurred here on several occasions during this part of the year. Again, the sky is still cloudy here. This is keeping the surface warm. Dewdrops also require a clear sky for their formation. Moreover, urbanisation and rapid loss of virgin forests have been stepping up surface temperature here. RCC structures capture solar heat during the daytime and radiate it during night. They behave in a contrary manner in the winter. All these factors facilitate extreme weather conditions, said Prof Kalita.
Meteorologists here maintain that in the urban areas of the plains districts of the State, water vapour usually takes the shape of dewdrops when it gets condensed under a below-15 degree Celsius average surface temperature. But for the formation of the dewdrops under the impact of such a surface temperature, the relative humidity in the atmosphere should be above 65 per cent, add the meteorologists.
Source : http://assamtribune.com