Pre-monsoon in Asia produces more precipitation, lightning

Tokyo The pre-monsoon season in Asia produces more intense precipitation and lightning, finds a study based on new satellite data potentially informing better weather prediction.

As adverse rainfall events rock the world, scientists are trying to understand the mechanism behind precipitation based on finer details than simply “how much” it rained.

Scientists led by doctors Moeka Yamaji and Hiroshi Takahashi from the Tokyo Metropolitan University in Japan and other institutes studied new satellite data showing the diameter of rain droplets and the distribution of heavy ice in the atmosphere worldwide.

They focused on the Asian monsoon region, finding larger droplets and more heavy ice precipitation on land before the actual monsoon season.

A previous study by the same team showed that the pre-monsoon season on land in Asia actually saw significantly heavier rainfall than the monsoon region, that is, there was less rainfall in total, but the rain that did fall fell in stronger outbursts.

In the new study, published in the Journal of the Atmospheric Sciences, they shifted their attention to finer properties. They now showed that rain droplets over land during the pre-monsoon season were larger, and there was an elevated amount of heavy ice precipitation.

This agreed well with seasonal changes in "top heights", the altitude at which precipitation originates.

Importantly, their analysis revealed that the correlation between the amount of rainfall and the size of droplets was not simple. Periods were found with similar total rainfall but different droplet diameters, showing how important it is to recognise different precipitation characteristics.