Research finds a shift in peak time of most rainfall

A examine which examined the spatial rainfall traits throughout India has discovered that the quantity of rainfall per day in sure components of India has elevated over the past decade 2011-2020 in contrast with the earlier decade (2001-2010) whereas sure different components have witnessed a discount within the rainfall quantity. The examine has used the GSMaP-ISRO knowledge to reach at this conclusion. The examine has additionally discovered that the timing of peak rainfall has additionally shifted in several methods throughout sure Indian areas over the past decade (2011-2020) in contrast with the sooner decade (2001-2010).

The examine, which was printed within the Geophysical Analysis Letters on March 17, 2025, used the GSMaP-ISRO knowledge; GSMaP stands for World Satellite tv for pc Mapping of Precipitation. “The GSMaP-ISRO is a precipitation product particularly for the Indian subcontinent which was developed by means of an settlement between ISRO and the Japan Aerospace Exploration Company (JAXA)”. Precipitation knowledge from GSMaP-ISRO can be found from March 2000 onwards and can be found at very high-quality decision of 0.1 x 0.1 diploma latitude/longitude grid with a temporal decision of 1 hour.

The examine discovered that west-central India skilled a slight improve in rainfall over the past decade (2011–2020) in comparison with the earlier decade (2001–2010). The rise in rainfall within the west-central area in the course of the interval 2011-2020 was round 2 mm per day. Moreover the west-central area, the Indo-Gangetic Plain and the southernmost components of the nation had additionally skilled barely elevated rainfall per day. In distinction, the japanese area acquired barely much less rainfall of about 1 mm per day in the course of the interval 2011-2020. The state of affairs was totally different in the course of the earlier decade. From 2001 to 2010, the northeastern and japanese components skilled 1-2 mm extra rainfall per day, whereas southern and central areas confronted a decline. “Although the Indo-Gangetic Plain and the southernmost components of the nation skilled barely extra rainfall per day, it was lower than what the west-central area had acquired,” says Dr. Kandula V. Subrahmanyam from the Nationwide Distant Sensing Middle (NRSC), ISRO, Hyderabad, and the corresponding creator of the paper.

The slight improve in every day rainfall over the west-central area seems to be linked to elevated vegetation. The examine discovered a rise in spatial vegetation cowl over west-central India over the past decade in contrast with the earlier decade. The rise in vegetation cowl over west-central India is mirrored within the improve within the common normalised distinction vegetation index (NDVI) worth from round 0.2 to 0.4. NDVI is used for quantifying vegetation greenness and is beneficial in understanding vegetation density. “The time sequence of NDVI in west‐central India, the place the rainfall is rising, exhibits a big improve in vegetation development over time,” he says. “Elevated vegetation results in elevated transpiration by crops, which releases water vapour into the ambiance. Through the summer season monsoon interval, the evapotranspiration course of occurring due to vegetation performs an important function.”

Together with a rise in vegetation cowl, there was a big improve in soil moisture content material over west‐central India within the current decade (2011-2020) in contrast with the earlier interval (2001-2010), whereas the japanese area confirmed a notable lower throughout the identical interval. Like elevated vegetation, improve in soil moisture content material can be strongly and positively correlated with rainfall.

“One other vital facet uncovered by our examine is the shift within the timing of most precipitation or peak time of most rainfall throughout a 24-hour interval,” Dr. Subrahmanyam says. “Normally, the height time of most rainfall within the Arabian Sea and the Bay of Bengal is within the morning, whereas within the case of inland, the height time of most rainfall is within the afternoon.” The examine discovered that in contrast with the earlier decade, the height time of most rainfall within the Indo-Gangetic Plain has superior by two-four hours, whereas within the west-central area, the height time of most rainfall has delayed by one-two hours.

The prevalence and timing of most rainfall is influenced by the modifications within the quantity of aerosols or aerosol loading. “Within the case of the Indo-Gangetic Plain, aerosol loading is excessive in contrast with the west-central area. Extra aerosol loading results in early peaking of rainfall,” says Dr. Subrahmanyam. Earlier research have proven that in polluted situations, heavy rainfall peaks earlier, and the utmost rainfall peaks roughly six hours earlier in comparison with clear days in Beijing.

 “It is because aerosols soak up and scatter photo voltaic radiation, which leads to heating within the ambiance and cooling on the floor, inflicting modifications in atmospheric vertical static stability and subsequently, modulation of rainfall,” the authors write. Dr. Subrahmanyam says an identical mechanism may need occurred over the Indo-Gangetic Plain. “Larger aerosol loading could also be chargeable for the early peak rainfall over the the Indo-Gangetic Plain, whereas the comparatively decrease aerosol inflicting late peak rainfall over west-central India over the past decade (2011-2020),” he says.