A examine which examined the spatial rainfall tendencies throughout India has discovered that the quantity of rainfall per day in sure components of India has elevated over the last decade 2011-2020 in contrast with the earlier decade (2001-2010) whereas sure different components have witnessed a discount in the rainfall quantity. The examine has used the GSMaP-ISRO information to reach at this conclusion. The examine has additionally discovered that the timing of peak rainfall has additionally shifted in other ways throughout sure Indian areas over the last decade (2011-2020) in contrast with the sooner decade (2001-2010).
The examine, which was printed in the Geophysical Research Letters on March 17, 2025, used the GSMaP-ISRO information; GSMaP stands for Global Satellite Mapping of Precipitation. “The GSMaP-ISRO is a precipitation product specifically for the Indian subcontinent which was developed through an agreement between ISRO and the Japan Aerospace Exploration Agency (JAXA)”. Precipitation information from GSMaP-ISRO can be found from March 2000 onwards and can be found at very positive decision of 0.1 x 0.1 diploma latitude/longitude grid with a temporal decision of one hour.
The examine discovered that west-central India skilled a slight improve in rainfall over the last decade (2011–2020) in comparison with the earlier decade (2001–2010). The improve in rainfall in the west-central area throughout the interval 2011-2020 was round 2 mm per day. Besides 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 obtained barely much less rainfall of about 1 mm per day throughout the interval 2011-2020. The situation was completely different throughout 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. “Though the Indo-Gangetic Plain and the southernmost parts of the country experienced slightly more rainfall per day, it was less than what the west-central region had received,” says Dr. Kandula V. Subrahmanyam from the National Remote Sensing Center (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 last decade in contrast with the earlier decade. The improve in vegetation cowl over west-central India is mirrored in the rise in 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 series of NDVI in west‐central India, where the rainfall is increasing, shows a significant increase in vegetation growth over time,” he says. “Increased vegetation leads to increased transpiration by plants, which releases water vapour into the atmosphere. During the summer monsoon period, the evapotranspiration process occurring because of vegetation plays a crucial role.”
Along with a rise in vegetation cowl, there was a important improve in soil moisture content material over west‐central India in 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 also be strongly and positively correlated with rainfall.
“Another important aspect uncovered by our study is the shift in the timing of maximum precipitation or peak time of maximum rainfall during a 24-hour period,” Dr. Subrahmanyam says. “In general, the peak time of maximum rainfall in the Arabian Sea and the Bay of Bengal is in the morning, while in the case of inland, the peak time of maximum rainfall is in the afternoon.” The examine discovered that in contrast with the earlier decade, the peak time of maximum rainfall in the Indo-Gangetic Plain has superior by two-four hours, whereas in the west-central area, the peak time of maximum rainfall has delayed by one-two hours.
The prevalence and timing of maximum rainfall is influenced by the modifications in the quantity of aerosols or aerosol loading. “In the case of the Indo-Gangetic Plain, aerosol loading is high compared with the west-central region. More aerosol loading leads to early peaking of rainfall,” says Dr. Subrahmanyam. Previous research have proven that in polluted situations, heavy rainfall peaks earlier, and the maximum rainfall peaks roughly six hours earlier in comparison with clear days in Beijing.
“This is because aerosols absorb and scatter solar radiation, which results in heating in the atmosphere and cooling on the surface, causing changes in atmospheric vertical static stability and subsequently, modulation of rainfall,” the authors write. Dr. Subrahmanyam says a comparable mechanism may need occurred over the Indo-Gangetic Plain. “Higher aerosol loading may be responsible for the early peak rainfall over the the Indo-Gangetic Plain, while the relatively lower aerosol causing late peak rainfall over west-central India during the last decade (2011-2020),” he says.
Published – April 12, 2025 11:00 pm IST
