After unprecedented August rainfall caused devastating floods in Kerala and parts of Karnataka, the National Aeronautics and Space Administration (NASA) has released a video providing an estimate of the intense rainfall using satellite data. The Kerala floods that severely affected 13 of the 14 districts of Kerala claiming nearly 370 people and displacing over a million and leaving a trail of destruction are being called the worst since 1924. The rains that started on August 8 ebbed only earlier this week.
The NASA video shows satellite-based rainfall accumulation from July 19 to August 18, 2018. According to it, rainfall peaked in Kerala on July 20 and again reached abnormally high levels between August 8 and 16.
Since the beginning of June, the weather data shows, the region received 42 per cent more rainfall than normal for this time period. Till August 20, the region had experienced 164 per cent more rain than normal.
Check the video here.
A report on the NASA website, however, points out that release of water from several dams that were brimming over worsened the flooding. “Instead of gradually releasing water during drier times, authorities were forced to open 80 dams in the region, including the Idukki Dam, which is one of the largest arch dams in Asia,” says the report.
As reported before, 35 of those dams were opened for the first time.
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“The dam releases came way too late, and it coincided with the heavy rain that was occurring,” says Sujay Kumar, research scientist at NASA’s Goddard Space Flight Center.
A NASA report says a contributing factor to the heavy rains along the southwest coast of India was the Western Ghats. “Though much smaller than the Himalayas, this mountain range runs parallel to the West Coast of India with many peaks over 2,000 meters (~6,500 feet). As a result, the Western Ghats are well positioned to enhance rainfall along the West Coast of India as they intercept the moisture laden air being drawn in off the warm waters of the northern Indian Ocean and Arabian Sea as part of the southwest monsoon circulation,” says the report.
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According to the report, rainfall accumulations from August 13 to 20 showed two bands of heavy rain across India. “The first band appeared much broader and extends across the northern part of the peninsula with weekly rainfall totals ranging from over 120 mm (~5 inches, in yellow) towards the western half of the peninsula to as much as 350 mm (~14 inches, in dark red) over parts of the eastern half towards the Bay of Bengal,” says the report.
It adds: “The second band was more concentrated, intense and closely aligned with the southwest coast of India and the Western Ghats. Rainfall totals in this band are generally over 250 mm (~10 inches, in red) with embedded areas exceeding 400 mm (~16 inches, in purple). The maximum estimated value from IMERG in this band was 469 mm (~18.5 inches).”
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The NASA video also mentions intense rainfall events that hit other areas of Southeast Asia. Eastern Myanmar experienced torrential downpours in mid-July and August, causing worst floods in 30 years resulting in fatalities and large-scale displacements.
The NASA says these rainfall data are remotely-sensed estimates that come from the Integrated Multi-Satellite Retrievals (IMERG), a product of the Global Precipitation Measurement (GPM) mission.