14:45 〜 15:00
[MIS06-05] Characteristics of precipitation and atmospheric environment during the heavy rain event observed on June 14-16, 2022 in the southern Meghalaya Plateau
キーワード：極端降水、インドモンスーン、夜間降水
The towns of Cherrapunji and Mawsynram, located on the southern slopes of the Meghalaya Plateau in the northeastern part of the Indian subcontinent, are known to have the heaviest rainfall in the world. The Indian Meteorological Department announced that 972 mm of rain was recorded in the 24 hours ending 03 UTC on 17 June 2022. This was the third rain in the last 122 years. Severe flash floods occurred downstream in Sylhet, Bangladesh. Such case studies of heavy rain events must be useful in understanding the mechanism of heavy rain and in considering countermeasures against flash floods.
A Vaisala WXT520 automatic weather station installed at Cherrapunji and an optical disdrometer installed at Sylhet recorded rain for the heavy rain event. The rainfall for the three days from the 14th to the 16th by the impact-type rain sensor was 2412 mm, and 43% of the monthly rainfall in June 2022 was concentrated. Precipitation showed a distinct diurnal variation and increases from midnight to early morning. On the other hand, in Sylhet, which is located in the plains 40 km southeast of Cherrapunji, the precipitation variability was completely different and the diurnal variation of precipitation was unclear.
June is the time of the Indian monsoon onset, and this heavy rain event occurred during the season's progress. Northerly wind of 600-700 hPa in the pre-monsoon season was prominent in the plains south of Cherrapunji until just before this heavy rain event. The environmental field at the time of the heavy rain event was southwesterly below 700 hPa, and northwesterly above. The center of the 200 hPa Tibetan High was located in the northeastern part of the Indian subcontinent. The CAPE was 1500-3500 J/kg and the equilibrium level was reached near the tropopause, while the distance to free convection was 1.5-3.0 km. The area from Bangladesh and Assam state in India was very wet with precipitable water of about 70 mm due to remarkable water vapor convergence due to southwesterly winds from the Bay of Bengal and westerly winds from northern India.
The precipitation system was characterized by the images of Bangladesh Air Force (BAF) C-band radar at Jessore, Bangladesh, 350 km away from Cherrapunji, and the Global Satellite Mapping of Precipitation (GSMaP) product. The precipitation system was a topographical system localized in southern Meghalaya. The precipitation system on the 15th was not sufficiently detected by the BAF radar, suggesting that the echo top height was relatively low. While the GSMaP precipitation distribution showed some agreement with the BAF radar, on the 14th it was not possible to properly detect the onset of the nocturnal rain around 12UTC. This was because the data from the satellite-borne microwave radiometer observations used to create the GSMaP were not available within 3 hours.
A Vaisala WXT520 automatic weather station installed at Cherrapunji and an optical disdrometer installed at Sylhet recorded rain for the heavy rain event. The rainfall for the three days from the 14th to the 16th by the impact-type rain sensor was 2412 mm, and 43% of the monthly rainfall in June 2022 was concentrated. Precipitation showed a distinct diurnal variation and increases from midnight to early morning. On the other hand, in Sylhet, which is located in the plains 40 km southeast of Cherrapunji, the precipitation variability was completely different and the diurnal variation of precipitation was unclear.
June is the time of the Indian monsoon onset, and this heavy rain event occurred during the season's progress. Northerly wind of 600-700 hPa in the pre-monsoon season was prominent in the plains south of Cherrapunji until just before this heavy rain event. The environmental field at the time of the heavy rain event was southwesterly below 700 hPa, and northwesterly above. The center of the 200 hPa Tibetan High was located in the northeastern part of the Indian subcontinent. The CAPE was 1500-3500 J/kg and the equilibrium level was reached near the tropopause, while the distance to free convection was 1.5-3.0 km. The area from Bangladesh and Assam state in India was very wet with precipitable water of about 70 mm due to remarkable water vapor convergence due to southwesterly winds from the Bay of Bengal and westerly winds from northern India.
The precipitation system was characterized by the images of Bangladesh Air Force (BAF) C-band radar at Jessore, Bangladesh, 350 km away from Cherrapunji, and the Global Satellite Mapping of Precipitation (GSMaP) product. The precipitation system was a topographical system localized in southern Meghalaya. The precipitation system on the 15th was not sufficiently detected by the BAF radar, suggesting that the echo top height was relatively low. While the GSMaP precipitation distribution showed some agreement with the BAF radar, on the 14th it was not possible to properly detect the onset of the nocturnal rain around 12UTC. This was because the data from the satellite-borne microwave radiometer observations used to create the GSMaP were not available within 3 hours.