9:30 AM - 9:45 AM
[ACG47-03] Comparison of the aircraft observation for vertical profiles of water vapor
Keywords:Aircraft observation, Dropsonde, Water vapor distribution, Quantitative precipitation forecasting (QPF)
To perform quantitative precipitation forecasting (QPF), it is necessary to observe water vapor distribution on the windward side accurately. However, it is difficult to observe it in Japan, because Japan is surrounded by the ocean and has quite less ground-based sounding observation points over the ocean. The dropsonde observation using an aircraft is useful to capture vertical profiles of water vapor over the ocean.
We carried out dropsonde observations using a jet aircraft (Gulfstream-IV: G-IV) of Diamond Air Service Inc. to capture the distributions of water vapor over the Pacific Ocean and East China Sea on July 5, 2022. On that day, Typhoon Aere (T2204) struck Kyushu and passed along the southern coast of Shikoku Island. Numerical simulations showed a large amount of water vapor intrusion in the eastern side of the typhoon and heavy rainfall around the southern coast of the Japanese Islands.
Outward flight in the morning was carried out from Nagoya to Shimojishima Airport (Okinawa Prefecture), and homeward one in the afternoon was reversal. The G-IV flew at a speed of 450 knots (833 km/h) at a height of 45,000 ft (13.7 km). Dropsonde observations were conducted every 5 min (approximately 70 km resolution) except for restricted observation regions, and obtained temperature, relative humidity, wind direction and speed at each altitude (pressure level) at every 1 sec.
Detailed distance-height water vapor distributions are captured by dropsonde observations, those are not uniform in horizontal directions. Several vapor profiles obtained by dropsoundes around Amami Island are a little drier (1~2 g/kg) than that by upper-air sounding at Naze in the lower troposphere. This difference seems to be quite crucial to the accuracy of the QPF. A Highly humid area that is consistent with the numerical weather forecasting, is observed to the south of the Kii Peninsula. The moist area may affect a heavy rainfall event at Hachijo Island (over 200 mm rainfall in 12 hours) in the midnight from July 5 to 6. An Area of relatively lower humidity with northerly or westerly wind is captured in the middle troposphere over the East China Sea. This feature may correspond the dry intrusion of the western side of the low pressure system (T2204 Aere).
We carried out dropsonde observations using a jet aircraft (Gulfstream-IV: G-IV) of Diamond Air Service Inc. to capture the distributions of water vapor over the Pacific Ocean and East China Sea on July 5, 2022. On that day, Typhoon Aere (T2204) struck Kyushu and passed along the southern coast of Shikoku Island. Numerical simulations showed a large amount of water vapor intrusion in the eastern side of the typhoon and heavy rainfall around the southern coast of the Japanese Islands.
Outward flight in the morning was carried out from Nagoya to Shimojishima Airport (Okinawa Prefecture), and homeward one in the afternoon was reversal. The G-IV flew at a speed of 450 knots (833 km/h) at a height of 45,000 ft (13.7 km). Dropsonde observations were conducted every 5 min (approximately 70 km resolution) except for restricted observation regions, and obtained temperature, relative humidity, wind direction and speed at each altitude (pressure level) at every 1 sec.
Detailed distance-height water vapor distributions are captured by dropsonde observations, those are not uniform in horizontal directions. Several vapor profiles obtained by dropsoundes around Amami Island are a little drier (1~2 g/kg) than that by upper-air sounding at Naze in the lower troposphere. This difference seems to be quite crucial to the accuracy of the QPF. A Highly humid area that is consistent with the numerical weather forecasting, is observed to the south of the Kii Peninsula. The moist area may affect a heavy rainfall event at Hachijo Island (over 200 mm rainfall in 12 hours) in the midnight from July 5 to 6. An Area of relatively lower humidity with northerly or westerly wind is captured in the middle troposphere over the East China Sea. This feature may correspond the dry intrusion of the western side of the low pressure system (T2204 Aere).