Polarimetric radar observation for early developing stage of cumulonimbus clouds

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03742
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: National Research Institute for Earth Science and Disaster Prevention
• Principal Investigator: Ohigashi Tadayasu 国立研究開発法人防災科学技術研究所, 水・土砂防災研究部門, 主幹研究員 (80464155)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 積乱雲 / 雲レーダー / 偏波レーダー / 雲発生 / 晴天エコー

Outline of Final Research Achievements

The development process of cumulonimbus clouds causing heavy rainfall from among numerous cumulus clouds in summer is not well understood. Therefore, we conducted observations of the generation and early development stage of cumulonimbus using polarimetric cloud radars, which can observe the three-dimensional distribution of clouds. After developing a method to distinguish cloud/precipitation echoes from clear-air echoes, we compared two echo areas with different degrees of development that occurred at approximately the same time and location. The developed echo area had a larger number of internal echo maxima and a larger horizontal scale from the early stage of development. It was inferred that the larger horizontal scale prevented mixing with the outside of clouds, and thus development was less likely to be inhibited.

Free Research Field

気象学

Academic Significance and Societal Importance of the Research Achievements

夏季に強雨をもたらす積乱雲の発生場所・時間を前もって予測することは難しい。本研究では夏季に数多く発生する積雲の中から強雨をもたらす積乱雲に発達する一つの過程が明らかにされた。このことは、発達する雲と発達しない雲の違いを明らかにし、強雨の直前予測に寄与することが期待できる。また、レーダーの偏波機能を利用して、目的としない晴天エコー域を識別し、晴天エコーと雲・降水エコーが混在する中から目的とする雲・降水エコーを抽出する方法を示した。