Improvement in simulated diurnal variation of precipitation and impact of the diurnal cycle on development of precipitation disturbances

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K12975
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geography
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Adachi Sachiho 国立研究開発法人理化学研究所, 計算科学研究センター, 研究員 (50512448)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 降水日変化 / 領域モデル / 局地循環 / 日射影響

Outline of Final Research Achievements

In this study, a quantitative evaluation of the effect of solar radiation on precipitation activity was conducted using a numerical model. First, to see the effect of solar radiation on precipitation, sensitivity experiments with and without solar radiation were conducted. The results showed that solar radiation increases precipitation by a factor of 1.5 compared to the case without solar radiation. Next, we investigated the effect of different amounts of solar radiation. The results showed that precipitation increases at sea and decreases on land under conditions of weak solar radiation. On the other hand, under conditions of strong solar radiation, precipitation decreased at sea and increased on land. The reason for this is that there is no simple linear relationship between the amount of solar radiation and the effect of solar radiation on precipitation, but rather feedback between the two effects of solar radiation: to increase convection and to strengthen local circulation.

Free Research Field

気候学

Academic Significance and Societal Importance of the Research Achievements

近年、豪雨に伴う水害や土砂災害が毎年のように発生している。「夜に集中豪雨は起こりやすいのか？」という疑問はしばしば話題となるが、これは、単に同規模の降水イベントが発生した場合に、夜間の方が危険リスクが高いことに由来するためか、それとも実際に雲の発達メカニズムが昼夜で異なるためか、明確な答えは今のところ存在しない。近年頻発している災害から身を守り、リスクを軽減するためにも、後者の視点から、日射の降水への影響について学術的に明らかにしておくことは重要である。本課題を継続・発展させることで、最初の問いに答えることが可能となり、大雨の予測精度向上や災害時のリスク軽減にもつながるものと期待される。