[A-AS22] ミクロスケール気象現象解明にむけた稠密観測・予報の新展開

[AAS22-08] 浅い雲の雲被覆率に対する積雲の広がりと積雲間距離の影響

*佐藤 陽祐¹、西澤 誠也¹、八代 尚¹、宮本 佳明¹、梶川 義幸¹、吉田 龍二¹、山浦 剛¹、富田 浩文¹ (1.理化学研究所計算科学研究機構)

キーワード：ラージ・ディー・シミュレーション, 層積雲, 積雲, 雲被覆率

Shallow cloud cover below sharp inversion is determined by the relationship between two scales. One is the horizontal distance of each cumulus and the other is the horizontal broadening distance of the stratiform clouds at the top of the boundary layer. We indicated it through the numerical experiments of a transition from cumulus under stratocumulus to the shallow cumulus off the west coast of California. The experiments were conducted with an extremely wide domain (i.e. 300 km × 28 km) using a large eddy simulation model with fine grid resolution (i.e. dx = dy = 50m, dz = 5m). The results show that cloud cover is high with large broadening distance of the stratiform clouds and a short distance between each cumulus. In contrast, low cloud cover occurs when the broadening distance is smaller than the distance of each cumulus. The contrast of the two distances is generated by the difference in aerosol the amount and the strength of surface heat flux. The small broadening distance of the stratiform clouds occurs when the surface heat flux (the aerosol amount) is strong (small), and vice versa. The effects of the surface heat flux are larger than that of aerosol amount.
The relationship between two distances can be applied for estimating the cloud cover below the sharp inversion. Hence, it is of help for improving the better expression of shallow clouds in global scale model.