Permalink : http://hdl.handle.net/2115/55022

2009年の春季東シナ海・黄海の下層雲を対象とした航空機観測 A-FORCE-2009 において, 雲底下のエアロゾル数濃度とその直上の雲微物理量の観測を７フライト（９ケース）で実施した. この観測からエアロゾル数濃度と雲粒数濃度に正相関があることを示した. さらに雲粒数濃度は大気最下層の鉛直安定度の指標（海表面温度 SST と 950hPa　気温の差）とも正相関があった. これは大気不安程度の増加により対流中の上昇流速度が増加し, より多くの雲粒が生成する可能性を示している. 冬季・春季の大陸からの北西季節風が高濃度エアロゾルを輸送するとともに, 寒気移流により SST が高い黒潮上において効果的に雲粒数濃度を増大させていることを初めて明らかとした.
Cloud microphysical properties and aerosol concentrations were measured aboard an aircraft over the East China Sea and Yellow Sea in April 2009 during the A-FORCE-2009 experiment. We sampled stratocumulus and shallow cumulus clouds over the ocean in 9 cases during 7 flights 500-900 km off the east coast of Mainland China. We show that the cloud droplet number concentration (highest 5%,Nc_max) correlates well with the accumulationmode aerosol number concentration (Na) below the clouds. We then show that Nc_max correlates partly with near-surface stratification evaluated as the difference between the sea surface temperature (SST) and 950-hPa temperature (SST－ T950). Cold air advection from China to the East China Sea was found to bring not only a large number of aerosols but also a dry and cold air mass that destabilized the atmospheric boundary layer, especially over the warm Kuroshio ocean current. Over this high-SST region, greater updraft velocities and hence greater Nc_max likely resulted. We hypothesize that the low-level static stability determined by SST and regional-scale airflow modulates both the cloud microphysics (aerosol impact on clouds) and macro-structure of clouds (cloud base and top altitudes, hence cloud liquid water path).