[A-CG30] Extratropical oceans and atmosphere

[ACG30-P22] Reproducibility and forecast skill of low clouds southeast off Hokkaido in summer with the Japan Meteorological Agency Meso-Scale Model

*Shion Sekizawa¹, Satoru Okajima¹, Ayumu Miyamoto², Takafumi Miyasaka¹, Morio Nakayama¹, Hisashi Nakamura¹ (1.Research Center for Advanced Science and Technology, University of Tokyo, 2.Scripps Institution of Oceanography, University of California)

In July 2022, aircraft-ship simultaneous observations of low clouds were conducted southeast off Hokkaido, Japan, supported by a research project, "Midlatitude ocean-atmosphere interaction hotspots under the changing climate." We provided the observation team with weather information based on forecasts by Japan Meteorological Agency Meso-scale model (MSM) during the observations. In this study, motivated by this observation support, we verify the reproducibility and forecast skill of summertime low clouds southeast off Hokkaido in MSM.
The low-cloud cover forecasted from the previous day corresponds quite well with that diagnosed at the analysis in MSM, showing apparent high forecast skill. However, when compared with the low-cloud cover in MODIS satellite observation products, there are large bias and variance between the model and satellite observation. These bias and variance are evaluated in relation to surface wind direction and temperature advection. We find that MSM tends to underestimate the low clouds in northerly-easterly wind (cold advection) situations, and have large variance from the satellite observation in southerly-westerly wind (warm advection) situations.