| Various satellite data,observation data and reanalyzed data are used to investigate the formation reason of cold SST patch in Summer over Yellow Sea. The Effect of Cold SST on Summer Atmosphere Boundary Layer and Sea Fog over Yellow Sea is researched simultaneously. Finally, this phenomenon is simulated using WRF (Weather Research Forecast) model.Sea surface temperature (SST) is a variable between sea and atmosphere. It is affected by ocean tide and ocean bottom topography etc.. SST has an impact on marine atmosphere boundary layer (MABL). NOAA OI SST uses Advanced Very High Resolution Radiometer (AVHRR) and Advanced Microwave Scanning Radiometer (AMSR) satellite SST data. And situ data from ships and buoys is assimilated in it. Using this data, we find SST over Yellow Sea has significant seasonal variation. Cold SST band is an important oceanography phenomenon over this sea in summer. In the Yellow Sea, rich structures in summer SST with extraordinarily cold patches on the west of Korean Peninsula , the peak of Liao Dong Peninsula and Shan Dong Peninsula, the southern of Shan Dong Peninsula, off the coast of Jiangsu and southern of Yellow Sea are generated. The present study focuses on the latest two SST cold patches. Continental shelf fronts upwelling causes strong vertical mixing in the upper ocean is the formation reason of these patches. The SST clod patches have significant inter-annual variations.As the underling surface of MABL, the SST cold patches must have impact on MBAL, further affect sea fog which is one of most important phenomena of the weather in MABL. Based on QuikSCAT sea surface wind data, we find the surface southerly wind clearly slows down over the cold patches. At the same time, SAT-SST is very positive in CFSR reanalyzed data. This indicates the cold patches cool air temperature, stabilize the near-surface atmosphere and decelerate surface wind through suppressed vertical mixing. This hypothesis can be verificated using WRF model's simulation.Our analysis of ship-board observations reveals frequent sea-fog occurrence over the cold patches with a maximum exceeding 15% on southern of Yellow Sea in June. This is the same as result fog frequency based on Modis satellite data. Numerical simulations with the Weather Research and Forecasting (WRF) model support that the cold patches cool air temperature, decelerate surface wind, and form a strong surface inversion layer up to 400m high, creating favorable conditions for sea-fog occurrence. The WRF simulation without the cold patches'cooling effect reduces sea-fog occurrence by more than 15% over cold patches. Our simulations indicate clod patches enhance sea fog occurrence through cooling air temperature, increasing condensation of water vapor; suppress low cloud occurrence due to warming from long wave radiation of fog. The huge warm temperature advections over cold patches compensate for the lost heat because of long wave radiation, and maintain inversion. The effect of cold patches can reach 900m height.To choose a suitable specification of WRF parameterizations, two groups of sensitive experiments are carried out. Finally, we select MYNN2 PBL scheme and WSM5 microphysics scheme to use in the simulation. |
