Variations in the Lower Level of the PBL Associated with the Yellow Sea Fog-New Observations by L-Band Radar

The Chinese east coastal areas and marginal seas are foggy regions. The development of effective forecasting methods rests upon a comprehensive knowledge of the fog phenomena. This study provides new observations associated with the sea togs over the northwestern Yellow Sea by means of L-band radar soundings with a high vertical resolution of 30m. The monthly tem- perature lapse rate, the Richardson Nulnbers, and the humidity show obvious seasonal variations in the lower level of the planetary boundary layer （PBL） that are related to the onset, peak and end of the Yellow Sea fog season. The typical pattern of stratification for the sea fog season in the northwestern Yellow Sea is that a stable layer of about 400 m thick caps a 150 m conditionally unstable layer Besides, the differences between togs and stratus clouds in terms of humidity, turbulence and temperature are analyzed, which is of significance for sea fog forecast and detection by satellites. The thickness of the sea fogs varies in different stages of the fog season, and is associated with the temperature inversion. The numerical simulation proves that the seasonal variations obtained by the radar well represent the situations over the Yellow Sea.

The Chinese east coastal areas and marginal seas are foggy regions. The development of effective forecasting methods rests upon a comprehensive knowledge of the fog phenomena. This study provides new observations associated with the sea fogs over the northwestern Yellow Sea by means of L-band radar soundings with a high vertical resolution of 30 m. The monthly temperature lapse rate, the Richardson Numbers, and the humidity show obvious seasonal variations in the lower level of the planetary boundary layer (PBL) that are related to the onset, peak and end of the Yellow Sea fog season. The typical pattern of stratification for the sea fog season in the northwestern Yellow Sea is that a stable layer of about 400 m thick caps a 150 m conditionally unstable layer. Besides, the differences between fogs and stratus clouds in terms of humidity, turbulence and temperature are analyzed, which is of significance for sea fog forecast and detection by satellites. The thickness of the sea fogs varies in different stages of the fog season, and is associated with the temperature inversion. The numerical simulation proves that the seasonal variations obtained by the radar well represent the situations over the Yellow Sea.