关键词: 大雾, 环流形势, 物理量场, 分析

Abstract:

The consecutive heavy fog occurred in most areas of Hebei Province from December 31, 2006 to January 5, 2007,was analyzed based on upper and low level circulation patterns, physical quantities and meteorological element fields, etc. The results show that the heavy fog occurred under the atmospheric circulation pattern controlled by the straightwesterly air flow at 500 hPa middle latitudes, northwesterly air flow orweak high p ressure circulation atmiddle and low levels, and weak p ressure in front of the surface high.Visible snow occurred before the heavy fog, and snow melting rap idly increased the humidity near the surface. During the fog, significant night radiation caused the temperature inversion near the surface. Water vapor accumulated near the surface and was saturated due to surface evaporation and radiation cooling. Amp le water vapor and obvious saturation near the surface were the important causes of the consecutive heavy fog. A weak stability near the surface and stability in middle and upper levels p resented during this fog event.

Key words: fog, circulation pattern, physical quantity field, cause