The Freezing Precipitation over the Middle-Lower Reaches of the Yangtze River during February-March 2009

In this paper, the authors analyze the quasistationary fronts, surface conditions, and atmospheric stratification processes associated with a freezing precipitation event over the middle-lower reaches of the Yangtze River, especially in the Dabie mountain during February-March 2009. The long duration of freezing precipitation was primarily caused by stationary and anomalous synoptic weather patterns, such as a blocking high pressure in the northern branch and a trough in the southern branch of the westerlies, which resulted in the encounter cold air from northern China and warm moisture from the south. The east-west-oriented, quasi-stationary front (or shear line) found in central China was mostly responsible for producing the precipitation. The warm layer and near-surface frozen layer were located in the lower troposphere along the front zone. Although the warm layer (> 0 degrees C) existed along the whole front, a surface temperature less than 0 degrees C appeared only over the lower- middle reaches of the Yangtze River, especially in the Dabie mountain. Therefore, the surface temperature was the main influencing factor, as the freezing precipitation only happened over the Dabie mountain.