Analysis on the Spatial Temporal Characteristics of Freezing Rain in Recent Decades
Using EC reanalysis data and the data from observation stations in China, this study analyzes the 53 freezing rain processes which occurred during the period 1978-2002, defines the incidental region and discusses the variability of their spatial temporal features in recent decades. The result shows that the intensity of the freezing rain events these years has a significant decreasing trend, whose break point happened in 1990. Then, two kinds of norms that measure the intensity of freezing rain: the number of stations that experienced the freezing rains and the durations are compared, finding close connections in them. The effects of the two methods used for describing the variability of freezing rain are similar. In addition, through the methods of composite analysis and empirical orthogonal function (EOF), it is revealed that the reverse layer is not only the essential requirement for producing freezing rains, but also acts as an intensity adjustor of the change of freezing rain intensity.