Evolutionary characteristics of the atmospheric circulations for frequent and infrequent dust storm springs in northern China and the detection of potential future seasonal forecast signals

The evolutionary characteristics of dust storms Ill spring in northern Chilli( springs tire determined by synthesizing the previous patterns and analyzing the geopotential height at 500 hPa Some potential seasonal predictors are found through detecting the atmospheric circulation factors in both qualitative and (quantitative analyses Based oil the frequency series obtained through comprehensive investigations of dust storm events Which occurred from 1970 to 2005. two sample sets, each containing 6 years. are. selected to represent the most frequent and infrequent occurrences of spring dust storms For the first set. most of the West Pacific Subtropical highs in the previous summer are relatively small and weak compared to those in normal year, In the previous winter. the mid-latitude legion of the Eurasian continent is strongly controlled by a large and active low system, simultaneously with a strong and westerly positioned trough over East Asia The northern hemisphere polar vortex, in general, changes from weak to strong with a large area from the previous winter to the current spring The geopotential height over the Tibetan Plateau keeps a lower than normal value with a relatively strong India-Burma trough from the preceding summer in to the spring. For the second set, the evolution displays opposite features. Furthermore, by using a bootstrapping technique, indices of the atmospheric circulation elements are detected quantitatively The forecast skill Score of the 36 year hindcast (1970-2005) Indicates that those indices call provide forecast signals in certain situations for spring dolt storm seasonal predictions in northern China Copyright (C) 2009 Royal Meteorological Society