Statistical quantification of the local daily surface meteorological condition's impact properties on dust storm occurrence: style, intensity, significance, contribution, and decisiveness, taking North and Northwest China as an example

摘要

The local surface meteorological condition (SMC) is decisive for dust storm (DS) occurrence (DSO), and SMC's impact properties on DSO, such as its impact style, intensity and significance on, its contribution to and decisiveness for DSO, and so on, are expected to help deepen knowledge of SMC's impact mechanism on DSO so as to improve the DS prediction. This paper has selected 23 SMC factors and assumed they can wholly quantify SMC; so and SMC's impact properties on DSO can be well reflected by each SMC factor or factor group's, and the latter can be decided according to the DSO possibility's (DSOP's) variations with the factor or group. Based on all SMC factors' daily datasets together with DS records during 1970-2007 at 139 weather stations within North and Northwest China (NNWC), who encounters the dust storm most frequently and has widely and densely covered weather stations, this paper has put forward a set of universal statistical techniques to respectively quantify DSOP under a certain SMC, a certain SMC factor's impact style on DSO, and a certain SMC factor or factor group's impact intensity and significance on and its contribution to and decisiveness for DSO. After quantifying SMC's impact properties on DSO, their factor-to-factor, i.e., factorial, and station-to-station, i.e., spatial, variations within NNWC have been specially analyzed on in detail, resulting in some interesting conclusions: (1) generally, if one SMC factor rises (drops) from the NDS to DS day and it is positively (negatively) correlated to the DS frequentness (DSF), then it will usually impact on DSO positively (negatively), i.e., that factor's increase can usually raise (reduce) DSOP; The wind speed and evaporation (relative humidity and vapor pressure) impact on DSO positively (negatively) at all or almost all stations within NNWC, however, other factors impact positively here but negatively there. (2) The SMC factor or factor group's correlation degree to DSF and its sensitivity to DSO can somewhat decide its impact intensity and significance on and its contribution to and thus decisiveness for DSO: the more sensitive to DSO and the more highly correlated to DSF the factor or group, the more intensively, significantly, contributively, and thus decisively it impacts on DSO. (3) Of all factors, the wind speed has proved to impact on DSO much more intensively, significantly, contributively and thus decisively at all stations within NNWC, and SMC seems to impact on DSO almost wholly by modifying the wind speed. (4) Using the cluster technique onto SMC's impact properties on DSO, all stations within NNWC have been classified into 7 clusters, who can well display the regionality of SMC's impact mechanism on DSO.