A Study On Circumfluence, Dynamic Factor And The Remote Correlation With North Pacific Ocean SST Of Spring Sandstorm In Ningxia

Using observation of spring sandstorm in Ningxia, North Pacific ocean SST, NCEP reanalyzed data, indices of circumfluence and the data of sonde in Yinchuan, a study on the basic law of spring sandstorm in Ningxia, and its circumfluence, dynamic instability condition was conducted systematically, especially on the remote correlation between north Pacific ocean SST and times of spring sandstorm in Ningxia, coupling relation and the relation between the anomaly of California and its possible impact on the sandstorm. The results show that:1. The times of spring sandstorm in Ningxia decreased in general with an obvious phase characteristics during 1961-2003 and there was a mutation in the middle of 1980s;2. The instability increased distinctly before sandstorm occurrence;the instability occurred mainly beneath 700 hPa, and most prominently beneath 850 hPa;the instability touched the summit in the course of sandstorm.3. Indices of the intensity, area of north hemisphere polar vortex, index of Asia monsoon circumfluence and the days of Ningxia gale in spring, mean temperature in winter, and the difference of temperature between winter and spring have the consistent annual variation features with the sandstorm, that means the factors of frequency of cold air activity experienced a mutation in the middle of 1980s.4. There is an obvious negative correlation between the frequency of spring sandstorm in Ningxia and the SST in California from the previous October to May in the same year, and the ENSO in the north Pacific impressed the spring sandstorm in Ningxia greatly, less sandstorm with the El Nino pattern, vice versa.5. The years with colder water in the key region in spring, the Eurasian high air systems are stronger, the meridional circulation increased, lower Mongolian cyclones are favorite to guide the cold air to the south and lead to more sandstorms occurrence. The east Asia troughs locate west and much deeper in the most of the years, western indices are more like to be negative, meridional circulation intensified, the cold fronts are more dynamic, most of the years have lower temperatures. Vice versa.