Study on the Model between the Occurrence Area of Grasshopper and the Characteristic Quantity Indexes of Atmospheric Circulation in Western Aletai

By analyzing the correlation between the occurrence area of grasshopper and 74 characteristic indexes of atmospheric circulation in western Aletai from 1991 to 2008,the atmospheric circulation factors which had the significant relationship with the occurrence area of grasshopper in different counties were screened.The prediction models for the occurrence area of grasshopper in different counties were established by stepwise regression method,and the models obtained were also tested.These models were subsequently utilized to carry out extended prediction on the occurrence area of grasshopper in different counties of western Aletai from 2009 to 2010.Meanwhile,the relationship between the atmospheric circulation factors and the occurrence area of grasshopper were analyzed.The results provided the theoretical basis for the prediction on grasshopper plague.

The Shallow Meridional Overturning Circulation in the Northern Indian Ocean and Its Interannual Variability

The shallow meridional overturning circulation (upper 1000 m) in the northern Indian Ocean and its interannual variability are studied, based on a global ocean circulation model (MOM2) with an integration of 10 years (1987-1996). It is shown that the shallow meridional overturning circulation has a prominent seasonal reversal characteristic. In winter, the flow is northward in the upper layer and returns southward at great depth. In summer, the deep northward inflow upwells north of the equator and returns southward in the Ekman layer. In the annual mean, the northward inflow returns through two branches: one is a southward flow in the Ekman layer, the other is a flow that sinks near 10°N and returns southward between 500 m and 1000 m. There is significant interannual variability in the shallow meridional overturning circulation, with a stronger (weaker) one in 1989 (1991) and with a period of about four years. The interannual variability of the shallow meridional overturning circulation is intimately r

Regional Atmospheric Blocking in the Drought Periods in Ukraine

The conditions for regional circulation of the atmosphere in the periods of severe droughts in Ukraine are described by two circulation indexes. In analogy with experimental index EBI （European Blocking Index） for the Eastern Atlantic and Western Europe is proposed a new index ECBI （European Continental Blocking Index）, which describes the blocking of zonal flow over the European continent. The obtained time series of the ECBI for the spring-summer seasons with the severe droughts in Ukraine were analyzed. Katz circulation index was used for the estimating of intensity of the meridional atmospheric processes during the same droughts. It is shown that there registered a high frequency of blocking processes which was accompanied by positive phases of ECBI and an increase in the meridional component of an atmospheric flow over the region of Europe. In years with droughts in average 60% consecutive pentads were with a positive value of ECBI, mostly in April to May. The absolute maximum duration of blocking was the 10 consecutive pentads and observed in 1963. The high positive values of the ECBI and Katz index were connected with strong anomalies in seasonal and monthly fields of wind over territory of Eastern Europe. A close relationship between the ECBI and the Katz index was obtained, which allowed to determine the critical value of the Katz index for the beginning of blocking situation,

DISCONTINUOUS OSCILLATION IN THE ATMOSPHERIC CIRCULATION AND INDEX CYCLE

By using a low-order,two-layer baroclinic quasi-geostrophic model,a nonlinear system including the interaction between a thermal forced wave,a transient wave and zonal flow is studied. Under the conditions of near-resonance and weak baroclinic instability,the features of solution in phase space are discussed with the analytical methods of multiple scale and discontinuous oscillation.The results show that the dynamic coupling between forced wave and transient wave is responsible for the physical mechanism of the non-uniform index cycle of the atmospheric circulation.