The Characteristics Of The PBL Structure And Its Temporal Evolvement During Summer And Winter Over Gobi Area

Based on the sounding balloon data obtainted in the north of Jiayuguan city, Gansu province in both summer and winter seasons of 2006, the characteristics of atmospheric boundary layer structure and its temporal evolution over the Gobi area are analyzed, and their similarities and differences during different seasons are also investigated . The results show that:1, The transitional layer of wind direction and multi-extremes of wind speed could be observed in both winter and summer seasons under certain conditions. Under the co-function of the transitional layer of wind direction and temperature inversion, which are closely related to the phenomenon of multi-extremes of wind speed, the occurrence frequency of low-level jet in winter is higher than that in summer.;2, There is feedback between temperature inversion and wind speed extremes in winter , the variation of the temperature inversion intensity and height is influenced by both the thermal and dynamic factors ;3, There are intimate relations between profiles of potential temperature and the development of PBL. From the humidity profiles, we can infer that the characteristics of PBL during the most development period of mixed layer could be partially stored in the residual layer;4, There are obvious diurnal and seasonal variations of the PBL height over Gobi surface. It is more reliable to determine the PBL height from humidity profiles under unstable conditions, and under stable conditions the results from wind speed also can be applied. The scattered diagnositic relations between PBL height determined from potential temperature profiles and micro-meteorological parameters indicate the complexity of PBL structure over Gobi surface;5, The forecast result of the development of convective boundary layer under typical clear condition in summer by the zero-order model is satisfying. The development of the nocturnal temperature inversion layer in winter could also be forecasted precisely by the model of Yamada, excluding the effect of radiation. These two models can be recommended as simple forecasting methods.