The global monsoon system is simulated by IAP 9L AGCM. The result indicates that the model successfully simulates the monsoon system in the lower troposphere including the classic tropical monsoon, the subtropical monsoon and the temperate-frigid monsoon. Besides, the planetary monsoon in the upper troposphere is also realistically reproduced. On the other hand, the stratospheric monsoon is poorly simulated, a further analysis reveals that this is caused by the systematic overestimation of the westerly in the model.
The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variations are remarkably different.The variability of the instant flux in the afternoon is much larger than in the nighttime.The afternoon and nighttime flux anomalies tend to be opposite.The diurnal and seasonal dependence of sensible heat flux variations is closely related to the diurnal cycle of mean land-air temperature difference.The relationship of sensible heat flux with land-air temperature difference based on the instant value differs from that based on the daily mean.The present study indicates the importance for the models to properly simulate mean land-air temperature difference and its diurnal and seasonal variations in order to capture surface sensible heat flux variability over Northwest China and predicts its plausible impacts on climate.
In this paper, by using the sounding data collected in LOPEX05, we have analyzed the vertical atmospheric structure and boundary layer characteristics of temperature and humidity in the late summer over the east Gansu loess plateau. The results show that the bottom of the stratosphere is at about 16 500 m and varies between 14 000 m and 18 000 m above the ground. The center of the westerly jet is located between 8300 m and 14 300 m above the ground and its direction moves between 260~ and 305~. There is an inverse humidity layer at about 3000 m height above the ground. The maximum of the air temperature occurs at 1700 LST in the layer below 800 m above the ground. The inversion layer is relatively thick. The time that the maximum of the vapor occurs is not the same for different layers. The depth of the atmospheric boundary layer can reach about 1000 m and the depth of the stable boundary layer can be 650 m.
This study evaluates the spatial distributions in the quality of momentum and sensible heat fluxes,and determines the turbulent transfer characteristics with quality-controlled observations.The research is based on raw turbulence data collected over a Gobi surface in the Dunhuang area in June 2004.The results indicate that part of the momentum fluxes are of poor quality in the daytime and nighttime.The poor quality of the momentum fluxes in the daytime is mainly attributed to the development of turbulence.The footprint reveals that,in general,the momentum fluxes and sensible heat fluxes can be measured well in the east and west upwind sectors under unstable conditions.The relationship between the non-dimensional standard deviation of the wind components and atmospheric stability follow the "1/3 power law",which supports the Monin-Obukhov similarity theory.Moreover,this study identifies a clear disturbance in the measurements surrounding the Gobi surface.The momentum roughness length of z0m=0.59 mm is determined after excluding such disturbance,and the additional resistance during the daytime is proposed to be an average of 3.1,although its actual value is highly scattered.This study discusses the applicability of several thermodynamic parameterization schemes for the Gobi surface.The results show that the scheme κB-1=3.1 can represent well the summer diurnal turbulent heat transfer.
The temporal variations in storm rainfall during the first rainy season (FRS) in South China (SC) are investigated in this study. The results show that the inter-annual variations in storm rainfall during the FRS in SC seem to be mainly influenced by the frequency of storm rainfall, while both frequency and intensity affect the inter-decadal variations in the total storm rainfall. Using the definitions for the beginning and ending dates of the FRS, and the onset dates of the summer monsoon in SC, the FRS is further divided into two sub-periods, i.e., the frontal and monsoon rainfall periods. The inter-annual and inter-decadal variations in storm rainfall during these two periods are investigated here. The results reveal a significant out-of-phase correlation between the frontal and monsoon storm rainfall, especially on the inter-decadal timescale, the physical mechanism for which requires further investigation.
In this study, the teleconnection between Indian Ocean sea surface temperature anomalies （SSTAs） and the frequency of high temperature extremes （HTEs） across the southern Yangtze River valley （YRV） was investigated. The results indicate that the frequency of HTEs across the southern YRV in August is remotely influenced by the Indian Ocean basin mode （IOBM） SSTAs. Corresponding to June-July-August （JJA） IOBM warming condition, the number of HTEs was above normal, and corresponding to IOBM cooling conditions, the number of HTEs was below normal across the southern YRV in August. The results of this study indicate that the tropical IOBM warming triggered low-level anomalous anticyclonic circulation in the subtropical northwestern Pacific Ocean and southern China by emanating a warm Kelvin wave in August. In the southern YRV, the reduced rainfall and downward vertical motion associated with the anomalous low-level anticyclonic circulation led to the increase of HTE frequency in August.
