| The air-ground exchange process on the inhomogeneity underlying surface, which is more complex than homogeneous surface, affect the weather process and global climate changes. Beijing has a typical inhomogeneity underlying surface, with a urban center and suburban surrounding, and with a different dynamic and thermal characteristics between urban and rural, and the interaction between them has an important implications on the formation and change of the weather, climate, environment, in the North China.Based on the radiation and fluxes data observed in January, April, August, October 2007 at Miyun station in Beijing, the radiation balance, albedo and energy balance under different types of synoptic conditions, including clear days and obscured days on heterogeneous underlying surface, are analyzed. The result shows that:(1) The energy balance closure (OLS) were 82%,97%,72%, and 83% in January, April, August and October, respectively. The total energy balance closure was 76%, indicating quality data.(2) As the changing of mixed crop-forest underlying surface, in clear days, the average of outcoming long-wave radiation were 279.6,381.5,430, and 358.7 W/m2 in January, April, August, and October, respectively. The respond time of short-wave radiation was 0.5 hr and 1.5 hr in January and August, respectively.(3) The albedo has an significant change with the both surface moisture and vegetation condition. The monthly averaged of albedo in clear days were:0.183,0.143,0.133, and 0.139, in January, April, August, and October. The diurnal variations of albedo were asymmetrical. The albedo was lower than that of Gucheng Station which had a value of 0.19 in October.(4) In clear days, the components of energy balance showed standards daily cycle patterns, the primary distribution of energy was the sensible heat exchange in January, April and October, while mainly used for latent heat exchange in August. The characteristics of energy distribution on obscured days were the same as that on clear days.The WRF model and its coupling Urban Canopy Model (UCM) are applyed. Furthermore, the WRF model dated land use classes data are replaced by real time one which come from the MODIS, to simulate the different characteristics of meteorological elements, turbulent activity and air-ground exchange on inhomogeneity underlying surface in Beijing. Take January 12, 2007 as the representative of winter, and August 30,2007 as representative of summer, which have a sunny, little wind weather. The results showed that:(1) The simulated flux value is consistent with the observed one. The height of urban boundary layer reached 1000 meters in winter, while the height of rural boundary layer was 700 meters; the urban rate of temperature inversion did not exceed 0.4 K/100m at night, while the rural rate of inversion up to 3.8 K/100m.(2) The height of boundary layer (BLH) was higher in summer than that in winter. In summer, the BLH in rural was 200m lower than the urban's during 11:00-14:00. At 15:00, the BLH both reached 1600m in urban and rural. And at 18:00, the BLH in rural dropped to 900m while it remains unchanded in urban. The rural rate of temperature inversion was betweened 2.7-4.2K/100m, due to the effect of thermal storage in urban, the rate of temperature inversion was betweened 1.1-1.9K/100m in urban.(3) The turbulent kinetic energy (TKE) in urban was much higher and grew faster than that in rural after sunrise. In winter, the maximum TKE was 0.59 m2·s-2 in urban while 0.39 m2·s-2 in rural. The TKE in summer was higher than that in winter, the maximum of TKE was 0.76 m2·s-2 in urban while 0.57 m2·s-2 in rural.(4) In summer, the sensible heat flux was positive throughout the day in urban and higher than other underlying surface; the latent heat flux was very weak throughout the day due to the little humidity; urban canopy layer can store more heat, therefore, soil heat flux in the urban was the largest, which was 270W/m2 at 11:00 and reduced to-80W/m2 at 02:00.(5)In winter, as the urban had a larger turbulent exchange coefficient, and temperature was homogeneous in vertical, the sensible heat flux was not a high value area; the maximum of latent heat flux was just 1.5 W/m2 due to the dry air; the primary distribution of energy is the soil heat flux, which reached 150 W/m2 at noon; the net radiation was larger than other underlying surface in daytime and lower at night in urban.
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