A Study On Energy And Water Cycle During HUBEX Periods

In this paper, by using the data of Huaihe River Basin Energy and Water Cycle Experiment (HUBEX) during the summer in 1998 and 1999, on the point of view of multi-scales, the water budgets and the apparent heat source and the apparent moisture sink over East China during the HUBEX periods are calculated and investigated, and the energy budgets of earth-air system are studied in detail by using the especial data of the intensive observation region, and finally the energy and water vapor cycle in the summer of 1998 is simulated by RegCM2. The main results are obtained as follows:1. East China is the strongest water vapor sink over the globe in May-August 1998.The minimum potential region (maximum convergent region) of water vapor transport vector correspond to intense heavy rainfall region, and the water vapor convergence of the heavy rain region is supplied by the hemisphere scale water vapor transport, indicating that even for a regional severe flood it must gain water vapor supply from very extensive regions. The situation of the water vapor convergence center in 1999 is more east and south than in 1998, so the heavy rain region in 1999 is souther than in 1998.2. The water vapor transportation in the South China Sea is well related to occurrence of the heavy rainfalls in China After onset of the South China Sea monsoon, the strong precipitation often occurs in the region where water vapor is gained by water vapor transportation from south. For East China, the water vapor flux from southern boundary is more significant than that from west.3. Atmospheric water vapor budgets in 1998 and 1999 indicate that precipitation comes mainly from the convergence of water vapor, mainly in the lower atmosphere; The local evaporation (calculated by the residual) is generally 1/3~1/2 of the precipitation amount, so the water vapor recycling is also important; The vertical advection of the water vapor transports the moisture from the low to the middle and high layers and increases moisture content at the high levels, thus providing a necessary condition for the cumulus development and latent heat release. 4. During the seven rainfall episodes in 1998 and the five rainfall episodes in 1999, the high value regions of the apparent heat source and the apparent moisture sink corresponds the strong precipitation regions, indicating that the water vaporcondensation is main effect in the air heating. The mean profiles of the area-averaged Ql and Q2 over Jianghui Region indicates that the cumulus convection in 1998 is stronger than in 1999. The analysis of TBB indicates that the convection regions in summer of 1998 move from south to north with the two times of strongest convection over Jiangnan region during Mei-yu periods and the convection occurs with diurnal variation obviously which in day is stronger than in night during 1998 but during 1999 the day convection is stronger than the night.5. The diurnal variation of energy budgets over water body, farmland, paddy field and forest over intensive observation region of HUBEX have their similarities and differences. The similarities: the maximum of the terms of the energy budgets occurs just afternoon; The differences: the maximum is only one over water body and paddy field but it is two or more over farmland and forest. The daily averages have differences too.6. The seasonal variations of energy budgets are obvious over four surfaces. The wave number of daily energy budgets over farmland, forest and paddy field is only one in spring and two or more in summer and only one in autumn, which indicating that the plant growth differences during different seasons maybe cause the variations. But to the water body, the wave number is only one in summer and autumn.7. In different synoptic conditions, the energy budgets are different. The values of sensible and latent heat fluxes are small when it is rain, but thereafter, the values become high and then to maximum. It's similar to the other terms of the energy budgets except the down long-wave radiation. It's similar with rain when it is cloudy.8. The means of the sensible and latent heat flux and momentum flux by bulk schemes for the time period from may to august are respectively 30.71 W/m2, 116.81 W/m2,2.86X10"2N/m2 in 1998 and 30.28 W/m2,107.35 W/m2,2.74X10-2N/m2 inl999. The values between the two years are similar.9. The calculations by bowen ratio, eddy and bulk schemes indicating that the sensible heat flux by the bowen ratio schemes is similar with by eddy schemes, and the latent heat flux by the bulk is similar with by the eddy.10. The simulation of the energy and water cycles over Jianghuai region from May to June in 1998 by RegCM2 is successful, e.g. the precipitation distribution, strong convection activity and the latent heat and sense heat transport etc are very simply to the observations in most regions of East China.Finally, the schematics of the budget of water vapor over Jianghuai region and the schematics of energy budgets over four surface during three seasons are given .