The Observation And Simulation Of Turbulence Fluxes Over Rice Paddy And Dry Farming Land

The differences of turbulent fluxes and heat budget over the rice paddy and dry farming land are presented in term of the eddy covariance and profile methods based on the radiation components, turbulent and related data observed in Anhui province supported by national '973' rainstorm program from June 11 to July 20, 2001. Furthermore, turbulent fluxes in different stages of rice growth season with observed forcing variables are simulated by SiB2, and they are compared in between observed fluxes and model values. The result may effect for understanding and improving the parameterized scheme of different land surface. The main results are as follows:The difference of albedo over the rice paddy and the dry land is not large with mean value 0.16-0.17 during observed period. Their main difference is that the albedo varies with growing rice and the albedo is constant with the time in the dry land. The net radiation in the dry land is about 10% larger than that for the rice paddy. The heat fluxes of sensible and latent are mainly budget items of net radiation, they compose of 16% and 35% of net radiation, separately, and the rest is soil heat conduction over the dry land. The latent heat flux is a prevailing item of the net radiation over the rice paddy, which is 70% of the net radiation, others are the sensible heat flux and soil heat conduction. It can be seen that the latent heat of rice paddy is greater, and rest items is smaller. The closure error of energy shows that neither of the rice paddy and the dry farming land is not closed with average 10% error during the observed period. In the dry land, the daytime closure error is small and the nighttime closure error is large. On the average the closure error over rice paddy is larger than that over the dry area.Rice paddy assimilates CO2 from atmosphere by photosynthesis, the CO2 flux during daytime is obviously larger than the flux released at night, which means rice paddy is the sink of CO2. The mean flux is 1.963g/m2h during the observed period.The simulated result for rice paddy of SiB2 model is the best in tillering stage, and take the second place in jointing stage, and is the worst in mature stage. The simulation effect for net radiation is the best and the correlation coefficient of observed flux and simulated flux is 0.98. SiB2 underestimates net radiation 4%. The correlation coefficient of observed latent heat and simulated latent heat is 0.97 and SiB2 overestimates it 13%. At the same time, SiB2 overestimates sensible heat flux and soil heat flux separately 40% and 23%. In dry farming land, SiB2 underestimates net radiation and sensible heat flux separately 7% and 5%, but overestimates latent heat flux and soil heat flux separately 27% and 40%. It shows that the SiB2 model has the better simulation effects for net radiation and latent heat flux, and that it is necessary to improve the simulation effect for sensible heat flux and soil heat flux.