HR: 1330h
AN: A43A-01    [Abstracts]
TI: A simplified Explicit Scheme of Phase-mixed Cloud Used in WRF model and precipitation experimentation
AU: * Yan, Z
EM: yanzh@cma.gov.cn
AF: Yan Zhihui, National Meteorological Center/CMA, Beijing, 100081 China
AB: Based on WRF model (Version 1.3) system introduced in National Meteorological Center /CMA, a simplified explicit scheme of phase-mixed cloud (HL3) was introduced in the model successfully. The case study of precipitation prediction, with the initial fields and boundary conditions provided by the medium-range prediction system T213 run in the National Meteorological Center, were made for the scheme (HL3) and compared with the original simple ice explicit scheme (Ncloud3) in the model, and the diagnosis analysis on the horizontal and vertical distributions of cloud physical parameter such as cloud water and rain water were made for the two schemes, also. HL3 is a simplified version of explicit moisture scheme of phase-mixed cloud developed by Z. Hu and Q. Liu in CAMS/CMA, in which the moisture, cloud water, cloud ice, rain water, snow and graupel are considered as prognostic variables. Compared with Ncloud3 scheme, the main differences included: (1) the cloud was divided into cloud water and ice crystal according to the atmospheric temperature in Ncloud3; but in HL3, the supercooled cloud water is the only form when temperature is lower than 0­aC, no cloud ice existed. (2) two processes, the nucleation and multiplication of ice crystal, are taken into account in HL3. In these two processes, the cloud water was transformed into snow crystal directly, and falling toward to the ground with terminal speed. The precipitation prediction experiment was made with initial fields at 0000UTC 10 October 2003. This is a heavy rainfall case occurred in east part of China. Fig.1 (a) is the observed accumulated precipitation amount (mm) from 0000 UTC 10, October 2003 to 0000 UTC 11 October 2003. The blue shaded area showed the rain area over 10 mm. Fig.1 (b) and (c) are the corresponding 24-h prediction by HL3 and Ncloud3 respectively. From Fig.1 we can see that the rainfall area predicted by two schemes is the same completely, almost, but the distribution of heavy rain belt is different. Compare the rain belt over 50mm with Fig.1 (a), (b) and (c), we can see that although the heavy rain belt predicted by two schemes was deviated to the east from the observation, the prediction for the sub-heavy rain belt near the Yangtse River is different obviously. Since the prediction of the precipitation intensity made by HL3 is stronger than that by Ncloud3 scheme, the prediction of this rain belt made by Ncloud3 scheme was pass over, but it was predicted correctly by HL3 scheme. Fig.1 Comparison of precipitation prediction with two schemes (a) Observed accumulated precipitation amount from 0000UTC 10 October 2003 to 0000UTC 11 October 2003 (b) 24-h accumulated precipitation amount prediction made by HL3 (c) 24-h accumulated precipitation amount prediction made by Ncloud3 The preliminary results was shown that the precipitation forecast made by the simplified explicit scheme of phase-mixed cloud is correspond to that by simple ice explicit scheme, and has a improvement on the precipitation intensity, slightly. The predictions to the spatial and temporal distributions of cloud water and rainwater as well as the vertical distribution of mean rainwater over main precipitation area are improvement somewhat, also.
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly