A Latent Heating Retrieval Algorithm For Typhoon And Plateau Precipitation System

Latent heat released by precipitation provides about three quarters of energy needed by global atmospheric circulation.The accuracy of model simulation is also partly determined by comprehensive understanding of distribution and intensity of latent heat.However,it is difficult to estimate it quantitatively.It is indicated that the vertical lapse rate of rain rate(-dRr/dz)and latent heating(LH)is connected in some way,which implies a unique way to estimate LH structure of high spatial and temporal resolution.By using WRF model,the structure of precipitation in typhoon Chaba is simulated.It is found that-dRr/dz has a good positive correlation with LH in spatial distribution.The correlation between them is sensitive to temporal and spatial scale.As the scale for both time and space is coarsened,the correlation become more significant.This sensitivity can be related to asynchronism of cloud formation and precipitation formation.To weaken the influence of the asynchronism,a relatively coarse scale is chosen,and a new and simple algorithm is developed in the form of a linear function in this scale.In this algorithm,precipitation profile is the main input.Self-consistency check is conducted and little bias is discovered.Applying the new algorithm to satellite products and comparing it with SLH,its accuracy is validated.It is found that the new algorithm is able to produce the overall features of LH's spatial structure in the same typhoon precipitation system.On the basis of conclusions above,the correlation between LH and-dRr/dz over the Tibetan Plateau(TP)is analyzed by using WRF model again.Two variables are found well correlated in this region,and have consistent spatial distribution at each moment.Based on physical connection between them,a semi-physical LH retrieval algorithm exclusively for the TP region is developed.The algorithm is a piece-wise function with precipitation and temperature profile as input.It is found performing well in both self-consistency check and the validation experiment.Two advantages of the algorithm is given:(1)it is not based on the Look-Up Tables,so it is very easy to apply;(2)it can provide LH profiles with the end exactly being the surface,that is,it is not affected by terrain variations.The algorithm is utilized to analyze the statistical characteristics of LH profile over the TP.The further validation with satellite products for the algorithm is also conducted.In conclusion,the new algorithm can retrieve the overall pattern of SLH over the plain,and that of CSH over the plateau.The influence from the freezing level is significant,and often determines the location of maximum heating in LH profile.