The Improvement And Application Of Air-sea Momentum Flux In The Nansha Aera

Nansha sea area is in a very important strategic position.It is very important to study the structural characteristics of atmospheric boundary layer in Nansha sea area.The momentum exchange between the sea and air interface directly affects the structure of the atmospheric boundary layer,and the wind field and the wave field play an important role in the momentum exchange process.Therefore,a correct understanding of the sea surface wind and wave characteristics and their correlation in Nansha sea area,and the development of a parameterized sea-air flux scheme which is more suitable for Nansha sea area,will effectively improve the ability of the atmospheric model to simulate the structure of the sea and atmosphere boundary layer.Based on the ERA-Interim reanalysis data,the spatial and temporal characteristics of wind and wave fields in Nansha areas are statistically analyzed,and the relationship between wind and wave growth is further studied to establish a wind-wave model suitable for the Nansha areas.The monthly mean field analysis shows that in the monsoon period,the spatial and temporal distribution characteristics of monthly mean significant wave height(Hs)has a good correspondence with that of the wind field.In the southeast of Indo-China Peninsula,there is a high value center for both wind speed and Hs,where the winter value is much stronger than the summer,and the center position moves slightly and seasonally down the wind.The frequency analysis shows that the frequency of 0?4 grade wind and wave-height within 3-class is the highest.The wind-force scale above 6-class and waves above 5-class mainly appear in the winter.The maximum wind speed and wave height in the whole year appears in October and November,when the maximum wind speed is up to 8-class and the maximum Hs is 6-class,although the probability is extremely low.The minimum wind speed and wave height appear in April and May.Then the parameterized sea surface roughness scheme of Gao12 is introduced into the mesoscale atmospheric model WRF,and the prediction accuracy of the model to the boundary layer wind field is verified.The results show that when the wind speed is less than 10m/s,compared with the classical charnock scheme,the Gao12 parameterization scheme has a better effect on wind field prediction.Without typhoon,the prediction error is 1-2 m / s,the correlation coefficient is more than 0.7,the overall deviation is about 1m/s,and the deviation increases to 2-3 m / s when affected by typhoon.It has been proved by practice that the Gao12 scheme introduces the atmospheric model and improves the aerodynamics of the sea.The flux parameterization scheme is effective to simulate the wind field under the condition of medium and low wind speed,and it is also suitable for the Nansha sea area with lower annual average wind speed.Finally,the typical structure characteristics of the sea and air boundary layer in Nansha sea area are analyzed by using the improved numerical simulation platform.The results show that the boundary layer height is relatively stable under the condition of typhoon free from typhoon during the prevailing monsoon.The background wind field and sea surface temperature have great influence on the height of the boundary layer.The more stable the background wind field,the better the relationship between the sea surface temperature and the height of the boundary layer,and the higher the sea surface temperature,the higher the height of the boundary layer.The height of boundary layer in Nansha sea area is about 1000 m during winter monsoon period,followed by summer monsoon period,and the lowest height of boundary layer is in April of monsoon transition period,the average height of boundary layer is below 600 m.Edge The simulation results of diurnal variation of boundary layer height are basically consistent with the actual situation.The convection develops most vigorously during the day,the height of the boundary layer is higher,but at night it is lower.The seasonal variation of turbulent kinetic energy is obvious,similar to the height of boundary layer.The turbulent kinetic energy is the largest during the prevailing winter monsoon,followed by the summer monsoon and the minimum monsoon transition period.The diurnal variation of turbulent kinetic energy is not obvious,and the turbulence is a little stronger in daytime than at night.Turbulence mainly occurs in the boundary layer,with the height rising,the turbulent kinetic energy increases a little first,then decreases rapidly.