Characteristics of Wind Field and Turbulent Flux in the Surface Layer in Dali before and after the Southwestern Monsoon Burst in 2008

Observation data of the boundary-layer tower at the Dali National Climate Observatory from April to May 2008 were used to investigate the characteristics of wind speed, direction, profile, vertical shear, momentum flux, and sensible and latent heat flux in the surface layer before and after the southwestern monsoon burst in 2008. The results show that the main wind direction was southeast in April and northwest in May. The diurnal pattern of wind speed before and after the monsoon burst showed two peaks and one peak, respectively. After the monsoon burst, the wind speed, vertical shear, and momentum flux became lower. The latent heat flux was larger than the sensible heat flux throughout the entire period. The latent heat flux decreased (increased) before (after) the monsoon burst. The peak values of diurnal variation of monthly mean latent flux did not change significantly during the period, although the monthly mean values of sensible heat flux decreased monthly from April to June. The causes of the changed characteristics for wind and fluxes correlated with the weather and land surface conditions.