How surface latent heat flux is related to lower-tropospheric stability in southern subtropica marine stratus and stratocumulus regions
AbstractThe relationship between surface latent heat flux and the lower-tropospheric stability (LTS) is examined using ERA-40 reanalysis, NCEP reanalysis and COADS (Comprehensive Ocean-Atmosphere Data Set) ship data in two southern subtropical marine stratus and stratocumulus regions. The change of surface latent heat flux with LTS is determined by a comparison of the correlation of LTS with surface wind speed and with near surface humidity difference. At intermediate LTS (10 K-15 K), both surface evaporation and downward surface radiation flux amplify small LTS perturbations due to the surface wind-LTS relationship and cloud-radiation feedback. At high LTS, surface latent heat flux exceeds its peak value and becomes a regulating mechanism to keep LTS at its commonly observed equilibrium value. Surface radiation flux is seen to decrease at a smaller rate with LTS than surface latent heat flux. By applying the regulating effect of LTS on near surface humidity differences, monthly surface latent heat flux can be better represented.