Improved Indirect Method for Estimating Sensible Heat Flux and Mixed Layer Height

Abstract

Surface and upper air observation have been conducted using Automatic Weather System and radio sonde in order to determine surface heat flux and atmospheric boundary layer depth in coastal area. The vertical profile data based on upper air observation (radio sonde and Terra/MODIS) and surface layer data from automatic weather systems were possible to analyze air - land interaction. Atmospheric turbulence can be explained by surface heat flux and mixed layer height. Sensible heat flux among the surface energy balance equation components is estimated by the indirect method. Subsequently, sensible heat flux was used to estimate the properties of the mixed layer where there is the effect of turbulence from the surface. Sensible heat flux estimated by Gradient method and Penman-Monteith method including Bulk method, and not that measured by using a turbulence instrument, was used with an Integral algorithm to calculate the mixed layer heights inexpensivly. Since the variation in the mixed layer height depends on the surface sensible heat flux, the integral algorithm estimated the mixed layer height in the daytime accurately. The results obtained using the integral algorithm were in good agreement with the mixed layer heights observed using radio sondes at Wolsung (35˚ 43′ 39.61″ N, 129˚ 28′ 51.69″ E), Pohang (36˚ 01′ 56.42″ N, 129˚22′47.09″ E) and Uljin (36˚ 59′ 13.49″ N, 129˚ 25′ 17.02″ E). In particular, the Integral algorithm generated excellent results on sunny days, in the case of the measurements made at Wolsung, the correlation coefficient between the mixed layer heights obtained using Terra/MODIS temperature profiles and those observed using radio sondes was more than 0.8. The turbulence parameter can be estimated not only in the eastern coastal region but also at the South of Korea. On the other hand, the proposed method is not suitable for estimating the turbulence parameter in the eastern coastal region when the wind is blowing from the East Sea. On May 31, 2008 at Uljin, although the sensible heat flux was more than 200 Wm^(-2)(at midday), the coastal boundary layer height was found to be less than 300 m. Finally, the vertical structure of the atmospheric boundary layer can be analyzed using only the routine data and the vertical temperature profiles. With the proposed method, the turbulence parameter as well as the distribution of sensible heat flux and mixed layer height over our country can be estimated.