Kajian Atmosfer Bawah Wilayah Tropis dan Subtropis

Abstract

Planetary Boundary Layer is the lowest part of the atmosphere directly affected by the earth’s surface and responds to surface forcings within a time period of hourly to daily. The thickness of boundary layer varies over space and time, ranging from hundreds of meters to a few kilometers. The objective of this study consist of the analysis of Boundary Layer based on diurnal and nocturnal vertical profiles of meteorological properties and identification of characteristics pertaining to tropical atmosphere (represented by Soekarno-Hatta (6.110S, 106.650E), Polonia (3.560N, 98.680E), and Da Nang (16.030N, 108.200E) stations) and subtropical atmosphere (represented by Perth (31.930S, 115.960E), Nanjing (32.000N, 118.800E), and Hakasskaja (43.780N, 87.620E) stations). Virtual potential temperature, specific humidity, wind speed and direction, atmospheric stability, and Bulk-Richardson number are used to estimate the boundary layer thickness. Vertical profile of the virtual potential temperature and specific humidity are used to determine the Mixed Layer heights during the day and Residual Layer heights during the night. On the other hand, the mean value of Turbulent Flow Thickness is derived from the vertical profile of the Bulk-Richardson number (RiB). Analytical results of this study revealed that Mixed Layer height in the tropical atmosphere varies in a range from 260 m to 1410 m, Residual Layer height varies in a range from 267 m to 925 m, whereas the Turbulent Flow Thickness variation is confined between 0 m to 335 m. In subtropical atmosphere Mixed Layer height varies in a range from 101 m to 1483 m, Residual Layer height varies in a range from 121 m to 1276 m, whereas the Turbulent Flow Thickness variation is confined between 0 m to 769 m. This study also revealed that, except during summer, Mixed Layer Heights in the tropics are normally higher than in the subtropics.