Surface Forcing of the Infrared Cooling Profile over the Tibetan Plateau. Part I: Influence of Relative Longwave Radiative Heating at High Altitude

Abstract

Abstract The role of the Tibetan Plateau on the behavior of the surface longwave radiation budget is examined, and the behavior of the vertical profile of longwave cooling over the plateau, including its diurnal variation, is quantified. The investigation has been conducted with the aid of datasets obtained during the 1986 Tibetan Plateau Meteorological Experiment (TIPMEX-86). A medium spectral-resolution infrared radiative transfer model using a simple modification for applications in idealized complex (valley) terrain is developed for the study. This study focuses on the clear-sky case where the surface effects are most significant. The TIPMEX-86 data, obtained during the spring-summer transition into the East Asian monsoon season, are used to help validate the surface longwave radiation budget at two sites of varying elevation: Lasa (3650 m) and Naqu (4500 m). Based on the degree to which skin-temperature boundary conditions control the magnitude of infrared cooling, we define the concept of relative l...