Observed heterogeneity in the local atmosphere and land–air heat exchange across complex terrain in the Tibetan mountains

Abstract

Surface heating is important in terms of the thermal effect of the Tibetan Plateau on atmospheric systems in Asia. The complex mountain terrain across the Tibetan Plateau introduces small-scale heterogeneity in the local atmosphere and land-air heat exchange that biases our understanding of the Tibetan thermal effect and misleads boundary-layer parameterization for numerical studies and predictions. It is therefore essentially important to evaluate heterogeneity in the Tibetan mountains. An observational experiment was conducted in a small region with a complex landscape in the eastern Himalayas from June 9 to July 9, 2013. This study analyzes the observations of three major land covers and discusses the observed heterogeneity of the local atmosphere and land-air heat exchange. A heterogeneity rate is defined to approximately quantify the heterogeneity observed in the atmospheric properties and land-air heat exchange. Obvious heterogeneity is found in the local atmosphere across the complex terrain of the Eastern Himalayas, which could introduce uncertainties up to 33.3 percent in our knowledge related to the local weather and climate. A large heterogeneity is revealed in the land-air heat exchange, which would bias our understanding of total surface heating in this region up to 16 percent and of heating properties up to 62 percent. Therefore, attention should be given to the uncertainties introduced by small-scale heterogeneity in any weather and climate studies across a complex terrain, such as the eastern Himalayas. In addition, the heterogeneity rate provided could be a useful measure to generally identify the uncertainties in our understanding of the local atmosphere and land-air heat exchange across a complex terrain.