Spatial distribution pattern of degree–day factors of glaciers on the Qinghai–Tibetan Plateau

Glaciers have a very obvious feedback effect on the global water cycle and environmental change. The Qinghai–Tibetan Plateau, also known as the “Water Towers of Asia,” provides an important source of freshwater resources derived from glacial meltwater. Changes in glaciers on the Qinghai–Tibetan Plateau are the most important aspect of the research related to global climate change. Because only a few input parameters are available, the degree–day factor model of glacier mass balance has been widely used on the Qinghai–Tibetan Plateau. Study of the spatial distribution pattern of degree–day factors for glaciers on the Qinghai–Tibetan Plateau and the factors that influence glaciers is important scientifically. The study of degree–day factors is important to the calculation of the glacial grid mass balance on the Qinghai–Tibetan Plateau, and this data can be used in the analysis of the response of glaciers experiencing climate change and for predicting future glacial trends. Through an analysis of the degree–day factors related to 24 glaciers on the Qinghai–Tibetan Plateau, one can conclude that the mean value of glacial degree–day factors on the Qinghai–Tibetan Plateau is 8.14 mm day^?1 °C^?1. The glacial degree–day factor shows a longitudinal zonality with values ranging from high to low from east to west, a latitudinal zonality with values ranging from high to low from south to north, and a vertical zonal regularity along with the change of elevation. The spatial distribution pattern of glacial degree–day factors in the Tibetan Plateau is related to the fact that the climate environment across the Qinghai–Tibetan Plateau is mainly affected by the Indian monsoon, the eastern monsoon, and the westerly winds. The climate gradually changes from cold-humid to warm-humid from northwest to southeast. The single-unit glacier of Qinghai–Tibetan Plateau—the Renlongba Glacier—is located in the southeastern portion of the Qinghai–Tibetan Plateau in a warm and humid climate; its degree–day factor is slightly large, averaging at 6.12 mm day^?1 °C^?1. Mountainous barriers exist in the eastern and western parts of the Renlongba Glacier. On the east side, the degree–day factor is small (5.63 mm day^?1 °C^?1) because of large mountains block weather systems. The glacial tongue is affected by valley wind, contributing to glacial ablation, so the degree–day factor is large on the tongue, averaging at 6.56 mm day^?1 °C^?1. The degree–day factor on the west side of the Renlongba Glacier increases gradually increasing radiation and elevation, presenting a vertical zonal feature. In general, the climate of the Qinghai–Tibetan Plateau is mainly affected by the Indian and eastern monsoons and by westerly winds. In dry and cold climatic conditions, the glacial degree–day factor in the Tibetan Plateau is small, while at warm and humid climate conditions, it is large, with latitudinal, longitudinal, and vertical zonality. In addition, the degree–day factor is also affected by blocking, topography, and other local microclimatic conditions.