Comparing to observation (panels a and e), most climate models have too much sunlight reaching the surface (panel b), but they reflect even more sunlight (panel f), resulting in strong cold biases over the Tibetan Plateau. Inclusion of 3D radiation-topography interactions can significantly reduce the amount of reflected sunlight (panel h), and hence warm up the surface. Credit: Lee et al. [2019], Figure 5
Source: Journal of Geophysical Research: Atmospheres

Because the massive glaciers and snowpack over the Tibetan Plateau supply fresh water to more than a billion people, accurate climate simulation in this area is critical to water resource management. Temperature is the sole factor dictating snow melting, but it has been systematically underestimated by virtually all global climate models, partially because of a common assumption that the land surface within a grid box is flat. As such, they cannot account for the three-dimensional interactions between sunlight and topography, such as shadow cast by mountains and surface-to-surface reflections.

Lee et al. [2019] developed a computationally efficient algorithm to quantify the impact of this interaction on the solar energy absorbed by the surface for application to climate models. They find that the problem of serious underestimation of surface temperature over the Tibetan Plateau is significantly lessened by including the interactions, which can reduce the amount of sunlight absorbed by mountainous surfaces. By considering the topographic effect, model simulations can be improved both for simulating the present climate and for projecting future climate change, especially in the Tibetan Plateau whose water resource is key in East and South Asia.

Citation: Lee, W.‐L., Liou, K.‐N., Wang, C.‐c., Gu, Y., Hsu, H.‐H., & Li, J.‐L. F. [2019]. Impact of 3‐D Radiation‐Topography Interactions on Surface Temperature and Energy Budget over the Tibetan Plateau in Winter. Journal of Geophysical Research: Atmospheres, 124.

—Zhanqing Li, Editor, JGR: Atmospheres

Text © 2019. The authors. CC BY-NC-ND 3.0
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