A Simulation Study on Radiation Budget and Water-Heat Exchange over Alpine Grassland Based on CLM4.5

Abstract

Forced by observations from 1 June to 31 August 2014， which are provided by Naqu station of Plateau Climate and Environment in northern Qinghai-Xizang Plateau， CLM4.5 is used to evaluate the influence on simulated results of both radiation balance and exchange of water-heat after some surface parameters and parameterization schemes including LAI、 vegetation coverage and roughness length have changed.The reason for these changes are also discussed in this article.The results suggested that （1） Compared with the results produced by default scheme Z98， those of schemes named Z12 and B82 perform better in decreasing the positive bias of latent heat fluxes and negative bias of sensible heat fluxes.（2） aerodynamic roughness length calculated by revised Massman model and a method named “Chen” are respectively used to replace the default value， the outcomes produced by CLM approach the observations further.（3）With leaf area index increasing， sensible heat fluxes and reflected radiation and surface long-wave radiation decrease a lot， while latent heat fluxes are on the increase.（4）As the vegetation cover increases， latent fluxes decreases， while sensible heat fluxes and reflected radiation and surface long-wave radiation rise， meanwhile soil temperature and moisture also rise.The aim of this study is to provide a basis for future ambition to simulate the balance of ground surface water and heat over the whole Plateau.

Keywords

• land surface model
• radiation budget
• water and heat exchange
• roughness length
• plant parameters