Investigating the Role of MODIS Leaf Area Index and Vegetation-Climate Interaction in Regional Climate Simulations over Asia

Abstract

Four yearlong climate simulations using the Seoul National University, regional climate model have been performed to assess the role of the MODIS Leaf Area Index (LAI) and interactive LAI in influencing Asian climate. The control experiment employs the fixed monthly LAI according to the original land surface model. Another additional simulation replaces the LAI by 4-year mean MODIS climatology. The last two integrations both allow the LAI to interact with the atmosphere, but adopt two different simple parameterization schemes.

Although the control experiment generally reproduces spatial distribution and the magnitude of Asian surface climate, it contains large biases in some specific areas, which are partly improved by the implementation of MODIS LAI and vegetation interaction schemes. In winter months (January-to-March), greener land surface introduced in the last three Simulations reduces cold biases over Northeast China and adjacent areas, southern China, Korea, and Japan, and warm biases over South Asia, and precipitation discrepancies over South Asia, southern China and West Japan. In contrast, LAI changes only play a limited role in summer. There are significant differences between regions with respect to mechanisms explaining winter-month improvement in surface climate Simulations. Over Northeast China and adjacent areas, increased LAI increases net solar radiation by about 12 W m(-2) mainly through the effects on surface albedo, thereby warming the surface by about 1.8 degrees C. A decrease in Clouds makes a major contribution to surface warming and precipitation reduction over southern China. Increased evapotranspiration dominates changes in surface energy balance, and cause less net radiation to be partitioned into sensible heat over South Asia. As a result, the model simulates about 1.5 degrees C colder surface air temperature and about 0.1 mm day(-1) more precipitation over this region. Finally, the implications and limitations of this study are also discussed.