The resolution of a general circulation model is a major factor that affects the numerical simulation of weather and climate. It is found that high-resolution models are able to simulate more realistic topography and large-scale atmospheric circulation. However, some studies argued that increasing the resolution does not always improve the simulation of rainfall. Therefore, what influences of model resolution would have on East Asian rainfall, especially over regions with complicated topography, is still worthy of further study.

Concentrating on this issue, scientists from Institute of Atmospheric Physics and Chinese Academy of Meteorological Sciences, China Meteorological Administration found that simulations at all three resolutions can capture the key features of the major seasonal variation of rainfall arising from the onset and advancement of the Asian monsoon. As the resolution increases, the simulated spatial pattern ？of annual mean precipitation amount improves significantly.

The distribution of rainfall over and around the elevation of the Tibetan Plateau and high-altitude mountains becomes more realistic at higher resolutions. Furthermore, a ？novel method is used to evaluate the sensitivity of the simulated intensity-frequency structure to the horizontal resolution. The proportion of light rain, which demonstrates large positive bias in climate models, decreases dramatically at higher resolution. The intensity-frequency structures averaged over steep-terrain regions and plain areas become more distinctive and realistic？as the resolution increases.

Fig. 1. Spatial distribution of the percentage of weak precipitation amount [intensity less than or equal to 3 mm (3h)^？1] to total precipitation amount in (a) TRMM, (b) T42, (c) T106, and (d) T266 (units: %, the black and red rectangles denote the areas of the main body of the Tibetan Plateau and central and eastern China).

The study has been published in Journal of Advances in Modeling Earth Systems in 2015.

Citation:

Jian Li, Rucong Yu, Weihua Yuan, Haoming Chen, Wei Sun and Yi Zhang, 2015: Precipitation over East Asia simulated by NCAR CAM5 at different horizontal resolutions J. Adv in Modeling Earth Syst, doi: 10.1002/2014MS000414.