Precipitation over East Asia simulated by NCAR CAM5 at different horizontal resolutions

Abstract

AbstractLong‐term simulations using version 5.1 of the National Center for Atmospheric Research’ Community Atmosphere Model at low (T42), medium (T106), and high (T266) resolutions were carried out to study the impact of horizontal resolution on the model's performance in reproducing the climatological features of precipitation over East Asia. The simulated spatial pattern of annual mean precipitation amount improves significantly with increased resolution. The low‐resolution model is inadequate to reproduce the precipitation closely associated with fine‐scale orographic forcing, such as the narrow large‐rainfall belt along the southern edge of the Tibetan Plateau. The distribution of rainfall over and around the elevation of the Tibetan Plateau and high‐altitude mountains becomes more realistic at higher resolutions. The proportion of the large‐bias (small‐bias) area continuously reduces (increases) when moving from T42 to T266 resolution. 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. 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.