Korea Institute of Atmospheric Prediction Systems (KIAPS), Seoul, Korea, has developed a new global forecast system since 2011 to replace the current operational model at Korea Meteorological Administration (KMS), which has been adopted from the United Kingdom’s Met Office Unified Model. The physics package of the new model system named KIAPS Integrated Model (KIM) consists of the schemes from existing models, and the GRIMs and WRF are used as the reference models in developing/revising the physics components for the KIM. For the orographic gravity wave drag parameterization, a subgrid orographic parameterization (SOP) implemented in GRIMs is updated by including the effects of orographic anisotropy and flow-blocking drag (FBD). The impact of the updated SOP on short-range forecasts is investigated using the GRIMs applied to a heavy snowfall event over Korea on January 4, 2010. When the SOP is updated, the orographic drag in the lower troposphere noticeably increases owing to the additional FBD over mountainous regions. The enhanced drag directly weakens the excessive wind speed in the low troposphere and indirectly improves the temperature and mass fields over East Asia. In addition, the snowfall overestimation over Korea is improved by the reduced heat fluxes from the surface. The forecast improvements are robust regardless of the horizontal resolution of the model. The parameterization is statistically evaluated based on the skill of the medium-range forecasts for February 2014. For the medium-range forecasts, the skill improvements of the wind speed and temperature in the low troposphere are observed globally and for East Asia while both positive and negative effects appear indirectly in the mid-upper troposphere. The statistical skill for the precipitation is mostly improved due to the improvements in the synoptic fields. The improvements are also found for seasonal simulation throughout the troposphere and stratosphere during boreal winter.

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*email: hj.choi@kiaps.org
*Preference: Oral