Impacts of sea surface roughness parameterization in KMA operational NWP model

In the Earth system, the ocean interacts with the atmosphere, exchanging water, momentum, and heat energy. This exchange influences not just the ocean but also atmospheric phenomena such as clouds, precipitation, and temperature. In particular, the ocean's latent and sensible heat significantly affect the temperature and moisture of the lower atmosphere, serving as a key process for energy transfer between the atmosphere and the ocean. In numerical weather prediction models, heat exchange is parameterized based on temperature, moisture, wind, and heat and moisture exchange coefficients. These factors are crucial for predicting severe weather around the Korean Peninsula. Since April 2020, the Korea Meteorological Administration (KMA) has operated the Korean Integrated Model (KIM) for medium-term weather forecasts. Sea surface temperature and sea ice concentration in KIM are initialized with OSTIA (Operational Sea Surface Temperature and Ice Analysis) data from the UK Meteorological Agency. The model's physical process for sensible and latent heat exchange between the atmosphere and the ocean relies on the difference in temperature and moisture between the sea surface and the atmosphere's lowest layer, the model's lowest wind speed, and the coefficients for heat and water exchange. These coefficients are determined by parameterizing the sea surface's roughness length, which accounts for factors such as gravitational wave effects. By examining the atmospheric-ocean energy exchange process in KIM during summer torrential rains on the Korean Peninsula, we assess the model's capability to simulate atmospheric-ocean interactions via sea surface roughness parameterization and depth correction, thus evaluating its impact on mid-term weather forecasting accuracy.