Citation:

Alapaty, Kiran, R. Bullock, J. Herwehe, R. Gilliam, C. Nolte, T. Otte, J. Kain, AND J. Dudhia. The Kain-Fritsch Scheme: Science Updates & Revisiting Gray-Scale Issues from the NWP & Regional Climatae Perspectives. Presented at Annual Wolf Workshop, Boulder, Co, June 23 - 28, 2013.

Impact/Purpose:

The National Exposure Research Laboratory (NERL) Atmospheric Modeling and Analysis Division (AMAD) conducts research in support of EPA mission to protect human health and the environment. AMAD research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.

Description:

It’s just a matter of time before we see global climate models increasing their spatial resolution to that now typical of regional models. This encroachment brings in an urgent need for making regional NWP and climate models applicable at certain finer resolutions. One of the hindrances of using regional models at these finer grid resolutions, particularly between ~10 to 1 km, is the so-called gray-scale issue related to subgrid-scale convection representation. First, the subgrid-scale and radiation interactions need to be implemented before descending on the development of a seamless convection parameterization. This makes clouds, at the least, adequately represented in the regional modeling systems. Then, it is the time to tease a few important parameters in a convection parameterization about their scale dependency. These parameters/processes can be: (1) convective adjustment timescale; (2) entrainment of air from the environment; (3) evaporation of falling precipitation; and (4) representation of convective cloud microphysics. We are cognizant that there may be other equally important parameters – but, for now, this is a good start with few in hand. The ultimate goal of this research is to make the Kain-Fritsch scheme used in the WRF model operable at all spatial scales up to ~1 km grid resolution. This effort opens up doors for a seamless representation of subgrid-scale convection. We present preliminary results obtained from using various grid resolutions in several test case studies ranging from short- to long-term simulations.

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