Lidar Simulation Model: MADS Atmospheric Variables

The Eta Model

The meso-scale atmospheric input-variables-representation employed by the AGM are provided by the 3-hour forecast of the National Center for Environmental Prediction (NCEP) mesoscale, step-mountain Eta coordinate model, more commonly known as the mesoscale Eta model. Operational since the fall of 1995, the mesoscale Eta model, so-named because of the use of a pressure-based vertical coordinate (Eta) which is normalized to mean sea level pressure, has a horizontal resolution of 29 km and consists of 50 layers in the vertical between the surface and around 50 mb. This model is run twice daily and provides forecasts up to 36 hours.

The primary prognostic variables of the Eta model are temperature, specific humidity, horizontal wind components, surface pressure and turbulent kinetic energy (TKE).

The model's physical package includes:

- Modifications of the Betts-Miller cumulus parameterization scheme (Betts,1986);

- A cloud water parameterization scheme (Zhao et al., 1991);

- TKE exchanges determined by the Mellor-Yamada Level 2 and 2.5 models (Mellor and Yamada, 1982);

- Stratiform and cumulus interactive clouds are diagnosed based upon the model's relative humidity and convective rain rate (using the scheme of Slingo, 1987).

For a more detailed description of the mesoscale Eta model, the reader is directed to Black (1994).

MADS DATA RECORD

A MADS record content is defined below. Sample graphics for various inputs are provided for a specific constant vertical level.