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As part of the GOES-R and NPP risk reduction programs, the Regional Atmospheric Modeling System (RAMS) was used to simulate different mesoscale weather events. RAMS was developed at Colorado State University (CSU) and is a fully staggered, non-hydrostatic, compressible cloud model. For our purposes, RAMS was initialized with spatially varying observations from ETA analysis. In addition, the model was run with not only a two-moment microphysical scheme, but also the two-way interactive nested grids procedure. In particular, two-moment microphysics and two-way interative grids were necessary for the production of synthetic satellite imagery. A total of four grids were used in the simulations. Grid 3 had horizontal grid spacings of 2 km–approximately the size of the GOES-R ABI footprint–while Grid 4 had horizontal grid spacings of 400 m–approximately the VIIRS footprint. Output from the model–both moments from all seven hydrometeor types, pressure, temperature, and water vapor–are used as input to the observational operator.
After RAMS completes a run, the observational operator reads in output from the model. One of the first things computed by the observational operator is the transmission through the gaseous atmosphere by calling a routine called OPTRAN. Clear sky optical depth is then computed from the transmission. Next, optical properties of each hydrometeor type–aggregates, cloud water, graupel, hail, pristine ice, rain, and snow–are computed based on modified anomalous diffraction theory. Bulk optical properties are then calculated as a weighted mean from each hydrometeor type and are used to diagnose brightness temperatures. Brightness temperatures for a given wavelength are then computed by radiative transfer models–one for clear sky and one for cloudy skies. Brightness temperatures, along with a lat/lon data set, are used to place the synthetic image in a Mcidas area file, a format that is somewhat familiar to most.
Simulated GOES-R ABI 10.35 mm band at 2-km grid spacing. Click the image for a loop.
Simulated NPOESS VIIRS 11.02 mm band at 400-m grid spacing. Click the image for a larger version.
Simulated GOES-R ABI 3.9 mm band at 2-km grid spacing. Click the image larger version.
Simulated Precipitable Water DPI at 2-km grid spacing. Click the image for a loop.
Simulated CAPE DPI at 2-km grid spacing. Click the image for a loop.
Simulated Convective Inhibition DPI at 2-km grid spacing. Click the image for a loop.
Simulated GOES-R ABI 10.35 mm band at 2-km grid spacing. Click the image for a loop.
Simulated GOES-R ABI 3.9 mm band at 2-km grid spacing. Click the image for a loop.
Simulated GOES 10.35 mm from 12 February 2003. Click the image for a loop.
Actual GOES Channel 4 (top) and simulated GOES Channel 4 (bottom) for comparison. Click the image for a loop.
Simulated CAPE DPI at 2-km grid spacing. Click the image for a loop.
Simulated Precipitable Water DPI at 2-km grid spacing. Click the image for a loop.