Numerical Modeling - RAMS
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.
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.
Synthetic Imagery - Examples
Severe Weather Simulation - 8 May 2003
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.
Hurricane Lili Simulation - 30 September - 4 October 2002
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.
Lake Effect Snow Simulation - 12-14 February 2003
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.
Additional synthetic imagery, as well as a number of observed satellite images can be found in the Case Study Database