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Synthetic NSSL WRF-ARW Imagery - 10.35 minus 12.3 µm

Figure 1. Example of a synthetic 10.35 minus 12.3 µm image from 13 April 2011 at 22 UTC. The image is based on a 22-hour forecast from NSSL's 4-km WRF-ARW.

1) Product Information:

- Who is developing and distributing this product?

This product is a combined effort between the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma, and The Cooperative Institute for Research in the Atmosphere (CIRA) in Fort Collins, Colorado, together with the NOAA/NESDIS RAMM Branch.

- Who is receiving this product, and how?

Daily output from NSSL's 4-km WRF-ARW is provided to CIRA, who then generate synthetic satellite imagery, which is sent to the Storm Prediction Center (SPC) via a McIDAS ADDE server. The output is also converted to AWIPS-compatible NETCDF format and provided to the National Weather Service (NWS) Central Region, where a number of NWS offices are displaying it in real-time via AWIPS.

- What is the product size?

Each image is just under 1 MB, and every day 25 images are provided.

2) Product Description:

- Purpose of this product:

The 10.35 minus 12.3 µm difference product is also known as the split window or the longwave difference. The dirty window band (12.3) is subtracted from an IR window band (10.35) to remove the effect of the radiating temperature and expose effects such as emissivity differences and differential absorption by various gases (especially water vapor) and cloud particles. We hope to learn more about the detection of low-level water vapor convergence by viewing this difference during the 2011 severe weather season. The split window difference can also be used for thin cirrus identification, as well as blowing dust (although the WRF doesn't simulate dust so it will not be visible in these loops). As more infomation about this difference product becomes available, we will post it here.

- Why is this a GOES-R Proving Ground Product?

The synthetic imagery is a Proving Ground Product because it replicates how actual features will appear in GOES-R ABI bands.

- How is this product created now?

Every day at 00 UTC, NSSL runs their 4-km WRF-ARW. As soon as the 12-hour forecast is completed, several variables are extracted and scp'ed to CIRA. These variables include temperature, water vapor, and other physical and microphysical parameters which are needed for the next step. When all variables have been receieved at CIRA, an observational operator is run to generate the synthetic imagery for 5 GOES-R ABI bands (6.95, 7.34, 8.5, 10.35, and 12.0 µm). The simulated imagery is then converted to McIDAS AREA format and made avaiable for the SPC, who then makes the output viewable on their NAWIPS system. It is also converted to netcdf format and made available to the NWS to view in AWIPS. Hourly output between 12-12 UTC is processed daily. The resolution of the output is 4-km to match the input resolution of the cloud model; the real GOES-R ABI bands will have 2-km resolution.

3) Product Examples and Interpretation

The synthetic 10.35 minus 12.3 µm loop is available in real-time around by around 16 UTC every day.

4) Advantages and Limitations

Advantages of the synthetic ABI imagery include: 1) Satellite imagery can be viewed before the simulated time actually occurs, so forecasters know what to expect, 2) multiple water vapor bands allow one to view different atmospheric levels since the weighting functions peak at different levels, and 3) forecasters can use this imagery to prepare themselves for what actual GOES-R ABI imagery will look like. The biggest limitation is that the forecast is only as good as the cloud model forecast; if the model does not initiate convection, for example, then the convection will also be absent from the synthetic imagery.