Senior Research Scientist
Science and Technology Corporation
Madison, WI 53705

STC e-mail: baum at


Active projects:

Principal Investigator and NASA Suomi-NPP Science Team Leader

I am serving as both a Principal Investigator on a data fusion project and the NASA Suomi-NPP Science Team Leader.

MODIS has three bands sensitive to carbon dioxide around 4.3 µm,  another four around 15 µm, 2 bands sensitive to water vapor near 6.7 µm, and a band sensitive to ozone near 9.7 µm. Unfortunately, VIIRS has none of these IR bands affected by atmospheric absorption, which results in a degradation of the accuracy of the cloud products (cloud mask, cloud top pressure/height and thermodynamic phase) and the moisture products (total precipitable water vapor, upper tropospheric humidity). The lack of at least one IR absorption channel on VIIRS degrades the accuracy of the cloud mask, cloud top pressure/height, and cloud thermodynamic phase products. These IR absorption bands have a variety of other uses in both operational products (such as total precipitable water, or TPW) and applications such as volcanic plume tracking, inference of polar winds, and more.

Our team (including Elisabeth Weisz and Paul Menzel at UW-Madison) developed a method to construct infrared absorption bands for VIIRS at 750-m spatial resolution. The imager-sounder fusion technique uses VIIRS and CrIS (Cross-track Infrared Sounder) data to construct the missing bands at high spatial resolution. Our fusion software is now fully integrated at the Atmosphere SIPS and is running daily in forward stream operations. The VIIRS fusion radiances are available in a NASA VIIRS Level-2 granule (NetCDF4) that provides 6 minutes of data. Each fusion granule provides IR radiances constructed using the spectral response functions for Aqua MODIS channels 23, 24, 25, 27, 28, 30, 33, 34, 35, and 36. The granules also provide radiances for VIIRS bands M15 and M16. The reason for including fusion-based VIIRS channels M15 and M16 is to compare measured-to-fusion IR window channel radiances at the pixel level. This can provide pixel-to-pixel error statistics necessary for optimal estimation algorithms.

The full record of VIIRS-CrIS fusion radiances is available for both the Suomi-NPP and NOAA-20 (JPSS-1) platforms. The fusion products and supporting documentation are available at the Level-1 and Atmosphere Archive & Distribution System (LAADS; NASA Goddard Space Flight Center). The following links provide access to users interested in acquiring these products, which are free of charge. All users need to register with NASA Earthdata to obtain a login account through the NASA User Registration System (URS) page ( For additional help on any aspect of searching for or acquiring these products, contact LAADS User Services.

Any feedback would be greatly appreciated as it will be of immense help for improving the process, and we hope that you will find this to be useful in your work.

Links to the Fusion Product and Documentation at LAADS 

1. The VIIRS+CrIS Fusion product page provides an overview and documentation

2. To perform a specific geographical search for the S-NPP VIIRS+CrIS fusion product

3. To perform a specific geographical search for the NOAA-20 VIIRS+CrIS fusion product

4. Direct access to the S-NPP VIIRS+CrIS fusion product archive

5. Direct access to the NOAA-20 VIIRS+CrIS fusion product archive

Radiances are provided for the full VIIRS scan swath but as noted in our 2017 paper, the radiances outside the sounder swath have a small warm bias. We do not correct for additional water vapor absorption for VIIRS pixels outside of the sounder swath. Also note that the deleted bowtie pixels are replaced with nearest neighbor values for those algorithms that depend on pixel arrays.

More information on the VIIRS-CrIS fusion project is available on our Data Fusion site.

Spectral Ice Cloud Bulk Scattering Models Available

This long-term effort to construct ice cloud bulk single-scattering property models wrapped up in 2014. My colleagues (Dr. Ping Yang at Texas A&M University and Dr. Andrew Heymsfield at NCAR) and I hope these models are useful and that you will share with us what you have done with them.

Spectral models from the UV to the Far-IR in NetCDF: Provides access to ice cloud bulk scattering models at each of 445 discrete wavelengths ranging from 0.2 µm to 100 µm, both with and without the full phase matrix. Individual sets of spectral models are provided based on (1) solid columns only, (2) the aggregate of solid columns only, and (3) a general habit mixture that employs nine ice habits (droxtals, plates, solid/hollow columns, solid/hollow bullet rosettes, small/large aggregate of plates and an aggregate of columns). These models are based on randomly oriented particle calculations for severely roughened ice particles. Details are provided in Baum et al. (2014, JQSRT - preprint available on my publication page).

A netCDF file for each set of models is available that provides microphysical and single-scattering properties including the full phase matrix; each is about 55 MB compressed.

Separate files are also available that provide the spectral models over the full wavelength range but without the phase matrix (i.e., only the asymmetry parameter is provided). These files are quite small, about 250 KB each.

Imager Models: Provides access to bulk scattering models for about 36 different polar-orbiting and geostationary imagers; models include integration over the imager-specific channel spectral response functions and are based on severely roughened ice particles. Models provide the intensity (i.e., the scattering phase function) but not the full phase matrix.

Microphysical Data: Provides access to the in situ data for more than 14,000 particle size distributions from 11 field campaigns (and increasing over time).

Shortwave Spectral Models: Provides access to ice cloud bulk scattering models at individual wavelengths from 0.4 µm to 3 µm in wavelength at 0.01 µm resolution; based on severely roughened ice particles. Models provide the intensity (i.e., the scattering phase function) but not the full phase matrix.