Part of the CIMSS Web

CIMSS is pleased to announce the release of version 3.0 (beta) of the International ATOVS Processing Package (IAPP). The software operates in the Unix environment on IBM, SGI, and Sun workstations, and in the Linux environment on Intel-based and similar computers. Documentation is included with the software, describing how to install the IAPP, the design structure, and how each module operates.

IAPP v3.0 (beta) has been designed to work with the HIRS level 1-D output file that is produced by the AAPP (ATOVS and AVHRR Preprocessing Package). The AAPP was developed under the auspices of EUMETSAT; distribution is currently handled by the UK Meteorological Office. For information on the AAPP, and how to obtain it, see

Below is a short description of the IAPP contents, licensing issues, and how to obtain the package.

IAPP Contents

The IAPP can use radiances from HIRS-3, AMSU-A, and AMSU-B on the NOAA-15 through NOAA-18 spacecraft, preprocessed into the AAPP level 1-D format, for retrieval of atmspheric parameters.

NOTE: on NOAA-18, the infrared instrument is actually HIRS-4, and the microwave moisture instrument is now called MHS. To avoid extra "bookkeeping" the HIRS radiative-transfer coefficients have been incorporated into the files whose names begin with "hirs3", and the MHS coefficients have been incorporated into the files whose names begin with "amsu". In the context of the IAPP retrieval software, the new instrument names have no real significance.

Ancillary data inputs for retrieval are high resolution topography (supplied), surface observations (see below) and numerical model data (see below). The IAPP performs temperature, moisture, and ozone retrieval calculations on a 3x3 HIRS field of view (fov) matrix, or field-of-regard (FOR). HIRS and AMSU-A radiances/brightness temperatures are used for clear/cloudy fov determination. Depending on clouds, a HIRS + AMSU-A + AMSU-B retrieval, an AMSU-A + AMSU-B (i.e., no-HIRS) retrieval, or no retrieval is made for each FOR. The output file is in netCDF format. Detailed information is provided in the documentation.

Surface data in the WMO Metar format is used, if available, to improve surface condition definition. If surface observations are not available, numerical model data is used (see next item) to define surface conditions, or, with neither available, window channel radiances are used to best approximate surface conditions. We strongly recommend using NWP information and/or hourly surface data to better characterize surface conditions in retrieval processing.

Numerical model output can be used as a first guess field for the atmosphere and surface. The NWP netCDF files routinely produced at CIMSS are posted on the SSEC anonymous ftp server -- see the information on the ITPP/IAPP main Web page. Any model can readily be adapted to fit into the IAPP retrieval scheme; clearly written documentation makes this task relatively straightforward. Alternatively, a regression scheme, based on synthetic radiance calculations, can be used to provide a first guess. Again, detailed information is provided in the documentation.


The IAPP source code and supporting fixed datasets have been bundled as Open Source in accordance with the terms of the GNU General Public License http://www.gnu.org/licenses/licenses.html#GPL. The package is freely available under the terms of that License.

Obtaining the IAPP

To download the IAPP, go here: ftp://ftp.ssec.wisc.edu/pub/iapp/release_3.0_beta_20100630/

Please note that in addition to the new version of IAPP, the "decoders" package has also been updated. To insure reliable processing of ancillary information, established users should download and install this software, as well. NetCDF software is no longer supplied with the IAPP and decoder packages; see the IAPP_Readme file for information on obtaining that software from its source.

Information from Users

Feedback on the performance of the system, as well as any problems encountered in installing or running it, is always welcome. and should be addressed to the Technical Contact:

Szuchia L. Moeller
Research Specialist
UW Space Science & Engineering Center
1225 West Dayton Street
Madison, WI 53706-1695
Email : Contact Form

Updated 30-Jun-2010 Space Science and Engineering Center
University of Wisconsin-Madison