Skew-T plotting tool disclaimer

This Skew-T diagram visualization web site is provided free of charge as a teaching reference for educators and weather enthusiasts around the world. The data shown here are based on simultaneous observations by the Atmospheric Infrared Sounder (AIRS) and its sister instrument, the Advanced Microwave Sounder Unit A (AMSU-A), both in near-polar Earth orbit aboard the NASA Aqua spacecraft since May 4, 2002. Derived vertical profiles of air temperature and water vapor concentrations are then processed using standard industry-wide meteorological definitions and formulas, using no more than middle school level mathematics. The very latest data files, covering the last several days, are downloaded several times in a 24-hour period and processed immediately for your convenience. These same data files are available to the general public through a centralized NASA data repository, along with rudimentary programs (code fragments) in various commercially-available programming languages to extract the data for calculations.

This Skew-T plotting tool enables you to browse weather data anywhere in the world (at least twice per day in most locations). It is NOT a research-grade software application, although the data which it reads are of this caliber. The researcher interested in AIRS data should contact the person specified for this purpose at the above-mentioned AIRS public web site. Please be aware that these data files contain substantial amounts of quality control and precision indicators that are essential to using the AIRS data in any serious scientific investigation. This Skew-T web application takes a conservative approach in converting these AIRS/AMSU-A observations into a Skew-T-appropriate data set. Therefore, for every six-minute period of time covering a particular ground track, a selected subset of the possible 1,350 individual observations may not be available. In addition, the algorithms that reconstruct the air temperature and water vapor profiles sometimes have difficulty over stretches of land or in the presence of very thick low-lying clouds.

The challenges experienced by AIRS in "retrieving" realistic atmospheric data are outlined in a paper published for the American Meteorological Society by AIRS scientists at the Jet Propulsion Laboratory. In these instances, even though the data may be available, the SkewT diagram will display a cautionary message and some of the descriptive Skew-T parameters will be set to "N/A" (not available) to denote that the observation may contain unrealistic properties or are not appropriate for a particular observation (e.g., measurement of storm energy where no storm conditions exist). Specifically, reference is made to "super-adiabatic temperature changes", meaning that a rapidly rising parcel of air is changing temperature much more quickly than could be explained by regular weather processes. The improvement of this algorithm, especially at very low altitudes over land, is the subject of much current research.

We invite you to explore this fascinating and comprehensive weather database. You may also wish to inquire about the AIRS instrument in general, or climate research in general at the ASK AIRS section of the web site. As always, your comments, suggestions and feedback are greatly appreciated.

Acknowledgements

The Skew-T web application and associated graphical interfaces were developed by Stephen Licata with the assistance of Dr. Eric Fetzer, Dr. Bjorn Lambrigsten, Dr. Edward Olsen, and Ms. Sharon Ray. The AIRS project and associated education outreach efforts presented through this web site were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.