Development of Interactive Cloud Height and Skew-T Diagram Algorithms for AWIPS

The Aviation Weather Center (AWC), in cooperation with the Aviation Division of the Forecast Systems Laboratory (FSL), has established an AWIPS facility for local software development. Using FSL source code and executables, AWIPS compatible software was successfully developed at the AWC to estimate cloud tops from satellite and sounding data. The ability to compute cloud heights is one of the AWIPS requirements for the Convective Sigmet Unit, for use in the products it generates. This ability also ranked top in the list of satellite application priorities for build 5.0 established from Regional Offices across the country.

The cloud height algorithm was designed to integrate with AWIPS sampling functionality that displays a continuous read-out of data at the cursor position. Using temperature data that is retrieved by sampling from an IR satellite image, a corresponding sounding (model or observed) is analyzed to compute a given cloud top. As cloud tops are sampled, a read-out of cloud tops at the cursor and the highest cloud tops in the vicinity of the cursor are continuously provided.

As an extension to the cloud height sampling logic, the ability to display the corresponding sounding data in a skew-t diagram was established. The 3 x 3 inch skew-t diagram placed in the upper-left hand corner of the screen updates automatically as one roams the satellite image.

This paper provides an in-depth description of the algorithm used in the interactive cloud height computation. It also describes the use of the interactive sounding display for diagnosing air mass variability.