The Integrated Terminal Weather System (ITWS) incorporates many sensors into a user-friendly format to be interpreted by air traffic specialists who have little or no training in meteorology. The system integrates radar data from all Terminal Doppler Weather Radars (TDWR), Next Generation Weather Radars (NEXRAD), and the weather channel from the Airport Surveillance Radars (ASR-9) within the TRACON. The user sees ASR-9 radar data within the TRACON range (about a 60 nm radius around the airport) and a composite NEXRAD reflectivity product for long range reflectivity data (seen when the system is set to a range or 100 nm range or more). Because of basic differences between the ASR-9 and NEXRAD radars, the two reflectivity products can have differences as great as two to three Video Integrator and Processor (VIP) levels. Studies conducted over the past two years have concluded that the NEXRAD composite reflectivity product generally overestimates the overall reflectivity of cells while the fan beam ASR-9 underestimates it. This situation has caused some confusion for users of the ITWS system and concern on the part of system safety monitors.
Based on previous research done at MIT Lincoln Laboratory, we have devised a way in which the NEXRAD pencil beam radar data can be more accurately compared to the ASR-9 fan beam data. We have studied cases where two to three VIP level differences were observed between cells in the NEXRAD and ASR-9 precipitation maps. We then compared these data to a derived Vertically Integrated Liquid water (VIL) map by converting the NEXRAD VIL data into a comparable six level VIP map. We have seen in initial studies that the NEXRAD VIL product, displayed using a six level map, compares very well to the data of the ASR-9 fan-beam radar. Because both products (ASR and VIL) incorporate the vertical structure of echoes, this data also is more relevant to the aviation community. Our study will compare the NEXRAD composite reflectivity product to that of the NEXRAD VIL for several cases in which the ASR-9 and NEXRAD six level reflectivity product differ by more then one VIP level. We will also examine the vertical profile and echo top information for each cell. It is our intention to show that the NEXRAD VIL product would be a more realistic weather representation to use for long range reflectivity in the ITWS system then the currently used composite product. We will also discuses the benefits and drawbacks to using the NEXRAD VIL product in place of the composite reflectivity product.
* This work was sponsored by the Federal Aviation Administration. The views expressed are those of the authors and do not reflect the official policy or position of the U.S. Government.
+ Opinions, interpretations, conclusions and recommendations
are those of the authors and are not necessarily endorsed by the United
States Air Force
The 8th Conference on Aviation, Range, and Aerospace Meteorology