Impact of TAMDAR data on RUC short-range forecasts

Over the last couple of years NOAA/ESRL/GSD, along with other groups, has been evaluating a new airborne sensor deployed on commercial aircraft, known as TAMDAR, for Troposheric AMDAR (Aircraft Meteorological Data Relay). TAMDAR adds the critical measurement of moisture to wind and temperature observations in the vertical. In addition, the instrument, developed and deployed by AirDat, LLC, a private firm located in Raleigh, North Carolina, in part through funding from NASA, has been deployed experimentally on smaller aircraft that fly lower than the larger commercial jets and service many more airports than the ACARS fleet. Thusfar the experimental data has flown on commercial airlines in an area that stretches from the eastern Dakotas to the Ohio Valley and south to portions of the Gulf states. This has provided more en route mid-tropospheric reports and sites for ascent/descent soundings than had previously been available. This new data has been available to NWS forecasters, who have found it to be very useful for a range of short-range forecast problems (the NWS WFO at Green Bay, Wisconsin has been an NWS focal point for the TAMDAR effort, and documentation of a number of cases can be found at http://www.crh.noaa.gov/tamdar).

In addition to a subjective evaluation of the use of TAMDAR data for forecasting, we have also been monitoring the potential impact of TAMDAR data on numerical weather prediction using a 20-km horizontal grid resolution version of the Rapid Update Cycle (RUC) model. Identical versions of the model have been run out to 12 h with and without TAMDAR for over two years, accumulating statistics by verifying against RAOBS. We have also examined individual cases for impact on forecasts of aviation variables such as ceiling and visibility, as well as forecasts of precipitation. In this paper we will emphasize the precipitation cases, some of which were for high impact weather events in the TAMDAR region. An overview of the TAMDAR project and data will also be given, which should be of interest to the forecasting community, especially since TAMDAR coverage is on schedule to expand into the western states later this year, with further expansion likely to follow, as the evaluation of the program continues.