Commercial aircraft now provide more than 170,000 observations per day of winds and temperature aloft over the contiguous United States. The general term for these data is AMDAR (Aircraft Meteorological Data Relay). These data have been ingested into the Rapid Update Cycle (RUC) for more than a decade, and have been shown to improve forecasts.

One weakness of the current AMDAR data set is the absence of data below 25,000 ft between major airline hubs and the almost complete absence of water vapor data. To address this weakness, a sensor called TAMDAR (Tropospheric Airborne Meteorological Data Reporting), developed by AirDat, LLC, under NASA sponsorship, has been deployed on several fleets of regional aircraft. Like the rest of the AMDAR fleet, TAMDAR measures winds and temperature. But unlike most of the rest of the fleet, TAMDAR measures humidity, turbulence, and icing. By late 2009, AirDat expects to have more than 400 aircraft operating in the contiguous U. S. and Alaska.

Over the past 4 years, NOAA/ESRL/GSD has evaluated TAMDAR's data quality (as compared with traditional AMDAR measurements) and its impact on RUC forecasts. To measure TAMDAR impact, we run two identical RUC cycles in real-time: one with TAMDAR and one without—otherwise both use the same input data. These cycles use up-to-date assimilation/model techniques (generally corresponding to the 13km RUC, but run at 20km resolution), and incorporate all observation types (as used in the RUC13) except radar, including cloud analysis (GOES and METAR), full METAR assimilation with effects of boundary-layer depth, GOES precipitable water, all other aircraft, profiler (NOAA and 915-MHz boundary layer), and rawinsondes. With its hourly assimilation and full use of other observations, the RUC provides a stringent assessment for forecast value added by TAMDAR. The parallel models are strictly controlled to isolate the effects of TAMDAR data, including a resetting of common initial conditions every 48h to ensure a full control.

For the first 3.5 years, we evaluated the data quality and impact of approximately 55 TAMDAR-equipped turboprop aircraft flying over the Midwest on Mesaba airlines. Data from these aircraft improve RUC forecasts of temperature, humidity, and wind. These sensors continue to report data and are now an operational part of the National Weather Service data stream.

Recently, TAMDAR sensors have been installed on regional jet aircraft operated by Chautauqua Airlines in the Gulf Coast, southern Midwest and eastern U.S. These jet aircraft fly higher and faster than Mesaba turboprops do. We will therefore update our previous TAMDAR studies to include these new aircraft, with particular emphasis on relative humidity measurements above 20,000 ft. We will consider both data quality, as measured with respect to RUC background fields, and TAMDAR impact on RUC forecast quality.