Commercial aircraft now provide more than 160,000 observations per day of wind and temperature aloft over the contiguous United States. The general term for these data is AMDAR (Aircraft Meteorological Data Reports). These data have been shown to improve both short- and long-term weather forecasts, and have become increasingly important for regional and global numerical weather prediction (Moninger, et al. 2003). Two shortfalls of the current AMDAR data set are the absence of data below 25,000 ft between major airline hubs and the almost complete absence of water vapor data at any altitude. To address these deficiencies, a sensor called TAMDAR (Tropospheric AMDAR), developed by AirDat, LLC, under sponsorship of the NASA Aviation Safety and Security Program, has been deployed on approximately 50 regional turboprop aircraft flying over the middle US (Daniels, et al. 2006). These turboprops are operated by Mesaba Airlines (doing business as “Northwest Airlink”). The aircraft cruise at lower altitudes (generally below 500 hPa) than traditional AMDAR jets, and into regional airports not serviced by AMDAR jets. Like the rest of the AMDAR fleet, TAMDAR measures winds and temperature. But unlike most of the rest of the fleet, TAMDAR also measures humidity, turbulence, and icing. By 2008, AirDat expects to have more than 400 aircraft operating with TAMDAR in the U.S. ESRL’s Global Systems Division (GSD) has built an extensive system for evaluating the quality of TAMDAR and AMDAR data, and has applied this system for the 2.5 years that TAMDAR has been in operation. Our evaluation system relies on the Rapid Update Cycle (RUC) numerical model and data assimilation system (Benjamin, et al.2004a,b, 2006a). Under FAA sponsorship, NOAA/ESRL/GSD is performing a careful TAMDAR impact experiment. The RUC is well-suited for regional observation impact experiments due to its complete use of hourly observations and diverse observation types. We report here on statistical measures of forecast improvement; a companion paper by Szoke et al. (2007) discusses several case studies in detail.
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