On the Use of Routine Airborne Observations for Evaluation and Monitoring of Satellite Observations of Thermodynamic Profiles

Abstract. Satellite-based observations require independent sources of data to monitor and evaluate their precision and accuracy. For the temperature and water vapor profiles produced by satellite-based sounders, this often results in comparisons to operational radiosondes. However, polar-orbiting satellite overpasses are frequently misaligned with the global synoptic launch times. The routine airborne in situ observations of temperature and water vapor from the Airborne Meteorological Data Relay (AMDAR) program and Water Vapor Sensing System-II (WVSS-II) instrument greatly enhance opportunities for making precise matchups due to the far greater temporal frequency and spatial density of aircraft flights. The potential for the use of aircraft-based observations as a source for evaluation of tropospheric satellite sounder profiles is explored through a year-long intercomparison with the IASI Level 2 profiles produced from both the Metop-A and Metop-B satellites. Results using 1 h and 50 km match criteria indicate good agreement between the satellites and the aircraft-based observations with temperature, specific humidity, and relative humidity biases generally less than 0.5 K, 0.8 g kg-1, and 5 % respectively; both IASI instruments perform nearly identically. While the intercomparisons are generally limited to the troposphere as aircraft typically reach their maximum height at the tropopause, the substantially larger number of intercomparison points enable characterization as a function of season, scan angle, and other characteristics heretofore unexplored due to a lack of validation data.