TES carbon monoxide validation during two AVE campaigns using the Argus and ALIAS instruments on NASA's WB‐57F

The Aura Validation Experiment (AVE) focuses on validating Aura satellite measurements of important atmospheric trace gases using ground‐based, aircraft, and balloon‐borne instruments. Global satellite observations of CO from the Tropospheric Emission Spectrometer (TES) on the EOS Aura satellite have been ongoing since September 2004. This paper discusses CO validation experiments during the Oct‐AVE (2004 Houston, Texas) and CR‐AVE (2006 San Jose, Costa Rica) campaigns. The coincidences in location and time between the satellite observations and the available in situ profiles for some cases are not ideal. However, the CO distribution patterns in the two validation flight areas are shown to have very little variability in the aircraft and satellite observations, thereby making them suitable for validation comparisons. TES CO profiles, which typically have a retrieval uncertainty of 10–20%, are compared with in situ CO measurements from NASA Ames Research Center's Argus instrument taken on board the WB‐57F aircraft during Oct‐AVE. TES CO retrievals during CR‐AVE are compared with in situ measurements from Jet Propulsion Laboratory's Aircraft Laser Infrared Absorption Spectrometer (ALIAS) instrument as well as with the Argus instrument, both taken on board the WB‐57F aircraft. During CR‐AVE, the average overall difference between ALIAS and Argus CO was 4%, with the ALIAS measurement higher. During individual flights, 2‐min time‐averaged differences between the two in situ instruments had standard deviation of 14%. The TES averaging kernels and a priori constraint profiles for CO are applied to the in situ data for proper comparisons to account for the reduced vertical resolution and the influence of the a priori in the satellite‐derived profile. In the TES sensitive pressure range, ∼700–200 hPa, the in situ profiles and TES profiles agree within 5–10%, less than the variability in CO distributions obtained by both TES and the aircraft instruments in the two regions. TES CO is slightly lower than in situ measurements in the Houston area (midlatitudes) and slightly higher than in situ CO measurements in the Costa Rica region (tropical).