Validation of the ACOS/GOSAT column CO2 data product using ground-based TCCON measurements

Description

The Total Carbon Column Observing Network (TCCON) is a ground-based network of Fourier Transform Spectrometers that make measurements of important atmospheric gases around the world. TCCON instruments measure the column average dry-air mole fractions of CO2, CO, CH4, N2O, and H2O TCCON by observing the absorption of direct sunlight by atmospheric gases in the near infrared (NIR) spectral region. The TCCON includes ARM-sponsored instruments at the Southern Great Plains site in Lamont, Oklahoma, and at Darwin, Australia. Measurements from the TCCON network are a critical component of validating satellite measurements of carbon dioxide. A specific example is the planned use of TCCON data for validating measurements from the Orbiting Carbon Observatory-2 (OCO-2) satellite, which is scheduled to launch in 2013. The validation plan for OCO-2 is based on the one developed for the original OCO instrument that launched in 2009 but failed to achieve orbit due to a launch vehicle malfunction. The validation strategy involves using data from TCCON sites, including the one at the SGP site to connect the space-based data to the World Meteorological Organization (WMO) CO2 standard used with ground-based measurements. This connection is made by validating the satellite data against the TCCON measurements, which are calibrated against aircraft observations (which use the WMO standard). The OCO-2 and TCCON teams are testing their validation plan using data from the TANSO-FTS instrument that was launched aboard the Greenhouse gas Observing Satellite (GOSAT) in 2009 to measure total columns of CO2 (XCO2) and methane (XCH4). The OCO-2 algorithm team is working on retrieving XCO2 from the GOSAT data in an effort called the Atmospheric CO2 Observations from Space (ACOS) using the OCO-2 retrieval algorithm. The ACOS/OCO-2 validation team is using the TCCON data to validate the ACOS retrievals. Some preliminary validation results will be presented in this poster. The full validation strategy for ACOS and OCO-2 and how it uses TCCON data taken at the SGP site and other locations will be described.