Validation of TES methane with HIPPO aircraft observations: implications for inverse modeling of methane sources
1Harvard University, Department of Earth and Planetary Sciences, Cambridge, MA, USA
2Jet Propulsion Library/California Institute of Technology, Pasadena, CA, USA
3University of Colorado at Boulder, Department of Mechanical Engineering Boulder, CO, USA
4Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, USA
5Atmospheric Environmental Research, Lexington, MA, USA
*now at: NOAA Climate Program Office, Silver Springs, MD, USA
Abstract. We validate satellite methane observations from the Tropospheric Emission Spectrometer (TES) with 151 aircraft vertical profiles over the Pacific from the HIAPER Pole-to-Pole Observation (HIPPO) program. We find that a collocation window of ±750 km and ±24 h does not introduce significant error in comparing TES and aircraft profiles. We validate both the TES standard product (V004) and an experimental product with two pieces of information in the vertical (V005). We determine a V004 mean bias of 65.7 ppb with residual standard deviation of 44.2 ppb. For V005 we determine mean biases (residual standard deviations) in the lower and upper troposphere of 18.2 (31.1) and 49.4 (33.2) ppb, respectively. TES errors show no significant dependence on latitude or surface type. Even when V005 cannot retrieve two pieces of information it still performs better than V004. An observation system simulation experiment (OSSE) with the GEOS-Chem chemical transport model (CTM) and its adjoint shows that TES V004 has only limited value for constraining methane sources. Our successful validation of V005 encourages its production as a standard retrieval to replace V004.