Validation of TES methane with HIPPO aircraft observations: implications for inverse modeling of methane sources

We validate satellite methane observations from the Tropospheric Emission Spectrometer (TES) with 151 air- craft vertical profiles over the Pacific from the HIAPER Pole- to-Pole Observation (HIPPO) program. We find that a col- location 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 exper- imental product with two pieces of information in the ver- tical (V005). We determine a V004 mean bias of 65.8 ppb and random instrument error of 43.3 ppb. For V005 we de- termine a mean bias of 42.3 ppb and random instrument er- ror of 26.5 ppb in the upper troposphere, and mean biases (random instrument errors) in the lower troposphere of 28.8 (28.7) and 16.9 (28.9) ppb at high and low latitudes respec- tively. Even when V005 cannot retrieve two pieces of in- formation 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.