Comparisons of satellite (GOSAT) and ground-based spectroscopic measurements of CH4 content near Saint Petersburg: influence of data collocation

Abstract

We compared atmospheric column average mole fractions of methane measured with ground-based Fourier transform spectroscopy at the Physical Department of Saint Petersburg State University (59.9° N, 29.8° E) in years 2009–2012 with similar data obtained from the Japanese Greenhouse Gases Observing Satellite (GOSAT) satellite. For the GOSAT data version V02.xx, average and median values of biases between satellite and ground-based methane mole fractions are −(1.7–4.1) ppb and their standard deviations are 10–13 ppb. These values are similar to biases between the GOSAT satellite and the ground-based Total Carbon Column Observation Network and Network for the Detection of Atmospheric Composition Change making Fourier transform spectroscopic observations. Average and median biases for satellite data selected within α = ±1° latitude–longitude vicinity from the ground-based observations site are smaller than those for α = ±3° and α = ±5°.