Atmosphere
EarthÔÇÖs climate is influenced Prof.oundly by anthropogenic greenhouse gas (GHG) emissions. Climate forecasts are needed so that we can prepare, mitigate and adapt to the changing climate. The forecasts require accurate information about the sources and sinks of natural and anthropogenic GHGs, in particular, carbon dioxide (CO2) and methane (CH4). Presently, GHG concentrations are observed using ground-based and satellite observations. While local sources can be observed using accurate in-situ measurements, remote sensing methods from satellites are needed to obtain global and regional coverage, which are important for climate research. A number of studies have indicated that uncertainties in regional CO2 and CH4 surface fluxes can be significantly reduced with global, unbiased, precise space-borne measurements which can lead to a more complete understanding of the CO2 and CH4 budget. The accuracy requirements of satellite remote sensing of atmospheric composition and, in particular, GHGs are challenging. Validation of measurements and their uncertainties and continuous development of retrieval methods are important for the success of satellite remote sensing systems, especially for GHGs where error requirements are demanding. Furthermore, sophisticated data assimilation methods and atmospheric transport models are needed to link atmospheric concentration to the underlying surface fluxes. The main objectives of this research project is to use a combination of ground-based measurements of CO2 and CH4 and data from current satellite observations (TanSat, GOSAT/-2, OCO-2/-3 and TROPOMI) to validate and evaluate satellite retrievals with retrieval intercomparisons, to assess them against model calculations and to ingest them into inverse methods to assess surface flux estimates of CO2 and CH4. The main geographic focus will be China but we will also take advantage of our global view provided by the space-borne data. Furthermore, we will look towards future observing systems from Europe and China. Specifically, we will use TCCON and Chinese ground-based measurements and extend the validation previously applied. AirCore Prof.ile observations of GHGs at Sodankyl├ñ will be used to support the validation at high latitudes. We will apply two independent retrieval algorithms available at University of Leicester and IAP to intercompare and advance retrieval methods. We will use the GEOS-Chem atmospheric transport model combined with Ensemble Kalman Filter to infer flux estimates of Chinese CO2 and CH4. No extra funding for this project is presently available. Work by both teams will be part of the normal scientific research. The Chinese team is funded by MOST and CAS, from which a limited amount of funding could be used to support international cooperation research. University of Leicester and University of Edinburgh will carry out the work using existing resources and by synergies with ongoing research projects funded by the National Centre for Earth Observations NCEO, NERC, ESA and the EU and the Finnish Meteorological Institute will use existing resources from the projects funded by the Finnish Academy, ESA and the EU.
