Atmospheric Physics and Chemistry Group

Sudhanshu Pandey

Research Interests

Inverse modeling technique is used to translate satellite and ground based observations into corresponding emissions of greenhouse gases at the Earth’s surface. However, in the case of long-lived greenhouse gases, such as methane,  it is a challenge for the satellites to meet the required level of accuracy. A successful method is the so-called proxy retrieval (Butz et al., 2011), which yields the ratio of the total column averaged mixing ratios of CH4 and CO2. In the past, this ratio has been used to study the global sources and sinks of CH4. To account for the contribution of CO2 to the measured CH4/CO2 ratio, CO2 concentrations  fields were used from a model (for example CarbonTracker). Systematic errors in satellite data, e.g. due to atmospheric scattering,  affect both carbon dioxide and methane similarly. Hence, taking the ratio largely eliminates this error. It is assumed that the contribution of carbon dioxide is understood well enough to use this method for studying methane. However, with the improved measurement quality obtained using the GOSAT instrument this assumption is starting to become an important limitation (Schepers et al., 2012).

I work on a new inverse modeling method ( ‘ratio’ method) based on the 4DVAR technique (Meirink et al., 2008). The aim is to optimize the ratio of methane and carbon dioxide, i.e. without translation to CH4 assuming the prior values of carbon dioxide. This approach of using proxy retrievals to optimize both methane and carbon dioxide allows us to make use of the powerful proxy retrieval approach, without biasing the inversion-derived flux estimates by imposing constraints on CO2 derived from a model. 

Posters

 

Presentations