Remote sensing of greenhouse gases in the air over Jinja, Uganda

A new ground-based measurement site in Uganda, set up by the University of Leicester in partnership with NaFIRRI, will provide a unique dataset of remotely sensed greenhouse gas observations over a period of several months.

From the 16th to 22nd of January 2020, Dr Neil Humpage (Earth Observation Science) visited Jinja, Uganda, to set up a Bruker EM27/SUN spectrometer which will make measurements of greenhouse gases in the atmosphere overhead during the coming months. The spectrometer deployment is the result of a partnership between the University of Leicester and the National Fisheries Resources Research Institute (NaFIRRI), who are hosting the spectrometer at their headquarters in Jinja, as part of the NERC funded Global Methane project (see https://moya.blogs.bris.ac.uk/ for more info).

The spectrometer works by observing light from the Sun, which it splits onto a fine wavelength grid to produce absorption spectra of the atmosphere. From these measured spectra, acquired at a rate of one every 75 seconds when the sky is cloud-free, we can derive the concentrations of carbon dioxide, methane, and carbon monoxide in the column of air overhead. We expect that the methane measurements in particular should be very interesting, as the scientific community are still trying to understand the relative importance of the many different processes – both natural and human – which are affecting recent trends in global concentrations of atmospheric methane. Tropical wetlands are one of the most important natural sources of methane, which makes Uganda an excellent location for this study. In addition to our interest in methane, our capability to measure carbon dioxide and carbon monoxide can give us an impression of Uganda’s greenhouse gas emissions from fossil fuel consumption, transport, and fires.

A further motivation for making these measurements in Uganda is to provide a validation dataset for our Earth Observation Science colleagues, who rely on ground-based validation measurements to provide confidence in the quality of the global greenhouse gas datasets they derive from satellite observations. The established ground-based spectrometer networks (e.g. the Total Column Carbon Observing Network, or TCCON) unfortunately do not include any locations at all on the continent of Africa. By temporarily filling this gap, the dataset we produce from our spectrometer measurements in Jinja should prove to be of great value to the global greenhouse gas remote sensing community.