Measuring greenhouse gases during India’s monsoon

India receives 80% of its annual rainfall in three months – between June and September. There are large year-to-year differences in the strength of the monsoon, which is heavily impacted by drivers such as aerosols and large-scale weather patterns, and this has significant impact on the livelihoods of over a billion people. For example, due to the strong El Nino last year, the 2015 monsoon experienced a 14% lower precipitation than average with some regions of India facing up to 50% shortfall.  Forecasting the timing and strength of the monsoon is critical for the region and particularly for India’s farmers, who must manage water resources to avoid failing crops.

 

The observational campaign, which is part of NERC’s Drivers of Variability in the South Asian Monsoon programme, is led jointly by UK researchers: Professor Hugh Coe (University of Manchester), Dr Andy Turner (University of Reading) and Dr Adrian Matthews (University of East Anglia) and Indian scientists from the Indian Space Research Organization and Indian Institute of Science.

Bristol PhD student Dan Say installing sample containers on the BAe- 146. Image credit: Angelina Wenger

To complement this project to study physical and chemical drivers of the monsoon, I am measuring greenhouse gas from the aircraft with PhD student Dan Say (School of Chemistry, University of Bristol). Dan is gaining valuable field experience by operating several instruments aboard the BAe-146 through the intense heat and rain of the Indian monsoon.

Two of the greenhouse gases that we are studying, methane and nitrous oxide, are primarily produced during the monsoon season from India’s intensive agriculture. Methane is emitted from rice paddies, in which flooded soils create prime conditions for “anaerobic” methane production. Nitrous oxide is also emitted from these flooded soils due the large quantity of fertilizers that are applied, again through anaerobic pathways. 

 

Rice fields near Bangalore, India. Image credit: Guy Gratton.

Our previous understanding of the large-scale emissions of these greenhouse gases from India’s agricultural soils has been limited and we aim to further our knowledge of what controls their production. In addition to the methane concentrations measured on the aircraft, with collaborators at the Royal Holloway, University of London’s isotope facility, we are also measuring the main isotope of methane (the 13-carbon isotope), which will provide us with a valuable tool for differentiating between agricultural and other sources of methane in the region. By combining this information with other measurements from the aircraft (for example, of moisture and of other atmospheric pollutants), we aim to gain new insights on how we may reduce these emissions in the future.

In addition, many synthetic “man-made” greenhouse gases are being measured for the first time in South Asia, giving us the first look at emissions from this region of some of the most potent warming agents. These include the suite of halocarbons such as hydrofluorocarbons (HFCs) and their predecessors the hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs). These gases will be measured on the University of Bristol School of Chemistry’s ‘Medusa’ gaschromatography-mass spectrometer (GC-MS) facility run by Professor Simon O’Doherty.

 

Sample canisters for collecting air that will be measured on the School of Chemistry’s ‘Medusa’ GC-MS facility. Image credit: Angelina Wenger

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This blog is written by University of Bristol Cabot Institute member Dr Anita Ganesan, a NERC Research Fellow, School of Geographical Sciences, who looks at greenhouse gas emissions estimation.