During the summer monsoon, winds move from the Arabian Sea to the coastal parts of western India, while the reverse happens during the winter monsoon.
Yogesh Tiwari, from the Indian Institute of Tropical Meteorology at Pune, and his colleagues used data from two sites in western India, Sinhagad near Pune and Cape Rama at Goa. Harvesting the pre-monsoon crop in Sinhagad seemed to affect CO2 levels, as did long range wind blowing in from the Arabian Sea. The study is scheduled to appear in the 15 August 2014 issue of the Science of the Total Environment.
During April and October, the transition months before the summer and winter monsoons, CO2 remained primarily over the Indian subcontinent and over the northern Arabian Sea.
In July, CO2 is transported in the south-westerly monsoon winds; during winter in January, north-easterly monsoon winds from the Tibetan plateau turn it around.
Mapping out the sources and sinks for CO2 and other GHGs during the two monsoons and calculating the time for which they stay over oceanic and land regions is important to understanding the carbon cycle of the region, the authors say in their study.
“The CO2 variability at other places is currently under investigation — in the east coast and central parts of India,” says Tiwari.
According to the findings of the study, more spatio-temporal (involving time and space) observations over the subcontinent are required to further understand the chemistry associated with GHG sinks.
Jayaraman Srinivasan from the Centre for Atmospheric and Ocean Sciences at the Indian Institute of Science, Bangalore, agrees that for further insight data from more stations is needed.
Srinivasan attributes the decrease in CO2 during the monsoon to “more mixing in the boundary layer when the wind speeds are higher.”
“The net trend would be more of practical interest in terms of deforestation of the Ghats and what that may mean for carbon sequestration and the impact of warming and precipitation changes on the net carbon uptake by the forests,” says Raghu Murtugudde of the University of Maryland in the US.
> Link to the study in Science of The Total Environment
This article has been produced by SciDev.Net's South Asia desk.