Reconstructing high-resolution in-situ vertical carbon dioxide profiles in the sparsely monitored Asian monsoon region

Atmospheric concentrations of the greenhouse gases carbon dioxide and nitrous oxide have increased substantially because of human activities. However, their sources in South Asia, which contribute strongly to the accelerating global growth of carbon dioxide and nitrous oxide, are poorly quantified. Here, we present aircraft measurements with high temporal and vertical resolution up to 20 km during the Asian summer monsoon where rapid upward transport of surface pollutants to greater altitudes occurs. Using Lagrangian model simulations, we successfully reconstruct observed carbon dioxide profiles leading to an improved understanding of the vertical structure of carbon dioxide in the Asian monsoon region. We show that spatio-temporal patterns of carbon dioxide on the Indian subcontinent driven by regional flux variations rapidly propagate to approximately 13 km with slower ascent above. Enhanced carbon dioxide compared to the stratospheric background can be detected up to 20 km. We suggest that the propagation of these signals from the surface to the stratosphere can be used to evaluate transport models and assess carbon dioxide fluxes in South Asia. Lagrangian model simulations successfully reconstruct vertical carbon dioxide profiles obtained by high resolution aircraft measurements during the Asian summer monsoon in a region of rapid upward transport of surface pollutants to altitude, allowing better pollutant source attribution.

Automated summary

Human activities have significantly increased the concentrations of carbon dioxide and nitrous oxide in the atmosphere. However, the sources of these gases in South Asia, which contribute to the global growth of carbon dioxide and nitrous oxide, are not well quantified. This study uses aircraft measurements and Lagrangian model simulations to reconstruct carbon dioxide profiles and understand the vertical structure of carbon dioxide in the Asian monsoon region. The findings suggest that the signals from surface to stratosphere can be used to evaluate transport models and assess carbon dioxide fluxes in South Asia.