Greenhouse gas relationships in the Indian summer monsoon plume measured by the CARIBIC passenger aircraft 1Atmospheric Chemistry Division, Max Planck Institute for Chemistry, Mainz, Germany
2Royal Netherlands Meteorological Institute, de Bilt, The Netherlands
3Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
Received: 07 January 2010 – Published in Atmos. Chem. Phys. Discuss.: 01 February 2010 Abstract. During the Indian summer monsoon period 2008, regular measurement flights were
performed by the CARIBIC aircraft between Germany and India.
Measurements included whole air sampling and subsequent analysis
for greenhouse gases (CH4, CO2, N2O, SF6) and in-situ measurements
of CO, O3, and H2O. For all these tracers a distinct monsoon signature was observed
in the longitude range 50–80° E south of 40° N at flight altitudes 8–12.5 km.
The formation of a monsoon plume with enhanced
mixing ratios was observed for CH4, N2O, SF6, CO and H2O.
The plume began to develop in May and persisted through September, and maximum mixing
ratios and maximum spatial extension of the plume were observed in August.
For CO2 and O3 a minimum was observed. The amplitude
of the CO2 seasonal cycle was larger than at comparable latitudes outside the monsoon
region, and the CO2 spring maximum was observed with a delay of one month.
Different tracer relationships show strong spatial variations across the plume.
The comparison with NOAA ground station data shows a clear enhancement
for CH4, N2O, SF6 and CO and a decrease in CO2 mixing ratios.
Assuming seasonally invariant SF6 emissions based on the EDGAR 4.0 inventory,
monthly emissions were estimated for the period June–September
for CH4, N2O, and CO, and the CO2 uptake was estimated.
While for N2O an emission decrease during the monsoon period was derived,
emissions of CH4 were highest in September indicating a different seasonal cycle of emissions.
Net CO2 uptake by the vegetation was largest in September.
Revised: 12 April 2010 – Accepted: 14 April 2010 – Published: 27 April 2010
Citation: Schuck, T. J., Brenninkmeijer, C. A. M., Baker, A. K., Slemr, F., von Velthoven, P. F. J., and Zahn, A.: Greenhouse gas relationships in the Indian summer monsoon plume measured by the CARIBIC passenger aircraft, Atmos. Chem. Phys., 10, 3965-3984, doi:10.5194/acp-10-3965-2010, 2010.