Diurnal and seasonal variations of atmospheric CO2 over Trivandrum, India

Continuous measurements of CO2 mixing ratio and meteorological parameters have been made in National Centre for Earth Science Studies (NCESS), Trivandrum (8.5°N 76.9°E) from June 2014 to May 2015 and analyzed the diurnal and seasonal variation of CO2 mixing ratio. The average atmospheric CO2 during study period was 321±14.78 ppm. The diurnal variation with a maximum during the early morning and late night and a minimum in the afternoon is clearly observed. Photosynthetic activity and the atmospheric boundary layer play an important role in diurnal variation of CO2. The analysis of its seasonal trend indicated that highest value of CO2 mixing ratio was found in summer (382 ppm) and the lowest during monsoon (274.3 ppm) season. The mean day –night ratio (D/N) for the study period was 0.94. All the months the night time concentration is higher than the day time concentrations since Photosynthetic activity is higher during day time. Wind speed plays a dominant role in controlling the CO2 mixing ratios at this station.