Variations of near-surface atmospheric CO_2 and H_2O concentrations during summer on Muztagata

1 Introduction As one of the most important greenhouse gases, atmospheric carbon dioxide (CO2) has increased in concentration rapidly since preindustrial times1―4] and significantly contributes to the climate change5] caused by anthropogenic emissions. Documentation of the global carbon cycle has been critical for under-standing the causative relationships between green-house gases and climate change. For example, the CO2 level in the atmosphere has been monitored at many sites worldwide …

Variations of near-surface atmospheric CO2 and H2O concentrations during summer on Muztagata

Expeditions during the summers of 2002 and 2003 implemented continuous monitoring of near-surface (2 m height) atmospheric CO2 and H2O concentrations at the 4500 m elevation on Muztagata. The resultant data sets reveal a slight decrease of CO2 concentrations (of about 5μmol·mol-1) and changes in the diurnal variations from the end of June to the middle August. The daily maximum CO2 concentrations occur between 02:30―05:30 AM (local time) and the minimum levels occur between 12:00―15:30 PM. The atmospheric CO2 concentrations in the summer of 2002 were around 5μmol·mol-1 lower than those during the same period of 2003, whereas the diurnal amplitude was higher. In contrast, we found that the daily mean atmospheric H2O content in 2003 was much lower than that in 2002 and there exists a striking negative correlation between CO2 and H2O concentrations. We therefore suggest that the near-surface atmospheric CO2 concentration is affected not only by photosynthesis and respiration, but also by the air H2O content in the glaciated region around Muztagata.