Temporal and Spatial Distribution Characteristics of Carbon Monoxide Column Amount over China Based on Satellite Data

Carbon monoxide is an important tropospheric species inasmuch as it influences the atmospheric chemistry through its reaction with the OH radical. It's also one of the main pollutants produced by incomplete combustion processes. Coupled with few weeks lifetime, it can be used as a tracer of atmospheric transport. Surface CO measurements which have generally been limited to boundary layer measurements often affected by local pollution cannot provide a global view of CO temporal and spatial distribution. Better understand these characteristics relies on a combination of ground based, aircraft, and space based measurements. CO long term changes and trends over a large area can only be obtained through space based remote sensing observations. Such measurements have been carried out by the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument on ENVISAT satellite and the Measurement of Pollution in the Troposphere instrument on TERRA (MOPITT). These measurements have been used effectively on monitoring CO plumes from forest fires, intercontinental transport of pollutions, frontal lifting and convective transport of pollution to the upper troposphere, and for inverse modeling to quantify surface source of CO. MOPITT measurements are useful in providing a global picture of the distribution of CO, but studies on their near surface application is limited. Since the sensors of CO on MOPITT are near the 4.7 μm absorption spectra, they are sensitive to CO mostly in the middle and upper troposphere but generally less sensitive in the lower troposphere comparing with the CO measurements in the solar channel at 2.3 μm by SCIMACHY. An introduction is given on CO remote sensing retrieval methods used by SCIAMACHY/ENVISAT and MOPITT/TERRA. Distribution properties and trend of CO from MOPITT of 2003 to 2005 are compared to SCIMACHY retrieval results. The two products show good agreement on the land; also they give roughly the same spatial and temporal distribution characteristics of CO. Comparisons between MOPITT product and ground measurement data of CO over Longfengshan, Lin'an and Waliguan during 2007—2008 show roughly the same temporal change in posture. Distribution characteristics and trend of CO from March 2000 to February 2004 over China is analyzed using MOPITT retrieval CO column amount product. On the average, CO in the east of China is higher than west. There is significant seasonal variation for CO with a peak in spring time. CO concentration in summer time is lowest in the east, but it reaches the minimum in autumn in the west of China. Trends analysis suggests that CO average column amount have increased during these nine years. The increasing trend for CO in the west region of China is at magnitude of a few thousandths, but in the east the increasing trend is about 1%.