Global Distributions of Carbon Monoxide Total Column: A Statistical Analysis from MOPITT Data
Abstract
Measurements Of Pollution In The Troposphere (MOPITT) on board NASA Terra satellite is a sensor developed for measuring carbon monoxide (CO) from space. The CO measurements made by MOPITT have greatly enhanced our understanding of temporal and spatial distributions of CO in the atmosphere and the mechanisms governing the distributions. In this study, the global CO data are statistically analyzed in terms of CO total column variations with time, latitude, longitude, and altitude. This statistics provides a new and comprehensive overview of global CO distributions in a quantitative way. The information is useful not only to atmospheric science community but also to other disciplines and public, owing to the importance of CO as a major pollutant, a precursor of ozone, and its effects on many atmospheric chemical processes. The CO data have illustrated the combined effects of natural and anthropogenic factors on the CO distributions in the atmosphere. The preliminary results from the analysis are highlighted as follows: (1) The mean CO of the northern hemisphere usually reaches its maximum in April-May, mainly because of low atmospheric oxidation capacity at the time. The maximum CO of the southern hemisphere often appears in October-November due to large fire events. As a result, seasonal variation of global mean CO generally shows two peaks at a level up to 2.0 ' 1018 molecules/cm2, in April-May and October-November. (2) As land is a source of CO and the fraction of land increases with latitude, global annual mean CO total column increase with latitude from ~1.0 ' 1018 molecules/cm2 in the south pole to 2.1 ' 1018 molecules/cm2 at 0o, then staying around that level up to the north pole. When looking at CO over land only, a peak of 2.3 ' 1018 between -10oS and 10oN and a trough at 34oN can be found. The former results from vegetation fires in the tropics and the latter is due to the Plateau of Tibet. The CO averaged over oceans increases from the south pole to 50oN and then decreases slightly along latitude. The trend of CO with latitude is similar to that for CO2. (3) Along longitude circles, global annual mean CO fluctuates from 1.6 to 1.9 ' 1018 molecules/cm2, a variation smaller than that across latitudes. The fluctuation is larger over land than that over oceans. (4) Considering both latitude and time, the rate of CO increase with latitude is the smallest in June/July (~ 0.006 ' 1018 molecules/cm2 per degree between ±60o) and the largest in April/May (one time bigger than that for June/July). The amplitude of seasonal variation of CO is low in the southern hemisphere at 45oS and 5oS (0.4 ' 1018 molecules/cm2 per year). In the northern hemisphere, the amplitude is ~0.6 ' 1018 molecules/cm2 per year with a small change with latitude. (5) CO total column generally decreases with altitude because of the reduction of air mass. In terms of the global annual mean, CO total column declines at a lapse rate of 0.3 ' 1018 molecules/cm2 per kilometer. (6) With a series of daily global mean CO from 2000 to 2004, a short-time trend of 0.025 ' 1018 molecules/cm2 per year is found. A long-term trend can be established if MOPITT continues on orbit for a longer period and other space-borne instrument shall be available to replace MOPITT when it is not operating.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.A43B..01D
- Keywords:
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- 0322 Constituent sources and sinks;
- 0365 Troposphere: composition and chemistry;
- 3322 Land/atmosphere interactions;
- 3360 Remote sensing