Analysis of the origin of the distribution of CO in the subtropical southern Indian Ocean in 2007 (original) (raw)
Related papers
Journal of Geophysical Research, 2002
[1] Air from South Asia carries heavy loadings of organic and light-absorbing aerosol but low concentrations of ozone. We investigate ambient pollutant concentrations measured during the Indian Ocean Experiment (INDOEX), and we estimate emissions to determine the origin, magnitude, and impacts of air pollution from South Asia and to understand better the uncertainty in emission inventories. In India, the preponderance of motorcycles with small, two-stroke engines and the practice of adulterating gasoline with kerosene lead to high CO emission factors; for 1999, we estimate release of 15 Tg yr−1 from fossil fuel use and 40 Tg yr−1 from biomass burning. With the addition of isoprene oxidation, the total CO emissions were 67 Tg yr−1 from India and 87 Tg(CO) yr−1 from all of South Asia. These values indicate a somewhat larger contribution from fossil fuels but slightly lower overall emissions when compared to prior emission inventories. Two-stroke engines also exhibit high emission factors for volatile organic compounds (VOC) and particulate organic matter but produce only modest amounts of NOx. Near sources in India, VOC to NOx ratios appear too high for efficient O3 formation, although other factors probably contribute to observed low O3 mixing ratios. An inventory based on source characteristics and known emission factors for black carbon (BC) from South Asia yields 0.7 Tg yr−1 (upper limit of about 1.0 Tg yr−1) with biomass burning as the dominant source. We can test this inventory with measurements of ambient CO and BC—ship, island, and aircraft observations of air from South Asia all show a positive correlation between CO and BC (r2 = 0.71–0.81). Such strong correlations have also been observed over North America and Europe, but with a lower BC/CO slope. Ambient concentrations indicate high BC emission from South Asia: 2–3 Tg(BC) yr−1. This disagreement with emission inventories demonstrates the need for direct measurements from sources in India.
Seasonal variations of atmospheric CO 2 in the southern Indian Ocean
Tellus B, 1987
Atmospheric C0 1 recording at Amsterdam Island shows a 0. 7 ppm seasonal effect, non• attributable to local causes and significantly different from the results obtained in other southern hemisphere stations. An attempt is made at comparing this seasonal variation to C0 1 models.
Sea-air CO2 fluxes in the Indian Ocean between 1990 and 2009
2013
The Indian Ocean (44 • S-30 • N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO 2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea-air CO 2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO 2 uptake of −0.37 ± 0.06 PgC yr −1 is consistent with the −0.24 ± 0.12 PgC yr −1 calculated from observations. The fluxes from the southern Indian Ocean (18-44 • S; −0.43 ± 0.07 PgC yr −1 ) are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO 2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO 2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea-air CO 2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO 2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO 2 fluxes by atmospheric inversions was mainly caused by a lack of atmospheric data in the Indian Ocean. The OBGM models suggest a small strengthening of the sink over the period 1990-2009 of −0.01 PgC decade −1 . This is inconsistent with the observations in the southwestern Indian Ocean that shows the growth rate of oceanic pCO 2 was faster than the observed atmospheric CO 2 growth, a finding attributed to the trend of the Southern Annular Mode (SAM) during the 1990s.
2018
The forests of the Southwest Indian Ocean (SWIO) islands States are large carbon sinks. Rapid population growth in these islands is responsible for deforestation, which in turn is the main source of carbon dioxide (CO 2) emissions. This study is divided into two parts: The present study (Part 1) describes the seasonal vertical and surface spatial distribution of CO 2 over the SWIO islands and the temporal variation of surface CO 2 concentrations using data measured by the Tropospheric Emission Spectrometer (TES) on board the Aura Satellite. The CO 2 hotspots over these islands were identified and assessed to determine if they were associated with deforestation and forest degradation anthropogenic activities. Areas of minimum or low CO 2 atmospheric loading were also identified, and investigated to determine if they coincided with strong sink areas. Atmospheric CO 2 concentration was building-up from summer to spring. The spatial extent of CO 2 hotspots was found to increase from sum...
Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009
Biogeosciences, 2013
The Indian Ocean (44 • S-30 • N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO 2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea-air CO 2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO 2 uptake of −0.37 ± 0.06 PgC yr −1 is consistent with the −0.24 ± 0.12 PgC yr −1 calculated from observations. The fluxes from the southern Indian Ocean (18-44 • S; −0.43 ± 0.07 PgC yr −1 ) are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO 2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO 2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea-air CO 2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO 2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO 2 fluxes by atmospheric inversions was mainly caused by a lack of atmospheric data in the Indian Ocean. The OBGM models suggest a small strengthening of the sink over the period 1990-2009 of −0.01 PgC decade −1 . This is inconsistent with the observations in the southwestern Indian Ocean that shows the growth rate of oceanic pCO 2 was faster than the observed atmospheric CO 2 growth, a finding attributed to the trend of the Southern Annular Mode (SAM) during the 1990s.
First ground-based FTIR observations of the seasonal variation of carbon monoxide in the tropics
Geophysical Research Letters, 2008
We present the first ground-based solar absorption Fourier Transform Infrared (FTIR) spectrometric measurements in the inner tropics over several years. The FTIR observations agree well with satellite data from the MOPITT instrument. MATCH-MPIC model simulations reproduce the mean vertical structure of the FTIR observations. The model is generally not able to reproduce the extreme enhancements seen during the specific biomass burning events by both observation instruments. Nevertheless, the model indicates that beyond the background source of CO from methane oxidation, the main contributions to the CO mixing ratios are the episodic convective injection of NMHCs and CO from South American biomass burning into the upper troposphere, along with long range transport of African biomass burning CO, particularly during spring. In future studies with more extensive observed time series, observations such as these will be valuable for evaluating ongoing improvements in global chemistry transport models.
Journal of Geophysical Research, 2005
Carbon monoxide (CO) volume mixing ratio (VMR) profiles have been retrieved from ship-borne solar absorption spectra recorded in the Atlantic between 80°N and 70°S. CO profiles can be retrieved up to 30 km with a maximum altitude resolution of 4 km for a few layers. CO enhancements due to biomass burning have been detected. Recurring enhancements of CO were detected in the upper troposphere (10-15 km) in the equatorial regions and in the southern Atlantic (20°S-30°S). These enhancements could be traced back to African biomass burning sources as well as sources as far as South America. Similar results are observed in CO measurements from space by the Measurements of Pollution in the Troposphere (MOPITT) instrument. However, some enhancements in the upper troposphere especially above the source regions are difficult to distinguish from the MOPITT data. Results from the Model of Atmospheric Transport and Chemistry from the Max Planck Institute for Chemistry (MATCH-MPIC) show good agreement with the FTIR results. An analysis of the model data allows the quantification of the contributions of different sources such as biomass burning, fossil fuel combustion, and oxidation of methane (CH 4) and nonmethane hydrocarbons (NMHC).
Atmospheric Chemistry and Physics, 2012
Carbon monoxide (CO) and ozone (O 3) have been measured in the Western Pacific (43 • N to 35 • S) during a ship campaign with Research Vessel Sonne in fall 2009. Observations have been performed using ship-based solar absorption Fourier Transform infrared spectrometry, flask sampling, balloon sounding, and in-situ Fourier Transform infrared analysis. The obtained results are compared to the GEOS-Chem global 3-D chemistry transport model for atmospheric composition. In general, a very good agreement is found between the GEOS-Chem model and all instruments. The CO and O 3 distributions show a comparable variability suggesting an impact from the same source regions. Tagged-CO simulations implemented in the GEOS-Chem model allow to differentiate between different sources and source regions. The sources are verified with HYSPLIT backward trajectory calculations. In the Northern Hemisphere fossil fuel combustion in Asia is the dominant source. European and North American fossil fuel combustion also contribute to Northern Hemispheric CO pollution. In the Southern Hemisphere contributions from biomass burning and fossil fuel combustion are dominant; African biomass burning has a significant impact on Western Pacific CO pollution. Furthermore, in the tropical Western Pacific enhanced upper tropospheric CO within the tropical tropopause layer mainly originates from Indonesian fossil fuel combustion and can be transported into the stratosphere. The sources and source regions of the measured O 3 pollution are simulated with a tagged-O 3 simulation implemented in the GEOS-Chem model. Similar source regions compared to the tagged-CO simulations are identified by the model. In the Northern Hemisphere contributions from Asia, Europe, and North America are significant. In the Southern Hemisphere the impact of emissions from South America, SouthEast Africa, and Oceania is important.
Tellus B, 2005
A B S T R A C T CO 2 is one of the primary agents of global climate changes. The increase of atmospheric CO 2 concentration is essentially related to human-induced emissions and, particularly, to the burning of fossil fuel whose δ 13 C values are quite negative. Consequently, an increase of the CO 2 concentration in the atmosphere should be paralleled by a decrease of its δ 13 C. Continuous and/or spot measurements of CO 2 concentrations were repeatedly carried out during the last decade and in the same period of the year along hemispheric courses from Italy to Antarctica on a vessel of the Italian National Research Program in Antarctica. During these expeditions, discrete air samples were also collected in 4-l Pyrex flasks in order to carry out precise carbon isotope analyses on atmospheric CO 2 from different areas, including theoretically 'clean' open ocean areas, with the main purpose of comparing these open ocean results with the results obtained by the National Oceanic and Atmospheric Administration/World Meteorological Organization (NOAA/WMO) at land-based stations. According to the data obtained for these two variables, a relatively large atmospheric pollution is apparent in the Mediterranean area where the CO 2 concentration has reached the value of 384 ppmv while quite negative δ 13 C values have been measured only occasionally. In this area, southerly winds probably help to reduce the effect of atmospheric pollution even though, despite a large variability of CO 2 concentrations, these values are consistently higher than those measured in open ocean areas by a few ppmv to about 10 ppmv. A marked, though non-continuous, pollution is apparent in the area of the Bab-el-Mandeb strait where δ 13 C values considerably more negative than in the Central and Southern Red Sea were measured. The concentration of atmospheric CO 2 over the Central Indian Ocean increased from about 361 ppmv at the end of 1996 to about 373 ppmv at the end of 2003 (mean growth rate of about 1.7 ppmv yr −1 in excellent agreement with the NOAA/WMO data from land-based stations). Simultaneously, the mean δ 13 C value of atmospheric CO 2 over the Central Indian Ocean (Equator) decreased from −7.92‰ at the end of 1998 to −8.22‰ at the end of 2003; the mean decrease rate being of about −0.06‰ yr −1 . This rate as well as that calculated at 12 • S (−0.05‰ yr −1 ) are not far from the rates that may be calculated according to the data from the nearest NOAA sites (Crozet and Mahe islands); the rates calculated South of Australia and between Tasmania and N.Z. are almost identical to those calculated according to the data from Cape Grim NOAA site (Tasmania).
Atmospheric Chemistry and Physics, 2018
Atmospheric carbon monoxide (CO) and methane (CH 4) mole fractions are measured by ground-based in situ cavity ring-down spectroscopy (CRDS) analyzers and Fourier transform infrared (FTIR) spectrometers at two sites (St Denis and Maïdo) on Reunion Island (21 • S, 55 • E) in the Indian Ocean. Currently, the FTIR Bruker IFS 125HR at St Denis records the direct solar spectra in the near-infrared range, contributing to the Total Carbon Column Observing Network (TCCON). The FTIR Bruker IFS 125HR at Maïdo records the direct solar spectra in the mid-infrared (MIR) range, contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). In order to understand the atmospheric CO and CH 4 variability on Reunion Island, the time series and seasonal cycles of CO and CH 4 from in situ and FTIR (NDACC and TCCON) measurements are analyzed. Meanwhile, the difference between the in situ and FTIR measurements are discussed. The CO seasonal cycles observed from the in situ measurements at Maïdo and FTIR retrievals at both St Denis and Maïdo are in good agreement with a peak in September-November, primarily driven by the emissions from biomass burning in Africa and South America. The dry-air column averaged mole fraction of CO (X CO) derived from the FTIR MIR spectra (NDACC) is about 15.7 ppb larger than the CO mole fraction near the surface at Maïdo, because the air in the lower troposphere mainly comes from the Indian Ocean while the air in the middle and upper troposphere mainly comes from Africa and South America. The trend for CO on Reunion Island is unclear during the 2011-2017 period, and more data need to be collected to get a robust result. A very good agreement is observed in the tropospheric and stratospheric CH 4 seasonal cycles between FTIR (NDACC and TCCON) measurements, and in situ and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements, respectively. In the troposphere, the CH 4 mole fraction is high in August-September and low in December-January, which is due to the OH seasonal variation. In the stratosphere, the CH 4 mole fraction has its maximum in March-April and its minimum in August-October, which is dominated by vertical transport. In addition, the different CH 4 mole fractions between the in situ, NDACC and TCCON CH 4 measurements in the troposphere are discussed, and all measurements are in good agreement with the GEOS-Chem model simulation. The trend of X CH 4 is 7.6 ± 0.4 ppb yr −1 from the TCCON measurements over the 2011 to 2017 time period, which is consistent with the CH 4 Published by Copernicus Publications on behalf of the European Geosciences Union. 13882 M. Zhou et al.: Atmospheric CO and CH 4 measurements on Reunion Island trend of 7.4±0.5 ppb yr −1 from the in situ measurements for the same time period at St Denis. 2 Measurements on Reunion Island There are two sites on Reunion Island: St Denis (−20.9014 • N, 55.4848 • E; 85 m a.s.l. above sea level) which