scholarly journals Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 1: Carbon dioxide

2008 ◽  
Vol 8 (2) ◽  
pp. 5477-5536 ◽  
Author(s):  
O. Schneising ◽  
M. Buchwitz ◽  
J. P. Burrows ◽  
H. Bovensmann ◽  
M. Reuter ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Northern Hemisphere ◽  
Seasonal Cycle ◽  
Reference Data ◽  
Data Set ◽  
Annual Increase ◽  
Dry Air ◽  
Good Agreement

Abstract. Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases. SCIAMACHY on ENVISAT is the first satellite instrument whose measurements are sensitive to concentration changes of the two gases at all altitude levels down to the Earth's surface where the source/sink signals are largest. We have processed three years (2003–2005) of SCIAMACHY near-infrared nadir measurements to simultaneously retrieve vertical columns of CO2 (from the 1.58 μm absorption band), CH4 (1.66 μm) and oxygen (O2 A-band at 0.76 μm) using the scientific retrieval algorithm WFM-DOAS. We show that the latest version of WFM-DOAS, version 1.0, which is used for this study, has been significantly improved with respect to its accuracy compared to the previous versions while essentially maintaining its high processing speed (~1 minute per orbit, corresponding to ~6000 single measurements, and per gas on a standard PC). The greenhouse gas columns are converted to dry air column-averaged mole fractions, denoted XCO2 (in ppm) and XCH4 (in ppb), by dividing the greenhouse gas columns by simultaneously retrieved dry air columns. For XCO2 dry air columns are obtained from the retrieved O2 columns. For XCH4 dry air columns are obtained from the retrieved CO2 columns because of better cancellation of light path related errors compared to using O2 columns retrieved from the spectrally distant O2 A-band. Here we focus on a discussion of the XCO2 data set. The XCH4 data set is discussed in a separate paper (Part 2). In order to assess the quality of the retrieved XCO2 we present comparisons with Fourier Transform Spectroscopy (FTS) XCO2 measurements at two northern hemispheric mid-latitude ground stations. To assess the quality globally, we present detailed comparisons with global XCO2 fields obtained from NOAA's CO2 assimilation system CarbonTracker. For the Northern Hemisphere we find good agreement with the reference data for the CO2 seasonal cycle and the CO2 annual increase. For the Southern Hemisphere, where significantly less data are available for averaging compared to the Northern Hemisphere, the CO2 annual increase is also in good agreement with CarbonTracker but the amplitude and phase of the seasonal cycle show systematic differences up to a few ppm arising partially from the O2 normalization. The retrieved XCO2 regional pattern at monthly resolution over various regions show clear corrrelations with CarbonTracker but also significant differences. Typically the retrieved variability is about 4 ppm (1% of 380 ppm) higher but depending on time and location differences can reach or even exceed 8 ppm. Based on the error analysis and on the comparison with the reference data we conclude that the XCO2 data set can be characterized by a single measurement retrieval precision (random error) of 1–2%, a systematic low bias of about 1.5%, and by a relative accuracy of about 1–2% for monthly averages at a spatial resolution of about 7°×7°. When averaging the SCIAMACHY XCO2 over all three years we find reasonable correlation with EDGAR anthropogenic CO2 emissions for Germany, The Netherlands and Belgium indicating that regionally elevated CO2 arising from regional anthropogenic CO2 emissions can be detected from space.

scholarly journals Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 1: Carbon dioxide

2008 ◽  
Vol 8 (14) ◽  
pp. 3827-3853 ◽  
Author(s):  
O. Schneising ◽  
M. Buchwitz ◽  
J. P. Burrows ◽  
H. Bovensmann ◽  
M. Reuter ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gas ◽  
Northern Hemisphere ◽  
Seasonal Cycle ◽  
Reference Data ◽  
Data Set ◽  
Annual Increase ◽  
Dry Air ◽  
Concentration Changes ◽  
Good Agreement

Abstract. Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases. SCIAMACHY on ENVISAT is the first satellite instrument whose measurements are sensitive to concentration changes of the two gases at all altitude levels down to the Earth's surface where the source/sink signals are largest. We have processed three years (2003–2005) of SCIAMACHY near-infrared nadir measurements to simultaneously retrieve vertical columns of CO2 (from the 1.58 μm absorption band), CH4 (1.66 μm) and oxygen (O2 A-band at 0.76 μm) using the scientific retrieval algorithm WFM-DOAS. We show that the latest version of WFM-DOAS, version 1.0, which is used for this study, has been significantly improved with respect to its accuracy compared to the previous versions while essentially maintaining its high processing speed (~1 min per orbit, corresponding to ~6000 single measurements, and per gas on a standard PC). The greenhouse gas columns are converted to dry air column-averaged mole fractions, denoted XCO2 (in ppm) and XCH4 (in ppb), by dividing the greenhouse gas columns by simultaneously retrieved dry air columns. For XCO2 dry air columns are obtained from the retrieved O2 columns. For XCH4 dry air columns are obtained from the retrieved CO2 columns because of better cancellation of light path related errors compared to using O2 columns retrieved from the spectrally distant O2 A-band. Here we focus on a discussion of the XCO2 data set. The XCH4 data set is discussed in a separate paper (Part 2). In order to assess the quality of the retrieved XCO2 we present comparisons with Fourier Transform Spectroscopy (FTS) XCO2 measurements at two northern hemispheric mid-latitude ground stations. To assess the quality globally, we present detailed comparisons with global XCO2 fields obtained from NOAA's CO2 assimilation system CarbonTracker. For the Northern Hemisphere we find good agreement with the reference data for the CO2 seasonal cycle and the CO2 annual increase. For the Southern Hemisphere, where significantly less data are available for averaging compared to the Northern Hemisphere, the CO2 annual increase is also in good agreement with CarbonTracker but the amplitude and phase of the seasonal cycle show systematic differences (up to several ppm) arising partially from the O2 normalization most likely caused by unconsidered scattering effects due to subvisual cirrus clouds. The retrieved XCO2 regional pattern at monthly resolution over various regions show clear correlations with CarbonTracker but also significant differences. Typically the retrieved variability is about 4 ppm (1% of 380 ppm) higher but depending on time and location differences can reach or even exceed 8 ppm. Based on the error analysis and on the comparison with the reference data we conclude that the XCO2 data set can be characterized by a single measurement retrieval precision (random error) of 1–2%, a systematic low bias of about 1.5%, and by a relative accuracy of about 1–2% for monthly averages at a spatial resolution of about 7°×7°. When averaging the SCIAMACHY XCO2 over all three years we find elevated CO2 over the highly populated region of western central Germany and parts of the Netherlands ("Rhine-Main area") reasonably well correlated with EDGAR anthropogenic CO2 emissions. On average the regional enhancement is 2.7 ppm including an estimated contribution of 1–1.5 ppm due to aerosol related errors and sampling.

scholarly journals Update on GOSAT TANSO-FTS performance, operations, and data products after more than 6 years in space

2016 ◽  
Vol 9 (6) ◽  
pp. 2445-2461 ◽  
Author(s):  
Akihiko Kuze ◽  
Hiroshi Suto ◽  
Kei Shiomi ◽  
Shuji Kawakami ◽  
Makoto Tanaka ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Near Infrared ◽  
Satellite System ◽  
Fourier Transform Spectrometer ◽  
Infrared Sensor ◽  
Data Set ◽  
Dry Air ◽  
Retrieval Accuracy ◽  
Carbon Dioxide Co2

Abstract. A data set containing more than 6 years (February 2009 to present) of radiance spectra for carbon dioxide (CO2) and methane (CH4) observations has been acquired by the Greenhouse gases Observing SATellite (GOSAT, available at http://data.gosat.nies.go.jp/GosatUserInterfaceGateway/guig/GuigPage/open.do), nicknamed “Ibuki”, Thermal And Near infrared Sensor for carbon Observation Fourier Transform Spectrometer (TANSO-FTS). This paper provides updates on the performance of the satellite and TANSO-FTS sensor and describes important changes to the data product, which has recently been made available to users. With these changes the typical accuracy of retrieved column-averaged dry air mole fractions of CO2 and CH4 (XCO2 and XCH4, respectively) are 2 ppm or 0.5 % and 13 ppb or 0.7 %, respectively. Three major anomalies of the satellite system affecting TANSO-FTS are reported: a failure of one of the two solar paddles in May 2014, a switch to the secondary pointing system in January 2015, and most recently a cryocooler shutdown and restart in August 2015. The Level 1A (L1A) (raw interferogram) and the Level 1B (L1B) (radiance spectra) of version V201 described here have long-term uniform quality and provide consistent retrieval accuracy even after the satellite system anomalies. In addition, we discuss the unique observation abilities of GOSAT made possible by an agile pointing mechanism, which allows for optimization of global sampling patterns.

scholarly journals Sixty years of radiocarbon dioxide measurements at Wellington, New Zealand 1954–2014

2016 ◽  
Author(s):  
Jocelyn C. Turnbull ◽  
Sara E. Mikaloff Fletcher ◽  
India Ansell ◽  
Gordon Brailsford ◽  
Rowena Moss ◽  
...  
Keyword(s):  
New Zealand ◽  
Southern Ocean ◽  
Co2 Emissions ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Seasonal Cycle ◽  
Fossil Fuel ◽  
Anthropogenic Sources ◽  
Deep Waters ◽  
Cape Grim

Abstract. We present 60 years of Δ14CO2 measurements from Wellington, New Zealand (41° S, 175° E). The record has been extended and fully revised. New measurements have been used to evaluate the existing record and to replace original measurements where warranted. This is the earliest atmospheric Δ14CO2 record and records the rise of the 14C "bomb spike", the subsequent decline in Δ14CO2 as bomb 14C moved throughout the carbon cycle and increasing fossil fuel CO2 emissions further decreased atmospheric Δ14CO2. The initially large seasonal cycle in the 1960s reduces in amplitude and eventually reverses in phase, resulting in a small seasonal cycle of about 2 ‰ in the 2000s. The seasonal cycle at Wellington is dominated by the seasonality of cross-tropopause transport, and differs slightly from that at Cape Grim, Australia, which is influenced by anthropogenic sources in winter. Δ14CO2 at Cape Grim and Wellington show very similar trends, with significant differences only during periods of known measurement uncertainty. In contrast, Northern Hemisphere clean air sites show a higher and earlier bomb 14C peak, consistent with a 1.4-year interhemispheric exchange time. From the 1970s until the early 2000s, the Northern and Southern Hemisphere Δ14CO2 were quite similar, apparently due to the balance of 14C-free fossil fuel CO2 emissions in the north and 14C-depleted ocean upwelling in the south. The Southern Hemisphere sites show a consistent and marked elevation above the Northern Hemisphere sites since the early 2000s, which is most likely due to reduced upwelling of 14C-depleted and carbon-rich deep waters in the Southern Ocean. This developing Δ14CO2 interhemispheric gradient is consistent with recent studies that indicate a reinvigorated Southern Ocean carbon sink since the mid-2000s, and suggests that upwelling of deep waters plays an important role in this change.

scholarly journals A proposed fuel cell vehicle for reducing CO2 emissions and its contribution to reducing greenhouse gas emissions

2014 ◽  
Vol 3 (2) ◽  
pp. 252 ◽  
Author(s):  
Mohamed Mourad
Keyword(s):  
Carbon Dioxide ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Greenhouse Gas Emission ◽  
Fuel Cell Vehicle ◽  
Fuel Cell Vehicles ◽  
Gas Emissions

Because of their high efficiency and low emissions, fuel cell vehicles are undergoing extensive research and development. When considering the introduction of advanced vehicles, a complete evaluation must be performed to determine the potential impact of a technology on carbon dioxide (CO2) and greenhouse gases emissions. However, the reduction of CO2 emission from the vehicle became the most important objective for all researches institutes of vehicle technologies worldwide. There interest recently to find unconventional methods to reduce greenhouse gas emission from vehicle to keep the environment clean. This paper offers an overview and simulation study to fuel cell vehicles, with the aim of introducing their main advantages and evaluates their influence on emissions of carbon dioxide from fuel cell vehicle and compares advanced propulsion technologies on a well-to-wheel energy basis by using current technology for conventional and fuel cell. The results indicate that the use of fuel cells, and especially fuel cells that consume hydrogen, provide a good attempt for enhancing environment quality and reducing greenhouse gas (GHG) emissions. Moreover, the emission reduction percentage of fuel cell vehicle reaches to 64% comparing to the conventional vehicle. Keywords: Fuel Cell Electric Vehicle, Performance, Simulation, Driving Cycle, CO2 Emissions, Greenhouse Gas Emissions, Fuel Consumption.

scholarly journals Net Carbon Dioxide Emission from An Eroding Atlantic Blanket Bog

2021 ◽  
Author(s):  
Rebekka Artz ◽  
Mhairi Coyle ◽  
Gillian Donaldson-Selby ◽  
Ross Morrison
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Global Climate ◽  
Carbon Dioxide Emission ◽  
Gas Emissions ◽  
Special Cases ◽  
Blanket Bog ◽  
Projected Changes

Abstract The net impact of greenhouse gas emissions from degraded peatland environments on national Inventories and subsequent mitigation of such emissions has only been seriously considered within the last decade. Data on greenhouse gas emissions from special cases of peatland degradation, such as eroding peatlands, are particularly scarce. Here, we report the first eddy covariance-based monitoring of carbon dioxide (CO2) emissions from an eroding Atlantic blanket bog. The CO2 budget across the period July 2018 to November 2019 was 147 (+/- 9) g C m-2. For an annual budget that contained proportionally more of the extreme 2018 drought and heat wave, cumulative CO2 emissions were nearly double (191 g C m-2) of that of an annual period without drought (106 g C m-2), suggesting that direct CO2 emissions from eroded peatlands are at risk of increasing with projected changes in temperatures and precipitation due to global climate change. The results of this study are consistent with chamber-based and modelling studies that suggest degraded blanket bogs to be a net source of CO2 to the atmosphere, and provide baseline data against which to assess future peatland restoration efforts in this region.

Evaluating the Carbon Embedded in the US Public Water Supply

2011 ◽  
Author(s):  
Kelly M. Twomey ◽  
Michael E. Webber
Keyword(s):  
United States ◽  
Carbon Dioxide ◽  
Water Supply ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Fossil Fuel ◽  
Fuel Combustion ◽  
Public Water Supply ◽  
Fossil Fuel Combustion ◽  
The Us

The United States uses approximately 5% of its primary energy and 6% of its electricity to pump, convey, treat, distribute, heat, and recondition water in the US public water supply. Allocating this energy towards water has contributed to a national public water distribution system that is considered among the best in the world, providing its users with a clean and reliable water supply. This water supply, treated to stringent water standards defined by the Environmental Protection Agency’s Safe Drinking Water Act, has been critical to the health and livelihood of United States’ citizens. However, this energy-expenditure comes at an environmental cost, since the majority of water-related energy is derived from burning fossil fuels. Fossil-fuel combustion emits carbon-dioxide, a greenhouse gas that has become of concern in recent years because of its connection to anthropogenic climate change. The amount of carbon-dioxide that is emitted from fossil-fuel combustion is principally a function of the quantity and type of fuel that is burned for energy. This first-order analysis quantifying national water-related carbon dioxide emissions is the second in a series of several analyses by the authors, quantifying the energy and greenhouse emissions embedded in the US public water supply. Results indicate that water withdrawal, conveyance, treatment, distribution, end-use preparation, and wastewater treatment produces approximately 301 million metric tonnes of CO2 emissions annually. This quantity is 5.1% of total US CO2 emissions in 2009, which is approximately equal to emissions from the gasoline consumed by one-quarter of the US passenger fleet in the same year. Considering that the emissions associated with water for industrial, municipal and self-supplied sectors (such as agriculture) were not included in this analysis, the actual quantity of carbon emissions released as a result of water-related activities is likely to be higher. Consequently, identifying efficiency measures and conservation schemes to reduce the amount of water-related energy consumed in the US might be significant in achieving future greenhouse gas emission reduction goals.

Seasonal and diurnal methane and carbon dioxide emissions from the littoral area of the Miyun Reservoir in Beijing, China

2018 ◽  
Vol 69 (5) ◽  
pp. 751 ◽  
Author(s):  
Gang Li ◽  
Hongli Li ◽  
Meng Yang ◽  
Ting Lei ◽  
Mingxiang Zhang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Carbon Dioxide Emissions ◽  
Co2 Flux ◽  
Closed Chamber ◽  
Gas Emissions ◽  
Littoral Zones ◽  
Littoral Area

Reservoirs have been regarded as hot spots for greenhouse gas emissions since the 1990s. However, there is scant research about littoral zones of reservoirs. In the present study, static closed chamber and gas chromatograph techniques were used to measure methane (CH4) and carbon dioxide (CO2) flux in the littoral area of a temperate reservoir from 2009 to 2010. The littoral area comprises three zones, namely supralittoral, eulittoral and infralittoral. The patterns of CH4 and CO2 emissions from these three littoral zones were significantly different during the sampling periods, with the eulittoral zone having the highest CH4 flux and the supralittoral zone having the highest CO2 flux. Temperature and biomass correlated with CH4 and CO2 emissions. Measurement of CO2 emissions after removing vegetation varied in each zone and according to time of sampling. A large littoral area of the reservoir sampled herein will be submerged and converted to a pelagic area with deep standing water after the South to North Water Transfer Project is completed, in 2050. The results of the present study suggest further research and monitoring are needed, and should focus on likely effects of extreme climate events and the effects of human-mediated factors on greenhouse gas emissions.

Influence of photoperiod on carbon dioxide and methane emissions from two pilot-scale stabilization ponds

2012 ◽  
Vol 66 (9) ◽  
pp. 1930-1940 ◽  
Author(s):  
Juan P. Silva ◽  
José L. Ruiz ◽  
Miguel R. Peña ◽  
Henk Lubberding ◽  
Huub Gijzen
Keyword(s):  
Carbon Dioxide ◽  
Chemical Oxygen Demand ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Ghg Emissions ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
The Other ◽  
Solar Light ◽  
Static Chamber

Greenhouse gas (GHG) emissions (CO2, CH4) from pilot-scale algal and duckweed-based ponds (ABP and DBP) were measured using the static chamber methodology. Daylight and nocturnal variations of GHG and wastewater characteristics (e.g. chemical oxygen demand (COD), pH) were determined via sampling campaigns during midday (12:30–15:30) and midnight (00:30–03:30) periods. The results showed that under daylight conditions in ABP median emissions were −232 mg CO2 m−2 d−1 and 9.9 mg CH4 m−2 d−1, and in DBP median emissions were −1,654.5 mg CO2 m−2 d−1 and 71.4 mg CH4 m−2 d−1, respectively. During nocturnal conditions ABP median emissions were 3,949.9 mg CO2 m−2 d−1, 12.7 mg CH4 m−2 d−1, and DBP median emissions were 5,116 mg CO2 m−2 d−1, 195.2 mg CH4 m−2 d−1, respectively. Once data measured during daylight were averaged together with nocturnal data the median emissions for ABP were 1,566.8 mg CO2 m−2 d−1 and 72.1 mg CH4 m−2 d−1, whilst for DBP they were 3,016.9 mg CO2 m−2 d− and 178.9 mg CH4 m−2 d−1, respectively. These figures suggest that there were significant differences between CO2 emissions measured during daylight and nocturnal periods (p < 0.05). This shows a sink-like behaviour for both ABP and DBP in the presence of solar light, which indicates the influence of photosynthesis in CO2 emissions. On the other hand, the fluxes of CH4 indicated that DBP and ABP behave as net sources of CH4 during day and night, although higher emissions were observed from DBP. Overall, according to the compound average (daylight and nocturnal emissions) both ABP and DBP systems might be considered as net sources of GHG.

Influence of Static Atomic Displacements on Composition Quantification of AlGaN/GaN Heterostructures from HAADF-STEM Images

2014 ◽  
Vol 20 (5) ◽  
pp. 1463-1470 ◽  
Author(s):  
Marco Schowalter ◽  
Ingo Stoffers ◽  
Florian F. Krause ◽  
Thorsten Mehrtens ◽  
Knut Müller ◽  
...  
Keyword(s):  
Reference Data ◽  
Dark Field ◽  
Data Set ◽  
Atomic Displacements ◽  
Annular Dark Field ◽  
Alternative Techniques ◽  
Reference Samples ◽  
Slight Discrepancy ◽  
Good Agreement

AbstractIn an earlier publication Rosenauer et al. introduced a method for determination of composition in AlGaN/GaN heterostructures from high-angle annular dark field (HAADF) images. Static atomic displacements (SADs) were neglected during simulation of reference data because of the similar covalent radii of Al and Ga. However, SADs have been shown (Grillo et al.) to influence the intensity in HAADF images and therefore could be the reason for an observed slight discrepancy between measured and nominal concentrations. In the present study parameters of the Stillinger–Weber potential were varied in order to fit computed elastic constants, lattice parameters and bonding energies to experimental ones. A reference data set of HAADF images was simulated, in which the new parameterization was used to account for SADs. Two reference samples containing AlGaN layers with different Al concentrations were investigated and Al concentrations in the layers determined based on the new data set. We found that these concentrations were in good agreement with nominal concentrations as well as concentrations determined using alternative techniques such as strain state analysis and energy dispersive X-ray spectroscopy.

scholarly journals Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 2: Methane

2009 ◽  
Vol 9 (2) ◽  
pp. 443-465 ◽  
Author(s):  
O. Schneising ◽  
M. Buchwitz ◽  
J. P. Burrows ◽  
H. Bovensmann ◽  
P. Bergamaschi ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Temporal Pattern ◽  
Near Infrared ◽  
Co2 Assimilation ◽  
Retrieval Algorithm ◽  
Data Set ◽  
Dry Air ◽  
Concentration Changes ◽  
Spatio Temporal ◽  
Carbon Dioxide Co2

Abstract. Carbon dioxide (CO2) and methane (CH4) are the two most important anthropogenic greenhouse gases. SCIAMACHY on ENVISAT is the first satellite instrument whose measurements are sensitive to concentration changes of the two gases at all altitude levels down to the Earth's surface where the source/sink signals are largest. We have processed three years (2003–2005) of SCIAMACHY near-infrared nadir measurements to simultaneously retrieve vertical columns of CO2 (from the 1.58 μm absorption band), CH4 (1.66 μm) and oxygen (O2 A-band at 0.76 μm) using the scientific retrieval algorithm WFM-DOAS. We show that the latest version of WFM-DOAS, version 1.0, which is used for this study, has been significantly improved with respect to its accuracy compared to the previous versions while essentially maintaining its high processing speed (~1 min per orbit, corresponding to ~6000 single measurements, and per gas on a standard PC). The greenhouse gas columns are converted to dry air column-averaged mole fractions, denoted XCO2 (in ppm) and XCH4 (in ppb), by dividing the greenhouse gas columns by simultaneously retrieved dry air columns. For XCO2 dry air columns are obtained from the retrieved O2 columns. For XCH4 dry air columns are obtained from the retrieved CO2 columns because of better cancellation of light path related errors compared to using O2 columns retrieved from the spectrally distant O2 A-band. Here we focus on a discussion of the XCH4 data set. The XCO2 data set is discussed in a separate paper (Part 1). For 2003 we present detailed comparisons with the TM5 model which has been optimally matched to highly accurate but sparse methane surface observations. After accounting for a systematic low bias of ~2% agreement with TM5 is typically within 1–2%. We investigated to what extent the SCIAMACHY XCH4 is influenced by the variability of atmospheric CO2 using global CO2 fields from NOAA's CO2 assimilation system CarbonTracker. We show that the CO2 corrected and uncorrected XCH4 spatio-temporal pattern are very similar but that agreement with TM5 is better for the CarbonTracker CO2 corrected XCH4. In line with previous studies (e.g., Frankenberg et al., 2005b) we find higher methane over the tropics compared to the model. We show that tropical methane is also higher when normalizing the CH4 columns with retrieved O2 columns instead of CO2. In consistency with recent results of Frankenberg et al. (2008b) it is shown that the magnitude of the retrieved tropical methane is sensitive to the choice of the spectroscopic line parameters of water vapour. Concerning inter-annual variability we find similar methane spatio-temporal pattern for 2003 and 2004. For 2005 the retrieved methane shows significantly higher variability compared to the two previous years, most likely due to somewhat larger noise of the spectral measurements.

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