Measurements Of Atmospheric Carbon Dioxide Research Articles

NASA Orbiting Carbon Observatory: measuring the column averaged carbon dioxide mole fraction from space

The NASA Orbiting Carbon Observatory (OCO) will make space-based measurements of atmospheric carbon dioxide (CO2) with the precision, resolution, and coverage needed to characterize regional scale CO2 sources and sinks and quantify their vari¬ability over the seasonal cycle. This mission will be launched in December 2008 and will fly in a 705 km altitude, 1:26 PM sun-synchronous orbit that provides complete coverage of the sunlit hemisphere with a 16-day ground track repeat cycle. OCO carries a single instrument designed to make co-boresighted spectroscopic measurements of reflected sunlight in near-infrared CO2 and molecular oxygen (O2) bands. These CO2 and O2 measurements will be combined to provide spatially resolved estimates of the column averaged CO2 dry air mole fraction, XCO2. The instrument collects 12 to 24 XCO2 soundings/second over the sunlit portion of the orbit, yielding 200 to 400 soundings per degree of latitude, or 7 to 14 million soundings every 16 days. Existing studies indicate that at least 10% of these soundings will be sufficiently cloud free to yield XCO2 estimates with accuracies of ~0.3 to 0.5% (1 to 2 ppm) on regional scales every month.

New method for isotopic ratio measurements of atmospheric carbon dioxide using a 4.3 μm pulsed quantum cascade laser

We present a new approach to the measurement of stable isotopic ratios of carbon dioxide using a near-room-temperature pulsed quantum cascade laser and a spectral ratio method based upon dual multiple pass absorption cells. The spectral ratio method improves precision and accuracy by reducing sensitivity to variations in the laser tuning rate, power and line width. The laser is scanned across three spectral lines (near 2310 cm-1) quantifying three CO2 isotopologues: 12C16O2, 13C16O2 and 12C16O18O. Isotopic ratios are determined simultaneously with a precision of 0.2δ for each ratio with a one-second measurement. Signal averaging for 400 s improves the precision to better than 0.03δ for both isotopic ratios (13 R and 18 R). Long-term accuracy of 0.2 to 0.3δ is demonstrated with replicate measurements of the same sample over a one-month period. The fast time response of this instrument is suitable for eddy flux measurements.

Demonstration Measurements of Water Vapor, Cirrus Clouds, and Carbon Dioxide Using a High-Performance Raman Lidar

Abstract Profile measurements of atmospheric water vapor, cirrus clouds, and carbon dioxide using the Raman Airborne Spectroscopic lidar (RASL) during ground-based, upward-looking tests are presented here. These measurements improve upon any previously demonstrated using Raman lidar. Daytime boundary layer profiling of water vapor mixing ratio up to an altitude of approximately 4 km under moist, midsummer conditions is performed with less than 5% random error using temporal and spatial resolution of 2 min and 60–210 m, respectively. Daytime cirrus cloud optical depth and extinction-to-backscatter ratio measurements are made using a 1-min average. The potential to simultaneously profile carbon dioxide and water vapor mixing ratio through the boundary layer and extending into the free troposphere during the nighttime is also demonstrated.

A complete study of CO 2 line parameters around 4845 cm −1 for Lidar applications

A diode laser spectrometer was used in the Groupe de Spectrométrie Moléculaire et Atmosphérique of Reims (France) to study CO 2 line intensities, self-broadening coefficients and air-pressure-broadening coefficients near 2.063 μm. The spectral region ranging from 4843 to 4848 cm −1, which is suitable for the measurement of atmospheric carbon dioxide (CO 2) mixing ratios was studied using a new generation-commercial diode laser from Nanoplus. Three lines of the (20°1) III←(0 0 0) band of CO 2 have been studied. The results of intensity measurements and self-broadening coefficients are compared with previous determinations and available databases. Furthermore, the air-broadening coefficients for these transitions are also reported and analyzed. Finally, these new parameters are used for the measurement of atmospheric CO 2 mixing ratio with the 2 μm heterodyne differential absorption Lidar from the Laboratoire de Météorologie Dynamique at Palaiseau (France). These new parameters demonstrate a dramatic improvement of the retrieved atmospheric CO 2 concentrations.

Metrological traceability: I make it 42; you make it 42; but is it the same 42?

The paper reproduces a talk given at a 2-day symposium on quality assurance in chemistry held in Brisbane, Australia in 2005. Intended for an audience of analysts in the field, the theme of the symposium drew inspiration from the series of books by Douglas Adams “The Hitchhiker's Guide to the Galaxy”. An introduction to basic concepts of metrological traceability is followed by a discussion of practical steps to ensure metrological traceability of field measurement results. The relationship between metrological traceability and comparability of measurement results is discussed. To achieve metrological traceability in the field, the use of appropriate certified reference materials for calibration is recommended. Examples of atmospheric carbon dioxide and roadside breathalyzer measurements are given.

Mauna Loa volcano is not a methane source: Implications for Mars

Thirteen years of continuous atmospheric carbon dioxide and methane measurements at the Mauna Loa Observatory in Hawaii are used to determine the methane emission rate from the summit of Mauna Loa volcano. We find no measurable methane emissions coming from the summit area, with a 95% confidence upper limit of 9 t CH4 yr−1. Recent studies have detected 10 ppb CH4 in the Martian atmosphere, requiring emissions of about 300 t CH4 yr−1. Volcanic activity has been suggested as a source of abiogenic CH4 on Mars, either by magmatic degassing or reactions in hydrothermal fluids heated by a magma intrusion. The most recent lava flows on Mars (2 My ago) are on the Tharsis shield volcanoes, which may still be active. If Mauna Loa is a valid terrestrial analog, our findings suggest that volcanic activity is not a significant source of methane to the Martian atmosphere.

Designated “no smoking” areas provide from partial to no protection from environmental tobacco smoke

Objective: To determine the efficacy of designated “no smoking” areas in the hospitality industry as a means of providing protection from environmental tobacco smoke (ETS), and whether certain design features...

Sensitivity studies for space-based measurement of atmospheric total column carbon dioxide by reflected sunlight.

The feasibility of making space-based carbon dioxide (CO2) measurements for global and regional carbon-cycle studies is explored. With the proposed detection method, we use absorption of reflected sunlight near 1.58 microm. The results indicate that the small (degrees 1%) changes in CO2 near the Earth's surface are detectable provided that an adequate sensor signal-to-noise ratio and spectral resolution are achievable. Modification of the sunlight path by scattering of aerosols and cirrus clouds could, however, lead to systematic errors in the CO2 column retrieval; therefore ancillary aerosol and cloud data are important to reduce errors. Precise measurement of surface pressure and good knowledge of the atmospheric temperature profile are also required.

The Orbiting Carbon Observatory (OCO) mission

The Orbiting Carbon Observatory (OCO) mission will make the first global, space-based measurements of atmospheric carbon dioxide (CO 2) with the precision, resolution, and coverage needed to characterize CO 2 sources and sinks on regional scales. The measurement approach and instrument specifications were determined through an analysis of existing carbon cycle data and a series of observing system simulation experiments. During its 2-year mission, OCO will fly in a 1:15 PM sun-synchronous orbit with a 16-day ground-track repeat time, just ahead of the EOS Aqua platform. It will carry a single instrument that incorporates three bore-sighted high-resolution spectrometers designed to measure reflected sunlight in the 0.76-μm O 2 A-band and in the CO 2 bands at 1.61 and 2.06 μm. Soundings recorded in these three bands will be used to retrieve the column-averaged CO 2 dry air mole fraction ( X CO 2 ). A comprehensive validation program was included in the mission to ensure that the space-based X CO 2 measurements have precisions of ∼0.3% (1 ppm) on regional scales. OCO measurements will be used in global synthesis inversion and data assimilation models to quantify CO 2 sources and sinks. While OCO will have a nominal lifetime of only 2 years, it will serve as a pathfinder for future long-term CO 2 monitoring missions.

Tropical rain forest tree growth and atmospheric carbon dynamics linked to interannual temperature variation during 1984-2000.

During 1984-2000, canopy tree growth in old-growth tropical rain forest at La Selva, Costa Rica, varied >2-fold among years. The trees' annual diameter increments in this 16-yr period were negatively correlated with annual means of daily minimum temperatures. The tree growth variations also negatively covaried with the net carbon exchange of the terrestrial tropics as a whole, as inferred from nearly pole-to-pole measurements of atmospheric carbon dioxide (CO(2)) interpreted by an inverse tracer-transport model. Strong reductions in tree growth and large inferred tropical releases of CO(2) to the atmosphere occurred during the record-hot 1997-1998 El Niño. These and other recent findings are consistent with decreased net primary production in tropical forests in the warmer years of the last two decades. As has been projected by recent process model studies, such a sensitivity of tropical forest productivity to on-going climate change would accelerate the rate of atmospheric CO(2) accumulation.

The impact of local winds and long-range transport on the continuous carbon dioxide record at Mount Waliguan, China

This paper describes the continuous measurements of atmospheric carbon dioxide at Mt. Waliguan (36°17ʹN, 100°54ʹE, 3816 m asl) in western China over the period 1994–2000. The CO2 hourly mixing ratios were segregated by horizontal wind direction/speed and vertical winds, respectively, merged by season over the entire measurement period. The short-term variability in CO2 was examined mainly from the point of view of local winds observed at this station and isobaric back trajectory cluster-concentration analysis as for local and long-range transport influence, to permit the selection of hourly average data that is representative of background conditions. From the selected hourly data, daily, monthly and annual averages that are not influenced by local CO2 sources and sinks be computed by discriminating the local and regional impact on the Waliguan CO2 records. On the basis of these results, background CO2 data were then analyzed to evaluate the averaged diurnal variation, monthly mean time series, CO2 mixing ratio distribution in different seasons as well as averaged seasonal cycle. Annual mean and growth rate of CO2 at Waliguan during the period of 1991 to 2000 were further discussed by supplement with NOAA/CMDL flask air sampling records at this station and other monitoring stations located at similar latitudinal band in the Northern Hemisphere. The results from this study can provide atmospheric CO2 characteristics in Asian inland regions, and be used in other studies to improve the understanding of carbon source and sink distributions.

The impact of local winds and long-range transport on the continuous carbon dioxide record at Mount Waliguan, China

This paper describes the continuous measurements of atmospheric carbon dioxide at Mt. Waliguan (36°17ʹN, 100°54ʹE, 3816 m asl) in western China over the period 1994–2000. The CO2 hourly mixing ratios were segregated by horizontal wind direction/speed and vertical winds, respectively, merged by season over the entire measurement period. The short-term variability in CO2 was examined mainly from the point of view of local winds observed at this station and isobaric back trajectory cluster-concentration analysis as for local and long-range transport influence, to permit the selection of hourly average data that is representative of background conditions. From the selected hourly data, daily, monthly and annual averages that are not influenced by local CO2 sources and sinks be computed by discriminating the local and regional impact on the Waliguan CO2 records. On the basis of these results, background CO2 data were then analyzed to evaluate the averaged diurnal variation, monthly mean time series, CO2 mixing ratio distribution in different seasons as well as averaged seasonal cycle. Annual mean and growth rate of CO2 at Waliguan during the period of 1991 to 2000 were further discussed by supplement with NOAA/CMDL flask air sampling records at this station and other monitoring stations located at similar latitudinal band in the Northern Hemisphere. The results from this study can provide atmospheric CO2 characteristics in Asian inland regions, and be used in other studies to improve the understanding of carbon source and sink distributions.

Spectroscopic gas analyzers based on indium-phosphide, antimonide and lead-salt diode-lasers

Currently available semiconductor lasers for spectroscopy in the near- and mid-infrared region based on direct band-to-band transitions as gallium-arsenide, indium-phosphide, antimonides and lead-salt containing compounds will be discussed together with the main features of different tunable diode-laser absorption spectrometers for trace gas analysis. Measurements of atmospheric carbon dioxide with a room-temperature 2 μm indium-phosphide laser, applications of antimonide lasers for methane and formaldehyde sensing in the 3–4 μm range and a fast chemical sensor for methane flux measurements based on lead-salt diode-lasers operating near 7.8 μm will be presented.

Near- and mid-infrared laser-optical sensors for gas analysis

Semiconductor diode lasers were first developed in the mid-1960s and found immediate application as much needed tunable sources for high-resolution laser spectroscopy commonly referred to as tunable diode laser absorption spectroscopy (TDLAS). In this paper, currently available semiconductor lasers for spectroscopy in the near- and mid-infrared spectral region based upon gallium arsenide, indium phosphite, antimonides and lead-salt containing compounds will be reviewed together with the main features of TDLAS. Room-temperature measurements of atmospheric carbon dioxide near 2 μm will be discussed and recent results obtained with a fast chemical sensor for methane flux measurements based on lead-salt diode lasers operating near 7.8 μm will be presented.

Regional changes in carbon dioxide fluxes of land and oceans since 1980.

We have applied an inverse model to 20 years of atmospheric carbon dioxide measurements to infer yearly changes in the regional carbon balance of oceans and continents. The model indicates that global terrestrial carbon fluxes were approximately twice as variable as ocean fluxes between 1980 and 1998. Tropical land ecosystems contributed most of the interannual changes in Earth's carbon balance over the 1980s, whereas northern mid- and high-latitude land ecosystems dominated from 1990 to 1995. Strongly enhanced uptake of carbon was found over North America during the 1992-1993 period compared to 1989-1990.

Modeling the effects of snowpack on heterotrophic respiration across northern temperate and high latitude regions: Comparison with measurements of atmospheric carbon dioxide in high latitudes

Simulations by global terrestrial biogeochemical models (TBMs) consistently underestimate the concentration of atmospheric carbon dioxide (CO2 at high latitude monitoring stations during the non-growing season. We hypothesized that heterotrophic respiration is underestimated during the nongrowing season primarily because TBMs do not generally consider the insulative effects of snowpack on soil temperature. To evaluate this hypothesis, we compared the performance of baseline and modified versions of three TBMs in simulating the seasonal cycle of atmospheric CO2 at high latitude CO2 monitoring stations; the modified version maintained soil temperature at 0 °C when modeled snowpack was present. The three TBMs include the Carnegie-Ames-Stanford Approach (CASA), Century, and the Terrestrial Ecosystem Model (TEM). In comparison with the baseline simulation of each model, the snowpack simulations caused higher releases of CO2 between November and March and greater uptake of CO2 between June and August for latitudes north of 30° N. We coupled the monthly estimates of CO2 exchange, the seasonal carbon dioxide flux fields generated by the HAMOCC3 seasonal ocean carbon cycle model, and fossil fuel source fields derived from standard sources to the three-dimensional atmospheric transport model TM2 forced by observed winds to simulate the seasonal cycle of atmospheric CO2 at each of seven high latitude monitoring stations. In comparison to the CO2 concentrations simulated with the baseline fluxes of each TBM, concentrations simulated using the snowpack fluxes are generally in better agreement with observed concentrations between August and March at each of the monitoring stations. Thus, representation of the insulative effects of snowpack in TBMs generally improves simulation of atmospheric CO2 concentrations in high latitudes during both the late growing season and nongrowing season. These simulations highlight the global importance of biogeochemical processes during the nongrowing season in estimating carbon balance of ecosystems in northern high and temperate latitudes.

The Response of Global Terrestrial Ecosystems to Interannual Temperature Variability

Measurements of atmospheric carbon dioxide and satellite-derived measurements of temperature and the vegetation index were used to investigate relationships among climate, carbon dioxide, and ecosystems. At the global scale, lagged correlations between temperature and carbon dioxide growth rate were found, indicating modulation by biogeochemical feedbacks. Spatial analysis of the temperature and vegetation index data suggests that the global correlations are a composite of individualistic responses of different ecosystems. The existence of biome-specific time scales of response implies that changes in global ecosystem distributions could indirectly alter the relationships between climate and carbon storage.

Short-term variations in atmospheric CO<sub>2</sub> at Ny-Ålesund, Spitsbergen, during spring and summer

Results from the continuous measurements of atmospheric carbon dioxide performed at Ny-Alesund, Spitsbergen are presented. The results are discussed with an emphasis on day-today variations during spring and early summer. During all years studied, significant negative anomalies (“dips”), lasting for several days, have been observed in the data from late May through July. The timing coincides with a draw down of dissolved carbon dioxide and nutrients in the surface waters of the North Atlantic observed by others. By using 3-dimensional trajectories, we follow the history of the air arriving in Ny-Alesund, and show that the air, depleted in CO 2 , had been in contact with these waters. Combining the trajectories with a box model yields a simple Lagrangian model, and we demonstrate that the timing and magnitude of the dips are consistent with the degree of CO 2 saturation of the sea during April to mid-June. In late June and July, the model indicates that a significant portion of the dips must have other causes, e.g., CO 2 uptake in the terrestrial biosphere further south. DOI: 10.1034/j.1600-0889.1996.00004.x

Thirteen years of atmospheric carbon dioxide measurements at Mt. Cimone station, Italy

The atmospheric carbon dioxide concentration has been continuously measured at Mt. Cimone station from March 1979. In this paper a selection scheme is applied to the measured concentrations in order to obtain data representative of background conditions. Monthly averages, expressed in the WMO X-85 scale are calculated from the selected data and analysed by a technique of time series decomposition until december 1991. Monthly values exibit an increasing long-term trend, mainly due to the fossil fuel combustion: over the whole monitoring period the average CO2 growth rate is 1.66 p.p.m.v./y. A seasonal cycle, largely due to the biospheric activity of the northern hemisphere is evident. The estimated average peak-to-peak amplitude is 11.32 p.p.m.v. with a maximum occurring in April and a minimum in August. The seasonal amplitude is found to be decreasing with time, by about 1.5 p.p.m.v. over the entire record: no conclusive interpretations are given about this experimental result. Besides the long-term trend and the seasonal cycle, CO2 interannual variations are observed in the selected record; these correlate negatively with the Southern Oscillation Index (SOI) with a maximum correlation coefficient of 0.6 for a delay of about 7–8 months.

Atmospheric carbon dioxide measurements at Cape Matatula, American Samoa, 1976–1987

The U.S. National Oceanic and Atmospheric Administration (NOAA) has operated a program to continuously monitor atmospheric CO2 at Cape Matatula, American Samoa, since January 1976. This paper describes the basic operational program and reports the data through 1987. Data sets are derived from hourly means which have been selected to represent baseline conditions. All hourly mean CO2 values (with flags indicating data selection status) are archived at NOAA's Geophysical Monitoring for Climatic Change (GMCC) laboratory in Boulder, Colorado; at the Carbon Dioxide Information and Analysis Center in Oak Ridge, Tennessee; and in the microfiche version of this paper. The record from the in situ analyzer is compared with that of flask samples obtained in various ways. The overall 12‐year record shows an average increase of 1.44 parts per million by volume per year. This increase amounts to 61% of the carbon dioxide emitted into the atmosphere by fossil fuel combustion during this period. The record is also characterized by the lack of a prominent seasonal cycle. The CO2 concentrations for the first half of each year are always more variable than the second 6 months, when the wind flow is dominated by strong southeasterly trades. The interannual variability of the CO2 growth rate correlates very well with that observed at other GMCC sites.