CO2 Mixing Ratios Research Articles

Constraining anthropogenic CH4 emissions in Nanjing and the Yangtze River Delta, China, using atmospheric CO2 and CH4 mixing ratios

Methane (CH4) emissions estimated with the Intergovernmental Panel on Climate Change (IPCC) inventory method at the city and regional scale are subject to large uncertainties. In this study, we determined the CH4:CO2 emissions ratio for both Nanjing and the Yangtze River Delta (YRD), using the atmospheric CH4 and CO2 concentrations measured at a suburban site in Nanjing in the winter. The atmospheric estimate of the CH4:CO2 emissions ratio was in reasonable agreement with that calculated using the IPCC method for the YRD (within 20%), but was 200% greater for the municipality of Nanjing. The most likely reason for the discrepancy is that emissions from unmanaged landfills are omitted from the official statistics on garbage production.

Influence of corona discharge on the ozone budget in the tropical free troposphere: a case study of deep convection during GABRIEL

Abstract. Convective redistribution of ozone and its precursors between the boundary layer (BL) and the free troposphere (FT) influences photochemistry, in particular in the middle and upper troposphere (UT). We present a case study of convective transport during the GABRIEL campaign over the tropical rain forest in Suriname in October 2005. During one measurement flight the inflow and outflow regions of a cumulonimbus cloud (Cb) have been characterized. We identified a distinct layer between 9 and 11 km altitude with enhanced mixing ratios of CO, O3, HOx, acetone and acetonitrile. The elevated O3 contradicts the expectation that convective transport brings low-ozone air from the boundary layer to the outflow region. Entrainment of ozone-rich air is estimated to account for 62% (range: 33–91%) of the observed O3. Ozone is enhanced by only 5–6% by photochemical production in the outflow due to enhanced NO from lightning, based on model calculations using observations including the first reported HOx measurements over the tropical rainforest. The "excess" ozone in the outflow is most probably due to direct production by corona discharge associated with lightning. We deduce a production rate of 5.12 × 1028 molecules O3 flash−1 (range: 9.89 × 1026–9.82 × 1028 molecules O3 flash−1), which is at the upper limit of the range reported previously.

Spatial variability of carbon dioxide in the urban canopy layer and implications for flux measurements

This contribution reports CO2 mixing ratios measured in the urban canopy layer (UCL) of a residential neighborhood in Vancouver, BC, Canada and discusses the relevance of UCL CO2 temporal and spatial variability to local-scale eddy covariance (EC) fluxes measured above the UCL. Measurements were conducted from a mobile vehicle-mounted platform over a continuous, 26-h period in the longterm turbulent flux source area of an urban EC tower. Daytime mixing ratios were highest along arterial roads and largely a function of proximity to vehicle traffic CO2 sources. At night, there was a distinct negative correlation between potential air temperature and CO2 mixing ratios. The spatial distribution of CO2 was controlled by topography and micro-scale advective processes (i.e. cold-air pooling). Mobile CO2 measurements were then used to calculate CO2 storage changes (FS) in the UCL volume and compared to single-layer FS estimates calculated from the EC system. In total, five variations of FS were calculated. On average, the choice of FS calculation method affected net measured hourly emissions (FC) by 5.2%. Analysis of FS using a four-year dataset measured at the EC tower show FS was 2.8% of hourly FC for this site on average. At this urban EC location, FS was relatively minor compared to FC and calculation of FS using a single-layer method was adequate, though FS still represents a potentially large uncertainty during individual hours.

Methods and uncertainties in the experimental assessment of horizontal advection

The eddy covariance technique is prone to underestimating the net ecosystem CO2 exchange under stable atmospheric conditions, which mostly occur at night time when other terms of the CO2 mixing ratio conservation equation (i.e. advection) may become significant. Given the potential large impact of night-time flux measurements on the estimation of the ecosystem carbon budget, it is important to develop reliable methodologies for the assessment of advective fluxes. Accurate CO2 concentration gradient measurements are needed for a precise estimation of the advection components. For this purpose a novel measurement system, designed to overcome some of the key issues of CO2 concentration measurements, has been developed and deployed at the IT-Ren eddy covariance site (Renon, BZ, Italy). In particular, the system is optimized for minimizing both the spatial and temporal uncertainty of the CO2 concentration gradients by adopting buffer volumes, a ramified sampling scheme, and a rapid switch between lines.Different configurations of the measurement system were used to quantify the uncertainty of horizontal concentration gradients and to disentangle its sources. The discrete temporal sampling was the major source of uncertainty, accounting for 54% of the total uncertainty, while spatial sampling accounts for 39% of the total uncertainty in stable conditions and for 35% in unstable conditions, with the remaining uncertainty being explained by the accuracy of the instrumental set-up (analyser, pumps and valves) (7% and 11% for stable and unstable atmospheric conditions, respectively, corresponding to ∼0.2ppm). Finally, we investigated the effect of buffer volumes on the uncertainty generated by a discrete temporal sampling in the estimation of horizontal advection. The use of volumes with a mean residence time equal to the turn-over time of the manifold reduced by half the standard deviation in the time series of horizontal advection (from 3.8 to 1.8μmolm−2s−1). The measurement system in its final configuration is currently used to quantify storage and advective fluxes at the site.

Impact of ambient O2(a1Δg) on satellite-based laser remote sensing of O2columns using absorption lines in the 1.27 µm region

Determination of CO2 mixing ratio columns from space using Laser Absorption Spectroscopy (LAS) requires simultaneous measurements of CO2 number density columns and knowledge of the dry atmospheric surface pressure. One approach to determining the surface pressure is to make an LAS column measurement of O2 number density in the 7857.3–7921.7 cm−1 (1.27 µm) region of the O2(1Δ) state. A complicating factor in the LAS O2 measurement is the presence of a permanent but spatially variable natural source of airglow from the O2(1Δ) state. In addition, the laser radiation can induce stimulated emission from the ambient O2(1Δ) state and also cause stimulated absorption and emission from the ground state O2 molecules as the laser beam passes through the atmosphere. Finally, the upwelling surface-reflected solar radiation is an additional source of background radiation. The effects of these additional radiation sources on the LAS measurement of O2 are examined. The surface-reflected solar radiation produces the largest background at 3 orders of magnitude more intense than the laser backscatter signal, while the airglow is of the same order of magnitude as the laser backscatter. The stimulated emission from ambient O2(a1Δg) is found to be about the same order of magnitude as the laser radiation. These effects are evaluated under noon, twilight, and midnight conditions at midlatitudes, the equator, and the pole. The stimulated emission is in the same direction and in phase with the laser signal, its contamination of the LAS O2 measurement prevents a full sunlight determination of surface pressure.

EXTREMELY ORGANIC-RICH COMA OF COMET C/2010 G2 (HILL) DURING ITS OUTBURST IN 2012

We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ≈ 25,000) at the Keck II Telescope on UT 2012 January 9 and 10, about a week after an outburst had occurred. Over the two nights of our observations, prominent emission lines of CH{sub 4} and C{sub 2}H{sub 6}, along with weaker emission lines of H{sub 2}O, HCN, CH{sub 3}OH, and CO were detected. The gas production rate of CO was comparable to that of H{sub 2}O during the outburst. The mixing ratios of CO, HCN, CH{sub 4}, C{sub 2}H{sub 6}, and CH{sub 3}OH with respect to H{sub 2}O were higher than those for normal comets by a factor of five or more. The enrichment of CO and CH{sub 4} in comet Hill suggests that the sublimation of these hypervolatiles sustained the outburst of the comet. Some fraction of water in the inner coma might exist as icy grains that were likely ejected from nucleus by the sublimation of hypervolatiles. Mixing ratios of volatiles in comet Hill are indicative of the interstellar heritage without significant alteration in the solar nebula.

Mercury Plumes in the Global Upper Troposphere Observed during Flights with the CARIBIC Observatory from May 2005 until June 2013

Tropospheric sections of flights with the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrumented Container) observatory from May 2005 until June 2013, are investigated for the occurrence of plumes with elevated Hg concentrations. Additional information on CO, CO2, CH4, NOy, O3, hydrocarbons, halocarbons, acetone and acetonitrile enable us to attribute the plumes to biomass burning, urban/industrial sources or a mixture of both. Altogether, 98 pollution plumes with elevated Hg concentrations and CO mixing ratios were encountered, and the Hg/CO emission ratios for 49 of them could be calculated. Most of the plumes were found over East Asia, in the African equatorial region, over South America and over Pakistan and India. The plumes encountered over equatorial Africa and over South America originate predominantly from biomass burning, as evidenced by the low Hg/CO emission ratios and elevated mixing ratios of acetonitrile, CH3Cl and particle concentrations. The backward trajectories point to the regions around the Rift Valley and the Amazon Basin, with its outskirts, as the source areas. The plumes encountered over East Asia and over Pakistan and India are predominantly of urban/industrial origin, sometimes mixed with products of biomass/biofuel burning. Backward trajectories point mostly to source areas in China and northern India. The Hg/CO2 and Hg/CH4 emission ratios for several plumes are also presented and discussed.

Low Ozone Episodes at Amphitrite Point Marine Boundary Layer Observatory, British Columbia, Canada

ABSTRACTAt Amphitrite Point, ozone (O3) mixing ratios are observed to drop steadily to 5–15 ppb over a period of 12 hours or less with a frequency approaching one event per week (with highest frequencies occurring in summer and fall). Analysis of 47 such O3 depletion events reveals that low O3 episodes are a predominantly nocturnal phenomenon associated with anticyclonic conditions characterized by light onshore or alongshore winds and an absence of fog and mist. Back-trajectories show air carried to the Amphitrite Point Observatory (APO) during depletion events remains in the marine boundary layer and is not brought to the surface from aloft. There is no strong correlation with other “criteria” pollutants (CO, NOx, SO2, PM2.5) that might be indicative of a mechanism for O3 destruction linked to human, terrestrial, or marine pollutant sources. However, CO2 mixing ratios are observed to increase, coincident with O3 depletion. Together, these results point to a natural marine boundary layer phenomenon in which O3 destruction dominates O3 production and/or replenishment by vertical mixing. While there are several candidate mechanisms, the conditions for O3 depletion (and CO2 buildup) to occur are set by meteorology and, in particular, development of a stable marine boundary layer in which vertical mixing is suppressed. Support for this interpretation is provided by simultaneous increases in CO2 in the stable marine boundary that are indicative of an important role played by marine biogenic processes (respiration). Future research should be directed at elucidating the chemical mechanisms responsible for O3 destruction in the coastal zone, which means that there would be a need for a much broader range of measurements at APO (including halogenated species) as well as offshore measurements of both chemical and marine boundary layer meteorological variables.

On the distribution of CO2 and CO in the mesosphere and lower thermosphere

AbstractWe have used the Whole Atmosphere Community Climate Model (WACCM) to calculate the distribution of CO2 and CO in the mesosphere and lower thermosphere (MLT), and we have compared the results with observations, mainly from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer and Michelson Interferometer for Passive Atmospheric Sounding satellite‐borne instruments. We find that WACCM can reproduce the observed distribution of CO2 in the MLT and the rapid falloff of CO2 above about 80 km. Analysis of the principal terms in the calculated budget of CO2 shows that its global‐mean vertical profile is determined mainly by the competition between molecular diffusive separation and eddy mixing by gravity waves. The model underestimates somewhat the mixing ratio of CO2 in the thermosphere compared to that in the observations, but we show that the discrepancy may be eliminated by a reasonable adjustment of the Prandtl number used to calculate the diffusivity due to gravity waves. Simulated CO is also consistent with observations, except that in the standard version of the model, its mixing ratio is uniformly lower than observed above about 100 km. We conclude that WACCM likely underestimates the rate of production of CO in the lower thermosphere from photolysis of CO2 at wavelengths < 121 nm, and we show that this stems from the use of a very large absorption cross section for O2 in the wavelength range 105–121 nm. When a smaller cross section is used, photolysis of CO2 increases by a factor of 2–3 at ~ 95–115 km and, as a result, CO mixing ratios become larger and agree much more closely with observations. We emphasize that the increase in CO2 photolysis implies only minor changes in the vertical profile of CO2 because photolytic loss is a minor term in the budget of CO2 in the MLT.

Observations of CO dayglow at 4.7 μm, CO mixing ratios, and temperatures at 74 and 104–111 km on Venus

The CO dayglow at 4.7μm on Venus has been observed using the long-slit high-resolution spectrograph CSHELL at NASA IRTF with a resolving power of 4×104. The observations covered a latitude range of ±60° at local time of 07:50 at low latitudes. Solar lines in the spectra are used to measure Venus reflectivity which is found to be of 0.077 at 4.7μm. Intensity ratio of the P2, P1, and R1 lines of the CO dayglow at the fundamental band (1-0) differs from that calculated by Crovisier et al. (Crovisier, J., Lellouch, E., de Bergh, C., Maillard, J.P., Lutz, B.L., Bezard, B. [2006]. Planet. Space Sci. 54, 1398–1414) and is closer to that expected at local thermodynamic equilibrium. The CO (1-0) dayglow is optically thick, its intensity weakly depends on the CO abundance and it proves poorly accessible for diagnostics of the Venus atmosphere. Six observed lines of the CO dayglow at the hot (2-1) band show a significant limb brightening typical of an optically thin airglow. Vertical intensities of the CO (2-1) band corrected for viewing angle and the Venus reflection are constant at 3.3MR in the latitude range of ±50° at a solar zenith angle of 64°. Rotational temperatures of the CO (2-1) dayglow should reflect ambient temperature near 111km. The observed temperatures are slightly higher on the south with a mean value of 203K. A model of the CO (2-1) dayglow has been improved. The CO (v=2) molecules are excited by absorption of the sunlight at the CO (2-0) and (3-0) bands at 2.35 and 1.58μm and photolysis of CO2 by the solar Lyman-alpha emission. The dayglow is quenched by CO2, and the calculated mean dayside intensity is 3.1MR. The weighted-mean dayglow altitude is 104km. Variations of the dayglow with CO abundance and solar zenith angle are calculated and presented. Then the model results are used to convert the observed dayglow intensities into CO abundances at 104km. The retrieved CO mixing ratios are constant from 50°S to 50°N with a mean value of 560±100ppm. The observed values of CO and temperatures are compared and discussed with those in other observations and models. Numerous CO and CO2 absorption lines in the observed spectra are used to retrieve CO abundances and temperatures at 74km on Venus. The measured CO mixing ratio is found constant at 40ppm from 50°S to 30°N with a weak increase to the higher latitudes. The temperature at 74km is almost constant at 222.6±3.4K, in perfect agreement with the Venus International Reference Atmosphere (Seiff, A. et al. [1985]. Adv. Space Res. 5, 3–58).

Role of the residual layer and large-scale subsidence on the development and evolution of the convective boundary layer

Abstract. Observations, mixed-layer theory and the Dutch Large-Eddy Simulation model (DALES) are used to analyze the dynamics of the boundary layer during an intensive operational period (1 July 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence campaign. Continuous measurements made by remote sensing and in situ instruments in combination with radio soundings, and measurements done by remotely piloted aircraft systems and two manned aircrafts probed the vertical structure and the temporal evolution of the boundary layer during the campaign. The initial vertical profiles of potential temperature, specific humidity and wind, and the temporal evolution of the surface heat and moisture fluxes prescribed in the models runs are inspired by some of these observations. The research focuses on the role played by the residual layer during the morning transition and by the large-scale subsidence on the evolution of the boundary layer. By using DALES, we show the importance of the dynamics of the boundary layer during the previous night in the development of the boundary layer at the morning. DALES numerical experiments including the residual layer are capable of modeling the observed sudden increase of the boundary-layer depth during the morning transition and the subsequent evolution of the boundary layer. These simulations show a large increase of the entrainment buoyancy flux when the residual layer is incorporated into the mixed layer. We also examine how the inclusion of the residual layer above a shallow convective boundary layer modifies the turbulent kinetic energy budget. Large-scale subsidence mainly acts when the boundary layer is fully developed, and, for the studied day, it is necessary to be considered to reproduce the afternoon observations. Finally, we also investigate how carbon dioxide (CO2) mixing ratio stored the previous night in the residual layer plays a fundamental role in the evolution of the CO2 mixing ratio during the following day.

Anthropogenic changes of CO2, CH4, N2O, CFCl3, CF2Cl2, CCl2FCClF2, CHCl3, CH3CCl3, CCl4, SF6 and SF5CF3 mixing ratios in the atmosphere over southern Poland

800x600 An overview of long-term, systematic observations of trace gas composition of the atmosphere over southern Poland is given. Three major greenhouse gases (CO 2 , CH 4 , N 2 O) and selected halocarbons (freons F-11, F-12 and F-113; chloroform; 1,1,1-trichloroetane; carbon tetrachloride; sulfur hexafluoride and trifluoromethyl sulfur pentafuoride) were monitored. Measurements were performed at two locations of contrasting characteristics: (1) the high-mountain site Kasprowy Wierch, High Tatras, representing atmospheric conditions relatively free of local influences, and (2) two sites located in the Krakow agglomeration, representing a typical urban atmosphere. The data available for Krakow and Kasprowy Wierch were compared with the Mace Head data, representing a marine regional background. The impact of continental sources for some of the measured gases is clearly seen in the Krakow and Kasprowy Wierch records. The mean offset between CH 4 concentrations recorded at Kasprowy Wierch and at Mace Head for the period 1998-2012 is 20.7 ppb and stems from continental emissions of this gas originating mainly from anthropogenic activities (leaks of natural gas distribution networks, landfills, livestock). For N 2 O, a similar offset of ca. 1 ppb for the period 2009-2012 was observed. Although the long-term concentration trends of selected halogenated compounds measured in Krakow coincide in general with the respective trends in Mace Head data, the Krakow records contain numerous spikes and periods of enhanced concentrations, reflecting the impact of local sources of these compounds. The impact of a legislative framework enforced in Poland in July 2002, regulating the trade, storage and disposal of ozone-depleting substances, is visible in the Krakow record of halogenated compounds. Normal 0 21 false false false PL X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;} Normal 0 21 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

Analysis of the PKT correction for direct CO<sub>2</sub> flux measurements over the ocean

Abstract. Eddy covariance measurements of air–sea CO2 fluxes can be affected by cross-sensitivities of the CO2 measurement to water vapour, resulting in order-of-magnitude biases. Well-established causes for these biases are (i) cross-sensitivity of the broadband non-dispersive infrared sensors due to band-broadening and spectral overlap (commercial sensors typically correct for this) and (ii) the effect of air density fluctuations (removed by determining the dry air CO2 mixing ratio). Another bias related to water vapour fluctuations has recently been observed with open-path sensors, attributed to sea salt build-up and water films on sensor optics. Two very different approaches have been used to deal with these water vapour-related biases. Miller et al. (2010) employed a membrane drier to physically eliminate 97% of the water vapour fluctuations in the sample air before it entered a closed-path gas analyser. Prytherch et al. (2010a) employed the empirical (Peter K. Taylor, PKT) post-processing correction to correct open-path sensor data. In this paper, we test these methods side by side using data from the Surface Ocean Aerosol Production (SOAP) experiment in the Southern Ocean. The air–sea CO2 flux was directly measured with four closed-path analysers, two of which were positioned down-stream of a membrane dryer. The CO2 fluxes from the two dried gas analysers matched each other and were in general agreement with common parameterisations. The flux estimates from the un-dried sensors agreed with the dried sensors only during periods with low latent heat flux (≤7 W m−2). When latent heat flux was higher, CO2 flux estimates from the un-dried sensors exhibited large scatter and an order-of-magnitude bias. Applying the PKT correction to the flux data from the un-dried analysers did not remove the bias when compared to the data from the dried gas analyser. The results of this study demonstrate the validity of measuring CO2 fluxes using a pre-dried air stream and show that the PKT correction is not valid for the correction of CO2 fluxes.

The Venus nighttime atmosphere as observed by the VIRTIS‐M instrument. Average fields from the complete infrared data set

AbstractWe present and discuss here the average fields of the Venus atmosphere derived from the nighttime observations in the 1960–2350 cm−1 spectral range by the VIRTIS‐M instrument on board the Venus Express satellite. These fields include: (a) the air temperatures in the 1–100 mbar pressure range (~85–65 km above the surface), (b) the altitude of the clouds top, and (c) the average CO mixing ratio. A new retrieval code based on the Bayesian formalism has been developed and validated on simulated observations, to statistically assess the retrieval capabilities of the scheme once applied to the VIRTIS data. The same code has then been used to process the entire VIRTIS‐M data set. Resulting individual retrievals have been binned on the basis of local time and latitude, to create average fields. Air temperature fields confirm the general trends previously reported in Grassi et al. (2010), using a simplified retrieval scheme and a more limited data set. At the lowest altitudes probed by VIRTIS (~65 km), air temperatures are strongly asymmetric around midnight, with a pronounced minima at 3LT, 70°S. Moving to higher levels, the air temperatures first become more uniform in local time (~75 km), then display a colder region on the evening side at the upper boundary of VIRTIS sensitivity range (~80 km). As already shown by Ignatiev et al. (2008) for the dayside, the cloud effective altitude increases monotonically from the south pole to the equator. However, the variations observed in night data are consistent with an overall variation of just 1 km, much smaller than the 4 km reported for the dayside. The cloud altitudes appear slightly higher on the evening side. Both observations are consistent with a less vigorous meridional circulation on the nightside of the planet. Carbon monoxide is not strongly constrained by the VIRTIS‐M data. However, average fields present a clear maximum of 80 ppm around 60°S, well above the retrieval uncertainty. Once the intrinsic low sensitivity of VIRTIS data in the region of cold collar is kept in mind, this datum is consistent with a [CO] enrichment toward the poles driven by meridional circulation.

Retrieval of column-averaged volume mixing ratio of CO2 with ground-based high spectral resolution solar absorption

The total column-averaged volume mixing ratio of atmospheric carbon dioxide (\( {\text{X}}_{{{\text{CO}}_{ 2} }} \)) has been retrieved with high spectral resolution solar absorption data obtained from ground-based Fourier transform spectrometer (FTS) measurements at Xichong, a coastal site in the district of Shenzhen in southern China. Based on differential optical absorption spectroscopy (DOAS) theory, the \( {\text{X}}_{{{\text{CO}}_{ 2} }} \) was retrieved by finding the best match of observed high spectral resolution solar absorption data and monochromatic radiation transfer model calculations. The averaged \( {\text{X}}_{{{\text{CO}}_{ 2} }} \) in the whole observation period was about 394.9 ppm. The uncertainty of the retrieval was estimated to be 2.0 ppm (0.51 %) by comparing retrievals at two bands. The preliminary results show that \( {\text{X}}_{{{\text{CO}}_{ 2} }} \) retrieved by this method can be used to validate satellite remote sensing of \( {\text{X}}_{{{\text{CO}}_{ 2} }} .\)

Volcanic CO2 flux measurement at Campi Flegrei by tunable diode laser absorption spectroscopy

Near-infrared room temperature tunable diode lasers (TDL) have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in volcanology are still limited to a few examples. Here, we explored the potential of a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) for measurement of volcanic CO2 mixing ratios, and ultimately for estimating the volcanic CO2 flux. Our field tests were conducted at Campi Flegrei near Pozzuoli, Southern Italy, where the GasFinder was used during three campaigns in October 2012, January 2013 and May 2013 to repeatedly measure the path-integrated mixing ratios of CO2 along cross sections of the atmospheric plumes of two major fumarolic fields (Solfatara and Pisciarelli). By using a tomographic post-processing routine, we resolved, for each of the two fields, the contour maps of CO2 mixing ratios in the atmosphere, from the integration of which (and after multiplication by the plumes’ transport speeds) the CO2 fluxes were finally obtained. We evaluate a total CO2 output from the Campi Flegrei fumaroles of ∼490 Mg/day, in line with independent estimates based on in situ (Multi-GAS) observations. We conclude that TDL technique may enable CO2 flux quantification at other volcanoes worldwide.

Temporal changes in the emissions of CH<sub>4</sub> and CO from China estimated from CH<sub>4</sub> / CO<sub>2</sub> and CO / CO<sub>2</sub> correlations observed at Hateruma Island

Abstract. In situ observation of the atmospheric CO2, CH4, and CO mixing ratios at Hateruma Island (HAT, 24.05° N, 123.80° E) often show synoptic-scale variations with correlative elevations during winter, associated with air transport from the East Asian countries. We examine winter (November– March) trends in ΔCH4 / ΔCO2, ΔCO / ΔCO2, and ΔCO / ΔCH4 observed at Hateruma over the period 1999 to 2010. To investigate the relationship between the East Asian emissions and the short-term variations in the atmospheric mixing ratios, we use the FLEXPART Lagrangian particle dispersion model (LPDM). The observed ratios ΔCH4 / ΔCO2 and ΔCO / ΔCO2 both show an overall gradual decrease over the study period due to a recent rapid increase in fossil fuel consumption in China. We note, however, that the decreasing rates of ΔCH4 / ΔCO2 and ΔCO / ΔCO2 show gradual decrease and increase, respectively, during the entire observation periods used in this study. The ΔCO / ΔCH4 slope, on the other hand, shows an increasing trend during 1999–2004 but a decrease during 2005–2010. Calculation of the concentration footprint for the atmospheric observation at HAT by using the FLEXPART LPDM indicates that most of the short-term variations are caused by emission variations from northern and eastern China. Combined with a set of reported emission maps, we have estimated the temporal changes in the annual CH4 and CO emissions from China under the assumption that the estimate of the fossil-fuel-derived CO2 emissions based on the energy statistics are accurate. The estimated annual CH4 emissions, corresponding to nonseasonal sources or anthropogenic sources without rice fields, show a nearly constant value of 39 ± 7 TgCH4 yr−1 during 1998–2002, and then gradually increase to 46 ± 8 TgCH4 yr−1 in 2009/2010. The estimated annual CO emissions increase from 134 ± 32 TgCO yr−1 in 1998/1999 to 182 ± 42 TgCO yr−1 in 2004/2005, level off after 2005, and then slightly decrease to less than 160 TgCO yr−1 in 2008–2010.

Constraining surface carbon fluxes using in situ measurements of carbonyl sulfide and carbon dioxide

AbstractUnderstanding the processes that control the terrestrial exchange of carbon is critical for assessing atmospheric CO2 budgets. Carbonyl sulfide (COS) is taken up by vegetation during photosynthesis following a pathway that mirrors CO2 but has a small or nonexistent emission component, providing a possible tracer for gross primary production. Field measurements of COS and CO2 mixing ratios were made in forest, senescent grassland, and riparian ecosystems using a laser absorption spectrometer installed in a mobile trailer. Measurements of leaf fluxes with a branch‐bag gas‐exchange system were made across species from 10 genera of trees, and soil fluxes were measured with a flow‐through chamber. These data show (1) the existence of a narrow normalized daytime uptake ratio of COS to CO2 across vascular plant species of 1.7, providing critical information for the application of COS to estimate photosynthetic CO2 fluxes and (2) a temperature‐dependent normalized uptake ratio of COS to CO2 from soils. Significant nighttime uptake of COS was observed in broad‐leafed species and revealed active stomatal opening prior to sunrise. Continuous high‐resolution joint measurements of COS and CO2 concentrations in the boundary layer are used here alongside the flux measurements to partition the influence that leaf and soil fluxes and entrainment of air from above have on the surface carbon budget. The results provide a number of critical constraints on the processes that control surface COS exchange, which can be used to diagnose the robustness of global models that are beginning to use COS to constrain terrestrial carbon exchange.

THE EFFECT OF CARBON MONOXIDE ON PLANETARY HAZE FORMATION

Organic haze plays a key role in many planetary processes ranging from influencing the radiation budget of an atmosphere to serving as a source of prebiotic molecules on the surface. Numerous experiments have investigated the aerosols produced by exposing mixtures of N$_{2}$/CH$_{4}$ to a variety of energy sources. However, many N$_{2}$/CH$_{4}$ atmospheres in both our solar system and extrasolar planetary systems also contain CO. We have conducted a series of atmosphere simulation experiments to investigate the effect of CO on formation and particle size of planetary haze analogues for a range of CO mixing ratios using two different energy sources, spark discharge and UV. We find that CO strongly affects both number density and particle size of the aerosols produced in our experiments and indicates that CO may play an important, previously unexplored, role in aerosol chemistry in planetary atmospheres.

Recent Springtime Regional CO Variability in Southern China and the Adjacent Ocean: Anthropogenic and Biomass Burning Contribution

ABSTRACTSpringtime regional CO variability in the boundary layer and lower free troposphere in recent years has been studied by a combination of chemical transport models, satellite retrievals and surface-based measurements. Based upon the surface-level measurements and satellite observations, the CO mixing ratios and column densities downwind of the continental outflow were found to have significant reductions in the springtime of 2009 and 2010. Under the influence of continental outflow, there were 58% and 38% decreases in the monthly mean mixing ratios at a rural coastal site in March and April 2009–10, respectively, compared to the 2007–08 figure. Other than the global economic recession, the CO reductions downwind are attributed to the recent implementation of effective anthropogenic CO emissions control in China. The CO simulations by the MM5-CMAQ modeling system with fixed annual emissions support this argument. Features of frontal passage, including the higher CO mixing ratios in the post-frontal stage, were well-captured by the modeling system. The high-resolution nested-grid GEOS-Chem model was used to better characterize the downwind influences of CO due to the biomass burning in Southeast Asia in March and April 2008. The computed CO mixing ratios agreed well with satellite observations at 700 hPa during selected episodes when intense biomass burning activities in Southeast Asia were observed by the satellite images. The biomass-burning-derived CO provided a large contribution (33–86%) to the total CO mixing ratio in the lower free troposphere downwind over the South China Sea and western Pacific Ocean, based on the modeling results. Vertical export of CO in active convection events near the source region was evident.