CO Profiles Research Articles

Biosphere Atmosphere Exchange of CO2, H2O Vapour and Energy during Spring over a High Altitude Himalayan Forest in Eastern India

For the first time, the exchange of greenhouse gases, such as CO2 and H2O vapour, between the biosphere and the atmosphere at an eastern Himalayan site in India has been investigated. This study was carried out over a high altitude (2286 m asl) evergreen coniferous forest (27.04°N, 88.08°E), where we measured the fluxes of CO2 and H2O vapour along with the sensible and latent energy using the eddy covariance method both above (38 m) and within (8 m) the canopy, the soil-CO2 flux and the vertical profile of CO2 during spring (March–April) in 2015. The mean eddy flux of CO2 above the canopy was –2.8 ± 6.5 µmol m–2 s–1, whereas it was 0.6 ± 0.4 µmol m–2 s–1 within the canopy. The mean flux of H2O vapour above the canopy (1.5 ± 1.8 mmol m–2 s–1) was three times higher than within the canopy (0.5 ± 0.6 mmol m–2 s–1). The mean flux of CO2 emitted from the soil surface was 1.6 ± 0.1 µmol m–2 s–1. The diurnal variation showed high sequestration of CO2 during daytime, when the negative flux increased beyond –10 µmol m–2 s–1. We observed that precipitation significantly enhanced CO2 sequestration (by approximately fourfold) as well as H2O vapour emissions (by approximately threefold) by the tall canopies. Overall, during the entire study period, the net ecosystem exchange (NEE) was –656.5 g CO2 m–2, suggesting that the evergreen coniferous forest in the eastern Himalaya acts as a net sink of CO2 during spring. Therefore, we can estimate the sequestration of anthropogenic carbon emission by the eastern Himalayan forest ecosystem, improving the national greenhouse gas inventory.

Method for Controlling Temperature Profiles and Water Table Depths in Laboratory Sediment Columns

Author(s): Tokunaga, TK; Kim, Y; Wan, J; Bill, M; Conrad, M; Dong, W | Abstract: Transport from the soil surface to groundwater is commonly mediated through deeper portions of the vadose zone and capillary fringe, where variations in temperature and water saturation strongly influence biogeochemical processes. This technical note describes a sediment column design that allows laboratory simulation of thermal and hydrologic conditions found in many field settings. Temperature control is particularly important because room temperature is not representative of most subsurface environments. A 2.0-m-tall column was capable of simulating profiles with temperatures ranging from 3 to 22°C, encompassing the full range of seasonal temperature variation observed in the deep vadose zone and capillary fringe of a semiarid floodplain in western Colorado. The water table was varied within the lower 0.8-m section of the column, and profiles of water content and matric potential were measured. Vadose zone CO2 collected from depth-distributed gas samplers under representative seasonal conditions reflected the influences of temperature and water table depth on microbial respiration. Thus, realistic subsurface biogeochemical dynamics can be simulated in the laboratory through establishing column profiles that represent seasonal thermal and hydrologic conditions.

Evaluation of forest CO2 fluxes from sonde measurements in three different climatological areas including Borneo, Malaysia, and Iriomote and Hokkaido, Japan

Evaluation of carbon dioxide (CO2) sinks in forest areas of East and Southeast Asia (especially tropical regions) is important for assessing CO2 budgets at the regional scale. To evaluate the CO2 flux of large forest areas, we collected vertical CO2 profiles over the forest using a CO2 sonde and measured surface CO2 concentrations around the forest using continuous CO2 measurement equipment. These observations were performed over a typical northern forest (Hokkaido) in Japan, a subtropical forest island (Iriomote Island) in Japan, and a tropical forest in Borneo Island. We detected the differences in CO2 vertical profiles between dawn and daytime, and at the upwind and downwind sites of the forests with the observational results from the CO2 sonde. We also clarified that CO2 concentrations during daytime at the downwind sites (affected by the forest) were systematically lower than those at the upwind sites (not affected by the forest). In contrast, CO2 concentrations during dawn at the downwind sites were larger than those at the upwind site. We estimated the CO2 fluxes (μmol m−2 s−1) at dawn and daytime of the forests from these observational results. The CO2 fluxes of Borneo’s forest were very large (16.5 and −37.7 at dawn and daytime, respectively), whereas the CO2 fluxes of the forests in Hokkaido and Iriomote were lower (3.9 to 11.8 at dawn and −11.8 to −15.0 at daytime). These evaluated values were consistent with fluxes measured by the eddy-covariance method in the same region. Thus, use of the CO2 sonde to collect observations of CO2 vertical profiles was considered to be an effective method to verify CO2 absorption and emission in large forest areas. This method can also be used to evaluate dynamic CO2 absorption and emission processes in tropical forests.

Experimental studies of nitromethane flames and evaluation of kinetic mechanisms

The present work reports new experimental data for premixed flames of nitromethane, CH3NO2, at atmospheric pressure, and an evaluation of two contemporary kinetic mechanisms based on these new flame studies as well as previously published experimental data on laminar burning velocity and ignition. Flames of nitromethane + air at lean (ϕ = 0.8) and rich (ϕ = 1.2) conditions were stabilized on a flat-flame burner, where profiles of CH2O, CO and NO were obtained using laser-induced fluorescence and temperature profiles using coherent anti-Stokes Raman spectroscopy. Laminar burning velocities for nitromethane + O2 + CO2 were measured using the heat flux method for ϕ = 0.8–1.3 at 348 K and ϕ = 0.8–1.6 at 358 K, and an oxidizer composition of 35% O2 and 65% CO2. In addition, the effect of the oxidizer composition was examined for a stoichiometric flame at 358 K by varying oxygen fraction from 30% to 40%. The mechanism by Mathieu et al. (Fuel 2016, 182, 597), previously not validated for flames, was able to reproduce experimental laminar burning velocities for nitromethane + air, but under predicted new results for CH3NO2 + O2 + CO2 mixtures. The mechanism by Brequigny et al. (Proc. Combust. Inst. 2014, 35, 703) under predicted experimental laminar burning velocities significantly at all investigated conditions. Previous studies have shown that none of the mechanisms can accurately predict ignition delay time over a wide range of conditions with respect to pressure, temperature, diluent and dilution ratio. The evaluation of the mechanisms reveals that the understanding of nitromethane combustion is at the present time not sufficient to produce a widely applicable mechanism.

The profile of the bending mode band in solid CO2

Context. Solid carbon dioxide (CO2 ) is one of the most abundant species detected in icy grain mantles in dense molecular clouds. Its identification is based on the comparison between astronomical and laboratory spectra. In the past 30 yr the profile of solid CO2 infrared absorption bands has been extensively studied experimentally, however, the debate on the structure (amorphous versus crystalline) of CO2 samples obtained in laboratory by the thin-film technique is still open.Aims. The aim of this work is to investigate if the presence of the double peak feature in the profile of the CO2 bending mode band is related to the crystalline or amorphous structure of the sample.Methods. We performed new laboratory experiments depositing CO2 under ultra high vacuum (UHV) conditions at 17 K. We investigated, using infrared transmission spectroscopy, the influence of various experimental parameters on the profile of the CO2 bands, namely deposition rate, sample thickness, annealing, and presence of H2 O, CH3 OH or CO co-deposited with CO2 . Results. We found that, within experimental uncertainties, under UHV conditions the profile of the CO2 bands in pure solid samples does not depend on the deposition rate or the sample thickness in the ranges investigated. In all cases the bending mode band profile shows a double peak (at 660 and 655 cm-1 ). The spectra also show the Fermi resonance features that cannot be active in crystalline samples. On the other hand, when a small fraction of H2 O or CH3 OH is co-deposited with CO2 the double peak is not observed while it is observed when a CO2 :CO mixture is considered. Furthermore, we measured the density of solid CO2 and the refractive index (at 543.5 nm) at 17 K and at 70 K: ρ (17 K)= 1.17 g cm-3 , ρ (70K)= 1.49 g cm-3 , n (17K)= 1.285, and n (70K)= 1.372. Conclusions. Our experimental results indicate that the presence of the double peak in the profile of the bending mode band is not an indication of a crystalline structure of the sample and they do not exclude the presence of amorphous solid CO2 in space.

Detection of CS in Neptune’s atmosphere from ALMA observations

Context. The large and vertically non-uniform abundance of CO in Neptune’s atmosphere has been interpreted as the result of past cometary impact(s), either single or distributed in size and time, which could also be at the origin of Neptune’s HCN. Aims. We aim to provide observational support for this scenario by searching for other comet-induced species, in particular carbon sulfide (CS) which has been observed continuously in Jupiter since the 1994 Shoemaker-Levy 9 impacts. Methods. In April 2016 we used the ALMA interferometer to search for CS(7-6) at 342.883 GHz in Neptune. Results. We report on the detection of CS in Neptune’s atmosphere, the first unambiguous observation of a sulfur-bearing species in a giant planet beyond Jupiter. Carbon sulfide appears to be present only at submillibar levels, with a column density of (2.0–3.1) × 1012 cm-2, and a typical mixing ratio of (2−20) × 10-11 that depends on its precise vertical location. The favoured origin of CS is deposition by a putative large comet impact several centuries ago, and the strong depletion of CS with respect to CO – compared to the Jupiter case – is likely due to the CS sticking to aerosols or clustering to form polymers in Neptune’s lower stratosphere. Conclusions. The CS detection, along with recent analyses of the CO profile, reinforces the presumption of a large comet impact into Neptune ~1000 yr ago, that delivered CO, CS, and HCN at the same time.

Composition and Chemistry of the Neutral Atmosphere of Venus

This paper deals with the composition and chemical processes occurring in the neutral atmosphere of Venus. Since the last synthesis, observers as well as modellers have emphasised the spatial and temporal variability of minor species, going beyond a static and uniform picture that may have prevailed in the past. The outline of this paper acknowledges this situation and follows closely the different dimensions along which variability in composition can be observed: vertical, latitudinal, longitudinal, temporal. The strong differences between the atmosphere below and above the cloud layers also dictate the structure of this paper. Observational constraints, obtained from both Earth and Venus Express, as well as 1D, 2D and 3D models results obtained since 1997 are also extensively referred and commented by the authors. An non-exhaustive list of topics included follows: modelled and observed latitudinal and vertical profiles of CO and OCS below the clouds of Venus; vertical profiles of CO and SO2 above the clouds as observed by solar occultation and modelled; temporal and spatial variability of sulphur oxides above the clouds. As a conclusion, open questions and topics of interest for further studies are discussed.

Experimental measurements of the interdiffusivities in fcc Co–rich Co–Ti, Co–W and Co–Ti–W systems

Utilizing 8 bulk single–phase diffusion couples together with the electron probe microanalysis technique, the composition–distance profiles of fcc binary Co–Ti and Co–W systems as well as ternary Co–Ti–W system at 1373K were first measured. The measured composition profiles for Co–rich Co–Ti, Co–W and Co–Ti–W systems at 1373K were then adopted to evaluate the corresponding binary and ternary interdiffusivities by using the newly proposed pragmatic numerical inverse method. The comprehensive comparisons between various model–predicted diffusion properties based on the evaluated interdiffusivities due to the pragmatic numerical inverse method, including composition profiles, interdiffusion fluxes and diffusion paths, and the experimental data were conducted to validate their reliability. Moreover, the presently obtained binary and ternary interdiffusivities by the numerical inverse method were further validated by the literature data and the calculated results by using the traditional Sauer–Freise method and Matano–Kirkaldy method.

Pollutant emissions and diesel oxidation catalyst performance at low ambient temperatures in transient load conditions

In this paper an experimental analysis of the ambient temperature effect on diesel engine pollutant emissions is carried out. The study is focused on hydrocarbons and carbon monoxide of both engine out pollutants formation analysis and diesel oxidation catalyzer (DOC) performance. The experiments were carried out at transient engine load conditions of Worldwide harmonized Light vehicles Test Cycle (WLTC) at two levels of ambient temperature: 20 °C and −7 °C. The study presented in this work shows significant different results depending on the pollutant analysed. Regarding hydrocarbons, a significant dependence of pollutant formation on ambient temperature is observed, being the emissions at −7 °C between two and three times the emissions at 20 °C. The DOC performance between temperatures shows similar conversion efficiency. In the case of carbon monoxide formation, temperature dependence plays a less important role than the engine load conditions. The reduction of air fuel ratio at transient conditions drives to unsteady CO profiles emissions along the WLTC that reduce the pollutant conversion with a greater negative impact at −7 °C.

Seasonal Variation of CO2 Vertical Distribution in the Atmospheric Boundary Layer and Impact of Meteorological Parameters

This paper presents the seasonality of vertical profiles of CO2 within 0–1100 m at a suburban site and discussions on the impacts of meteorological parameters on it. CO2 concentrations as well as metrological conditions were measured on June 2–18, July 7–22 (21 days, summer), October 10–20 (10 days, autumn) in 2012, and January 15–February 1 (12 days, winter), May 7–23 (10 days, spring) in 2013. The CO2 vertical profiles were affected by meteorological conditions, source emissions, urban canopy and other factors. The CO2 concentrations’ comparison analysis between different seasons including spring, summer (previously published results), autumn and winter suggests that the highest peak of the CO2 concentration (450.00 ± 14.78 ppm) occurred during winter (2013-01-23 at 09:00–09:55) with neutral stability class whereas the lowest peak of the CO2 concentration (389.88 ± 4.67 ppm) occurred during summer (2012-07-17 at 15:48–16:40) with moderately stable conditions. The high levels of CO2 concentrations were due to the accumulation caused by the stable atmosphere dominant during the measurement period. Atmospheric CO2 concentrations in summer can be lower near the surface than at elevated altitude under certain conditions because terrestrial photosynthesis dominated the industrial pollutant emissions at that time. However, in other seasons, CO2 profiles showed monotonically declining trends with altitudes.

Numerical simulation of aqueous ammonia-based CO2 absorption in a sprayer tower: An integrated model combining gas-liquid hydrodynamics and chemistry

CO2 capture in the spray tower using aqueous ammonia solution has been proved a potential approach for the post-combustion CO2 capture. To improve the performance of spray absorption, a new three-dimensional numerical model integrating the complex gas-liquid hydrodynamics and the chemistry of the NH3-CO2-H2O system has been proposed and developed in this paper. In the model, the gas-liquid hydrodynamics was simulated using the Euler-Lagrange method, while the chemistry of the NH3-CO2-H2O system, including both thermodynamic and kinetic characteristics, was modeled using user-defined modules implemented in the CFD package. Moreover, a laboratory scale spray absorption system was built, and run under various operating conditions were carried out in order to validate the model developed. Subsequently, the predicted results using different kinetic models were compared with the experimental results. It was found the model using Liu’s kinetics showed a better agreement with the experiments, especially when the liquid temperature and NH3 concentration of solution vary. Furthermore, the validated model was used to study the fundamentals of spray absorption. It has been found that the gas temperature profile as well as gaseous CO2 and NH3 concentration profile depends on the velocity field, indicating the hydrodynamics should be considered when optimizing the design of reactor. It has also been found that the residence time of droplets increases with the increase of gas flow rate, leading to an increase in average droplets temperature and CO2 loading, while the increase of ammonia concentration of solution could significantly improve the overall CO2 mass transfer coefficient. When the solution temperature increases from 293 K to 303 K, the overall CO2 mass transfer coefficient gradually increases, resulting in CO2 removal efficiency improvement. However, when the solution temperature increases from 303 K to 313 K, the promotion of reverse reaction leads to the reduction of CO2 removal efficiency. In addition, the increase of ammonia solution flow rate would mainly increase the interphase area and promote both CO2 absorption and NH3 escape. The model developed in this paper can be used to optimize the design and operation of such reactors in practice.

Pyrolysis of Olive Mill Waste with On-line and Ex-post Analysis

Olive mill wastes constitute a serious environmental problem in the Mediterranean region due to the unique features associated with this type of agricultural waste. Therefore, it is not surprising that research efforts have been directed towards developing efficient treatment technologies including various physical–chemical processes. In this paper we present a thermo-chemical degradation method (pyrolysis) to produce biochar. The large part of work is devoted to understand the pyrolysis processes using on-line analysis of thermal parameters and chemical composition. The originality of our work resides in the on-line analysis in the form of temperature measurements during individual pyrolysis cycles as well as the whole pyrolysis process, accompanied with on-line measurements of component concentrations during the whole pyrolysis process. On-line and ex-post analysis of gas phase composition provides important information about environmental impacts of the pyrolyzing process. The concentration profiles of CO, CO2, CH4, H2 and NOX were measured at four locations within the pilot system with a high sampling frequency (every 8 s) during whole pyrolysis process. In terms of the general aspects and possible future application of pyrolysis and its products we propose a novel method capable to reduce carbon dioxide concentrations in pyrolysis gas. The average CO2 removal efficiency during the whole pyrolysis process was as high as 65%. The final product is solid proteinoid. The pyrolysis process decrease the amont of waste to 10% of input amount of material. The carbon char produced in the system may find several applications especially in the agriculture.

Using a Bayesian framework to account for advection in seven years of snowpack CO2 fluxes in a mortality-impacted subalpine forest

In subalpine forests where snowpacks can persist for 50% of the year or longer, wintertime subnivean soil respiration constitutes a significant, but poorly understood, portion of the carbon (C) cycle. The temporal and seasonal dynamics of this flux are difficult to measure compared to snow-free respiration. This makes it challenging to fully address key knowledge gaps in high-elevation forests, including effects of tree mortality on ecosystem C fluxes. Our paper attempts to overcome these challenges by developing a new method for estimating wintertime CO2 flux from soil underneath winter snowpack based on CO2 profiles in the snow and using this to examine potential effects of a tree mortality event on wintertime respiration. The chief problem for estimates based on snow CO2 measurements is that during strong winds, vertical CO2 profiles can depart significantly from linearity, resulting in CO2 fluxes that are not steady-state diffusive fluxes. Consequently, these fluxes include an advective component induced by wind and atmospheric pressure, resulting in above-snowpack fluxes that may be temporally decoupled from biological flux production in the soil. These advective fluxes lead to errors in estimates of the total amount of CO2 produced from the soil surface during the winter, and may complicate the detection of significant seasonal and interannual trends in snowpack CO2 fluxes. Our goal was twofold: first, to improve methods for estimating wintertime subnivean soil respiration; and second, to use this new method to examine potential effects of forest mortality on respiration. We develop a Bayesian-based model of CO2 snowpack profiles and accounts for CO2 storage flux within the snowpack to calculate diffusive and advective fluxes from both the bottom and the top of the snowpack. We apply this model to hourly snowpack CO2 profile data collected over 7 years at an AmeriFlux eddy covariance (EC) site in a Wyoming subalpine forest that had recently experienced a mass tree mortality event. Hourly advective fluxes from the snowpack surface are less variable over time than hourly EC fluxes. Nonetheless, on a daily time scale, the two methods agree well with each other. We found that soil biological CO2 production entering the bottom of snowpack peaked 3 years after the onset of the bark beetle outbreak and 1-year after dead trees dropped their needles, presenting the first evidence of a short-term increase in respiration following bark beetle mortality. Our findings emphasize the importance of accounting for the role of wind-driven advection in wintertime respiration and suggest that tree mortality may nearly double wintertime respiration in the first few years.

Propagation of sub-atmospheric methyl formate flames

Laminar flame speeds of methyl formate/air mixtures were measured at sub-atmospheric pressures for which limited data exist. The experiments were carried out in the counterflow configuration at an unburned mixture temperature of 333 K. The flow velocities were measured using particle image velocimetry. Particle phase slip correction was applied to low-pressure data sets for which the density disparity between the flow tracers and the gaseous phase is notable. The data were modeled using two recently developed kinetic models of methyl formate oxidation, and significant disagreements were realized at all pressures especially under fuel-rich conditions. Additionally, the computed species profiles of CO and CO2 in the burner-stabilized flame configuration using the two models were found to differ significantly. Reaction path analysis revealed that the kinetics of CH2OCHO that is produced directly from the fuel affects the overall reactivity, and the attendant rate constants differ between the two models. The variation of laminar flame speed with pressure revealed also a different behavior between experiments and simulations. Further insight into the sources causing the observed discrepancies were investigated and it was determined that reactions involving formyl radical, methanol, and formaldehyde could also be responsible for the reduction in reactivity specifically under fuel-rich conditions.

ALMA + VLT observations of a damped Lyman-α absorbing galaxy: massive, wide CO emission, gas-rich but with very low SFR

We are undertaking an ALMA survey of molecular gas in galaxies selected for their strong HI absorption, so-called DLA/sub-DLA galaxies. Here we report CO(2-1) detection from a DLA galaxy at z = 0.716. We also present optical and near-infrared spectra of the galaxy revealing [OII], H{\alpha} and [NII] emission lines shifted by ~170 km/s relative to the DLA, and providing an oxygen abundance 3.2 times solar, similar to the absorption metallicity. We report low unobscured SFR ~1 Msun/yr given the large reservoir of molecular gas, and also modest obscured SFR=4.5(+4.4,-2.6) Msun/yr based on far-IR and sub-mm data. We determine mass components of the galaxy: log[M*/Msun] = 10.80(+0.07,-0.14), log[M mol-gas/Msun] = 10.37 +/-0.04, and log[M dust/Msun] = 8.45(+0.10,-0.30). Surprisingly, this HI absorption-selected galaxy has no equivalent objects in CO surveys of flux-selected samples. The galaxy falls off current scaling relations for the SFR to molecular gas mass and CO Tully-Fisher relation. Detailed comparison of kinematical components of the absorbing, ionized and molecular gas, combined with their spatial distribution, suggests that part of the CO gas is both kinematically and spatially de-coupled from the main galaxy. It is thus possible that a major star burst in the past could explain the wide CO profile as well as the low SFR. Support for this also comes from the SED favouring an instantaneous burst of age ~0.5 Gyr. Our survey will establish whether flux-selected surveys of molecular gas are missing a key stage in the evolution of galaxies and their conversion of gas to stars.

A CO2Profile Retrieving Method Based on Chebyshev Fitting for Ground-Based DIAL

The vertical profile of atmospheric CO2 is of great scientific significance in identifying carbon sinks and sources, and estimating CO2 emissions or uptakes. Differential absorption Light Detection And Ranging (DIAL), has been widely accepted as the most promising technique to sense atmospheric CO2. The classical method to retrieve measurements, generated from range-resolved detection, is derived from differentiating the measured column content, but its performance in dealing with aerosol backscatter signals is poor. To address this issue, this paper proposes a derivative method, which is based on Chebyshev fitting to the measured differential absorption optical depth. We created a performance evaluation model to assess the performance of the proposed method. Simulations revealed that the error of a single CO2 profile in data retrieval can be reduced to less than 4 ppm in 6000 m. The precision of long-term mean CO2 profile is expected to be less than 1 ppm. We believe that this novel method can be used in other applications also, e.g., trace gas measurements collected using DIAL, especially when the signal-to-noise-ratio of received signal is small.

The Technique Analysis of CO2 in Troposphere using AIRS

Currently global warming has become an international issue. One of the biggest contributors to global warming is carbon dioxide (CO2). CO2 gas is one of the most prominent gases of greenhouse gases or greenhouse gases in the atmosphere and has an important role in the Earth's climate. Increased CO2 contributes more than 50% to the effects of global warming. Various methods and measuring instruments of CO2 concentration developed from optical sensors to measuring CO2 directly from space using satellites. Atmosphere Infrared Sounder (AIRS) is one of NASA's six (6) instances launched on May 4, 2002 installed on the AQUA satellite. This instrument uses sounding technology that determines the vertical profile of CO2 from space. This instrument supports climate-related research and also in improving weather forecasts. AIRS data can be obtained online from the Giovanni Website at http://giovanni.gsfc.nasa.gov. Giovani is an application provided by NASA to make it easier to acquire, visualize, and analyze remote sensing data with ASCII data facilities that can be downloaded directly. The purpose of this research is to conduct CO2 analysis in Indonesia online using Giovanni Website year 2013-2016. Rendering data online shows the CO2 fluctuated every month, but yearly data shows the CO2 increased signifantly and the higest value in 2016, its reach 4.039 ppm. The results of CO2 analysis is expected to assist in the process of prevention or reduction of CO2 emissions in the air as one of the activities of environmental conservation.

Bias assessment of lower and middle tropospheric CO<sub>2</sub> concentrations of GOSAT/TANSO-FTS TIR version 1 product

Abstract. CO2 observations in the free troposphere can be useful for constraining CO2 source and sink estimates at the surface since they represent CO2 concentrations away from point source emissions. The thermal infrared (TIR) band of the Thermal and Near Infrared Sensor for Carbon Observation (TANSO) Fourier transform spectrometer (FTS) on board the Greenhouse Gases Observing Satellite (GOSAT) has been observing global CO2 concentrations in the free troposphere for about 8 years and thus could provide a dataset with which to evaluate the vertical transport of CO2 from the surface to the upper atmosphere. This study evaluated biases in the TIR version 1 (V1) CO2 product in the lower troposphere (LT) and the middle troposphere (MT) (736–287 hPa), on the basis of comparisons with CO2 profiles obtained over airports using Continuous CO2 Measuring Equipment (CME) in the Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL) project. Bias-correction values are presented for TIR CO2 data for each pressure layer in the LT and MT regions during each season and in each latitude band: 40–20° S, 20° S–20° N, 20–40° N, and 40–60° N. TIR V1 CO2 data had consistent negative biases of 1–1.5 % compared with CME CO2 data in the LT and MT regions, with the largest negative biases at 541–398 hPa, partly due to the use of 10 µm CO2 absorption band in conjunction with 15 and 9 µm absorption bands in the V1 retrieval algorithm. Global comparisons between TIR CO2 data to which the bias-correction values were applied and CO2 data simulated by a transport model based on the Nonhydrostatic ICosahedral Atmospheric Model (NICAM-TM) confirmed the validity of the bias-correction values evaluated over airports in limited areas. In low latitudes in the upper MT region (398–287 hPa), however, TIR CO2 data in northern summer were overcorrected by these bias-correction values; this is because the bias-correction values were determined using comparisons mainly over airports in Southeast Asia, where CO2 concentrations in the upper atmosphere display relatively large variations due to strong updrafts.

Comparison of the GOSAT TANSO-FTS TIR CH<sub>4</sub> volume mixing ratio vertical profiles with those measured by ACE-FTS, ESA MIPAS, IMK-IAA MIPAS, and 16 NDACC stations

Abstract. The primary instrument on the Greenhouse gases Observing SATellite (GOSAT) is the Thermal And Near infrared Sensor for carbon Observations (TANSO) Fourier transform spectrometer (FTS). TANSO-FTS uses three short-wave infrared (SWIR) bands to retrieve total columns of CO2 and CH4 along its optical line of sight and one thermal infrared (TIR) channel to retrieve vertical profiles of CO2 and CH4 volume mixing ratios (VMRs) in the troposphere. We examine version 1 of the TANSO-FTS TIR CH4 product by comparing co-located CH4 VMR vertical profiles from two other remote-sensing FTS systems: the Canadian Space Agency's Atmospheric Chemistry Experiment FTS (ACE-FTS) on SCISAT (version 3.5) and the European Space Agency's Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat (ESA ML2PP version 6 and IMK-IAA reduced-resolution version V5R_CH4_224/225), as well as 16 ground stations with the Network for the Detection of Atmospheric Composition Change (NDACC). This work follows an initial inter-comparison study over the Arctic, which incorporated a ground-based FTS at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Canada, and focuses on tropospheric and lower-stratospheric measurements made at middle and tropical latitudes between 2009 and 2013 (mid-2012 for MIPAS). For comparison, vertical profiles from all instruments are interpolated onto a common pressure grid, and smoothing is applied to ACE-FTS, MIPAS, and NDACC vertical profiles. Smoothing is needed to account for differences between the vertical resolution of each instrument and differences in the dependence on a priori profiles. The smoothing operators use the TANSO-FTS a priori and averaging kernels in all cases. We present zonally averaged mean CH4 differences between each instrument and TANSO-FTS with and without smoothing, and we examine their information content, their sensitive altitude range, their correlation, their a priori dependence, and the variability within each data set. Partial columns are calculated from the VMR vertical profiles, and their correlations are examined. We find that the TANSO-FTS vertical profiles agree with the ACE-FTS and both MIPAS retrievals' vertical profiles within 4 % (± ∼ 40 ppbv) below 15 km when smoothing is applied to the profiles from instruments with finer vertical resolution but that the relative differences can increase to on the order of 25 % when no smoothing is applied. Computed partial columns are tightly correlated for each pair of data sets. We investigate whether the difference between TANSO-FTS and other CH4 VMR data products varies with latitude. Our study reveals a small dependence of around 0.1 % per 10 degrees latitude, with smaller differences over the tropics and greater differences towards the poles.

Rate-based modeling and sensitivity analysis of a packed column for post-combustion CO2 capture into a novel reactive 1-dimethylamino-2-propanol (1DMA2P) solution

This study presents the rate-based modeling for CO2 absorption into a novel amine solution, 1DMA2P, in a column packed with random packing. The rate-based model has been developed on the basis of five key elements: the heat and mass transfer balances, thermodynamic model, estimation of physicochemical properties, enhancement factor model, and calculations of column internal hydraulic. The heat and mass transfer balances were derived based on the two-film theory by taking a differential element from a packed column. The Deshmukh–Mather model as thermodynamic framework was incorporated in the rate-based model to calculate the CO2 loading of 1DMA2P solution. The physicochemical properties such as amine density, amine viscosity, amine surface tension, amine heat capacity, and diffusivity of the CO2 in amine solution were predicted based on the thermodynamic correlations developed in this study. The rate-based model was numerically solved and validated by using experimental data of the CO2 concentration along the height of a packed column. In addition, we have performed the sensitivity analysis on the profiles of CO2 and H2O and profiles of gas and liquid temperature by applying four different mass transfer correlations of the random packing. Also, the effects of different operating parameters were investigated on the CO2 mole fraction profiles in gas phase. The rate-based model predicted the experimental data of CO2 concentration along the height of a packed column with an AARD% of 2.18. The sensitivity analysis showed that Onda’s correlations provided good results in comparison with other analyzed correlations.