Sensitivity of on-line wavelength during retrieval of atmospheric CO2 vertical profile

Accurately measuring the differential molecular absorption cross section is the key to obtaining a high-precision concentration of atmospheric trace gases in a differential absorption lidar（DIAL） system. However, the CO2 absorption line is meticulous at 1.6 μm, easily translating and broadening because of the change of temperature and pressure. Hence, measuring the vertical profile of atmospheric temperature and pressure to calculate the vertical profile of the CO2 weight parameter is necessary. In general, measuring atmospheric temperature and pressure has a certain amount of uncertainty. Therefore, this study proposes the concept of a balanced on-line wavelength,where the differential molecular absorption cross section is larger and the CO2 weight parameter is insensitive to the uncertainty of atmospheric temperature and pressure. In this study, we analyzed the influence of uncertainty on the CO2 weight parameter at every preselected wavelength, as well as determined an appropriate wavelength near one of the absorption peaks. Our result shows that 1572.023 nm should be one of the appropriate balanced online wavelengths. The measurement errors of the mixing ratio of CO2 molecule in this wavelength are only 0.23%and 0.25% and are caused by 1 K temperature error and 1h Pa pressure error, respectively. This achievement of a balanced on-line wavelength will not only depress the requirement of the laser’s frequency stabilization but also the demand for measurement precision of the atmospheric temperature and pressure profile. Furthermore, this study can achieve the exact measurement of the vertical profile of atmospheric CO2 based on an independent differential absorption laser.

Using a Tree Ring δ^(13)C Annual Series to Reconstruct Atmospheric CO_2 Concentration over the Past 300 Years

The annual series of δ13C were measured in tree rings of three Cryptomeria fortunei disks （OF-1, OF-2, and OF- 3） collected from West Tianmu Mountain, Zhejiang Province, China, according to cross-dating tree ring ages. There was no obvious decreasing trend of the δ13C annual time series of CF-2 before 1835. However, from 1835 to 1982 the three tree ring δ13C annual series exhibited similar decreasing trends that were significantly （P ≤ 0.001） correlated. The distribution characteristics of a scatter diagram between estimated δ13C series of CF-2 from modeling and the atmospheric CO2 concentration extracted from the Law Dome ice core from 1840 to 1978 were analyzed and a curvilinear regression equation for reconstructing atmospheric CO2 concentration was established with R2 = 0.98. Also, a test of independent samples indicated that between 1685 and 1839 the reconstructed atmospheric CO2 concentration .using the δ13C series of CF-2 had a close relationship with the Law Dome and Siple ice cores, with a standard deviation of 1.98. The general increasing trend of the reconstructed atmospheric CO2 concentration closely reflected the 10ng-term variation of atmospheric CO2 concentration recorded both before and after the Industrial Revolution. Between 1685 and 1840 the evaluated atmospheric CO2 concentration was stable, but after 1840 it exhibited a rapid increase. Given a longer δ13C annual time series of tree rings, it was feasible to rebuild a representative time series to describe the atmospheric CO2 concentration for an earlier period and for years that were not in the ice core record.

The Buffer Capability of the Ocean to Increasing Atmospheric CO_2

The CO_2-seawater system and the method for calculating the partial pressure of CO2 (pCO2) in seawater are studied. The buffer capability of the ocean to increasing atmospheric CO2 is expressed in terms of the differential buffer factor and buffer index. Dissolutions of aragonite and calcite have a significant inffluence on the differential buffer factor. The trend of change in the buffer factor is obtained by a box model.

Capability of Raman lidar for monitoring the variation of atmospheric CO_2 profile

Lidar （Light detection and ranging） has special capabilities for remote sensing of many different behaviours of the atmosphere. One of the techniques which show a great deal of promise for several applications is Raman scattering. The detecting capability, including maximum operation range and minimum detectable gas concentration is one of the most significant parameters for lidar remote sensing of pollutants. In this paper, based on the new method for evaluating the capabilities of a Raman lidar system, we present an evaluation of detecting capability of Raman lidar for monitoring atmospheric CO2 in Hefei. Numerical simulations about the influence of atmospheric conditions on lidar detecting capability were carried out, and a conclusion can be drawn that the maximum difference of the operation ranges caused by the weather conditions alone can reach about 0.4 to 0.5km with a measuring precision within 30ppmv. The range of minimum detectable concentration caused by the weather conditions alone can reach about 20 to 35 ppmv in vertical direction for 20000 shots at a distance of 1 km on the assumption that other parameters are kept constant. The other corresponding parameters under different conditions are also given. The capability of Raman lidar operated in vertical direction was found to be superior to that operated in horizontal direction. During practical measurement with the Raman lidar whose hardware components were fixed, aerosol scattering extinction effect would be a significant factor that influenced the capability of Raman lidar. This work may be a valuable reference for lidar system designing, measurement accuracy improving and data processing.

Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile

Lidar （Light detection and ranging） system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and ＇real-time＇ Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.

Spatial heterodyne spectroscopy for space-based measurements of atmospheric CO_2

To reduce the error from measurement and retrieval process, a new technology of spatial heterodyne spectroscopy is proposed. The principle of this technology and the instrument spatial het- erodyne spectrometer （SHS） are introduced. The first application of this technology will be for CO2 measurements from space on a high spectral observation satellite. The outstanding measurement principle and the priority of combination of retrieval algorithm and three channels （ O2 A-band, CO2 1.58 μm and 2.06 μm bands） are theoretically analyzed and numerically simulated. Experiments u- sing SHS prototype with low spectral resolution of 0. 4 cm -1are carried out for preliminary valida- tion. The measurements show clear CO2 absorption lines and follow the expected signature with the- ory spectrum, and the retrievals agreed well with GOSAT CO2 products, except a small bias of about 4 × 10 ^-6. The results show that the ability of spatial heterodyne spectroscopy for CO2 detecting is ob- vious, and SHS is a competent sensor.

Dynamic Responses of Atmospheric Carbon Dioxide Concentration to Global Temperature Changes between 1850 and 2010

Changes in Earth＇s temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a tem- perature sensitivity parameter （1.64 ppm yr-1 ℃-1） into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide （CO2） concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010 （r2 〉 0.96 and the root-mean-square error 〈 1 ppm for the period from 1960 onward）. Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir （-12 year） approximates the long-term temperature sensitivity of global atmospheric CO2 concentration （-15 ppm ℃ 1）, generally consistent with previous estimates based on reconstructed CO2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmo- spheric CO2 concentration and slowed the net rate of atmospheric CO2 sequestration by global land and oceans by -30% since the 1960s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.

Atmospheric CO_2 retrieval with a look-up-table based method by combining near and thermal infrared spectra

In order to precisely retrieve the atmospheric CO2 , a retrieval method based on both near infrared （NIR） and thermal infrared （TIR） is established firstly. Then a look-up-table （LUT） based fast line-by-line radiative transfer model （RTM） was integrated into the retrieval procedure to accelerate radiative transfer calculations. The LUT stores gas absorption cross-sections as a function of temperature, pressure and wavenumber. It could greatly reduce calculating time in radiative transfer compared to direct line-by-line method. Then retrieval was simulated using NIR, TIR and both bands. The retrieved CO2 profiles suggest joint approach could reconstruct CO2 profile better than those using NIR or TIR alone. Joint retrieval using both bands simultaneously could provide better constrain to CO2 vertical distribution in the whole troposphere.

Effect of Ocean Thermal Diffusivity on Global Warming Induced by Increasing Atmospheric CO_2

A global mean ocean model including atmospheric heating, heat capacity of the mixed layer ocean, and vertical thermal diffusivity in the lower ocean, proposed by Cess and Goldenberg (1981), is used in this paper to study the sensitivity of global warming to the vertical diffusivity. The results suggest that the behaviour of upper ocean temperature is mainly determined by the magnitude of upper layer diffusivity and an ocean with a larger diffusivity leads to a less increase of sea surface temperature and a longer time delay for the global warming induced by increasing CO2 than that with smaller one. The global warming relative to four scenarios of CO2 emission assumed by Intergovernmental Panel of Climate Change (IPCC) is also estimated by using the model with two kinds of thermal diffusivities. The result shows that for various combinations of the CO2 emission scenarios and the diffusivities, the oceanic time delay to the global warming varies from 15 years to 70 years.

Real-data assimilation experiment with a joint data assimilation system: assimilating carbon dioxide mole fraction measurements from the Greenhouse gases Observing Satellite

The performance of a joint data assimilation system（Tan-Tracker）,which is based on the PODEn4 Dvar assimilation method,in assimilating Greenhouse gases Observing SATellite（GOSAT） carbon dioxide（CO2） data,was evaluated.Atmospheric 3D CO2 concentrations and CO2 surface fluxes（CFs） from2010 were simulated using a global chemistry transport model（GEOS-Chem）.TheTan-Tracker system used the simulated CO2 concentrations and fluxes as a background field and assimilated the GOSAT column average dry-air mole fraction of CO2（X（CO2）） data to optimize CO2 concentrations and CFs in the same assimilation window.Monthly simulated X（CO2）（X（CO2）Sim）） and assimilated X（CO2）（X（CO2）,TT） data retrieved at different satellite scan positions were compared with GOSAT-observed X（CO2）（X（CO2）,obs）data.The average RMSE between the monthly X（CO2）,TT and X（CO2）,Obs data was significantly（30%） lower than the average RMSE between X（CO2）,Sim and X（CO2）,Obs）.Specifically,reductions in error were found for the positions of northern Africa（the Sahara）,the Indian peninsula,southern Africa,southern North America,and western Australia.The difference between the correlation coefficients of the X（CO2）,Sim）and X（CO2）,Obs and those of the X（CO2）Π）,TT and X（CO2）,Obs was only small.In general,the Tan-Tracker system performed very well after assimilating the GOSAT data.

Impact of animal manure addition on the weathering of agricultural lime in acidic soils＂ The agent of carbonate weathering

Fertilization and aglime(agricultural lime) application, as important agricultural activities in acid soil, exert an influence on the fluxes of carbon both between and within ecosystems. Animal manure added to soil can elevate the soil CO_2 and release organic acid due to microbial decomposition of the high organic matter content of animal manure. Additionally, the elevated CO_2 can accelerate carbonate weathering in alkaline soil, such as lime soil. However, in acidic soil, it is unclear whether the chemical weathering of additive aglime can be quickened by the elevated CO_2 due to animal manure addition. Thus, to ascertain the impact of animal manure addition on aglime weathering in acidic soil and to understand the weathering agent of aglime or underlying carbonate in the acidic soil profile, we established two contrasting profiles(control profile and manurial profile) in a cabbage-corn or capsicum-corn rotation in a field experiment site located in the Hua Xi district of Guiyang, China, and buried carbonate rock tablets at different depths of soil profiles to calculate the dissolution rate of carbonate rock by monitoring the weights of the tablets. The results indicated that soil CO_2 increased due to animal manure addition, but the rate of dissolution of the carbonate rock tablets was reduced, which was attributed to the increase in the p H in acidic soil after animal manure addition because the relationship between the dissolution rate of carbonate rock and soil p H indicated that the weathering rate of carbonate rock was controlled by pH and not by CO_2 in acidic soil. Thus, the contribution of H+ ions(mainly exchangeable acid) in acid soil as a weathering agent to the weathering of underlying carbonate(and/or aglime) may lead to the overestimation of the CO_2 consumption through chemical weathering at the regional/global scale using hydro-chemical methods.

Effect of Carbon Dioxide (CO_2) Controlled Atmosphere on Superoxide Dismutase (SOD) Activity of Three Storage Pests in Chinese Medicinal Materials

[ Objective ] The paper was to study the effect of controlled atmosphere stress of carbon dioxide （ CO2 ） on Superoxide dismutase （SOD） activity of in- sect, so as to analyze the biological mechanism of the action of controlled atmosphere stress on insect. [ Method] Using nitrotetrazolium blue chloride （NBT） light reduction method, SOD activity of drugstore beetle （ Stegobium panlceum ）, cigarette beetle （ Lasioderma serricorne） and coffee bean beetle （Araecerus fasciculatus） was studied, and the stress response of the enzyme under controlled atmosphere stress of CO2 was analyzed. [ Result ] SOD activity of drugstore beetle, cigarette beetle and coffee bean beetle exposed to controlled atmosphere stress of high concentrations of CO2 for 3 and 6 h had certain degree of increase, and the activity sig- nificantly increased from 2.011±0.954,2.664±0.218 and 1.458±0.718 to 3. 135±0. 105,3.050±0.673 and 2.975±0.229 U/（per pest · 30 min） after treat- ment for 6 h. [ Conclusion] Controlled atmosphere stress of high concentrations of CO2 had certain activation effect on SOD activity of storage pest in Chinese me- dicinal material within the context of sub-lethal events. The results could enrich the insecticidal mechanism of controlled atmosphere and theoretical system of analy- sis on insect resistance to controlled atmosphere.

Photosynthetic Responses to Inorganic Carbon in Ulva lactuca Under Aquatic and Aerial States

Intertidal macroalgae experience continual alternation of photosynthesis between aquatic state at high tide and aerial state at low tide. The comparative photosynthetic responses to inorganic carbon were investigated in the common intertidal macroalga Ulva lactuca L. along the coast of Shantou between aquatic and aerial state. The inorganic carbon dissolved in seawater at present could fully (at 10 ℃ or 20 ℃) or nearly (at 30 ℃) saturate the aquatic photosynthesis of U. lactuca . However, the aerial photosynthesis was limited by current ambient atmospheric CO 2 level, and such a limitation was more severe at higher temperature (20-30 ℃) than at lower temperature (10 ℃). The carbon_saturated maximal photosynthesis of U. lactuca under aerial state was much greater than that under aquatic state at 10 ℃ and 20 ℃, while the maximal photosynthesis under both states was similar at 30 ℃. The aerial values of K m (CO 2) for photosynthesis were higher than the aquatic values. On the contrary, the values of apparent photosynthetic CO 2 conductance under aerial state were considerably lower than that under aquatic state. It was concluded that the increase of atmospheric CO 2 would enhance the primary productivity of U. lactuca through stimulating the photosynthesis under aerial state during low tide.

The Soil Moisture and Net Primary Production Affected by CO_2 and Climate Change Using a Coupled Model

In this paper, a coupled model was used to estimate the responses of soil moisture and net primary production of vegetation(NPP) to increasing atmospheric CO2 concentration and climate change. The analysis uses three experiments simulated by the second-generation Earth System Model(CanESM2) of the Canadian Centre for Climate Modelling and Analysis(CCCma), which are part of the phase 5 of the Coupled Model Intercomparison Project(CMIP5). The authors focus on the magnitude and evolution of responses in soil moisture and NPP using simulations modeled by CanESM, in which the individual effects of increasing CO2 concentration and climate change and their combined effect are separately accounted for. When considering only the single effect of climate change, the soil moisture and NPP have a linear trend of 0.03 kg m–2 yr–1 and –0.14 gC m–2 yr–2, respectively. However, such a reduction in the global NPP results from the decrease of NPP at lower latitudes and in the Southern Hemisphere, although increased NPP has been shown in high northern latitudes. The largest negative trend is located in the Amazon basin at –1.79 gC m–2 yr–2. For the individual effect of increasing CO2 concentration, both soil moisture and NPP show increases, with an elevated linear trend of 0.02 kg m–2 yr–1 and 0.84 gC m–2 yr–2, respectively. Most regions show an increasing NPP, except Alaska. For the combined effect of increasing atmospheric CO2 and climate change, the increased soil moisture and NPP exhibit a linear trend of 0.04 kg m–2 yr–1 and 0.83 gC m–2 yr–2 at a global scale. In the Amazon basin, the higher reduction in soil moisture is illustrated by the model, with a linear trend of –0.39 kg m–2 yr–1, for the combined effect. Such a change in soil moisture is caused by a weakened Walker circulation simulated by this coupled model, compared with the single effect of increasing CO2 concentration(experiment M2), and a consequence of the reduction in NPP is also shown in this area, with a linear trend of-0.16 gC m-2 yr-2.

The Observed Low CO_2 Concentration in the Rongbuk Valley on the Northern Slope of Mt. Everest

In the summers of 2006 and 2007, the atmospheric CO2 concentration and the wind speed in the Rongbuk Valley on the northern slope of Mr. Everest were measured by an ultrasonic anemometer with an Li-7500 CO2/H2O gas analyzer. The average CO2 concentration was 370.23±0.59 and 367.45±1.91 ppm in June of 2006 and 2007, respectively. The values are much lower than those at sites with similar latitudes and altitudes worldwide. The observed atmospheric CO2 concentration in Rongbuk Valley can be affected by the transportation of prevailing down-valley winds from the up-valley direction to the observation site. Our results suggest that the Mt. Everest region could be ideal for background atmospheric and environmental studies.

A comparison of atmospheric CO_2 concentration GOSAT-based observations and model simulations

Satellite observations of atmospheric CO2 are able to truly capture the variation of global and regional CO2 concentration.The model simulations based on atmospheric transport models can also assess variations of atmospheric CO2 concentrations in a continuous space and time,which is one of approaches for qualitatively and quantitatively studying the atmospheric transport mechanism and spatio-temporal variation of atmospheric CO2 in a global scale.Satellite observations and model simulations of CO2 offer us two different approaches to understand the atmospheric CO2.However,the difference between them has not been comprehensively compared and assessed for revealing the global and regional features of atmospheric CO2.In this study,we compared and assessed the spatio-temporal variation of atmospheric CO2 using two datasets of the column-averaged dry air mole fractions of atmospheric CO2(XCO2)in a year from June 2009 to May 2010,respectively from GOSAT retrievals(V02.xx)and from Goddard Earth Observing System-Chemistry(GEOS-Chem),which is a global 3-D chemistry transport model.In addition to the global comparison,we further compared and analyzed the difference of CO2 between the China land region and the United States(US)land region from two datasets,and demonstrated the reasonability and uncertainty of satellite observations and model simulations.The results show that the XCO2 retrieved from GOSAT is globally lower than GEOS-Chem model simulation by 2 ppm on average,which is close to the validation conclusion for GOSAT by ground measures.This difference of XCO2 between the two datasets,however,changes with the different regions.In China land region,the difference is large,from 0.6 to 5.6 ppm,whereas it is 1.6 to 3.7 ppm in the global land region and 1.4 to 2.7 ppm in the US land region.The goodness of fit test between the two datasets is 0.81 in the US land region,which is higher than that in the global land region(0.67)and China land region(0.68).The analysis results further indicate that the inconsistency of CO2concentration between satellite observations and model simulations in China is larger than that in the US and the globe.This inconsistency is related to the GOSAT retrieval error of CO2 caused by the interference among input parameters of satellite retrieval algorithm,and the uncertainty of driving parameters in GEOS-Chem model.

Influence of HITRAN Database Updates on Retrievals of Atmospheric CO_2 from Near-Infrared Spectra

The line-transition parameters of the High Resolution Transmission （HITRAN） 2008 database have been updated relative to previous editions. The transmission spectra and sensitivity to changes in CO2 concentrations using line parameters from the HITRAN 2004 and HITRAN 2008 databases are compared to evaluate the effect of the database updates on retrievals of carbon dioxide vertical columns from nearinfrared reflected sunlight. This comparison is done in three spectral regions covering the 2.06-, 1.61-, and 1.58-μm CO2 bands used by the Greenhouse Gases Observatory Satellite （GOSAT） instrument and the planned successor to the Orbiting Carbon Observatory （OCO）. The updates to the HITRAN database have the largest effects on the transmittance and the off-line to on-line transmittance ratio in the 2.06-μm region and the smallest effects on these parameters in the 1.58-μm region. The influence of the updates to the HITRAN database on the off-line to on-line ratio calculation in the narrow spectral region 4855-4880 cm^-1 could be equivalent to a change in CO2 of more than 50 ppmv. Use of the HITRAN 2004 database will lead to an underestimate of the column CO2 abundance in the 2.06- and 1.61-pro spectral regions, whereas it will lead to an overestimate of the column CO2 abundance in the 1.58-μm spectral region.

A nonautonomous mat hematical model to assess the impact of algae on the abatement of atmospheric carbon dioxide

The world's oceans have played an important role in sequestering atmospheric carbon dioxide through solubility and the action of algae.Fixation of atmospheric carbon dioxide by photoautotrophic algal cultures has the potential to diminish the release of carbon dioxide into the atmosphere,thereby helping to alleviate the trend toward global warming.This work investigates the role of algae in controlling the level of atmospheric carbon dioxide.Partial Rank Correlation Coefficients(PRCCs)technique is used to address how the concentration of atmospheric carbon dioxide is affected by changes in a specific parameter disregarding the uncertainty over the rest of the model parameters.Parameters related to algal growth are shown to significantly reduce the level of atmospheric CO_(2).Further,we explore the dynamics of nonautonomous system by incorporating the seasonal variations of sonic ecologically important model parameters.Our nonautonomous system exhibits globally attractive positive periodic solution,and also the appearance of double periodic solution is observed.Moreover,by letting the seasonally forced parameters as almost periodic functions of time,we show almost periodic behavior of the system.Our findings suggest that the policy makers should focus on continuous addition of nutrients in the ocean to accelerate the algal growth thereby reducing the level of carbon dioxide in the atmosphere.

Cooperative effect from cation and anion of pyridine-containing anion-based ionic liquids for catalysing CO_2 transformation at ambient conditions

Pyridine-containing anion-based ionic liquids(PA-ILs) with two kinds of interaction sites to bind CO_2, e.g., [P4444][2-OP], were found to be highly efficient for catalysing the cycloaddition reactions of atmospheric CO_2 with epoxides at room temperature under metal-and halogen-free conditions, producing a series of cyclic carbonates in high yields. It was demonstrated that the cooperative interaction from two interaction sites in the anions of PA-ILs activated CO_2, while the cation activated the epoxides substrates via coordination to the central P+ unit, thus resulting in the high activity of the IL catalysts.