Effect of HITRAN Database Improvement on Retrievals of Atmospheric Carbon Dioxide from Reflected Sunlight Spectra in the 1.61-μm Spectral Window

A large number of experimental and theoretical investigations of carbon dioxide (CO2) spectra have been conducted since the most recent update of the High-Resolution Transmission Molecular Absorption (...     

Calculation of solar and thermal radiation absorption in the atmosphere, based on the HITRAN data

Summary Using the HITRAN database from 2003, the absorption of solar and thermal radiation by the atmosphere is calculated. The results are presented in the form of spectral densities of absorption yield of the atmosphere and its components, and fractions of absorbed energy of the solar radiation and thermal radiation in the atmosphere by each of its components separately and together. Finally, the obtained results are discussed in the context of the lately published model of Earth’s radiation budget-MAP 85(4), 275–281 (2004). The shares of atmospheric components in the greenhouse effect and in the absorption of solar radiation are calculated. The percentage contributions of the more important atmospheric components in the greenhouse effect are as follows: clouds 66, water vapor 25, CO₂ 6.7, N₂O 0.7, CH₄ 0.7.     

Optimization of the OCO-2 Cloud Screening Algorithm and Evaluation against MODIS and TCCON Measurements over Land Surfaces in Europe and Japan

A method to tighten the cloud screening thresholds based on local conditions is used to provide more stringent schemes for Orbiting Carbon Observatory-2(OCO-2) cloud screening algorithms. Cloud screening strategies are essential to remove scenes with significant cloud and/or aerosol contamination from OCO-2 observations, which helps to save on the data processing cost and ensure high quality retrievals of the column-averaged CO₂ dry air mole fraction(XCO₂). Based on the rad...     

Biogenic and anthropogenic organic matter in aerosol over continental Europe: source characterization in the east Baltic region

An Aerodyne quadruple aerosol mass spectrometer (Q-AMS) has been used to provide on-line measurements of size dependent chemical composition of fine aerosol particles (PM₁) at the Air Pollution Research Station in Preila, Lithuania, representing the east Baltic region. The size dependent chemical composition measurements by AMS have revealed that in marine air masses 118?nm mode organics-containing particles were fresher compared to sulfate-containing particles (295?nm), likely originated as secondary aerosol from forest emissions or produced by primary sea spray over the Baltic Sea. In polluted continental air masses sulfate and organics were highly internally mixed and aged. The mass spectral results indicated that the major components of organic compounds were oxygenated organic species with strong signals at m/z 18, 43, 44 with several specific features. Positive matrix factorization (PMF) of AMS organic mass spectral data has identified three factors: aged oxygenated low-volatility organic aerosol (LV-OOA), less oxygenated semi-volatile organic aerosol (SV-OOA), and biogenic organic aerosol (BGOA) of either terrestrial or marine origin. The measurements were compared with a real-time particulate matter Beta Absorption Monitor (Thermo ESM Andersen) and Micro Orifice Uniform Deposit Impactor (MOUDI) data. The intercomparison showed a good correlation and a stable ratio between PM₁ and PM_2.5 concentrations. A comparison of the on-line Q-AMS data and the off-line MOUDI fine particle (<1???m) data yielded a reasonable agreement in size distributions but not the absolute mass concentrations due to sampling conditions, evaporation of acidic species from sampling substrates and bounce of the particles in the MOUDI.     

The influence of negative emission technologies and technology policies on the optimal climate mitigation portfolio

Combining policies to remove carbon dioxide (CO₂) from the atmosphere with policies to reduce emissions could decrease CO₂ concentrations faster than possible via natural processes. We model the optimal selection of a dynamic portfolio of abatement, research and development (R&D), and negative emission policies under an exogenous CO₂ constraint and with stochastic technological change. We find that near-term abatement is not sensitive to the availability of R&D policies, but the anticipated availability of negative emission strategies can reduce the near-term abatement optimally undertaken to meet 2°C temperature limits. Further, planning to deploy negative emission technologies shifts optimal R&D funding from ??carbon-free?? technologies into ??emission intensity?? technologies. Making negative emission strategies available enables an 80% reduction in the cost of keeping year 2100 CO₂ concentrations near their current level. However, negative emission strategies are less important if the possibility of tipping points rules out using late-century net negative emissions to temporarily overshoot the CO₂ constraint earlier in the century.     

Molecular Line Parameters for the “MASTER” (Millimeter Wave Acquisitions for Stratosphere/Troposphere Exchange Research) Database

In order to investigate the upper troposphere/lower stratosphere (UTLS) region of the earth's atmosphere, ESA/ESTEC (European space agency) is considering the opportunity to develop the spaceborne limb sounding millimeter sensor “MASTER” (millimeter wave acquisitions for stratosphere/troposphere exchange research). This instrument is part of the “atmospheric composition explorer for chemistry and climate interactions” (ACECHEM) project. In addition, ESA/ESTEC is developing the “MARSCHALS” (millimeter-wave airborne receiver for spectroscopic characterization of atmospheric limb sounding) airborne instrument which will demonstrate the feasibility of MASTER. The present paper describes the line-by-line database which was generated in order to meet at best the needs of the MASTER (or MARSCHALS) instrument. The linelist involves line positions, line intensities, line broadening and line shift parameters in the 294–305, 316–325, 342–348, 497–506 and 624–626 GHz spectral microwindows. This database was first generated for the target molecules for MASTER (H₂O, O₃, N₂O, CO, O₂, HNO₃, HCl, ClO, CH₃Cl, BrO). In addition, ten additional molecules (SO₂, NO₂, OCS, H₂CO, HOCl, HCN, H₂O₂, COF₂, HO₂ and HOBr) had also to be considered in the database as “possible interfering species” for the retrieval of the target molecules of MASTER. The line parameters were derived, depending on their estimated accuracy, (i) from a combination of spectral parameters included in the JPL and HITRAN catalogs (ii) from data taken into the literature or (iii) using data obtained through experimental measurements (and/or) calculations performed during the present study.     

锡林浩特草原CO2通量特征及其影响因素分析

利用锡林浩特国家气候观象台开路涡度相关系统、辐射土壤观测系统,测得的长期连续通量观测数据,对锡林浩特草原2009—2011年期间的CO₂通量观测特征进行了分析。结果表明:CO₂通量存在明显的年际、季节和日变化特征。3 a中NEE年际变率达到200 g·m^-2,季节变率最大达到460 g·m^-2,日变化幅度生长季最大达到0.25 mg·m^-2·s^-1。通过不同时间尺度碳通量与温度、水分、辐射等环境因子的分析,认为CO₂通量日变化主要受温度和光合有效辐射影响,而季节变化和年变化主要受降水和土壤含水量的影响。降水强度及时间分布是制约牧草CO₂吸收的关键因素,大于15%的土壤含水量有利于促进牧草生长。     

Methane emissions from a landfill measured by eddy correlation using a fast response diode laser sensor

We describe a fast response methane sensor based on the absorption of radiation generated with a near-infrared InGaAsP diode laser. The sensor uses an open path absorption region 0.5 m long; multiple pass optics provide an optical path of 50 m. High frequency wavelength modulation methods give stable signals with detection sensitivity (S/N=1, 1 Hz bandwidth) for methane of 65 ppb at atmospheric pressure and room temperature. Improvements in the optical stability are expected to lower the current detection limit. We used the new sensor to measure, by eddy correlation, the CH₄ flux from a clay-capped sanitary landfill. Simultaneously we measured the flux of CO₂ and H₂O. From seven half-hourly periods of data collected after a rainstorm on November 23, 1991, the average flux of CH₄ was 17 mmol m^–2 hr^–1 (6400 mg CH₄ m^–2 d^–1) with a coefficient of variation of 25%. This measurement may underrepresent the flux by 15% due to roll-off of the sensor response at high frequency. The landfill was also a source of CO₂ with an average flux of 8.1 mmol m^–2 hr^–1 (8550 mg CO₂ m^–2 d^–1) and a coefficient of variation of 26%. A spectral analysis of the data collected from the CH₄, CO₂, and H₂O sensors showed a strong similarity in the turbulent transfer mechanisms.     

The Effects of Different HITRAN Versions on Calculated Long-Wave Radiation and Uncertainty Evaluation

Four editions of the High Resolution Transmission (HITRAN) databases (HITRAN96, HITRAN2K, HITRAN04, and HITRAN08) are compared by using a line-by-line (LBL) radiative model in the long-wave calculation for six typical atmospheres. The results show that differences in downward radiative fluxes between HITRAN96 and HITRAN08 at the surface can reach a maximum of 1.70 W m 2 for tropical atmospheres. The largest difference in heating rate between HITRAN96 and HITRAN08 can reach 0.1 K day 1 for midlatitude summer atmosphere. Uncertainties caused by line intensity and air-broadened halfwidths are also evaluated in this work using the uncertainty codes given in HITRAN08. The uncertainty is found to be 1.92 W m 2 for upward fluxes at the top of the atmosphere (TOA) and 1.97 W m 2 for downward fluxes at the surface. The largest heating rate caused by the uncertainty of line intensity and air-broadened half-width can reach 0.5 K day 1 . The differences in optical depths between 1300 and 1700 cm 1 caused by different HITRAN versions are larger than those caused by the uncertainties in intensity and air-broadened half-width. This paper suggests that there is inaccurate representation of line parameters over some spectral ranges in HITRAN and more attention should be paid to these ranges in fields such as remote sensing.     

北京城区二氧化碳时空分布及湍流谱特征

利用北京325 m气象塔上安装的7层CO₂涡动相关系统在2014年12月到2015年11月的观测资料,分析了北京城区不同高度上CO₂浓度、通量时空分布及湍流谱的特征。结果表明:城市CO₂浓度日变化除了冬季都呈现双峰型,冬季由于人为碳源排放的大幅增加,双峰型不明显。每层的CO₂浓度、通量都有明显的季节变化:冬季最高,春末、夏季最低。CO₂浓度整体随高度的增加而降低。北京城区是CO₂源,CO₂通量的日变化不如CO₂浓度日变化规律明显。CO₂通量在47 m以下为负,47 m以上为正。通量在140 m以下随高度的增加而增加;140m以上随高度的增加而减少。根据对CO₂时空分布的分析可知:边界层CO₂浓度、通量强烈受到碳源、下垫面植被、大气稳定度、环境温度和天气过程等因素的影响。各变量谱与Kaimal等的研究结果接近:归一化速度谱和CO₂谱在惯性子区有－2/3的斜率,在低频区与稳定度参数（Z/L）有一定的关系。这说明复杂地形的城市下垫面的湍流谱结构与平坦地形相比没有太大的实质性差异。     

On tropospheric adjustment to forcing and climate feedbacks

Motivated by findings that major components of so-called cloud ??feedbacks?? are best understood as rapid responses to CO₂ forcing (Gregory and Webb in J Clim 21:58?C71, 2008), the top of atmosphere (TOA) radiative effects from forcing, and the subsequent responses to global surface temperature changes from all ??atmospheric feedbacks?? (water vapour, lapse rate, surface albedo, ??surface temperature?? and cloud) are examined in detail in a General Circulation Model. Two approaches are used: applying regressions to experiments as they approach equilibrium, and equilibrium experiments forced separately by CO₂ and patterned sea surface temperature perturbations alone. Results are analysed using the partial radiative perturbation (??PRP??) technique. In common with Gregory and Webb (J Clim 21:58?C71, 2008) a strong positive addition to ??forcing?? is found in the short wave (SW) from clouds. There is little evidence, however, of significant global scale rapid responses from long wave (LW) cloud, nor from surface albedo, SW water vapour or ??surface temperature??. These responses may be well understood to first order as classical ??feedbacks????i.e. as a function of global mean temperature alone and linearly related to it. Linear regression provides some evidence of a small rapid negative response in the LW from water vapour, related largely to decreased relative humidity (RH), but the response here, too, is dwarfed by subsequent response to warming. The large rapid SW cloud response is related to cloud fraction changes??and not optical properties??resulting from small cloud decreases ranging from the tropical mid troposphere to the mid latitude lower troposphere, in turn associated with decreased lower tropospheric RH. These regions correspond with levels of enhanced heating rates and increased temperatures from the CO₂ increase. The pattern of SW cloud fraction response to SST changes differs quite markedly to this, with large positive radiation responses originating in the upper troposphere, positive contributions in the lowest levels and patterns of positive/negative contributions in mid latitude low levels. Overall SW cloud feedback was diagnosed as negative, due to the substantial negative SW feedback in cloud optical properties more than offsetting these. This study therefore suggests the rapid response to CO₂ forcing is (apart from a possible small negative response from LW water vapour) essentially confined to cloud fraction changes affecting SW radiation, and further that significant feedbacks with temperature occur in all cloud components (including this one), and indeed in all other classically understood ??feedbacks??.     

Quantification of ecosystem carbon exchange characteristics in a dominant subtropical evergreen forest ecosystem

CO₂ fluxes were measured continuously for three years (2003?C2005) using the eddy covariance technique for the canopy layer with a height of 27 m above the ground in a dominant subtropical evergreen forest in Dinghushan, South China. By applying gapfilling methods, we quantified the different components of the carbon fluxes (net ecosystem exchange (NEE)), gross primary production (GPP) and ecosystem respiration (R_eco) in order to assess the effects of meteorological variables on these fluxes and the atmospherecanopy interactions on the forest carbon cycle. Our results showed that monthly average daily maximum net CO₂ exchange of the whole ecosystem varied from ?3.79 to ?14.24 ??mol m^?2 s^?1 and was linearly related to photosynthetic active radiation. The Dinghushan forest acted as a net carbon sink of ?488 g C m^?2 y^?1, with a GPP of 1448 g Cm^?2 y^?1, and a R_eco of 961 g C m^?2 y^?1. Using a carboxylase-based model, we compared the predicted fluxes of CO₂ with measurements. GPP was modelled as 1443 g C m^?2 y^?1, and the model inversion results helped to explain ca. 90% of temporal variability of the measured ecosystem fluxes. Contribution of CO₂ fluxes in the subtropical forest in the dry season (October-March) was 62.2% of the annual total from the whole forest ecosystem. On average, 43.3% of the net annual carbon sink occurred between October and December, indicating that this time period is an important stage for uptake of CO₂ by the forest ecosystem from the atmosphere. Carbon uptake in the evergreen forest ecosystem is an indicator of the interaction of between the atmosphere and the canopy, especially in terms of driving climate factors such as temperature and rainfall events. We found that the Dinghushan evergreen forest is acting as a carbon sink almost year-round. The study can improve the evaluation of the net carbon uptake of tropical monsoon evergreen forest ecosystem in south China region under climate change conditions.     

Carbon dioxide,water vapor and sensible heat exchanges of a grain sorghum canopy

With the aid of eddy correlation instrumentation, the components of the energy budget and CO₂ flux were measured over grain sorghum grown at Mead, Nebraska. Diurnal patterns of sensible heat, latent heat, CO₂ and momentum flux are examined for typical days. On a mostly clear day when the crop leaf area index was 3.7, net radiation reached a mid-day peak of 560 W m^-2, while sensible and latent heat fluxes peaked at 50 and 460 W m^-2, respectively. The peak CO₂ flux occurring just prior to solar noon was 1.5 mg m^-2(ground area) s^-1. CO₂ flux (respiration from plants, soil and roots) in the early evening was about -0.28 mg m^-2 (ground area) s^-1.A relationship between CO₂ flux and photosynthetically active radiation (PAR) was developed. Except during the late stage of growth (growth stage 8.5, toward the initiation of senescence), the crop showed no evidence of saturation up to PAR 1800 Ei m^-2s^-1. The light compensation point was found to be about 211 Ei m^-2s^-1. Examination of CO₂ flux-PAR relationships for selected days through the season indicated an aging effect in terms of a decrease in photosynthetic activity of the sorghum canopy. Measurements made on two consecutive days demonstrate the effects of weather conditions on CO₂ flux and carbon-water flux ratio (a measure of water use efficiency of the crop). The occurrence of regional sensible heat advection with concommitant high vapor pressure deficit and air temperature-limited CO₂ exchange reduced the carbon-water flux ratio.Published as Paper No. 7717, Journal Series, Nebraska Agricultural Research Division. The work was conducted under Regional Research Project 11-33 and Nebraska Agricultural Research Division Project 27-003.Formerly Post Doctoral Research Associate (now at the University of Connecticut Department of Renewable Natural Resources Storrs CT)     

Daytime boundary layer behavior over eastern region (per-humid climate) and western regions (semi-arid climate) of India: a case study

The annual variation in planetary boundary layer (PBL) height is determined from the profiles of conserved thermodynamic variables, i.e., virtual potential temperature ?? _v and equivalent potential temperature ?? _e, using radiosonde data at per-humid climate region, Ranchi (23°42??N, 85°33??E, 610?m asl) and semi-arid region, Anand (23°35??N, 72°55??E, 45.1?m asl), India. Of all the variables, the ?? _v profile seems to provide the most reasonable estimate of the PBL height. This has been supplemented by T-Phi gram analysis for specific days. It has been found that in winter the height of boundary layer is very low due to subsidence and radiational cooling, while pre-monsoon months exhibit the most variable convection. It may be inferred that synoptic conditions accompanied by a variety of weather phenomena such as thunderstorms, onset and withdrawal of monsoons, etc. control the ABL over Ranchi, while daytime solar insolation and nighttime radiative cooling mainly control the ABL over Anand.     

山西省城市大气CO2本底筛分对比及特征分析

基于典型城市站太原站2018年3月—2019年2月的大气CO₂在线观测资料,利用筛分法(Meteorological filtering method, MET)和黑碳示踪法(Black Carbon tracer, BC)进行本底/非本底的筛分,得到了本底浓度的变化特征。结果表明,太原大气CO₂浓度季均值冬季最高,夏季最低;不同季节呈“单峰型”日变化特征,日振幅均在26.0×10^-6以上;4个季节CO₂浓度与地面风速存在显著负相关关系;CO₂浓度抬升区域主要受当地工业布局的影响,最大抬升幅度在秋季达17.4×10^-6;使用气象筛分法(MET)得到年均本底浓度为(431.4±19.9)×10^-6,人为排放等对其影响为23.5×10^-6,年振幅比同纬度其它本底站大,为34.5×10^-6;黑碳示踪法(BC)得到冬季季均本底浓度为(445.0±22.9)×10^-6,比MET筛...     

Effects of climate change and elevated atmospheric CO2 on soil organic carbon: a response equation

Climate change, such as warming and precipitation change, as well as elevated CO₂ can affect soil organic carbon (SOC) dynamics and cause changes in soil carbon sequestration. In this study, we introduced a response equation, relating the relative change of SOC to the relative changes of annual average temperature, annual precipitation, and atmospheric CO₂ concentration, as well as their inter-products. Using Nelson Farm as a case study, based on simulations of CENTURY model and multiple regressions, we examined the response equation for three vegetation covers (i.e., soybean, corn, and grass) and scenarios with different soil erosion rates and initial SOC contents. The response equation fit the simulation results very well with high adjusted coefficients of determination (R ²) (0.982 to 0.990). The results showed that the SOC was negatively related to the annual average temperature, positively related to the annual precipitation, and positively related to the elevated CO₂ for all the vegetation covers (p?<?0.001). The SOC was also significantly impacted by the interaction effects between elevated CO₂ and warming or precipitation change (p?<?0.001). The general form of the response equations for the different vegetation covers, soil erosion rates, and initial SOC contents was the same although the parameters varied with the different conditions. Based on the response equation, ??cutoff surfaces?? were defined to clearly quantify the synthesis effects of any possible combination of climate change and elevated CO₂ on the SOC, and the SOC sequestration potential was assessed under climate change and elevated CO₂ for different vegetations. Compared with the empirical models in the literature, this response equation provides a simple yet but robust method to represent the relationship between the SOC relative change vs. the relative changes of atmospheric temperature, precipitation, and atmospheric CO₂ concentration.     

Interannual Variability of Atmospheric CO<Subscript>2</Subscript> Concentrations over Central Siberia from ZOTTO Data for 2009–2015

The interannual variations in the characteristics of the seasonal cycle (annual and seasonal amplitudes, winter emission, dates of annual minimum and maximum, and phase) and in the growth rate of atmospheric carbon dioxide concentration over Central Siberia are analyzed for the period from May 2009 to January 2016. The results are based on the continuous monitoring of CO₂ concentration at the Zotino Tall Tower Observatory (ZOTTO, www.zottoproject.org). It is found that the seasonal amplitude of CO₂ concentration in the atmo spheric surface layer over Western Siberia is 26.4 ± 0.8 μmol/mol (no long-term trend toward its increase was revealed), the annual mean growth rate of CO₂ is 2.34 μmol/mol per year, its variations range from 1 to 4 μmol/mol per year.     

硫酸盐气溶胶直接辐射效应在线与离线模拟方法的比较

利用区域气候模式RegCM 2与大气化学模式连接的模拟系统 ,比较了硫酸盐气溶胶辐射强迫的在线、离线模拟方法的硫酸盐柱含量、大气顶直接辐射强迫及地表温度响应。发现 :在线与离线模拟方法得到的硫酸盐柱含量、有无反馈大气顶直接辐射强迫和地表温度响应在许多地区有很大差异 ,这种差异在较小区域平均的尺度上更显著 ,在全区域平均尺度上也较为明显 ,是不能被忽略的 ;结果显示从硫酸盐含量到辐射强迫和地表温度响应逐渐加大的差异 ,说明硫酸盐气溶胶的辐射强迫与模拟方法有关 ,显示出较大的不确定性。     

Atmospheric CO2 variations at Barrow,Alaska, 1973–1982

The first 10 years (1973–1982) of atmospheric CO₂ measurements at Barrow, Alaska, by the NOAA/GMCC program are described. The paper updates and extends the Barrow CO₂ record presented in Tellus (1982). The data are given in final form, based on recent calibrations of the Scripps Institution of Oceanography, with selected values identified as representative of large, spacescale conditions. Analyses of the data show: (1) a long-term CO₂ average increase of 1.3 ppm per year, but with large year-to-year variations in that growth rate; (2) a suggestion, not statistically significant, of a secular increase in the amplitude of the annual cycle, presumably a reflection of global-scale biospheric variability; and (3) good absolute agreement between the Barrow results and those from four neighboring high latitude sites between 50 and 82°N.     

Why Is the Climate Forcing of Sulfate Aerosols So Uncertain?

l. IntroductionAlthough the aerosol has been recognized as an important factor which has innuence onthe past, present and future climate for a long time, it still has much uncertainty in assessingits climate forcing. The direct radiative forcing of sulfate aerosols has been estimated rangingfrom --0.3 W/ m2 to --0.9 W/ m2 in recent publications (Charlson et al., l992, Kiehl andBriegleb l993; Taylor and Penner 1994, Boucher and Anderson l995, Kieh1 and Rodhe l995;Chuang et al., l997, Penne…