An important component of any CO_2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties,such as velocity and density.Different reservoirs have different amplitude variatio...An important component of any CO_2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties,such as velocity and density.Different reservoirs have different amplitude variation with offset(AVO) responses,which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile(VSP) AVO response to CO_2 injection at the Ketzin site,the first European onshore CO_2 sequestration pilot study dealing with research on geological storage of CO_2.First,we performed rock physics analysis to evaluate the effect of injected CO_2 on seismic velocity using the Biot-Gassmann equation.On the basis of this model,the seismic response for different CO_2 injection saturation was studied using ray tracing modeling.We then created synthetic walkaway VSP data,which we then processed.In contrast,synthetic seismic traces were created from borehole data.Finally,we found that the amplitude of CO_2 injected sand layer with different gas saturations were increased with the offset when compared with the original brine target layer.This is the typical classⅢAVO anomaly for gas sand layer.The AVO responses matched the synthetic seismic traces very well.Therefore,walkaway VSP AVO response can monitor CO_2 distribution in the Ketzin area.展开更多
CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, A...CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, Apr. to Jul. of 2000, and from Aug. 2002 to Sept. 2003. Based on the collected dada, the diurnal and seasonal dynamics of profiles and storage of carbon dioxide in the forest were analyzed. The diurnal CO2 profiles showed that the vertical distribution of CO2 concentration were different for daytime and nighttime, and the CO2 concentration was highest close to forest floor, no matter at daytime and nighttime. The seasonal profiles of CO2 showed that stratification in the canopy was evident during growth season. CO2 concentrations at different heights (60 m to 2.5 m) had a little change in March, with a difference of 10 mmolmol-1, but had a significant change in July, with a difference of 60 mmolmol-1. In July, there also existed a greater gradient of CO2 concentrations at canopy (22, 26 and 32 m), with a difference of 8 mmolmol-1. The calculated total storage (ΔC/Δt ) of CO2 in the air column with height of 40 m beneath eddy covariance instrument was negative, and made a little contribution to NEE.展开更多
The vertical distribution of carbon dioxide(CO2)is important for the calibration and validation of transport models and remote sensing measurements.Due to the large mass and volume of traditional instruments as well a...The vertical distribution of carbon dioxide(CO2)is important for the calibration and validation of transport models and remote sensing measurements.Due to the large mass and volume of traditional instruments as well as supporting systems,in-situ measurements of the CO2 vertical profile within the boundary layer are rare.This study used a miniaturized CO2 monitoring instrument based on a low-cost non-dispersive infrared(NDIR)sensor to measure the CO2 vertical profile and meteorological parameters of the lower troposphere(0–1000 m)in southwestern Shijiazhuang,Hebei Province,China.The sensors were onboard a tethered balloon with two processes:the ascending process and the descending process.The results showed that the overall trend of CO2 concentration decreased with height.Weather conditions and CO2 emission sources caused fluctuations in CO2 concentrations.The CO2 concentration varied from morning to afternoon due mainly to the faster spread of air mass during daytime,with strong convections and the accumulation of emissions at night.The low-cost sensor produced results consistent with the traditional gas chromatography method.The Weather Research and Forecasting model could not capture the CO2 profiles well due mainly to the bad performances in boundary layer height and the potential outdated fossil fuel emissions around the experimental site.This experiment is the first successful attempt to observe the CO2 vertical distribution in the lower troposphere by using lowcost NDIR sensors.The results help us to understand the vertical structure of CO2 in the boundary layer,and provide data for calibrating and validating transport models.展开更多
Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical a...Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)technology is established for retrieving the tropospheric NO_(2) vertical distribution profiles.This method retrieves the aerosol extinction profiles with minimum cost function.Then,the aerosol extinction profiles and the atmospheric radiation transfer model(RTM)are employed to establish the look-up table for retrieving the NO_(2) vertical column densities(VCDs)and profiles.The measured NO_(2) differential slant column densities(DSCDs)are compared with the NO_(2) DSCDs simulated by the atmospheric RTM,and the NO_(2) VCDs,the weight factor of NO_(2) in the boundary layer,and the boundary layer height are obtained by the minimization process.The look-up table is established to retrieve NO_(2) VCDs based on MAX-DOAS measurements in Huaibei area,and the results are compared with the data from Copernicus Atmospheric Monitoring Service(CAMS)model.It is found that there are nearly consistent and the correlation coefficient R2 is more than 0.86.The results show that this technology provides a more convenient and accurate retrieval method for the stereoscopic monitoring of atmospheric environment.展开更多
An airborne multi-axis differential optical absorption spectroscopic （AMAX-DOAS） instrument was developed and applied to measure tropospheric NO2 in the Pearl River Delta region in the south of China. By combining t...An airborne multi-axis differential optical absorption spectroscopic （AMAX-DOAS） instrument was developed and applied to measure tropospheric NO2 in the Pearl River Delta region in the south of China. By combining the measurements in nadir and zenith directions and analyzing the UV and visible spectral region using the DOAS method, information about tropospheric NO2 vertical columns was obtained. Strong tropospheric NO2 signals were detected when flying over heavilly polluted regions and point sources like plants. The AMAX-DOAS results were compared with ground-based MAX-DOAS observations in the southwest of Zhuhai city using the same parameters for radiative transport calculations. The difference in vertical column data between the two instruments is about 8%. Our data were also compared with those from OMI and fair agreement was obtained with a correlation coefficient R of 0.61. The difference between the two instruments can be attributed to the different spatial resolution and the temporal mismatch during the measurements.展开更多
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, th...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.展开更多
We present a study on validation of the National Institute for Environmental Studies Transport Model(NIES TM)by comparing to observed vertical profiles of atmospheric CO_(2).The model uses a hybrid sigmaisentropic(σ...We present a study on validation of the National Institute for Environmental Studies Transport Model(NIES TM)by comparing to observed vertical profiles of atmospheric CO_(2).The model uses a hybrid sigmaisentropic(σ–θ)vertical coordinate that employs both terrain-following and isentropic parts switched smoothly in the stratosphere.The model transport is driven by reanalyzed meteorological fields and designed to simulate seasonal and diurnal cycles,synoptic variations,and spatial distributions of atmospheric chemical constituents in the troposphere.The model simulations were run for combination of biosphere,fossil fuel,air-ocean exchange,biomass burning and inverse correction fluxes of carbon dioxide(CO_(2))by GOSAT Level 4 product.We compared the NIES TM simulated fluxes with data from the HIAPER Pole-to-Pole Observations(HIPPO)Merged 10-s Meteorology,Atmospheric Chemistry,and Aerosol Data,including HIPPO-1,HIPPO-2 and HIPPO-3 from 128.0°E to 84.0°W,and 87.0°N to 67.2°S.The simulation results were compared with CO_(2) observations made in January and November,2009,and March and April,2010.The analysis attests that the model is sufficient to simulate vertical profiles with errors within 1–2 ppmv,except for the lower stratosphere in the northern hemisphere high latitudes.展开更多
The silicon vertical multi-junction （VMJ） solar cell has a good potential in high concentration, but it requires high quality front and back surface passivation layers to keep its high efficiency. We try to add dopa...The silicon vertical multi-junction （VMJ） solar cell has a good potential in high concentration, but it requires high quality front and back surface passivation layers to keep its high efficiency. We try to add dopants into the front and back surfaces of the VMJ cell to release this strict requirement in this work. The effects of recombination velocities, doping types and doping pro- files of front and back surfaces on the performance of the P-type VMJ cell were calculated under 1 sun and 1000 suns. The 2D numerical simulation tool TCAD software was used. The performance of the VMJ cell without front and back surface dopants was also calculated for comparison. It was found that the requirement of high quality front and back surface passivation layers could be released remarkably by adding either N-type or W-type front and back surface dopants. For the two types of front surface dopants, the highest efficiencies of the cells were got by light dopant; for the two types of back surface dopants, the doping type and profile affected little on the performance of the cell in our calculation range. It was also found that the series resistance of the VMJ cell with N-type front surface dopant was decreased by the 2D effect of front surface emitter. The VMJ cell with W-type front surface dopant had the highest efficiency under 1000 suns and the VMJ cell with N-type front surface dopant had the highest efficiency under 1 sun in our calculation range.展开更多
基金The European Commission,German Federal Ministry of Education and Research,German Federal Ministry of Economics and Technology as well as Research Institute and Industry are gratefully acknowledged for funding and supporting CO2 Storage by Injection into a Natural Storage Site CO2SINK(Project No.502599)
文摘An important component of any CO_2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties,such as velocity and density.Different reservoirs have different amplitude variation with offset(AVO) responses,which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile(VSP) AVO response to CO_2 injection at the Ketzin site,the first European onshore CO_2 sequestration pilot study dealing with research on geological storage of CO_2.First,we performed rock physics analysis to evaluate the effect of injected CO_2 on seismic velocity using the Biot-Gassmann equation.On the basis of this model,the seismic response for different CO_2 injection saturation was studied using ray tracing modeling.We then created synthetic walkaway VSP data,which we then processed.In contrast,synthetic seismic traces were created from borehole data.Finally,we found that the amplitude of CO_2 injected sand layer with different gas saturations were increased with the offset when compared with the original brine target layer.This is the typical classⅢAVO anomaly for gas sand layer.The AVO responses matched the synthetic seismic traces very well.Therefore,walkaway VSP AVO response can monitor CO_2 distribution in the Ketzin area.
基金This study is supported by The Development Plan of State Key Fundamental Research of China (973) (contract No. 2002CB412502),by Knowledge Innovation Project of CAS (KZCX1-SW-01-03) and by Natural Science Foundation of China (30170167).
文摘CO2 concentrations at different heights in a broadleaved/Korean forest (with a mean height of 26 m) were measured with infrared gas analyzer IRGA (model 2250D, LI-COR Inc. and LI-COR, 820) from Aug. to Oct. of 1999, Apr. to Jul. of 2000, and from Aug. 2002 to Sept. 2003. Based on the collected dada, the diurnal and seasonal dynamics of profiles and storage of carbon dioxide in the forest were analyzed. The diurnal CO2 profiles showed that the vertical distribution of CO2 concentration were different for daytime and nighttime, and the CO2 concentration was highest close to forest floor, no matter at daytime and nighttime. The seasonal profiles of CO2 showed that stratification in the canopy was evident during growth season. CO2 concentrations at different heights (60 m to 2.5 m) had a little change in March, with a difference of 10 mmolmol-1, but had a significant change in July, with a difference of 60 mmolmol-1. In July, there also existed a greater gradient of CO2 concentrations at canopy (22, 26 and 32 m), with a difference of 8 mmolmol-1. The calculated total storage (ΔC/Δt ) of CO2 in the air column with height of 40 m beneath eddy covariance instrument was negative, and made a little contribution to NEE.
基金This work was supported by the National Key R&D Program of China[grant number 2017YFB0504000]the National Natural Science Foundation of China[grant numbers 41705113 and 41877312].
文摘The vertical distribution of carbon dioxide(CO2)is important for the calibration and validation of transport models and remote sensing measurements.Due to the large mass and volume of traditional instruments as well as supporting systems,in-situ measurements of the CO2 vertical profile within the boundary layer are rare.This study used a miniaturized CO2 monitoring instrument based on a low-cost non-dispersive infrared(NDIR)sensor to measure the CO2 vertical profile and meteorological parameters of the lower troposphere(0–1000 m)in southwestern Shijiazhuang,Hebei Province,China.The sensors were onboard a tethered balloon with two processes:the ascending process and the descending process.The results showed that the overall trend of CO2 concentration decreased with height.Weather conditions and CO2 emission sources caused fluctuations in CO2 concentrations.The CO2 concentration varied from morning to afternoon due mainly to the faster spread of air mass during daytime,with strong convections and the accumulation of emissions at night.The low-cost sensor produced results consistent with the traditional gas chromatography method.The Weather Research and Forecasting model could not capture the CO2 profiles well due mainly to the bad performances in boundary layer height and the potential outdated fossil fuel emissions around the experimental site.This experiment is the first successful attempt to observe the CO2 vertical distribution in the lower troposphere by using lowcost NDIR sensors.The results help us to understand the vertical structure of CO2 in the boundary layer,and provide data for calibrating and validating transport models.
基金the National Natural Science Foundation of China(Grant No.41875040)the Top-notch Talents Program in Universities of Anhui Province,China(Grant No.gxbjZD2020067)the Natural Science Research Projects of Universities in Anhui Province,China(Grant No.KJ2020A0029).
文摘Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)technology is established for retrieving the tropospheric NO_(2) vertical distribution profiles.This method retrieves the aerosol extinction profiles with minimum cost function.Then,the aerosol extinction profiles and the atmospheric radiation transfer model(RTM)are employed to establish the look-up table for retrieving the NO_(2) vertical column densities(VCDs)and profiles.The measured NO_(2) differential slant column densities(DSCDs)are compared with the NO_(2) DSCDs simulated by the atmospheric RTM,and the NO_(2) VCDs,the weight factor of NO_(2) in the boundary layer,and the boundary layer height are obtained by the minimization process.The look-up table is established to retrieve NO_(2) VCDs based on MAX-DOAS measurements in Huaibei area,and the results are compared with the data from Copernicus Atmospheric Monitoring Service(CAMS)model.It is found that there are nearly consistent and the correlation coefficient R2 is more than 0.86.The results show that this technology provides a more convenient and accurate retrieval method for the stereoscopic monitoring of atmospheric environment.
基金supported by the National Natural Science Foundation of China(Grant Nos.41275037,41275038,and 41275027)
文摘An airborne multi-axis differential optical absorption spectroscopic （AMAX-DOAS） instrument was developed and applied to measure tropospheric NO2 in the Pearl River Delta region in the south of China. By combining the measurements in nadir and zenith directions and analyzing the UV and visible spectral region using the DOAS method, information about tropospheric NO2 vertical columns was obtained. Strong tropospheric NO2 signals were detected when flying over heavilly polluted regions and point sources like plants. The AMAX-DOAS results were compared with ground-based MAX-DOAS observations in the southwest of Zhuhai city using the same parameters for radiative transport calculations. The difference in vertical column data between the two instruments is about 8%. Our data were also compared with those from OMI and fair agreement was obtained with a correlation coefficient R of 0.61. The difference between the two instruments can be attributed to the different spatial resolution and the temporal mismatch during the measurements.
基金supported by the National Natural Science Foundation of China (Grant No. 41127901)the Program for Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1278)
文摘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.
基金supported by the National Basic Research Program of China(No.2010CB951603)supported by the High Performance Computer Center of East China Normal University.
文摘We present a study on validation of the National Institute for Environmental Studies Transport Model(NIES TM)by comparing to observed vertical profiles of atmospheric CO_(2).The model uses a hybrid sigmaisentropic(σ–θ)vertical coordinate that employs both terrain-following and isentropic parts switched smoothly in the stratosphere.The model transport is driven by reanalyzed meteorological fields and designed to simulate seasonal and diurnal cycles,synoptic variations,and spatial distributions of atmospheric chemical constituents in the troposphere.The model simulations were run for combination of biosphere,fossil fuel,air-ocean exchange,biomass burning and inverse correction fluxes of carbon dioxide(CO_(2))by GOSAT Level 4 product.We compared the NIES TM simulated fluxes with data from the HIAPER Pole-to-Pole Observations(HIPPO)Merged 10-s Meteorology,Atmospheric Chemistry,and Aerosol Data,including HIPPO-1,HIPPO-2 and HIPPO-3 from 128.0°E to 84.0°W,and 87.0°N to 67.2°S.The simulation results were compared with CO_(2) observations made in January and November,2009,and March and April,2010.The analysis attests that the model is sufficient to simulate vertical profiles with errors within 1–2 ppmv,except for the lower stratosphere in the northern hemisphere high latitudes.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275040,60976046,60837001,61021003)the National Basic Research Program of China("973" Project)(Grant No.2012CB934204)by Chinese Academy of Sciences(Grant No.Y072051002)
文摘The silicon vertical multi-junction （VMJ） solar cell has a good potential in high concentration, but it requires high quality front and back surface passivation layers to keep its high efficiency. We try to add dopants into the front and back surfaces of the VMJ cell to release this strict requirement in this work. The effects of recombination velocities, doping types and doping pro- files of front and back surfaces on the performance of the P-type VMJ cell were calculated under 1 sun and 1000 suns. The 2D numerical simulation tool TCAD software was used. The performance of the VMJ cell without front and back surface dopants was also calculated for comparison. It was found that the requirement of high quality front and back surface passivation layers could be released remarkably by adding either N-type or W-type front and back surface dopants. For the two types of front surface dopants, the highest efficiencies of the cells were got by light dopant; for the two types of back surface dopants, the doping type and profile affected little on the performance of the cell in our calculation range. It was also found that the series resistance of the VMJ cell with N-type front surface dopant was decreased by the 2D effect of front surface emitter. The VMJ cell with W-type front surface dopant had the highest efficiency under 1000 suns and the VMJ cell with N-type front surface dopant had the highest efficiency under 1 sun in our calculation range.
