scholarly journals GFIT2: an experimental algorithm for vertical profile retrieval from near-IR spectra

2016 ◽  
Vol 9 (8) ◽  
pp. 3513-3525 ◽  
Author(s):  
Brian J. Connor ◽  
Vanessa Sherlock ◽  
Geoff Toon ◽  
Debra Wunch ◽  
Paul O. Wennberg
Keyword(s):  
Spectral Band ◽  
Total Carbon ◽  
Vertical Profiles ◽  
Satellite Measurements ◽  
Ongoing Research ◽  
Near Ir ◽  
Synthetic Spectra ◽  
Experimental Algorithm ◽  
Scientific Value ◽  
Co2 Profile

Abstract. An algorithm for retrieval of vertical profiles from ground-based spectra in the near IR is described and tested. Known as GFIT2, the algorithm is primarily intended for CO2, and is used exclusively for CO2 in this paper. Retrieval of CO2 vertical profiles from ground-based spectra is theoretically possible, would be very beneficial for carbon cycle studies and the validation of satellite measurements, and has been the focus of much research in recent years. GFIT2 is tested by application both to synthetic spectra and to measurements at two Total Carbon Column Observing Network (TCCON) sites. We demonstrate that there are approximately 3° of freedom for the CO2 profile, and the algorithm performs as expected on synthetic spectra. We show that the accuracy of retrievals of CO2 from measurements in the 1.61μ (6220 cm−1) spectral band is limited by small uncertainties in calculation of the atmospheric spectrum. We investigate several techniques to minimize the effect of these uncertainties in calculation of the spectrum. These techniques are somewhat effective but to date have not been demonstrated to produce CO2 profile retrievals with sufficient precision for applications to carbon dynamics. We finish by discussing ongoing research which may allow CO2 profile retrievals with sufficient accuracy to significantly improve the scientific value of the measurements from that achieved with column retrievals.

scholarly journals GFIT2: an experimental algorithm for vertical profile retrieval from near IR spectra

2015 ◽  
Vol 8 (11) ◽  
pp. 12263-12295 ◽  
Author(s):  
B. J. Connor ◽  
V. Sherlock ◽  
G. Toon ◽  
D. Wunch ◽  
P. Wennberg
Keyword(s):  
Vertical Profile ◽  
Spectral Band ◽  
Sufficient Accuracy ◽  
Vertical Profiles ◽  
Satellite Measurements ◽  
Near Ir ◽  
Synthetic Spectra ◽  
Experimental Algorithm ◽  
Co2 Profile ◽  
Total Column

Abstract. An algorithm for retrieval of vertical profiles from ground-based spectra in the near IR is described and tested. Known as GFIT2, the algorithm is primarily intended for CO2, and is used exclusively for CO2 in this paper. Retrieval of CO2 vertical profiles from ground-based spectra is theoretically possible, would be very beneficial for carbon cycle studies and the validation of satellite measurements, and has been the focus of much research in recent years. GFIT2 is tested by application both to synthetic spectra, and to measurements at two TCCON sites. We demonstrate that there are approximately 3° of freedom for the CO2 profile, and the algorithm performs as expected on synthetic spectra. We show that the accuracy of retrievals of CO2 from measurements in the 1.6 μ spectral band is limited by small uncertainties in calculation of the atmospheric spectrum. We investigate several techniques to minimize the effect of these uncertainties in calculation of the spectrum. These techniques are somewhat effective, but to date have not been demonstrated to produce CO2 profile retrievals superior to existing techniques for retrieval of column abundance. We finish by discussing on-going research which may allow CO2 profile retrievals with sufficient accuracy to significantly improve on the results of column retrievals, both in total column abundance and in profile shape.

scholarly journals Quantifying lower tropospheric methane concentrations using GOSAT near-IR and TES thermal IR measurements

2015 ◽  
Vol 8 (8) ◽  
pp. 3433-3445 ◽  
Author(s):  
J. R. Worden ◽  
A. J. Turner ◽  
A. Bloom ◽  
S. S. Kulawik ◽  
J. Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
Surface Fluxes ◽  
Vertical Profiles ◽  
Monthly Average ◽  
Near Ir ◽  
Surface Measurements ◽  
Increased Sensitivity ◽  
The Impact ◽  
Total Column ◽  
Methane Concentrations

Abstract. Evaluating surface fluxes of CH4 using total column data requires models to accurately account for the transport and chemistry of methane in the free troposphere and stratosphere, thus reducing sensitivity to the underlying fluxes. Vertical profiles of methane have increased sensitivity to surface fluxes because lower tropospheric methane is more sensitive to surface fluxes than a total column, and quantifying free-tropospheric CH4 concentrations helps to evaluate the impact of transport and chemistry uncertainties on estimated surface fluxes. Here we demonstrate the potential for estimating lower tropospheric CH4 concentrations through the combination of free-tropospheric methane measurements from the Aura Tropospheric Emission Spectrometer (TES) and XCH4 (dry-mole air fraction of methane) from the Greenhouse gases Observing SATellite – Thermal And Near-infrared for carbon Observation (GOSAT TANSO, herein GOSAT for brevity). The calculated precision of these estimates ranges from 10 to 30 ppb for a monthly average on a 4° × 5° latitude/longitude grid making these data suitable for evaluating lower-tropospheric methane concentrations. Smoothing error is approximately 10 ppb or less. Comparisons between these data and the GEOS-Chem model demonstrate that these lower-tropospheric CH4 estimates can resolve enhanced concentrations over flux regions that are challenging to resolve with total column measurements. We also use the GEOS-Chem model and surface measurements in background regions across a range of latitudes to determine that these lower-tropospheric estimates are biased low by approximately 65 ppb, with an accuracy of approximately 6 ppb (after removal of the bias) and an actual precision of approximately 30 ppb. This 6 ppb accuracy is consistent with the accuracy of TES and GOSAT methane retrievals.

scholarly journals Technical Note: Feasibility of CO<sub>2</sub> profile retrieval from limb viewing solar occultation made by the ACE-FTS instrument

2009 ◽  
Vol 9 (8) ◽  
pp. 2873-2890 ◽  
Author(s):  
P. Y. Foucher ◽  
A. Chédin ◽  
G. Dufour ◽  
V. Capelle ◽  
C. D. Boone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Transport ◽  
A Priori ◽  
Accurate Determination ◽  
Technical Note ◽  
High Spectral Resolution ◽  
Vertical Profiles ◽  
Vertical Resolution ◽  
Solar Occultation ◽  
Co2 Profile

Abstract. Major limitations of our present knowledge of the global distribution of CO2 in the atmosphere are the uncertainty in atmospheric transport mixing and the sparseness of in situ concentration measurements. Limb viewing space-borne sounders, observing the atmosphere along tangential optical paths, offer a vertical resolution of a few kilometers for profiles, which is much better than currently flying or planned nadir sounding instruments can achieve. In this paper, we analyse the feasibility of obtaining CO2 vertical profiles in the 5–25 km altitude range from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS, launched in August 2003), high spectral resolution solar occultation measurements. Two main difficulties must be overcome: (i) the accurate determination of the instrument pointing parameters (tangent heights) and pressure/temperature profiles independently from an a priori CO2 profile, and (ii) the potential impact of uncertainties in the temperature knowledge on the retrieved CO2 profile. The first difficulty has been solved using the N2 collision-induced continuum absorption near 4 μm to determine tangent heights, pressure and temperature from the ACE-FTS spectra. The second difficulty has been solved by a careful selection of CO2 spectral micro-windows. Retrievals using synthetic spectra made under realistic simulation conditions show a vertical resolution close to 2.5 km and accuracy of the order of 2 ppm after averaging over 25 profiles. These results open the way to promising studies of transport mechanisms and carbon fluxes from the ACE-FTS measurements. First CO2 vertical profiles retrieved from real ACE-FTS occultations shown in this paper confirm the robustness of the method and applicability to real measurements.

scholarly journals Spectral Sizing of a Coarse Spectral Resolution Satellite Sensor for XCO<sub>2</sub>

2019 ◽  
Author(s):  
Jonas Simon Wilzewski ◽  
Anke Roiger ◽  
Johan Strandgren ◽  
Jochen Landgraf ◽  
Dietrich G. Feist ◽  
...  
Keyword(s):  
Light Scattering ◽  
Spectral Resolution ◽  
Spectral Band ◽  
Ground Truth ◽  
Resolving Power ◽  
Total Carbon ◽  
Band Selection ◽  
Co2 Absorption ◽  
Absorption Bands ◽  
Satellite Sensor

Abstract. Verifying anthropogenic carbon dioxide (CO2) emissions globally is essential to inform about the progress of institutional efforts to mitigate man-made climate forcing. To monitor localized emission sources, spectroscopic satellite sensors have been proposed that operate on the CO2 absorption bands in the shortwave-infrared (SWIR) spectral range with ground resolution as fine as a few tens to about a hundred meters. When designing such sensors, fine ground resolution requires a trade-off towards coarse spectral resolution in order to achieve sufficient noise performance. Since fine ground resolution also implies limited ground coverage, such sensors are envisioned to fly in fleets of satellites, requiring low-cost and simple design, e.g. by restricting the spectrometer to a single spectral band. Here, we use measurements of the Greenhouse Gases Observing Satellite (GOSAT) to evaluate the spectral resolution and spectral band selection of a prospective satellite sensor with fine ground resolution. To this end, we degrade GOSAT SWIR spectra of the CO2 bands at 1.6 (SWIR-1) and 2.0 μm (SWIR-2) to coarse spectral resolution, and we evaluate retrievals of the column-averaged dry-air mole-fractions of CO2 (XCO2) by comparison to ground-truth provided by the Total Carbon Column Observing Network (TCCON) and by comparison to global native GOSAT retrievals with native spectral resolution and spectral band selection. Coarsening spectral resolution from GOSAT's native resolving power of > 20,000 to the range of 700 to a few thousand makes the scatter of differences between the SWIR-1 and SWIR-2 retrievals and TCCON increase moderately. For resolving powers of 1,600 (SWIR-1) and 1,200 (SWIR-2), the scatter increases from 2.4 ppm (native) to 3.0 ppm for SWIR-1 and 3.3 ppm for SWIR-2. Coarser spectral resolution yields only marginally worse performance than the native GOSAT configuration in terms of station-to-station variability and geophysical parameter correlations for the TCCON-GOSAT differences. Comparing the SWIR-1 and SWIR-2 configurations to native GOSAT retrievals on the global scale, however, reveals that the coarse resolution SWIR-1 and SWIR-2 configurations suffer from some spurious correlations with geophysical parameters that characterize the light-scattering properties of the scene such as particle amount, size, height and surface albedo. Overall, the SWIR-1 and SWIR-2 configurations with resolving powers of 1,600 and 1,200 show promising performance for future sensor design in terms of random error sources while residual errors induced by light-scattering along the lightpath need to be investigated further. Due to the stronger CO2 absorption bands in SWIR-2 than in SWIR-1, the former has the advantage that measurement noise propagates less into the retrieved XCO2 and that some retrieval information on particle scattering properties is accessible.

scholarly journals A method for colocating satellite <i>X</i><sub>CO<sub>2</sub></sub> data to ground-based data and its application to ACOS-GOSAT and TCCON

2014 ◽  
Vol 7 (8) ◽  
pp. 2631-2644 ◽  
Author(s):  
H. Nguyen ◽  
G. Osterman ◽  
D. Wunch ◽  
C. O'Dell ◽  
L. Mandrake ◽  
...  
Keyword(s):  
Mean Squared Error ◽  
Weighted Average ◽  
Satellite Observations ◽  
Total Carbon ◽  
Satellite Measurements ◽  
Temporal Window ◽  
Squared Error ◽  
Scanning Imaging ◽  
Total Column ◽  
Absorption Spectrometer

Abstract. Satellite measurements are often compared with higher-precision ground-based measurements as part of validation efforts. The satellite soundings are rarely perfectly coincident in space and time with the ground-based measurements, so a colocation methodology is needed to aggregate "nearby" soundings into what the instrument would have seen at the location and time of interest. We are particularly interested in validation efforts for satellite-retrieved total column carbon dioxide (XCO2), where XCO2 data from Greenhouse Gas Observing Satellite (GOSAT) retrievals (ACOS, NIES, RemoteC, PPDF, etc.) or SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) are often colocated and compared to ground-based column XCO2 measurement from Total Carbon Column Observing Network (TCCON). Current colocation methodologies for comparing satellite measurements of total column dry-air mole fractions of CO2 (XCO2) with ground-based measurements typically involve locating and averaging the satellite measurements within a latitudinal, longitudinal, and temporal window. We examine a geostatistical colocation methodology that takes a weighted average of satellite observations depending on the "distance" of each observation from a ground-based location of interest. The "distance" function that we use is a modified Euclidian distance with respect to latitude, longitude, time, and midtropospheric temperature at 700 hPa. We apply this methodology to XCO2 retrieved from GOSAT spectra by the ACOS team, cross-validate the results to TCCON XCO2 ground-based data, and present some comparisons between our methodology and standard existing colocation methods showing that, in general, geostatistical colocation produces smaller mean-squared error.

scholarly journals Numerical Experiments to Analyze Cloud Microphysical Processes Depicted in Vertical Profiles of Radar Reflectivity of Warm Clouds

2015 ◽  
Vol 72 (12) ◽  
pp. 4509-4528 ◽  
Author(s):  
Naomi Kuba ◽  
Kentaroh Suzuki ◽  
Tempei Hashino ◽  
Tatsuya Seiki ◽  
Masaki Satoh
Keyword(s):  
Collection Efficiency ◽  
Radar Reflectivity ◽  
Efficient Production ◽  
Vertical Profiles ◽  
Satellite Measurements ◽  
Cloud Optical Depth ◽  
Surface Precipitation ◽  
Slope Factor ◽  
Microphysical Processes ◽  
Bin Method

Abstract Information about microphysical processes in warm clouds embedded in satellite measurements must be untangled to be used to improve the parameterization in global models. In this paper, the relationship between vertical profiles of horizontally averaged radar reflectivity Zm and cloud optical depth from cloud top τd was investigated using a hybrid cloud microphysical model and a forward simulator of satellite measurements. The particle size distributions were explicitly simulated using a bin method in a kinematic framework. In contrast to previous interpretations of satellite-observed data, three patterns of the Zm–τd relationship related to microphysical processes were identified. The first is related to the autoconversion process, which causes Zm to increase upward with decreasing τd. Before the initiation of surface precipitation, Zm increases downward with τd in the upper part of the cloud, which is considered to be a second characteristic pattern and is caused by the accretion process. The appearance of this pattern corresponds to the initiation of efficient production of raindrops in the cloud. The third is related to the sedimentation and evaporation of raindrops causing Zm to decrease downward with τd in the lower part of the Zm–τd relationship. It was also found that the bulk collection efficiency has a partially positive correlation with the slope factor of Zm with regard to τd and that the slope factor could be a gross measure of the collection efficiency in partial cases. This study also shows that differences in the aerosol concentration modulate the duration of these three patterns and change the slope factor of Zm.

scholarly journals Radiative forcing by volcanic eruptions since 1990, calculated with a chemistry-climate model and a new emission inventory based on vertically resolved satellite measurements

2021 ◽  
Author(s):  
Jennifer Schallock ◽  
Christoph Brühl ◽  
Christine Bingen ◽  
Michael Höpfner ◽  
Landon Rieger ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Emission Inventory ◽  
Climate Model ◽  
Aerosol Particles ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Radiation Budget ◽  
Vertical Profiles ◽  
Satellite Measurements ◽  
Model Simulations

Abstract. This paper presents model simulations of stratospheric aerosols with a focus on explosive volcanic eruptions. Using various (occulation and limb based) satellite instruments, with vertical profiles of sulfur dioxide (SO2) from the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) instrument and vertical profiles of aerosol extinction from GOMOS (Global Ozone Monitoring by Occultation of Stars), OSIRIS (Optical Spectrograph and InfraRed Imaging System), and SAGE II (Stratospheric Aerosol and Gas Experiment), we characterised the influence of volcanic aerosols for the period between 1990 and 2019. We established a volcanic sulfur emission inventory that includes more than 500 eruptions. The identified SO2 perturbations were incorporated as three-dimensional pollution plumes into a chemistry-climate model, which converts the gases into aerosol particles and computes their optical properties. The Aerosol Optical Depth (AOD) and the climate radiative forcing are calculated online. Combined with model improvements, the simulations reproduce the observations of the various satellites. Slight deviations between the observations and model simulations were found only for the large volcanic eruption of Pinatubo in 1991. This is likely due to either an overestimation of the removal of aerosol particles in the model, or limitations of the satellite measurements, which are related to saturation effects associated with anomalously high aerosol concentrations. Since Pinatubo, only smaller-sized volcanic eruptions have taken place. Weak- and medium-strength volcanic eruptions captured in satellite data and the Smithsonian database typically inject about 10 kt to 50 kt SO2 directly into the upper troposphere/lower stratosphere (UTLS) region or transport it indirectly via convection and advection. Our results show that these relatively smaller eruptions, which occur quite frequently, can nevertheless contribute significantly to the stratospheric aerosol layer and are relevant for the Earth's radiation budget. These eruptions are found to cause a global radiative forcing in the order of −0.1 Wm−2 at the tropopause.

scholarly journals Influence of aerosols and thin cirrus clouds on the GOSAT-observed CO<sub>2</sub>: a case study over Tsukuba

2011 ◽  
Vol 11 (11) ◽  
pp. 29883-29914 ◽  
Author(s):  
O. Uchino ◽  
N. Kikuchi ◽  
T. Sakai ◽  
I. Morino ◽  
Y. Yoshida ◽  
...  
Keyword(s):  
Near Infrared ◽  
Cirrus Clouds ◽  
Total Carbon ◽  
Observation Data ◽  
Vertical Profiles ◽  
Lidar System ◽  
Infrared Band ◽  
The Difference ◽  
Lidar Observations

Abstract. Lidar observations of vertical profiles of aerosols and thin cirrus clouds were made at Tsukuba (36.1° N, 140.1° E), Japan, to investigate the influence of aerosols and thin cirrus clouds on the column-averaged dry-air mole fraction of carbon dioxide (XCO2) retrieved from observation data of the Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer, measured in the Short-Wavelength InfraRed band (TANSO-FTS SWIR), onboard the Greenhouse gases Observing SATellite (GOSAT). The lidar system measured the backscattering ratio, depolarization ratio, and/or the wavelength exponent of atmospheric particles. The lidar observations and ground-based high-resolution FTS measurements at the Tsukuba Total Carbon Column Observing Network (Tsukuba TCCON) site were recorded simultaneously during passages of GOSAT over Tsukuba. GOSAT SWIR XCO2 data (version 01.xx) released in August 2010 were compared with the lidar and Tsukuba TCCON data. High-altitude aerosols and thin cirrus clouds had a large impact on the GOSAT SWIR XCO2 results. By taking into account the observed aerosol/cirrus vertical profiles and using a more adequate solar irradiance database in the GOSAT SWIR retrieval, the difference between the GOSAT SWIR XCO2 data and the Tsukuba TCCON data was greatly reduced.

scholarly journals Impact of eutrophication and climate change on Cd and other trace metal dynamic in the Gulf of Riga, Baltic Sea

2014 ◽  
Vol 68 (1-2) ◽  
pp. 112-117
Author(s):  
Juris Aigars ◽  
Rita Poikāne ◽  
Iveta Jurgensone ◽  
Mintauts Jansons
Keyword(s):  
Water Column ◽  
Marine Ecosystem ◽  
Total Carbon ◽  
Vertical Profiles ◽  
Element Ratio ◽  
Column Studies ◽  
Positive Correlation ◽  
Sedimentary Records ◽  
Gulf Of Riga ◽  
Over Time

Abstract The ability of Cd and other trace metals to be incorporated in living phytoplankton cells has been widely used to explain its dynamic in marine ecosystem. However, the discrepancy between results from water column studies and those from studies in sediments remain unexplained. This strongly suggests a need for study with a more interconnected approach in identification of the main governing factors of trace element dynamics. Therefore, we conducted this study, which linked sedimentary records of trace elements with particular emphasis on Cd with available supporting information from sediments and water column. The concentrations of Cu, Mn, Cd and Cr in sediments of the Gulf of Riga exhibited significant (P < 0.01) positive relationships, while concentrations of Al and Ni had significant (P < 0.01 and P < 0.05, respectively) negative correlation with concentrations of TC. Concentrations of Zn, Pb and Fe in sediments did not exhibit significant correlation with concentrations of total carbon (TC). The vertical profiles of concentrations of several elements indicated that their accumulation patterns in sediments have changed substantially over time in respect to that of TC. The magnitude of change varied substantially from retaining positive correlation but changing element ratio value, in case of Cd, to complete shift from positive correlation to negative, in case of Zn and Cu.

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