scholarly journals Bias Correction of the Ratio of Total Column CH4 to CO2 Retrieved from GOSAT Spectra

2020 ◽  
Vol 12 (19) ◽  
pp. 3155
Author(s):  
Haruki Oshio ◽  
Yukio Yoshida ◽  
Tsuneo Matsunaga ◽  
Nicholas M. Deutscher ◽  
Manvendra Dubey ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Mole Fraction ◽  
Bias Correction ◽  
Lower Atmosphere ◽  
Total Carbon ◽  
Dry Air ◽  
Scattering Effects ◽  
The Mean ◽  
The Difference ◽  
Total Column

The proxy method, using the ratio of total column CH4 to CO2 to reduce the effects of common biases, has been used to retrieve column-averaged dry-air mole fraction of CH4 from satellite data. The present study characterizes the remaining scattering effects in the CH4/CO2 ratio component of the Greenhouse gases Observing SATellite (GOSAT) retrieval and uses them for bias correction. The variation of bias between the GOSAT and Total Carbon Column Observing Network (TCCON) ratio component with GOSAT data-derived variables was investigated. Then, it was revealed that the variability of the bias could be reduced by using four variables for the bias correction—namely, airmass, 2 μm band radiance normalized with its noise level, the ratio between the partial column-averaged dry-air mole fraction of CH4 for the lower atmosphere and that for the upper atmosphere, and the difference in surface albedo between the CH4 and CO2 bands. The ratio of partial column CH4 reduced the dependence of bias on the cloud fraction and the difference between hemispheres. In addition to the reduction of bias (from 0.43% to 0%), the precision (standard deviation of the difference between GOSAT and TCCON) was reduced from 0.61% to 0.55% by the correction. The bias and its temporal variation were reduced for each site: the mean and standard deviation of the mean bias for individual seasons were within 0.2% for most of the sites.

scholarly journals Comparisons of the Orbiting Carbon Observatory-2 (OCO-2) <i>X</i><sub>CO<sub>2</sub></sub> measurements with TCCON

2017 ◽  
Vol 10 (6) ◽  
pp. 2209-2238 ◽  
Author(s):  
Debra Wunch ◽  
Paul O. Wennberg ◽  
Gregory Osterman ◽  
Brendan Fisher ◽  
Bret Naylor ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Data Quality ◽  
Surface Properties ◽  
Mole Fraction ◽  
Bias Correction ◽  
Total Carbon ◽  
Retrieval Algorithm ◽  
Dry Air ◽  
Earth’S Atmosphere ◽  
Earth's Atmosphere

Abstract. NASA's Orbiting Carbon Observatory-2 (OCO-2) has been measuring carbon dioxide column-averaged dry-air mole fraction, XCO2, in the Earth's atmosphere for over 2 years. In this paper, we describe the comparisons between the first major release of the OCO-2 retrieval algorithm (B7r) and XCO2 from OCO-2's primary ground-based validation network: the Total Carbon Column Observing Network (TCCON). The OCO-2 XCO2 retrievals, after filtering and bias correction, agree well when aggregated around and coincident with TCCON data in nadir, glint, and target observation modes, with absolute median differences less than 0.4 ppm and RMS differences less than 1.5 ppm. After bias correction, residual biases remain. These biases appear to depend on latitude, surface properties, and scattering by aerosols. It is thus crucial to continue measurement comparisons with TCCON to monitor and evaluate the OCO-2 XCO2 data quality throughout its mission.

scholarly journals Carbon dioxide retrieval from OCO-2 satellite observations using the RemoTeC algorithm and validation with TCCON measurements

2018 ◽  
Author(s):  
Lianghai Wu ◽  
Otto Hasekamp ◽  
Haili Hu ◽  
Jochen Landgraf ◽  
Andre Butz ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Standard Deviation ◽  
Bias Correction ◽  
Satellite Observations ◽  
Total Carbon ◽  
A Posteriori ◽  
Gas Concentration ◽  
Dry Air ◽  
Spectral Bands ◽  
A Value

Abstract. In this study we present the retrieval of the column averaged dry air mole fraction of carbon dioxide (XCO2) from the Orbiting Carbon Observatory-2 (OCO-2) satellite observations using the RemoTeC algorithm, previously successfully applied to retrieval of greenhouse gas concentration from the Greenhouse Gases Observing Satellite (GOSAT). The XCO2 product has been validated with collocated ground based measurements from the Total Carbon Column Observing Network (TCCON) for almost 2 years of OCO-2 data from September 2014 to July 2016. We found that fitting an additive radiometric offset in all three spectral bands of OCO-2 significantly improved the retrieval. Based on a small correlation of the XCO2 error over land with fit residuals, we applied an a posteriori bias correction to our OCO-2 retrievals. In daily averaged results, XCO2 retrievals have a standard deviation ~ 1.30 ppm and a station-to-station variability of ~ 0.40 ppm among collocated TCCON sites. The seasonal relative accuracy (SRA) has a value of 0.52 ppm. The validation shows relatively larger difference with TCCON over high latitude areas and some specific regions like Japan.

scholarly journals Validation of methane and carbon monoxide from Sentinel-5 Precursor using TCCON and NDACC-IRWG stations

2021 ◽  
Vol 14 (9) ◽  
pp. 6249-6304
Author(s):  
Mahesh Kumar Sha ◽  
Bavo Langerock ◽  
Jean-François L. Blavier ◽  
Thomas Blumenstock ◽  
Tobias Borsdorff ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Mole Fraction ◽  
Land Surface ◽  
Systematic Difference ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
Dry Air ◽  
Wide Range ◽  
Quality Filtering ◽  
Total Column

Abstract. The Sentinel-5 Precursor (S5P) mission with the TROPOspheric Monitoring Instrument (TROPOMI) on board has been measuring solar radiation backscattered by the Earth's atmosphere and surface since its launch on 13 October 2017. In this paper, we present for the first time the S5P operational methane (CH4) and carbon monoxide (CO) products' validation results covering a period of about 3 years using global Total Carbon Column Observing Network (TCCON) and Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG) network data, accounting for a priori alignment and smoothing uncertainties in the validation, and testing the sensitivity of validation results towards the application of advanced co-location criteria. We found that the S5P standard and bias-corrected CH4 data over land surface for the recommended quality filtering fulfil the mission requirements. The systematic difference of the bias-corrected total column-averaged dry air mole fraction of methane (XCH4) data with respect to TCCON data is -0.26±0.56 % in comparison to -0.68±0.74 % for the standard XCH4 data, with a correlation of 0.6 for most stations. The bias shows a seasonal dependence. We found that the S5P CO data over all surfaces for the recommended quality filtering generally fulfil the missions requirements, with a few exceptions, which are mostly due to co-location mismatches and limited availability of data. The systematic difference between the S5P total column-averaged dry air mole fraction of carbon monoxide (XCO) and the TCCON data is on average 9.22±3.45 % (standard TCCON XCO) and 2.45±3.38 % (unscaled TCCON XCO). We found that the systematic difference between the S5P CO column and NDACC CO column (excluding two outlier stations) is on average 6.5±3.54 %. We found a correlation of above 0.9 for most TCCON and NDACC stations. The study shows the high quality of S5P CH4 and CO data by validating the products against reference global TCCON and NDACC stations covering a wide range of latitudinal bands, atmospheric conditions and surface conditions.

scholarly journals Study of outcome of the treatment with intravenous iron sucrose in moderately anaemic pregnant women

2019 ◽  
Vol 8 (9) ◽  
pp. 3480
Author(s):  
Kohila Kalimuthu ◽  
Vanusha Avudaithangam
Keyword(s):  
Standard Deviation ◽  
Iron Deficiency ◽  
Pregnant Women ◽  
Iron Deficiency Anaemia ◽  
Intravenous Iron ◽  
Iron Sucrose ◽  
P Value ◽  
Deficiency Anaemia ◽  
The Mean ◽  
The Difference

Background: Moderate anaemia seen in about 15-20% of pregnant women. Iron sucrose complex which is used intravenously for the correction of Iron deficiency anaemia. The drug has been able to raise the haemoglobin to satisfactory level when used in moderately anaemic iron deficient pregnant women. The objective of this study was to study the improvement of Hb% after treatment with intravenous Iron sucrose complex in moderately anaemic pregnant women belonging to 24-32 weeks of gestational age.Methods: 50 antenatal patients between gestational age 24-32 weeks with hemoglobin between 8-9.5g/dl were selected and included in this study. They were subjected to blood hemoglobin estimation, hematocrit and peripheral smear study. In each infusion, the maximum total dose administered was 200 mg iron sucrose in 100 ml of normal saline, slow IV infused over 30 minutes. Monitoring was done throughout the infusion to observe for any side effects.Results: Mean hemoglobin among the 50 patients before starting the therapy was 8.172g/dl and the mean hemoglobin at the end of one month of completing the therapy was 11.066g/dl. The rise in mean hemoglobin i.e. the difference in the mean hemoglobin before and after treatment was 2.894g/dl. The p value is 0.0001 which is statistically significant. The mean hematocrit of the 50 patients studied before starting the treatment was 26.772% with a standard deviation of 1.914. The mean hematocrit after completing the therapy was 33.872% with a standard deviation of 1.321. The difference in the mean hematocrit was 7.100% with a p value of 0.0001 which is statistically significant.Conclusions: Intravenous iron sucrose complex is well tolerated and highly efficacious in improving hemoglobin, hematocrit in the treatment of iron deficiency anaemia in antenatal women.

EVALUATION OF QUALITY OF POULTRY FEEDS SOLD IN KATSINA METROPOLIS, KATSINA STATE, NIGERIA

2021 ◽  
Vol 5 (1) ◽  
pp. 601-607
Author(s):  
A. U. Uduma ◽  
Joseph Akumah Ojogba ◽  
O. E. Okafor
Keyword(s):  
Standard Deviation ◽  
Crude Protein ◽  
Proximate Analysis ◽  
Crude Protein Content ◽  
Poultry Feeds ◽  
Crude Fiber Content ◽  
Percent Moisture ◽  
The Mean ◽  
The Difference

In Katsina metropolitan, a variety of poultry feeds are available, and the quality and standards of these feeds are critical for the production of eggs and meat. As a result, the quality of selected chicken feeds sold in Katsina metropolitan was assessed by performing proximate analysis using AOAC methodology. Super starter, grower concentrate, broiler finisher, broiler starter, broiler super starter, layer mesh, grower mesh, and layer concentrate were among the samples used. The percentage mean to standard deviation was used to express the findings. The crude protein content of the diets studied ranged from 0.46 ± 0.00 percent to, 8.24± 0.02 percent, ash content 6.31± 0.01 percent – 33.30± 0.04 percent, crude fiber content 1.03 ±0.00 percent – 3.21± 0.00 percent, lipid content 0.11± 0.00 percent, 2.30 ±0.00 percent, moisture content 4.28 ±0.25 – 6.66 ±0.78 percent, and carbohydrate content 51.78± 2.68 – 83.72 ±0.57 percent. Although there was variation in the mean and standard deviation levels among the samples analyzed, such variations were not statistically significant (P>0.05) according to a one-way analysis of variance (ANOVA) for the difference in the mean levels of parameters evaluated in eight samples

scholarly journals Retrieval of atmospheric CH<sub>4</sub> vertical information from ground-based FTS near-infrared spectra

2019 ◽  
Vol 12 (11) ◽  
pp. 6125-6141 ◽  
Author(s):  
Minqiang Zhou ◽  
Bavo Langerock ◽  
Mahesh Kumar Sha ◽  
Nicolas Kumps ◽  
Christian Hermans ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Mole Fraction ◽  
Atmospheric Chemistry ◽  
Near Infrared ◽  
Satellite Observations ◽  
Total Carbon ◽  
Fourier Transform Spectrometer ◽  
Aircraft Measurements ◽  
Retrieval Software ◽  
Total Column

Abstract. The Total Carbon Column Observing Network (TCCON) column-averaged dry air mole fraction of CH4 (XCH4) measurements have been widely used to validate satellite observations and to estimate model simulations. The GGG2014 code is the standard TCCON retrieval software used in performing a profile scaling retrieval. In order to obtain several vertical pieces of information in addition to the total column, in this study, the SFIT4 retrieval code is applied to retrieve the CH4 mole fraction vertical profile from the Fourier transform spectrometer (FTS) spectrum at six sites (Ny-Ålesund, Sodankylä, Bialystok, Bremen, Orléans and St Denis) during the time period of 2016–2017. The retrieval strategy of the CH4 profile retrieval from ground-based FTS near-infrared (NIR) spectra using the SFIT4 code (SFIT4NIR) is investigated. The degree of freedom for signal (DOFS) of the SFIT4NIR retrieval is about 2.4, with two distinct pieces of information in the troposphere and in the stratosphere. The averaging kernel and error budget of the SFIT4NIR retrieval are presented. The data accuracy and precision of the SFIT4NIR retrievals, including the total column and two partial columns (in the troposphere and stratosphere), are estimated by TCCON standard retrievals, ground-based in situ measurements, Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) satellite observations, TCCON proxy data and AirCore and aircraft measurements. By comparison against TCCON standard retrievals, it is found that the retrieval uncertainty of SFIT4NIR XCH4 is similar to that of TCCON standard retrievals with systematic uncertainty within 0.35 % and random uncertainty of about 0.5 %. The tropospheric and stratospheric XCH4 from SFIT4NIR retrievals are assessed by comparison with AirCore and aircraft measurements, and there is a 1.0 ± 0.3 % overestimation in the SFIT4NIR tropospheric XCH4 and a 4.0 ± 2.0 % underestimation in the SFIT4NIR stratospheric XCH4, which are within the systematic uncertainties of SFIT4NIR-retrieved partial columns in the troposphere and stratosphere respectively.

Carbon dioxide and methane RemoTeC retrievals from GOSAT (2009-2019) and GOSAT-2 (2019)

2020 ◽  
Author(s):  
Markus Haun ◽  
Hiroshi Suto ◽  
André Butz
Keyword(s):  
Carbon Dioxide ◽  
Bias Correction ◽  
Total Carbon ◽  
Dry Air ◽  
The Earth ◽  
First Results ◽  
Process Measurements ◽  
Spectral Ranges ◽  
Atmospheric Concentrations ◽  
Band Signal

&lt;p&gt;The Japanese Greenhouse gases Observing SATellite (GOSAT), in orbit since January 2009, and its successor GOSAT-2, in orbit since October 2018, are dedicated to enhancing our knowledge of the carbon cycle. We use our RemoTeC full-physics algorithm to infer atmospheric concentrations and auxiliary parameters from the measured solar SWIR radiances backscattered at the earth&amp;#180;s atmosphere and surface. Accuracy requirements are a major challenge for these space-based measurements of column-averaged dry-air mole fractions of carbon dioxide and methane (XCO&lt;sub&gt;2&lt;/sub&gt; and XCH&lt;sub&gt;4&lt;/sub&gt;).&lt;/p&gt;&lt;p&gt;Here we present 1) a consolidated ten years GOSAT XCO&lt;sub&gt;2&lt;/sub&gt; and XCH&lt;sub&gt;4&lt;/sub&gt; dataset and 2) first results for GOSAT-2 XCO&lt;sub&gt;2&lt;/sub&gt; and XCH&lt;sub&gt;4&lt;/sub&gt; retrievals. For GOSAT, 4.8 % of all measurements pass our cloud filter, based on the O&lt;sub&gt;2&lt;/sub&gt; A-band signal and several quality filters. For validation and bias-correction, we use collocated measurements from ground-based stations of the Total Carbon Column Observing Network (TCCON). The dataset shows a scatter of well below 1 %. For GOSAT-2, we are able to reliably process measurements in land nadir and ocean glint geometry. In addition to the retrieval windows implemented for GOSAT, we use the spectral ranges at 4290 - 4328 cm&lt;sup&gt;-1&lt;/sup&gt; and 4354 - 4441 cm&lt;sup&gt;-1&lt;/sup&gt; to retrieve carbon monoxide and nitrous oxide concentrations. We evaluate instrument performance and precision by comparing XCO&lt;sub&gt;2&lt;/sub&gt; and XCH&lt;sub&gt;4&lt;/sub&gt; retrievals to both collocated GOSAT and ground-based TCCON measurements.&lt;/p&gt;

scholarly journals Validation of SCIAMACHY HDO/H<sub>2</sub>O measurements using the TCCON and NDACC-MUSICA networks

2015 ◽  
Vol 8 (4) ◽  
pp. 1799-1818 ◽  
Author(s):  
R. A. Scheepmaker ◽  
C. Frankenberg ◽  
N. M. Deutscher ◽  
M. Schneider ◽  
S. Barthlott ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Hydrological Cycle ◽  
Source Region ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
The Tibetan Plateau ◽  
Wet Season ◽  
Data Set ◽  
The Mean ◽  
The Impact

Abstract. Measurements of the atmospheric HDO/H2O ratio help us to better understand the hydrological cycle and improve models to correctly simulate tropospheric humidity and therefore climate change. We present an updated version of the column-averaged HDO/H2O ratio data set from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The data set is extended with 2 additional years, now covering 2003–2007, and is validated against co-located ground-based total column δD measurements from Fourier transform spectrometers (FTS) of the Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC, produced within the framework of the MUSICA project). Even though the time overlap among the available data is not yet ideal, we determined a mean negative bias in SCIAMACHY δD of −35 ± 30‰ compared to TCCON and −69 ± 15‰ compared to MUSICA (the uncertainty indicating the station-to-station standard deviation). The bias shows a latitudinal dependency, being largest (∼ −60 to −80‰) at the highest latitudes and smallest (∼ −20 to −30‰) at the lowest latitudes. We have tested the impact of an offset correction to the SCIAMACHY HDO and H2O columns. This correction leads to a humidity- and latitude-dependent shift in δD and an improvement of the bias by 27‰, although it does not lead to an improved correlation with the FTS measurements nor to a strong reduction of the latitudinal dependency of the bias. The correction might be an improvement for dry, high-altitude areas, such as the Tibetan Plateau and the Andes region. For these areas, however, validation is currently impossible due to a lack of ground stations. The mean standard deviation of single-sounding SCIAMACHY–FTS differences is ∼ 115‰, which is reduced by a factor ∼ 2 when we consider monthly means. When we relax the strict matching of individual measurements and focus on the mean seasonalities using all available FTS data, we find that the correlation coefficients between SCIAMACHY and the FTS networks improve from 0.2 to 0.7–0.8. Certain ground stations show a clear asymmetry in δD during the transition from the dry to the wet season and back, which is also detected by SCIAMACHY. This asymmetry points to a transition in the source region temperature or location of the water vapour and shows the added information that HDO/H2O measurements provide when used in combination with variations in humidity.

scholarly journals Carbon dioxide retrieval from OCO-2 satellite observations using the RemoTeC algorithm and validation with TCCON measurements

2018 ◽  
Vol 11 (5) ◽  
pp. 3111-3130 ◽  
Author(s):  
Lianghai Wu ◽  
Otto Hasekamp ◽  
Haili Hu ◽  
Jochen Landgraf ◽  
Andre Butz ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Bias Correction ◽  
Goodness Of Fit ◽  
Satellite Observations ◽  
Total Carbon ◽  
A Posteriori ◽  
Gas Concentration ◽  
Dry Air ◽  
Spectral Bands ◽  
A Value

Abstract. In this study we present the retrieval of the column-averaged dry air mole fraction of carbon dioxide (XCO2) from the Orbiting Carbon Observatory-2 (OCO-2) satellite observations using the RemoTeC algorithm, previously successfully applied to retrieval of greenhouse gas concentration from the Greenhouse Gases Observing Satellite (GOSAT). The XCO2 product has been validated with collocated ground-based measurements from the Total Carbon Column Observing Network (TCCON) for almost 2 years of OCO-2 data from September 2014 to July 2016. We found that fitting an additive radiometric offset in all three spectral bands of OCO-2 significantly improved the retrieval. Based on a small correlation of the XCO2 error over land with goodness of fit, we applied an a posteriori bias correction to our OCO-2 retrievals. In overpass averaged results, XCO2 retrievals have an SD of  ∼ 1.30 ppm and a station-to-station variability of  ∼ 0.40 ppm among collocated TCCON sites. The seasonal relative accuracy (SRA) has a value of 0.52 ppm. The validation shows relatively larger difference with TCCON over high-latitude areas and some specific regions like Japan.

scholarly journals A performance assessment of the World Wide Lightning Location Network (WWLLN) via comparison with the Canadian Lightning Detection Network (CLDN)

2010 ◽  
Vol 3 (2) ◽  
pp. 1861-1887 ◽  
Author(s):  
D. Abreu ◽  
D. Chandan ◽  
R. H. Holzworth ◽  
K. Strong
Keyword(s):  
Standard Deviation ◽  
World Wide ◽  
Detection Efficiency ◽  
Low Frequency ◽  
High Peak ◽  
Peak Current ◽  
Lightning Detection ◽  
The World ◽  
The Mean ◽  
The Difference

Abstract. The World Wide Lightning Location Network (WWLLN) uses globally-distributed Very Low Frequency (VLF) receivers in order to observe lightning around the globe. Its objective is to locate as many global strokes as possible, with high temporal and spatial (<10 km) accuracy. Since detection is done in the VLF range, signals from high peak current lightning strokes are able to propagate up to ~104 km before being detected by the WWLLN sensors, allowing for receiving stations to be sparsely spaced. Through a comparison with measurements made by the Canadian Lightning Detection Network (CLDN) between May and August 2008 over a 4° latitude by 4° longitude region centered on Toronto, Canada, this study found that WWLLN detection was most sensitive to high peak current lightning strokes. Events were considered shared between the two networks if they fell within 0.5 ms of each other. Using this criterion, 19 128 WWLLN strokes (analyzed using the Stroke_B algorithm) were shared with CLDN lightning strokes, producing a detection efficiency of 2.8%. The peak current threshold for WWLLN detection is found to be ~20 kA, with the detection efficiency increasing to ~70% at peak currents of ±120 kA. The detection efficiency is seen to have a clear diurnal dependence, with a higher detection efficiency at local midnight than at local noon; this is attributed to the difference in the thickness of the ionospheric D-region between night and day. The mean time difference (WWLLN – CLDN) between shared events was −6.44 μs with a standard deviation of 35 μs, and the mean absolute location accuracy was 7.24 km with a standard deviation of 6.34 km. These results are generally consistent with previous comparison studies of the WWLLN with other regional networks around the world. Additional receiver stations are continuously being added to the network, acting to improve this detection efficiency.

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