scholarly journals Comparison of Optimal Estimation HDO/H2O Retrievals from AIRS with ORACLES measurements

2019 ◽  
Author(s):  
Robert L. Herman ◽  
John Worden ◽  
David Noone ◽  
Dean Henze ◽  
Kevin Bowman ◽  
...  
Keyword(s):  
A Priori ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Deuterium Content ◽  
Aircraft Measurements ◽  
State University ◽  
Atmospheric Infrared Sounder ◽  
Fractional Deviation ◽  
Oregon State University

Abstract. In this paper we evaluate new retrievals of the deuterium content of water vapor from the Aqua Atmospheric InfraRed Sounder (AIRS) with aircraft measurements of HDO and H2O from the ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) field mission. Single footprint AIRS radiances are processed with an optimal estimation algorithm that provides a vertical profile of the HDO/H2O ratio, characterized uncertainties, and instrument operators (or averaging kernel matrix). These retrievals are compared to vertical profiles of the HDO/H2O from the Oregon State University Water Isotope Spectrometer for Precipitation and Entrainment Research (WISPER) on the ORACLES NASA P-3B Orion aircraft. Measurements were taken over the Southeast Atlantic Ocean from 31 August to 25 September 2016. HDO/H2O is commonly reported in delta-D notation, which is the fractional deviation of the HDO/H2O ratio from the standard reference ratio. For collocated measurements, the satellite operator (averaging kernels and a priori constraint) is applied to the aircraft profile measurements. We find that AIRS delta-D bias relative to the aircraft is well within the estimated measurement uncertainty. In the lower troposphere, 1000 to 800 hPa, AIRS delta-D bias is −6.6‰ and the Root Mean Square (RMS) deviation is 20.9‰, consistent with the calculated uncertainty of 19.1‰. In the mid-troposphere, 800 to 500 hPa, AIRS delta-D bias is 6.8‰ and RMS 44.9‰, comparable to the calculated uncertainty of 25.8‰.

scholarly journals Comparison of optimal estimation HDO∕H<sub>2</sub>O retrievals from AIRS with ORACLES measurements

2020 ◽  
Vol 13 (4) ◽  
pp. 1825-1834
Author(s):  
Robert L. Herman ◽  
John Worden ◽  
David Noone ◽  
Dean Henze ◽  
Kevin Bowman ◽  
...  
Keyword(s):  
A Priori ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Deuterium Content ◽  
Vertical Profiles ◽  
Aircraft Measurements ◽  
State University ◽  
Atmospheric Infrared Sounder ◽  
Fractional Deviation

Abstract. In this paper we evaluate new retrievals of the deuterium content of water vapor from the Aqua Atmospheric InfraRed Sounder (AIRS), with aircraft measurements of HDO and H2O from the ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) field mission. Single-footprint AIRS radiances are processed with an optimal estimation algorithm that provides vertical profiles of the HDO∕H2O ratio, characterized uncertainties and instrument operators (i.e., averaging kernel matrix). These retrievals are compared to vertical profiles of the HDO∕H2O ratio from the Oregon State University Water Isotope Spectrometer for Precipitation and Entrainment Research (WISPER) on the ORACLES NASA P-3B Orion aircraft. Measurements were taken over the southeastern Atlantic Ocean from 31 August to 25 September 2016. HDO∕H2O is commonly reported in δD notation, which is the fractional deviation of the HDO∕H2O ratio from the standard reference ratio. For collocated measurements, the satellite instrument operator (averaging kernels and a priori constraint) is applied to the aircraft profile measurements. We find that AIRS δD bias relative to the aircraft is well within the estimated measurement uncertainty. In the lower troposphere, 1000 to 800 hPa, AIRS δD bias is −6.6 ‰ and the root-mean-square (rms) deviation is 20.9 ‰, consistent with the calculated uncertainty of 19.1 ‰. In the mid-troposphere, 800 to 500 hPa, AIRS δD bias is −6.8 ‰ and rms 44.9 ‰, comparable to the calculated uncertainty of 25.8 ‰.

scholarly journals Characterization and evaluation of AIRS-based estimates of the deuterium content of water vapor

2019 ◽  
Vol 12 (4) ◽  
pp. 2331-2339 ◽  
Author(s):  
John R. Worden ◽  
Susan S. Kulawik ◽  
Dejian Fu ◽  
Vivienne H. Payne ◽  
Alan E. Lipton ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Latitudinal Variation ◽  
Deuterium Content ◽  
Atmospheric Infrared Sounder ◽  
Single Target ◽  
Similar Accuracy ◽  
The Tropics

Abstract. Single-pixel tropospheric retrievals of HDO and H2O concentrations are retrieved from Atmospheric Infrared Sounder (AIRS) radiances using the optimal estimation algorithm developed for the Aura Tropospheric Emission Spectrometer (TES) project. We evaluate the error characteristics and vertical sensitivity of AIRS measurements corresponding to 5 d of TES data (or five global surveys) during the Northern Hemisphere summers between 2006 and 2010 (∼600 co-located comparisons per day). We find that the retrieval characteristics of the AIRS deuterium content measurements have similar vertical resolution in the middle troposphere as TES but with slightly less sensitivity in the lowermost troposphere, with a typical degrees of freedom (DOFS) in the tropics of 1.5. The calculated measurement uncertainty is ∼30 ‰ (parts per thousand relative to the deuterium composition of ocean water) for a tropospheric average between 750 and 350 hPa, the altitude region where AIRS is most sensitive, compared to ∼15 ‰ for the TES data. Comparison with the TES data also indicates that the uncertainty of a single target AIRS HDO ∕ H2O measurement is ∼30 ‰. Comparison of AIRS and TES data between 30∘ S and 50∘ N indicates that the AIRS data are biased low by ∼-2.6 ‰ with a latitudinal variation of ∼7.8 ‰. This latitudinal variation is consistent with the accuracy of TES data compared to in situ measurements, suggesting that both AIRS and TES have similar accuracy.

scholarly journals Retrieval of temperature and water vapor profiles from radio occultation refractivity and bending angle measurements using an Optimal Estimation approach: a simulation study

2005 ◽  
Vol 5 (6) ◽  
pp. 1665-1677 ◽  
Author(s):  
A. von Engeln ◽  
G. Nedoluha
Keyword(s):  
Water Vapor ◽  
Radio Occultation ◽  
A Priori ◽  
Estimation Method ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Pronounced Difference ◽  
Bending Angle ◽  
Advantages And Disadvantages ◽  
The Impact

Abstract. The Optimal Estimation Method is used to retrieve temperature and water vapor profiles from simulated radio occultation measurements in order to assess how different retrieval schemes may affect the assimilation of this data. High resolution ECMWF global fields are used by a state-of-the-art radio occultation simulator to provide quasi-realistic bending angle and refractivity profiles. Both types of profiles are used in the retrieval process to assess their advantages and disadvantages. The impact of the GPS measurement is expressed as an improvement over the a priori knowledge (taken from a 24h old analysis). Large improvements are found for temperature in the upper troposphere and lower stratosphere. Only very small improvements are found in the lower troposphere, where water vapor is present. Water vapor improvements are only significant between about 1 km to 7 km. No pronounced difference is found between retrievals based upon bending angles or refractivity. Results are compared to idealized retrievals, where the atmosphere is spherically symmetric and instrument noise is not included. Comparing idealized to quasi-realistic calculations shows that the main impact of a ray tracing algorithm can be expected for low latitude water vapor, where the horizontal variability is high. We also address the effect of altitude correlations in the temperature and water vapor. Overall, we find that water vapor and temperature retrievals using bending angle profiles are more CPU intensive than refractivity profiles, but that they do not provide significantly better results.

scholarly journals Validation and Error Estimation of AIRS MUSES CO Profiles with HIPPO, ATom and NOAA GML Aircraft Observations

2021 ◽  
Author(s):  
Jennifer D. Hegarty ◽  
Karen E. Cady-Pereira ◽  
Vivienne H. Payne ◽  
Susan S. Kulawik ◽  
John R. Worden ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
Optimal Estimation ◽  
Reference Network ◽  
Atmospheric Infrared Sounder ◽  
Tropical Regions ◽  
Mixing Ratios ◽  
Bias Drift ◽  
Time Period ◽  
Aircraft Observations ◽  
Standard Deviations

Abstract. Single footprint retrievals of carbon monoxide from the Atmospheric Infrared Sounder (AIRS) are evaluated using aircraft in situ observations. The aircraft data are from the HIAPER Pole-to-Pole (HIPPO, 2009–2011), the first three Atmospheric Tomography Mission (ATom, 2016–2017) campaigns and the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory (GML) Global Greenhouse Gas Reference Network Aircraft Program from 2006–2017. The retrievals are obtained using an optimal estimation approach within the MUlti-SpEctra, MUlti-SpEcies, MUlti-Sensors (MUSES) algorithm. Retrieval biases and estimated errors are evaluated across a range of latitudes from the sub-polar to tropical regions over both ocean and land points. AIRS MUSES CO profiles were compared with HIPPO, ATom, and NOAA GML aircraft observations with a coincidence of 9 hours and 50 km to estimate retrieval biases and standard deviations. Comparisons were done for different pressure levels and column averages, latitudes, day, night, land, and ocean observations. We find mean biases of +6.6 % +/− 4.6 %, +0.6 % +/− 3.2 %, −6.1 % +/− 3.0 %, and 1.4 % +/− 3.6 %, for 750 hPa, 510 hPa, 287 hPa, and the column averages, respectively. The mean standard deviation is 15 %, 11 %, 12 %, and 9 % at these same pressure levels, respectively. Observation errors (theoretical errors) from the retrievals were found to be broadly consistent in magnitude with those estimated empirically from ensembles of satellite aircraft comparisons. The GML Aircraft Program comparisons generally had higher standard deviations and biases than the HIPPO and ATom comparisons. Since the GML aircraft flights do not go as high as the HIPPO and ATom flights, results from these GML comparisons are more sensitive to the choice of method for extrapolation of the aircraft profile above the uppermost measurement altitude. The AIRS retrieval performance shows little sensitivity to surface type (land or ocean) or day or night but some sensitivity to latitude. Comparisons to the NOAA GML set spanning the years 2006–2017 show that the AIRS retrievals are able to capture the distinct seasonal cycles but show a high bias of ~20 % in the lower troposphere during the summer when observed CO mixing ratios are at annual minimum values. The retrieval bias drift was examined over the same period and found to be small at < 0.5 % over the 2006–2017 time period.

scholarly journals The global tropospheric ammonia distribution as seen in the 13 year AIRS measurement record

2015 ◽  
Vol 15 (24) ◽  
pp. 35823-35856 ◽  
Author(s):  
J. X. Warner ◽  
Z. Wei ◽  
L. L. Strow ◽  
R. R. Dickerson ◽  
J. B. Nowak
Keyword(s):  
South America ◽  
A Priori ◽  
Optimal Estimation ◽  
Retrieval Algorithm ◽  
Aerosol Formation ◽  
Atmospheric Infrared Sounder ◽  
Animal Feeding Operations ◽  
Source Regions ◽  
Summer Maximum ◽  
Spring Maximum

Abstract. Ammonia (NH3) plays an increasingly important role in the global biogeochemical cycle of reactive nitrogen as well as in aerosol formation and climate. We present extensive and nearly continuous global ammonia measurements made by the Atmospheric Infrared Sounder (AIRS) from the Aqua satellite to identify and quantify major persistent and episodic sources as well as to characterize seasonality. We examine the 13 year period from September 2002 through August 2015 with a retrieval algorithm using an optimal estimation technique with a set of three, spatially and temporally uniform a priori profiles. Vertical profiles show good agreement (~5–15 %) between AIRS NH3 and the in situ profiles from the winter 2013 DISCOVER-AQ field campaign in central California, despite the likely biases due to spatial resolution differences between the two instruments. AIRS captures the strongest consistent NH3 emissions from the anthropogenic (agricultural) source regions, such as, South Asia (India/Pakistan), China, the US, parts of Europe, SE Asia (Thailand/Myanmar/Laos), the central portion of South America, as well as Western and Northern Africa. These correspond primarily to croplands with extensive animal feeding operations and fertilizer applications where a summer maximum and secondary spring maximum are reliably observable. In the Southern Hemisphere (SH) regular agricultural fires contribute to a spring maximum. Regions of strong episodic emissions include Russia and Alaska as well as parts of South America, Africa, and Indonesia. Biomass burning, especially wildfires, dominate these episodic NH3 emissions.

scholarly journals Optimal estimation of tropospheric H<sub>2</sub>O and δD with IASI/METOP

2011 ◽  
Vol 11 (21) ◽  
pp. 11207-11220 ◽  
Author(s):  
M. Schneider ◽  
F. Hase
Keyword(s):  
A Priori ◽  
Measurement Techniques ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Atmospheric Temperature ◽  
Data Sets ◽  
Upper Troposphere ◽  
Systematic Uncertainties ◽  
Better Than

Abstract. We present optimal estimates of tropospheric H2O and δD derived from radiances measured by the instrument IASI (Infrared Atmospheric Sounding Interferometer) flown on EUMETSAT's polar orbiter METOP. We document that the IASI spectra allow for retrieving H2O profiles between the surface and the upper troposphere as well as middle tropospheric δD values. A theoretical error estimation suggests a precision for H2O of better than 35% in the lower troposphere and of better than 15% in the middle and upper troposphere, respectively, whereby surface emissivity and atmospheric temperature uncertainties are the leading error sources. For the middle tropospheric δD values we estimate a precision of 15–20‰ with the measurement noise being the dominating error source. The accuracy of the IASI products is estimated to about 20–10% and 10‰ for lower to upper tropospheric H2O and middle tropospheric δD, respectively. It is limited by systematic uncertainties in the applied spectroscopic parameters and the a priori atmospheric temperature profiles. We compare our IASI products to a large number of near coincident radiosonde in-situ and ground-based FTS (Fourier Transform Spectrometer) remote sensing measurements. The bias and the scatter between the different H2O and δD data sets are consistent with the combined theoretical uncertainties of the involved measurement techniques.

scholarly journals Characterization and Evaluation of AIRS-Based Estimates of the Deuterium Content of Water Vapor

2018 ◽  
Author(s):  
John R. Worden ◽  
Susan S. Kulawik ◽  
Dejian Fu ◽  
Vivienne H. Payne ◽  
Alan E. Lipton ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Degrees Of Freedom ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Latitudinal Variation ◽  
Deuterium Content ◽  
Vertical Resolution ◽  
Single Target ◽  
The Difference ◽  
Similar Accuracy

Abstract. Single pixel, tropospheric retrievals of HDO and H2O concentrations are retrieved from Atmospheric Infrared Sounder (AIRS) radiances using the optimal estimation algorithm developed for the Aura Tropospheric Emission Spectrometer (TES) project. These retrievals are evaluated against co-located TES observations taken between 2006 through 2010. We evaluate the error characteristics and vertical sensitivity of AIRS measurements corresponding to five days of TES data (or 5 global surveys) during the N. Hemisphere summers between 2006 and 2010 (~ 600 co-located comparisons per day). We find that the retrieval characteristics of the AIRS deuterium content measurements have similar vertical resolution and uncertainty in the middle-troposphere as TES but with slightly less sensitivity in the lower-most troposphere, with a typical degrees-of-freedom (DOFS) in the tropics of 1.5. The difference in sensitivity to the lower-most troposphere is mostly likely due to the reduced spectral resolution as previous studies found that spectral resolution was the primary factor, relative to signal-to-noise, affecting the vertical resolution of nadir sounding retrievals (Worden et al., 2004). The calculated measurement uncertainty is ~ 30 per mil (parts per thousand relative to the deuterium composition of ocean water) for a tropospheric average between 750 and 350 hPa, the altitude region where AIRS is most sensitive. Comparison with the TES data suggest that the calculated and actual uncertainty of a single target AIRS HDO/H2O measurement ~ 30 per mil. Comparison of AIRS and TES data between 30 S and 50 N suggest that the AIRS data is biased low by ~ −2.6 per mil with a latitudinal variation of ~ 7.8 per mil. This latitudinal variation is consistent with the accuracy of TES data as compared to in situ measurements, suggesting that both AIRS and TES have similar accuracy.

scholarly journals Daytime HONO, NO<sub>2</sub> and aerosol distributions from MAX-DOAS observations in Melbourne

2018 ◽  
Author(s):  
Robert G. Ryan ◽  
Steve Rhodes ◽  
Matthew Tully ◽  
Stephen Wilson ◽  
Nicholas Jones ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
A Priori ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Oxidative Capacity ◽  
Urban Environments ◽  
Vertical Profiles ◽  
Pollution Levels ◽  
The World ◽  
Gas Measurements

Abstract. Nitrogen oxides produced by high temperature combustion are prevalent in urban environments and toxic, contributing to a significant health burden. The chemistry of nitrogen oxides such as NO2 and HONO in pollution are important for hydroxyl radical production and overall oxidative capacity in urban environments, however current mechanisms cannot explain high daytime levels of HONO observed in many urban and rural locations around the world. Here we present HONO, NO2 and aerosol extinction vertical distributions retrieved from MAX-DOAS measurements in suburban Melbourne, which are the first MAX-DOAS results from Australia. Using the optimal estimation algorithm HEIPRO we show that vertical profiles for NO2 and HONO can be calculated with low dependence on the retrieval forward model and a priori parameters, despite a lack of independent co-located aerosol or trace gas measurements. Between December 2016 and April 2017 average peak NO2 values of 8 ± 2 ppb indicated moderate traffic pollution levels, and high daytime peak values of HONO were frequently detected, averaging 220 ± 30 ppt in the middle of the day. HONO levels measured in Melbourne were typically lower than those recorded in the morning in other places around the world, indicating minimal overnight accumulation, but peaked in the middle of the day to be commensurate with midday concentrations in locations with much higher NO2 pollution. Regular midday peaks in the diurnal cycle of HONO surface concentrations have only previously been reported in rural locations. The HONO measured represents an OH radical source in the middle of the day in Melbourne up to ten times stronger than from ozone photolysis. The dependence of the high HONO levels on time since rainfall, combined with the observed diurnal and vertical profiles, provide evidence for a strong photo-activated and ground-based daytime HONO source.

On the Challenges of Tomography Retrievals of a 2D Water Vapor Field Using Ground-Based Microwave Radiometers: An Observation System Simulation Experiment

2015 ◽  
Vol 32 (1) ◽  
pp. 116-130 ◽  
Author(s):  
Véronique Meunier ◽  
David D. Turner ◽  
Pavlos Kollias
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Turbulent Boundary Layer ◽  
Covariance Matrix ◽  
A Priori ◽  
Simulated Data ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Observation System ◽  
Microwave Radiometers

AbstractTwo-dimensional water vapor fields were retrieved by simulated measurements from multiple ground-based microwave radiometers using a tomographic approach. The goal of this paper was to investigate how the various aspects of the instrument setup (number and spacing of elevation angles and of instruments, number of frequencies, etc.) affected the quality of the retrieved field. This was done for two simulated atmospheric water vapor fields: 1) an exaggerated turbulent boundary layer and 2) a simplified water vapor front. An optimal estimation algorithm was used to obtain the tomographic field from the microwave radiometers and to evaluate the fidelity and information content of this retrieved field.While the retrieval of the simplified front was reasonably successful, the retrieval could not reproduce the details of the turbulent boundary layer field even using up to nine instruments and 25 elevation angles. In addition, the vertical profile of the variability of the water vapor field could not be captured. An additional set of tests was performed using simulated data from a Raman lidar. Even with the detailed lidar measurements, the retrieval did not succeed except when the lidar data were used to define the a priori covariance matrix. This suggests that the main limitation to obtaining fine structures in a retrieved field using tomographic retrievals is the definition of the a priori covariance matrix.

scholarly journals Information-based mid-upper tropospheric methane derived from Atmospheric Infrared Sounder (AIRS) and its validation

2009 ◽  
Vol 9 (4) ◽  
pp. 16331-16360 ◽  
Author(s):  
X. Xiong ◽  
C. Barnet ◽  
J. Wei ◽  
E. Maddy
Keyword(s):  
Temporal Variation ◽  
High Latitude ◽  
A Priori ◽  
Thermal Infrared ◽  
Lapse Rate ◽  
Spatial And Temporal Variation ◽  
Aircraft Measurements ◽  
Infrared Sensors ◽  
Atmospheric Infrared Sounder ◽  
Temperature Lapse Rate

Abstract. Atmospheric Infrared Sounder (AIRS) measurements of methane (CH4) generally contain about 1.0 degree of freedom and are therefore dependent on a priori assumptions about the vertical methane distribution as well as the temperature lapse rate and the amount of moisture. Thus it requires that interpretation and/or analysis of the CH4 spatial and temporal variation based on the AIRS retrievals need to use the averaging kernels (AK). To simplify the use of satellite retrieved products for scientific analysis, a method based on the information content of the retrievals is developed, in which the AIRS retrieved CH4 in the layer from 50 to 250 hPa below the tropopause is used to characterize the mid-upper tropospheric CH4 in the mid-high latitude regions. The basis of this method is that in the mid-high latitude regions the maximum sensitive layers of AIRS to CH4 have a good correlation with the tropopause heights, and these layers are usually between 50 and 250 hPa below the tropopause. Validation using the aircraft measurements from NOAA/ESRL/GMD and the campaigns INTEX-A and -B indicated that the correlation of AIRS mid-upper tropospheric CH4 with aircraft measurements is ~0.6–0.7, and its the bias and rms difference are less than ±1% and 1.2%, respectively. Further comparison of the CH4 seasonal cycle indicated that the cycle from AIRS mid-upper tropospheric CH4 is in a reasonable agreement with NOAA aircraft measurements. This method provides a simple way to use the thermal infrared sounders data to approximately analyze the spatial and temporal variation CH4 in the upper free tropospere without referring the AK. This method is applicable to derive tropospheric CH4 as well as other trace gases for any thermal infrared sensors.

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