scholarly journals Validation of three different scientific ozone products retrieved from IASI spectra using ozonesondes

2012 ◽  
Vol 5 (3) ◽  
pp. 611-630 ◽  
Author(s):  
G. Dufour ◽  
M. Eremenko ◽  
A. Griesfeller ◽  
B. Barret ◽  
E. LeFlochmoën ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Degrees Of Freedom ◽  
Lower Troposphere ◽  
Natural Variability ◽  
Vertical Resolution ◽  
Random Errors ◽  
Research Teams ◽  
Atmospheric Sounding ◽  
Systematic And Random Errors ◽  
The Tropics

Abstract. Three scientific ozone products from the Infrared Atmospheric Sounding Interferometer (IASI) aboard MetOp-A, retrieved in three different research teams (LA, LATMOS/ULB, LISA) with different retrieval schemes, are characterized and validated using ozonesondes measurements. The characteristics of the products are analyzed in terms of retrieval sensitivity, systematic and random errors, and ability to retrieve the natural variability of ozone and focus on different partial columns from the lower troposphere up to 30 km. The validation covers the midlatitudes and the tropics and the period from January to December 2008. The products present degrees of freedom (DOF) in the troposphere between 1 and 1.2 on average in the midlatitudes and between 1 and 1.4 in the tropics. The DOF are distributed differently on the vertical depending on the profiles and the season: summer leading to a better sensitivity to the lower troposphere, as expected. The error estimates range between 10 and 20% from the lower tropospheric partial columns (0–6 km and 0–8 km for the midlatitudes and the tropics respectively) to the UTLS partial columns (8–16 km and 11–20 km for the midlatitudes and the tropics respectively) for all the products and are about 5% in the stratosphere (16–30 km) and for the column up to 30 km. The main feature that arises from the comparison with the ozonesondes is a systematic overestimation of ozone in the UTLS (between 10 and 25%) by the three products in the midlatitudes and the tropics, attributed to the moderate vertical resolution of IASI and possibly to spectroscopic inconsistencies. The ability of the products to reproduce natural variability of tropospheric ozone is fairly good and depends on the considered season and region.

scholarly journals Validation of three different scientific ozone products retrieved from IASI spectra using ozonesondes

2011 ◽  
Vol 4 (4) ◽  
pp. 5425-5479 ◽  
Author(s):  
G. Dufour ◽  
M. Eremenko ◽  
A. Griesfeller ◽  
B. Barret ◽  
E. LeFlochmoën ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Degrees Of Freedom ◽  
Lower Troposphere ◽  
Natural Variability ◽  
Random Errors ◽  
Research Teams ◽  
Atmospheric Sounding ◽  
Systematic And Random Errors ◽  
The Tropics

Abstract. Three scientific ozone products from the Infrared Atmospheric Sounding Interferometer (IASI) aboard MetOp-A, retrieved in three different research teams (LA, LATMOS/ULB, LISA) with different retrieval schemes, are characterized and validated using ozonesondes measurements. The three products are mature enough to be used for detailed analyses of atmospheric chemistry and transport in the troposphere. The characteristics of the products are analyzed in terms of retrieval sensitivity, systematic and random errors, and ability to retrieve the natural variability of ozone and focus on different partial columns from the lower troposphere up to 30 km. The validation covers the midlatitudes and the tropics and the period from January to December 2008. The products present degrees of freedom (DOF) in the troposphere between 1 and 1.2 on average in the midlatitudes and between 1 and 1.4 in the tropics. The DOF are distributed differently on the vertical depending on the profiles and the season: summer leading to a better sensitivity to the lower troposphere, as expected. The error estimates range between 10 and 20 % from the lower tropospheric partial columns (0–6 km and 0–8 km for the midlatitudes and the tropics respectively) to the UTLS partial columns (8–16 km and 11–20 km for the midlatitudes and the tropics respectively) for all the products and are about 5 % in the stratosphere (16–30 km) and for the column up to 30 km. The main feature that arises from the comparison with the ozonesondes is a systematic overestimation of ozone in the UTLS (between 10 and 25 %) by the three products in the midlatitudes and the tropics, attributed to the moderate vertical resolution of IASI and possibly to spectroscopic inconsistencies. The ability of the products to reproduce natural variability of tropospheric ozone is fairly good and depends on the considered season and region.

scholarly journals Tropospheric ozone from IASI: comparison of different inversion algorithms and validation with ozone sondes in the northern middle latitudes

2009 ◽  
Vol 9 (3) ◽  
pp. 11441-11479 ◽  
Author(s):  
C. Keim ◽  
M. Eremenko ◽  
J. Orphal ◽  
G. Dufour ◽  
J.-M. Flaud ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Concentration Profiles ◽  
Random Errors ◽  
Statistical Validation ◽  
Middle Latitudes ◽  
Atmospheric Sounding ◽  
Systematic And Random Errors ◽  
Mean Differences ◽  
Vertical Ozone ◽  
Different Sources

Abstract. This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the satellite instrument IASI. Since end of 2006, IASI (Infrared Atmospheric Sounding Interferometer) aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. The comparison of the ozone products with the vertical ozone concentration profiles from balloon sondes leads to estimates of the systematic and random errors in the IASI ozone products. The intercomparison of the retrieval results from four different sources (including the EUMETSAT ozone products) shows systematic differences due to the used methods and algorithms. On average the tropospheric columns have a small bias of less than 2 Dobson Units (DU) when compared to the sonde measured columns. The comparison of the still pre-operational EUMETSAT columns shows higher mean differences of about 5 DU.

scholarly journals Validation of six years of TES tropospheric ozone retrievals with ozonesonde measurements: implications for spatial patterns and temporal stability in the TES bias

2013 ◽  
Vol 6 (1) ◽  
pp. 1239-1267 ◽  
Author(s):  
W. W. Verstraeten ◽  
K. F. Boersma ◽  
J. Zörner ◽  
M. A. F. Allaart ◽  
K. W. Bowman ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Degrees Of Freedom ◽  
A Priori ◽  
Temporal Stability ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
The World ◽  
The Difference ◽  
The Tropics

Abstract. In this analysis, Tropospheric Emission Spectrometer (TES) V004 nadir ozone profiles are validated with more than 4400 coinciding ozonesonde measurements taken across the world from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) during the period 2005–2010. The TES observation operator was applied to the sonde data to ensure a consistent comparison between TES and ozonesonde data, i.e. without the influence of the a priori O3 profile needed to regulate the retrieval. Generally, TES V004 ozone retrievals are biased high by 2–7 ppbv in the troposphere, consistent with validation results from earlier studies. Because of two degrees of freedom for signal in the troposphere, we can distinguish between upper and lower troposphere mean biases, respectively ranging from −0.4 to +13.3 ppbv for the upper troposphere and +3.9 to +6.0 ppbv for the lower troposphere. Focusing on the 464 hPa retrieval level, broadly representative for free tropospheric ozone, we find differences in the TES biases for the Tropics (+3 ppbv), sub-tropics (+5 ppbv), and northern (+7 ppbv) and southern mid-latitudes (+4 ppbv). The relatively long-term record (6 yr) of TES-ozonesonde comparisons, allowed us to quantify temporal variations in TES biases in free tropospheric ozone, at 464 hPa. We find that there are no discernable biases in each of these latitudinal bands; temporal variations in the bias are typically within the uncertainty of the difference between TES and ozone-sondes. Establishing these bias patterns is important in order to make meaningful use of TES O3 data in applications such as model evaluation, trend analysis, or data assimilation.

scholarly journals Extending the satellite data record of tropospheric ozone profiles from Aura-TES to MetOp-IASI

2014 ◽  
Vol 7 (7) ◽  
pp. 7013-7051 ◽  
Author(s):  
H. Oetjen ◽  
V. H. Payne ◽  
S. S. Kulawik ◽  
A. Eldering ◽  
J. Worden ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Degrees Of Freedom ◽  
Measurement Noise ◽  
Retrieval Algorithm ◽  
Random Errors ◽  
Sample Covariance ◽  
Atmospheric Sounding ◽  
Data Record ◽  
Retrieval Errors ◽  
Better Than

Abstract. We apply the Tropospheric Emission Spectrometer (TES) ozone retrieval algorithm to Infrared Atmospheric Sounding Instrument (IASI) radiances and characterise the uncertainties and information content of the retrieved ozone profiles. This study focuses on mid-latitudes for the year 2008. We validate our results by comparing the IASI ozone profiles to ozone sondes. In the sonde comparisons, we find a positive bias in the IASI ozone profiles in the UTLS region of up to 14% on average. For the described cases, the degrees of freedom for signal are on average 3.2, 0.3, 0.8, and 0.9 for the columns 0 km–top of atmosphere, (0–6) km, (0–11) km, and (8–16) km, respectively. We find that our biases with respect to sondes and our degrees of freedom for signal for ozone are comparable to previously published results from other IASI ozone algorithms. In addition to evaluating biases, we validate the retrieval errors by comparing predicted errors to the sample covariance matrix of the IASI observations themselves. For the predicted vs. empirical error comparison, we find that these errors are consistent and that the measurement noise and the interference of temperature and water vapour on the retrieval together mostly explain the empirically derived random errors. In general, the precision of the IASI ozone profiles is better than 20%.

scholarly journals Evaluation of MUSICA IASI tropospheric water vapour profiles using theoretical error assessments and comparisons to GRUAN Vaisala RS92 measurements

2018 ◽  
Vol 11 (9) ◽  
pp. 4981-5006 ◽  
Author(s):  
Christian Borger ◽  
Matthias Schneider ◽  
Benjamin Ertl ◽  
Frank Hase ◽  
Omaira E. García ◽  
...  
Keyword(s):  
Water Vapour ◽  
Degrees Of Freedom ◽  
Global Climate ◽  
Atmospheric Temperature ◽  
Systematic Difference ◽  
Polar Regions ◽  
Mixing Ratio ◽  
Random Errors ◽  
The Tropics ◽  
Dry Bias

Abstract. Volume mixing ratio water vapour profiles have been retrieved from IASI (Infrared Atmospheric Sounding Interferometer) spectra using the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) processor. The retrievals are done for IASI observations that coincide with Vaisala RS92 radiosonde measurements performed in the framework of the GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) in three different climate zones: the tropics (Manus Island, 2° S), mid-latitudes (Lindenberg, 52° N), and polar regions (Sodankylä, 67° N). The retrievals show good sensitivity with respect to the vertical H2O distribution between 1 km above ground and the upper troposphere. Typical DOFS (degrees of freedom for signal) values are about 5.6 for the tropics, 5.1 for summertime mid-latitudes, 3.8 for wintertime mid-latitudes, and 4.4 for summertime polar regions. The errors of the MUSICA IASI water vapour profiles have been theoretically estimated considering the contribution of many different uncertainty sources. For all three climate regions, unrecognized cirrus clouds and uncertainties in atmospheric temperature have been identified as the most important error sources and they can reach about 25 %. The MUSICA IASI water vapour profiles have been compared to 100 individual coincident GRUAN water vapour profiles. The systematic difference between the data is within 11 % below 12 km altitude; however, at higher altitudes the MUSICA IASI data show a dry bias with respect to the GRUAN data of up to 21 %. The scatter is largest close to the surface (30 %), but never exceeds 21 % above 1 km altitude. The comparison study documents that the MUSICA IASI retrieval processor provides H2O profiles that capture the large variations in H2O volume mixing ratio profiles well from 1 km above ground up to altitudes close to the tropopause. Above 5 km the observed scatter with respect to GRUAN data is in reasonable agreement with the combined MUSICA IASI and GRUAN random errors. The increased scatter at lower altitudes might be explained by surface emissivity uncertainties at the summertime continental sites of Lindenberg and Sodankylä, and the upper tropospheric dry bias might suggest deficits in correctly modelling the spectroscopic line shapes of water vapour.

scholarly journals Validation of six years of TES tropospheric ozone retrievals with ozonesonde measurements: implications for spatial patterns and temporal stability in the bias

2013 ◽  
Vol 6 (5) ◽  
pp. 1413-1423 ◽  
Author(s):  
W. W. Verstraeten ◽  
K. F. Boersma ◽  
J. Zörner ◽  
M. A. F. Allaart ◽  
K. W. Bowman ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Temporal Stability ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
Upper Troposphere ◽  
The World ◽  
The Difference ◽  
The Tropics

Abstract. In this analysis, Tropospheric Emission Spectrometer (TES) V004 nadir ozone (O3) profiles are validated with more than 4400 coinciding ozonesonde measurements taken across the world from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) during the period 2005–2010. The TES observation operator was applied to the sonde data to ensure a consistent comparison between TES and ozonesonde data, i.e. without the influence of the a priori O3 profile needed to regulate the retrieval. Generally, TES V004 O3 retrievals are biased high by 2–7 ppbv (7–15%) in the troposphere, consistent with validation results from earlier studies. Because of two degrees of freedom for signal in the troposphere, we can distinguish between upper and lower troposphere mean biases, respectively ranging from −0.4 to +13.3 ppbv for the upper troposphere and +3.9 to +6.0 ppbv for the lower troposphere. Focusing on the 464 hPa retrieval level, broadly representative of the free tropospheric O3, we find differences in the TES biases for the tropics (+3 ppbv, +7%), sub-tropics (+5 ppbv, +11%), and northern (+7 ppbv, +13%) and southern mid-latitudes (+4 ppbv, +10%). The relatively long-term record (6 yr) of TES–ozonesonde comparisons allowed us to quantify temporal variations in TES biases at 464 hPa. We find that there are no discernable biases in each of these latitudinal bands; temporal variations in the bias are typically within the uncertainty of the difference between TES and ozonesondes. Establishing these bias patterns is important in order to make meaningful use of TES O3 data in applications such as model evaluation, trend analysis, or data assimilation.

scholarly journals Characterization of ozone profiles derived from Aura TES and OMI Radiances

2012 ◽  
Vol 12 (10) ◽  
pp. 27589-27636 ◽  
Author(s):  
D. Fu ◽  
J. R. Worden ◽  
X. Liu ◽  
S. S. Kulawik ◽  
K. W. Bowman ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Surface Ozone ◽  
Lower Troposphere ◽  
Vertical Resolution ◽  
Ozone Monitoring Instrument ◽  
Near Surface ◽  
Upper Troposphere ◽  
Ozone Profile ◽  
Mean Square Difference

Abstract. We present satellite based ozone profile estimates derived by combining radiances measured at thermal infrared (TIR) wavelengths from the Aura Tropospheric Emission Spectrometer (TES) and ultraviolet (UV) wavelengths measured by the Aura Ozone Monitoring Instrument (OMI). The advantage of using these combined wavelengths and instruments for sounding ozone over either instrument alone is improved sensitivity near the surface as well as the capability to consistently resolve the lower troposphere, upper troposphere, and lower stratosphere for scenes with varying geophysical states. For example, the vertical resolution for ozone estimates from either TES or OMI vary strongly by surface albedo and temperature and typically provide 1.6 degrees-of-freedom for signal (DOFS) for TES or less than 1 DOFS for OMI in the troposphere. The combination typically provides 2 degrees-of-freedom for signal (DOFS) in the troposphere with approximately 0.4 DOFS for near surface ozone (surface to 700 hPa). We evaluate these new ozone profile estimates with ozonesonde measurements and find that calculated errors for the joint TES and OMI ozone profile estimates are in approximate agreement with actual errors as derived by the root-mean-square difference between the ozonesondes and the joint TES/OMI ozone estimates. We find that the vertical resolution of the joint TES/OMI ozone profile estimate is sufficient for quantifying variations in near-surface ozone with a precision of 26% (15.6 ppb) and a bias of 9.6% (5.7 ppb).

scholarly journals Profiles of CH<sub>4</sub>, HDO, H<sub>2</sub>O, and N<sub>2</sub>O with improved lower tropospheric vertical resolution from Aura TES radiances

2011 ◽  
Vol 4 (6) ◽  
pp. 6679-6721 ◽  
Author(s):  
J. Worden ◽  
S. Kulawik ◽  
C. Frankenberg ◽  
V. Payne ◽  
K. Bowman ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
Retrieval Algorithm ◽  
Profile Measurement ◽  
Vertical Resolution ◽  
Spectral Window ◽  
Carbon Cycles ◽  
Cloud Properties ◽  
Peak Sensitivity ◽  
Window Approach ◽  
The Tropics

Abstract. Thermal infrared (IR) radiances measured near 8 microns contain information about the vertical distribution of water vapor (H2O), one of its minor isotopologues (HDO) and methane (CH4), key gases that can be used to investigate the water and carbon cycles. Here, we show improvements in vertical resolution and reduction in uncertainties for estimates of these trace gases made from the Aura Tropospheric Emission Spectrometer (TES). The improvements are achieved by utilizing more of the inherent information available in the TES measurements. In previous versions of the TES profile retrieval algorithm, a "spectral-window" approach was used that attempted to minimize uncertainty from interfering specie. However, this approach can also reduce the vertical resolution of the retrieved species. Here we document the vertical sensitivity and error characteristics of retrievals in which H2O, HDO, CH4 and nitrous oxide (N2O) are jointly estimated (together with temperature, surface emissivity, and cloud properties) using the spectral region between 1100 cm−1 and 1330 cm−1. The TES retrieval constraints are also modified to maximize the use of this information. The H2O estimates show greater vertical resolution in the lower troposphere and boundary layer, while the new HDO/H2O estimates can now profile the HDO/H2O ratio between 925 hPa and 450 hPa in the tropics and during summertime at high latitudes. The new retrievals are now sensitive to methane in the free troposphere between 800 and 150 mb with peak sensitivity near 650 hPa. However, there is a bias in the upper troposphere of approximately 10 % that is likely related to temperature uncertainties and/or to errors in the methane spectroscopy. We discuss approaches for correcting this bias either through averaging or through correcting the estimated methane using co-estimated N2O profiles. While these new CH4, HDO/H2O, and H2O estimates are consistent with previous TES retrievals in the regions of overlap, future comparisons with independent profile measurement will be required to validate these new retrievals.

scholarly journals Characterization of ozone profiles derived from Aura TES and OMI radiances

2013 ◽  
Vol 13 (6) ◽  
pp. 3445-3462 ◽  
Author(s):  
D. Fu ◽  
J. R. Worden ◽  
X. Liu ◽  
S. S. Kulawik ◽  
K. W. Bowman ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Surface Ozone ◽  
A Priori ◽  
Lower Troposphere ◽  
Vertical Resolution ◽  
Ozone Monitoring Instrument ◽  
Near Surface ◽  
Production Code ◽  
Ozone Profile

Abstract. We present satellite based ozone profile estimates derived by combining radiances measured at thermal infrared (TIR) wavelengths from the Aura Tropospheric Emission Spectrometer (TES) and ultraviolet (UV) wavelengths measured by the Aura Ozone Monitoring Instrument (OMI). The advantage of using these combined wavelengths and instruments for sounding ozone over either instrument alone is improved sensitivity near the surface as well as the capability to consistently resolve the lower troposphere, upper troposphere, and lower stratosphere for scenes with varying geophysical states. For example, the vertical resolution of ozone estimates from either TES or OMI varies strongly by surface albedo and temperature. Typically, TES provides 1.6 degrees of freedom for signal (DOFS) and OMI provides less than 1 DOFS in the troposphere. The combination provides 2 DOFS in the troposphere with approximately 0.4 DOFS for near surface ozone (surface to 700 hPa). We evaluated these new ozone profile estimates with ozonesonde measurements and found that calculated errors for the joint TES and OMI ozone profile estimates are in reasonable agreement with actual errors as derived by the root-mean-square (RMS) difference between the ozonesondes and the joint TES/OMI ozone estimates. We also used a common a priori profile in the retrievals in order to evaluate the capability of different retrieval approaches on capturing near-surface ozone variability. We found that the vertical resolution of the joint TES/OMI ozone profile estimates shows significant improvements on quantifying variations in near-surface ozone with RMS differences of 49.9% and correlation coefficient of R = 0.58 for the TES/OMI near-surface estimates as compared to 67.2% RMS difference and R = 0.33 for TES and 115.8% RMS difference and R = 0.09 for OMI. This comparison removes the impacts of using the climatological a priori in the retrievals. However, it results in artificially large sonde/retrieval differences. The TES/OMI ozone profiles from the production code of joint retrievals will use climatological a priori and therefore will have more realistic ozone estimates than those from using a common a priori volume mixing ratio profile.

scholarly journals Global height-resolved methane retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp

2016 ◽  
Author(s):  
Richard Siddans ◽  
Diane Knappett ◽  
Alison Waterfall ◽  
Jane Hurley ◽  
Barry Latter ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Lower Troposphere ◽  
The Other ◽  
Spectral Interval ◽  
Spectral Features ◽  
Random Errors ◽  
Rutherford Appleton Laboratory ◽  
Cloud Parameters ◽  
Atmospheric Sounding ◽  
Retrieval Scheme

Abstract. This paper describes the global height-resolved methane (CH4) retrieval scheme for the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp, developed at the Rutherford Appleton Laboratory (RAL). The scheme is novel in: (a) precisely fitting measured spectra in the 7.9 micron region to allow information to be retrieved on two independent layers centred in the upper and lower troposphere and (b) making specific use of nitrous oxide (N2O) spectral features in the same spectral interval to directly retrieve effective cloud parameters to mitigate errors in retrieved methane due to residual cloud and other geophysical variables. The scheme has been applied to analyse IASI measurements between 2007 and 2015. Results are compared to model fields from the MACC greenhouse gas inversion and independent measurements from satellite (GOSAT), airborne (HIPPO) and ground (TCCON) sensors. The scheme is shown to be capable of retrieving column average methane with random errors of ~20–40 ppbv on individual soundings. Systematic differences with the other datasets are typically

Sign in / Sign up

Export Citation Format

Share Document