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NASA NTRS2009

Changes in Cloud and Aerosol Cover (1980-2006) from Reflectivity Time Series Using SeaWiFS, N7-TOMS, EP-TOMS, SBUV-2, and OMI Radiance Data

The amount of solar radiation reflected back to space or reaching the Earth's surface is primarily governed by the amount of cloud cover and, to a much lesser extent, by Rayleigh scatteri ng, aerosols, and various absorbing gases (e.g., O3, NO2, H2O). A useful measure of the effect of cloud plus aerosol cover is given by the amount that the 331 run Lambert Equivalent Reflectivity (LER) ofa scene exceeds the surfuce reflectivity for snow/ice-free scenes after Rayleigh scattering has been removed. Twenty-eight years of reflectivity data are available by overlapping data from several satellites: N7 (Nimbus 7, TOMS; 331 nm) from 1979 to 1992, SBUV-2 series (Solar Backscatter Ultraviolet, NOAA; 331 nm) 1985 to 2007, EP (Earth-Probe, TOMS; 331 nm) 1997 to 2006, SW (SeaWiFS; 412 nm) 1998 to 2006, and OMI (Ozone Measuring Instrument; 331 nm) 2004-2007. Only N7 and SW have a sufficiently long data record, Sun-synchronous orbits, and are adequately calibrated for long-term reflectivity trend estimation. Reflectivity data derived from these instruments and the SBUV-2 series are compared during the overlapping years. Key issues in determining long-term reflecti vity changes that have occurred during the N7 and SW operating periods are discussed. The largest reflectivity changes in the 412 nm SW LER and 331 nm EP LER are found to occur near the equator and are associated with a large EI Nino-Southern Oscillation event. Most other changes that have occurred are regional, such as the apparent cloud decrease over northern Europe since 1998. The fractional occurrence (fraction of days) of high reflectivity values over Hudson Bay, Canada (snow/ice and clouds) appears to have decreased when comparing reflectivity data from 1980 to 1992 to 1997-2006, suggesting shorter duration of ice in Hudson Bay since 1980.

Herman, J. R.↗

NASA NTRS2004

Highlights of the Version 8 SBUV and TOMS Datasets Released at this Symposium

Last October was the 25th anniversary of the launch of the SBUV and TOMS instruments on NASA's Nimbus-7 satellite. Total Ozone and ozone profile datasets produced by these and following instruments have produced a quarter century long record. Over time we have released several versions of these datasets to incorporate advances in UV radiative transfer, inverse modeling, and instrument characterization. In this meeting we are releasing datasets produced from the version 8 algorithms. They replace the previous versions (V6 SBUV, and V7 TOMS) released about a decade ago. About a dozen companion papers in this meeting provide details of the new algorithms and intercomparison of the new data with external data. In this paper we present key features of the new algorithm, and discuss how the new results differ from those released previously. We show that the new datasets have better internal consistency and also agree better with external datasets. A key feature of the V8 SBUV algorithm is that the climatology has no influence on inter-annual variability and trends; it only affects the mean values and, to a limited extent, the seasonal dependence. By contrast, climatology does have some influence on TOMS total O3 trends, particularly at large solar zenith angles. For this reason, and also because TOMS record has gaps, md EP/TOMS is suffering from data quality problems, we recommend using SBUV total ozone data for applications where the high spatial resolution of TOMS is not essential.

Bhartia, Pawan K.↗

NASA NTRS1991

A new self-calibration method applied to TOMS and SBUV backscattered ultraviolet data to determine long-term global ozone change

The currently archived (1989) total ozone mapping spectrometer (TOMS) and solar backscattered ultraviolet (SBUV) total ozone data (version 5) show a global average decrease of about 9.0 percent from November 1978 to November 1988. This large decrease disagrees with an approximate 3.5-percent decrease estimated from the ground-based Dobson network. The primary source of disagreement was found to arise from an overestimate of reflectivity change and its incorrect wavelengths dependence for the diffuse plate used when measuring solar irradiance. Both of these factors have led to an overestimate of the rate of atmospheric ozone depletion by SBUV and TOMS. For total ozone measured by TOMS, a means has been found to use the measured radiance-irradiance ratio from several wavelengths pairs to construct an internally self-consistent calibration. The method uses the wavelength dependence of the sensitivity to calibration errors and the requirement that albedo ratios for each wavelength pair yield the same total ozone amounts. Smaller errors in determining spacecraft attitude, synchronization problems with the photon counting electronics, and sea-glint contamination of boundary reflectivity data have been corrected or minimized. New climatological low-ozone profiles have been incorporated into the TOMS algorithm that are appropriate for Antarctic ozone hole conditions and other low ozone cases. The combined corrections have led to a new determination of the global average total ozone trend (version 6) as a 2.9 + or - 1.3 percent decrease over 11 years (October 1978 to November 1989).

Herman, J. R.↗

NASA NTRS2010

The Effect of New Ozone Cross Sections Applied to SBUV and TOMS Retrievals

The ozone cross sections as measured by Bass and Paur have been used for processing of SBUV and TOMS data since 1986. While these cross sections were a big improvement over those previously available, there were known minor problems with accuracy for wavelengths longward of 330 nm and with the temperature dependance. Today's requirements to separate stratospheric ozone from tropospheric ozone and for the derivation of minor species such as BrO and N02 place stringent new requirements on the accuracy needed. The ozone cross section measurements of Brion, Daumont, and Malicet (BDM) are being considered for use in UV-based ozone retrievals. They have much better resolution, an extended wavelength range, and a more consistent temperature dependance. Tests show that BDM retrievals exhibit lower retrieval residuals in the satellite data; i.e., they explain our measured atmospheric radiances more accurately. Total column ozone retrieved by the TOMS instruments is about 1.5% higher than before. Ozone profiles retrieved from SBUV using the new cross sections are lower in the upper stratosphere and higher in the lower stratosphere and troposphere.

McPeters, Richard D.↗

NASA NTRS1994

A new method for monitoring long term calibration of the SBUV and TOMS instruments

A new method has been developed to monitor the long-term calibration of the Solar Backscatter Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) instruments. It is based on the fact that the radiance in one channel can be expressed as a linear sum of the radiances in neighboring channels. Using simulated radiances for the SBUV and TOMS instruments, various scenarios of changes in instrument calibration are investigated. Results from sample processing of SBUV data are also presented.

Ahmad, Z.↗

NASA NTRS2003

Ozone Climatological Profiles for Version 8 TOMS and SBUV Retrievals

A new altitude dependent ozone climatology has been produced for use with the latest Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter Ultraviolet (SBUV) retrieval algorithms. The climatology consists of monthly average profiles for ten degree latitude zones covering from 0 to 60 km. The climatology was formed by combining data from SAGE II (1988 to 2000) and MLS (1991-1999) with data from balloon sondes (1988-2002). Ozone below about 20 km is based on balloons sondes, while ozone above 30 km is based on satellite measurements. The profiles join smoothly between 20 and 30 km. The ozone climatology in the southern hemisphere and tropics has been greatly enhanced in recent years by the addition of balloon sonde stations under the SHADOZ (Southern Hemisphere Additional Ozonesondes) program. A major source of error in the TOMS and SBUV retrieval of total column ozone comes from their reduced sensitivity to ozone in the lower troposphere. An accurate climatology for the retrieval a priori is important for reducing this error on the average. The new climatology follows the seasonal behavior of tropospheric ozone and reflects its hemispheric asymmetry. Comparisons of TOMS version 8 ozone with ground stations show an improvement due in part to the new climatology.

McPeters, R. D.↗

NASA NTRS1999

NASA's Experience with UV Remote Using SBUV and TOMS Instruments

This paper will discuss key features of the NASA algorithm that has been used to produce several highly popular geophysical products from the Solar Backscatter Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) series of instruments. Since these instruments have a limited number of wavelengths, many innovative algorithmic approaches have been developed over the years to derive maximum information from these sensors. We will use Global Ozone Monitoring Experiment (GOME) data to test the assumptions made in these algorithms and show what additional information is contained in the GOME hyperspectral data. At NASA we are using this information to improve the SBUV and TOMS algorithms, as well as to develop more efficient algorithms to process GOME data.

Bhartia, P. K.↗

NASA NTRS2000

The Impact of Withholding Observations from TOMS or SBUV Instruments on the GEOS Ozone Data Assimilation System

In a data assimilation system (DAS), model forecast atmospheric fields, observations and their respective statistics are combined in an attempt to produce the best estimate of these fields. Ozone observations from two instruments are assimilated in the Goddard Earth Observing System (GEOS) ozone DAS: the Total Ozone Mapping Spectrometer (TOMS) and the Solar Backscatter Ultraviolet (SBUV) instrument. The assimilated observations are complementary; TOMS provides a global daily coverage of total column ozone, without profile information, while SBUV measures ozone profiles and total column ozone at nadir only. The purpose of this paper is to examine the performance of the ozone assimilation system in the absence of observations from one of the instruments as it can happen in the event of a failure of an instrument or when there are problems with an instrument for a limited time. Our primary concern is for the performance of the GEOS ozone DAS when it is used in the operational mode to provide near real time analyzed ozone fields in support of instruments on the Terra satellite. In addition, we are planning to produce a longer term ozone record by assimilating historical data. We want to quantify the differences in the assimilated ozone fields that are caused by the changes in the TOMS or SBUV observing network. Our primary interest is in long term and large scale features visible in global statistics of analysis fields, such as differences in the zonal mean of assimilated ozone fields or comparisons with independent observations, While some drifts in assimilated fields occur immediately, after assimilating just one day of different observations, the others develop slowly over several months. Thus, we are also interested in the length of time, which is determined from time series, that is needed for significant changes to take place.

Stajner, Ovanka↗

NASA NTRS2000

Merged Long-Term Data Sets from TOMS and SBUV Total Ozone Measurements

Total ozone has been measured by a series of nadir-viewing satellite instruments. These measurements begin with the Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter UltraViolet (SBUV) instruments on Nimbus 7, launched in late 1978. The measurements have continued with the Meteor 3 TOMS, Earth Probe TOMS, and NOAA 9,11,14 SBUV/2 instruments. The problem for producing a long-term data set is establishing the relative calibration of the various instruments to better than 1%. There was a nearly two year gap between the Meteor 3 TOMS and the Earth Probe TOMS. This gap is filled by the NOAA 9 and 11 SBUV/2 instruments, but they were in drifting orbits that result in effective gaps in the record when the equator crossing time occurs at large solar zenith angle. We have used recently re-derived calibrations of the SBUV instruments using the D-pair (306/313 nm wavelengths) data at the equator. These equatorial D-pair measurements should maintain the internal calibration of each instrument better than previous approaches. We then use the comparisons between instruments during their overlap periods to establish a consistent calibration over the entire data set. The resulting merged ozone data set is independent of the ground-based Dobson/Brewer network.

Stolarski, Richard↗

NASA NTRS2004

Implications of Version 8 TOMS and SBUV Data for Long-Term Trend Analysis

Total ozone data from the Total Ozone Mapping Spectrometer (TOMS) and profile/total ozone data from the Solar Backscatter Ultraviolet (SBUV; SBW/2) series of instruments have recently been reprocessed using new retrieval algorithms (referred to as Version 8 for both) and updated calibrations. In this paper, we incorporate the Version 8 data into a TOMS/SBW merged total ozone data set and an S B W merged profile ozone data set. The Total Merged Ozone Data (Total MOD) combines data from multiple TOMS and SBW instruments to form an internally consistent global data set with virtually complete time coverage from October 1978 through December 2003. Calibration differences between instruments are accounted for using external adjustments based on instrument intercomparisons during overlap periods. Previous results showed errors due to aerosol loading and sea glint are significantly reduced in the V8 TOMS retrievals. Using SBW as a transfer standard, calibration differences between V8 Nimbus 7 and Earth Probe TOMS data are approx. 1.3%, suggesting small errors in calibration remain. We will present updated total ozone long-term trends based on the Version 8 data. The Profile Merged Ozone Data (Profile MOD) data set is constructed using data from the SBUV series of instruments. In previous versions, SAGE data were used to establish the long-term external calibration of the combined data set. The SBW Version 8 we assess the V8 profile data through comparisons with SAGE and between SBW instruments in overlap periods. We then construct a consistently-calibrated long term time series. Updated zonal mean trends as a function of altitude and season from the new profile data set will be shown, and uncertainties in determining the best long-term calibration will be discussed.

Frith, Stacey M.↗

NASA NTRS2003

TOMS and SBUV Data: Comparison to 3D Chemical-Transport Model Results

We have updated our merged ozone data (MOD) set using the TOMS data from the new version 8 algorithm. We then analyzed these data for contributions from solar cycle, volcanoes, QBO, and halogens using a standard statistical time series model. We have recently completed a hindcast run of our 3D chemical-transport model for the same years. This model uses off-line winds from the finite-volume GCM, a full stratospheric photochemistry package, and time-varying forcing due to halogens, solar uv, and volcanic aerosols. We will report on a parallel analysis of these model results using the same statistical time series technique as used for the MOD data.

Stolarski, Richard S.↗

NASA NTRS1983

Correlative studies of satellite ozone sensor measurements

Comparisons are made between total ozone measurements made by four satellite ozone sensors (TOMS, SBUV, TOVS and MFR). The comparisons were made during July 1979 when all sensors were operating simultaneously. The TOMS and SBUV sensors were observed to measure less total ozone than the MFR sensor, 10 and 15 Dobson units (DU) respectively. The MFR and TOMS sensors measured less ozone than the TOVS sensor, 19 and 28 DU, respectively. Latitudinal variability of the total ozone comparisons is discussed.

Lovill, J. E.↗

NASA NTRS2003

Validation of Envisat Ozone Data Products using Satellite and Ground Based Data

The Envisat chemistry instruments provide an opportunity to continue the ozone data sets produced by TOMS, SBUV, HALOE, and SAGE. These data sets have already been extensively validated and are assured to be of high accuracy. Continuity and consistency of data sets among the various satellite instruments as well as ground networks is essential for detecting an ozone recovery and climate change. Our objective, as part of the Envisat CaWal program, is to validate SCIAMACHY, MIPAS, and GOMOS ozone products using these heritage instruments. In addition we plan to validate SCIAMACHY Level 1 radiance using heritage satellite data and ground observations using a radiative transfer model. Ground based data included US ozonesonde profiles and a double monochromator Brewer instrument located at Goddard Space Flight Center. To date we have tested our intercomparisons algorithms using available Envisat data compared with SBW/2 and the ground based observations. We analyzed the comparisons with respect to ozone amounts and latitude and found the differences that were expected based on the initial release of Envisat data, which had known deficiencies. We will present our latest results based on the most current release of Envisat ozone data products.

Hilsenrath, E.↗

NASA NTRS2004

Ozone and Aerosol Retrieval from Backscattered Ultraviolet Radiation

In this presentation we will discuss the techniques to estimate total column ozone and aerosol absorption optical depth from the measurements of backscattered ultraviolet (buv) radiation. The total ozone algorithm has been used to create a unique record of the ozone layer, spanning more than 3 decades, from a series of instruments (BUV, SBUV, TOMS, SBUV/2) flown on NASA, NOAA, Japanese and Russian satellites. We will discuss how this algorithm can be considered a generalization of the well-known Dobson/Brewer technique that has been used to process data from ground-based instruments for many decades, and how it differs from the DOAS techniques that have been used to estimate vertical column densities of a host of trace gases from data collected by GOME and SCIAMACHY instruments. The BUV aerosol algorithm is most suitable for the detection of UV absorbing aerosols (smoke, desert dust, volcanic ash) and is the only technique that can detect aerosols embedded in clouds. This algorithm has been used to create a quarter century record of aerosol absorption optical depth using the BUV data collected by a series of TOMS instruments. We will also discuss how the data from the OM1 instrument launched on July 15,2004 will be combined with data from MODIS and CALIPSO lidar data to enhance the accuracy and information content of satellite-derived aerosol measurements. The OM1 and MODIS instruments are currently flying on EOS Aura and EOS Aqua satellites respectively, part of a constellation of satellites called the "A-train". The CALIPSO satellite is expected to join this constellation in mid 2005.

Bhartia, Pawan K.↗

NASA NTRS2004

SAO Participation in the GOME and SCIAMACHY Satellite Instrument Programs

This report summarizes the progress on our three-year program of research to refine the measurement capability for satellite-based instruments that monitor ozone and other trace species in the Earth's stratosphere and troposphere, to retrieve global distributions of these and other constituents h m the GOME and SCIAMACHY satellite instruments, and to conduct scientific studies for the ILAS instruments. This continues our involvements as a U.S. participant in GOME and SCIAMACHY since their inception, and as a member of the ILAS-II Science Team. These programs have led to the launch of the first satellite instrument specifically designed to measure height-resolved ozone, including the tropospheric component (GOME), and the development of the first satellite instrument that will measure tropospheric ozone simultaneously with NO2, CO, HCHO, N2O, H2O, and CH4 (SCIAMACHY). The GOME program now includes the GOME-2 instruments, to be launched on the Eumetsat Metop satellites, providing long-term continuity in European measurements of global ozone that complement the measurements of the TOMS, SBUV, OMI, OMPS instruments. The research primarily focuses on two areas: Data analysis, including algorithm development and validation studies that will improve the quality of retrieved data products, in support for future field campaigns (to complement in situ and airborne campaigns with satellite measurements), and scientific analyses to be interfaced to atmospheric modeling studies.

Hilsenrath, Ernest↗

NASA NTRS2012

Ozone and Aerosol Retrieval from Backscattered Ultraviolet Radiation

In this presentation we will discuss the techniques to estimate total column ozone and aerosol absorption optical depth from the measurements of back scattered ultraviolet (buv) radiation. The total ozone algorithm has been used to create a unique record of the ozone layer, spanning more than 3 decades, from a series of instruments (BUV, SBUV, TOMS, SBUV/2) flown on NASA, NOAA, Japanese and Russian satellites. We will discuss how this algorithm can be considered a generalization of the well-known Dobson/Brewer technique that has been used to process data from ground-based instruments for many decades, and how it differs from the DOAS techniques that have been used to estimate vertical column densities of a host of trace gases from data collected by GOME and SCIAMACHY instruments. The buv aerosol algorithm is most suitable for the detection of UV absorbing aerosols (smoke, desert dust, volcanic ash) and is the only technique that can detect aerosols embedded in clouds. This algorithm has been used to create a quarter century record of aerosol absorption optical depth using the buv data collected by a series of TOMS instruments. We will also discuss how the data from the OMI instrument launched on July 15, 2004 will be combined with data from MODIS and CALIPSO lidar data to enhance the accuracy and information content of satellite-derived aerosol measurements. The OMI and MODIS instruments are currently flying on EOS Aura and EOS Aqua satellites respectively, part of a constellation of satellites called the "A-train".

Bhartia, Pawan K.↗

NASA NTRS2017

Accessing Suomi NPP OMPS Products through the GES DISC Online Data Services

This presentation will provide an overview of the OMPS products available at the GES DISC archive, as well as demonstrate the various data services provided by the GES DISC. Since the TOMS, SBUV, and EOS Aura (OMI, MLS, HIRDLS) data products are also available from the GES DISC archive, these can be easily accessed and compared with the OMPS data.

OMPS↗

NASA NTRS1991

Long-term changes in the total ozone mapping spectrometer relative to world primary standard Dobson spectrometer 83

The stability of the calibration of the Nimbus 7 solar backscatter UV (SBUV) and total ozone mapping spectrometer (TOMS) instruments by comparing their ozone measurements with those made by a single, very stable Dobson instrument: the world primary standard Dobson spectrometer number 83. Measurements of ozone made with instrument 83 at Mauna Loa observatory in eight summers between 1979 and 1989 were compared with coincident TOMS ozone measurements. The comparison shows that relative to instrument 83, ozone measured by TOMS (and SBUV) was stable between 1979 and approximately 1983, had decreased by 3 percent by 1986, and had decreased by almost 7 percent by 1989. A similar time dependence is seen when data from an ensemble of 39 Dobson stations throughout the world is compared with TOMS over the period 1979-1987. The most likely reason for the relative drift is that the diffuser plate used by both SBUV and TOMS to measure solar flux has suffered an uncorrected wavelength-dependent degradation, with most of the degradation occurring after 1983. The recently released version 6 TOMS data, corrected using the internal 'pair justification' technique, show almost no drift relative to Dobson instrument 83. Accurate measurements of long-term global ozone change will require a coherent system incorporating both ground-based and satellite-based ozone measurements.

Mcpeters, Richard D.↗