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Fleig, A. J.

Publications and source records attributed to Fleig, A. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Backscattered ultraviolet measurements of ozone 1970-2000 - An overview

The history of the Backscattered Ultraviolet Experiment (BUV) is recounted and related future efforts are discussed. Satellite measurement of backscattered UV radiation will be the major source of long-term global information about total ozone and ozone profiles for the rest of this century. These measurements started with the BUV experiment flown on Nimbus 4 from 1970 to 1977 and are presently being continued with the Solar and Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) launched on Nimbus 7 in 1978. NOAA's improved version (SBUV/2) is to fly until sometime in the 1990s and NASA plans to fly an SBUV/2 on the Upper Atmosphere Research Satellite in 1989. Differences between these instruments and in the algorithms for deriving ozone amounts from these data sets are discussed.

Fleig, A. J.↗
NASA NTRS1985

Standard profiles of ozone from ground to 60 km obtained by combining satellite and ground based measurements

A study is reported based on four years of SBUV data and five years of published ozonesonde data. The Solar Backscatter Ultraviolet Experiment (SBUV), has been operating continuously since November 1978, providing some 1000 profiles per day. The data are of excellent quality from about 50 km down to the tropopause. By combining the satellite-derived data with ozonesonde data, a data base of standard ozone profiles and variance/covariance matrices has been developed, defining the observed variation of the atmospheric ozone around the mean profiles. Highlights of the data base are presented along with parameters of an analytical fit that describes the essential features of the data set. Although the data base was created specifically for use as a priori profiles for SBUV and Umkehr retrievals, it should be useful in other remote sensing applications and in modeling the UV radiation fields in the stratosphere. Another suggested application is in estimating ozone above the peak altitude of the ozone balloons.

Bhartia, P. K.↗
NASA NTRS1985

An evaluation of the performance of Umkehr stations by Solar Backscattered Ultraviolet (SBUV) experiment

Until recently, Umkehr data taken by 20 Dobson stations around the world have been the principal source of information about the behavior of upper stratospheric ozone. Umkehr results are used also for detecting drifts in satellite instruments and for determining intersatellite biases. However, a systematic evaluation of the quality of Umkehr data taken by the various stations has been lacking. Five years of ozone profile data from the Solar Backscattered Ultraviolet (SBUV) have been used to examine and intercompare the quality of Umkehr stations, and to assess the degradation of their performance after the El Chichon volcano eruption in southern Mexico. In contrast to Umkehr, the SBUV ozone measurments in layers 7 through 9 (1-8 mb) were unaffected by the massive amounts of dust and gases ejected by El Chichon.

Bhartia, P. K.↗
NASA NTRS1985

Intercomparison of satellite ozone profile measurements

Ozone profile data are intercompared with those from the LIMS and SBUV flown on Nimbus 7, SAGE flown on Atmospheric Explorer Mission 2, and the Ultraviolet and Infrared Spectrometers flown on the SME. Ozone data were derived from the measurements with independently derived processing algorithms. The data cover different time periods and have different spatial and temporal resolutions. The similarities and differences between the individual data sets are determined with effort focused on directly comparing the spacecraft data sets in the form of individual profiles, zonal mean profiles and global analyses. Comparisons with ground data from balloons and Umkehr stations are made.

Fleig, A. J.↗
NASA NTRS1984

Intercomparison of NIMBUS 7 solar backscattered ultraviolet ozone profiles with rocket, balloon, and Umkehr profiles

A global ozone data set covering the two years from November 1978 until October 1980, with an average of 1200 profiles per day, has been produced and archived from the solar backscattered ultraviolet (SBUV) instrument flown on the NIMBUS 7 spacecraft. The SBUV ozone profiles are compared with measurements from chemical and optical sensors launched on balloons and rockets and with ozone profiles obtained from the ground-based Dobson spectrophotometers using the Umkehr method. The biases between the SBUV results and the balloon and Umkehr results are generally less than 10 percent. These biases are functions of layer height and latitude and are believed to be largely due to inconsistencies in the ozone absorption cross sections used for the various measurement systems. The precision of the SBUV measurements is found to be better than 8 percent for pressures between 1 and 64 mbar and better than 15 percent from 64 to 253 mbar.

Bhartia, P. K.↗
NASA NTRS1984

Intercomparison of the Nimbus 7 SBUV/TOMS total ozone data sets with Dobson and M83 results

Two years of SBUV/TOMS (Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer) data spanning the period November 1978 to October 1980 have been processed and compared with ground-based ozone measurements made at 62 Dobson spectrophotometer and 18 M83 filter photometer ozone stations. Results show that the satellite ozone values are consistently smaller than those measured by the stations; most of this difference is probably due to an error in the currently accepted ozone absorption cross sections at ultraviolet wavelengths. Dobson-derived ozone amounts agree extremely well with those derived from each of the satellite instruments. Long-term stability of the ozone derived by the two instruments is expected to be better than 0.5 percent per year.

Bhartia, P. K.↗
NASA NTRS1984

User's guide for SBUV/TOMS ozone derivative products

A series of products are available derived from the total-ozone and ozone vertical profile results for the Solar Backscattered Ultraviolet/Total-Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus-7 operation. Products available are (1) orbital height-latitude cross sections of the SBUV profile data, (2) daily global total ozone contours in polar coordinates, (3) daily averages of total ozone in global 5x5 degree latitude-longitude grid, (4) daily, monthly and quarterly averages of total ozone and profile data in 10 degree latitude zones, (5) tabular presentation of zonal means, (6) daily global total ozone and profile contours in polar coordinates. The ""Derivative Products User's Guide'' describes each of these products in detail, including their derivation and presentation format. Information is provided on how to order the tapes and microfilm from the National Space Science Data Center.

Fleig, A. J.↗
NASA NTRS1983

Standard ozone profiles from balloon and satellite data sets

Standard profiles based on upper level averaged profiles from BUV and lower level averaged profiles from balloon measurements are presented in a parametric representation as a function of time of year and latitude. The representation is a simple 4-parameter function representing the ozone amount (m-atm-cm) in each of 12 atmospheric layers defined following the standard Umkehr convention. The same parameterization is applied to the Nimbus-7 SBUV data and is compared to the BUV/balloon parameterization. The ozone variance unaccounted for by the representation is presented and discussed. The season-latitude representation reduces considerably the ozone variance at all levels and explains much of the correlation between layers. This simple representation and corresponding covariance matrix have been used as a priori information in the ozone vertical profile inversion of the Nimbus-7 SBUV experimental measurements.

Klenk, K. F.↗
NASA NTRS1983

User's guide for the Solar Backscattered Ultraviolet (SBUV) and the Total Ozone Mapping Spectrometer (TOMS) RUT-S and RUT-T data sets: October 31, 1978 to November 1, 1980

Raw data from the Solar Backscattered Ultrviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus 7 operation are available on computer tape. These data are contained on two separate sets of RUTs (Raw Units Tapes) for SBUV and TOMS, labelled RUT-S and RUT-T respectively. The RUT-S and RUT-T tapes contain uncalibrated radiance and irradiance data, housekeeping data, wavelength and electronic calibration data, instrument field-of-view location and solar ephemeris information. These tapes also contain colocated cloud, terrain pressure and snow/ice thickness data, each derived from an independent source. The "RUT User's Guide" describes the SBUV and TOMS experiments, the instrument calibration and performance, operating schedules, and data coverage, and provides an assessment of RUT-S and -T data quality. It also provides detailed information on the data available on the computer tapes.

Fleig, A. J.↗
NASA NTRS1983

Vertical ozone profile determination from Nimbus-7 SBUV measurements

An inversion algorithm is presented, which is used to process Nimbus-7 solar backscattered UV (SBUV) data collected between November 1978 and October 1980. The SBUV experiment utilizes a double monochromator in the nadir position which measures the backscattered solar radiation in twelve 1-nm bands; a separate photometer measures the radiance at 343.0 nm in the field of view coincident with the monochromator. The primary output of the inversion is the total ozone content in umkehr layers in units of m atm cm. In addition, the diagonal elements of the covariance matrix are reported; they represent the uncertainty in the derived ozone content in each layer. The solution covariance is noted to be independent of the measurements.

Klenk, K. F.↗
NASA NTRS1983

An intercomparison of ozone profile measurements from LIMS, SAGE, and SBUV

Ozone profile measurements by the Limb IR Monitor of Stratosphere (LIMS) and the Solar Backscatter UV (SBUV) aboard the Nimbus satellite, and the Stratospheric Aerosol and Gas Experiment (SAGE) aboard the AEM-2 satellite are intercompared in an effort to assess the quality of satellite ozone retrieval techniques. Good correlation between LIMS and SBUV observations is noted in the ozone layer bounded by pressures of 31.2-15.6 mb; absolute differences are generally less than 10 percent, with similar zonal variations. Above 35 km SAGE values are systematically larger than SBUV or LIMS. The differences generally increase with height and are largest in the tropics. Finally, excellent agreement is noted to exist among the three data sets between 10 and 35 km of altitude with respect to the latitude dependence of the ozone profiles.

Fleig, A. J.↗
NASA NTRS1983

Nimbus-7 total ozone algorithm

The total ozone algorithm used for the processing of Nimbus-4 BUV measurements is modified to account for off-nadir viewing of the Total Ozone Mapping Spectrometer onboard Nimbus-7 satellite. TOMS is a cross-track scanning instrument with a 50 x 50-km field of view, increasing to 150 x 150 km at the extreme off-nadir angle of 51 deg and six spectral bands in the 310-380-nm region. Consideration is given to the determination of the pressure at the reflecting surface and profile selection scheme at very high solar zenith angles. The algorithm is also applicable to the Solar Backscattered UV Experiment aboard the same satellite. The modifications provide for a better cloud height, snow correction, and improved retrievals near the terminator.

Bhartia, P. K.↗
NASA NTRS1983

Observation of El Chichon volcanic aerosols by the solar backscattered ultraviolet (SBUV) experiment

The Solar Backscatter Ultraviolet Experiment (SBUV) aboard the Nimbus-7 satellite identified large amounts of SO2 in the tropical stratosphere on April 15, 1982, 11 days after major eruption of the El Chichon volcano in southern Mexico. It is shown in the present study that the backscattered ultraviolet radiances measured by the SBUV experiment have been strongly affected by the presence of stratospheric volcanic cloud from the El Chichon eruptions. Both SO2 and aerosol amounts present in the volcanic cloud have been mapped on the basis of an analysis of the radiances measured by the SBUV and TOMS (Total Ozone Mapping Spectrometer) experiments. It is estimated that a volcanic cloud of optical depths as small as 0.03 can be detected using SBUV, provided the cloud reaches the middle atmosphere. Lower-altitude clouds have progressively smaller effects on the radiances as well as on the ozone profile derived from them and are therefore harder to detect.

Bhartia, P. K.↗
NASA NTRS1982

Ozone climatology series. Volume 1: Atlas of total ozone, April 1970 - December 1976

Contours and gridded values are given for seven years of monthly mean total ozone data derived from observations with the Backscattered Ultraviolet instrument on Nimbus-4 for the Northern and Southern Hemispheres. The instrument, algorithm, uncertainties in derived ozone and systematic changes in the bias with respect to the international groundbased ozone network of Dobson instruments, are discussed.

Heath, D. F.↗
NASA NTRS1982

User's guide for the Solar Backscattered Ultraviolet (SBUV) instrument first year ozone-S data set

Total-ozone and ozone vertical profile results for Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus 7 operation from November 1978 to November 1979 are available. The algorithm used have been thoroughly tested, the instrument performance has been examined in details, and the ozone results have been compared with Dobson, Umkehr, balloon, and rocket observations. The accuracy and precision of the satellite ozone data are good to at least within the ability of the ground truth to check and are self-consistent to within the specifications of the instrument. The 'SBUV User's Guide' describes the SBUV experiment and algorithms used. Detailed information on the data available on computer tape is provided including how to order tapes from the National Space Science Data Center.

Fleig, A. J.↗
NASA NTRS1982

Total ozone variations 1970-74 using Backscattered Ultraviolet /BUV/ and ground-based observations

The most long-lived satellite set of ozone observations, to date, is that derived from the Backscatter Ultraviolet (BUV) ozone sensor on Nimbus 4 and extends from April 1970 through 1976. Unfortunately, this experiment suffered spacecraft power limitations which limited the spatial and temporal coverage and also appears to have suffered from long-term drifts which may be associated with changes in the instrument characteristics or the incident solar flux. Techniques have been developed to account for these problems, and this paper presents results of the BUV total ozone variations and compares them with those from ground-based observations, specifically the computations of Angell and Korshover (1978). After adjustments for the spatial gaps and comparison with concurrent Dobson ground-based observations, no significant trend was found in the BUV data over the years 1970-74. This finding is in contrast to a general decrease of about 2% during the same period appearing in the data of Angell and Korshover. The difference in these results is discussed in terms of the geographic sampling and the methods of hemispheric integration.

Miller, A. J.↗
NASA NTRS1981

Characteristics of space and ground based total ozone observing systems investigated by intercomparison of Nimbus 4 Backscattered Ultraviolet /BUV/ data with Dobson and M-83 results

The Nimbus 4 Backscattered Ultraviolet (BUV) experiment data has been reprocessed to provide a near global data set covering the seven years from 1970 to 1977. The data set is the result of a three year effort by the Ozone Processing Team which included review and correction of the spacecraft ephemeris, instrument calibration, and processing algorithms. The accuracy of the resulting total ozone determinations compares well with that of ground based data. An important application of the global BUV data set is to use it in determining long term trends in global total ozone. However, in order to identify long term trends in ozone, it is necessary to eliminate first long-term drift in the instrument calibration. A follow on experiment, the Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer, (SBUV/TOMS), was flown on Nimbus 7 launched in October 1978. The SBUV provides information about both total ozone and vertical ozone profiles for a 200 km square field of view.

Fleig, A. J.↗