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At least 163 records · Page 9
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NASA NTRS1988

Satellite maps of Antarctic total ozone

Satellite remote sensing techniques for ozone have made it possible to observe the detailed, daily horizontal structure of atmospheric ozone at all locations where sunlight is present. The Antarctic ozone 'hole' has been observed with the Total Ozone Mapping Spectrometer (TOMS) instrument since launch of Nimbus 7 in 1978. This feature is a continental-size ozone minimum found in the Antarctic winter and spring seasons which has generally deepened in recent years to levels in 1985 and 1987 far below the lowest values ever observed elsewhere. The minimum appears to be produced by atmospheric circulations, but the deepening almost certainly involves chemistry which is unique to cold, dark conditions.

Krueger, Arlin J.↗
NASA NTRS1988

Comparison of total ozone amounts derived from satellite and ground-based measurements

Total ozone amounts derived from the NOAA operational sounder (TOVS) are compared to measurements from Nimbus-7 SBUV and ground-based Dobson spectrophotometer observations over a seven-year period. The global trends of the data, in terms of deviations from long-term averages, derived from measurements by each satellite instrument show qualitative agreement until mid-1984 when the data diverge with the TOVS-derived data showing higher values. Additionally, more significant differences appear in both the north and south temperate zones' records. The trends derived from the satellite systems' measurements also show differences from that of the Dobson instrument measurements with the trend of the TOVS measurements showing generally better overall agreement with the Dobson data record.

Planet, Walter G.↗
NASA NTRS1994

Statistic analysis of annual total ozone extremes for the period 1964-1988

Annual extremes of total column amount of ozone (in the period 1964-1988) from a network of 29 Dobson stations have been examined using the extreme value analysis. The extremes have been calculated as the highest deviation of daily mean total ozone from its long-term monthly mean, normalized by the monthly standard deviations. The extremes have been selected from the direct-Sun total ozone observations only. The extremes resulting from abrupt changes in ozone (day to day changes greater than 20 percent) have not been considered. The ordered extremes (maxima in ascending way, minima in descending way) have been fitted to one of three forms of the Fisher-Tippet extreme value distribution by the nonlinear least square method (Levenberg-Marguard method). We have found that the ordered extremes from a majority of Dobson stations lie close to Fisher-Tippet type III. The extreme value analysis of the composite annual extremes (combined from averages of the annual extremes selected at individual stations) has shown that the composite maxima are fitted by the Fisher-Tippet type III and the composite minima by the Fisher-Tippet type I. The difference between the Fisher-Tippet types of the composite extremes seems to be related to the ozone downward trend. Extreme value prognoses for the period 1964-2014 (derived from the data taken at: all analyzed stations, the North American, and the European stations) have revealed that the prognostic extremes are close to the largest annual extremes in the period 1964-1988 and there are only small regional differences in the prognoses.

Krzyscin, Janusz W.↗
NASA NTRS2004

Antarctic Ultraviolet Radiation Climatology from Total Ozone Mapping Spectrometer Data

This project has successfully produced a climatology of local noon spectral surface irradiance covering the Antarctic continent and the Southern Ocean, the spectral interval 290-700 nm (UV-A, UV-B, and photosynthetically active radiation, PAR), and the entire sunlit part of the year for November 1979-December 1999. Total Ozone Mapping Spectrometer (TOMS) data were used to specify column ozone abundance and UV-A (360- or 380-nm) reflectivity, and passive microwave (MW) sea ice concentrations were used to specify the surface albedo over the Southern Ocean. For this latter task, sea ice concentration retrievals from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and its successor, the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) were identified with ultraviolet/visible-wavelength albedos based on an empirical TOMS/MW parameterization developed for this purpose (Lubin and Morrow, 2001). The satellite retrievals of surface albedo and UV-A reflectivity were used in a delta-Eddington radiative transfer model to estimate cloud effective optical depth. These optical depth estimates were then used along with the total ozone and surface albedo to calculate the downwelling spectral UV and PAR irradiance at the surface. These spectral irradiance maps were produced for every usable day of TOMS data between 1979-1999 (every other day early in the TOMS program, daily later on).

Lubin, Dan↗
NASA NTRS2005

Instrument Drift Uncertainties and the Long-Term TOMS/SBUV Total Ozone Record

Long-term climate records from satellites are often constructed from the measurements of a sequence of instruments launched at different times. Each of these instruments is calibrated prior to launch. After launch they are subjected to potential offsets and slow drifts in calibration. We illustrate these issues in the construction of a merged total ozone record from two TOMS and three SBUV instruments. This record extends from late 1978 through the present. The question is "How good are these records?". We have examined the uncertainty in determining the relative calibration of two instruments during an overlap period in their measurements. When comparing a TOMS instrument, such as that on Nimbus 7, with an SBUV instrument, also on Nimbus 7, we find systematic differences and random differences. We have combined these findings with estimates of individual instrument drift into a monte- carlo uncertainty propagation model. We estimate an instrument drift uncertainty of a little larger than 1 percent per decade over the 25-year history of the TOMS/SBUV measurements. We make an independent estimate of the drift uncertainty in the ground-based network of total ozone measurements and find it to be of similar, but slightly smaller magnitude. The implications of these uncertainties for trend and recovery determination will be discussed.

Solarski, Richard S.↗
NASA NTRS1981

A preliminary assessment of the problems in the use of interference filter photometers to determine total ozone

In the spring of 1979 an investigation was started involving the intercomparison of five ground based instruments designed to measure total ozone. The instruments considered include the Dobson spectrometer, the Russian M-83 ozonometer, the Brewer Ozone Spectrophotometer, the New Zealand (Canterbury) filter photometer, and the SenTran Company filter photometer. Three of these instruments use optical filters to make spectrophotometric determinations of total atmospheric ozone. The M-83 uses glass absorption filters to isolate the ultraviolet bands used. The Canterbury and the SenTran instruments use narrow-bandpass dielectric interference filters for the same purpose. Instruments employing optical filters are very appealing since they can be made small, rugged, and relatively inexpensive. However, the results of the reported investigation show that serious problems must be resolved before any filter instrument can be considered reliable enough for the conduction of long term, meaningful ozone measurements.

Gerlach, J. C.↗
NASA NTRS1979

The seasonal and interannual variability of total ozone as revealed by the BUV Nimbus-4 experiment

The BUV/Nimbus-4 total ozone data is analyzed with emphasis on the seasonal and interannual variability for the period April 1970 to April 1972. An objective analysis using a Fourier expansion shows the annual wave dominates at mid and high latitudes where the semiannual wave becomes significant in the tropics. A small interannual difference is detected and is most likely due to changes in the general circulation.

Hilsenrath, E.↗
NASA NTRS1987

Observation guidelines for a Total Ozone Mapping Spectrometer (TOMS) in geosynchronous orbit

The successful utilization of Total Ozone Mapping Spectrometer (TOMS) measurements in low Earth orbit for the analysis of rapidly changing events has led to the consideration of a TOMS in geosynchronous orbit. This orbit should allow for the selection of temporal and spatial resolutions that are specifically designed for these events, plus the flexibility of selecting different sized areas and pointing the sensor to focus on the most interesting events. Separate temporal and spatial resolution guidelines plus recommended areal coverage have been developed for tropical cyclones, jet streams, the interaction between strong convection and the environment, and the surveillance of volcanoes. It is also suggested that the most effective use of TOMS would be simultaneous flights with microwave and high spatial resolution infrared temperature profiles.

Shenk, William E.↗
NASA NTRS1993

General Design Specification Total Ozone Mapping Spectrometer

This specification establishes the general requirements for the Total Ozone Mapping Spectrometer (TOMS) and its major components, and is the main systems-engineering tool for the TOMS program. This document shall be the primary technical specification for the TOMS FM-3 and later instruments, not including ground support equipment.

Source record↗
NASA NTRS1985

An interpretation for the interannual variations of the global distribution of total ozone

The quasibiennial oscillation (QBO) and the four year oscillation (FYO) in total ozone are discussed. In order to understand these oscillations, a comprehensive view of the ozone and the stratospheric temperature is attempted. The standpoint here is to examine if these oscillations could be understood as a reflection of the general circulation changes in the stratosphere. The description of the circulation is based on the Lagrangian-mean point of view, although only a rough estimate is obtained. For the sake of simplicity, the ozone is assumed to be an inert tracer following the atmospheric motion.

Hasebe, F.↗
NASA NTRS1986

An assessment of the long-term drift in SBUV total ozone data, based on comparison with the Dobson network

Six years of total ozone data derived from the Nimbus 7 Solar Backscatter Ultraviolet (SBUV) experiment are compared with results from 41 Dobson stations to determine year-to-year changes in addition to the monthly bias change for individual stations and for the network. The SBUV measurements are found to drift against the Dobson stations with a linear trend of .38 + or - .13 percent/yr. The cause of the drift could not be separated between residual uncorrected drift in the SBUV instrument, limited sensitivity of the SBUV to increases in tropospheric ozone, and the effect of local increases in pollution level on individual Dobson stations.

Fleig, Albert J.↗
NASA NTRS1988

An assessment of the long-term drift in TOMS total ozone data, based on comparison with the Dobson network

Seven years of total ozone data derived from the TOMS instrument on Nimbus-7 are compared with results from 41 Dobson stations. In this study, a significant improvement in fit from previous studies is obtained using a model which assumes a change in the rate of drift between TOMS and Dobson around the middle of 1982. Results indicate that the TOMS measurements have drifted relative to the Dobson stations with a two-part linear trend of -0.25 + or - 0.17 percent per year during the period from launch to 6/30/82, and -0.51 + or - 0.21 percent per year during 7/1/82 - 10/31/85. The causes of this drift cannot be definitively separated between residual uncorrected drift in the TOMS instrument (a similar drift is apparent in the SBUV-Dobson comparisons), limited sensitivity of the TOMS to increases in tropospheric ozone, and the effect of local increases in pollution levels on individual Dobson stations.

Fleig, Albert J.↗
NASA NTRS1988

The QBO and interannual variation in total ozone

Garcia and Soloman (1987) have noted that the October monthly mean minimum total ozone amounts south of 30 S were modulated by a quasibiennial oscillation (QBO) signal. The precise mechanism behind this effect, however, is unclear. Is the modulation brought about by the circulation-produced QBO signal in the ozone concentration itself, or does the temperature QBO modulate the formation of polar stratospheric clouds (PSCs), leading to changes in the chemically induced Antarctic spring ozone decline rate. Or is some other phenomenon involved. To investigate the means through which the QBO effect occurs, a series of correlation studies has been made between polar ozone and QBO signal in ozone and temperature.

Lait, Leslie R.↗
NASA NTRS1994

Recalculated values of the total ozone amount over Oslo, 60 deg N, for the period 1979-1992

The total ozone amount over Oslo has been measured with the Dobson spectrophotometer No 56. The instrument was modified, calibrated, and intercompared in 1977 in Boulder. A new intercomparison was made in 1986 in Arosa. Much work has been done to make the zenith charts reliable. A new method has been introduced where one takes into account the change in the shape of the zenith chart curves which is caused by a change of the ozone profile when the ozone amount changes. According to the conclusion derived from the intercomparison in Arosa 1986, the instrument has not been stable. The R-N tables had to be altered, but not the Q-tables. We have tried to account for this change in our handling of the observation data. No statistical analyses of these data has yet been made, but the monthly averages of the raw data show a negative linear trend of about 4 percent for the whole period.

Larsen, Soren H. H.↗
NASA NTRS1994

Accuracy of total ozone retrieval from NOAA SBUV/2 measurements: Impact of instrument performance

The National Oceanic and Atmospheric Administration/National Environmental Satellite Data and Information Service (NOAA/NESDIS) has been collecting and evaluating the solar backscattered ultraviolet (SBUV/2) instrument data from NOAA 9 and NOAA 11 spacecraft since March 1985. Over 5 years (March 1985 to October 1990) of NOAA 9 (version 5.0) and over 4 years (January 1989 to June 1993) of NOAA 11 (version 6.0) reprocessed data are now available to the scientific community to study geophysical phenomena involving ozone. This paper examines the impact of the instrument performance on total ozone retrieval from the two instruments. We estimate that at the end of October 1990 the total postlaunch error for NOAA 9 due to instrument alone is -2.2%. A significant fraction of this error (-1.9%) is due to diffuser degradation which is not accounted for in the version 5 reprocessing. The estimate for NOAA 11 total postlaunch instrument error, at the end of June 1993, is -0.4%.

Ahmad, Z.↗
NASA NTRS1977

Problems in the use of interference filters for spectrophotometric determination of total ozone

An analysis of the use of ultraviolet narrow-band interference filters for total ozone determination is given with reference to the New Zealand filter spectrophotometer under the headings of filter monochromaticity, temperature dependence, orientation dependence, aging, and specification tolerances and nonuniformity. Quantitative details of each problem are given, together with the means used to overcome them in the New Zealand instrument. The tuning of the instrument's filter center wavelengths to a common set of values by tilting the filters is also described, along with a simple calibration method used to adjust and set these center wavelengths.

Basher, R. E.↗
NASA NTRS1986

Seven years of total ozone from the TOMS instrument - A report on data quality

Seven years of TOMS total ozone data are currently available. Recently a new ozone retrieval algorithm based on improved ozone absorption cross section was implemented that has introduced 6-7 percent discontinuity in the archived data sets at the end of the fifth year of instrument operation. Until all data are reprocessed with the new algorithm users can use a table of correction factors given in this paper to make the data set internally consistent. This paper also presents a comparison of TOMS results with Amundsen Scott Dobson station. Though the agrement in most years is good, in 1983-84 the Dobson station reported unusually high values of ozone while TOMS saw the very low ozone values associated with the Antarctica ozone hole.

Fleig, Albert J.↗