Nimbus-7 Total Ozone Mapping Spectrometer Research Articles

Temporal and spatial variability of total ozone column using TOMS satellite observations and comparison with measurements from the Dobson network

This article presents a detailed analysis of seasonal and interannual variability of total ozone content (TOC) at 16 different stations in Africa using Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) data for a period of 14 years (January 1979–December 1992). The analysis provides not only an estimate of the long-term annual and seasonal trends but also statistics of means and variability of ozone on temporal and spatial scales. For example, high negative deviations were observed for stations in Northern Africa in spring (March–May), with as much as –20 DU in Alexandria. A comparison of total ozone column data retrieved from the TOMS satellite with measurements obtained from the Dobson ground-based network is further presented for Cairo, Irene, Nairobi and Springbok. Estimates of the percentage seasonal difference between TOMS satellite and Dobson ground-based measurements reveal that the ground measurements were higher in magnitude at all stations with the exception of Nairobi. To verify the level of correlation between the ground-based and satellite observations, rank correlation coefficients were determined for all stations using daily and monthly observations. The results show that there is good correlation between the compared data sets, with daily coefficient of determination (r 2) values of 0.87, 0.76, 0.58 and 0.87 for Cairo, Irene, Nairobi and Springbok, respectively.

Comparative analyses of the ultraviolet-B flux over the continental United State based on the NASA total ozone mapping spectrometer data and USDA ground-based measurements

In recent years, the risk of health effects caused by the increased exposure to Ultraviolet-B (UVB) due to stratospheric ozone depletion has received wide attention. In the US, there are two ways to accurately measure the UVB. They include: 1) the National Aeronautical and Space Administration (NASA) Nimbus-7 total ozone mapping spectrometer (TOMS), and 2) the United State Department of Agriculture (USDA) ground-based network. This paper compares these two sensors' data for the ultraviolet index (UVI) nationally and regionally to support possible public health, agricultural, and ecological analyses in the future. The major findings of our study are: 1) although there are discrepancies between these two data sets, the temporal correlation coefficients can be as high as 98%. 2) Both types of data sources depict the macroscopic spatial pattern of the UVI across the continental US.indicating a strong spatial correlation; 3) The two data sources are generally consistent though the UVI of the NASA TOMS data are often about 0.13-1.05 units larger than those of the USDA ground-based measurements; and 4) Varying differences can be seen between the Midwest and two coastal regions. While the level of the UVI on the west coast has shown a decreasing trend in the past few years, its counterpart on the east coast showed an opposite trend in between 2000 and 2005. It is hard to conclude that the changes are due to variations of total ozone concentrations in this study period. The USDA ground-based measurements may be better applied for time series analysis for public health, ecological, and agricultural applications due to their ability to provide intensive calibrated point measurements.

Skin cancer incidence is highly associated with ultraviolet-B radiation history

Recently, the increased amount of ultraviolet-B (UV-B) exposure due to ozone depletion has been found to be associated with increased incidence of skin cancer across the world. The quantification of individual, regional, and historical UV exposure directly affects establishment of the association between skin cancer and UV exposure, but accurate assessment and measurement have been challenging for decades. As a sequence, cumulative studies using different metrics reported conflicting results on whether UV radiation, including sunburns, early childhood sun exposure, and chronic exposure, increases melanoma risk. This paper aims to establish the relationship between UV-B and melanoma incidence across the continental U.S. using an ecological approach that incorporate more accurate UV-B exposure measured by the National Aeronautical and Space Administration Nimbus-7 total ozone mapping spectrometer, and the United State Department of Agriculture ground-based network. Using statistical linear mixed models, we found strong positive associations between the skin cancer and the past UV exposure or the past cumulative 3-year UV exposure 3 or 4 years ago. UV has regional distributions and its regional effects on the skin cancer incidence are still significant after adjusting the effect of UV exposure. Research findings yield deepened understanding of spatiotemporal distribution of melanoma incidence rates and a greater appreciation for the complexity and heterogeneity of melanoma risk factors especially the UV-B exposure at different temporal and spatial scales.

Circumpolar transport of a volcanic cloud from Hekla (Iceland)

Hekla volcano (Iceland) erupted on 17 August 1980 and emplaced a sulfur dioxide (SO2) cloud into the north polar stratosphere at a maximum altitude of ∼15 km. The SO2 is tracked using satellite data from the ultraviolet (UV) Nimbus‐7 Total Ozone Mapping Spectrometer (N7/TOMS) and the infrared (IR) High‐resolution Infrared Radiation Sounder (HIRS/2) on the NOAA TIROS Operational Vertical Sounder (TOVS) platform. The eruption emitted ∼0.5–0.7 Tg of SO2, which later split into three distinct clouds, one of which circled the North Pole at the perimeter of an atypically persistent Arctic cyclone for six days, impacting airspace on three continents. Separate clouds drifted across eastern Russia, Alaska, and Canada. Maximum SO2 columns derived from TOMS and HIRS/2 accurately define the volcanic cloud's path and fit trajectories produced by the NOAA Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT) model, providing confidence in the model. When combined with the SO2 measurements, trajectory altitudes derived from HYSPLIT provide robust estimates of the altitudes of the SO2 clouds (8–15 km), which would be elusive using either the satellite data or the trajectory model in isolation. Near‐coincident, spectrally discrete UV and IR retrievals are compared in the volcanic cloud and indicate good agreement between TOMS and HIRS/2 SO2 columns for pixels with similar viewing geometry. Hekla eruptions, which follow a pattern of early explosive venting of volcanic gases with significant stratospheric injection, could play a role in promoting Arctic ozone loss, depending on the phase of the North Atlantic Oscillation during the eruption.

A climatology of ozone mini-holes over the northern hemisphere

A comprehensive climatology of ozone mini-hole occurrence over mid-latitudes of the northern hemisphere is constructed, based on daily measurements of total column ozone from the Nimbus-7 TOMS (total ozone mapping spectrometer) satellite, using version-7 data, over a 14-year period. An ozone mini-hole is a synoptic-scale area of strongly reduced total column ozone amount, which undergoes a cycle of growth and decay, in direct association with tropospheric weather systems. A computer-based analytical method for searching for local minima in the daily TOMS ozone fields is employed to build up a catalogue of mini-hole events, tracking location and intensity. Geographical and seasonal variations in the resulting data are summarised and possible trends over the data period are assessed. Ozone mini-hole activity exhibits a strong annual cycle, peaking in the late winter. Mini-holes are shown to be generally more frequent over the N. Atlantic/European sector than the N. Pacific/N. American sector. An alternative method of defining a threshold is also discussed in which ozone minima are viewed as anomalies from local climatological mean ozone levels. Mini-hole activity is seen to exhibit a close spatial correlation to each of the storm-track regions of the hemisphere. © 1998 Royal Meteorological Society

Wavelet analysis and visualization of the formation and evolution of low total ozone events over northern Sweden

The formation and development of abnormally low total ozone events (LOEs), which typically last an average of 3–4 days, are analyzed to determine conditions under which these events may form. Wavelet analysis is performed on 13 years of daily total column ozone (TOZ) obtained by the Nimbus‐7 Total Ozone Mapping Spectrometer each day of the record. With wavelet analysis, the contributions and relative phases of signal components may be ascertained at specific times of interest. Timescales relevant during LOEs are identified and the contributions and phase relations of all components present in the TOZ signal are compared for common patterns and features. For a location in Sweden, the formation of 96% of the 52 LOEs studied required that all components with timescales (τ) less than a maximum value (τmax) were present in their negative phases. This suggests that LOEs result from the simultaneous interaction of TOZ‐depleting processes. The number of interacting processes varies with season and location. In addition, two criteria are seen to prevail when LOEs form in this location. First, background conditions favorable for the development of an event exist; these occur when TOZ is in a spectral state where all components with Δτ1<τ<τmax are in their negative phases. Second, a process takes place that can force the remaining short‐timescale components (τ<Δτ1) into their negative phases. Processes associated with “initiating” timescales (Δτ1) of ≈ 2–6 days are found to be a key factor in the initiation of LOEs in this location. Although the background conditions are not uncommon, the likelihood that both criteria are simultaneously met is low and the occurrence of LOEs is indeed rare (averaging 4.7 events per year from 1980–1990).

Seasonal variation and trends of Toms ozone over Tibet

Using Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) data, this article discusses the seasonal variation in total ozone over the Tibetan Plateau. In addition, total ozone trends over this region are revealed by linear regression analysis. Low ozone concentrations are found over the large scale topographies of the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains. The phenomenon is the strongest over Tibet. Total ozone in Tibet is lowest in October and highest in March. However, relative to zonal mean total ozone, largest ozone deficiency over Tibet occurs in May, while smallest deficiency occurs during November–January months. The ozone deficiencies are negatively correlated to the heat flux from the surface to the air in Tibet, with correlation coefficient −0.97. The ozone trend over Tibet, deduced from TOMS 1978–1991 year‐round data, is −0.79±0.82 DU/Year (−2.7±2.8 percent/decade), with the monthly trends ranging from −0.17 DU/year (−0.6 percent/decade) to −1.79 DU/year (6.0 percent/decade).

Detection of biomass burning smoke from TOMS measurements

A 14.5 year gridded data set of tropospheric absorbing aerosol index was derived from the Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) reflectivity difference between 340 and 380 nm channels. Based upon radiative transfer calculations, the reflectivity anomaly between these two UV wavelength channels is very sensitive to smoke and soot aerosols from biomass burning and forest fires, volcanic ash clouds as well as desert mineral dust. We demonstrate the ability of the TOMS instrument to detect and track smoke and soot aerosols generated by biomass burning in South America. TOMS data can clearly distinguish between absorbing particles (smoke and dust) and non‐absorbing aerosols (clouds and haze). For South American fires, comparisons of TOMS data are consistent with the limited amount of ground‐based observations (Porto Nacional, Brazil) and show generally good agreement with other satellite imagery. TOMS data shows large‐scale transport of smoke particulates generated by the burning fires in the South America, which subsequentially advects smoke aerosols as far as the Atlantic Ocean east of Uruguay.

Intercomparison of global PAR data sets

Global data sets of surface‐incident photosynthetically active radiation (PAR, 400–700 nm) from three satellite‐based methodologies are compared with each other and with ground data. Two are based on C1 data from the International Satellite Cloud Climatology Project (ISCCP): ISCCP‐BR was produced from an existing total shortwave irradiance data set by assuming 50% PAR; ISCCP‐PL is an existing PAR‐specific data set. TOMS PAR is based on 370 nm data from the Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS). ISCCP‐BR and ISCCP‐PL are typically 12–16% and 8–12% greater than TOMS PAR, respectively. Comparison of ISCCP‐BR, ISCCP‐PL, and TOMS PAR with ground data at a mid‐latitude site for non‐winter (snow/ice‐free) months yields RMS differences of 28.1%, 13.7%, and 7.2%, and biases of +25.9%, +12.0%, and +2.8%, respectively. The comparison indicates TOMS PAR provides the most reliable estimates of PAR for snow/ice‐free, growing season months, i.e. when the energy is effective for photosynthesis. Differences among the data sets constitute a significant source of variation in results from biospheric process models that include PAR as a variable.

Satellite estimation of spectral UVB irradiance using TOMS derived total ozone and UV reflectivity

A method for satellite remote sensing of spectral UVB radiation incident at the earth's surface for snow and/or ice free areas has been developed. Measurements of total ozone and UV reflectivity from the Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) instrument have been applied to this technique. Comparison of satellite estimates with ground based measurements of spectral UVB irradiance show differences which are comparable to differences between near simultaneous measurements made with two or more ground based co‐located instruments.

Ozone depletion over Scotland as derived from Nimbus-7 TOMS measurements

Abstract The TOMS (Total Ozone Mapping Spectrometer) flown on the Nimbus-7 satellite has been measuring the total ozone concentration over the globe since November 1978. Recent investigations based on TOMS data have shown that in the latitude belt 40–70° N the spring ozone depletion rate reaches the value of —0·8 per cent per year. This paper reports trends derived from the TOMS reprocessed total ozone data for the case of Dundee (56·5°N, 3°W) from January 1979 to January 1992. The depletion rate of the mean monthly total ozone concentration over this 13-year period shows a strong variation from more than —15 per cent in December and January to about +0·5 per cent in February and June, while the overall mean is about —7 per cent.

Total ozone amount trend at St Petersburg as deduced from Nimbus-7 TOMS observations

Abstract The observations of the Total Ozone Mapping Spectrometer (TOMS) flown on the Nimbus-7 satellite have been used in order to detect the monthly trend in total ozone concentration over St Petersburg (60°N, 30°E) during the period from November 1978 to January 1992. The trend analysis suggests that the total ozone depletion over the 13-year period shows strong variations from month to month reaching —13 per cent for December but with a slightly positive trend for September.

Ozone depletion over Greece as deduced from Nimbus-7 TOMS measurements

Abstract The Total Ozone Mapping Spectrometer (TOMS) on the Nimbus-7 satellite has been measuring the total column amount of ozone over the globe for more than 13 years. Recent findings from TOMS data suggest that just north of 40° N the winter trend shows an annual ozone depletion rate of just over —0-8 per cent per year. This paper reports trends derived from the TOMS reprocessed total ozone data for the case of Athens (38° N 24° E) from January 1979 to January 1992. The total depletion over the 13 year period shows a strong seasonal variation from more than 7 per cent in winter and early spring to about 2-5 per cent in summer. These trends are twice as large as expected from models.

Nimbus-7Total Ozone Observations of Western North Pacific Tropical Cyclones

The Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) was used to map the distribution of total ozone around western North Pacific tropical cyclones from 1979 to 1982. The strong correlation between total ozone distribution and tropopause height found in the subtropical and midlatitudes made it possible for TOMS to monitor the propagation of upper-tropospheric waves and the mutual adjustment between these waves and tropical cyclones during their interaction. Changes in these total ozone patterns reflect the three-dimensional upper-tropospheric transport processes that are involved in tropical cyclone intensity and intensity and motion changes. The total ozone distributions indicate that 1) the mean upper-tropospheric circulations associated with western North Pacific and Atlantic tropical cyclones are similar; 2) more intense tropical cyclones have higher tropopauses around their centers; 3) more intense tropical cyclones have higher tropopauses on the anticyclonic-shear side of their outflow jets, which indicate that the more intense tropical cyclones have stronger outflow channels than less intense systems; 4) tropical cyclones that intensify (do not intensify) are within 10° (15°) latitude of weak (strong) upper-tropospheric troughs that are moderately rich (very rich) in total ozone; and 5) tropical cyclones turn to the left (right) when they move within approximately 15° latitude downstream of an ozone-poor (ozone-rich) upper-tropospheric ridge (trough).

Tropical Cyclone-Upper Atmospheric Interaction as Inferred from Satellite Total Ozone Observations

The Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) was used to map the distribution of total ozone in and around western Atlantic tropical cyclones from 1979 to 1982. It was found that the TOMS-observed total ozone distribution within the subtropics during the tropical cyclone season correlated well with the tropopause topography, similar to earlier middle-latitudinal observations. This relationship made it possible to use TOMS to monitor the propagation of upper-tropospheric subtropical transient waves and the mutual adjustment between the tropical cyclone and the upper-tropospheric waves during their interaction. These total ozone patterns reflected the three-dimensional upper-tropospheric transport processes that were conducive for storm intensification and weakening. It was also found from satellite observations and numerical model simulations that modification of the environmental distribution of total ozone by the tropical cyclones was primarily caused by the secondary circulation associated with the tropical cyclone's outflow jet and the intrusion of stratospheric air in the eyes of tropical cyclones.

Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex.

An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. There is tentative evidence for quasi-periodic (15 to 20 days) O3 fluctuations in the collar and for upwelling of tropospheric air in late spring. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The concentrations required to account for the observed loss of O3 are higher than those previously reported by Anderson et al. but are comparable to their recently revised values. However, the O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator. This uncertainty, together with the uncertainties associated with measurements acquired during the Airborne Antarctic Ozone Experiment, suggests that in early spring, closer to the vortex center, there may be even larger ClO concentrations than have yet been detected.

Evidence of the mid-latitude impact of Antarctic ozone depletion

THE 1987 Antarctic Airborne Ozone Expedition established that the springtime depletion of Antarctic ozone1,2 is due to photochemical destruction3 following a preconditioning phase involving heterogeneous reactions on polar stratospheric clouds4. Ozone destruction is concentrated in the cold Antarctic stratospheric vortex of winter and early spring, where these clouds occur. Nevertheless, ozone data reveal a secular decline into mid-latitudes5,6. Modelling studies6,7 suggest a 'dilution effect' whereby ozone-poor air is transported into mid-latitudes when the vortex breaks up in late spring (the 'final warming'). The extent to which the effect penetrates into middle latitudes is clouded by statistical uncertainty in trend analyses and by the difficulty of separating photochemical and dynamical effects on seasonal timescales. Here we analyse record low ozone values found over Australia and New Zealand during December 19875 following the record low Antarctic values of October 19875. In fact, there was a sudden decline of ozone amounts in mid-month; this rules out photochemical effects as a cause and allows us to investigate the underlying processes on a 'case study' basis. Using data from ozonesondes, radiosondes, the Nimbus-7 total ozone mapping spectrometer (TOMS), and meteorological analyses from the National Meteorological Center (Washington), we argue that these low values resulted from transport of ozone-poor air from higher latitudes. It therefore seems that the chemical destruction of ozone over Antarctica in early spring is having an impact on lower latitudes.