TOMS Ozone Data Research Articles

Estimation of different biologically effective irradiances at Visakhapatnam (17.7°N, 83.3°E) from standard action spectra

Measurements of solar ultraviolet radiation in the biological band (280 - 320 nm) using a ground based UV-B Photometer at VISAKHAPATNAM have been used to estimate the biological effects of the incoming radiation on various species like human, animals, plants etc. with the help of standard action spectra. A comparison is made with TOMS ozone data to find the dependence on column ozone at a subtropical Indian station Visakhapatnam (17.7°N, 83.3°E). It is found that there is no significant change in the incoming biological effective radiation in the latitude (10 - 20° North) which corresponds to very less change in the columnar ozone content for this latitude. A bilinear regression model developed for this station was used to find the RAF (Radiation Amplification Factor) which indicates the change in the biological effect with respect to the corresponding change in ozone. The values of RAF for different biological effects were evaluated and are presented in this paper. Key words: UV-B irradiance, TOMS ozone, RAF, regression model, solar zenith angle, action spectrum.

Numerical test of a simple approach for using TOMS total ozone data in hurricane environment

AbstractUsing a regime‐dependent linear regression model that maps TOMS observed total column ozone (O3) into model mean vertically‐integrated potential vorticity (MPV): O3 = α × MPV + β, where the regression constants α and β are evaluated separately for data in regions strongly and weakly influenced by deep convection/southerly advection, respectively, TOMS ozone data can readily be incorporated into a hurricane forecast model. Case‐studies of several hurricanes are conducted applying such a simple regime‐dependent linear regression model to TOMS ozone data assimilation. Improvements in the track prediction are shown. A detailed analysis of how TOMS total ozone affects the track prediction is conducted for Hurricane Erin (2001). A significant improvement in the track prediction for Hurricane Erin (2001) using TOMS ozone occurred at about 20 hours into the model forecast, when the control forecast experiences a sudden increase of track error. It is found that such an improvement in the track prediction of Hurricane Erin is mainly due to differences in the steering flows of the two forecast experiments, resulting from the presence of an upstream middle‐latitude ozone trough and a downstream low‐latitude ozone trough. An examination of the time evolution of these two troughs in both forecast experiments indicates that both troughs became stronger and moved closer to Hurricane Erin with time in the forecast experiment with the assimilation of TOMS ozone data than did those in the control forecast. Copyright © 2008 Royal Meteorological Society

Estimativa para cálculo de ozônio total usando dados de UVB E UVA do observatório espacial do sul, Brasil

A obtenção da coluna total de ozônio a partir de detectores de radiação ultravioleta (UV) como Radiômetros e Espectroradiômetros é de grande importância, visto que os medidores de ozônio como o Espectrofotômetro Brewer são muito caros e, portanto, de difícil obtenção. Este trabalho tem como objetivo encontrar modelos matemáticos que relacionem a razão entre as radiações UVB/UVA do Espectroradiômetro MS 701, dos Radiômetros UV-B MS 212 W e UV-A MS 212 A e as medidas de ozônio efetivo obtidas a partir do Espectrofotômetro Brewer MKIII #167, instalados no Observatório Espacial do Sul, no Sul do Brasil. Os períodos selecionados para análise foram o ano de 2003 para o Espectroradiômetro e o de 2005 para os Radiômetros, onde foram utilizados apenas dias sem interferências de nuvens. Os modelos matemáticos encontrados foram funções exponenciais com coeficiente de correlação R = 0,85 para a relação com o Espectroradiômetro e de R = 0,99 para a relação com os Radiômetros. Os dados de ozônio efetivo obtidos a partir dos detectores UV foram ajustados aos seus respectivos modelos e comparados com a coluna total de ozônio fornecida pelo Espectrofotômetro Brewer e pelo TOMS. A diferença média entre os valores obtidos da coluna total de ozônio do Espectroradiômetro e o Brewer foi de 0,7% e com o TOMS foi de 3,1% enquanto a comparação para a coluna total de ozônio fornecida pelos Radiômetros com o Brewer apresentou diferença média de 2% e com o TOMS de 4,3%. Estes resultados comprovam a eficiência do método utilizado e uma boa aproximação das funções encontradas.

Proxy-based reconstruction of erythemal UV doses over Estonia for 1955–2004

Abstract. A proxy-based reconstruction of the erythemally-weighted UV doses for 1955-2004 has been performed for the Tartu-Tõravere Meteorological Station (58°16' N, 26°28' E, 70 m a.s.l.) site. The pyrheliometer-measured daily sum of direct irradiance on partly cloudy and clear days, and the pyranometer-measured daily sum of global irradiance on overcast days were used as the cloudiness influence related proxies. The TOMS ozone data have been used for detecting the daily deviations from the climatic value (averaged annual cycle). In 1998–2004, the biases between the measured and reconstructed daily doses in 55.5% of the cases were within ±10% and in 83.5% of the cases within ±20%, on average. In the summer half-year these amounts were 62% and 88%, respectively. In most years the results for longer intervals did not differ significantly, if no correction was made for the daily deviations of total ozone from its climatic value. The annual and summer half-yearly erythemal doses (contributing, on average, 89% of the annual value) agreed within ±2%, except for the years after major volcanic eruptions and one extremely fine weather year (2002). Using the daily relative sunshine duration as a proxy without detailed correction for atmospheric turbidity results in biases of 2–4% in the summer half-yearly dose in the years after major volcanic eruptions and a few other years of high atmospheric turbidity. The year-to-year variations of the summer half-yearly erythemal dose in 1955–2004 were found to be within 92–111% relative to their average value. Exclusion of eight extreme years reduces this range for the remaining to 95–105.5%. Due to the quasi-periodic alternation of wet and dry periods, the interval of cloudy summers 1976–1993 regularly manifests summer half-yearly erythemal dose values lower than the 1955–2004 average. Since 1996/1997 midwinters have been darker than on average.

A Web‐based Tool for UV lrradiance Data: Predictions for European and Southeast Asian Sites

There are a range of UV models available, but one needs significant pre-existing knowledge and experience in order to be able to use them. In this article a comparatively simple Web-based model developed for the SoDa (Integration and Exploitation of Networked Solar Radiation Databases for Environment Monitoring) project is presented. This is a clear-sky model with modifications for cloud effects. To determine if the model produces realistic UV data the output is compared with 1 year sets of hourly measurements at sites in the United Kingdom and Thailand. The accuracy of the output depends on the input, but reasonable results were obtained with the use of the default database inputs and improved when pyranometer instead of modeled data provided the global radiation input needed to estimate the UV. The average modeled values of UV for the UK site were found to be within 10% of measurements. For the tropical sites in Thailand the average modeled values were within 1120% of measurements for the four sites with the use of the default SoDa database values. These results improved when pyranometer data and TOMS ozone data from 2002 replaced the standard SoDa database values, reducing the error range for all four sites to less than 15%.

Modeling the effect of ozone loss on photobleaching of chromophoric dissolved organic matter in the St. Lawrence estuary

Temporal trends in total ozone for the St. Lawrence estuary were estimated from ground‐based measurements at the NOAA/CMDL station in Caribou, Maine. Linear regression analysis showed that from 1979 to 1999 total ozone has decreased by about 3.3% per decade on an annual basis and ≤6.2% per decade on a monthly basis relative to unperturbed (pre‐CFC) levels. The influence of increased ultraviolet‐B (280–320 nm) radiation associated with ozone depletion on water column photochemical processes was evaluated by modeling the photobleaching of chromophoric dissolved organic material (CDOM). Linear regression analysis showed small (<0.5% per decade), but statistically significant upward trends in maximum noontime photobleaching rates. Most notably, positive trends in relative rates for May, June, and July, when maximum absolute rates are expected, were predicted. A global model based on TOMS ozone data revealed increases in photobleaching of ≤3% per decade at high latitudes in the Southern Hemisphere. Radiation amplification factors for increases in photochemically weighted UV (280–400 nm) in response to ozone depletion were estimated at 0.1 and 0.08 for photobleaching of CDOM absorbance at 300 and 350 nm, respectively. Application of the laboratory‐based model to conditions that more closely resembled those in situ were variable with both overestimation and underestimation of measured rates. The differences between modeled rates and observed rates under quasi‐natural conditions were as large or larger than the predicted increases due to ozone depletion. These comparisons suggest that biological activity and mixing play an important, but as yet ill‐defined, role in modifying photochemical processes.

Retrieval of ozone column from global irradiance measurements and comparison with TOMS data. A year of data in the Alps

Spectral UV global irradiance has been measured regularly during the year 2000, in the French Alps, using two UV spectroradiometers. The total ozone column amount is retrieved from the ratio of irradiances around 305 and 340 nm, using look up tables based on modeling data. During cloudless days, ozone values from direct sun observations agree to within 5 DU. These ground based values compare reasonably well (to within about 4%, or 12 DU) with TOMS ozone data; this is consistent with the uncertainty of both methods which is estimated to 5 DU for TOMS, and 5–7 DU for clear sky ground based measurements. Generally the ground based ozone values seem to be slightly higher than the TOMS ozone values. For a few cases, the difference between TOMS and ground based values, can reach 10 to 15%. Different possible explanations of the discrepancies are considered.

Evidence for an ozone hole perturbation at 30° South

A relatively strong stratospheric column ozone decrease was observed in the south of Brazil (29.5‡S) in 1993, at the end of October. This ozone decrease was observed when the normal behavior of the ozone column at low latitudes, in Brazil, reaches its yearly maximum, so that a decrease of ozone during this time period is unexpected. The local observations were made by two different measurement techniques. Two independent ground-based Brewer spectrophotometers documented strong column ozone decreases in the south of Brazil, in 1993. The vertical distribution of ozone was observed with ozone-soundings, showing a uniform ozone decrease at all heights in the stratosphere, and very low ozone in the lower stratosphere, which has been shown to be a characteristic of Antarctic ozone in Spring. TOMS ozone data, representing a third observational technique, averaged over small latitude-longitude bands, correlate very well with the local observations, which leaves no doubt that the observed ozone decreases in the south of Brazil during October 1993 were real. Also, the observed ozone decreases may be considered large, since for comparison, the local seasonal variation is at most of the order of 30 Dobson Units (DU), whereas one of the October decreases measured about 60 DU. There seems to be no physical or chemical mechanism at low latitudes, that could account for such a large and fast perturbation in the stratosphere. On the other hand, inspection of the TOMS total ozone data maps, on the days of the above observations, show a distinct link between the Antarctic ozone hole latitudes, reaching out to the north in a curved path, and touching tropical latitudes over a narrow belt. Trajectory analyses confirm that for days of low ozone in Santa Maria, Brazil, the air masses at 20 and 25 km height have an Antarctic origin.

Ozone depletion at northern and southern latitudes derived from January 1979 to December 1991 Total Ozone Mapping Spectrometer data

Long‐term ozone depletion rates (percentage change) have been computed from 13 years of Nimbus 7/Total Ozone Mapping Spectrometer (TOMS) data as a function of latitude, longitude, and month for the period January 1, 1979, to December 31, 1991. In both hemispheres the amount of ozone has decreased at latitudes above 30° by amounts that are larger than predicted by homogeneous chemistry models for the 13‐year time period. The largest rates of ozone decrease occur in the southern hemisphere during winter and spring, with partial recovery during the summer and autumn. Outside of the Antarctic ozone hole region, the 12‐year ozone depletion rates reach 8–10% per decade during the winter and spring at 55°S. Ozone depletion rates in excess of 7% per decade occur over populated regions in the southern hemisphere poleward of 45°S (southern Argentina and the tip of New Zealand) for 7 months of the year. Similar rates of decrease occur during northern winter and spring (6–8% at 55°N) over large populated regions. The enhanced zonal average ozone depletion rates at northern mid‐latitudes (40–50°N) during January, February, and March, that correspond to five geographically localized regions of high ozone depletion rates, are probably associated with long‐term dynamical or temperature changes. Only the equatorial band between ±20° shows little or no long‐term ozone change since January 1979. Ozone time series data have been examined for effect of volcanic eruptions on stratospheric ozone observed by TOMS, with only the Mount Pinatubo stratospheric aerosol injection affecting ozone amounts for a few months after the eruption in June 1991. The TOMS data show no ozone perturbation after the El Chichon eruption, or after any of the other smaller equatorial eruptions, that cannot be explained by interference effects between the annual, El Nino/Southern Oscillation, and Quasi‐Biennial Oscillation cycles. The effect of the stratospheric aerosol scattering phase function is clearly seen in the high spatial resolution TOMS ozone data after El Chichon and Mount Pinatubo. Errors caused by the short‐term presence of stratospheric aerosols in the TOMS zonally averaged ozone data are less than 1% before correction, and have no significant effect on ozone trend determination.

Trends in column ozone based on TOMS data: Dependence on month, latitude, and longitude

On the basis of the TOMS satellite column ozone data in latitudes 70°S–70°N from November 1978 to May 1990, we use a statistical model to estimate the trends in ozone as a function of latitude, longitude, and month. The trends in the TOMS ozone data are highly seasonal and dependent on location. Near the equator, the estimated monthly trends are not significantly different from zero. For high latitudes, most of the estimated monthly trends are negative. In January, February, and March, there are some positive trend estimates in the western hemisphere around latitude 60°N. The most negative trends for these 3 months also appear in the high latitudes of the northern hemisphere. Starting in June, more negative trends appear in the latitudes 50°S–70°S than the trends in the rest of the world considered. A large depletion develops during the spring time (September to November) in the southern high‐latitude region, and the area of peak ozone decline is moving eastward during the period. The largest negative trends (about −29% per decade) for the area considered in this study appear in October around the latitude 70°S and longitudes 20°W–100°W region. Since the magnitudes of the estimated trends in the southern hemisphere increase toward the pole, more negative trends occur beyond the latitude 70°S. For the northern hemisphere, the year‐round trend estimates for latitudes 30°N–70°N range from −0.96% to −7.43% per decade. In the latitudes 30°N–50°N, the winter trend estimates are more negative than those for the summer and the fall. However, this pattern did not hold for latitudes 50°N–70°N.

Total ozone measurements and stratospheric cloud detection during the AASE and the TECHNOPS Arctic Balloon Campaign

Total ozone fields over Northern Europe and Arctic regions were calculated during the winter 1989 using the TOVS/HIRS2 infra‐red radiances. During that same period ground‐based and airborne ozone and PSCs measurements were performed as part of the AASE and TECHNOPS campaigns. Comparisons have also been made with the TOMS ozone data. They show a generally good agreement, except above northernmost regions where TOMS observations seem affected by the high solar zenith angles encountered near the polar night region. This result is confirmed by the ozone measurements made from Kiruna on the 23 and 30 of January. A major type II PSC event is clearly identified in the TOVS ozone field on January 31. The cloud location is consistent with airborne lidar soundings made on the same day from DC‐8 aircraft, which measured scattering and depolarization ratios characteristic of high concentration of large ice crystals. TOVS observations show that type II PSCs covering large areas may form above the Arctic regions. However, only two major water‐ice PSCs events have been identified from January 3 to February 10. These events may not be frequent enough for the polar air to reach a completely processed state, with high ClO amounts and significant denitrification as it is observed in the Antarctic early spring.