TOMS Data Research Articles

Sahara mineral dust measurements from TOMS: Comparison to surface observations over the Middle East for the extreme dust storm, March 14–17, 1998

A comparison of the TOMS aerosol index (AI) with both measurements of dust concentrations and synoptic data over the Middle East for the extremely heavy dust storm of March 14–17, 1998, is performed. Time series over Algeria, Libya, and Israel yield the following findings: The peak values in both surface concentrations and TOMS data suggest that AI values of 2.5 and 1.2 correspond to surface mean daily concentrations of 1900 and 1000 μg/m3 respectively. Surface concentrations and TOMS maps show that AI values of 3.0 correspond to about 4000 μg/m3. TOMS AI maximum values were found to increase from Algeria to Israel moving along with the center of the dust plume from 0.9 to 2.1 and 2.5 AI values. This seems to be in contradiction with the fact that the plume moves farther away from the major mineral dust sources over the Sahara and may be caused by either an increased vertical extension of the plume, hence increasing the TOMS AI, or due to convergence of the dust plume over the eastern Mediterranean. The size distribution, morphological, and mineralogical composition of the dust analyzed in this study, as well as other aerosol parameters, are essential for improving the remote sensing methods such as the TOMS AI algorithms. Of course, surface measurements alone do not allow the refinement of the TOMS retrievals; vertical profile dust measurements as well as other physical and optical aerosol parameters are necessary.

Characteristics of episodes with extremely low ozone values in the northern middle latitudes 1957−2000

Abstract. A number of episodes are observed when the total ozone for 2 to 3 days has fallen below 220 matm-cm in the northern mid- and polar latitudes in autumn. The occurrences of such episodes represent ozone deviations of about one-third from the pre-1976 Oct-Nov-Dec monthly mean! By using primarily quality checked Dobson data, a clear identification was made of more than three dozen short spells with extremely low ozone in the 1957–1978 period. In the following twenty-two years (1979–2000), using mainly TOMS data, one can identify ~ 46 cases with ozone values falling below 220 matm-cm for longer than 1 day, with each time over an area greater than 500,000 km2 . The Ozone Mass Deficiency (O3MD) from the pre-1976 average ozone values over the affected area was ~2.8 Mt per day, i.e. four to seven times greater than it would be, assuming only a long-term trend in the Oct-Nov-Dec period. The Extremely Low Ozone (ELO3) events on the day of their appearance over the N. Atlantic/European region contribute to the O3MD by representing 16% of the deficiency due to the Oct-Nov trend in the entire 40–65° N latitudinal belt. The O3MD of the greater pool with low ozone (here taken as <260 matm-cm) surrounding the area of the lowest events could contribute on the day of their appearance in Oct-Nov up to 60% and in December, ~30% to the deficiency due to the trend over the entire 40–65° N belt. Analysis of synoptic charts, supported by a backward trajectory on the isentropic surfaces 350 and 380 K, shows that in most of the events, subtropical air masses with low ozone content were transported from the Atlantic toward the UK, Scandinavia, and in many cases, further to the western sub-polar regions of Russia. This transport was sometimes combined with upward motions above a tropospheric anticyclone which lifted low ozone mixing ratios to higher altitudes. The ELO3 events cause a significant deficiency above the tropopause where, in general, the subtropical air is injected. In fact, the overall amount of ozone is not depleted, but redistributed on the hemispheric scale. Review of low ozone events, defined as days with negative deviations from the pre-1976 averages greater than 25% show, in general, similar origin. The seasonally averaged area with ELO3 and the associated O3MD, as well as for the cases with deviations > –25%, has increased during the 1990s, which could be an indication of stronger and/or more frequent subtropical air intrusions. Their occurrences could contribute noticeably to the ozone deficiency of the middle latitude ozone during the days of ELO3 appearances; however, their contribution to the long-term trend of the ozone seasonal decline is of the order of ~10%.Key words. Atmospheric composition and structure (middle atmosphere - composition and chemistry) Meteorology and atmospheric dynamics (middle atmosphere dynamics)

Twisting turning and pulsating of the Antarctic ozone hole, as revealed by TOMS data

Using data from TOMS!Nimbus7 and Meteor 3, the evolution of Antarctic ozone holes during the southern springs of 1992, 1993, 1994 was studied. At the South Pole, the evolution was mostly smooth, a steady decrease up to about September end and a steady recovery up to about December end. At latitudes near 65° S, the ozone levels (~220 DU) at different latitudes and longitudes showed fluctuations compatible with passing of a noncircular (oval) ! vortex boundary (two ends of a major axis of an ellipse), with a rotation period of -15 days (full rotation period ~30 days) in 1992 and ~17 days (full rotation period ~34 days) in 1994, different from the 2-3 weeks reported by earlier workers. However, the rotation was not with uniform speeds. During a full rotation, the speeds varied sometimes from almost zero (stalling) for a few days to ~20° per day during other intervals. Outside the oval boundary, often there were, depletions with spacings of a few (5-8) days, extending to lower latitudes up to ~30° S, indicating corrugations in the oval boundary, probably due to the effects of synoptic disturbances on total ozone through tropopause pressure changes and/or I ozone mini- holes caused by anticyclonic tropospheric forcing under the southern polar vortex. The shape of the ozone hole changed from elliptic to almost circular and vice versa within a few days and the area also changed by ~15-20%. Thus, the ozone hole was twisting, turning and pulsating, probably due to a varying strength of the wave number 2 component of the wind system prevailing there.

Total ozone potential vorticity and tropopause pressure : A comparative Analysis over south-east Asia

On the basis of TOMS data, a comparative analysis of total ozone. potential vorticity and tropopause pressure has been done over the area 20°- 50° N, 90° -160° E (south-east Asia) for a period October 1982 to September, 1983. The study has been done for three different latitude bands 20°-30° N, 30°-40° N and 400-50° N. High correlations have been found near the tropopause level at all seasons except in autumn.

Anisotropic reflection of UV radiation at the top of the atmosphere: Characteristics and models obtained from Meteor 3/TOMS

Reflection of solar radiation usually exhibits a strong dependence on viewing geometry relative to the Sun's position. Such a dependence needs taking into account in remote sensing studies employing satellite measurements made with scanning radiometers. While many investigations have been conducted concerning the angular variation of radiation in the total solar, visible, and IR wavelengths, no study was devoted to the UV radiation whose dependence on viewing geometry may differ from radiation in other spectral regions. On the basis of two and half years of Meteor‐3/TOMS data (from January 1992 to May 1994) the angular characteristics of UV radiation reflected at the top of the atmosphere (TOA) were studied extensively. A set of angular dependence models (ADMs) was developed for UV radiation at 340, 360, and 380 nm over 10 scene types. The results show that the angular dependence of UV‐reflected radiation is strong and rather different from that for total shortwave (SW) radiation as derived for the Earth Radiation Budget Experiment (ERBE). The largest discrepancy occurs under clear conditions over oceans for overhead Sun and large viewing zenith angles. The discrepancy in TOA mean albedos derived using the two sets of ADM can reach up to 48%. The discrepancy diminishes to about 10% for clear land scenes. Comparisons were also made for regional monthly mean TOA albedos over the whole globe derived from the ERBE SW ADM, TOMS UV ADM, and the assumption of isotropic reflection from an independent data set acquired by Nimbus 7/TOMS in January and July 1991. The differences exhibit an apparent zonal trend, large at high latitudes, moderate at midlatitudes, and small in the tropics.

Large loss of total ozone during the Arctic winter of 1999/2000

Three‐dimensional model calculations are used together with total ozone observations from the Global Ozone Monitoring Experiment (GOME) and ozone sonde measurements at Ny‐Ålesund, Spitsbergen to quantify the chemical ozone loss inside the Arctic polar vortex in winter 1999/2000. GOME shows March 2000 mean Arctic total ozone values of 365 DU, about 100 DU less than the 1980–1989 mean from TOMS data, well reproduced by the model calculations. A comparison of the modeled ozone with a passive ozone tracer and ozone sonde observations at Ny‐Ålesund shows that by the end of March 2000 about 2.5 ppmv of ozone are chemically depleted in the lower stratosphere, corresponding to more than 70% ozone loss. At the same time, the inferred loss in total ozone inside or at the edge of the polar vortex is between 90 and 140 DU. The large ongoing loss during March 2000 is likely to be due to widespread denitrification, which maintains high chlorine activation during this period.

Determination of radiative forcing of Saharan dust using combined TOMS and ERBE data

We determine the direct radiative forcing of Saharan dust aerosols by combining aerosol information derived from Nimbus‐7 TOMS with radiation measurements observed at the top of atmosphere (TOA) by NOAA‐9 ERBE made during February‐July 1985. Cloud parameters and precipitable water derived from NOAA‐9 HIRS2 were used to aid in screening for clouds and water vapor in the analyses. Our results indicate that under “cloud‐free” and “dry” conditions there is a good correlation between the ERBE TOA outgoing longwave fluxes and the TOMS aerosol index measurements over both land and ocean in areas under the influence of airborne Saharan dust. The ERBE TOA outgoing shortwave fluxes were also found to correlate well with the dust loading derived from TOMS over ocean. However, the calculated shortwave forcing of Saharan dust aerosols is very weak and noisy over land for the range of solar zenith angle viewed by the NOAA‐9 ERBE in 1985. Sensitivity factors of the TOA outgoing fluxes to changes in aerosol index were estimated using a linear regression fit to the ERBE and TOMS measurements. The ratio of the shortwave‐to‐longwave response to changes in dust loading over the ocean is found to be roughly 2 to 3 but opposite in sign. The monthly averaged “clear‐sky” TOA direct forcing of airborne Saharan dust was also calculated by multiplying these sensitivity factors by the TOMS monthly averaged “clear‐sky” aerosol index. Both the observational and theoretical analyses indicate that the underlying surface properties, dust layer height, ambient moisture content, and the presence of cloud all play important roles in determining the TOA direct radiative forcing due to mineral aerosols.

TOMS-BASED ASSESSMENTS OF TOTAL OZONE CONTENT OVER CENTRAL AND NORTHERN EUROPE

Results of time-series analysis of measurements of total ozone content (TOC) using the TOMS spectrometer for the period fall 1978 to spring 1993 are presented. TOC trend levels were ascertained for four stations in middle and high latitudes of European Russia and Norway. Emphasis is on identification of decadal and seasonal trends within an overall decline in ozone content in middle and high latitudes of both hemispheres. Trends computed using an earlier version of processing of TOMS data (version 6) are compared with data processed using the latest version 7, and differences are noted, especially during the autumn-winter period.

Total ozone decrease in the Arctic after REP events

Abstract. Eight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10-14 kHz) monitored along the Aldra (Norway) - Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55-50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger than that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry) - Meteorology and atmospheric dynamics (polar meteorology)

A stratospheric ozone trends data set for global modeling studies

A global stratospheric ozone trends data set is described, providing monthly profile trend estimates derived for the period 1979–1997. SAGE I/II profile trends are used above 20 km outside of polar regions, and results between the tropopause and 20 km are derived by differencing SAGE and TOMS column ozone trends. In polar regions trends are derived from ozone sonde data up to 27 km, using the near‐complete profile records at Syowa (69°S) and Resolute (75°N). While these polar ozonesonde trends agree well with TOMS outside of polar night, the Arctic data furthermore indicate significant ozone losses beginning in midwinter (January) that are not observable in TOMS data.

An analysis of ozonesonde data for the lower stratosphere: Recommendations for testing models

I present an analysis of ozonesonde data with a focus on using these data to evaluate stratospheric models of transport and chemistry. Ozonesondes are the only instruments that provide year‐round profiles of ozone throughout the lowermost stratosphere for middle and high latitudes of the Northern Hemisphere. I show vertical profiles and the annual cycle of ozone at selected pressure levels and stations and use TOMS data to evaluate the spatial bias of the sonde stations with respect to zonal mean values of column ozone. Between 10 and 30% of the ozone column is located between 100 hPa and the tropopause at middle and high latitudes, and this region drives much of the seasonal variation of the ozone column. The sonde data allow quantification of the buildup of ozone in the lowermost stratosphere of the Northern Hemisphere in winter and of its loss in late spring and summer. The amount of ozone between the tropopause and 100 hPA in the Northern Hemisphere decreases from 175 to 75 Tg from March to September, with the maximum rate of decrease in May to June; about half of the decrease is caused by the increase in the height of the tropopause. There is a lag of about a month in the time when ozone starts to accumulate in the lowermost stratosphere, from September near 40°N to October or November near 80°N, and a similar lag in the time when ozone starts to decrease, from February or March near 40°N to March or April near 80°N. I propose that the sonde data be used to provide a test of transport in two‐ and three‐dimensional models in addition to those provided by long‐lived tracers, such as N2O, CFCs, CO2, CH4, and their correlation patterns, and age of air. The annual variation of the ozone content of the lowermost stratosphere in the Northern Hemisphere is suggested as a particularly useful constraint on transport parameterizations. I make recommendations for the use of particular stations and provide summary statistics for ozone concentrations and for the mean tropopause height for each station.

A climatology of total ozone mapping spectrometer data using rotated principal component analysis

The spatial and temporal variability of total column ozone (Ω) obtained from the total ozone mapping spectrometer (TOMS version 7.0) during the period 1980–1992 was examined through the use of a multivariate statistical technique called rotated principal component analysis. Utilization of Kaiser's varimax orthogonal rotation led to the identification of 14, mostly contiguous subregions that together accounted for more than 70% of the total Ω variance. Each subregion displayed statistically unique Ω characteristics that were further examined through time series and spectral density analyses, revealing significant periodicities on semiannual, annual, quasi‐biennial, and longer term time frames. This analysis facilitated identification of the probable mechanisms responsible for the variability of Ω within the 14 homogeneous subregions. The mechanisms were either dynamical in nature (i.e., advection associated with baroclinic waves, the quasi‐biennial oscillation, or El Niño‐Southern Oscillation) or photochemical in nature (i.e., production of odd oxygen (O or O3) associated with the annual progression of the Sun). The analysis has also revealed that the influence of a data retrieval artifact, found in equatorial latitudes of version 6.0 of the TOMS data, has been reduced in version 7.0.

The simulation of atmospheric ozone distribution with a 2-D model and validation against LIARS and TOMS data

A two-dimensional model of radiative, dynamical and photochemical processes in the atmosphere has been developed and used for the simulation of ozone distribution. The results of numerical simulations are compared with LIARS and TOMS measurements. The comparison shows that the overall agreement between simulated and LIARS stratospheric ozone data is within 5–15% for almost all of the stratosphere except for the high latitudes of the winter hemisphere. This kind of disagreement is a common problem for all 2-D models, which cannot resonably reproduce planetary and gravity wave breaking processes over high latitudes. Validation of the simulated total ozone against TOMS data also shows a good overall agreement. The the total ozone difference between the 2-D model results and TOMS measurements is within 5–10% in both Northern and Southern hemispheres during all seasons except 40°S-60°S from June to October. In this region, the difference between simulated and TOMS total ozone is 30%.

Global structure of ozone response to solar and galactic cosmic ray influence (ground based and satellite data analysis)

A joint statistical analysis of solar proton fluxes measured by Russian polar satellites system “Meteor”, total ozone data sets for different points of ground based observations, and galactic cosmic ray fluxes (balloon long-term measurements in Russia) were used to study the magnitude and spatial structure of total ozone response (ground based and TOMS data).Yearly averaged values only were used for analysis to estimate the long-term effects in ozone response. The results of the study has revealed the negative ozone response to solar protons at high latitudes for the years of strong SPE's , which decreased to the low latitudes with zero effect at 45° N. Similar regression procedure for the lower latitudes has revealed a positive response of total ozone to the proton's forcing. Galactic cosmic rays produced a decadal cycle in total ozone with amplitude of about several DU at high latitudes with opposite phase to solar cycle. The response of total ozone to GCR influence has a negative trend of about 0.7 DU per decade at 43° N and increases to higher latitudes.

Air depression over south pole during Antarctic spring and its possible influence on ozone content in this region

Air depression during Antarctic spring, its long-term behaviour and connection with ozone content has been investigated on base of rocket data for polar regions and total ozone data sets for South pole (TOMS data) for 1979–1990. It was shown, that air pressure depression near South polar region in September in the lower stratosphere has a visible (about 5% per decade) negative trend similar to the tendency which total ozone records reveal. Rather high correlation (+0.82) between air pressure in the stratosphere and total ozone content for spring in Antarctica was found.

Ozone Trend over Taiwan from TOMS Data

Ozone column data obtained from Nimbus 7 satellite instrument, TOMS, were analyzed. Total ozone data over Taiwan starts November 1978 till May 1993. Daily observations were changed into monthly data for trend analysis. First, spectral analyses were performed to find possible atmospheric movements. Significant peaks were found at periods of 6, 12, 19, and 29 months. The first two are due to seasonal variations. The last one corresponds to the quasi-biennial oscillation (QBO) in stratosphere. It is suggested that the 19-months period is the difference of the annual and the equatorial QBD frequencies. A linear regression model (LRM) described by Yang and Tung (J. of Geophysical Res. 100, 9091, 1995) were adapted to the deseasoned ozone data. Besides the QBD, the solar flux and ENSO are known to affect the amount of ozone in the Earth atmosphere. The 30-mbar Singapore wind and F10.7-cm solar flux were chosen to represent variations of QBD and solar flux, respectively. The estimated total ozone decreasing trends due to anthropogenic activities are 0.92 + - 0.46% and 1.77 + - 0.52% per decade over Taipei and Cheng-Kung, respectively. Increase in tropospheric production of ozone in Taipei may explain the lower trend in Taipei than that in Cheng-Kung. Estimated contributions from natural variables to the total ozone variations are: 3.2% and 2.8% form QBD maximum to minimum; 2.0% and 2.3% per 100 solar units for Taipei and Cheng-Kung, respectively. Influence from ENSO seems to be insignificant. Comparison with ground total ozone stations will be discussed.

A comparison of global tropospheric teleconnections using observed satellite and general circulation model total ozone column data for 1979-91

The total ozone column is well correlated with tropospheric fields such as the heights of the upper tropospheric geopotential surfaces and thus it can provide useful information on temporal variability in the troposphere. The global availability of long period satellite measurements of the total ozone column, taken by the TOMS instruments since 1978, provides a valuable and independent data set for use in studies of seasonal and interannual climate variability. In this study, the global low-frequency seasonal teleconnections in the observed TOMS data from 1979–91 have been investigated using seasonal teleconnectivity maps and empirical orthogonal function analysis. They have also been compared with the results from a simulation made with the atmospheric GCM at Meteo-France, having prescribed observed sea surface temperatures for the same period. In the observed total ozone, strong ENSO-related wave number one longitudinal dipole patterns are seen in both the tropics and in the Southern Hemisphere extratropics. The model shows much weaker variability in total ozone yet appears to be able to capture similar teleconnection patterns in the tropics related to ENSO. In the SH extratropics, the model total ozone shows a strong wave number 3 response rather than the wave number one dipole seen in the observations. A wave number 3 response is also evident in the 200 hPa geopotential height simulated by the model and in the NCEP analysis, and is consistent with the response in a linearised barotropic model forced in the Indonesian region. The different responses in the modelled and observed total ozone, suggest that tropopause effect is not the major factor in the SH extratropics, and it is likely that horizontal ozone transport also plays a role in this region. Despite a generally poor simulation of the zonal mean total ozone, the model was able to capture the anomalous strengthening of the SH stationary waves during austral spring of 1988, related to an intense stratosphere sudden warming.

Subtropical tropopause break as a possible stratospheric source of ozone in the tropical troposphere

Abstract The understanding of the transport of trace chemical species between the stratosphere and the troposphere is necessary for global change prediction. Until recently it was believed that stratospheric inputs, through jet streaks and tropopause folding, should occur only at extratropical latitudes. A case study of a tropopause fold was reported at Pointe-a-Pitre by Gouget et al . (1996). We presently corroborate this first case study by new observations in the Indian Ocean suggesting that stratosphere-troposphere exchanges, induced by the subtropical jet, are actually occurring near the edge of the tropics. Key to these exchanges is the crucial region of the junction between the lowermost stratosphere and the tropical and extratropical tropospheres, defined by Holton (1996) as the intersection zone of the 2 PVU potential vorticity surface with the 380 K potential temperature level. In this paper, the wind and ozone climatological context is given using vertical radiosounding data from Reunion Island (France, 21 °S, 55 °E) and Irene (South Africa, 25 °S, 28 °E). A case of subtropical tropopause fold occurring between Madagascar and Reunion Islands is presented using ECMWF and TOMS data. Observations are found to be fairly accordant with a dynamical jet analysis and suggest that stratospheric air intrusions are possible during winter in the sub-tropics edges.

Comparison of total ozone measurements from a differential optical absorption filter instrument and a Dobson spectrophotometer

Measures of total ozone at Lisbon in July 1996 taken with a differential optical absorption filter instrument (UAM-DOAF) and a Dobson spectrophotometer are compared. Correlation of the UAM-DOAF measures and NOAATOVS data from April to October 1996 and NASA Earth Probe TOMS data from July to October 1996 for Madrid (40 N, 3 W) are given. Results show that the UAM-DOAF instrument can be used with approximately a 3 per cent error in estimating short-term total ozone variations.

Long‐term ozone trends derived from the 16‐year combined Nimbus 7/Meteor 3 TOMS Version 7 record

Ozone measurements from the Nimbus 7 TOMS instrument, which operated from November 1978 through early May 1993, have been extended through December 1994 using data from the TOMS instrument on‐board the Russian Meteor 3 satellite. Both TOMS data records have recently been recalibrated, and then reprocessed using the Version 7 retrieval algorithm. Long‐term trend estimates obtained from a multiple regression analysis show ozone losses in the extended data record similar to those reported in previous studies using Version 6 TOMS and SBUV data, and ground‐based Dobson data. Ozone continues to decline through the end of 1994, with the most significant ozone losses occurring in the high southern latitudes during October (−20% per decade) and in the northern mid‐ to high‐latitudes during March/April (−6 to −8% per decade). There is no significant ozone trend in the tropics. Annual‐average trends derived from the Nimbus 7 Version 7 data are 0–2.5% per decade less negative than those derived over the same time period using Version 6 data.