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1.
The ozone content of the free troposphere over Athens-Greece (37,58°N, 23,44°E), during the winter-spring period is examined based on observations obtained from the ozonesonde ascents from 1994 until 1998. Variations of tropospheric ozone are correlated with the corresponding Total Ozone Content (TOC) and other meteorological parameters, like tropopause temperature. Additionally TOC values as derived from ozonesounding profiles, Dobson #118 spectrophotometer and TOMS observations are cross correlated  相似文献   

2.
The Dobson ozone spectrometer has been used for studies of the ozone layer for about 60 years. It remains indispensable for assessing the accuracy of satellite-borne instruments. The steps which led to the present understanding of global ozone distribution and variations are reviewed.  相似文献   

3.
The general behavior of total ozone by season and latitude was known before 1930 through the pioneering observations by G. M. B. Dobson. The ozone record at Oxford and other European stations was dominated by an annual cycle and by irregular short term fluctuations. The amplitude and phase of the annual cycle were determined at representative latitudes in both hemispheres. However, the short term variations appeared to be of meteorological origin, although the specific cause could not be identified. Data from the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus 7 spacecraft, with global coverage at an average spatial resolution of 66 km, can now be used to completely map the total ozone field. These maps demonstrate that troughs and ridges in the upper troposphere are responsible for the large, short term ozone variations found at middle latitudes, while in the troplcs, the steady, low ozone levels show broad scale structure associated with the Hadley circulation.  相似文献   

4.
A tentative comparison is made between the various instruments operated at Gap and at the Observatoire de Haute-Provence to measure the ozone vertical distribution up to 25 km during the Intercomparison Ozone Campaign. This includes comparison of the three ozonosondes carried on the same payload during the stratospheric open air balloon flights on 19 June and 25/26 June 1981, comparison between Brewer Mast sondes and electrochemical concentration cells on 19 and 26 June. A specific comparison has been made between a ground-based lidar and ECC sondes launched at the same location on 20/21 June 1981. Also compared are the ozone distributions as monitored between 12 June and 20 June 1981 by two ground-based instruments : lidar (active sounding) or Dobson spectrometer using the Umkehr method. Analysis of the various data set are performed in terms of relative variations observed and potential causes of discrepancies.  相似文献   

5.
A scanning filter photometer using narrow band interference filters for ozone solar absorption studies was installed on O.H.P. Mt Chiran for the initial part of the intercomparison campaign. The total ozone data obtained agree to within 2% with the Dobson spectrophotometer at the same site. A sample of the data obtained on one of the intercomparison days is presented.  相似文献   

6.
This study reports observations of the total ozone content (TOC), made by both Dobson spectrophotometer at Athens Greece (39°N, 24°E) and TOMS for the time period 1979–1997. The final purpose is to examine the total ozone content by means of Fourier analysis, paying special attention to the possible difference in the atmospheric properties between TOC minima and maxima.  相似文献   

7.
A GSFC Super Loki optical ozonesonde instrument was flown as part of the ozone sensor intercomparison balloon campaign at Gap, France, in June 1981. A primary objective was to confirm biases between external absorption techniques, such as the GSFC sonde, and in situ techniques, which include ECC, Mast-Brewer, and DASIBI sondes. Ozone distributions were obtained with the GSFC sonde on three of the four ascent-descent legs of the first flight on 19 June. Ozone densities were measured redundantly over altitudes from 22 to 32 km using filters centered at 303 and 300 nm. The three profiles obtained by averaging the data from the two channels are in close agreement with an average S.E. of 1.4%. However, small but consistent differences were found between the ozone densities measured at the two wavelengths. The average difference is 5% using Vigroux cross sections and 4% using preliminary Bass cross sections. The integral ozone amount above the first ceiling altitude of 32.85 km was determined by the Langley plot method to be 45 D.U. The total ozone derived by integrating the optical ozonesonde and ECC profiles is within 2% of the Chiran Dobson Spectrophotometer observation based on a pre-campaign calibration but is 9% greater than the amount derived using a post-campaign calibration.  相似文献   

8.
Observational evidence and theoretical predictions of the response of ozone to solar variations are reviewed. Short-term solar proton effects, possible effects of galactic cosmic rays modulated by the Sun, and the effects of 27-day solar rotation and 11-year solar cycle variations are discussed. Solar proton effects on HO x chemistry in the mesosphere and NO x chemistry in the stratosphere with resulting catalytic destruction of O3 help validate present day photochemical models. If there is an 11-year solar cycle variation in global ozone, the large dynamical effects at individual locations and the lack of good global coverage of ground based and in situ measurements can disguise it. Recently, with the global coverage of satellites, it has become possible to accurately determine global mean ozone. It has been found that variations in global mean ozone filtered for seasonal variations are highly correlated with variations of the 10.7 cm solar activity index and that global mean ozone responds rapidly to solar activity index variations. Photochemical models indicate that the observed 3% variations in global mean ozone over the solar cycle can be accounted for by solar UV variations which are not inconsistent with recent solar measurements.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.  相似文献   

9.
A critical study of distribution of ozone with altitude of about 91 Km and above has been made and following important results are obtained:(i) An empirical equation is fitted theoretically between the variation of ozone concentration and altitude at a definite time.(ii) The rate of change of O3 concentration with respect to altitude is directly proportional to the O3 concentration at that altitude.(iii) From analysis it is shown that ozone concentration decreases with the increase of altitude.  相似文献   

10.
The Nimbus 7 Total Ozone Mapping Spectrometer data over Europe have been specially processed for the 2 days of the ozone sensor intercomparison balloon campaign in June 1981 at Gap, France. The 19 June TOMS map shows an elongated ozone maximum (~ 400 D.U.)extending in a NW-SE direction across central Europe and an ozone minimum (300 D.U.) in the central Atlantic. This pattern produces a 12 D.U. decrease along the balloon trajectory from the first ascent to the second descent. On 26 June a much smaller ozone maximum (400 D.U.) is centered in northern France with its main axis running in a SW-NE direction. The total ozone contours tend to lie parallel to the balloon trajectory so that the total ozone during the flight is nearly constant.  相似文献   

11.
To date, ozone has only been identified in the atmospheres of Earth and Mars. This study reports the first detection of ozone in the atmosphere of Venus by the SPICAV ultraviolet instrument onboard the Venus Express spacecraft. Venusian ozone is characterized by a vertically confined and horizontally variable layer residing in the thermosphere at a mean altitude of 100 km, with local concentrations of the order of 107–108 molecules cm−3. The observed ozone concentrations are consistent with values expected for a chlorine-catalyzed destruction scheme, indicating that the key chemical reactions operating in Earth’s upper stratosphere may also operate on Venus.  相似文献   

12.
A 3-D Atmospheric Chemical Transport model has been developed and used to simulate the present-day ozone distributions in the troposphere and stratosphere. A 5-year-long steady-state model run using 1995 boundary conditions and circulation fields derived from the 24-layer University of Illinois at Urban a-Champaign (UIUC) Atmospheric General Circulation model has been carried out. The simulated distribution of ozone is compared with available observations made by the HALOE, CLAES and MLS instruments onboard the LIARS satellite. The comparison is carried out for the monthly zonal-mean climatology of the ozone distribution. The correlations between the monthly zonal-mean ozone derived from the simulated and measured data are calculated. The results of this comparison show reasonable agreement (within 30%) of the simulated and measured monthly zonal-mean ozone distributions, although the location of the simulated maximum in the ozone distribution is generally lower by about 2–3 km than shown by the satellite data. The model overestimates the ozone mixing ratio in the lower stratosphere and slightly underestimates it in the upper stratosphere. A better overall agreement was found between the simulated ozone and the ozone measured by HALOE than by CLAES and MLS.  相似文献   

13.
A critical study on different ozone depletion and formation processes has been made and following important results are obtained:(i) From analysis it is shown that O3 concentration will decrease very minutely with time for normal atmosphere when [O], [O2] and UV-radiation remain constant. (ii) An empirical equation is established theoretically between the variation of ozone concentration and time. (iii) Special ozone depletion processes are responsible for the dramatic decrease of O3-concentration at Antarctica.  相似文献   

14.
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%.  相似文献   

15.
The fluctuation and the periodicities of the total ozone layer for the period 1957–1990 is studied. Monthly total ozone data from 32 ground based stations have been analysed. It is shown that the maxima and the minima of the monthly values of total ozone for each year and for the whole period in question do not necessarily occur in March or in April and in September or October but range from March till July and from September till December respectively. Periodicities of 3, 4 and 6 months have been revealed. Finally the maxima and the minima of the total ozone data were examined. The variation of the whole phenomenon is analytically expressed with the help of an algebraic formula and can represent the observed monthly ozone values with an accuracy of 97%.  相似文献   

16.
Ozone vertical profiles have been obtained above the “Observatoire de Haute-Provence” from 9 to 19 June 1981, with both conventional and short Umkehr methods: the mesospheric and stratospheric ozone variability has been found to be very small while the ozone variability was large in the troposphere and maximum at the tropopause level.  相似文献   

17.
The ozone height profile in the Arctic, at the end of the winter, has been measured up to an altitude of 100 km using a combined solar occultation and 1.27 μ oxygen emission technique. The typical two layer structure has been observed with a high altitude minimum near 80 km and a maximum at 86 km. The measured concentration in this ozone bulge was 5.1 × 107cm?3, typical of that measured at 52°N for the summer months. It is suggested that this reduced ozone concentration may have been associated with a stratospheric warming event that was in progress at the time of the measurement.  相似文献   

18.
In order to point out and study transports of ozone rich air masses in the lower troposphere from the stratosphere/upper troposphere, continuous measurements of several parameters have been undertaken at Mt. Cimone during the European Community VOTALP project (Vertical Ozone Transport in the Alps). Several high values of surface ozone concentration due to vertical stratospheric-tropospheric exchanges have been recorded in the four mountain peak stations involved in this project (Jungfraujoch, Sonnblick, Zugspitze and Mt. Cimone) in 1996–1997. This paper presents and analyses data concerning the Mt. Cimone ground-based station, which is the highest peak of the Italian Northern Apennines and the most representative WMO-GAW site in Italy. Episodes of vertical exchange in the lower stratosphere, as tropopause folding, or in the upper troposphere, as down draft transport, have been registered at Mt. Cimone since March 1996 and subsequently studied. In fact, the comparison between the behaviours of different background trace gases at a mountain baseline station, the weather situations and the backward trajectory analyses can bring to light these events and be very useful for a better knowledge of transport phenomena. Correlation between high level of ozone concentration, chemical and meteorological parameters and three-dimensional backward trajectories relative to two particular events are herein presented.  相似文献   

19.
The present paper presents some of the results from the EU-funded Photochemical Activity and solar Ultraviolet Radiation (PAUR) and Photochemical Activity and solar Ultraviolet Radiation Modulation Factors (PAUR II) projects that are relevant to the photochemistry of the Eastern Mediterranean under variable conditions. Compared to S-SW flows, northern flows result in higher ozone values above the PBL. Usually during N flow the aerosol optical depth is also lower, thus resulting in higher NO2 photodissociation rates. In one case of northern flow, the Etesian synoptic regime, N-NE flows are associated with high wind speeds and result to even lower aerosol optical depth. S-SW flow during springtime in some cases brings air loaded with Saharan dust particles over the region that is poor in tropospheric ozone and precursors. Often, these cases are associated with southern stratospheric circulation, resulting in reduced total ozone amounts and hence increased ozone photolysis rates, whereas the dust load reduces nitrogen dioxide photolysis rates. Results are presented from a spectral radiation model, which simulates the spectral UV radiation during some of the above cases. Measurement results from the Athens basin and rural Aegean sites are presented, that compare the ozone levels between normal N flow conditions and Etesian flow.  相似文献   

20.
Insight into the causes of the annual and semi-annual ozone oscillations may be gained from the analysis of photochemical model behavior. In this paper, the monthly variations of the ozone mixing ratio computed by the two-dimensional photochemical model of Garcia and Solomon (1983, J. geophys. Res. 88, 1379) are Fourier-analyzed and compared with SBUV observations of ozone mixing ratio. Remarkably good qualitative agreement between the model calculations and the observations is found. Analysis of computed transport and chemical production and destruction rates reveals the causes of the modelled seasonal ozone variations.

It will be shown that at high latitudes and low altitudes, modelled ozone abundances increase in the winter due to transport and decrease in the summer due to chemical destruction. In the middle stratosphere, the calculated annual ozone variation is largely due to the annual variation in the odd-oxygen production rate, and in the upper stratosphere, the computed annual ozone variation is caused by the large calculated annual oscillation in temperature. Comparison between the model and observations suggests that the equatorial semi-annual oscillation above 10 mb is caused mainly by the semi-annual temperature and wind oscillation (SAO). Below 10 mb the computed equatorial ozone variation is caused by the increased rates of odd-oxygen production associated with the semi-annual zenith crossings of the Sun. Finally, the calculated polar semi-annual ozone oscillations are found to be caused by modulation of the radiatively driven middle-stratospheric ozone variation by temperature dependent chemical destruction processes.  相似文献   


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