Ozone Climatology Research Articles

Ozone climatology at Natal, Brazil, from in situ ozonesonde data

Results are presented from analysis of a large ozone profile data set obtained from balloon ozonesonde soundings made at Natal, Brazil (6°S, 35°W) during the last 10 years (1978–1988). The measurements have been made through an Instituto Nacional de Pesquisas Espaciais (INPE)/NASA long‐term collaboration program. The balloons were released by the Brazilian Air Force at the Natal rocket range. The data set is sufficiently large to provide useful climatology on the average ozone concentration behavior and its seasonal variation. The day‐to‐day ozone concentration variability in the troposphere is rather large, giving standard deviations of about 30–40% for seasonal averages. Maximum ozone concentrations occur during local spring, September–October, and minimum concentrations during late autumn, April‐May. The seasonal variation in the troposphere is much larger than in the stratosphere. If there were no seasonal variation at all in the stratosphere, the seasonal variation observed in the troposphere alone would be strong enough to drive a total ozone column variation of about 5%, which is about one half the size of the variation observed in the Natal Dobson spectrophotometer data. The ozone concentration at Natal increases with height between the surface and about 500 mbar, almost linearly, from about 15 parts per billion by volume (ppbv) to about 38 ppbv, in autumn. For the spring average the ozone concentration increases from about 25 ppbv at the surface to about 66 ppbv at 500 mbar. The sonde data suggest that limitations in aneroid pressure sensors used until 1986 caused the Natal sondes to indicate too much ozone above 6 mbar. Because of the relative sparsity and uneven distribution in time of the ozone soundings, the data are not adequate to study ozone trends. The Dobson data time series shows no definitive ozone trend but displays a pronounced quasi‐biennial oscillation in ozone.

Ozone climatology at high elevations in the southern Appalachians

Ozone measurements are reported for two high‐elevation sites located in the Mt. Mitchell State Park in North Carolina (site 1 on Mt. Gibbs, ∼2006 m, and site 2 on Commissary Ridge, ∼1760 m). These measurements are also compared to those from a nearby, low‐elevation site (Fairview, ∼850 m). The measurements were made from May through September during the years 1986 and 1988 and from May through October during 1987, at sites 1 and 2. Measurements were also made from May through September 1989 at site 1 only. During the monitoring season at site 1 the mean ozone concentrations were 50, 51, 66, and 52 ppbv for 1986, 1987, 1988, and 1989 field seasons, respectively, while at site 2 the mean ozone concentrations were 49, 49 and 52 ppbv for 1986, 1987, and 1988. (It has been shown that exposure to ozone concentrations of ≥50 ppbv is sufficient to cause damage to certain species of vegetation.) The daily maximum, 1‐hour average, and 24‐hour average concentrations were found to be greatest during summer months (late May through early July), with lower concentrations during fall (August and September), suggesting a correlation with the seasonal photochemical cycle. It is suggested that excess hydrocarbons released during budbreak may contribute to the seasonal signal in the ozone data. During the 1988 monitoring season there were three periods of very high ozone levels (>80 ppbv) which lasted over 100 hours. During these long episodes there were 48 hours during which ozone concentrations exceeded the current National Ambient Air Quality Standard (NAAQS) of 0.12 ppmv. High hourly averaged SO2 (∼25 ppbv) and NOx (∼11 ppbv) levels were also found during these episodes. Meteorological analyses show an association between periods of high ozone concentrations and synoptic‐scale patterns. Such high gaseous pollutant concentrations were not observed during the previous two field seasons. Also, no exceedances of the NAAQS were observed during the field season of 1989. No discernible diurnal cycle in the ozone concentrations was observed at site 2; however, a reversed diurnal cycle (nighttime maximum) was evident at site 1. Also, average ozone concentrations increased from lower elevations to higher elevations. Evidence suggests that the relationship between the mountaintop and the height of the mixing layer, coupled with horizontal transport of ozone in the lower troposphere, may be important in explaining the nocturnal maximum at site 1 and the observed altitudinal gradient in ozone.

Surface ozone and meteorological predictors on a subregional scale

Meteorological conditions affect the ozone concentration near the surface. To quantify the importance of meteorological parameters for the surface ozone concentration a nonlinear regression analysis between 313 meteorological candidate predictors and surface ozone concentration at five stations in the German Democratic Republic over the period 1972–1987 has been made. The stability and quality of the relationship between ozone and meteorological predictors has been tested by independent samples. Most important predictors for surface ozone are the ozone value of the preceding day (persistence) and solar radiation. They explain 33–46% and 6–21% of the climatological ozone variance, respectively. As all meteorological parameters can be forecasted, the regression method described might be the basis for a short-term prediction of surface ozone. An analysis of long-term changes of surface ozone and solar radiation shows that changes in cloudiness are probably not the main cause of the long-term changes in surface ozone. Therefore, the ozone changes should mainly be due to changes in circulation and/or concentration of ozone precursors (NO x , VOC).

The climatology of surface ozone in rural areas: a conceptual model

The climatology of surface ozone in rural areas: a conceptual model

Distribution of tropospheric ozone determined from satellite data

An analysis of more than 22,000 ozone profiles from Stratospheric Aerosol and Gas Experiment I (SAGE I) (1979–1981) and SAGE II (1984–1987) between 50°N and 50°S is used in conjunction with 9 years (1979–1987) of daily global depictions of total ozone from the Total Ozone Mapping Spectrometer (TOMS) instrument aboard Nimbus 7 to investigate the spatial distribution and seasonal cycle of the integrated amount of ozone in the troposphere. In the tropics, highest concentrations are found in the eastern Atlantic Ocean downwind (west) of Africa and maximize during the time when biomass burning is most prevalent, between July and October. A different seasonal cycle in the tropics is also observed over Indonesia where a relative maximum is present in the March–April time frame, likewise consistent with when biomass burning is most prevalent. At mid‐latitudes, highest concentrations are found downwind of Asia and maximize in the summer. Relatively higher amounts of tropospheric ozone are similarly observed downwind of North America and Europe. At mid‐latitudes, the ratio between the amount of tropospheric ozone in the northern hemisphere and the amount in the southern hemisphere is 1.4, in good agreement with in situ measurements. A detailed comparison of this satellite technique with available ozonesonde measurements suggests that the accuracy of this method for deriving the climatology of tropospheric ozone is probably better than 10% in the tropics and 15% at mid‐latitudes. We also show that TOMS total ozone measurements in the tropics can often be used independently to provide important qualitative insight into the behavior of tropospheric ozone at these low latitudes.

Reference model for CH 4 and N 2O and trends

Data from the Stratospheric and Mesospheric Sounder on Nimbus 7 have been used as the basis for a model of the abundances of nitrous oxide and methane in the stratosphere. A version of this was produced two years ago (Taylor, Dudhia and Rodgers, /1/ — hereafter called paper 1) and in this new paper we consider some of the possible error sources in more detail, as well as long-term trends. The principal source of error in the SAMS retrievals is thought to be the use of climatological ozone profiles to invert the temperature profile data. However, we find that the effect is too small, and of the opposite sign, to explain the discrepancies between satellite and in-situ measurements, noted in paper 1. As expected, no systematic trends which exceed the estimated error in the data are found in either methane or nitrous oxide.

The sensitivity of total ozone and ozone perturbation scenarios in a two‐dimensional model due to dynamical inputs

The sensitivity of the total ozone distribution in our two‐dimensional photochemical model to dynamical inputs has been explored. The residual circulation has been computed from three sets of heating rates but using the same temperature distributions. These heating rates result in advection fields that are appropriately linked with the magnitude of their vertical winds in the lower stratosphere and are called: (1) the strong circulation, (2) the weak circulation, and (3) the combined circulation. Three different formulations of horizontal eddy diffusion have also been investigated, including (1) a small constant diffusion, (2) a computed diffusion from potential vorticity using measured temperatures, and (3) a self‐consistent diffusion determined from the meridional velocity. Finally, we studied two different formulations of vertical eddy diffusion: (1) a small constant diffusion and (2) an altitude‐dependent larger diffusion. Our modeled global average total ozone varies by up to 10%, depending on the various dynamical inputs, and the seasonal and latitudinal variabilities are even more substantial. The calculations indicate that total ozone in the middle to high latitudes is very sensitive to the advection field below 100 mbar, the region where the heating rates (which are used in computing the advection field) are most uncertain. Modeled total ozone shows better agreement with solar backscattered ultraviolet (SBUV) ozone climatology, when computed horizontal eddy diffusion is used. Our “best” modeled total ozone distribution is a result of using the heating rates from Rosenfield et al. (1987) for pressures less than 100 mbar, along with heating rates from Dopplick (1974, 1979) for pressures greater than 100 mbar. Our model results, especially when comparing model and SBUV ozone between 10 and 1 mbar, indicate that there is an inconsistency between our “best” horizontal eddy diffusion and the “best” mean residual circulation. Our studies indicate a relative similarity of a typical ozone perturbation scenario among the different dynamical inputs. All of the perturbation studies predict the smallest ozone changes in the tropical latitudes, with larger ozone changes in the middle to high latitudes. The major changes in the various perturbation results are in the middle to high latitudes: (1) the peak ozone change is off of the pole in the southern hemisphere (near 60°S latitude) using the strong circulation but centered on the pole for the various other dynamical studies, and (2) the maximum ozone change is centered at times varying from early spring to early summer, depending on which dynamical input is used.

An improved rocket ozonesonde (ROCOZ‐A): 3. Northern mid‐latitude ozone measurements from 1983 to 1985

We report the results of a set of ozone measurements at the NASA Wallops Flight Facility (37.8°N, 75.5°W) from August 1983 to September 1985. Nineteen profiles were obtained during this period, using ROCOZ‐A and electrochemical concentration cell ozonesondes, standard U.S. meteorological radio‐sondes, and Super‐Loki datasondes. Complete profiles of ozone, pressure, and temperature were obtained from the ground to 52 km, and 18 of the profiles correspond to site overpasses by ozone instruments on NASA and National Oceanic and Atmospheric Administration (NOAA) satellites. The profiles from this data set show reasonable agreement with established ozone climatologies. The annual ozone variability from the data set is roughly two thirds of the variability from the ozone model for the U.S. Standard Atmosphere (1976). The agreement between total ozone measurements from this data set and concurrent Dobson direct‐Sun total ozone measurements is excellent. The precision of ROCOZ‐A ozone values has been measured at the 3% level (1σ), and the accuracy of the ozone values is estimated at 5–7%. Since the ROCOZ‐A radiometers are expendable, the long‐term repeatability of the ozone measurements is based on a calibration facility which uses standards that are traceable to the National Bureau of Standards (NBS). The assembly of ROCOZ‐A ozone, pressure, and temperature measurements presented here allows the use of this data set as a transfer standard between satellite instruments with different fundamental ozone measurements. In addition, this data set can be used for comparisons of modeled and measured ozone amounts in the stratosphere and lower mesosphere. Such comparisons should prove valuable, since model results are typically 30–50% lower than measured ozone concentrations at altitudes above 35 km.

Toward an improved global network for determination of tropospheric ozone climatology and trends

An examination of typical tropospheric ozone variability on daily, monthly, annual and interannual timescales and instrumental precision indicates that the current ozonesonde network is insufficient to detect a trend in tropospheric ozone of ≤1% per year at the 2σ level even at stations with records a decade in length. From a trend prediction analysis we conclude that in order to detect a 1% per year trend in a decade or less it will be necessary to decrease the time between observations from its present value of 3–7 days to 1 day or less. The spatial distribution of the current ozonesonde stations is also inadequate for determining the global climatology of ozone. We present a quantitative theory taking into account photochemistry, surface deposition, and wind climatology to define the ‘effectively sampled region’ for an observing station which, used in conjunction with the instrumental precision and the above prediction analysis, forms the basis for defining a suitable global network for determining regional and global ozone climatology and trends. At least a doubling of the present number of stations is necessary, and the oceans, most of Asia, Africa, and South America are areas where more stations are most needed. Differential absorption lidar ozone instruments have the potential for far more frequent measurements of ozone vertical profiles and hence potentially more accurate climatology and trend determinations than feasible with ozonesondes but may produce a (fair weather) biased data set above the cloud base. A strategy for cloudy regions in which either each station utilizes both lidars and sondes or each station is in fact a ‘doublet’ comprised of a near-sea-level lidar and a proximal-mountain-top lidar could serve to minimize this bias.

Distribution of total ozone and stratospheric ozone in the tropics: Implications for the distribution of tropospheric ozone

Climatologies of total columnar ozone and integrated stratospheric ozone amounts at low latitudes (15°N to 15°S), derived from satellite observations, are presented. A significant longitudinal variability in total ozone is present, with highest values generally located between 60°W and 60°E. The integrated stratospheric component of total ozone, on the other hand, does not exhibit a longitudinal preference for high values. Therefore we hypothesize that the climatological longitudinal distribution of total ozone reflects the variability of the abundance of tropospheric ozone at low latitudes. Furthermore, we speculate that in situ photochemical production of ozone resulting from biomass burning may be responsible for the observed enhancement of total ozone at these longitudes.

The Middle Atmosphere In the Absence of Dynamical Heat Fluxes

AbstractA new radiative transfer scheme, developed for use in a three‐dimensional dynamical model of the stratosphere and mesosphere, is used to consider the hypothetical state of the middle atmosphere in the absence of dynamical heat fluxes. Most previous work in this area has considered radiative equilibrium temperatures using a fixed solar forcing. This equilibrium state is shown to be different from a state calculated using a seasonal cycle of solar forcing; in particular, the winter pole is found to be warmer and the latitudinal temperature gradient across the edge of the polar night is found to be smaller. This difference is due to two processes. Firstly, latitudes just polewards of the edge of the polar night at solstice are in darkness for only a short period. Secondly, radiative time scales lengthen greatly as temperatures decrease, so that equilibrium cannot be reached before the sun reappears.Recent ozone climatologies are used to impose a realistic annual cycle of ozone on the model. It is found that the simulation of the lower stratosphere is in considerably better agreement with observations than previous radiation‐only calculations. the better simulation is shown to be, in most cases, due to the use of the new ozone climatology. It is also shown that a realistic ozone distribution is necessary for a good simulation of the polar stratopause at the summer solstice.A comparison of the observed and calculated annual cycle of temperature in the polar regions of the southern hemisphere lower stratosphere indicates that this region is under strong radiative control. This contrasts with an implied strong dynamical control for the same region in the northern hemisphere.

Trace Constituents in the Mesosphere

Recent observations of selected trace constituents in the mesosphere are reviewed. The review is divided into discussions of some long-lived constituents (CO, NO and H2O), and short-lived constituents (OH and O3) that are important for understanding the transport and photochemical processes in the mesosphere. CO and NO are produced in the lower thermosphere and lost in the lower mesosphere and stratosphere. There is now observational evidence that downward transport into the winter polar region, and subsequent "spillage" into the winter mid-latitude regions are important for CO and NO. In comparison with CO and NO the distribution of H2O is "upside down" in the sense that it is generated in the lower atmosphere and flows upward to its sink. The same transport mechanism may operate for H2O, but in the opposite sense of moving dry air downward in winter, and moist air upward in summer. The short-lived OH radical is important for understanding the HOx-Ox mechanism in the middle atmosphere. Unfortunately, there is an almost complete lack of data for its distribution above 50 km. Ozone and water vapor are out-of-phase in their seasonal behavior in the upper mesosphere; the variations in both species provide important clues for understanding the causes of eddy mixing in the mesosphere. The seasonal climatology of mesospheric ozone is now well documented as a result of five years of SME satellite observations.

A synoptic climatology for surface ozone concentrations in Southern Ontario, 1976–1981

The synoptic climatology of ozone (O 3) for S Ontario has shown that, over the 1976–1981 period, average summer O 3 concentrations follow a relationship similar to that reported for event analysis during periods of high O 3 concentration. Highest average concentrations, 36 parts per billion (ppb), occur with ‘back of the high’ situations while lowest average concentrations (20 ppb) occur with ‘front of the high’ situations. With similar weather events in the winter, the pattern is reversed with highest average O 3 concentrations on the ‘front of the high’ (19 ppb) and lowest average concentrations on the ‘back of the high’ (13 ppb). Concentration of O 3 in the ‘front of the high’ sector is due in part to the intrusion of O 3 in the vicinity of storms from the stratosphere. The seasonal variation of average concentrations in these situations is low, ranging from 14 to 26 ppb. The very low average concentration during the winter and fall for the ‘back of the high’ situation may be the result of scavenging by NO x from the urban/industrial areas around the Great Lakes. During the spring and summer, solar energy and warm temperatures cause the photochemical production of O 3 from NO x and HC s precursors. In the fall and winter, photochemical production of O 3 is either very low or absent, and the NO x consume O 3 rather than produce it. Thus, average O 3 concentrations for winter ‘back of the high’ situations are one-third of those in the summer months. The synoptic climatology of events during the months from May to September with maximum O 3 concentrations in excess of 80 ppb indicates that 78 % of these events occur under synoptic weather classes generally indicative of back or centre of the high situations.

A global climatology of total ozone from the Nimbus 7 total ozone mapping spectrometer

A global climatology of total column ozone has been computed from 4 years of daily observations by the total ozone mapping spectrometer aboard the Nimbus 7 polar‐orbiting satellite. Observations were made at local noon; no observations are available in polar regions during the polar night. The orbital data have been area averaged onto a regular 5° by 5° latitude‐longitude grid. The global coverage is more than 90% complete during the last 3 observing years (October 1979 to September 1982) and approximately 70% complete during the first year (October 1978 to September 1979). Global maps of the temporal mean and rms variance and the amplitude and phase of the annual and semiannual harmonics are presented. Similar analyses of the zonal mean values are given along with a time‐latitude section of the zonal‐mean total ozone. This climatology should be useful both for validating numerical models and for inspiring theoretical analyses.

Some features of the ozone climatology of Ontario, Canada and possible contributions of stratospheric ozone to surface concentrations

Background ozone concentration displayed distinct seasonal variations at all stations, with a maximum of about 40 ppb in spring and a minimum of about 23 ppb in autumn. The monthly and yearly mean diurnal variations of ozone at urban stations exhibited bi-modal characteristics not evident at rural sites. Two daily maxima and minima were recorded at urban stations, but only one maximum and one minimum at rural sites. The second minimu min the evening at urban stations was shown to be related to high levels of nitric oxide, while nighttime heat island was considered the main cause of the second maximum. One-day resultant trajectories show that the most frequent and highest ozone concentrations were associated with a relatively light to moderate south to southwesterly flow but not with light or with strong winds. Although there were several recognizable meteorological regimes associated with elevated ozone concentrations over Ontario, those with weak pressure gradients favourable for the onset of lake breeze or with southwesterly flows on the west side of slow-moving high pressure centres crossing the eastern United States were the most frequent and resulted in the highest ozone concentrations. Ozone maxima over Ontario may mostly be attributed to long distance transport of emissions from major industrial areas south of the border. However, tropospheric and stratospheric contributions cannot be ruled out and may even be a major source at times. A case study of possible stratospheric ozone influx into the troposphere is presented.

Tropospheric ozone: The role of transport

The Geophysical Fluid Dynamics Laboratory general circulation/transport model, with photochemistry in the top level (middle stratosphere) only, is used to simulate global tropospheric ozone distributions for upper and lower limits of surface removal rates. We compared these simulations with available observations and find that large‐scale atmospheric transport plays a major role in the behavior of tropospheric ozone. Furthermore, we identify potential roles for tropospheric chemistry, discover defects in the model's simulations of transport, and gain a more global picture of tropospheric ozone. The transport model's mean cross‐tropopause flux is in the range of previous estimates, and the shapes of the simulated vertical profiles of mixing ratio and percent standard deviation are in good agreement with observations. South of 40°N, the simulated and observed latitude gradients are the same, the upper and lower limit calculations bracket measured values, and the seasonal cycles are well reproduced. While the transport model simulates a wide range of tropospheric ozone climatology, there are a significant number of disagreements. The need for additional ozone destruction in the maritime boundary layer suggests a role for chemical destruction, while in the continental boundary layer, it appears that chemical production, a seasonal cycle in surface deposition, and improved boundary layer transport are all required. The two major defects in the simulated “free troposphere” are (1) excess ozone at high latitudes of the northern hemisphere (NH) and (2) spring rather than summer maxima and fall rather than winter minima at NH mid‐ and high latitudes. While defect 1 has a number of possible causes, deficiencies in model transport play a major role. Although similar transport defects have not been ruled out for defect 2, tropospheric chemistry appears to be needed. Separate calculations of the net chemical production and loss demonstrate that this is a complex problem. The most likely solution involves the transport control of NOx which controls the ozone chemistry.

Ozone climatology over western mediterranean sea

A preliminary climatology of atmospheric ozone over Western Mediterranean Sea is given by analysis of the upper observations of O3 carried out at Cagliari-Elmas station from 1968 to 1976. Some peculiarities are here illustrated and discussed.

The validation of NIMBUS 7 LIMS measurements of ozone

Approximately months of stratospheric ozone profiles have been processed from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on NIMBUS 7. Data profiles cover the stratosphere and mesosphere from 100 to 0.1 mbar and from 84°N to 64°S latitude. The retrieved ozone profiles are not constrained in any way to an initial guess profile or to an ozone climatology. This paper describes the ozone channel characteristics, precision, systematic uncertainties, and comparisons with data from balloon and rocket underflights, Umkehr soundings, and Dobson measurements. Comparisons with Dobson total ozone are made by integrating combined LIMS plus balloon profiles. The estimated on‐orbit precision is 0.02–0.16 ppmv. Simulations of the experiment indicate potential systematic uncertainties ranging from 15% in the 1‐mbar to the 3‐mbar region to an upper limit of 40% at 100 mbar and 0.1 mbar. Comparisons with sets of correlative ozone profiles show mean differences of less than 10% from 7 to 50 mbar for mid‐latitude balloon‐borne sensors and 16% from 0.3 to 50 mbar for rocket data. Such results are well within the uncertainties for the correlative sensors themselves. Agreement with balloon measurements degrades somewhat at tropical latitudes in the lower stratosphere. LIMS detects significant vertical structure in the ozone profile even below the ozone mixing ratio peak. Preliminary comparisons with Umkehr data at four stations show generally good agreement from 1 to 30 mbar. The zonal mean ozone cross section for March 1979 compares well with ozone climatologies reported by Dutsch (1974) and with more recent data obtained for a similar time of year using satellite instruments operating at the much different ultraviolet and visible wavelengths. When taken together with the other LIMS parameters (temperature, H2O, HNO3, and NO2), this new ozone data set can be used to study middle atmospheric processes.

Stratospheric ozone as viewed from the Chappuis band

Stratospheric total ozone values have been obtained for the period 1912–50 from analysis of Smithsonian data. Naturally caused variations of 25% or more are common over time scales ranging from months to decades. We suggest that the ozone layer acts as a shutter on the incoming solar energy, providing one of the long sought trigger mechanisms betwen solar activity and climatic change. The present state of knowledge of ozone climatology is not sufficient to support popular speculations about man's effects on the ozone layer.