Vertical Ozone Profiles Research Articles

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A WRF–SMOKE–CMAQ modeling system was used to simulate vertical profiles of ozone, temperature and wind as well as surface ozone and meteorology during the Study of Houston Atmospheric Radical Precursors (SHARP) in May 2009. WRF and CMAQ sensitivity studies were conducted to define a proper combination of model configurations.With objective analysis WRF showed considerable skills in simulating temperature and wind profiles. CMAQ did well in replicating daily regional average ozone, with only minor overprediction for most of the days. According to the surface ozone statistics and the ozone biases along the vertical profiles, the model displayed little sensitivity to the two CMAQ model options: (i) fixed night time PBL height vs. WRF calculated night time PBL heights, and (ii) the combination of the Euler-backward iterative chemistry schemes and Yamartino advection (EBI/YAMO) vs. the Sparse-Matrix Vectorized Gear chemistry and Parabolic Method advection (SMV-GEAR/PPM) schemes. CMAQ shows substantial underprediction of ozone in the upper troposphere, but demonstrated fair skills in reproducing the ozone profile in the lower to middle troposphere, with typically a few ppb negative biases which tend to increase with height. However, the model usually cannot reproduce high variability in the ozone profiles due to the fixed default profiles and lack of data assimilation capability. While the default CMAQ static profile setup for boundary condition (BC) does not properly reflect the actual dynamic atmosphere, it remains a reasonable choice, since using downscaled real-time global chemistry model BCs demands considerable efforts and would still depend on the performance of the global model.

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A WRF–SMOKE–CMAQ modeling system was used to simulate vertical profiles of ozone, temperature and wind as well as surface ozone and meteorology during the Study of Houston Atmospheric Radical Precursors (SHARP) in May 2009. WRF and CMAQ sensitivity studies were conducted to define a proper combination of model configurations.With objective analysis WRF showed considerable skills in simulating temperature and wind profiles. CMAQ did well in replicating daily regional average ozone, with only minor overprediction for most of the days. According to the surface ozone statistics and the ozone biases along the vertical profiles, the model displayed little sensitivity to the two CMAQ model options: (i) fixed night time PBL height vs. WRF calculated night time PBL heights, and (ii) the combination of the Euler-backward iterative chemistry schemes and Yamartino advection (EBI/YAMO) vs. the Sparse-Matrix Vectorized Gear chemistry and Parabolic Method advection (SMV-GEAR/PPM) schemes. CMAQ shows substantial underprediction of ozone in the upper troposphere, but demonstrated fair skills in reproducing the ozone profile in the lower to middle troposphere, with typically a few ppb negative biases which tend to increase with height. However, the model usually cannot reproduce high variability in the ozone profiles due to the fixed default profiles and lack of data assimilation capability. While the default CMAQ static profile setup for boundary condition (BC) does not properly reflect the actual dynamic atmosphere, it remains a reasonable choice, since using downscaled real-time global chemistry model BCs demands considerable efforts and would still depend on the performance of the global model.

First stage of Antarctic ozone recovery

Ozone within the springtime Antarctic vortex is affected by both chemical and dynamical processes. We use correlations between monthly means of total ozone columns and temperatures in the vortex core and the vortex edge (or collar) regions to construct ozone anomaly time series for September and October, which mainly reflect variations in ozone due to chemical forcing. The ozone anomaly time series, obtained from ground‐based Dobson/Brewer column measurements, reveal a statistically significant leveling off of total ozone, relative to the previous rate of decline, since 1997. The second derivative with respect to time of stratospheric halogen loading in the Antarctic vortex reached a well‐defined minimum in 1997, marking the time when the chemical forcing of polar ozone loss started leveling off. Vertical profiles of ozone in the Antarctic vortex from SAGE II and ozonesondes show that near‐zero levels of ozone have sometimes been reached in the core of the vortex each October, between the 380 and 500 K isentropes, since 1992. We have accounted for this so‐called loss saturation effect in our analysis by comparing the frequency distribution of measured ozone with the distribution expected from a reconstruction of ozone that hypothetically allows ozone abundances to drop below zero. This approach indicates that changes in stratospheric halogen loading, not the loss saturation effect, are the primary cause of the recent leveling off of the total ozone anomaly time series. This analysis indicates that total column ozone within the Antarctic vortex core and collar regions has reached the first stage of recovery as defined by the World Meteorological Organization: a statistically significant reduction in the rate of decline that is clearly attributable to decreases in the abundance of ozone‐depleting substances brought about by the Montreal Protocol.

서울지역 연직 오존 분포: 2003년 6월 6~9일 오존존데 관측

Variability in vertical ozone and meteorological profiles was measured by 2Z electrochemical concentration cells (ECC) ozonesonde at Bangyi in Seoul (, ) during June , 2003 in odor to identify the vertical distribution of ozone and its relationship with the lower-atmospheric structure resulted in the high ozone concentrations near the surface. The eight profiles obtained in the early morning and the late afternoon during the study period clearly showed that the substantial change of ozone concentrations in lower atmosphere(), indicating that it is tightly coupled to the variation of the planetary boundary layer (PBL) structure as well as the background synoptic flow. All profiles observed early in the morning showed very low ozone concentrations near the surface with strong vertical gradients in the nocturnal stable boundary layer due to the photochemical ozone loss caused by surface NO titration under very weak vertical mixing. On the other hand, relatively uniform ozone profiles in the developed mixing layer and the ozone peaks in the upper PBL, were observed in the late afternoon. It was noted that a significant increase in ozone concentrations in the lower atmosphere occurred with the corresponding decrease of the mixing height in the late afternoon on June 8. Ozone in upper layer did not vertically vary much compared to that in PBL but changed significantly on June 6 that was closely associated with the variation of synoptic flows. Interestingly, heavily polluted ozone layers aloft (a maximum value of 115 ppb around 2 km) were formed early in the morning on 6 through 7 June under dominant westerly synoptic flows. This indicates the effects of the transport of pollutants on regional scale and consequently can give a rise to increase the surface ozone concentration by downward mixing processes enhanced in the afternoon.

Comparison of ozone profiles by the Umkehr measurements taken at Belsk (52°N, 21°E) with the Aura Microwave Limb Sounder overpasses: 2004–2006

A comparison of ozone profile measurements by the Umkehr observations taken at Belsk (52°N, 21°E) by the Dobson spectrophotometer and collocated Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura platform during 2004–2006 site overpasses is presented. The MLS ozone vertical profiles from 1.5 and 2.2 retrieval algorithms and various Umkehr retrievals are considered. There is a good agreement between the ozone content in Umkehr layers. The mean difference ∼ ±5%, standard deviation of the relative differences < 10%, and the correlation coefficient > 0.5 are found in the midstratosphere (Umkehr layers 5–7) and in the upper stratosphere (combined layers 8, 9, and 10). In the lower stratosphere (combined layers 2 and 3 and layer 4) the mean difference and/or standard deviation are larger but the correlation coefficient is still high (∼0.8). Ozone content in Umkehr layers by integration of MLS version 1.5 and 2.2 ozone mixing ratio profiles behaves very similarly in the comparisons with the ground‐based data.

Association of the vertical ozone structure with the lower‐stratospheric circulation

This study aims to examine the role of the atmospheric circulation in the lower stratosphere in relation to the vertical ozone distribution. This analysis is based on the vertical ozone profiles collected by balloon‐borne sondes released at Athens, Greece (38° N, 24° E) during the period 2002–2005 and those derived from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) observations of ENVISAT. The most pronounced special features of the ozone structure have been used in order to create groups of relevant profiles. The occurrence of the laminated ozone structure, the minimum of ozone partial pressure at the height region of 14–17 km and the ozone minima at the height region of 20–25 km as well as the scalable ozone increment from the region of the characteristic ozone minimum up to the ozone maximum concentration region, correlated with the general circulation, leads to several results. They are (1) the laminated ozone profiles are associated with the north‐north‐west circulation in the lower stratosphere; (2) the characteristic ozone minimum is related to the influence of the subtropical jet stream circulation; (3) the observed ozone depletion at the height region of 20–25 km is characterized by the movement of the polar vortex to the mid‐latitudes, resulting in more intense north‐western circulation above our experimental site; and (4) the scalable ozone increment from the characteristic ozone minimum region at 100 hPa up to the region where the ozone partial pressure takes its maximum value was observed on the southern side of the trough during cyclonic flow.

Background ozone levels of air entering the west coast of the US and assessment of longer-term changes

An analysis of surface ozone measurements at a west coast site in northern California (Trinidad Head) demonstrates that this location is well situated to sample air entering the west coast of the US from the Pacific Ocean. During the seasonal maximum in the spring, this location regularly observes hourly average ozone mixing ratios ⩾50 ppbv in air that is uninfluenced by the North American continent. Mean daytime values in the spring exceed 40 ppbv. A location in southern California (Channel Islands National Park) demonstrates many of the characteristics during the spring as Trinidad Head in terms of air flow patterns and ozone amounts suggesting that background levels of ozone entering southern California from the Pacific Ocean are similar to those in northern California. Two inland locations (Yreka and Lassen Volcanic National Park) in northern California with surface ozone data records of 20 years or more are more difficult to interpret because of possible influences of local or regional changes. They show differing results for the long-term trend during the spring. The 10-year ozone vertical profile measurements obtained with weekly ozonesondes at Trinidad Head show no significant longer-term change in tropospheric ozone.

A new technique for retrieval of tropospheric and stratospheric ozone profiles using sky radiance measurements at multiple view angles: Application to a Brewer spectrometer

This paper describes and applies a new technique for retrieving diurnal variability in tropospheric ozone vertical distribution using ground‐based measurements of ultraviolet sky radiances. The measured radiances are obtained by a polarization‐insensitive modified Brewer double spectrometer located at Goddard Space Flight Center, in Greenbelt, Maryland, USA. Results demonstrate that the Brewer angular (0–72° viewing zenith angle) and spectral (303–320 nm) measurements of sky radiance in the solar principal plane provide sufficient information to derive tropospheric ozone diurnal variability. In addition, the Brewer measurements provide stratospheric ozone vertical distributions at least twice per day near sunrise and sunset. Frequent measurements of total column ozone amounts from direct‐sun observations are used as constraints in the retrieval. The vertical ozone profile resolution is shown in terms of averaging kernels to yield at least four points in the troposphere–low stratosphere, including good information in Umkehr layer 0 (0–5 km). The focus of this paper is on the derivation of stratospheric and tropospheric ozone profiles using both simulated and measured radiances. We briefly discuss the necessary modifications of the Brewer spectrometer that were used to eliminate instrumental polarization sensitivity so that accurate sky radiances can be obtained in the presence of strong Rayleigh scattering and aerosols. The results demonstrate that including a site‐specific and time‐dependent aerosol correction, based on Brewer direct‐sun observations of aerosol optical thickness, is critical to minimize the sky radiance residuals as a function of observing angle in the optimal estimation inversion algorithm and improve the accuracy of the retrieved ozone profile.

Low level of stratospheric ozone near the Jharia coal field in India

The Indian reserve of coking coal is mainly located in the Jharia coal field in Jharkhand. Although air pollution due to oxides and dioxides of carbon, nitrogen and sulphur is reported to have increased in this area due to large-scale opencast mining and coal fires, no significant study on the possible impact of coal fires on the stratospheric ozone concentration has been reported so far. The possible impact of coal fires, which have been burning for more than 90 years on the current stratospheric ozone concentration has been investigated using satellite based data obtained from Upper Atmospheric Research Satellite (UARS MLS), Earth Observing System Microwave Limb Sounder (EOS MLS) and Ozone Monitoring Instrument (OMI) in this paper. The stratospheric ozone values for the years 1992–2007, in the 28–36 km altitude range near Jharia and places to its north are found to be consistently lower than those of places lying to its south (up to a radius of 1000 km around Jharia) by 4.0–20%. This low stratospheric ozone level around Jharia is being observed and reported for the first time. However, due to lack of systematic ground-based measurements of tropospheric ozone and vertical ozone profiles at Jharia and other far off places in different directions, it is difficult to conclude strongly on the existence of a relationship between pollution from coal fires and stratospheric ozone depletion.

Measurements and Mesoscale Modeling of Autumnal Vertical Ozone Profiles in Southern Taiwan

Vertical measurements of ozone were made using a tethered balloon at the Linyuan site in Kaohsiung County, southern Taiwan. Ozone was monitored at altitudes of 0, 100, 300, 500, and 1000 m from November 23 to 25 in 2005. The potential temperature profiles revealed a stable atmosphere during the study period, largely because of the dominance of the high-pressure system and nocturnal radiation cooling close to the surface. The mixing height was low (50-300 m), particularly in the late night and early morning. The surface ozone concentrations that were predicted using TAPM (The Air Pollution Model) were high (33.7-119 ppbv) in the daytime (10:00-16:00) and were low (10-40 ppbv) at other times; the predictions of which were consistent with the observations. The simulated surface ozone concentrations reveal that costal lands typically had higher ozone concentrations than those inland, because most industrial parks are located in or close to the boundaries of Kaohsiung City. Both measurements and simulations indicate that daytime ozone concentrations decreased quickly with increasing height at altitudes below 300 m; while nighttime ozone concentrations were lower at low altitudes (50 to 300 m) than at higher altitudes, partly because of dry deposition and titration of surface ozone by the near-surface nitrogen oxides (NO(subscript x)) and partly because of the existence of the residual layer above the stable nocturnal boundary layer. The simulations show a good correlation between the maximum daytime surface ozone concentration and average nighttime ozone concentration above the nocturnal boundary layer.

Demonstration and validation of the φ-IASI inversion scheme with NAST-I data

The physical forward/inverse scheme φ-IASI has been applied to the retrieval of atmospheric vertical profiles of temperature, water vapour and ozone by inverting high spectral infrared observations recorded by the NAST-I Fourier Transform Spectrometer. For the retrieval exercise we have used clear-sky spectra recorded over the sea surface on the night of 9–10 September 2004, during the Italian phase of the EAQUATE field campaign. During the campaign NAST-I flew on board the NASA Proteus aircraft at an altitude of 15 km. Retrievals have been compared to radiosonde observations, profiles from the ECMWF analysis and AIRS level 2 products. While providing a basis for the validation of the φ-IASI inversion scheme, the retrieval exercise has also demonstrated (i) the NAST-I ability to accurately detect H2O fine-scale vertical features, and (ii) the good quality of the temperature and water vapour profiles from the ECMWF analysis. Copyright © 2007 Royal Meteorological Society

Retrieval of atmospheric ozone profiles from an infrared quantum cascade laser heterodyne radiometer: results and analysis

Following the recent development of a ground-based prototype quantum cascade laser heterodyne radiometer operating in the midinfrared, atmospheric ozone profile retrievals from a solar occultation measurement campaign performed at the Rutherford Appleton Laboratory on 21 September 2006 are presented. Retrieval is based on the optimal estimation method. High resolution (0.0073 cm(-1)) atmospheric spectra recorded by the laser heterodyne radiometer and covering a microwindow (1033.8-1034.5 cm(-1)) optimized for atmospheric ozone measurements were used as measurement vectors. As part of the evaluation of this novel instrument, a comprehensive analysis of the retrievals is presented, demonstrating the high potential of quantum cascade laser heterodyne radiometry for atmospheric sounding. Vertical resolutions of 2 km near the ground and about 3 km in the stratosphere were obtained. The information content of the retrieval was found to be up to 48 bits, which is much higher than any other passive ground-based instrument. Frequency mismatches of several absorption peaks between the forward model and experimental spectra have been observed and significantly contribute to the retrieval noise error in the upper-troposphere lower-stratosphere region. Retrieved ozone vertical profiles were compared to ozonesonde data recorded at similar latitudes. The agreement is generally excellent except for the 20 to 25 km peak in ozone concentration, where ozonesonde data were found to be 20% lower than the amount retrieved from the laser heterodyne radiometer spectra. Quantum cascade laser based heterodyne radiometry in the midinfrared has been demonstrated to provide high spectral resolution and unprecedented vertical resolution for a passive sounder in a highly compact and mechanically simple package.

Comparison of the inversion algorithms applied to the ozone vertical profile retrieval from SCIAMACHY limb measurements

Abstract. This paper is devoted to an intercomparison of ozone vertical profiles retrieved from the measurements of scattered solar radiation performed by the SCIAMACHY instrument in the limb viewing geometry. Three different inversion algorithms including the prototype of the operational Level 1 to 2 processor to be operated by the European Space Agency are considered. Unlike usual validation studies, this comparison removes the uncertainties arising when comparing measurements made by different instruments probing slightly different air masses and focuses on the uncertainties specific to the modeling-retrieval problem only. The intercomparison was performed for 5 selected orbits of SCIAMACHY showing a good overall agreement of the results in the middle stratosphere, whereas considerable discrepancies were identified in the lower stratosphere and upper troposphere altitude region. Additionally, comparisons with ground-based lidar measurements are shown for selected profiles demonstrating an overall correctness of the retrievals.

Validation of AIRS v4 ozone profiles in the UTLS using ozonesondes from Lauder, NZ and Boulder, USA

Ozonesonde observations from Lauder (45.0°S, 169.7°E) and Boulder (39.9°N, 105.3°W) are used to examine the quality of the Atmospheric Infrared Sounder (AIRS) v4 vertical ozone profile product in the upper troposphere lower stratosphere (UTLS). At lower altitudes (∼700–200 hPa pressure range), AIRS ozone mixing ratios are larger than ozonesonde measurements, and at higher altitudes (∼100–30 hPa pressure range), AIRS ozone mixing ratios are smaller. Compared to the ozonesondes, AIRS retrieval results at Lauder have a median bias of 80% in the region 700–200 hPa, and 0 to −20% in the region 100–30 hPa. For Boulder these values are 40% and 0 to 5%, respectively. Using a tropopause adjusted vertical coordinate system, Lauder has median biases of +90 to +120% in the troposphere and 0 to +25% in the stratosphere whereas Boulder shows median biases of +45 to +70% in the troposphere and 0 to +35% in the stratosphere. Despite the bias, AIRS retrieval in the UTLS region shows a statistically significant positive correlation with the ozonesonde data, indicating that while the absolute values have a large uncertainty, the retrieval captures the variability of ozone in the UTLS region. Hence AIRS ozone is suitable for studies where the change in ozone is important rather than the absolute ozone mixing ratio. Examinations of the training data set show that the retrieval biases are likely influenced by the deficiency of the training data to represent ozone distribution during the regression step of the retrieval. Furthermore the physical retrieval adds little additional information to the final result.

Characteristics and error estimation of stratospheric ozone and ozone-related species over Poker Flat (65° N, 147° W), Alaska observed by a ground-based FTIR spectrometer from 2001 to 2003

Abstract. It is important to obtain the year-to-year trend of stratospheric minor species in the context of global changes. An important example is the trend in global ozone depletion. The purpose of this paper is to report the accuracy and precision of measurements of stratospheric chemical species that are made at our Poker Flat site in Alaska (65° N, 147° W). Since 1999, minor atmospheric molecules have been observed using a Fourier-Transform solar-absorption infrared Spectrometer (FTS) at Poker Flat. Vertical profiles of the abundances of ozone, HNO3, HCl, and HF for the period from 2001 to 2003 were retrieved from FTS spectra using Rodgers' formulation of the Optimal Estimation Method (OEM). The accuracy and precision of the retrievals were estimated by formal error analysis. Errors for the total column were estimated to be 5.3%, 3.4%, 5.9%, and 5.3% for ozone, HNO3, HCl, and HF, respectively. The ozone vertical profiles were in good agreement with profiles derived from collocated ozonesonde measurements that were smoothed with averaging kernel functions that had been obtained with the retrieval procedure used in the analysis of spectra from the ground-based FTS (gb-FTS). The O3, HCl, and HF columns that were retrieved from the FTS measurements were consistent with Earth Probe/Total Ozone Mapping Spectrometer (TOMS) and HALogen Occultation Experiment (HALOE) data over Alaska within the error limits of all the respective datasets. This is the first report from the Poker Flat FTS observation site on a number of stratospheric gas profiles including a comprehensive error analysis.

Vertical ozone measurements in the troposphere over the Eastern Mediterranean and comparison with Central Europe

Abstract. Vertical ozone profiles measured in the period 1996–2002 in the framework of the MOZAIC project (Measurement of Ozone and Water Vapor by Airbus in Service Aircraft) for flights connecting Central Europe to the Eastern Mediterranean basin (Heraklion, Rhodes, Antalya) were analysed in order to evaluate the high rural ozone levels recorded in the Mediterranean area during summertime. The 77 flights during summer (JJAS) showed substantially (10–12 ppb, 20–40%) enhanced ozone mixing ratios in the lower troposphere over the Eastern Mediterranean frequently exceeding the 60 ppb, 8-h EU air quality standard, whereas ozone between 700 hPa and 400 hPa was only slightly (3–5 ppb, 5–10%) higher than over Central Europe. Analysis of composite weather maps for the high and low ozone cases, as well as back-trajectories and vertical profiles of carbon monoxide, suggest that the main factor leading to high tropospheric ozone values in the area is anticyclonic influence, in combination with a persistent northerly flow in the lower troposphere during summertime over the Aegean. On the other hand the lowest ozone levels are associated with low-pressure systems, especially the extension of the Middle East low over the Eastern Mediterranean area.

Bias determination and precision validation of ozone profiles from MIPAS-Envisat retrieved with the IMK-IAA processor

Abstract. This paper characterizes vertical ozone profiles retrieved with the IMK-IAA (Institute for Meteorology and Climate Research, Karlsruhe – Instituto de Astrofisica de Andalucia) science-oriented processor from high spectral resolution data (until March 2004) measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the environmental satellite Envisat. Bias determination and precision validation is performed on the basis of correlative measurements by ground-based lidars, Fourier transform infrared spectrometers, and microwave radiometers as well as balloon-borne ozonesondes, the balloon-borne version of MIPAS, and two satellite instruments (Halogen Occultation Experiment and Polar Ozone and Aerosol Measurement III). Percentage mean differences between MIPAS and the comparison instruments for stratospheric ozone are generally within ±10%. The precision in this altitude region is estimated at values between 5 and 10% which gives an accuracy of 15 to 20%. Below 18 km, the spread of the percentage mean differences is larger and the precision degrades to values of more than 20% depending on altitude and latitude. The main reason for the degraded precision at low altitudes is attributed to undetected thin clouds which affect MIPAS retrievals, and to the influence of uncertainties in the water vapor concentration.

Comparative analysis of SBUV/2 and HALOE ozone profiles and trends

The Halogen Occultation Experiment (HALOE) (version 19) ozone vertical profiles are compared with the data obtained by the second generation Solar Backscatter Ultraviolet (SBUV)/2 instruments from the National Oceanic and Atmospheric Administration’s NOAA‐11 and NOAA‐16 satellites using its version 8 algorithm. We examine the inverse noise‐weighted mean percent differences between the HALOE and SBUV/2 ozone profiles at near coincident points and obtain a bias of less than 9% from 40 to 1.5 mb for the NOAA‐11 and NOAA‐16 satellite data records, with few exceptions. The weighted root mean square (RMS) differences between the HALOE and SBUV/2 observations are generally between 4 and 15% for pressure levels 40–1.5 mb. The RMS differences are larger for the NOAA‐16 SBUV/2 data for higher latitudes. We also analyze the time‐dependent differences between the two instruments in order to establish whether there is a significant relative drift. The slopes of time series of differences between the HALOE ozone profiles and the NOAA‐11 and NOAA‐16 SBUV/2 retrievals are, by and large, less than 1% per year and 2% per year, respectively. These results suggest a changing calibration in the NOAA‐11 SBUV/2 instrument. Then we investigate the differences between ozone trends determined by the HALOE and SBUV/2 instruments. Trend differences are less than 0.5% per year in almost all latitude bands at pressure levels 10 and 3 mb. There are statistically significant biases of about 0.7% per year at 5 mb from 20°S to 50°N, and the trend differences are less than 1.3% per year at 60°–30°S.

Retrieval of tropospheric ozone: The synergistic use of thermal infrared emission and ultraviolet reflectivity measurements from space

We investigate the synergistic use of ultraviolet reflectivity measurements in the spectral range of 290–320 nm and the thermal emission spectra at the 9.6‐μm ozone absorption band for the retrieval of vertical distribution of tropospheric ozone from satellite observations. Retrievals of vertical ozone profiles are performed from simulated measurements for different atmospheric conditions. The retrievals show that the use of measurements of both spectral ranges can improve significantly the retrieved ozone in the lowest 5 km of the troposphere. Here largest improvements are found for tropical temperature distributions and for a low thermal contrast in the lower troposphere. So the use of both spectral bands may help to improve the remote sensing of tropospheric ozone from space.

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

Abstract. The results from three 45-year simulations of a coupled chemistry climate model are analysed for solar cycle influences on ozone and temperature. The simulations include UV forcing at the top of the atmosphere, which includes a generic 27-day solar rotation effect as well as the observed monthly values of the solar fluxes. The results are analysed for the 27-day and 11-year cycles in temperature and ozone. In accordance with previous results, the 27-day cycle results are in good qualitative agreement with observations, particularly for ozone. However, the results show significant variations, typically a factor of two or more in sensitivity to solar flux, depending on the solar cycle. In the lower and middle stratosphere we show good agreement also between the modelled and observed 11-year cycle results for the ozone vertical profile averaged over low latitudes. In particular, the minimum in solar response near 20 hPa is well simulated. In comparison, experiments of the model with fixed solar phase (solar maximum/solar mean) and climatological sea surface temperatures lead to a poorer simulation of the solar response in the ozone vertical profile, indicating the need for variable phase simulations in solar sensitivity experiments. The role of sea surface temperatures and tropical upwelling in simulating the ozone minimum response are also discussed.