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1. Introduction An efficient black layer coating is required for the manufacture of diffraction gratings with a holographic technique. In this process two s-polarized, 413-nm-wavelength laser beams impinge onto an aluminum substrate coated with a photoresist layer at an angle of 25° Fig. 1. There they interfere to form a grating pattern in the photoresist. After exposure and etching, the photoresist is removed, prior to illumination, leaving a grating at the surface of the aluminum substrate. For a good process and to avoid problems resulting from thin-film ...

The importance of measurements of the vertical distribution of odd nitrogen in studies of ozone chemistry and climate change has long being recognized. In this paper, we use the optimal estimation method developed by Rodgers (1976, 1990) to retrieve NO 2 vertical profiles from slant column observations made with a portable ultraviolet (UV)-visible zenith-sky spectrometer operated on the ground during the Middle Atmosphere Nitrogen TRend Assessment (MANTRA) balloon campaign carried out at Vanscoy, Saskatchewan, Canada (52°N, 107°W), from 18 to 25 August 1998. Late summer was chosen for the campaign because the stratospheric zonal wind velocity changes sign at that time. Under such conditions the stratospheric winds are at a minimum, leaving the stratosphere in a dynamically quiescent state and closer to photochemical control (Fahey et al., 2001; Fioletov and Shepherd, 2003). The NO 2 profile retrieved from the ground-based observations is compared with the co-located and simultaneous NO 2 profile measured by a balloon-borne UV-visible spectrometer during sunrise on 24 August. Good agreement is observed, giving us confidence in the retrieval technique adopted. The retrieved NO 2 profiles are also compared with the output of the Model for Evaluating oZONe trends (MEZON) 3D stratospheric chemical transport model. It is observed that, for altitudes below the peak concentration, the model underestimates the NO 2 amount, and at the altitude of peak concentration, the model values lie between the values measured from the balloon and those retrieved from the ground-based measurements. Nevertheless, the model reproduces the general shape of the retrieved profiles, including the altitude of the NO 2 maximum, for both sunrise and sunset conditions. RÉSUMÉ [Traduit par la rédaction] L'importance des mesures de la distribution verticale de l'azote radiculaire dans les études de la chimie de l'ozone et du changement climatique est depuis longtemps reconnue. Dans cet article, nous utilisons la méthode d'estimation optimale mise au point par Rodgers (1976, 1990) pour produire des profils verticaux de NO 2 à partir d'observations dans une colonne oblique faites à l'aide d'un spectromètre zénithal ultraviolet-visible portatif placé au sol lors de l'Évaluation des tendances de l'azote dans l'atmosphère moyenne (projet MANTRA) qui a eu lieu à Vanscoy (52°N, 107°W), en Saskatchewan, du 18 au 25 août 1998. C'est vers la fin de l'été que la campagne a eu lieu parce que la vitesse du vent stratosphérique zonal change de signe à ce moment. Dans ces conditions, le vent stratosphérique est à son minimum et la stratosphère se trouve dans un état de repos dynamique et plus près d'une régulation photochimique (Fahey et al., 2001; Fioletov and Shepherd, 2003). Nous comparons le profil de NO 2 produit à partir des observations faites depuis le sol au profil de NO 2 mesuré au même endroit et au même moment par un spectromètre UV-visible emporté par ballon au lever du soleil le 24 août. Les profils s'accordent bien, ce qui nous donne confiance dans la méthode de production adoptée. Nous comparons aussi les profils de NO 2 produits du modèle de transport chimique stratosphérique 3D MEZON (Model for Evaluating oZONe trends). On constate que, pour les altitudes en bas de la concentration de pointe, le modèle sousestime la valeur de NO 2 , et que, à l'altitude de la concentration de pointe, les valeurs du modèle sont entre les valeurs mesurées du ballon et les valeurs dérivées des mesures au sol. Toutefois, le modèle reproduit la forme générale des profils produits, y compris l'altitude du maximum de NO 2 , tant lors du lever que du coucher du soleil.

This paper provides an overview of the measurement systems available to make observations of the chemistry of the ozone layer. The characteristics and applications of the data collected are considered. Models provide insight into the physical processes taking place that determine the state of the ozone layer. The properties and uses of a number of models are examined. RÉSUMÉ [Traduit par la rédaction] Cet article donne une vue d'ensemble des systèmes de mesure dont on dispose pour faire des observations de la chimie de la couche d'ozone. Nous examinons les caractéristiques et les applications des données recueillies. Les modèles fournissent des indices sur les processus physiques en jeu qui déterminent l'état de la couche d'ozone. Nous examinons les propriétés et l'utilisation de différents modèles.

The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO 3 , ClONO 2 , and N 2 O 5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N 2 O 5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO 3 , ClONO 2 , and N 2 O 5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO 3 and ClONO 2 were also compared with measurements by groundbased Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO 3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv (±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within ±10% between 10 and 36 km. ACE-FTS HNO 3 partial columns (∼15-30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8 • S-76.5 • N. Good agreement between ACE-FTS ClONO 2 and MI-PAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO 2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N 2 O 5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N 2 O 5 maximum (around 30 km). Mean absolute differences at lower altitudes (16-27 km) are typically

This paper presents extensive bias determination analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloonborne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45-60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about +20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within ±10% (average values within ±6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (∼35-55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45-55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements.

Vertical profiles of NO 2 and NO have been obtained from solar occultation measurements by the Atmospheric Chemistry Experiment (ACE), using an infrared Fourier Transform Spectrometer, ACE-FTS, and an ultraviolet-visible-near-infrared spectrometer, MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). In this paper, the quality of the ACE-FTS version 2.2 NO 2 and NO and the MAESTRO version 1.2 NO 2 data are assessed using other solar occultation measurements (HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY), stellar occultation measurements (GOMOS), limb measurements (MIPAS, OSIRIS), nadir measurements (SCIAMACHY), balloon measurements (SPIRALE, SAOZ) and ground-based measurements (UV-VIS, FTIR). Time differences between the comparison measurements were reduced using either a tight coincidence criterion, or where possible, chemical box models. ACE-FTS NO 2 and NO and the MAESTRO NO 2 are generally consistent with the correlative data. The ACE-FTS NO 2 VMRs agree with the satellite data sets to within about 20% between 25 and 40 km, and suggest a negative bias between 23 and 40 km of about −10%. In comparisons with HALOE, ACE-FTS NO VMRs typically agree to ±8% from 22 to 64 km and to +10% from 93 to 105 km. Partial column comparisons for NO 2 show that there is fair agreement between the ACE instruments and the FTIRs, with a mean difference of +7.3% for ACE-FTS and +12.8% for MAESTRO. 1 Introduction This is one of two papers describing the validation of NO y species measured by the Atmospheric Chemistry Experiment (ACE) through comparisons with coincident measurements. The total reactive nitrogen, or NO y , family consists of active nitrogen, NO x (NO+NO 2), and all oxidized nitrogen species, including NO 3 , HNO 3 , HNO 4 , ClONO 2 , BrONO 2 and N 2 O 5. The ACE-Fourier Transform Spectrometer (ACE-FTS) measures

The first three Canadian Arctic ACE validation campaigns were held during polar sunrise at Eureka, Nunavut, Canada (80 • N, 86 • W) from 2004 to 2006 in support of validation of the ACE (Atmospheric Chemistry Experiment) satellite mission. Three or four zenith-sky viewing UV-visible spectrometers have taken part in each of the three campaigns. The differential slant column densities and vertical column densities from these instruments have been compared following the methods of the UV-visible Working Group of the NDACC (Network for Detection of Atmospheric Composition Change). The instruments are found to partially agree within the required accuracies for both species, although both the vertical and slant column densities are more scattered than required. This might be expected given the spatial and temporal variability of the Arctic stratosphere in spring. The vertical column densities are also compared to integrated total columns from ozonesondes and integrated partial columns from the ACE-FTS (ACE-Fourier Transform Spectrometer) and ACE-MAESTRO (ACE-Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) instruments on board ACE. For both species, the columns from the ground-based instruments and the ozonesondes are found to generally agree within their combined error bars. The ACE-FTS ozone partial columns and the ground-based total columns agree within 4.5%, averaged over the three campaigns. The ACE-MAESTRO ozone partial columns are generally smaller than those of the ground-based instruments, by an average of 9.9%, and are smaller than the ACE-FTS columns by an average of 14.4%. The ACE-FTS NO 2 partial columns are an average of 13.4% smaller than the total columns from the ground-based instruments, as expected. The ACE-MAESTRO NO 2 partial columns are larger than the total columns of the ground-based instruments by an average of 2.5% and larger than the partial columns of the ACE-FTS by an average of 15.5%.

The MANTRA (Middle Atmosphere Nitrogen TRend Assessment) 2004 campaign took place in Vanscoy, Saskatchewan, Canada (52 • N, 107 • W) from 3 August to 15 September, 2004. In support of the main balloon launch, a suite of five zenith-sky and direct-Sun-viewing UV-visible ground-based spectrometers was deployed, primarily measuring ozone and NO 2 total columns. Three Fourier transform spectrometers (FTSs) that were part of the balloon payload also performed ground-based measurements of several species, including ozone. Ground-based measurements of ozone and NO 2 differential slant column densities from the zenith-viewing UV-visible instruments are presented herein. They are found to partially agree within NDACC (Network for the Detection of Atmospheric Composition Change) standards for instruments certified for process studies and satellite validation. Vertical column densities of ozone from the zenithsky UV-visible instruments, the FTSs, a Brewer spectrophotometer, and ozonesondes are compared, and found to agree within the combined error estimates of the instruments (15%). NO 2 vertical column densities from two of the UV-visible instruments are compared, and are also found to agree within combined error (15%).

Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990-2002 are used to retrieve vertical profiles of HNO 3 , CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and optimization steps. The retrieved HNO 3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. We therefore find no evidence of long-term changes in the HNO 3 summer mid-latitude profile, although the uncertainty of our measurements precludes a conclusive trend analysis.

The purpose of this study is to perform a global search of the upper troposphere (z≥10 km) for enhancements of nitrogen dioxide and determine their sources. We have searched two years (May 2003-May 2005) of OSIRIS (Optical Spectrograph and Infrared Imager System) operational NO 2 data (version 2.3/2.4) to find large en

Abstract. We have developed models of physically-based cloud and ocean surfaces for use in photochemical models. These surface models are described in terms of a flux albedo and a normalized reflection function. Through these, the dependence of albedo on wavelength, solar zenith ...

The vertical distribution of stratospheric nitrogen dioxide was measured during the Atmospheric Environment Service STRATOPROBE projects in August of 1975 and 1976. Vertical profiles of NO2 are determined by measuring the NO2 absorption of sunlight from a balloon platform during sunrise and sunset and inverting the absorption curves. A total of four sunrise/sunset pairs of observations were obtained from balloon flights of August 10 and 17, 1975 and August 19 and 28, 1976. The measurements show significant stability of the NO2 profile from flight to flight with variations of less than 15% between individual profiles. The average NO2 concentration at sunset was found to increase from about 0.3 ppbv at 10 km to 10 ppbv at 35 km. At sunrise the concentrations increase from 0.2 ppbv at 10 km to 5 ppbv at 35 km.

A mechanism for the conversion of stratospheric N20 S to HNO 3 by the reaction of N20 S reaction R3. with aqueous aerosol in the winter polar stratosphere is proposed to explain the observed deficit amounts of dinitrogen pentoxide and excess amounts of nitric acid compared to the results of calculations based on current gas phase chemistry. The presence of large numbers of aqueous aerosols in the winter polar vortex is associated with the formation of polar stratospheric clouds. An estimate of the rate of the conversion reaction leads to a time constant of about 18 days; model calculations indicate that a conversion process with this time constant is sufficient to convert about 4 ppbv of NO 2 into HNO 3 in the polar winter vortex.

Measurements of ozone, water vapour, nitric acid and nitrogen dioxide taken during the STRATOPROBE flight of October 23, 1980 from Palestine Texas at 32øN are presented. The measured ratio of HN03 to NO2 is in good agreement with that of a one dimensional model using current photochemistry. The measured ratio is used to infer •proxy" hydroxyl densities. These OH densities are very low below 25 km, in agreement with the findings of earlier flights.

It has been more than 20 years since the Brewer reference triad was established by Environment Canada at Toronto. The triad serves as a reference for traveling standard instruments that are used to calibrate Brewer spectrophotometers around the world. The members of the triad are calibrated on a regular basis at Mauna Loa, Hawaii. Regular tests made with an internal quartz halogen lamp make it possible to track the instrument response between the calibrations. A new analysis of available column ozone data records indicates that the uncertainty in the daily values derived from each instrument is approximately 0.6%. The random errors of individual observations are within ±1% for 90% of all measurements. Sources of potential errors in the individual Brewer measurements as well as quality control tools are also discussed.

During winter/spring 96/97 ozone levels over the Eureka NDSC observatory (80øN,86øW) were measured using a lidar, sondes, and a Brewer spectrophotometer. Column C10 measurements were also made using an FTIR system. Measurements show that lower stratospheric ozone mixing ratios decreased rapidly between mid-February and late-March though the ozone mixing ratio losses appear to have been less than for the 95/96 season. Elevated column amounts of C10 were found to be present over Eureka until late March. loss to occur, stratospheric chlorine compounds must be converted from inert reservoir forms into active forms (chlorine activation). In the presence of sunlight, these active chlorine compounds will engage in catalytic ozone destruction. Enhanced levels of C10 are indicative of this process [$alawitch et al., 1993]. Chlorine activation is believed to occur via heterogeneous chemical reactions on stratospheric HNOa/H20/H2SO4 aerosols (with various fractional compositions and phases) at temperatures below around 195 K [Kawa et al., 1997]. At temperatures approaching 195 K, heterogeneous reaction probabilities associated with the "background" mainly sulphate/water aerosol greatly increase, leading to significant chlorine activation [Del Negro et al., 1997]. At temperatures below around 193 K, the aerosol may grow significantly via increased absorption of HNOa [Carslaw et al., 1994] leading to polar stratospheric cloud (PSC) formation. PSCs not only engage in chlorine activation, but they also provide a means whereby

The first measurements of the spectral flux on a homontal surface, limb brighiness and apparent surface brightness •th the NASA ER-2 research aircraft were made during the Stratospherie Photochemistry, Aerosol and Dynamics Expedition (SPADE) of the NASA High-S• Research Program. Results from the May, 1993 campaign are presented. J-values for the production of O(lD) from the photodissociation of ozone and the photodissociation rate of NO2 to form NO have been detemained and are compared to the currently used, modelled values. The instrument and its installation on-board the ER-2 are described elsewhere [McElroy, this issue]. The inclusion of the Composition and Photodissociative Flux Measurement on the aircraft is intended to address two needs. One is for actual experimental measurements of stratospheric chemical composition and light flux levels, and the other is to provide sensitive diagnostic information about the light-scattering process for validation and possible improvement of the scattering models used for photochemical modelling. Data analysis The radiation environment of the aircraft is characterized by measurements made of the direct solar irradiance on a nearlyhorizontal surface, the surface brightness of the horizon and the a•t surface brighiness below the aircraft. The collected data 4. Spectra are converted to physical units using ground-based calibration data from intensity reference lamps. 5. Separately-processed UV and visible observations for each field are filtered and blended into one continuous spectrum. 6. The direct-lxmm spectral irradiance is determined by applying a cosine crnrection to the data taken on the horizontal diffuser. 7. Spectra are convolved with various weighting vectors to produce band integrals, constituent amounts and J-values. 8. The J-value contributions from each field measured are combined to produce total estimated J-values.

ER-2 aircraft observations of OH and HO2 concentrations in the upper troposphere during the NASA/STRAT campaign are interpreted using a photochemical model constrained by local observations of 03, H20, NO, CO, hydrocarbons, albedo and overhead ozone column. We find that the reaction O(•D) + H20 is minor compared to acetone photolysis as a primary source of HOx (= OH + peroxy radicals) in the upper troposphere. Calculations using a diel steady state model agree with observed HOx concentrations in the lower stratosphere and, for some flights, in the upper troposphere. However, for other flights in the upper troposphere, the steady state model underestimates observations by a factor of 2 or more. These model underestimates are found to be related to a recent (< 1 week) convective origin of the air. By conducting time-dependent model calculations along air trajectories determined for the STRAT flights, we show that convective injection of CH3OOH and H202 from the boundary layer to the upper troposphere could resolve the discrepancy. These injections of HOx reservoirs cause large HOx increases in the tropical upper troposphere for over a week downwind of the convective activity. We propose that this mechanism provides a major source of HOx in the upper troposphere. Simultaneous measurements of peroxides, formaldehyde and acetone along with OH and HO2 are needed to test our hypothesis.

The 2004 Canadian Arctic ACE Validation Campaign was conducted to provide correlative data for validating measurements from the Atmospheric Chemistry Experiment (ACE) satellite mission. These measurements were made at Eureka, Nunavut during polar springtime 2004. Six groundbased instruments were operated during the intensive phase of the campaign and ozonesondes and radiosondes were flown. During this time, ACE-FTS and ACE-MAESTRO were performing solar-occultation measurements over the Canadian Arctic. We report the first comparisons between campaign measurements and those from ACE, focusing on O 3 , NO 2 and temperature. Initial mean O 3 profiles from ACE-FTS and ACE-MAESTRO agree to within 20% between 10 and 30 km, and the NO 2 profiles agree to within 40% between 17 and 40 km, which is within the standard deviations. The ACE-FTS temperature profiles agree to better than 2.5 K with the radiosonde temperatures from 10 to 32 km and with the lidar temperatures from 17 to 45 km.