David Tarasick - Profile on Academia.edu (original) (raw)

Papers by David Tarasick

We use the GEOS-Chem global chemical transport model and its adjoint, together with satellite and... more We use the GEOS-Chem global chemical transport model and its adjoint, together with satellite and in situ observation of tropospheric ozone, to assess the impact of transport of pollution from midlatitudes on the abundance of ozone in the Arctic. The model reproduces well the seasonal cycle in the abundances of PAN and ozone as measured at the surface at Alert. However, relative to ozonesonde measurements, the model overestimates ozone in the middle and upper troposphere in spring, while it underestimates ozone in summer. We examine the information gained by assimilating tropospheric ozone profile retrievals from the Tropospheric Emission Spectrometer (TES) satellite instrument at midlatitudes to provide an improved boundary condition for ozone at midlatitudes to better quantify the transport of ozone into the Arctic. We find that the assimilation corrects model biases relative to sondes in the Arctic free troposphere, implying an increase in the net northward ozone flux. We also use the adjoint model to conduct a detailed analysis of the sensitivity of the modeled ozone abundances in the Arctic to midlatitude precursor emissions.

Revisiting the evidence of increasing springtime ozone mixing ratios in the free troposphere over western North America

Geophysical Research Letters, 2015

Interactive comment on "Surface ozone depletion episodes in the Arctic and Antarctic from historical ozonesonde records" by D. W. Tarasick and J. W. Bottenheim

We thank the referee for his critique and helpful suggestions. We have amended the abstract to re... more We thank the referee for his critique and helpful suggestions. We have amended the abstract to refer only to "average springtime surface temperatures", rather than "surface meteorology"; we agree this is more reflective of our results. We have also amended the discussion and conclusion somewhat to better represent this, too. However, we do conclude that both surface temperatures and lower atmospheric stability play a role, and these are both part of the surface meteorology. 1) We have included the station latitude. We note in the text that all are close to sea ice except for Edmonton and Goose Bay. The resolution of the reported Syowa data is so poor in the lower troposphere that it is severely biased toward not finding depletion events, so we feel that it is not appropriate to compare it with the ECC data. S286

The ()ZONE WATCH, initiated in March, 1992, is a weekly bulletin describing the state of the ozon... more The ()ZONE WATCH, initiated in March, 1992, is a weekly bulletin describing the state of the ozone layer over Canada. The UV-B advisory program, which started in May, 1992, produces daily forecasts of clear-sky UV-B radiation. The forecast procedure uses daily ozone mea.surements from the eight-station monitoring network, the output from the Canadian operational forecast model and a UV-B algorithm based on three years of spectral UV-B measurements with the Brewer spectrophotometer. Toronto decreased by ahout 4% during the 1980's (Kerr, 1991). Com-parison of total ozone measurements from recent years to those made before 1980 shows that the ozone decrease is due primarily to an 8% reduction during the winter/spring season, a time when total ozone is at its annual maximum. I)espite this loss, ozone values during win-ter and spring remain significantly higher than those values during fall, a tirne of year which has shown little or no loss. The study also illustrated that the nature...

A review of the O2 (a 1Delta-g) and O2 (b 1Sigma-g(+)) airglow emissions

Advances in Space Research

The state of knowledge of the IR atmospheric and the atmospheric emission band systems of molecul... more The state of knowledge of the IR atmospheric and the atmospheric emission band systems of molecular oxygen is reviewed. These emissions are present in the nightglow, the twilight, and the dayglow. The available observations are collected in a data base model with the capability of displaying and manipulating the data in a number of ways. The observational data base is used to examine the state of theoretical understanding of the atmospheric photochemistry of these emissions. These emissions are of interest to future space experiments - in particular the WINDII and HRDI experiments on the Upper Atmospheric Research Satellite (UARS) - which will use them to measure state parameters of the middle atmosphere such as temperature and wind velocity. While the IR Atmospheric system in the dayglow is both well characterized observationally and well understood theoretically, the other emissions are neither, suggesting an immediate need for additional work in this area to support UARS.

The interaction of gravity waves and airglow emissions is explored with a view to elucidating the... more The interaction of gravity waves and airglow emissions is explored with a view to elucidating the observable effects of such waves. The results obtained are applicable to ground-based photometric observations, where the total line-of-sight emission, at an arbitrary viewing angle, is measured. Explicit relations are developed for the dependence of the magnitude and phase of the observable parameter eta, the ratio of brightness fluctuations to temperature fluctuations. Both magnitude and phase depend on dynamical parameters (wavelength and period), the viewing angle at which observations are made, chemical parameters related to the temperature dependence of the reaction chemistry, and the number of bodies involved in the reaction. Methods of distinguishing between evanescent and internal gravity wave modes, and determining the vertical wavelength and direction of propagation for internal modes, are proposed. The specific cases of O2(b(sup 1)sigma) and OH airglow are examined in detail...

RIALTO (Routine Inflight Assessment of Lower Tropospheric Oxidants)

In spite of large advances in knowledge of tropospheric chemistry in the latter part of the 20th ... more In spite of large advances in knowledge of tropospheric chemistry in the latter part of the 20th century, the database of routine observations is embarrassingly sparse. The large majority of observations are limited to surface measurements of only a few species, and most of those are in urban/suburban locations. Regularly obtained vertical profile data are limited to ozone from sondes or ozone DIALs. Routine observations from space promise to improve the situation but actual profile information will still be hard to obtain. A major obstacle to a routine measurement program in the vertical is expense, since it requires lifting an observing system to several altitudes above ground, and then having it return to ground level after performing the desired measurements. One solution to this problem is to make use of existing infrastructure, i.e. to mount measurement equipment onboard aircraft already in service. This approach has been pioneered by such programs as MOZAIC and CARIBIC, where...

Planetary and Space Science, 1987

We develop here theoretical relations between fluctuations of airglow brightness, fluctuations of... more We develop here theoretical relations between fluctuations of airglow brightness, fluctuations of temperature as revealed by airglow, and the atmospheric gravity waves that are believed to cause these fluctuations. We note and account for differences between our relations and those obtained by Krassovsky (1972, Ann. Geophys. 28, 739) and Weinstock (1978, J. geophys. Res. 83, X75), correctiug both of the latter in the process. We explicitly repudiate the need for a nonlinear treatment of O#&) emissions as it was asserted by Weinstock, one aspect of the nonlinear treatment he gave, and the conclusions he drew from that treatment, including, inter a/in, the conclusion that temperature fluctuations carry more meaning as a diagnostic than do brightness fluctuations. Instead, we note the dependence of both types of fluctuation on variable gravity-wave parameters, which dependence can be applied to the study of gravity waves via airglow or of airglow via gravity waves. As a first step, we note the ability of the present analysis to account for certain observations of OH and O,('Z#) emissions that have been, until now, inadequately or incorrectly explained, and we stress the importance of the proper measurement of parameters such as wave frequency and propagation speed if our own tentative explanations are to be put to the test and further progress is to be made.

Planetary and Space Science, 1990

The influence of gravity waves on airglow emissions is explored with a view to elucidating the ob... more The influence of gravity waves on airglow emissions is explored with a view to elucidating the observable effects of such waves. The results obtained are applicable to ground-based photometric observations, where the total line-of-sight emission, at an arbitrary zenith angle, is measured. Explicit relations are developed for the dependence of the magnitude and phase of the observable parameter q, the ratio of brightness fluctuations to temperature fluctuations. Both magnitude and phase depend on dynamical parameters (wavelength and period), the zenith angle at which observations are made, and a chemical parameter which is specific to the reaction chemistry. Methods of (i) distinguishing between evanescent and internal gravity wave modes, and (ii) determining the vertical wavelength and sense of vertical propagation for internal modes, are proposed. The former may be of considerable importance observationaliy, since the effects of evanesxmt and internal modes on airglow are quite different. The latter is a measurement that is typically difficult to make directly.

The Astrophysical Journal, 1983

Journal of Geophysical Research, 1993

An attempt is made to clarify the role that may be played by nonlinearities in airglow fluctuatio... more An attempt is made to clarify the role that may be played by nonlinearities in airglow fluctuations induced by atmospheric gravity waves. species being assumed to move together, at the relevant levels), not because of local compression or dilation. But, since both [brightness and measured temperature]

Journal of Geophysical Research, 2008

Journal of Geophysical Research, 1992

The theory of Hines and Tarasick (1987) for the effects of gravity waves on airglow emissions is ... more The theory of Hines and Tarasick (1987) for the effects of gravity waves on airglow emissions is extended to consider more complex airglow chemistries, including multiple and multiple-step production mechanisms, quenching, and other loss processes. Relations for the dependence of ,/, the ratio of brightness to temperature fluctuations, on emission chemistry are presented in a generalized form which is readily applicable to other emissions. The specific case of O2(b!Z •) airglow is examined in detail for three different proposed chemical production mechanisms. Loss mechanisms are also considered; quenching is found to be important to predictions of r/. The results obtained are compared with the very limited set of published observations of gravity waves in O2(b l Z• ) airglow.

Journal of Atmospheric and Solar-Terrestrial Physics, 1997

The theory of airglow fluctuations observed from the ground is often advanced by numerical integr... more The theory of airglow fluctuations observed from the ground is often advanced by numerical integration of certain parameter combinations through the depth of a model emitting layer. Practical requirements oblige the layer to be truncated above, if not also below, the heights of greatest emission intensity. If the analysis is of an Eulerian type, this truncation requires that edge effects be taken into account if the results are to represent the true situation properly, but no such correction is normally required if the analysis is of a Lagrangian type. The nature of the correction is discussed both for thin layers and for thick layers, and the distinction between the Eulerian and Lagrangian approaches is clarified. The theory for limb-viewing measurements made from spacecraft is somewhat different and is touched upon briefly. Copyright 0 1996 Elsevier Science Ltd 321

Geophysical Research Letters, 1994

There is currently much interest in fluctuations of airglow emissions caused by atmospheric gravi... more There is currently much interest in fluctuations of airglow emissions caused by atmospheric gravity waves. The fluctuations of brightness tend to be found in phase (or occasionally in antiphase) with the fluctuations of measured temperature, whereas current theory tends to anticipate substantial phase differences. We suggest here that the discrepancy results from failure of the common theoretical assumption that the relevant gravity waves are dominated by a single upgoing component: that, instead, there is an accompanying downgoing component of comparable magnitude, produced by reflection. In the case of total reflection, simple, steady state chemistry and vertical viewing, the phase difference is necessarily zero (or 180ø).

Geophysical Research Letters, 1993

Measurements of ozone made over Canada during the first four months of 1993 indicate that total o... more Measurements of ozone made over Canada during the first four months of 1993 indicate that total ozone has been about 11 to 17 % below normal. These low values were recorded, without exception, at all nine of the Canadian mid-latitude ground-based monitoring sites. Record low averages for the period from January to April were measured at three of the four mid-latitude stations where measurements have been made since the 1960's. Comparison of January to April, 1993 ozonesonde profile measurements with those from earlier years indicates that the ozone deficit is in the lower stratosphere between 40 and 200 mb, the same altitudes where aerosols from the Mount Pinatubo volcanic eruption have been observed. The peak loss is 30% at 100 mb (16 Km). I I Toronto 196'0-1 b93 _ ß ß ß ß ß ß ß ß ß ß ß ß

Atmospheric Chemistry and Physics, 2002

Episodes of ozone depletion in the lowermost Arctic atmosphere (0-2 km) at polar sunrise have bee... more Episodes of ozone depletion in the lowermost Arctic atmosphere (0-2 km) at polar sunrise have been intensively studied at Alert, Canada, and are thought to result from catalytic reactions involving bromine. Recent observations of high concentrations of tropospheric BrO over large areas of the Arctic and Antarctic suggest that such depletion events should also be seen by ozonesondes at other polar stations. An examination of historical ozonesonde records shows that such events occur frequently at Alert, Eureka and Resolute, but much less frequently at Churchill and at other stations. The differences appear to be related to differences in average springtime surface temperatures. The long record at Resolute shows depletions since 1966, but with an increase in their frequency over the period 1966-2000 of 0.66 ± 0.59% per year (95% confidence limits), explaining the apparent increase of Hg in Arctic biota in recent times.

Atmosphere-Ocean, 2008

An improved understanding of the global tropospheric ozone budget has recently become of great in... more An improved understanding of the global tropospheric ozone budget has recently become of great interest, both in Canada and elsewhere. Improvements in both modelling and measurement have made it possible for weather centres to begin to forecast air quality using numerical weather prediction models. Despite substantial progress, there are many open questions regarding tropospheric ozone photochemistry, long-range transport and the importance of the stratospheric source; this remains an area of very active research. Since ozone in association with particulate matter causes respiratory problems in humans, trends and forecasting of future surface ozone levels are also of great importance. The current status of measurement and modelling, as well as the current understanding of tropospheric ozone budgets and trends, are reviewed, with an emphasis on Canada within the global context.

A Study of Air Pollutants over the UAE

The first ever campaign of observing air pollutants over the UAE began in 2006 with a couple of b... more The first ever campaign of observing air pollutants over the UAE began in 2006 with a couple of balloon flights carrying ECC ozonesondes to measure the vertical profiles of ozone. The chromatography of the collected air samples to measure concentrations of the Volatile Oxy-genated Compounds (VOCs) began a year later. The purpose of this campaign was to study characteristics of

Advances in Space Research, 1993

The state of knowledge of the Infrared Atmospheric and the Atmospheric emission band systems of m... more The state of knowledge of the Infrared Atmospheric and the Atmospheric emission band systems of molecular oxygen is reviewed. These emissions are present in the nightglow, the twilight, and the dayglosv. The available observations are collected in a data base model with the capability of displaying and manipulating the data in a number of ways. The observational data base is used to examine the state of theoretical understanding of the atmospheric photochemistry of these emissions. These emissions are of interest to future space experimentsin particular the WINDII and IIRDI experiments on the Upper Atmospheric Research Satellitewhich will use them to measure state parameters of the middle atmosphere such as temperature and wind velocity. While the IR Atmospheric system in the dayglow is both well characterized observationally and well understood theoretically, the other emissions are neither, suggesting an immediate need for additional work in this area to support UARS.