David Tarasick | Environment Canada (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.
Geophysical Research Letters, 2015
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...
Following the success of the Sunphotometer Earth Atmosphere Measurement (SPEAM-I) experiment, a m... more Following the success of the Sunphotometer Earth Atmosphere Measurement (SPEAM-I) experiment, a more involved experiment was developed to fly as part of the second set of Canadian Experiments (CANEX-2) which will fly on the US Space Shuttle in the fall of 1992. The instrument complement includes an IBM-PC compatible control computer, a hand-held diode array spectrophotometer, and an interference-filter, limb imaging radiometer for the measurement of the atmospheric airglow. The hand-held spectrometer will measure nitrogen dioxide, ozone and aerosols. The limb imaging radiometer will observe emissions from the O2(1 DELTA) and O2(1 SIGMA) airglow bands. Only the spectrophotometer will be discussed here.
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...
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
Planetary and Space Science, 1990
The Astrophysical Journal, 1983
Journal of Geophysical Research, 1993
Journal of Geophysical Research, 2008
Journal of Geophysical Research, 1992
Journal of Atmospheric and Solar-Terrestrial Physics, 1997
Geophysical Research Letters, 1994
Geophysical Research Letters, 1993
Atmospheric Chemistry and Physics, 2002
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
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.
Geophysical Research Letters, 2015
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...
Following the success of the Sunphotometer Earth Atmosphere Measurement (SPEAM-I) experiment, a m... more Following the success of the Sunphotometer Earth Atmosphere Measurement (SPEAM-I) experiment, a more involved experiment was developed to fly as part of the second set of Canadian Experiments (CANEX-2) which will fly on the US Space Shuttle in the fall of 1992. The instrument complement includes an IBM-PC compatible control computer, a hand-held diode array spectrophotometer, and an interference-filter, limb imaging radiometer for the measurement of the atmospheric airglow. The hand-held spectrometer will measure nitrogen dioxide, ozone and aerosols. The limb imaging radiometer will observe emissions from the O2(1 DELTA) and O2(1 SIGMA) airglow bands. Only the spectrophotometer will be discussed here.
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...
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
Planetary and Space Science, 1990
The Astrophysical Journal, 1983
Journal of Geophysical Research, 1993
Journal of Geophysical Research, 2008
Journal of Geophysical Research, 1992
Journal of Atmospheric and Solar-Terrestrial Physics, 1997
Geophysical Research Letters, 1994
Geophysical Research Letters, 1993
Atmospheric Chemistry and Physics, 2002
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