Microphysical modeling of the 1999–2000 Arctic winter: 1. Polar stratospheric clouds, denitrification, and dehydration

Drdla, K.; Schoeberl, M. R.; Browell, Edward V.

doi:10.1029/2001jd000782

Cited by 56 publications

(159 citation statements)

References 67 publications

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“…Subsequent modelling studies have indicated that the sedimentation of these large NAT particles was capable of causing denitrification comparable to that observed Drdla et al, 2002). Mann et al (2003) used the microphysical DLAPSE model to demonstrate that this mechanism may have caused denitrification in a number of other cold Arctic winters of the 1990s.…”

Section: S Davies Et Al: Model and Mipas-observed Arctic Denitrificmentioning

confidence: 99%

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

et al. 2006

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Abstract. Observations of gas-phase HNO 3 and N 2 O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E) were made during the cold Arctic winter of 2002/2003. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation) microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NO y and N 2 O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in midDecember 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.

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Section: S Davies Et Al: Model and Mipas-observed Arctic Denitrificmentioning

confidence: 99%

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

et al. 2006

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“…Large nitric acidcontaining particles (10 to 20 µm diameter) at low number concentrations (between 10 −5 and 10 −3 cm −3 ) were measured by the NOAA NO y instrument aboard the NASA ER-2 aircraft in the 1999/2000 winter Arctic vortex and have generally been inferred to be NAT (Fahey et al, 2001;Northway et al, 2002a). Previous model calculations Drdla et al, 2002) show that meteorological conditions in the 1999/2000 Arctic vortex allowed NAT particles to grow to the very large sizes that were observed. These large particles can very efficiently denitrify the lower stratosphere on the timescale of a few days (Fahey et al, 2001;Mann et al, 2002;Northway et al, 2002b;Davies et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Factors controlling Arctic denitrification in cold winters of the 1990s

et al. 2003

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Abstract. Denitrification of the Arctic winter stratosphere has been calculated using a 3-D microphysical model for the winters 1994/95, 1995/96, 1996/97 and 1999/2000. Denitrification is assumed to occur through the sedimentation of low number concentrations of large nitric acid trihydrate (NAT) particles (as inferred by e.g. Fahey et al., 2001). We examine whether the meteorological conditions that allowed particles to grow to the very large sizes observed in 1999/2000 also occurred in the other cold winters. The results show that winter 1999/2000 had conditions that were optimum for denitrification by large NAT particles, which are a deep concentric NAT area and vortex. Under these conditions, NAT particles can circulate in the NAT-supersaturated air for several days, reaching several micrometres in radius and leading to a high downward flux of nitric acid. The other winters had shorter periods with optimum conditions for denitrification. However, we find that NAT particles could have grown to large sizes in all of these winters and could have caused significant denitrification. We define the quantity "closedflow area" (the fraction of the NAT area in which air parcel trajectories can form closed loops) and show that it is a very useful indicator of possible denitrification. We find that even with a constant NAT nucleation rate throughout the NAT area, the average NAT number concentration and size can vary by up to a factor of 10 in response to this meteorological quantity. These changes in particle properties account for a high degree of variability in denitrification between the different winters. This large meteorologically induced variability in denitrification rate needs to be compared with that which could arise from a variable nucleation rate of NAT particles, which remains an uncertain quantity in models. Sensitivity studies show that although denitrification was likely approaching asymptotic minimum values throughout much of the 1999/2000 vortex, decreases in the volume-averaged nucleation rate would have substantially reduced the denitrification.

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“…Stratospheric variations in aerosol optical depth can significantly affect heterogeneous chemistry that leads to ozone depletion because particle surface areas are directly proportional to the optical depth. Below we consider how the continuous presence of volcanic cloudy-like conditions in the Arctic can affect springtime ozone loss processes (13)(14)(15)(16)(17)(18) in a cold year such as the winter of 1999-2000.…”

Section: Volcanic Aerosol Effectsmentioning

confidence: 99%

“…We increased sulfate volume mixing ratio (29) in the model from 0.17 ppbv (nonvolcanic) to 20 ppbv (volcanic) to account for volcanic aerosol effects on ozone. We used the Integrated MicroPhysics and Aerosol Chemistry on Trajectories (IMPACT) model in a quasi-three-dimensional mode (15,16) to obtain the results shown. Nearly 3,000 initial points were distributed evenly (in both horizontal and vertical directions) inside the Arctic vortex on Jan. 15, 2000 between Ϸ450 and 700 K surface.…”

Section: Volcanic Aerosol Effectsmentioning

confidence: 99%

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Arctic “ozone hole” in a cold volcanic stratosphere

Tabazadeh

Drdla

Schoeberl

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Optical depth records indicate that volcanic aerosols from major eruptions often produce clouds that have greater surface area than typical Arctic polar stratospheric clouds (PSCs). A trajectory cloudchemistry model is used to study how volcanic aerosols could affect springtime Arctic ozone loss processes, such as chlorine activation and denitrification, in a cold winter within the current range of natural variability. Several studies indicate that severe denitrification can increase Arctic ozone loss by up to 30%. We show large PSC particles that cause denitrification in a nonvolcanic stratosphere cannot efficiently form in a volcanic environment. However, volcanic aerosols, when present at low altitudes, where Arctic PSCs cannot form, can extend the vertical range of chemical ozone loss in the lower stratosphere. Chemical processing on volcanic aerosols over a 10-km altitude range could increase the current levels of springtime column ozone loss by up to 70% independent of denitrification. Climate models predict that the lower stratosphere is cooling as a result of greenhouse gas built-up in the troposphere. The magnitude of column ozone loss calculated here for the 1999 -2000 Arctic winter, in an assumed volcanic state, is similar to that projected for a colder future nonvolcanic stratosphere in the 2010 decade.E ruptions with a volcanic explosivity index (VEI) of 4 or higher produce significant stratospheric injections (1, 2). Sulfur dioxide (2), the most important atmospheric component of volcanic emissions, is converted into sulfate aerosols after injection into the stratosphere. More than 100 eruptions with VEIs Ն 4 are thought to have occurred in the past 500 years (1). However, only about half of all large eruptions are sulfur-rich (2, 3). Both the 1982 El Chichon (VEI ϭ 4) (4) and 1991 Mt. Pinatubo (VEI ϭ 5) (5) eruptions were sulfur-rich, producing volcanic clouds in the stratosphere that lasted for a number of years (6). On the other hand, the relatively sulfur-poor eruption of Mt. St. Helens (VEI ϭ 5) (2, 7) in 1980 contributed very little sulfate mass to the stratospheric aerosol layer (6). The fact that Mt. St. Helens' plume was emitted at an angle also reduced the amount of possible stratospheric injections by this volcano. Nevertheless, large sulfate-rich eruptions are common (6). Therefore, it is important to understand to what extent these eruptions could affect the Arctic ozone layer in the next 30 years or so, while anthropogenic chlorine levels are still sufficiently high [Ϸ3 parts per billion in volume (ppbv)] to cause severe ozone depletion (8, 9).Model simulations (10) have shown that the early rapid growth of the Antarctic ''ozone hole'' in the early 1980s may have been influenced (in part) by a number of large volcanic eruptions. The goal of this study is to explore how a large eruption could affect Arctic ozone loss processes, such as chlorine activation and denitrification, in a cold year within the current range of natural variability. It is projected that the Arctic climate may be ...

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Microphysical modeling of the 1999–2000 Arctic winter: 1. Polar stratospheric clouds, denitrification, and dehydration

Cited by 56 publications

References 67 publications

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

Factors controlling Arctic denitrification in cold winters of the 1990s

Arctic “ozone hole” in a cold volcanic stratosphere

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