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Zurek, R. W.

Publications and source records attributed to Zurek, R. W..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Evidence for Arctic Ozone Depletion in Late February and early March 1994

Significant chemical ozone (O3 ) loss in the 1993-94 Arctic winter occurred mainly during an unusually late cold spell of approximately 10 days in late Feb/early Mar. Over the 30 d period studied (including the cold spell), observed vortex-averaged O3 at 465 K (approximately 40 hPa) decreased by approximately 10%. New three-dimensional, diabatic trajectory calculations show that this observed decrease represents only about half of the net chemical loss (approximately 20%) during the 30 day period. The resupply of lower stratospheric O3 by transport in Feb 1994 was considerably greater than in 1993, when transport masked only about a quarter of the chemical loss in Feb/Mar. The net estimated chemical loss over 30 days in 1994 was comparable to that over the same 30 days in 1993, but mainly occurred at a faster rate during the brief cold spell. These results highlight the impact of Arctic interannual variability on the relative roles of chemistry and dynamics in O3 evolution during recent Arctic winters.

Manney, G. L.↗
NASA NTRS1995

Lagrangian Transport Calculations Using UARS Data: Ozone - Part 2

Trajectory calculations are used to examine ozone transport in the polar winter stratosphere during periods of the Upper Atmosphere Research Satellite (UARS) observations. The value of these calculations for determining mass transport was demonstrated previously using UARS observations of long-lived tracers, In the middle stratosphere, the overall ozone behavior observed by the Microwave Limb Sounder in the polar vortex is reproduced by this purely dynamical model. Calculations show the evolution of ozone in the lower stratosphere during early winter to be dominated by dynamics in December 1992 in the Arctic. Calculations for June 1992 in the Antarctic show evidence of chemical ozone destruction and indicate that approx. 50% of the chemical destruction may be masked by dynamical effects, mainly diabatic descent, which bring higher ozone into the lower-stratospheric vortex. Estimating differences between calculated and observed fields suggests that dynamical changes masked approx. 20% - 35% of chemical ozone loss during late February and early March 1993 in the Arctic. In the Antarctic late winter, in late August and early September 1992, below approx. 520 K, the evolution of vortex-averaged ozone is entirely dominated by chemical effects; above this level, however, chemical ozone depletion can be partially or completely masked by dynamical effects. Our calculations for 1992 showed that chemical loss was nearly completely compensated by increases due to diabatic descent at 655 K.

Manney, Gloria L.↗
NASA NTRS1995

Evolution of microwave limb sounder ozone and the polar vortex during winter

The evolution of polar ozone observed by the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) is described for the northern hemisphere (NH) winters of 1991/1992, 1992/1993, and 1993/1994 and the southern hemisphere (SH) winters of 1992 and 1993. Imterannual and interhemispheric variability in polar ozone evolution are closely related to differences in the polar vortex and to the frequency, duration and strength of stratospheric sudden warmings. Ozone in the midstratospheric vortices increases during the winter, with largest increases associated with stratospheric warmings and a much larger increase in the NH than in the SH. A smaller NH increase was observed in 1993/1994, when the middle stratospheric vortex was stronger. During strong stratospheric warmings in the NH, the upper stratospheric vortex may be so much eroded that it presents little barrier to poleward transport; in contrast, the SH vortex remains strong throughout the stratosphere during wintertime warmings, and ozone increases only below the mixing ratio peak, due to enhanced diabatic descent. Ozone mixing ratios decrease rapidly in the lower stratosphere in both SH late winters, as expected from chemical destruction due to enhanced reactive chlorine. The interplay between dynamics and chemistry is more complex in the NH lower stratosphere and interannual variability is greater. Evidence has previously been shown for chemical ozone destruction in the 1991/1992 and 1992/1993 winters. We show here evidence suggesting some chemical destruction in late February and early March 1994. In the NH late winter lower stratosphere the pattern of high-ozone values (typical of the vortex) seen in mid-latitudes is related to the strength of the lower-stratospheric vortex, with the largest areal extent of high ozone outside the vortex in 1994, when the lower stratospheric vortex is relatively weak, and the least extent in 1993 when the lower stratospheric vortex is strongest.

Manney, G. L.↗
NASA NTRS1995

Comparison of UKMO and NMC Stratospheric Analyses During Northern and Southern Winter

Instruments on board the Upper Atmosphere Research Satellite have been measuring stratospheric temperatures, winds, and constituent species since September 1991. Among the correlative data that aid in interpreting this data are two sets of global meteorological analyses. Meteorological data from the United Kingdom Meteorological Office (UKMO), and the US National Meteorological Center (NMC) are discussed.

arctic antarctic atmosphere research satellite met↗
NASA NTRS1995

Arctic Ozone Depletion Observed by UARS MLS During the 1994-95 Winter

The Earth's northern hemisphere lower stratosphere was unusually cold in December 1995 and January 1995. Temperatures low enough for polar stratospheric cloud formation persisted until mid-March 1995, and the polar vortex was exceptionally strong throughout the winter. Previous and current Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) measurements indicating ozone depletion are given.

arctic↗
NASA NTRS1994

The anomalous Arctic lower stratospheric polar vortex of 1992-1993

Potential vorticity (PV) gradients defining the lower stratospheric vortex during the 1992-1993 winter were anomalously strong and persistent compared to those during the last 16 Arctic winters. For approximately equal to 3 months PV gradients were closer to typical Antarctic values than to most Arctic values. Air motion diagnostics computed for 3-dimensional air parcels confirm that the 1992-1993 Arctic lower stratospheric vortex was substantially more isolated than is typical. Such isolation will delay and reduce the export of the higher ozone typical of the winter lower stratospheric vortex to mid-latitudes. This may have contributed to the record-low total ozone amounts observed in northern mid-latitudes in 1993.

Manney, G. L.↗
NASA NTRS1994

On the motion of air through the stratospheric polar vortex

Trajectory calculations using horizontal winds from the U.K. Meteorological Office data assimilation system and vertical velocities from a radiation calculation are used to simulate the three-dimensional motion of air through the stratospheric polar vortex for Northern Hemisphere (NH) and Southern Hemisphere (SH) winters since the launch of the Upper Atmosphere Research Satellite (UARS). Throughout the winter, air from the upper stratosphere moves poleward and descends into the middle stratosphere. In the SH lower to middle stratosphere, strongest descent occurs near the edge of the polar vortex, with that edge defined by mixing characteristics. The NH shows a similar pattern in late winter, but in early winter strongest descent is near the center of the vortex, except when wave activity is particularly strong. Strong barriers to latitudinal mixing exist above about 420 K throughout the winter. Below this, the polar night jet is weak in early winter, so air descending below that level mixes between polar and middle latitudes. In late winter, parcels descend less and the polar night jet moves downward, so there is less latitudinal mixing. The degree of mixing in the lower stratosphere thus depends strongly on the position and evolution of the polar night jet and on the amount of descent experienced by the air parcels; these characteristics show considerable interannual variability in both hemispheres. The computed trajectories provide a three-dimensional picture of air motion during the final warming. Large tongues of air are drawn off the vortex and stretched into increasingly long and narrow tongues extending into low latitudes. This vortex erosion process proceeds more rapidly in the NH than in he SH. In the lower stratosphere, the majority of air parcels remain confined within a lingering region of strong potential vorticity gradients into December in the SH and April in the NH, well after the vortex breaks up in the midstratosphere.

Manney, G. L.↗
NASA NTRS1994

Stratospheric warmings during February and March 1993

Two stratospheric warmings during February and March 1993 are described using United Kingdom Meteorological Office (UKMO) analyses, calculated potential vorticity (PV) and diabetic heating, and N2O observed by the Cryogenic Limb Array Etalon Spectrometer (CLAES) instrument on the Upper Atmosphere Research Satellite (UARS). The first warming affected temperatures over a larger region, while the second produced a larger region of reversed zonal winds. Tilted baroclinic zones formed in the temperature field, and the polar vortex tilted westward with height. Narrow tongues of high PV and low N2O were drawn off the polar vortex, and irreversibly mixed. Tongues of material were drawn from low latitudes into the region between the polar vortex and the anticyclone; diabatic descent was also strongest in this region. Increased N2O over a broad region near the edge of the polar vortex indicates the importance of horizontal transport. N2O decreased in the vortex, consistent with enhanced diabatic descent during the warmings.

Manney, G. L.↗
NASA NTRS1994

Stratospheric Warmings During February and March 1993

Two stratospheric warnings during February and March 1993 are described using UKMO analyses, calculated PV and diabatic heating, and N2O observed by the CLAES instrument on the UARS. The first warming affected temperatures over a larger region. while the second produced a larger region of reversed zonal winds. Tilted baroclinic zones formed in the temperature field, and the polar vortex tilted westward with height. Narrow tongues of high PV and low N2O were drawn off the polar vortex, and irreversibly mixed. Tongues of material were drawn from low latitudes into the region between the polar vortex and the anticyclone; diabatic descent was also strongest in this region. Increased N2O over a broad region near the edge of the polar vortex indicates the importance of horizontal transport. N2O decreased in the vortex, consistent with enhanced diabatic descent during the warmings.

Manney, G. L.↗
NASA NTRS1994

Low Ozone Anomalies in the Winter Middle Stratosphere

Microwave Limb Sounder observations of mid-stratospheric ozone during stratospheric warmings show tongues of high ozone drawn up from low latitudes into the developing anticyclone.

Microwave Limb Sounder ozone ozone anomalies middl↗
NASA NTRS1994

Chemical Depletion of Lower Stratospheric Ozone in the 1992-1993 Northern Winter Vortex

Satellite observations of ozone and chlorine monoxide in the Arctic lower stratosphere during winter 1992-1993 are compared with observations during other winters, observations of long-lived tracers and the evolution of the polar vortex. Chlorine in the lower stratospheric vortex during February 1993 was mostly in chemically reactive forms.

Arctic polar vortex↗
NASA NTRS1994

Lagrangian Transport Calculations Using UARS Data. Part I: Passive Tracers

The transport of passive tracers observed by UARS has been simulated using computed trajectories of thousands of air parcels initialized on a three-dimensional stratospheric grid. These trajectories are calculated in isentropic coordinates using horizontal winds provided by the United Kingdom Meteorological Office data assimilation system and vertical (cross-isentropic) velocities computed using a fast radiation code.

UARS computed trajectories↗
NASA NTRS1994

Evolution of MLS Ozone and the Polar Vortex During Winter

The evolution of polar ozone observed by the Upper Atmosphere Research Satellite Microwave Limb Sounder is described for the northern hemisphere (NH) winters of 1991/1992, 1992/1993, and 1993/1994, and the southern hemisphere (SH) winters of 1992 and 1993. Ozone in the mid-stratospheric vortex increases over the winter, with largest increases associated with stratospheric warmings, and a much larger increase in the NH than in the SH.

ozone↗
NASA NTRS1994

On the Motion of Air Through the Stratospheric Polar Vortex

Trajectory calculations using horizontal winds from the United Kingdom Meteorological Office data assimilation system, and vertical velocities from a radiation calculation are used to simulate the three-dimensional motion of air through the stratospheric polar vortex, for several northern hemisphere(NH) and southern hemisphere (SH) winters since the launch of UARS.

UARS↗