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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Interhemispheric comparison of the development of the stratospheric polar vortex during fall - A 3-dimensional perspective for 1991-1992

The development of the stratospheric polar vortex during fall and early winter in the Northern Hemisphere (NH) during 1991-1992, and the Southern Hemisphere (SH) during 1992 is examined using National Meteorological Center data. Compared to the NH, the polar vortex in the SH developed with less variability on short time scales, deepened more rapidly and continued to expand well into winter. Daily minimum temperatures in the lower stratosphere were lowest at equivalent seasonal dates in both hemispheres, but values below the condensation temperatures of polar stratospheric clouds occurred earlier, persisted much longer, and occupied a larger volume of air in the SH. These interhemispheric meteorological differences can account for some of the key features of the chlorine monoxide distributions observed by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite.

Manney, Gloria L.↗
NASA NTRS1989

Transport into the south polar vortex in early spring

The effect of transport on the springtime decline in ozone in the southern polar vortex was investiated using data on long-lived gas tracers (N2O, CH4, CCl4, CH3CCl3, CO, CFC-11, CFC-12, and CFC-113) obtained by the ER-2 aircraft in the period between August 23 and September 22 during the Airborne Antarctic Ozone Experiment. It was found that, while the concentrations of long-lived trace gases remained relatively constant for fixed potential temperature and latitude, the ozone mixing ratio over the same period declined by more than 50 percent inside the polar vortex near 18-km altitude. These data indicate a substantial photochemical sink of ozone. The evidence of the zero or negative time tendencies for long-lived trace gases and the meridional and vertical gradients of ozone imply that transport is supplying ozone to the polar region during springtime.

Hartmann, D. L.↗
NASA NTRS1993

Stratospheric meteorological conditions in the Arctic polar vortex, 1991 to 1992

Stratospheric meteorological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 K) should have formed over small regions in early December. The temperatures in the polar vortex warmed beyond NAT temperatures by late January (earlier than normal). Perturbed chemistry was found to be associated with these cold temperatures.

Newman, P.↗
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 NTRS1996

Interannual Variability of the North Polar Vortex in the Lower Stratosphere During the UARS Mission

Northern winters since the 1991 launch of UARS are compared to earlier years (1978 -1991) with respect to the potential for formation of Polar Stratospheric Clouds and for isolation of the north polar vortex. Daily NMC temperature minima at 465 K late in the winter of 1993-94 and again in December 1994 were the lowest values experienced during these times of the year (since 1978). Northern PV gradients were unusually strong in 1991-92 prior to late January and throughout the winter in both 1992-93 and 1994-95. Of all northern winters since 1978, 1994-95 with its early extended cold spell and persistently strong PV gradients most resembled the Antarctic winter lower stratosphere. Even so, temperatures was never as low, nor was the polar vortex as large, as during a typical southern winter. Judged by daily temperature minima and PV gradients at 465 K, meteorological conditions in the Arctic winter lower stratosphere during the UARS period were more conducive to vortex ozone loss by heterogeneous chemistry than in most previous winters since 1978-79.

Zurek, R. W.↗
NASA NTRS1988

Polar vortex dynamics

Recent work with high resolution, one-layer numerical models of fluid flows resembling those in the real stratosphere has suggested that: (1) the interiors of strong cyclonic vortices like the Antarctic polar vortex may be almost completely isolated laterally from their surroundings - perhaps even completely isolated, under some circumstances; (2) by contrast, material near the edge of such and isolated region can easily be eroded (or mixed one-sidedly) into the surrounding region; and (3) the erosion characteristically produces extremely steep gradients in isentropic distributions of potential vorticity (PV) and of other tracers, possibly down to horizontal length scales of a few kilometers only. Such length scales may occur both at the edge of the main polar vortex and in smaller features outside it, such as thin filamentary structures, produced by the erosion process.

Mcintyre, Michael↗
NASA NTRS1990

Ozone loss in the Arctic polar vortex inferred from high-altitude aircraft measurements

The Arctic polar vortex in winter is known to be chemically primed for ozone depletion, yet it does not exhibit the large seasonal ozone decrease that characterizes its southern counterpart. This difference may be due in part to a net flux of ozone-rich air through the Arctic vortex, which can mask ozone loss. But by using a chemically conserved tracer as a reference, significant ozone loss can be identified. This loss is found to be correlated with high levels of chlorine monoxide, suggesting that much of the decrease in ozone is caused by anthropogenic emissions of chlorofluorocarbons.

Proffitt, M. H.↗
DOE OSTI2024

Higher‐Order Gravity Waves and Traveling Ionospheric Disturbances From the Polar Vortex Jet on 11–15 January 2016: Modeling With HIAMCM‐SAMI3 and Comparison With Observations in the Thermosphere and Ionosphere

Abstract In Vadas et al. (2024, https://doi.org/10.1029/2024ja032521 ), we modeled the atmospheric gravity waves (GWs) during 11–14 January 2016 using the HIAMCM, and found that the polar vortex jet generates medium to large‐scale, higher‐order GWs in the thermosphere. In this paper, we model the traveling ionospheric disturbances (TIDs) generated by these GWs using the HIAMCM‐SAMI3 and compare with ionospheric observations from ground‐based Global Navigation Satellite System (GNSS) receivers, Incoherent Scatter Radars (ISR) and the Super Dual Auroral Radar Network (SuperDARN). We find that medium to large‐scale TIDs are generated worldwide by the higher‐order GWs from this event. Many of the TIDs over Europe and Asia have concentric ring/arc‐like structure, and most of those over North/South America have planar wave structure and occur during the daytime. Those over North/South America propagate southward and are generated by higher‐order GWs from Europe/Asia which propagate over the Arctic. These latter TIDs can be misidentified as arising from geomagnetic forcing. We find that the higher‐order GWs that propagate to Africa and Brazil from Europe may aid in the formation of equatorial plasma bubbles (EPBs) there. We find that the simulated GWs, TIDs and EPBs agree with EISCAT, PFISR, GNSS, and SuperDARN measurements. We find that the higher‐order GWs are concentrated at N at 200 km, in agreement with GOCE and CHAMP data. Thus the polar vortex jet is important for generating TIDs in the northern winter ionosphere via multi‐step vertical coupling through GWs.

Vadas, Sharon L. [Northwest Research Associates Bo↗
NASA NTRS1988

Climatology of the stratospheric polar vortex and planetary wave breaking

The distribution of Ertel's potential vorticity (PV) on the 850 K isentropic surface is used to establish a climatology for the transient evolution of the planetary scale circulation in the Northern Hemisphere winter midstratosphere. PV distributions are computed from gridded NMC daily temperature and height maps for the 10 and 30 mb levels, and show that a very good approximation for 850 K PV can be derived from 10 mb heights and temperatures alone. It is assumed that reversals of the latitudinal gradient of PV, localized in longitude and latitude may be regarded as signatures of planetary wave breaking. Wave breaking identified by such signatures tends to occur mainly in the vicinity of the Aleutian anticyclone, with a secondary maximum over Europe. The area of the polar vortex, defined as the area enclosed by PV contours greater than a certain critical value, is strongly influenced by wave breaking. Erosion of the polar vortex due to transport and mixing of PV leads to a preconditioned state, when defined in terms of vortex area, that always occurs prior to major stratospheric warmings. During winters with little PV transport or mixing, the vortex area evolves rather uniformly in response to radiative forcing. During winters with major sudden warmings, the wave breaking signature as defined here first appears at low values of PV, then rapidly moves toward higher values as the vortex area is reduced and the 'surf-zone' structure becomes well defined.

Baldwin, Mark P.↗
NASA NTRS2002

Comparison of measurements and models in stratospheric polar vortex studies

An overview will be given of recent studies comparing model results with observations of stratospheric meteorological and trace gas fields, focusing on the polar vortex during winter. Studies comparing process-oriented (e.g., stability) model, mechanistic (i.e., forced lower boundary near the tropopause) model and general circulation model (GCM) simulations of the dynamics of the polar winter stratosphere with analyzed or assimilated meteorological datasets are reviewed.

modeling↗
NASA NTRS2006

Chemical Observations of a Polar Vortex Intrusion

An intrusion of vortex edge air in D the interior of the Arctic polar vortex was observed on the January 31,2005 flight of the NASA DC-8 aircraft. This intrusion was identified as anomalously high values of ozone by the AROTAL and DIAL lidars. Our analysis shows that this intrusion formed when a blocking feature near Iceland collapsed, allowing edge air to sweep into the vortex interior. along the DC-8 flight track also shows the intrusion in both ozone and HNO3. Polar Stratospheric Clouds (PSCs) were observed by the DIAL lidar on the DC-8. The spatial variability of the PSCs can be explained using MLS HNO3 and H2O observations and meteorological analysis temperatures. We also estimate vortex denitrification using the relationship between N2O and HNO3. Reverse domain fill back trajectory calculations are used to focus on the features in the MLS data. The trajectory results improve the agreement between lidar measured ozone and MLS ozone and also improve the agreement between the HNO3 measurements PSC locations. The back trajectory calculations allow us to compute the local denitrification rate and reduction of HCl within the filament. We estimate a denitrification rate of about lO%/day after exposure to below PSC formation temperature. Analysis of Aura MLS observations made

Schoeberl, M. R.↗
NASA NTRS1990

Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex

An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator.

Yung, Yuk L.↗
NASA NTRS2000

Lamination and polar vortex development in fall from ATMOS long-lived trace gases observed during November 1994

Long-lived trace-gas profiles observed by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument around the developing polar vortex (the protovortex) during early November 1994 show distinctive inversions (lamiane). High-resolution profiles calculated using a reverse trajectory (RT) model to produce the majority of these laminae, demonstrating that most of these features arise from advection by the large-scale winds.

polar↗
NASA NTRS2000

A Composite View of Ozone Evolution in the 1995-1996 Northern Winter Polar Vortex Developed from Airborne Lidar and Satellite Observations

The processes which contribute to the ozone evolution in the high latitude northern lower stratosphere are evaluated using a three dimensional model simulation and ozone observations. The model uses winds and temperatures from the Goddard Earth Observing System Data Assimilation System. The simulation results are compared with ozone observations from three platforms: the differential absorption lidar (DIAL) which was flown on the NASA DC-8 as part of the Vortex Ozone Transport Experiment; the Microwave Limb Sounder (MLS); the Polar Ozone and Aerosol Measurement (POAM II) solar occultation instrument. Time series for the different data sets are consistent with each other, and diverge from model time series during December and January. The model ozone in December and January is shown to be much less sensitive to the model photochemistry than to the model vertical transport, which depends on the model vertical motion as well as the model vertical gradient. We evaluate the dependence of model ozone evolution on the model ozone gradient by comparing simulations with different initial conditions for ozone. The modeled ozone throughout December and January most closely resembles observed ozone when the vertical profiles between 12 and 20 km within the polar vortex closely match December DIAL observations. We make a quantitative estimate of the uncertainty in the vertical advection using diabatic trajectory calculations. The net transport uncertainty is significant, and should be accounted for when comparing observations with model ozone. The observed and modeled ozone time series during December and January are consistent when these transport uncertainties are taken into account.

Douglass, A. R.↗