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Newman, P. A.

Publications and source records attributed to Newman, P. A..

At least 37 records · Page 2
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NASA NTRS2008

The Relationship of Loss, Mean Age of Air and the Distribution of CFC's to Stratospheric Circulation and Implications for Atmospheric Lifetimes

Model-derived estimates of the annually integrated destruction and lifetime for various ozone depleting substances (ODSs) depend on the simulated stratospheric transport and mixing in the global model used to produce the estimate. Observations in the middle and high latitude lower stratosphere show that the mean age of an air parcel (i.e., the time since its stratospheric entry) is related to the fractional release for the ODs (i.e., the amount of the ODS that has been destroyed relative to the amount at the time of stratospheric entry). We use back trajectory calculations to produce an age spectrum, and explain the relationship between the mean age and the fractional release by showing that older elements in the age spectrum have experienced higher altitudes and greater ODs destruction than younger elements. In our study, models with faster circulations produce distributions for the age-of-air that are 'young' compared to a distribution derived from observations. These models also fail to reproduce the observed relationship between the mean age of air and the fractional release. Models with slower circulations produce both realistic distributions for mean age and a realistic relationship between mean age and fractional release. These models also produce a CFCl3 lifetime of approximately 56 years, longer than the 45 year lifetime used to project future mixing ratios. We find that the use of flux boundary conditions in assessment models would have several advantages, including consistency between ODS evolution and simulated loss even if the simulated residual circulation changes due to climate change.

Douglas, A. R.↗
NASA NTRS2007

An Ozone Increase in the Antarctic Summer Stratosphere: A Dynamical Response to the Ozone Hole

Profiles of ozone concentration retrieved from the SBUV series of satellites show an increase between 1979 and 1997 in the summertime Antarctic middle stratosphere (approx. 25-10 hPa). Data over the South Pole from ozone sondes confirm the increase. A similar ozone increase is produced in a chemistry climate model that allows feedback between constituent changes and the stratospheric circulation through radiative heating. A simulation that excludes the radiative coupling between predicted ozone and the circulation does not capture this ozone increase. We show that the ozone increase in our model simulations is caused by a dynamical feedback in response to the changes in the stratospheric wind fields forced by the radiative perturbation associated with the Antarctic ozone hole.

Stolarski, R. S.↗
NASA NTRS2007

Variations in Stratospheric Inorganic Chlorine Between 1991 and 2006

So how quickly will the ozone hole recover? This depends on how quickly the chlorine content (Cl2) of the atmosphere will decline. The ozone hole forms over the Antarctic each southern spring (September and October). The extremely small ozone amounts in the ozone hole are there because of chemical reactions of ozone with chlorine. This chlorine originates largely from industrially produced chlorofluorocarbon (CFC) compounds. An international agreement, the Montreal Protocol, is drastically reducing the amount of chlorine-containing compounds that we are releasing into the atmosphere. To be able to attribute changes in stratospheric ozone to changes in chlorine we need to know the distribution of atmospheric chlorine. However, due to a lack of continuous observations of all the key chlorine gases, producing a continuous time series of stratospheric chlorine has not been achieved to date. We have for the first time devised a technique to make a 17-year time series for stratospheric chlorine that uses the long time series of HCl observations made from several space borne instruments and a neural network. The neural networks allow us to both inter-calibrate the various HCl instruments and to infer the total amount of atmospheric chlorine from HCl. These new estimates of Cl, provide a much needed critical test for current global models that currently predict significant differences in both Cl(sub y) and ozone recovery. These models exhibit differences in their projection of the recovery time and our chlorine content time series will help separate the good from the bad in these projections.

Lary, D. J.↗
NASA NTRS2007

A New Formulation of Equivalent Effective Stratospheric Chlorine (EESC)

Equivalent effective stratospheric chlorine (EESC) is a convenient parameter to quantify the effects of halogens (chlorine and bromine) on ozone depletion in the stratosphere. We show and discuss a new formulation of EESC that now includes the effects of age-of-air dependent fractional release values and an age-of-air spectrum. This new formulation provides quantitative estimates of EESC that can be directly related to inorganic chlorine and bromine throughout the stratosphere. Using this EESC formulation, we estimate that human-produced ozone depleting substances will recover to 1980 levels in 2041 in the midlatitudes, and 2067 over Antarctica. These recovery dates are based upon the assumption that the international agreements for regulating ozone-depleting substances are adhered to. In addition to recovery dates, we also estimate the uncertainties in the estimated time of recovery. The midlatitude recovery of 2041 has a 95% confidence uncertainty from 2028 to 2049, while the 2067 Antarctic recovery has a 95% confidence uncertainty from 2056 to 2078. The principal uncertainties are from the estimated mean age-of-air, and the assumption that the mean age-of-air and fractional release values are time independent. Using other model estimates of age decrease due to climate change, we estimate that midlatitude recovery may be accelerated from 2041 to 2031.

Newman, P. A.↗
NASA NTRS2007

The Relationship of Loss, Mean Age of Air and the Distribution of CFCs to Stratospheric Circulation and Implications for Atmospheric Lifetimes

Man-made molecules called chlorofluorcarbons (CFCs) are broken apart in the stratosphere by high energy light, and the reactive chlorine gases that come from them cause the ozone hole. Since the ozone layer stops high energy light from reaching low altitudes, CFCs must be transported to high altitudes to be broken apart. The number of molecules per volume (the density) is much smaller at high altitudes than near the surface, and CFC molecules have a very small chance of reaching that altitude in any particular year. Many tons of CFCs were put into the atmosphere during the end of the last century, and it will take many years for all of them to be destroyed. Each CFC has an atmospheric lifetime that depends on the amount of energy required to break them apart. Two of the gases that were made the most are CFC13 and CF2C12. It takes more energy to break apart CF2C12 than CFC13, and its lifetime is about 100 years, nearly twice as long as the lifetime for CFC13. It is hard to figure out the lifetimes from surface measurements because we don't know exactly how much was released into the air each year. Atmospheric models are used to predict what will happen to ozone and other gases as the CFCs decrease and other gases like C02 continue to increase during the next century. CFC lifetimes are used to predict future concentrations and all assessment models use the predicted future concentrations. The models have different circulations and the amount of CFC lost according to the model may not match the loss that is expected according to the lifetime. In models the amount destroyed per year depends on how fast the model pushes air into the stratosphere and how much goes to high altitudes each year. This paper looks at the way the model circulation changes the lifetimes, and looks at measurements that tell us which model is more realistic. Some models do a good job reproducing the age-of-air, which tells us that these models are circulating the stratospheric air at the right speed. These same models also do a good job reproducing the amount of CFCs in the lower atmosphere where they were measured by instruments on NASA's ER-2, a research plane that flies in the lower stratosphere. The lifetime for CFC13 that is calculated using the models that do the best job matching the data is about 25% longer than most people thought. This paper shows that using these measurements to decide which models are more realistic helps us understand why their predictions are different from each other and also to decide which predictions are more likely.

Douglass, A. R.↗
NASA NTRS2006

Relative Contribution of Greenhouse Gases and Ozone Change to Temperature Trends in the Stratosphere: A Chemistry/Climate Model Study

Long-term changes in greenhouse gases, primarily carbon dioxide, are expected to lead to a warming of the troposphere and a cooling of the stratosphere. We examine the cooling of the stratosphere and compare the contributions greenhouse gases and ozone change for the decades between 1980 and 2000. We use 150 years of simulation done with our coupled chemistry/climate model (GEOS 4 GCM with GSFC CTM chemistry) to calculate temperatures and constituents fiom,1950 through 2100. The contributions of greenhouse gases and ozone to temperature change are separated by a time-series analysis using a linear trend term throughout the period to represent the effects of greenhouse gases and an equivalent effective stratospheric chlorine (EESC) term to represent the effects of ozone change. The temperature changes over the 150 years of the simulation are dominated by the changes in greenhouse gases. Over the relatively short period (approx. 20 years) of ozone decline between 1980 and 2000 changes in ozone are competitive with changes in greenhouse gases. The changes in temperature induced by the ozone change are comparable to, but smaller than, those of greenhouse gases in the upper stratosphere (1-3 hPa) at mid latitudes. The ozone term dominates the temperature change near both poles with a negative temperature change below about 3-5 hPa and a positive change above. At mid latitudes in the upper stratosphere and mesosphere (above about 1 hPa) and in the middle stratosphere (3 to 70 ma), the greenhouse has term dominates. From about 70 hPa down to the tropopause at mid latitudes, cooling due to ozone changes is the largest influence on temperature. Over the 150 years of the simulation, the change in greenhouse gases is the most important contributor to temperature change. Ozone caused a perturbation that is expected to reverse over the coming decades. We show a model simulation of the expected temperature change over the next two decades (2006-2026). The simulation shows a crossover between lower atmospheric heating and upper atmospheric cooling that is located at about 90 hPa in the tropics and 30-40 hPa in the polar regions. This results from the combination of continuing increases in greehouse gases and recovery from ozone depletion.

Stolarski, Richard S.↗
NASA NTRS2004

Non-coincident Inter-instrument Comparisons of Ozone Measurements Using Quasi-conservative Coordinates

Ozone measurements from ozonesondes, AROTAL, DIAL, and POAM III instruments during the SOLVE-2/VINTERSOL period are composited in a time-varying, flow-following quasi-conservative (PV-6) coordinate space; the resulting composites from each instrument are mapped onto the other instruments locations and times. The mapped data are then used to intercompare data from the different instruments. Overall, the four data sets are found to be in good agreement. AROTAL shows somewhat lower values below 16 km, and DIAL has a positive bias at the upper limits of its altitude range. These intercomparisons are consistent with those obtained from more conventional near-coincident profiles, where available. Although the PV-theta mapping technique entails larger uncertainties of individual profile differences compared to direct near-coincident comparisons, the ability to include much larger numbers of comparisons can make this technique advantageous.

Lait, L. R.↗
NASA NTRS2003

The 2002 Antarctic Ozone Hole

Since 1979, the ozone hole has grown from near zero size to over 24 Million km2. This area is most strongly controlled by levels of inorganic chlorine and bromine oncentrations. In addition, dynamical variations modulate the size of the ozone hole by either cooling or warming the polar vortex collar region. We will review the size observations, the size trends, and the interannual variability of the size. Using a simple trajectory model, we will demonstrate the sensitivity of the ozone hole to dynamical forcing, and we will use these observations to discuss the size of the ozone hole during the 2002 Austral spring. We will further show how the Cly decreases in the stratosphere will cause the ozone hole to decrease by 1-1.5% per year. We will also show results from a 3-D chemical transport model (CTM) that has been continuously run since 1999. These CTM results directly show how strong dynamics acts to reduce the size of the ozone hole.

Newman, P. A.↗
NASA NTRS2002

The Distribution of Ozone in the Early Stages of Polar Vortex Development

Previous analysis has shown that the distribution of O3 at high northern latitudes in the lower-to-middle stratosphere at the beginning of the winter season, 1999-2000 has a characteristic distribution, which is consistent between in situ and satellite measurements [Kawa et al., The Interaction Between Dynamics and Chemistry of Ozone in the Set-up Phase of the Northern Hemisphere Polar Vortex, submitted manuscript, 2001 ]. Initial O3 profiles in the vortex are similar to each other and are quite different from outside the vortex at the same latitude and also from a zonal mean climatology. In the vortex, O3 is nearly constant from 500 to above 800 K with a value at 3 ppmv +/- approx.10%. Values outside the vortex are up to a factor of 2 higher and increase significantly with potential temperature. The seasonal time series of POAM data shows that relatively low O3 mixing ratios, which characterize the vortex in late fall, are already present at high latitudes at the end of summer in September before the vortex circulation sets up. This suggests a possible feedback role between O3 chemistry and the formation of the vortex, which is dominated by the seasonal radiation balance. Here we show that these characteristic O3 distributions are consistent from year to year and between the hemispheres. We will attempt to determine whether variations in fall vortex O3 are related in any way to O3 abundances and vortex structure later during winter and into spring.

Kawa, S. R.↗
NASA NTRS2002

Effect of Random Geometric Uncertainty on the Computational Design of a 3-D Flexible Wing

The effect of geometric uncertainty due to statistically independent, random, normally distributed shape parameters is demonstrated in the computational design of a 3-D flexible wing. A first-order second-moment statistical approximation method is used to propagate the assumed input uncertainty through coupled Euler CFD aerodynamic / finite element structural codes for both analysis and sensitivity analysis. First-order sensitivity derivatives obtained by automatic differentiation are used in the input uncertainty propagation. These propagated uncertainties are then used to perform a robust design of a simple 3-D flexible wing at supercritical flow conditions. The effect of the random input uncertainties is shown by comparison with conventional deterministic design results. Sample results are shown for wing planform, airfoil section, and structural sizing variables.

Gumbert, C. R.↗
NASA NTRS2002

Interannual Variability of Ozone in the Polar Vortex during the Fall Season

Previous analysis has shown that the distribution of O3 at high northern latitudes in the lower-to-middle stratosphere at the beginning of the winter season has a characteristic distribution, which is consistent between in situ and satellite measurements. Initial O3 profiles in the vortex are similar to each other and are quite different from outside the vortex at the same latitude and also from a zonal mean climatology. In the vortex, O3 is nearly constant from 500 to above 800 K with a value near 3 ppmv. Values outside the vortex are up to a factor of 2 higher and increase significantly with potential temperature. Model analysis indicates that the characteristic vortex O3 profiles arise from a combination of seasonally accelerated photochemical loss at high latitudes and minimal transport of air from lower latitudes. Analysis of the relatively high-resolution POAM data shows that these characteristic O3 distributions are consistent from year to year and between the hemispheres. Here we emphasize analysis of the 24-year time series of O3 data from SBUV in the lower-to-middle stratosphere at high latitudes in the fall vortex. We find that the variability of O3 from SBUV is relatively small in this regime and no significant trend is detectable. The implications of the findings for stratospheric O3 chemistry and transport will be explored.

Bhartia, P. K.↗
NASA NTRS2001

Ozone Loss From Quasi-Conservative Coordinate Mapping During the 1999-2000 SOLVE Campaign

During the winter of 1999-2000, the Sage III Ozone Loss and Validation Experiment (SOLVE) field experiment took place in Kiruna, Sweden. The purpose of SOLVE was to examine ozone depletion mechanisms in the Arctic stratosphere (from about 10 to 50 km altitude) during the winter and early spring, when a band of strong winds (the 'polar vortex') circle the pole. Measurements of stratospheric ozone were made by several different kinds of instruments in different meteorological situations. We analyzed these data using the 'quasi-conservative coordinate mapping' technique, in which the measurements are analyzed in terms of meteorological properties ('potential temperature' and 'potential vorticity') which tend not to change very much over a few days. This technique reduces or removes the changes that are associated with the polar vortex moving around. Over longer time periods, potential temperature and potential vorticity change as air cools and descends within the polar vortex. We account for these changes by calculating the trajectories of air parcels, and this enables us to extend the analysis over a ten-week period from January 10 to March 17, 2000. Using data from the NASA ER-2 aircraft, from the DIAL and AROTEL laser sounders on the NASA DC-8 aircraft, and balloon-borne ozonesondes, our analysis reveals changes in ozone which, because we have removed the effects of polar vortex motion and the descending air, indicate chemical destruction of ozone in early 2000. We find a peak decline rate of approximately 0.03 ppmv/day near 470 K of potential temperature (near 20 km) in mid-January which sinks in altitude to around 440 K (near 18 km) in mid-March.

Lait, L. R.↗
NASA NTRS2000

Accuracy of Modelled Stratospheric Temperatures in the Winter Arctic Vortex from Infra Red Montgolfier Long Duration Balloon Measurements

The temperature of the stratosphere has been measured in the Arctic vortex every 9-10 minutes along the trajectory of four Infra Red Montgolfier long duration balloons flown for 7 to 22 days during the winters of 1997 and 1999. From a number of comparisons to independent sensors, the accuracy of the measurements is demonstrated to be plus or minus 0.5 K during nighttime and at altitude below 28 km (10 hPa). The performances of the analyses of global meteorological models, European Center for Medium Range Weather Forecasts (ECMWF) 31 and 50 levels, United Kingdom Meteorological Office (UKMO), Data Assimilation Office (DAO), National Climatic Prediction Center (NCEP) and NCEP/NCAR reanalysis, used in photochemical simulations of ozone destruction and interpretation of satellite data, are evaluated by comparison to this large (3500 data points) and homogeneous experimental data set. Most of models, except ECMWF31 in 1999, do show a smal1 average warm bias of between 0 and 1.6 K, with deviations particularly large, up to 20 K at high altitude (5hPa) in stratospheric warming conditions in 1999. Particularly wrong was ECMWF 31 levels near its top level at 10 hPa in 1999 where temperature 25 K colder than the real atmosphere were reported. The average dispersion between models and measurements varies from plus or minus 1.0 to plus or minus 3.0 K depending on the model and the year. It is shown to be the result of three contributions. The largest is a long wave modulation likely caused by the displacement of the temperature field in the analyses compared to real atmosphere. The second is the overestimation of the vertical gradient of temperature particularly in warming conditions, which explains the increase of dispersion from 1997 to 1999. Unexpectedly, the third and smallest (plus or minus 0.6-0.7 K) is the contribution of meso and subgrid scale vertical and horizontal features associated to the vertical propagation of orographic or gravity waves. Compared to other models, the newly available ECMWF 50 levels version assimilating the high vertical resolution radiances of the space borne Advanced Microwave Sounding Unit, performs significantly better (0.03 plus or minus 1.12 K on average between 10 and 140 hPa in 1999) than other models.

Pommereau, J.-P.↗
NASA NTRS2000

Quantifying Denitrification and Its Effect on Ozone Recovery

Upper Atmosphere Research Satellite observations indicate that extensive denitrification, without significant dehydration, currently occurs only in the Antarctic during mid to late June. The fact that denitrification occurs in a relatively warm month in the Antarctic raises concern about the likelihood of its occurrence, and associated effects on ozone recovery, in a future colder and possibly more humid Arctic lower stratosphere. Polar stratospheric cloud lifetimes required for Arctic denitrification to occur in the future are presented and contrasted against the current Antarctic cloud lifetimes. Model calculations show widespread severe denitrification could enhance future Arctic ozone loss by up to 30%.

Tabazadeh, A.↗
NASA NTRS2000

An Investigation of Polar Ozone Recovery in the 1997 Southern Hemisphere Spring

A chemical transport model is used to investigate the processes that control the depth and duration of the ozone 'hole' in the lower stratosphere through comparisons of model output with measurements from the Total Ozone Mapping Spectrometer (TOMS) and from the Microwave Limb Sounder (MLS) and Halogen Occultation Experiment (HALOE), both on the Upper Atmosphere Research Satellite (UARS). This study extends previous model comparisons with observations into October and November and examine levels in (greater than 31 hPa) and above (less than 31 hPa) the chemical loss region. Averages of column ozone in the model decrease through mid-October below 31 hPa but begin to increase in mid-September above 31 hPa. An investigation of model-tracer data comparisons and other meteorological parameters indicate that the model presents a consistent picture of top-down recovery and tracer transport. An O03budget study at 500 K (below 31 hPa) and 840 K (above 31 hPa) is carried out to investigate the processes that control the timing of the transition of ozone from a chemical to dynamically driven regime. The model ozone decrease at 500 K is due to chemical loss in August and September but is due to upward motion in October. The ozone increase at 840 K is primarily due to photochemical production, with a smaller contribution from transport. These results show that chemistry and dynamics can play different roles in polar vortex ozone recovery at different levels.

Pierson, J. M.↗
NASA NTRS2000

Chance Encounter with a Stratospheric Kerosene Rocket Plume From Russia Over California

A high-altitude aircraft flight on April 18, 1997 detected an enormous aerosol cloud at 20 km altitude near California (37 N). Not visually observed, the cloud had high concentrations of soot and sulfate aerosol, and was over 180 km in horizontal extent. The cloud was probably a large hydrocarbon fueled vehicle, most likely from rocket motors burning liquid oxygen and kerosene. One of two Russian Soyuz rockets could have produced the cloud: a launch from the Baikonur Cosmodrome, Kazakhstan on April 6; or from Plesetsk, Russia on April 9. Parcel trajectories and long-lived trace gas concentrations suggest the Baikonur launch as the cloud source. Cloud trajectories do not trace the Soyuz plume from Asia to North America, illustrating the uncertainties of point-to-point trajectories. This cloud encounter is the only stratospheric measurement of a hydrocarbon fuel powered rocket.

Newman, P. A.↗
NASA NTRS2000

An Assessment of the Ozone Loss During the 1999-2000 SOLVE Campaign

Ozone observations from ozonesondes, the DIAL and AROTEL lidars aboard the DC-8, in situ ozone measurements from the ER-2 and satellite ozone measurements from POAM were used to assess ozone loss during the SOLVE 1999-2000 campaign. We compare three different methods of computing the ozone loss. The first method simply compares the time sequence of ozonesondes taken at the same station inside the vortex from December through the end of March. In the second method, ozonesondes from a variety of stations are compared using a variant on the Match technique. This method uses short (approx. 5-10 day) forward diabatic trajectories to connect various sonde launches. In the third method, the measurements are simply injected into a diabatic trajectory model and carried forward in time from December 1 to March 16. Over 60,000 individual measurements were used in the last calculation. Again, ozone loss is estimated by comparing vortex interior measurements made early in the campaign with those made later in the campaign. The diabatic nature of the second and third methods calculation presumably corrects for the normal increase in ozone within the vortex due to downward advection. The three methods agree that the largest ozone loss occurs between 400 and 460 K potential temperatures (approx. 16-20 km) with slightly over 1.5 ppmv lost over the winter period. Between 460 K and 500 K (approx. 22 km) net ozone loss is less than 0.8 ppmv. From 500K to 600K (26 km) net loss is less than 0.5 ppmv.

Schoeberl, M. R.↗