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Dive into the research topics where Adrian M. Lee is active.

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Featured researches published by Adrian M. Lee.


Journal of Geophysical Research | 1997

Carbon aerosols and atmospheric photochemistry

D. J. Lary; Adrian M. Lee; Ralf Toumi; Mike Newchurch; Michel Pirre; Jean-Baptiste Renard

Carbon aerosols are produced by all combustion processes. This paper investigates some possible effects of heterogeneous reduction of atmospheric constituents on carbon aerosols. Reduction of HNO 3 , NO 2 , and O 3 on carbon aerosols may be an important effect of increased air traffic that has not been considered to date. It is shown that if HNO 3 , NO 2 and O 3 are heterogeneously reduced on atmospheric amorphous carbon aerosols, then a significant, lower stratospheric ozone loss mechanism could exist. This ozone loss mechanism is almost independent of temperature and does not require the presence of sunlight. The mechanism can operate at all latitudes where amorphous carbon aerosols are present. The relative importance of the mechanism increases with nightlength. The reduction of HNO 3 on carbon aerosols could also be a significant renoxification process wherever carbon aerosols are present. Owing to the very different soot levels in the two hemispheres, this implies that there should be a hemispheric assymetry in the role of these mechanisms. The renoxification leads to simulated tropospheric HNO 3 /NO x ratios that are close to those observed. In contrast to the stratospheric response, the tropospheric production of NO x due to the reduction of HNO 3 would lead to tropospheric ozone production.


Geophysical Research Letters | 2000

Large loss of total ozone during the Arctic winter of 1999/2000

Björn-Martin Sinnhuber; M. P. Chipperfield; S. Davies; J. P. Burrows; K.-U. Eichmann; M. Weber; P. von der Gathen; M. Guirlet; G. A. Cahill; Adrian M. Lee; J. A. Pyle

Three-dimensional model calculations are used together with total ozone observations from the Global Ozone Monitoring Experiment (GOME) and ozone sonde measurements at Ny-Alesund, Spitsbergen to quantify the chemical ozone loss inside the Arctic polar vortex in winter 1999/2000. GOME shows March 2000 mean Arctic total ozone values of 365 DU, about 100 DU less than the 1980-1989 mean from TOMS data, well reproduced by the model calculations. A comparison of the modeled ozone with a passive ozone tracer and ozone sonde observations at Ny-Alesund shows that by the end of March 2000 about 2.5 ppmv of ozone are chemically depleted in the lower stratosphere, corresponding to more than 70% ozone loss. At the same time, the inferred loss in total ozone inside or at the edge of the polar vortex is between 90 and 140 DU. The large ongoing loss during March 2000 is likely to be due to widespread denitrification, which maintains high chlorine activation during this period.


Journal of Geophysical Research | 2001

The impact of the mixing properties within the Antarctic stratospheric vortex on ozone loss in spring

Adrian M. Lee; Howard K. Roscoe; Anna E. Jones; Peter H. Haynes; Emily Shuckburgh; Martin W. Morrey; Hugh C. Pumphrey

Calculations of equivalent length from an artificial advected tracer provide new insight into the isentropic transport processes occurring within the Antarctic stratospheric vortex. These calculations show two distinct regions of approximately equal area: a strongly mixed vortex core and a broad ring of weakly mixed air extending out to the vortex boundary. This broad ring of vortex air remains isolated from the core between late winter and midspring. Satellite measurements of stratospheric H2O confirm that the isolation lasts until at least mid-October. A three-dimensional chemical transport model simulation of the Antarctic ozone hole quantifies the ozone loss within this ring and demonstrates its isolation. In contrast to the vortex core, ozone loss in the weakly mixed broad ring is not complete. The reasons are twofold. First, warmer temperatures in the broad ring prevent continuous polar stratospheric cloud (PSC) formation and the associated chemical processing (i.e., the conversion of unreactive chlorine into reactive forms). Second, the isolation prevents ozone-rich air from the broad ring mixing with chemically processed air from the vortex core. If the stratosphere continues to cool, this will lead to increased PSC formation and more complete chemical processing in the broad ring. Despite the expected decline in halocarbons, sensitivity studies suggest that this mechanism will lead to enhanced ozone loss in the weakly mixed region, delaying the future recovery of the ozone hole.


Geophysical Research Letters | 1996

Model calculations of ozone depletion in the Arctic Polar Vortex for 1991/92 to 1994/95

M. P. Chipperfield; Adrian M. Lee; J. A. Pyle

We have used a 3D chemical transport model to investigate the potential for chemical ozone depletion in the Arctic polar vortex for the past 4 winters. By using the same chemical initial conditions for each winter we have isolated the effects of meteorological variability on polar ozone loss. These calculations show that during 1994/95 conditions in the Arctic polar vortex were the most conducive to ozone depletion in recent years. Our numerical experiments show that at 475 K (around 18 km) in the lower stratosphere the chemical ozone destruction between late December and mid March was greater than 30% over a large area of the polar vortex. Larger percentage losses, reaching 50%, occur at slightly lower altitudes. The average model depletion in the entire region poleward of 60°N over the same period was around 22% at 475 K. Similar calculations for the preceding three Arctic winters show less depletion. The large depletion for 1994/95 is a consequence of the extreme meteorological conditions during this winter.


Journal of Physical Chemistry A | 2009

Accurately reproducing ab initio electrostatic potentials with multipoles and fragmentation.

Hai-Anh Le; Adrian M. Lee; Ryan P. A. Bettens

In this work, we show that our energy based fragmentation method (Bettens, R. P. A.; Lee, A. M. J. Phys. Chem. A 2006, 110, 8777) accurately reproduces the electrostatic potential for a selection of peptides, both charged and uncharged, and other molecules of biological interest at the solvent accessible surface and beyond when compared with the full ab initio or density functional theory electrostatic potential. We also consider the ability of various point charge models to reproduce the full electrostatic potential and compare the results to our fragmentation electrostatic potentials with the latter being significantly superior. We demonstrate that our fragmentation approach can be readily applied to very large systems and provide the fragmentation electrostatic potential for the neuraminidase tetramer (ca. 24,000 atom system) at the MP2/6-311(+)G(2d,p) level. We also show that by using at least distributed monopoles, dipoles, and quadrupoles at atomic sites in the fragment molecules an essentially identical electrostatic potential to that given by the fragmentation electrostatic potential at and beyond the solvent accessible surface can be obtained.


Geophysical Research Letters | 2000

Model and measurements show Antarctic ozone loss follows edge of polar night

Adrian M. Lee; Howard K. Roscoe; Samuel J. Oltmans

A three-dimensional chemical-transport model of the stratosphere has been used to study the 1996 austral winter and spring. Both the model and ozonesonde measurements show that ozone depletion associated with the Antarctic ozone hole follows the edge of polar night: very little ozone-depleted air mixes ahead of the terminator as it sweeps poleward, until the terminator reaches 80°S. Other details of the model ozone field show very good agreement with measurements.


Journal of Geophysical Research | 2000

Seasonal observations of chlorine monoxide in the stratosphere over Antarctica during the 1996–1998 ozone holes and comparison with the SLIMCAT three-dimensional model

James Barrett; Brian J. Connor; Saeid Zoonematkermani; Alan Parrish; Adrian M. Lee; J. A. Pyle; M. P. Chipperfield

We report ground-based microwave measurements of chlorine monoxide (ClO) mixing ratio profiles above Scott Base, Antarctica (latitude = 77.85°S), during the late winter and early spring of 1996, 1997, and 1998 and analyze in detail the 1996 data. The instrument is permanently installed at the site, permitting continuous measurements throughout the ozone hole period, starting before the end of the polar night. The development of the lower stratospheric ClO layer is strikingly similar in all three years, with the peak (day-night) ClO mixing ratio at 22 km rising from 0.1 to 1.9–2.0 ppbv in the 21 days from August 13 to September 4. The altitude of the peak drifts downward from 22 to 17–18 km by the end of September. In 1997 and 1998 the chlorine remained in active species until about September 29, while in 1996 there was a rapid and sharp decline in ClO beginning on September 12. We compare the daily average ClO profiles for 1996 with the output of a three-dimensional off-line chemical transport model. The model output is sampled to match the data and is used as an a priori profile for retrieval of the measured profiles from the data, allowing a rigorous comparison of the consistency between the model and measurements without bias from an a priori. The model captures all of the major features of the measurements, including the rapid rise in August, the sharp drop on September 13 due to the arrival of warmer, ClOx-poor air over Scott Base, and the deactivation of ClOx into the reservoir species, HCl and ClONO2, during the last half of September. However, the model using recommended rate coefficients consistently underestimates the measured ClO, suggesting that the ratio of the ClO dimer photolysis rate to the dimer formation rate, j/kƒ, needs to be increased by a factor of 1.8±0.3. This has important implications for model calculations of ozone loss.


Journal of Geophysical Research | 1997

Three‐dimensional chemical forecasting: A methodology

Adrian M. Lee; G. D. Carver; M. P. Chipperfield; J. A. Pyle

During the recent ASHOE (Airborne Southern Hemisphere Ozone Experiment) and SESAME (Second European Stratospheric Arctic and Middle-Latitude Experiment) field campaigns we produced a number of 10-day chemical forecasts of the stratosphere to aid in flight planning and interpretation of the observations. A general circulation model was integrated at high resolution to produce a 10-day meteorological forecast. These forecast fields were then used to specify the circulation in an off-line three-dimensional chemical transport model to produce a medium-range chemical forecast of the stratosphere. The chemical model has a detailed stratospheric chemistry scheme, including heterogeneous reactions on polar stratospheric clouds and sulfate aerosols. The NASA ER-2 high-altitude research aircraft made in situ measurements of chemical tracers in the lower stratosphere during the ASHOE campaign, which took place in four deployments from March to October 1994. This paper presents examples from the chemical forecasts made during the second and fourth deployments. We show that the ability to indicate the likely composition of the atmosphere is an important improvement over the standard meteorological forecasts, especially in air perturbed by chemical processing on polar stratospheric clouds. Of particular interest was the ability to forecast the chemical composition of filaments, which had been eroded from the vortex edge. Furthermore, immediate post-flight comparison between observed data and synoptic model data gave useful chemical interpretation of the observations.


Journal of Geophysical Research | 2000

Ozone measurements during the Airborne Polar Experiment: Aircraft instrument validation, isentropic trends, and hemispheric fields prior to the 1997 Arctic ozone depletion

E. Kyrö; R. Kivi; T. Turunen; H. Aulamo; V. V. Rudakov; V. Khattatov; A. R. MacKenzie; M. P. Chipperfield; Adrian M. Lee; L. Stefanutti; F. Ravegnani

The first deployment of the ECOC electro chemical ozone cell (ECOC) instrument onboard the high-altitude research aircraft, the Geophysica M-55, took place from Rovaniemi, northern Finland, between December 23, 1996, and January 14, 1997. The ECOC data were compared against contemporaneous data from a network of balloon-borne ozone sondes. The comparison was carried out in potential vorticity-potential temperature (PV, Θ) coordinates, using meteorological analyses from the European Centre for Medium-Range Forecasts. The comparison showed that ozone mixing ratios measured by ECOC are lower than those measured by ozonesonde by a small but statistically significant bias of (−5.7 ± 2.8)% at the cruising altitudes of the aircraft, 15 to 19 km. After establishing and removing the average bias, ECOC and ozonesonde data were analyzed together to follow the development of ozone distributions in the early winter Arctic stratosphere. The analysis showed no evidence of chemical ozone depletion at the cruising altitudes of the aircraft, that is, between 435 and 490 K. The absence of chemical depletion is in agreement with polar statospheric cloud (PSC) observations, which showed no PSCs at aircraft cruising altitudes, although from January 5 onwards, PSCs were observed above cruising altitudes. Results from a three-dimensional chemical transport model reproduce the basic features of the reconstructed ozone fields. However, the model does not capture the observed ozone increase during the campaign, due to weak modeled ozone vertical gradients, and indicates small ozone depletion of about 3% inside the vortex at 480 K by mid January.


Faraday Discussions | 1995

Early modelling results from the SESAME and ASHOE campaigns

J. A. Pyle; M. P. Chipperfield; I. Kilbane-Dawe; Adrian M. Lee; Richard M. Stimpfle; Daniel Kohn; Wolfgang Renger; J. W. Waters

Data from the second European stratospheric arctic and middle latitude experiment (SESAME) and the airborne southern hemisphere ozone experiment (ASHOE)(recent campaigns in both hemispheres), and from the upper atmosphere research satellite (UARS) provide information about the movement, and possible mixing, of stratospheric air from the vortex and vortex edge into middle latitudes. Model studies reported here reproduce the observed features and may provide insight into their larger-scale structure. It is now clear that filaments of activated air, removed from the vortex edge, contribute to the observed decline of ozone in middle latitudes.

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J. A. Pyle

University of Cambridge

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Alan Parrish

University of Massachusetts Amherst

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James Barrett

State University of New York System

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Brian J. Connor

National Institute of Water and Atmospheric Research

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Ryan P. A. Bettens

Australian National University

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