A5022877908- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Climate variability and models
- Oceanographic and Atmospheric Processes
- Marine and coastal ecosystems
- Meteorological Phenomena and Simulations
- Astro and Planetary Science
- Planetary Science and Exploration
- Geology and Paleoclimatology Research
- Ocean Acidification Effects and Responses
- Methane Hydrates and Related Phenomena
- Tropical and Extratropical Cyclones Research
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Space Exploration and Technology
- Urban Heat Island Mitigation
- Air Quality and Health Impacts
- Geophysics and Gravity Measurements
- Climate Change and Health Impacts
- Air Quality Monitoring and Forecasting
- Arctic and Antarctic ice dynamics
- Atmospheric aerosols and clouds
- Urban Green Space and Health
- Water Quality Monitoring and Analysis
University of Baltimore
2006-2025
Johns Hopkins University
2015-2024
Planetary Science Institute
2000-2024
UNSW Sydney
2018-2023
University of Tasmania
2023
Weizmann Institute of Science
2021
Indiana University
2020
NOAA Earth System Research Laboratory
2018
Cooperative Institute for Research in Environmental Sciences
2018
University of St Andrews
2017
Abstract The importance of stratospheric ozone depletion on the atmospheric circulation troposphere is studied with an general model, Community Atmospheric Model, version 3 (CAM3), for second half twentieth century. In particular, relative contrasted that increased greenhouse gases and accompanying sea surface temperature changes. By specifying gas forcings independently, performing long, time-slice integrations, it shown impacts are roughly 2–3 times larger than those associated gases,...
Simulations of the stratosphere from thirteen coupled chemistry‐climate models (CCMs) are evaluated to provide guidance for interpretation ozone predictions made by same CCMs. The focus evaluation is on how well fields and processes that important determining distribution represented in simulations recent past. core period 1980 1999 but long‐term trends compared an extended (1960–2004). Comparisons polar high‐latitude temperatures show most CCMs have only small biases Northern Hemisphere...
We review the relationship between tracer distributions and transport timescales in stratosphere discuss use of to evaluate constrain theories numerical models stratosphere. The “age spectrum,” distribution transit times since stratospheric air last made tropospheric contact, provides a way understand information tracers, how sensitive different tracers are various processes, combination rates. Trace gas observations can be used infer aspects age spectrum, most commonly “mean age,” but also...
It has recently been shown that extreme stratospheric events (ESEs) are followed by surface weather anomalies (for up to 60 days), suggesting variability might be used extend prediction beyond current time scales. In this paper, attention is drawn away from the stratosphere demonstrate originating point of ESEs located in troposphere. First, it anomalously strong eddy heat fluxes at 100 hPa nearly always precede weak vortex events, and conversely, consistent with wave–mean flow interaction...
Simulations from eleven coupled chemistry‐climate models (CCMs) employing nearly identical forcings have been used to project the evolution of stratospheric ozone throughout 21st century. The model‐to‐model agreement in projected temperature trends is good, and all CCMs predict continued, global mean cooling stratosphere over next 5 decades, increasing around 0.25 K/decade at 50 hPa 1 under Intergovernmental Panel on Climate Change (IPCC) Special Report Emissions Scenarios (SRES) A1B...
In the past several decades, tropospheric westerly winds in Southern Hemisphere have been observed to accelerate on poleward side of surface wind maximum. This has attributed combined anthropogenic effects increasing greenhouse gases and decreasing stratospheric ozone is predicted continue by Intergovernmental Panel Climate Change/Fourth Assessment Report (IPCC/AR4) models. this paper, predictions Chemistry-Climate Model Validation (CCMVal) models are examined: Unlike AR4 models, CCMVal a...
The impact of stratospheric ozone on the tropospheric general circulation Southern Hemisphere (SH) is examined with a set chemistry‐climate models participating in Stratospheric Processes and their Role Climate (SPARC)/Chemistry‐Climate Model Validation project phase 2 (CCMVal‐2). integrations both past future climates reveal crucial role driving SH change: stronger depletion late spring generally leads to greater poleward displacement intensification midlatitude jet, expansion Hadley cell...
Abstract The response of stratospheric climate and circulation to increasing amounts greenhouse gases (GHGs) ozone recovery in the twenty-first century is analyzed simulations 11 chemistry–climate models using near-identical forcings experimental setup. In addition an overall global cooling stratosphere (0.59 ± 0.07 K decade−1 at 10 hPa), causes a warming Southern Hemisphere polar lower summer with enhanced above. rate correlates projected by and, on average, changes from 0.8 0.48 100 hPa as...
Abstract. A continuous tropospheric and stratospheric vertically resolved ozone time series, from 1850 to 2099, has been generated be used as forcing in global climate models that do not include interactive chemistry. multiple linear regression analysis of SAGE I+II satellite observations polar ozonesonde measurements is for the zonal mean dataset during well-observed period 1979 2009. In addition terms describing annual cycle, includes representing equivalent effective chlorine (EESC) 11-yr...
Abstract. Equivalent effective stratospheric chlorine (EESC) is a convenient parameter to quantify the effects of halogens (chlorine and bromine) on ozone depletion in stratosphere. We show, discuss, analyze new formulation EESC that now includes age-of-air dependent fractional release values an spectrum. This can be more appropriately applied various parts stratosphere because this dependence mean age-of-air. provides quantitative estimates directly related inorganic bromine throughout In...
Abstract The term polar vortex has become part of the everyday vocabulary, but there is some confusion in media, general public, and science community regarding what vortices are how they related to various weather events. Here, we clarify meant by atmospheric literature. It important recognize existence two separate planetary-scale circumpolar vortices: one stratosphere other troposphere. These have different structures, seasonality, dynamics, impacts on extreme weather. tropospheric much...
Regions of upper tropospheric equatorial westerly winds, observed over the Pacific and Atlantic Oceans during northern fall to spring, are important for extratropical‐tropical interactions. This paper focuses on one feature these “westerly ducts” that has received relatively little attention date: occurrence Rossby wave breaking events transport tongues extratropical air deep into tropics, mix tropical subtropical air, can affect convection. A climatology “intrusion” formed from 20 years...
The climatological structure, and interannual variability, of the Arctic Antarctic stratospheric polar vortices are examined by analysis elliptical diagnostics applied to over 19 yr potential vorticity data. define area, center, elongation, orientation each vortex used quantify their structure evolution. offer a novel view well-known differences in vortices. Although both form autumn early winter, has shorter life span breaks down month before vortex. There substantial distortion from zonal...
The persistence of the Arctic and Antarctic lower stratospheric vortices is examined over period from 1958 to 1999. Three different vortex‐following diagnostics (two using potential vorticity one based solely on zonal winds) are compared shown give very similar results for breakup date. variability in timing both qualitatively same: There large interannual variations together with smaller decadal‐scale there a significant increase since mid‐1980s (all larger vortex). Also, hemispheres, high...
Abstract. Projections of stratospheric ozone from a suite chemistry-climate models (CCMs) have been analyzed. In addition to reference simulation where anthropogenic halogenated depleting substances (ODSs) and greenhouse gases (GHGs) vary with time, sensitivity simulations either ODS or GHG concentrations fixed at 1960 levels were performed disaggregate the drivers projected changes. These also used assess two distinct milestones returning historical values (ozone return dates) no longer...
Climate change in the Southern Hemisphere (SH) has been robustly documented last several years. It altered atmospheric circulation a surprising number of ways: rising global tropopause, poleward intensification westerly jet, shift storm tracks, expansion Hadley cell, and many others. While these changes have extensively related with anthropogenic warming resulting from increase greenhouse gases, their potential link to stratospheric cooling ozone depletion only recently examined...
We evaluate transport characteristics of two‐ and three‐dimensional chemical models the stratosphere by comparing their simulations mean age stratospheric air propagation annually periodic oscillations in tracer mixing ratio at tropical tropopause into to inferences from situ satellite observations CO 2 , SF 6 water vapor. The models, participants recent NASA “Models Measurements II” study, display a wide range performance. Most propagate annual too rapidly vertical overattenuate signal....
The distribution of anthropogenic carbon (Cant) in the oceans is estimated using transit time (TTD) method applied to global measurements chlorofluorocarbon-12 (CFC12). Unlike most other inference methods, TTD does not assume a single ventilation and avoids large uncertainty incurred by attempts correct for natural background dissolved inorganic measurements. highest concentrations deepest penetration are found North Atlantic Southern Oceans. total inventory 1994 134 Pg-C. To evaluate...
The interaction of two isolated vortices having uniform vorticity is examined in detailed contour dynamics calculations, and quantified using a diagnostic that measures the coherence final state. have identical vorticity, leaving basic parameters determine evolution: radius ratio separation distance. It found term ‘‘vortex merger’’ inadequately describes general takes place. Five regimes are found: (1) elastic interaction, (2) partial straining-out, (3) complete (4) merger, (5) merger....
The fine‐scale structure in lower stratospheric tracer transport during the period of two Arctic Airborne Stratospheric Expeditions (January and February 1989; December 1991 to March 1992) is investigated using contour advection with surgery calculations. These calculations show that Rossby wave breaking an ongoing occurrence these periods air ejected from polar vortex form long filamentary structures. There good qualitative agreement between filaments measurements chemical tracers taken...
Measurements of chemical tracers whose spatial gradients are primarily due to the time dependence sources and/or sinks often used define “tracer ages” in an effort diagnose transport. However, a major problem with interpreting these tracer ages is that different can yield ages, and at present, it not clear what aspects transport measured by tracers. We use concept distribution transit times compare timescales derived from tracers, including CFCs, tritium‐helium, radioactive By performing...