K. Minschwaner

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Papers by K. Minschwaner

Spatio-temporal variability of the polar middle atmosphere. Insights from over 30 years of research satellite observations

2007), An analysis of the regulation of tropical tropospheric water vapor

[1] We use a simple trajectory model to investigate the mechanisms that regulate mid- and upper-t... more [1] We use a simple trajectory model to investigate the mechanisms that regulate mid- and upper-tropospheric humidity. Our model advects water passively and contains no microphysics other than the requirement that water vapor is immediately removed so as to prevent the relative humidity from ever exceeding 100%. We demonstrate that our model accurately reproduces H2O measurements made by the Atmospheric Infrared Sounder onboard NASA’s Aqua satellite. Our results show that, given the large-scale circulation of the troposphere, detailed microphysics need not be included in order to accurately simulate H2O. We have also identified three preferred regions where air parcels in the mid and upper troposphere experience their final dehydration. The first is in the equatorial upper troposphere and is associated with convective outflow at the top of the tropical Hadley circulation. Final dehydration of air that detrains at potential temperature q above 340 K (10 km) predominantly occurs here. The other two regions are found at lower altitudes in the midlatitudes of both hemispheres and are associated with dehydration during isentropic excursions to midlatitudes. Final dehydration of air that detrains at q below 340 K predominantly occurs here. Finally, we analyze the water budget of the dry eastern Pacific subtropics and find that dehydration in both the equatorial upper troposphere and the midlatitudes contribute to the dryness there.

Absorption of Solar Radiation by 02 ' Implications for 03 and Lifetimes of N 2 O , CFC 13 , and CF 2 C 12

An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge ba... more An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of 02 on transmission of ultraviolet radiation. Allowing also for absorption in the Herzberg continuum, the model is shown to provide a reliable simulation of observed transmission i the spectral interval 192 to 200 nm. The model is used to evaluate rates for photolysis of N20, CFC13, and CF2C12, and to infer global loss rates (1.22x 10 •ø kg N yr -• , 7.21 x107 and 3.04x107 kg C1 yr -•, respectively) and instantaneous lifetimes (123, 44, and 116 years, respectively) appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission i the Schumann-Runge r gion is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxy...

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The photochemical production and loss rates for carbon monoxide ( CO ) in the stratosphere and mesosphere are evaluated using measurements from the Aura Microwave Limb

The photochemical production and loss rates for carbon monoxide (CO) in the stratosphere and meso... more The photochemical production and loss rates for carbon monoxide (CO) in the stratosphere and mesosphere are evaluated using measurements from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). The distributions of reactive trace gases involved in the photochemistry of CO, including OH, CH 4 , O( 1 D), Cl, as well as temperatures for calculating reaction rates, are either directly observed or constrained from observations. We map the CO net production and loss as a function of pressure (10-0.02 hPa, about 30-75 km altitude), latitude (approximately ±70°), and season. The results indicate that photochemical loss dominates over production for nearly all conditions considered here. A minimum photochemical loss lifetime of about 10 days occurs near the 2 hPa pressure level, and it follows the region of maximum sunlight exposure. At high latitudes during winter, the CO lifetime is generally longer than 30 days. Time scales become much shorter in spring, however, when CO lifetimes can be 15-20 days poleward of 60°latitude in the upper stratosphere. On the basis of these results, CO is a suitable tracer during autumn to spring above the 0.1 hPa pressure level but not in the upper stratosphere near 1 hPa.

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Detection and Classification of Ozone Laminae Using Vertical Profiles of Ozone and Potential Temperature

Signature of a tropical Pacific cyclone in the composition of the upper troposphere over Socorro, NM

Geophysical Research Letters, 2015

We present a case study based on balloon‐borne ozone measurements during the SouthEast American C... more We present a case study based on balloon‐borne ozone measurements during the SouthEast American Consortium for Intensive Ozonesonde Network Study in August–September 2013. Data from Socorro, NM (34°N, 107°W) show a layer of anomalously low ozone in the upper troposphere (UT) during 8–14 August. Back trajectories, UT jet analyses, and data from the Microwave Limb Sounder (MLS) on the Aura satellite indicate that this feature originated from the marine boundary layer in the eastern/central tropical Pacific, where several disturbances and one hurricane (Henriette) formed within an active region of the Intertropical Convergence Zone in early August 2013. The hurricane and nearby convection pumped boundary layer air with low ozone (20–30 ppbv) into the UT. This outflow was advected to North America 3–5 days later by a strong subtropical jet, forming a tongue of low ozone observed in MLS fields and a corresponding layer of low ozone in Socorro vertical profiles.

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SPARC-IGAC Symposium on Climate-Chemistry Interactions. Climate Feedback by Water Vapor in the Tropical Upper Troposphere

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Observations of the Upper Tropospheric Water Vapor Feedback in UARS MLS and HALOE Data

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The Tropical Water Vapor Feedback Implied by Aqua Observations

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On the regulation of tropical tropospheric water vapor

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Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses

Atmospheric Chemistry and Physics, 2015

We present a comprehensive comparison of polar processing diagnostics derived from the National A... more We present a comprehensive comparison of polar processing diagnostics derived from the National Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim). We use diagnostics that focus on meteorological conditions related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics, and air parcel trajectories to evaluate the effects these reanalyses might have on polar processing studies. Our results show that the agreement between MERRA and ERA-Interim changes significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases improves. By comparing our diagnostics during five time periods when an increasing number of higher-quality observations were brought into these reanalyses, we show how changes in the data assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many of our stratospheric temperature diagnostics show a convergence toward significantly better agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as the winter mean volume of air with temperatures below polar stratospheric cloud formation thresholds (V PSC ) and some diagnostics of polar vortex size and strength, do not show improved agreement between the two reanalyses in recent years when data inputs into the DAS were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim agree much better than those calculated from earlier reanalysis data sets. We still, however, see fairly large differences in many of the diagnostics in years prior to 2002, raising the possibility that the choice of one reanalysis over another could significantly influence the results of polar processing studies. After 2002, we see overall good agreement among the diagnostics, which demonstrates that the ERA-Interim and MERRA reanalyses are equally appropriate choices for polar processing studies of recent Arctic and Antarctic winters.

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Satellite observations and modelling of transport in the upper troposphere through the lower mesosphere during the 2006 major stratospheric sudden arming

Atmospheric Chemistry and Physics Discussions, 2009

An unusually strong and prolonged stratospheric sudden warming (SSW) in January 2006 was the firs... more An unusually strong and prolonged stratospheric sudden warming (SSW) in January 2006 was the first major SSW for which globally distributed long-lived trace gas data are available covering the upper troposphere through the lower mesosphere. We use Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) data, the SLIMCAT Chemistry Transport Model (CTM), and assimilated meteorological analyses to provide a comprehensive picture of transport during this event. The upper tropospheric ridge that triggered the SSW was associated with an elevated tropopause and layering in trace gas profiles in conjunction with stratospheric and tropospheric intrusions. Anomalous poleward transport (with corresponding quasi-isentropic troposphereto-stratosphere exchange at the lowest levels studied) in the region over the ridge extended well into the lower stratosphere. In the middle and upper stratosphere, the breakdown of the polar vortex transport barrier was seen in a signature of rapid, widespread mixing in trace gases, including CO, H 2 O, CH 4 and N 2 O. The vortex broke down slightly later and more slowly in the lower than in the middle stratosphere. In the middle and lower stratosphere, small remnants with

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Intra-annual variations and trends of HOx and the ratio of HO2/OH

The middle atmospheric OH and HO2 are known for their important roles in catalytic HOx reaction c... more The middle atmospheric OH and HO2 are known for their important roles in catalytic HOx reaction cycles (involving OH, HO2, and H) that destroy ozone. Since OH and HO2 are mainly produced through photolysis, their variations and trends are strongly affected by solar forcing. These variations and trends have to be understood for a better understanding of the related variability in middle atmospheric O3. The Microwave Limb Sounder (MLS) on board the Aura satellite, launched in July 2004, provides the first simultaneous global measurements for OH and HO2 on a daily basis, making it possible to investigate the variability in these species and the partitioning between them. This study focuses on the intra-annual variability of daytime HOx, which is a combined result of the solar forcing (solar zenith angle change during the course of year) and the seasonal variation of the source species of HOx (such as O3 and H2O). In addition, the longer-term ( 5 - 6 years) trends will also be showed, i...

Ozone over New Mexico; a 25 Day Intensive Ozonesonde Campaign

ABSTRACT

A comparison of clear-sky OLR between CERES measurements and model calculations and the dependence of OLR on temperature and water vapor

We compare nighttime clear-sky outgoing longwave radiation (OLR) from a model calculation against... more We compare nighttime clear-sky outgoing longwave radiation (OLR) from a model calculation against measurements from the Clouds and the Earth's Radiant Energy System (CERES) data set. Our model calculation is driven by profiles of temperature and water vapor from the Atmospheric Infrared Sounder (AIRS). Using several different radiative transfer models, we find an offset between the model and measurements, with

Radiative constraints on the energy budget of the tropical atmosphere

Planetary and Space Science, 1992

Abstract A simple one-dimensional model is presented to describe the energy budget of the tropica... more Abstract A simple one-dimensional model is presented to describe the energy budget of the tropical atmosphere. Heating of the atmosphere is associated primarily with latent energy released due to precipitation in localized regions of intense cumulonimbus activity. Air transported to upper regions of the troposphere by cumulonimbus systems is returned to the surface over a large region of descent. Heat released by subsidence is balanced primarily by emission of radiation in the infrared. The model accounts for this energy balance, exploring specifically the constraints on permissible fluxes of mass and energy. Results suggest that the strength of the background subsidence field in the tropics may be sensitive to surface temperature and to changes in atmospheric composition, specifically variations in the altitude distribution of H 2 O and changes in the abundance of greenhouse gases such as CO 2 . The mean level of detrainment of deep cumulonimbus clouds is found to increase with increasing surface temperature. This behavior is shown to be sensitive to atmospheric composition. The surface temperature for an atmosphere containing twice the present level of CO 2 is predicted to increase by 1.4K, about 25% less than the change obtained with models in which the lapse rate of temperature is specified at lower altitudes, where assumptions of radiative equilibrium would lead otherwise to a statically unstable condition. Buoyancy considerations suggest that there may be an upper limit to the range of permissible values for surface temperature in the tropics. Models in which the subsidence mass flux is assumed constant with respect to altitude are found to be unable to maintain buoyancy for rising air in the face of heat released by descent when surface temperatures exceed about 312K.

The photochemistry of carbon monoxide in the stratosphere and mesosphere evaluated from observations by the Microwave Limb Sounder on the Aura satellite

Journal of Geophysical Research, 2010

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Evidence for a recurring eastern North America upper tropospheric ozone maximum during summer

Journal of Geophysical Research: Atmospheres, 2007

Daily ozonesondes were launched from 14 North American sites during August 2006, providing the be... more Daily ozonesondes were launched from 14 North American sites during August 2006, providing the best set of free tropospheric ozone measurements ever gathered across the continent in a single season. The data reveal a distinct upper tropospheric ozone maximum above eastern North America and centered over the southeastern USA. Recurring each year, the location and strength of the ozone maximum is influenced by the summertime upper tropospheric anticyclone that traps convectively lofted ozone, ozone precursors and lightning NOx above the southeastern USA. The North American summer monsoon that flows northward along the Rocky Mountains is embedded within the western side of the anticyclone and also marks the westernmost extent of the ozone maximum. Removing the influence from stratospheric intrusions, median ozone mixing ratios (78 ppbv) in the upper troposphere (>6 km) above Alabama, near the center of the anticyclone, were nearly twice the level above the U.S. west coast. Simulatio...

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An analysis of the dependence of clear‐sky top‐of‐atmosphere outgoing longwave radiation on atmospheric temperature and water vapor

Journal of Geophysical Research: Atmospheres, 2008

We have analyzed observations of clear‐sky top‐of‐atmosphere outgoing longwave radiation (OLR) me... more We have analyzed observations of clear‐sky top‐of‐atmosphere outgoing longwave radiation (OLR) measured by the Clouds and the Earth's Radiant Energy System (CERES). These measurements were obtained during March 2005 at night and over the ocean and cover latitudes from 70°N to 70°S. First, we compare the OLR measurements to OLR calculated from two radiative transfer models. The models use as input simultaneous and collocated measurements of atmospheric temperature and atmospheric water vapor made by the Atmospheric Infrared Sounder (AIRS). We find excellent agreement between the models' predictions of OLR and observations, well within the uncertainty of the measurements. We also analyze the sensitivity of OLR to changing surface temperature Ts, atmospheric temperature Ta, and atmospheric water vapor q. We find that OLR is most sensitive to unit changes in Ta when that change occurs in the lower troposphere. For q, the altitude distribution of sensitivity varies between the mi...

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Observation of enhanced ozone in an electrically active storm over Socorro, NM: Implications for ozone production from corona discharges

Journal of Geophysical Research: Atmospheres, 2008

Enhancements in ozone were observed between about 3 and 10 km altitude within an electrically act... more Enhancements in ozone were observed between about 3 and 10 km altitude within an electrically active storm in central New Mexico. Measurements from satellite sensors and ground‐based radar show cloud top pressures between 300 and 150 mb in the vicinity of an ozonesonde launched from Socorro, NM, and heavy precipitation with radar reflectivities exceeding 50 dBZ. Data from a lightning mapping array and a surface electric field mill show a large amount of electrical activity within this thunderstorm. The observed ozone enhancements are large (50% above the mean) and could have resulted from a number of possible processes, including the advection of polluted air from the urban environments of El Paso and Juarez, photochemical production by lightning‐generated NOx from aged thunderstorm outflow, downward mixing of stratospheric air, or local production from within the thunderstorm. We find that a large fraction of the ozone enhancement is consistent with local production from corona dis...

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