Papers by Darrel Baumgardner
Journal of Geophysical Research, 1995
Stratospheric in situ aerosol and ozone measurements aboard the NASAoperated ER-2 high-altitude r... more Stratospheric in situ aerosol and ozone measurements aboard the NASAoperated ER-2 high-altitude research aircraft from August 1991 to May 1993 provide an opportunity to document the temporal evolution of the correlation between the stratospheric aerosol and the ozone from shortly after the Mount Pinatubo eruption until almost two years later. The observations show that at midlatitudes a linear relationship evolves between aerosol surface (or number) mixing ratios and ozone at altitudes ranging from slightly above the tropopause to 14-16 km. This correlation is linear for values of ozone from 200 to 1300 parts per billion by volume and for potential temperatures between 310 K and 467 K. The linear correlation persisted from late December 1991 until early March 1992 but degraded by October 1992. l lnstitut ffir Physik der Atmosph•ire, Johannes Gutenberg
Atmospheric Research, Oct 1, 2001
A new airborne particle spectrometer has been developed with the same measurement capabilities of... more A new airborne particle spectrometer has been developed with the same measurement capabilities of the Forward Scattering Spectrometer Probes (FSSP) models 100 and 300 (FSSP-300 and FSSP-100), two-dimensional optical imaging probe (2D-OAP), the Multiangle Aerosol Spectrometer Probe (MASP) and hot-wire liquid water probe, but with a single integrated system. The cloud, aerosol and precipitation spectrometer (CAPS) measures particles from 0.35 mm to 1.55 mm in diameter and liquid water content (LWC) from 0.01 to 3 g m À 3 . In addition to combining five probes into one, it measures airspeed at the sample volume and transmits a data stream that requires no special interfaces to communicate with most computers.
Evidence for the presence of SAT in extensive regions of the lower northern stratosphere in the winter of 1992
Eos, Transactions American Geophysical Union, 1993
Meteorological Monographs, 2017
Understanding the formation and evolution of ice in clouds requires detailed information on the s... more Understanding the formation and evolution of ice in clouds requires detailed information on the size, shape, mass, and optical properties of individual cloud hydrometeors and their bulk properties over a broad range of atmospheric conditions. Since the 1960s, instrumentation and research aircraft have evolved, providing increasingly more accurate and larger quantities of data about cloud particle properties. In this chapter, the current status of electrical powered, in situ measurement systems are reviewed with respect to their strengths and weaknesses and their limitations and uncertainties are documented. There remain many outstanding challenges. These are summarized and accompanied by recommendations for moving forward through new developments that fill the remaining information gaps. Closing these gaps will remove the obstacles that continue to hinder our understanding of cloud processes in general and the evolution of ice in particular.
Geophysical Research Letters, Nov 19, 1993
The eruption of the Mt. Pinatubo volcano in the Philippines in June 1991 has resulted in increase... more The eruption of the Mt. Pinatubo volcano in the Philippines in June 1991 has resulted in increases in the surface and mass concentrations of aerosol particles in the lower stratosphere. Airborne measurements made at rnidlatitudes between 15 and 21 km from August 1991 to March 1992 show that, prior to December 1991, the Pinatubo aerosol cloud varied widely in microphysical properties such as size distribution, number, surface and volume concentrations and was also spatially variable. Aerosol surface area concentration was found to be highly correlated to extinction at visible and near-infrared wavelengths throughout the measurement period. Similarly, backscatter at common lidar wavelengths was a good predictor of aerosol volume concentrations. These results support the use of satellite extinction measurements to estimate aerosol surface and of lidar measurements to estimate aerosol volume or mass if temporal changes in the relationships between the variables are considered. Podolske, and A. Weaver, In Situ observations aerosol and C10 after the 1991 eruption ofMt. Pinatubo: effect of reactions on sulfate aerosol, in press, ..Science, 1993.
Journal of Atmospheric and Oceanic Technology, Feb 1, 1995
The microphysical and radiative properties of cirrus clouds continue to be beyond understanding a... more The microphysical and radiative properties of cirrus clouds continue to be beyond understanding and thus still represent one of the largest uncertainties in the prediction of the Earth's climate (IPCC, 2013). Our study aims to provide a guide to cirrus microphysics, which is compiled from an extensive set of model simulations, covering the broad range of atmospheric conditions for cirrus formation and evolution. The model results are portrayed in the same parameter space as field measurements, i.e. in the Ice Water Content-Temperature (IWC-T) parameter space. We validate this cirrus analysis approach by evaluating cirrus data sets from seventeen aircraft campaigns, conducted in the last fifteen years, spending about 94 h in cirrus over Europe, Australia, Brazil as
Performance of the Focused Cavity Aerosol Spectrometer in AASE II
Eos, Transactions American Geophysical Union, 1992
Leveraging multi-band fluorescence monitoring calibrated to track bioaerosols in sensitive indoor environments
ISEE Conference Abstracts, 2013
Atmospheric Measurement Techniques Discussions, 2016
Rapid bioaerosol characterization has immediate applications in the military, environmental and p... more Rapid bioaerosol characterization has immediate applications in the military, environmental and public health sectors. Recent technological advances have facilitated single particle detection of fluorescent aerosol in near real-time; this leverages controlled exposures with single or multiple ultraviolet wavelengths, followed by the characterization of associated fluorescence. This type of Ultravio let induced fluorescence has been used to detect some intact airborne microorganisms in laboratory studies, and has been extended to field studies which implicate bioaerosol to compose a substantial fraction of supermicron atmospheric particles. To enhance the information yield which new generation fluorescence instruments provide, we report the compilation of a systematic referential catalogue including more than fifty pure cultures of common airborne bacteria, fungi and pollens. This catalogue juxtaposes intrinsic optical properties and multiple bandwidths of fluorescence spectra, which...
Journal of Geophysical Research: Atmospheres, 2015
Airborne observations of fluorescent aerosol were made aboard an airship during CloudLab, a serie... more Airborne observations of fluorescent aerosol were made aboard an airship during CloudLab, a series of flights that took place in September and October of 2013 and covered a wideband of longitude across the continental U.S. between Florida and California and between 28 and 37 N latitudes. Sampling occurred from near the surface to 1000 m above the ground. A Wideband Integrated Bioaerosol Sensor (WIBS‐4) measured average concentrations of supermicron fluorescent particles aloft (1 µm to 10 µm), revealing number concentrations ranging from 2.1 ± 0.8 to 8.7 ± 2.2 × 104 particles m−3 and representing up to 24% of total supermicron particle number. We observed distinct variations in size distributions and fluorescent characteristics in different regions, and attribute these to geographically diverse bioaerosol. Fluorescent aerosol detected in the east is largely consistent with mold spores observed in a laboratory setting, while a shift to larger sizes associated with different fluorescen...
Atmospheric Chemistry and Physics Discussions, 2016
Mean properties of individual contrails are characterized for a wide range of jet aircraft as a f... more Mean properties of individual contrails are characterized for a wide range of jet aircraft as a function of age during their lifecycle from seconds to 11.5 hours (7.4 to 18.7 km altitude, -88°C to -31°C ambient temperature), based on a compilation of about 230 previous in-situ and remote sensing measurements. The airborne, satellite, and ground-based observations encompass exhaust contrails from jet aircraft since 1972, and a few older data for propeller aircraft. The contrails are characterized by mean ice particle sizes and concentrations, extinction, ice water content, optical depth, geometrical depth, and contrail width. Integral contrail properties include the cross-section area and total number of ice particles, total ice water content, and total extinction (area-integral of extinction) per contrail length. When known, the contrail-causing aircraft and ambient conditions are characterized. The individual datasets are briefly described, including a few new analyses performed for this study, and compiled together to form a "contrail library" (COLI). The data are compared with results of the Contrail Cirrus Prediction model CoCiP. The observations confirm that the number of ice particles in contrails is controlled by the engine exhaust and the formation process in the jet phase, with some particle losses in the wake vortex phase, followed later by weak decreases with time. Contrail cross-sections grow more quickly than expected from exhaust dilution. The cross-section integrated extinction follows an algebraic approximation. The ratio of volume to effective mean radius decreases with time. The ice water content increases with increasing temperature, similar to non-contrail cirrus, while the equivalent relative humidity over ice saturation of the contrail ice mass increases at lower temperatures in the data. Several contrails were observed in warm air above the Schmidt-Appleman threshold temperature. The "emission index" of ice particles, i.e. the number of ice particles formed in the young contrail per burnt fuel mass, is estimated from the measured concentrations for estimated dilution; maximum values exceed 10 15 kg -1 . The dependence of
Atmospheric Measurement Techniques, 2016
Rapid bioaerosol characterization has immediate applications in the military, environmental and p... more Rapid bioaerosol characterization has immediate applications in the military, environmental and public health sectors. Recent technological advances have facilitated single-particle detection of fluorescent aerosol in near real time; this leverages controlled ultraviolet exposures with single or multiple wavelengths, followed by the characterization of associated fluorescence. This type of ultraviolet induced fluorescence has been used to detect airborne microorganisms and their fragments in laboratory studies, and it has been extended to field studies that implicate bioaerosol to compose a substantial fraction of supermicron atmospheric particles. To enhance the information yield that newgeneration fluorescence instruments can provide, we report the compilation of a referential aerobiological catalogue including more than 50 pure cultures of common airborne bacteria, fungi and pollens, recovered at water activity equilibrium in a mesoscale chamber (1 m 3 ). This catalogue juxtaposes intrinsic optical properties and select bandwidths of fluorescence emissions, which manifest to clearly distinguish between major classes of airborne microbes and pollens.
Atmospheric Chemistry and Physics Discussions, 2015
Microbiome, Jan 9, 2015
A wide variety of specialty textiles are used in health care settings for bedding, clothing, and ... more A wide variety of specialty textiles are used in health care settings for bedding, clothing, and privacy. The ability of textiles to host or otherwise sequester microbes has been well documented; however, their reciprocal potential for liberating airborne bacteria remains poorly characterized. In response, a multi-season survey of bacterial bioaerosols was conducted in the origin and terminus of residual paths which are specifically designed to isolate soiled hospital textiles as they are moved to laundering. This survey used conventional optical particle counting which incorporated multi-channel fluorescence in conjunction with molecular phylogenetic analyses to characterize the bioaerosols liberated during soiled textile storage--immediately before and after the occupation of a modern hospital. Although outfitted with a HEPA filtration system, the number of airborne particles presenting fluorescing optical signatures consistent with airborne bacteria and fungi significantly increa...
In Situ Measurements of Aerosol Particles
Airborne Measurements for Environmental Research, 2013
This chapter contains sections titled: Introduction; Aerosol Particle Number Concentration; Aeros... more This chapter contains sections titled: Introduction; Aerosol Particle Number Concentration; Aerosol Particle Size Distribution; Chemical Composition of Aerosol Particles; Aerosol Optical Properties; CCN and IN; Challenges and Emerging Techniques
Science, 2004
NASA's recent Cirrus Regional Study of Tropical Anvils and Cirrus LayersâFlorida Area Cirru... more NASA's recent Cirrus Regional Study of Tropical Anvils and Cirrus LayersâFlorida Area Cirrus Experiment focused on anvil cirrus clouds, an important but poorly understood element of our climate system. The data obtained included the first comprehensive measurements of aerosols and cloud particles throughout the atmospheric column during the evolution of multiple deep convective storm systems. Coupling these new measurements with detailed cloud simulations that resolve the size distributions of aerosols and cloud particles, we found several lines of evidence indicating that most anvil crystals form on mid-tropospheric rather than boundary-layer aerosols. This result defies conventional wisdom and suggests that distant pollution sources may have a greater effect on anvil clouds than do local sources.
In Situ Observations of Aerosol and Chlorine Monoxide After the 1991 Eruption of Mount Pinatubo: Effect of Reactions on Sulfate Aerosol
Science, 1993
Highly resolved aerosol size distributions measured from high-altitude aircraft can be used to de... more Highly resolved aerosol size distributions measured from high-altitude aircraft can be used to describe the effect of the 1991 eruption of Mount Pinatubo on the stratospheric aerosol. In some air masses, aerosol mass mixing ratios increased by factors exceeding 100 and aerosol surface area concentrations increased by factors of 30 or more. Increases in aerosol surface area concentration were accompanied by increases in chlorine monoxide at mid-latitudes when confounding factors were controlled. This observation supports the assertion that reactions occurring on the aerosol can increase the fraction of stratospheric chlorine that occurs in ozone-destroying forms.
Journal of Geophysical Research: Atmospheres, 1997
Airborne measurements of total reactive nitrogen (NOy) and polar stratospheric cloud (PSC) aeroso... more Airborne measurements of total reactive nitrogen (NOy) and polar stratospheric cloud (PSC) aerosol particles were made in the Antarctic (68øS) as part of the NASA Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign in late July 1994. As found in both polar regions during previous studies, substantial PSC aerosol volume containing NOy was observed at temperatures above the frost point, confirming the presence of particles other than water ice. The composition of the aerosol particles is evaluated using equilibrium expressions for nitric acid trihydrate (NAT), nitric acid dihydrate (NAD), and the supercooled ternary solution (STS) composed of nitric acid (HNO3), sulfuric acid (H2SO4), and water (H20). The equilibrium abundance of condensed HNO3 is calculated for each phase and compared to estimates made using observations of aerosol volume and NOy. The best agreement is found for STS composition, using criteria related to the onset and abundance of aerosol volume along the flight track. Throughout the PSC region, a comparison of the number of particles between 0.4 and 4.0 gm diameter with the number of available nuclei indicates that a significant fraction of the background aerosol number participates in PSC growth. Modeled STS size distributions at temperatures below 191 K compare favorably with measured size distributions of PSC aerosol. Calculations of the heterogeneous loss of chlorine nitrate (C1ONO2) show that the reactivity of the observed PSC surface area is 30 to 300% greater with STS than with NAT composition for temperatures less than 195 K. The total volume of STS PSCs is shown to be more sensitive than NAT to increases in H20, HNO3, and H2SO 4 from supersonic aircraft fleet emissions. Using the current observations and perturbations predicted by the current aircraft assessments, an increase of 50 to 260% in STS aerosol volume is expected at the lowest observed temperatures (190 to 192 K), along with an extension of significant PSC activity to regions -0.7 K higher in temperature. These results improve our understanding of PSC aerosol formation in polar regions while strengthening the requirement to include STS aerosols in studies of polar ozone loss and the effects of aircraft emissions. Introduction Heterogeneous reactions on polar stratospheric clouds (PSCs) play an important role in ozone destruction in both the Arctic and the Antarctic by directly activating chlorine and by 1Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado.
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Papers by Darrel Baumgardner