Search

Die entsprechend der Quellstärke größte Fraktion des atmosphärischen Aerosols ist der natürliche Grobstaub (Seesalz, Mineralstaub und primär biologische Partikel). Nahezu alle natürlichen Grobstaubpartikel in trockener Phase weisen mehr oder weniger starke Abweichungen von der sphärischen Form auf. Der Einfluss der Asphärizität auf die aerodynamischen und optischen Eigenschaften kann durch sogenannte Formfaktoren unter Verwendung einer Referenzgröße berücksichtigt werden. Für wissenschaftliche Fragestellungen, die sowohl auf aerodynamischen wie auch optischen Aspekten beruhen, bedarf es einer vollständigen Betrachtung des Einflusses der Partikelmorphologie, um ein physikalisch plausibles Ergebnis zu erhalten. Gegenstand dieser Arbeit ist die Analyse der Relationen zwischen aerodynamischen und optischen Eigenschaften. Ziel ist die approximative Darstellung der optischen Formfaktoren durch den aerodynamischen Formfaktor als Maßzahl der Asphärizität. Hierfür wurden sowohl geometrische Formparameter als auch aerodynamische und optische Formfaktoren für ein Ensemble von regelmäßigen und unregelmäßigen Partikeln simuliert. Der Approximation der optischen Formfaktoren durch den aerodynamischen Formfaktor werden theoretische Überlegungen und Ergebnisse numerischer Simulationen vorangestellt. Die optischen Formfaktoren sind dabei primär eine Funktion des Größenparameters (Partikelgröße und Wellenlänge) und des aerodynamischen Formfaktors. In Laborexperimenten wurden beide Abhängigkeiten unter Verwendung von Proben mit Partikeln unterschiedlicher Asphärizität validiert. Die resultierende Approximation ermöglicht eine einfache und konsistente Beschreibung des Einflusses der Partikelmorphologie auf die aerodynamischen und optischen Eigenschaften. Dies ist eine unabdingbare Voraussetzung für eine genauere Analyse von Partikeleigenschaften, die aus aerodynamisch und optisch basierten In-situ-Messungen abgeleitet werden.

Die entsprechend der Quellstärke größte Fraktion des atmosphärischen Aerosols ist der natürliche Grobstaub (Seesalz, Mineralstaub und primär biologische Partikel). Nahezu alle natürlichen Grobstaubpartikel in trockener Phase weisen mehr oder weniger starke Abweichungen von der sphärischen Form auf. Der Einfluss der Asphärizität auf die aerodynamischen und optischen Eigenschaften kann durch sogenannte Formfaktoren unter Verwendung einer Referenzgröße berücksichtigt werden. Für wissenschaftliche Fragestellungen, die sowohl auf aerodynamischen wie auch optischen Aspekten beruhen, bedarf es einer vollständigen Betrachtung des Einflusses der Partikelmorphologie, um ein physikalisch plausibles Ergebnis zu erhalten. Gegenstand dieser Arbeit ist die Analyse der Relationen zwischen aerodynamischen und optischen Eigenschaften. Ziel ist die approximative Darstellung der optischen Formfaktoren durch den aerodynamischen Formfaktor als Maßzahl der Asphärizität. Hierfür wurden sowohl geometrische Formparameter als auch aerodynamische und optische Formfaktoren für ein Ensemble von regelmäßigen und unregelmäßigen Partikeln simuliert. Der Approximation der optischen Formfaktoren durch den aerodynamischen Formfaktor werden theoretische Überlegungen und Ergebnisse numerischer Simulationen vorangestellt. Die optischen Formfaktoren sind dabei primär eine Funktion des Größenparameters (Partikelgröße und Wellenlänge) und des aerodynamischen Formfaktors. In Laborexperimenten wurden beide Abhängigkeiten unter Verwendung von Proben mit Partikeln unterschiedlicher Asphärizität validiert. Die resultierende Approximation ermöglicht eine einfache und konsistente Beschreibung des Einflusses der Partikelmorphologie auf die aerodynamischen und optischen Eigenschaften. Dies ist eine unabdingbare Voraussetzung für eine genauere Analyse von Partikeleigenschaften, die aus aerodynamisch und optisch basierten In-situ-Messungen abgeleitet werden.

The overarching, long-term goal of the study was to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals as initially conceived were: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. However, in the course of obtaining the measurements and analyzing them, our goals evolved as it became clear both that some particular tasks were infeasible with the resources available and other goals would be of more value to the overall objective of the study. The specific goals, or objectives, pursued in the study are given below. The sampling platform utilized throughout the study has been the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities.

The overarching, long-term goal of the study is to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals are: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. The sampling platform utilized is the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities. For the current reporting period, our efforts have centered on completing several different analyses utilizing data both from the various CARMA studies, the VOCALS study and additional studies such as SAFARI and DYCOMS, the precise suite of data bases being dependent on the specific analysis. Our objectives for these analyses have changed from those in our original proposal several times, guided by our ongoing analysis., The original document contains color images.

Aerosol particles interact with sunlight through scattering and absorption and have therefore a direct radiative effect. Hygroscopic aerosol particles take up water and are able to grow in size below 100% relative humidity, which involves the change of optical properties and the direct radiative effect. The change of aerosol optical properties for aerosol mixtures under humidification is presently not well understood, especially for the largest particle sources worldwide. The present PhD-thesis quantifies wavelength- and humidity-dependent aerosol optical properties for a mixture of Saharan mineral dust and marine aerosol. For quantification, an aerosol model was developed, which based on in-situ measurements of microphysical and optical properties at Cape Verde. With this model, aerosol optical properties were calculated from the dry state up to 90% relative humidity. To validate the model, a measure of the total extenuated light from particles under ambient conditions was used. Finally, the humidity dependence of aerosol optical properties for marine aerosol, Saharan dust aerosol, and a mixture of both species was described by two empirical equations. With the wavelength of the incident visible solar radiation, relative humidity, and dry dust volume fraction, the humidity dependence of optical properties can be calculated from tabulated values. To calculate radiative effects, aerosol optical properties were used as input parameters for global circulation models including radiative transfer. Due to the complexity of aerosol related processes, they have been treated implicitly, meaning in parameterized form. For modelling purposes, the present PhD-thesis provides a solution to include humidity effects of aerosol optical properties., Aerosolpartikel wechselwirken durch Streu- und Absorptionsprozesse mit der einfallenden Sonnenstrahlung und haben somit einen direkten Strahlungseffekt. Bei relativen Feuchten bis 100% können Aerosolpartikel aufquellen und somit ihre Größe ändern. Im Zuge des Aufquellens, ändern sich die optischen Eigenschaften und somit auch der direkte Strahlungseffekt der Aerosolpartikel. Speziell für Mischungen von verschiedenen Aerosolspezies ist die Änderung der optischen Eigenschaften des Aerosols durch Feuchte Einfuss noch nicht ausreichend verstanden. Gegenstand der vorliegenden Arbeit ist daher die Quantifizierung der wellenlängen- und feuchteabhängigen optischen Eigenschaften einer Mischung von Saharastaub- und marinen Aerosol. Die zur Quantifizierung notwendigen Daten wurden im Rahmen einer Feldmessung von mikrophysikalischen- und optischen Aerosol-Eigenschaften auf den Kapverdischen Inseln gesammelt. Auf Grundlage dieser Messungen wurde ein Aerosol-Modell entwickelt. Dieses Modell wurde daraufhin verwendet, um Berechnungen von optischen Aerosol-Eigenschaften bei relativen Feuchten bis 90% durchzuführen. Eine Messung der Lichtschwächung durch Aerosolpartikel unter Umgebungsbedingungen wurde verwandt, um das Modell bei Umgebungsfeuchten zu validieren. Die Wellenlängen- und Feuchteabhängigkeit der optischen Eigenschaften des Aerosols wurde parametrisiert und konnte anhand von zwei Parametergleichungen bestimmt werden. Unter Benutzung von tabellierten Werten und der Wellenlänge des einfallenden sichtbaren Sonnenlichtes, der relativen Feuchte, sowie der Staubvolumenfraktion, kann die Feuchteabhängigkeit von wichtigen Aerosol-optischen Eigenschaften für Saharastaub, marinen Aerosol und einer Mischung aus beiden Komponenten bestimmt werden. Globale Zirkulationsmodelle, die auch eine Berechnung von Strahlungseffekten durch Aerosolpartikel beinhalten, nutzen Aerosol-optische Eigenschaften als Eingabeparameter. Durch zunehmende Komplexitiät zur Beschreibung von Wechselwirkungen i

Aerosol particles interact with sunlight through scattering and absorption and have therefore a direct radiative effect. Hygroscopic aerosol particles take up water and are able to grow in size below 100% relative humidity, which involves the change of optical properties and the direct radiative effect. The change of aerosol optical properties for aerosol mixtures under humidification is presently not well understood, especially for the largest particle sources worldwide. The present PhD-thesis quantifies wavelength- and humidity-dependent aerosol optical properties for a mixture of Saharan mineral dust and marine aerosol. For quantification, an aerosol model was developed, which based on in-situ measurements of microphysical and optical properties at Cape Verde. With this model, aerosol optical properties were calculated from the dry state up to 90% relative humidity. To validate the model, a measure of the total extenuated light from particles under ambient conditions was used. Finally, the humidity dependence of aerosol optical properties for marine aerosol, Saharan dust aerosol, and a mixture of both species was described by two empirical equations. With the wavelength of the incident visible solar radiation, relative humidity, and dry dust volume fraction, the humidity dependence of optical properties can be calculated from tabulated values. To calculate radiative effects, aerosol optical properties were used as input parameters for global circulation models including radiative transfer. Due to the complexity of aerosol related processes, they have been treated implicitly, meaning in parameterized form. For modelling purposes, the present PhD-thesis provides a solution to include humidity effects of aerosol optical properties., Aerosolpartikel wechselwirken durch Streu- und Absorptionsprozesse mit der einfallenden Sonnenstrahlung und haben somit einen direkten Strahlungseffekt. Bei relativen Feuchten bis 100% können Aerosolpartikel aufquellen und somit ihre Größe ändern. Im Zuge des Aufquellens, ändern sich die optischen Eigenschaften und somit auch der direkte Strahlungseffekt der Aerosolpartikel. Speziell für Mischungen von verschiedenen Aerosolspezies ist die Änderung der optischen Eigenschaften des Aerosols durch Feuchte Einfuss noch nicht ausreichend verstanden. Gegenstand der vorliegenden Arbeit ist daher die Quantifizierung der wellenlängen- und feuchteabhängigen optischen Eigenschaften einer Mischung von Saharastaub- und marinen Aerosol. Die zur Quantifizierung notwendigen Daten wurden im Rahmen einer Feldmessung von mikrophysikalischen- und optischen Aerosol-Eigenschaften auf den Kapverdischen Inseln gesammelt. Auf Grundlage dieser Messungen wurde ein Aerosol-Modell entwickelt. Dieses Modell wurde daraufhin verwendet, um Berechnungen von optischen Aerosol-Eigenschaften bei relativen Feuchten bis 90% durchzuführen. Eine Messung der Lichtschwächung durch Aerosolpartikel unter Umgebungsbedingungen wurde verwandt, um das Modell bei Umgebungsfeuchten zu validieren. Die Wellenlängen- und Feuchteabhängigkeit der optischen Eigenschaften des Aerosols wurde parametrisiert und konnte anhand von zwei Parametergleichungen bestimmt werden. Unter Benutzung von tabellierten Werten und der Wellenlänge des einfallenden sichtbaren Sonnenlichtes, der relativen Feuchte, sowie der Staubvolumenfraktion, kann die Feuchteabhängigkeit von wichtigen Aerosol-optischen Eigenschaften für Saharastaub, marinen Aerosol und einer Mischung aus beiden Komponenten bestimmt werden. Globale Zirkulationsmodelle, die auch eine Berechnung von Strahlungseffekten durch Aerosolpartikel beinhalten, nutzen Aerosol-optische Eigenschaften als Eingabeparameter. Durch zunehmende Komplexitiät zur Beschreibung von Wechselwirkungen i

The overarching, long-term goal of the study is to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals are: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. The sampling platform utilized is the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities. For the current reporting period, our efforts have centered on completing the analysis of the combined data sets we gathered during the CARMA-IV, CARMA-III, and CARMA-II field campaigns, and an analysis of data from the Paposo, Chile site taken during the VOCALS campaign. The source attribution of CCN and aerosol light scattering requires the measurement of both the aerosol chemical composition, aerosol light scattering and the CCN activity., The original document contains color images.

The overarching, log term goal of the study is to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals are: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. The sampling platform utilized is the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities., Code 1 only. The original document contains color images.

The overarching, log term goal of the study is to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals are: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. The sampling platform utilized is the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities., Code 1 only. The original document contains color images.

The overarching, log term goal of the study is to explore the profound effect of aerosol-water interaction both on radiation propagation in, and the thermodynamic structure of, the marine boundary layer. Specific goals are: 1) compile a climatology of aerosol hygroscopicity for use in the NAAPS and COAMPS models, and, further, to develop a model parameterization of hygroscopicity based on aerosol size and composition for such models, 2) explore the relative impacts of cross-inversion mixing and sub-cloud aerosol on cloud thickness and cloud base height, 3) quantify and parameterize the impact of precipitation scavenging on below cloud radiative transfer and cloud liquid water path. The sampling platform utilized is the CIRPAS Twin Otter research aircraft and the venue is the littoral environment off the California coast, representative of areas with high shipping densities.

A new instrument to measure the size-resolved hygroscopic growth of both sub- and super-micron atmospheric aerosol is described. It consists of two white-light optical particle counters measuring the same sample aerosol simultaneously at two different controlled relative humidities. Calibration with aerosols of different refractive index confirms the expected relative insensitivity of the instrument to index of refraction. Data obtained in the field from airborne sampling support the utility of the instrument in measuring differences in size-resolved hygroscopicity in the marine boundary layer and also in addressing the issue of kinetic limitations to aerosol condensational growth.

Associated with the renewal of funding in 2002, and the successful attainment of several of the studies early goals, the current goals of the study have been modified and now include the interaction of marine aerosols with marine boundary layer (MBL) clouds. New goals include: 1) assessment of the relative impacts of purely meteorological and aerosol factors on cloud albedo, 2) determination of the impact of very large CCN on cloud albedo, 3) assessment of the impact of cloud processing on aerosol light scattering, and 4) explore, observationally, the impact of organics on CCN activation in MBL clouds. Additionally, the more general goal of assessing the impact of organics on aerosol hygroscopicity has been retained and, indeed, expanded to include an element of aerosol-cloud interaction. On the other hand, we have curtailed our exploration of the hygroscopicity-organic composition relationship using the POEM code since our work suggests that it is premature to attempt this until measurement of the aerosol size distribution in the super-micron size range is better established.

This DURIP equipment grant is in support of our ongoing grant exploring the interactions of marine aerosols with clouds and the relationship between aerosol size and composition, and aerosol hygroscopicity and cloud condensation nuclei activity (Award # N00014-97-1-0132). Hence, these long-term goals of the parent grant are also those of this grant. However, the DURIP itself is more sharply focused on the fabrication of an instrument to address some of these long term goals, namely, obtaining reliable measurements of both super-micron aerosol particles and their hygroscopicity., The original document contains color images.

Associated with the renewal of funding in 2002, and the successful attainment of several of the studies early goals, the current goals of the study have been modified and now include the interaction of marine aerosols with marine boundary layer (MBL) clouds., The original document contains color images.

Although the importance of the aerosol contribution to the global radiative budget has been recognized, the forcings of aerosols in general, and specifically the role of the organic component in these forcings, still contain large uncertainties. In an attempt to better understand the relationship between the background forcings of aerosols and their chemical speciation, marine air samples were collected off the windward coast of Oahu, Hawaii, during the Rough Evaporation Duct project (RED) using filters mounted on both the Twin Otter aircraft and the Floating Instrument Platform (FLIP) research platform. Laboratory analysis revealed a total of 17 species, including 4 carboxylic acids and 2 carbohydrates that accounted for 74% 6 20% of the mass gain observed on the shipboard filters, suggesting a possible significant unresolved organic component. The results were correlated with in situ measurements of particle light scattering (ssp) at 550 nm and with aerosol hygroscopicities. Principal component analysis revealed a small but ubiquitous pollution component affecting the ssp and aerosol hygroscopicity of the remote marine air. The Princeton Organic-Electrolyte Model (POEM) was used to predict the growth factor of the aerosols based upon the chemical composition. This output, coupled with measured aerosol size distributions, was used to attempt to reproduce the observed ssp. It was found that while the POEM model was able to reproduce the expected trends when the organic component of the aerosol was varied, due to large uncertainties especially in the aerosol sizing measurements, the ssp predicted by the POEM model was consistently higher than observed.

Oxalic acid is the most abundant dicarboxylic acid found in the troposphere, yet there is still no scientific consensus concerning its origins or formation process. Recent studies have suggested mechanisms for its formation in cloud water from gaseous precursors. Comparison of the characteristics of oxalic acidandnss sulfate, a chemical with a known incloud formation pathway, provides some support for an aqueous formation mechanism for oxalic acid. Analysis of the filters collected from the CIRPAS Twin Otter aircraft during CARMA I, a field campaign designed to study the marine stratocumulus off the coast of Monterey, CA, by a five stage Micro-Orifice Impactor (MOI) revealeda peak in the concentration distribution at a diameter of 0.26–0.44 mm, similar to the size distribution found for nss sulfate and corresponding to the droplet mode in the aerosol size distribution. An air-equivalent average of 2.0370.47 mgm 3 (standard error) of sulfate was observed in the collected marine cloud water, in excess to below-cloud concentrations by 1.16 mgm 3 on average. This suggests in-cloudprod uction similar in concentration to previous field campaigns in coastal marine atmospheres. Oxalate was observedin the clouds at air-equivalent concentrations of 0.2170.04 mgm 3, in excess to below-cloudconcentrations by 0.14 mgm 3 andsuggesting an in-cloudprod uction as well. The tentative identification in cloud water of one of the intermediate species in the aqueous oxalate production mechanism lends further support to an in-cloudoxalate source.

Aerosol chemical composition and number size distributions were measured aboard the R/V Ronald H. Brown during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) from 14 March to 20 April 2001. This manuscript focuses on the prefrontal and postfrontal air masses sampled aboard the ship in the Sea of Japan between 6 and 15 April 2001 to illustrate the different chemical sources/mixtures off the coast of Asia resulting from the contrasting meteorological transport patterns. The prefrontal air masses had a dominant accumulation mode composed of pollution and volcanic aerosols. The aerosol was predominately ammonium sulfate and organic carbon. Minor amounts of dust were present in the marine boundary layer (MBL) as a result of subsidence from a pronounced Taklimakan dust aerosol layer aloft. The sea salt in both the submicron and supermicron modes was highly depleted in chloride from reaction with sulfuric and nitric acid vapors. The passage of a large low-pressure center, surrounded by a widespread distribution of airborne dust, on 10 April brought elevated concentrations of submicron and supermicron Gobi desert dust to the ship. The supermicron dust particles contained high concentrations of sulfate, nitrate, organic, and elemental carbon. The MBL aerosol properties and controlling processes described here provide data to evaluate and refine chemical transport models. Copyright 2004 by the American Geophysical Union.