Showing papers on "Microphysics published in 2000"

A New Cloud Physics Parameterization in a Large-Eddy Simulation Model of Marine Stratocumulus

Abstract: A new bulk microphysical parameterization for large-eddy simulation (LES) models of the stratocumulus-topped boundary layer has been developed using an explicit (drop spectrum resolving) microphysical model as a data source and benchmark for comparison. The liquid water is divided into two categories, nonprecipitable cloud water and drizzle, similar to traditional Kessler-type parameterizations. The cloud condensation nucleus (CCN) count, cloud/drizzle water mixing ratios, cloud/drizzle drop concentrations, and the cloud drop integral radius are predicted in the new scheme. The source/sink terms such as autoconversion/accretion of cloud water into/by drizzle are regressed using the cloud drop size spectra predicted by an explicit microphysical model. The results from the explicit and the new bulk microphysics schemes are compared for two cases: nondrizzling and heavily drizzling stratocumulus-topped boundary layers (STBLs). The evolution of the STBL (characterized by such parameters as turbulence...

Particle Scattering by Magnetic Fields

Abstract: The need for a correct quantitative treatment of the interactions between cosmic rays and turbulent magnetic fields continues to be one of the fundamental problems of modern astrophysics. It is the aim of this paper to review new developments in the understanding of mechanisms involved in the scattering of charged particles by magnetic field fluctuations. Special emphasis is given to a comparison of transport parameters determined from the modeling of spacecraft and neutron monitor observation of solar particle events, with theoretical predictions derived from a spectral analysis of simultaneously measured fluctuation spectra. It appears that the traditional quasi-linear theory of particle scattering requires only a slight modification, and the major problem still is our lack of knowledge of the three-dimensional structure of the magnetic turbulence. Possibilities to better reconcile the theory with observations by properly taking into account the microphysics of wave and turbulence aspects of the fluctuations, and to use energetic particles as probes to study certain properties of the magnetic turbulence, are discussed.

An Investigation of Ice Production Mechanisms in Small Cumuliform Clouds Using a 3D Model with Explicit Microphysics. Part I: Model Description

Abstract: A new cloud model that combines a three-dimensional nonhydrostatic dynamical framework with explicit liquid- and ice-phase microphysics and a detailed treatment of ice nucleation and multiplication processes is presented. The use of 28 size bins to describe each cloud drop and ice particle spectra allows the authors to account for all major microphysical processes. A detailed scavenging model has been implemented to calculate the collection rate of contact ice nuclei by cloud drops. In addition to contact nucleation, the model accounts for deposition, condensation-freezing, and immersion ice nucleation mechanisms, as well as for secondary ice production via rime splintering. The model performance is illustrated by a simulation of a New Mexican cumulus cloud. Combination of high 100-m spatial resolution with a new initialization procedure that promotes development of small eddies results in a cloud with a more realistic distribution of liquid water content compared to simulations initialized by th...

Seeding Convective Clouds with Hygroscopic Flares: Numerical Simulations Using a Cloud Model with Detailed Microphysics

Abstract: Numerical experiments were conducted to evaluate the role of hygroscopic flare seeding on enhancement of precipitation in convective clouds. The spectra of seeding particles were based on measurements of the particles produced by hygroscopic flares used in field experiments in South Africa. The seeding effects were investigated by comparing the development of precipitation particles and rain production between the seeded and unseeded cases for clouds with different cloud condensation nuclei (CCN) concentrations and spectra. The South African hypothesis that the introduction of larger and more efficient artificial CCN below cloud base at the early stage of cloud development would influence the initial condensation process in the cloud, resulting in a broader droplet spectrum and in acceleration of the precipitation growth by coalescence, was tested. The results show that the largest seeding particles broaden the cloud droplet distribution near cloud base, leading to an earlier formation of raindro...

The Role of Background Cloud Microphysics in the Radiative Formation of Ship Tracks

Abstract: The authors investigate the extent to which the contrast brightness of ship tracks, that is, the relative change in observed solar reflectance, in visible and near-infrared imagery can be explained by the microphysics of the background cloud in which they form. The sensitivity of visible and near-infrared wavelengths for detecting reflectance changes in ship tracks is discussed, including the use of a modified cloud susceptibility parameter, termed the ‘‘contrast susceptibility,’’ for assessing the sensitivity of background cloud microphysics on potential track development. It is shown that the relative change in cloud reflectance for ship tracks is expected to be larger in the near-infrared than in the visible and that 3.7- mm channels, widely known to be useful for detecting tracks, have the greatest sensitivity. The usefulness of contrast susceptibility as a predictor of ship track contrast is tested with airborne and satellite remote sensing retrievals of background cloud parameters and track contrast. Retrievals are made with the high spatial resolution Moderate Resolution Imaging Spectroradiometer Airborne Simulator flown on the National Aeronautics and Space Administration’s high-altitude ER-2 aircraft, and with the larger-scale perspective of the advanced very high resolution radiometer. Observed modifications in cloud droplet effective radius, optical thickness, liquid water path, contrast susceptibility, and reflectance contrast are presented for several ship tracks formed in background clouds with both small and large droplet sizes. The remote sensing results are augmented with in situ measurements of cloud microphysics that provide data at the smaller spatial scales.

Dynamical and Microphysical Retrievals from Doppler Radar Observations of a Deep Convective Cloud

Abstract: A four-dimensional variational data assimilation system consisting of a three-dimensional time-dependent cloud model with both liquid and ice phase microphysics parameterization was used to assimilate radar data into a cloud model. Data of a severe thunderstorm observed during the Cooperative Huntsville Meteorological Experiment project were assimilated and results compared to a conventional analysis. The analysis system was able to retrieve all the prominent features of the storm, but differed in some of the details. However, the consistency of this retrieval dataset lent credence to the results. It was found that the algorithm was very sensitive to several coefficients in the microphysical and turbulence parameterizations. Simulations proved to be unable to reproduce the evolution of the observed storm even with parameterization coefficients set at values that produce reasonable storm evolutions. This result has implications for short-range forecasting of convective events. Such forecasts require initial fields that currently can only be derived from observations such as used in this study. The problems with assimilating radar observations point to additional work to design parameterizations that allow models to more accurately simulate actual observed storms.

Cloud Microphysics and the Tropical Climate: Cloud-Resolving Model Perspective

Abstract: This paper discusses the role cloud microphysics play in the tropical climate. It is argued that this problem can best be studied within the context of a cloud-resolving model because of complicated interactions among cloud dynamics, cloud microphysics, radiative processes, and surface processes. Two sets of highly idealized cloud-resolving simulations are discussed. In each set, the simulations differ only in the parameters applied in the representation of cloud microphysics. The simulations are run until quasi-equilibrium between sinks and sources of moisture and energy is achieved. The comparisons between simulations applying dramatically different parameters exposes the effects of cloud microphysics on the mean state of the tropical atmosphere and on the tropical climate. The first set considers large-scale flow driven by sea surface temperature gradients and prescribed radiative cooling. The cloud microphysics appears to have minor effects on the large-scale flow as well as temperature and m...

An Investigation of Ice Production Mechanisms in Small Cumuliform Clouds Using a 3D Model with Explicit Microphysics. Part II: Case Study of New Mexico Cumulus Clouds

Abstract: A new 3D model with explicit liquid- and ice-phase microphysics and a detailed treatment of ice nucleation and multiplication processes is applied to study ice formation and evolution in cumulus clouds. Simulation results are compared with in situ observations collected by the National Center for Atmospheric Research King Air aircraft in a cloud over the Magdalena Mountains in New Mexico on 9 August 1987. The model reproduces well the observed cloud in terms of cloud geometry, liquid water content, and concentrations of cloud drops and ice particles (IP). Primary ice nucleation is shown to produce IP in concentrations on the order of 103 m−3 (1 L−1) once the cloud top reaches −10° to −12°C. At mature and early dissipating stages of cloud development, ice production is dominated by the rime-splintering (Hallett–Mossop) mechanism, which in some regions generates up to 5 × 104 m−3 (50 L−1) IP in about 10 min. The predicted maximum of IP concentration is in agreement with observations. The sampling t...

Electrification of Stratiform Regions in Mesoscale Convective Systems. Part II: Two-Dimensional Numerical Model Simulations of a Symmetric MCS

Abstract: Model simulations of a symmetric mesoscale convective system (MCS; observations discussed in Part I) were conducted using a 2D, time-dependent numerical model with bulk microphysics A number of charging mechanisms were considered based on various laboratory studies The simulations suggest that noninductive ice–ice charge transfer in the low liquid water content regime, characteristic of MCS stratiform regions, is sufficient to account for observed charge density magnitudes, and as much as 70% of the total charge in the stratiform region The remaining 30% is contributed by charge advection from the convective region The strong role of in situ charging is consistent with previous water budget studies, which indicate that roughly 70% of the stratiform precipitation results from condensation in the mesoscale updraft Thus both in situ charging and charge advection (the two previously identified hypotheses) appear to be important contributors to the electrical budget of the stratiform region The

Large Eddy Simulation of Shallow Cumulus Convection during BOMEX: Sensitivity to Microphysics and Radiation.

Abstract: A number of large eddy simulations with the Regional Atmospheric Modeling System have been made to study the sensitivity of shallow marine cumulus convection to different microphysics and radiation schemes. In particular, the sensitivity of shallow marine cumulus convection to drizzle and radiation effects, and how drizzle and radiation modify turbulent fluxes, are investigated. It is shown that for the case of prescribed radiative heating, drizzle—albeit very slight—leads to reduced buoyancy fluxes and less turbulence. Consequently, drizzling boundary layers appear to entrain less than their nondrizzling counterpart. Heavy drizzle events are simulated in association with deeper clouds as high as 2 km, even though the majority of clouds are only a few hundred meters deep. A heavier and longer lasting drizzle episode associated with a deeper boundary layer is produced when a two-stream radiative parameterization replaces the prescribed radiative heating in the simulation. Simulated surface precipitation rates agree reasonably well with observations. The greatest alteration in boundary layer structure is obtained when radiative heating interacts explicitly with the broadened drop distribution associated with drizzle formation.

Evolution of the aerosol, cloud and boundary-layer dynamic and thermodynamic characteristics during the 2nd Lagrangian experiment of ACE-2

Abstract: We present observations from the 2nd Aerosol Characterisation Experiment where over a 29-h period between 16–18 July 1997 a tagged column of air was followed by a fully instrumented aircraft. The Lagrangian framework this offered made it possible to measure the evolution of the aerosol size distribution, the cloud structure and microphysics, and the dynamic and thermodynamic structure of the marine boundary layer within a polluted airmass advecting off northwest Europe over the sub-tropical North Atlantic Ocean. The salient observations are presented and analysed. Processes responsible for the evolution are suggested, but quantification of their respective rates must be taken up by future modelling studies. Stratocumulus capped the boundary layer throughout the period that produced negligible washout of aerosol. This implies that the conversion of a continental to a maritime airmass within the cloud-capped sub-tropical marine boundary layer is not controlled by the drizzle process but by entrainment from the free troposphere. We find evidence of processing of aerosol particles by stratocumulus cloud, in particular by aqueous-phase reactions. The processing of the aerosol, realised by modification of the aerosol size distribution in the particle diameter range 0.1–0.5 μm, was complicated by rapid changes in boundary layer height and structure, and also by entrainment of both polluted and relatively clean aerosol from the free troposphere. The cloud microphysics was affected by these changes in the boundary layer aerosol through changes in the cloud condensation nuclei activation spectra. The cloud microphysics was also strongly affected by changes in the dynamics of the boundary layer which included variations (e.g., diurnal) in cloud thickness and an increase in vertical wind speed. Thermodynamic changes within the boundary layer included decoupling due to an increasing sea-surface temperature and a change in the subsidence rate in the free troposphere superimposed on diurnal decoupling. Hypotheses have been devised so that future modellers can focus their efforts to either validate or invalidate potentially important processes. DOI: 10.1034/j.1600-0889.2000.00051.x

Radiative Effects on the Diffusional Growth of Ice Particles in Cirrus Clouds

Abstract: At Colorado State University the Regional Atmospheric Modeling System (RAMS) has been used to study the radiative effect on the diffusional growth of ice particles in cirrus clouds. Using soundings extracted from a mesoscale simulation of the 26 November 1991 cirrus event, the radiative effect was studied using a two-dimensional cloud-resolving model (CRM) version of RAMS, coupled to an explicit bin-resolving microphysics. The CRM simulations of the 26 November 1991 cirrus event demonstrate that the radiative impact on the diffusional growth (or sublimation) of ice crystals is significant. Even in a radiatively cooled atmospheric environment, ice particles may experience radiative warming because the net radiation received by an ice particle depends upon the emission from the particle, and the local upwelling and downwelling radiative fluxes. Model results show that radiative feedbacks on the diffusional growth of ice particles can be very complex. Radiative warming of an ice particle will restri...

Effects of Aerosols on the Radiative Properties of Clouds

Abstract: The influence of anthropogenic aerosols, in the form of ship exhaust effluent, on the microphysics and radiative properties of marine stratocumulus is studied using data gathered from the U.K. Met. Office C-130 and the University of Washington C-131A aircraft during the Monterey Area Ship Track (MAST) experiment in 1994. During the period of MAST, stratocumulus clouds were studied during 11 flights and a wide range of levels of background pollution was observed. The impact of the aerosol emitted from the ships was found to be very dependent on the background cloud microphysical conditions. In clouds of continental influence, the susceptibility of the cloud to further aerosol emissions was low, with a correspondingly weak microphysics and radiation signature in the ship tracks. In clean clouds, changes in droplet concentration of a factor of 2, and reductions in droplet size of up to 50%, were measured. These changes in the microphysics had significant impacts on the cloud radiative forcing. Furthermore, as a result of the cloud droplet size being reduced, in some cases the drizzle was suppressed in the clean clouds, resulting in an increase in liquid water path in the polluted ship track environment. The impact of this combined change in liquid water path and droplet radius was to increase the cloud radiative forcing by up to a factor of 4.

Implications of Microphysics for Cloud-Radiation Parameterizations: Lessons from TOGA COARE

Abstract: A single-column model (SCM) and observational data collected during TOGA COARE were used to investigate the sensitivity of model-produced cloud properties and radiative fluxes to the representation of cloud microphysics in the cloud-radiation parameterizations. Four 78-day SCM numerical experiments were conducted for the atmospheric column overlying the COARE Intensive Flux Array. Each SCM experiment used a different cloud-radiation parameterization with a different representation of cloud microphysics. All the SCM experiments successfully reproduced most of the observed temporal variability in precipitation, cloud fraction, shortwave and longwave cloud forcing, and downwelling surface shortwave flux. The magnitude and temporal variability of the downward surface longwave flux was overestimated by all the SCM experiments. This bias is probably due to clouds forming too low in the model atmosphere. Time-averaged model results were used to examine the sensitivity of model performance to the differe...

Precipitation parameterization in a simulated Mei-Yu front

Abstract: Observational and numerical studies have consistently shown the importance of latent heat release associated with frontal precipitation in the development of a Mei-Yu front. However, a systematic evaluation of precipitation parameterization in the simulation of a Mei-Yu front has been rare in the literature. In order to enhance our understanding on precipitation parameterization of Mei-Yu fronts, this study conducts numerical experiments to evaluate the performance of subgrid-scale cumulus schemes and resolvable-scale microphysics schemes to simulate the Mei-Yu frontal system on 4-5 June 1998 at grid resolutions of 45 km and 15 km, using the Penn State/NCAR mesoscale model MM5. Principal findings are summarized here. The horizontal extent and intensity of precipitation, the partitioning off precipitation into grid-resolvable and subgrid-scale portions, the vertical thermodynamic profile in the precipitation region and the embedded mesoscale structure are extremely sensitive to the choice of cumulus parameterization schemes. This is true for both the 45- and 15-km grids. The partitioning of precipitation into subgrid scale and resolvable scale is sensitive to the particular cumulus parameterization that is used in the model, but it is nearly the same on both the 4S- and IS-km grids for a given cumulus parameterization. The detailed ice-phase microphysical processes do not have a significant impact on the rainfall pattern on either the 45- and 15-km grids. However, the inclusion of cloud ice-snow-graupel microphysical processes increases the total surface precipitation amount by 30% compared to the amount with only warm raid processes. Variations in the subgrid-scale cumulus parameterization have a much larger impact on the distribution and amount of Mei-Yu frontal precipitation than do variations in the resolvable-scale microphysics parameterization at mesoscale grid resolutions of 10-50 km.

Observations of microphysics pertaining to the development of drizzle in warm, shallow cumulus clouds

Abstract: The evolution of drizzle in small cumulus clouds in a subtropical environment was studied. Observations were made using three instrumented aircraft, a ground-based radar, and a 95 GHz airborne Doppler radar during the Small Cumulus Microphysics Study in east central Florida in summer 1995. Data from six clouds, from two days, are examined in this paper. Both sets of clouds were less than 2 km in depth at observation times; in-cloud temperatures were > 10 °C. Droplet spectra observed in these clouds were generally bi-modal. The sizes of the droplets within the large mode are consistent with growth through condensation. It remains unclear how droplets within the small mode formed, but their existence appears to be tied to entrapment and mixing. Drizzle drops (drops with diameters > 50 μm) were found at all levels in the clouds. The penetration-averaged concentrations of drizzle drops were less than 15 L−1, except in the uppermost regions of clouds on one of the days where drizzle drop concentrations exceeded 100L−1. In general, the presence of drizzle drops in the upper regions of the clouds is consistent with models of droplet growth through condensation and stochastic collection. The existence of drizzle at low and mid-levels may be due to collection initiated by ultra-giant aerosols, or to the redistribution of drizzle drops from neighbouring or earlier cloud elements.

The Estimation of Hydrometeor Profiles from Wideband Microwave Observations

Abstract: Profiles of the microphysical properties of clouds and raincells are essential in many areas of atmospheric research and operational meteorology. In order to enhance the understanding of the nonlinear and underconstrained relationships between cloud and hydrometeor microphysical profiles and passive microwave brightness temperatures, estimations of cloud profiles for an anvil, a convective, and an updraft region of an oceanic squall were performed. The estimations relied on comparisons between radiative transfer calculations of incrementally estimated microphysical profiles and concurrent dual-altitude wideband brightness temperatures from the 22 February 1993 flight during TOGA-COARE. The wideband observations (10--220 GHz) are necessary for estimating cloud profiles reaching up to 20 km. The low frequencies enhance the rain and cloud water profiles, while the high frequencies are required to detail the higher altitude ice microphysics. A microphysical profile was estimated for each of the three regions of the storm. Each of the three estimated profiles produced calculated brightness temperatures within approximately 10 K of the observations. A majority, of the total iterative adjustment were to the estimated profile's frozen hydrometeor characteristics and were necessary to match the high frequency calculations with the observations. This indicates a need to validate cloud resolving models using high frequencies. Some difficulties matching the 37 GHz observation channels on the DC-8 and ER-2 aircrafts with the calculations simulated at the two aircraft heights (approximately 11 km and 20 km, respectively) were noted and potential causes presented.

Microphysical and radiative properties of inhomogeneous stratocumulus: Observations and model simulations

Abstract: Detailed microphysical observations made from aircraft during the Atlantic Stratocumulus Transition Experiment are used to examine the optical properties of marine stratocumulus. Special attention is given to the relationship between the droplet size distribution (droplet-number concentration, effective radius, and liquid-water content) and the optical extinction parameter. The extinction parameter calculated with measurements from the forward-scattering spectrometer probe (FSSP) differs only slightly from the extinction parameter obtained from the total droplet spectrum (measured with two optical probes, FSSP and 260X). In contrast, the results for the effective radius and the liquid-water content show differences up to 40% between the two spectra. A Monte Carlo radiative-transfer model is initialized with optical properties calculated from the observed microphysics. Monte Carlo simulations of radiative fluxes are in good agreement with observations for well-mixed boundary-layer cloud fields.

Cloud Droplet Residual Particle Microphysics in Marine Stratocumulus Clouds Observed during the Monterey Area Ship Track Experiment

Abstract: The effect of marine boundary layer pollution level (as determined by the aerosol particle number concentration) on the size distribution of aerosol particles that formed cloud droplets in marine stratiform clouds is examined. In situ measurements of cloud droplet residual particles with a counterflow virtual impactor during the Monterey Area Ship Track experiment are presented. The variation in residual particle size distribution and number concentration in clouds that formed in marine boundary layers with different pollution levels are discussed. The measurements show a constant shape of the residual particle size distributions for the variety of pollution levels encountered, even though the aerosol number concentration varied by up to a factor of 6. The measurements indicate that particles smaller than 0.1-μm radius controlled cloud droplet number concentrations in the clouds investigated. From literature values of the maximum supersaturations encountered in stratocumulus clouds, one can estim...

Spectral signature of column solar radiation absorption during the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE)

Abstract: Spectral and broadband shortwave radiative flux data obtained from the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE) are compared with 3-D radiative transfer computations for the cloud field of October 30, 1995. Because the absorption of broadband solar radiation in the cloudy atmosphere deduced from observations differs from that modeled by 135 W m−2, we performed a consistency analysis using spectral observations and the model to integrate for wavelengths between the spectral observations. To match spectral measurements, aerosols need a reduction in both single-scattering albedo (from 0.938 to 0.82) and asymmetry factor (from 0.67 to 0.61), and cloud droplets require a threefold increase in coalbedo. Even after modifying the model inputs and microphysics the difference in total broadband absorption is still of the order of 75 W m−2. Finally, an unexplained absorber centered near 1.06 μm appears in the comparison that is much too large to be explained by any known atmospheric process.

Evaluation of radar retrieval algorithms in stratiform clouds using large-eddy simulations

Abstract: The performance of algorithms retrieving cloud liquid water content W from radar reflectivity factor Z is evaluated using data from a three-dimensional large-eddy simulation model with detailed size-resolving microphysics. On the basis of case studies of a marine stratocumulus cloud observed during the Atlantic Stratocumulus Transition Experiment in June of 1992 and a continental stratus cloud observed over north central Oklahoma on April 30, 1994, it is shown that retrieval algorithms based only on Z are very sensitive to cloud microphysics and do not reproduce adequately the horizontally averaged vertical profile of W. Additional independent measurements are needed to constrain the retrieved W profile. Surprisingly, algorithms show little improvement when the exact concentrations of cloud droplets obtained from the model are included in the calculations. Vertically integrated liquid water path P is found to be a robust constraint that ensures a more accurate retrieval. In the two studied cases an algorithm based on the Z-W relation of the form Z = a W b gives an optimal performance when a is inversely proportional to P and b = 1.32. The horizontal averaging of P over a computational domain of several kilometers does not affect the accuracy of the retrieval of the horizontally averaged profile of cloud liquid water content, which adds to the versatility of the algorithm.

Some impact of pollutants on the development and optical properties of stratocumulus clouds

Abstract: Two major recent field programmes-the European Cloud Radiation Experiment (EUCREX) and the Aerosol Characterization Experiment II (ACE-2)-have extensively analysed the dynamical, microphysical and radiative attributes of stratocumulus clouds contaminated by continental air Although an extensive set of dynamical and microphysical data are now available, there are no accounts of any matching theoretical modelling studies To fully understand and numerically model the interplay between the dynamics, microphysics, radiative and chemical properties of the two clouds chosen for our case-studies would require a full three-dimensional large-eddy simulation (LES) model coupled to a full-size resolving microphysical model where the computational costs would be prohibitive In this study we have optimized' the classic Kessler parametrization scheme so that it is effectively able to distinguish between clean and contaminated clouds We perform LES runs with the optimized scheme to study the morphology and the dynamics of the clouds and then use a second one-dimensional microphysical parcel model run with identical environmental conditions to study the effects of pollution on the clouds as well as the droplet spectral evolution This procedure yields extremely good agreement with observations at modest computational expense It is shown that nitric acid (HNO 3 ) vapour in the parts per billion by volume (ppbv) range affects cloud formation by increasing the number of cloud droplets and decreasing the mean size compared to an acid-free simulation The effects of HNO 3 contamination on the EUCREX case-study is evident owing to the proximity of this cloud to sources of air pollutants With 10 ppbv of HNO 3 , we are able to achieve good agreement with the observations of the droplet effective radii as well as with observations of the optical-depth variation For the ACE-2 cloud which formed further away from sources of pollutants, even on a typical polluted' day when the ambient HNO 3 was ∼5 parts per trillion by volume, the drop concentration was found to be insensitive to changes in the HNO 3

Modelling and observations of aerosol properties in the clean and polluted marine boundary layer and free troposphere

Abstract: The characteristic time of many of the microphysical aerosol processes is days up to several weeks, hence longer than the residence time of the aerosol within a typical atmospheric compartment such as the marine boundary layer, the free troposphere etc. To understand aerosol properties, one cannot confine the discussion to such compartments. This paper presents simulations using a box model that describes aerosol microphysics within the context of atmospheric dynamics that connects those compartments. The model results for a Clean Marine and Polluted Continental air mass are compared to observations.