Impacts of Nucleating Aerosol on Florida Storms. Part I: Mesoscale Simulations

2006 ◽  
Vol 63 (7) ◽  
pp. 1752-1775 ◽  
Author(s):  
Susan C. van den Heever ◽  
Gustavo G. Carrió ◽  
William R. Cotton ◽  
Paul J. DeMott ◽  
Anthony J. Prenni
Keyword(s):  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Supercooled Liquid ◽  
Atmospheric Modeling ◽  
Saharan Dust ◽  
Regional Study ◽  
Surface Precipitation ◽  
Convective Storms ◽  
Mixing Ratios ◽  
High Concentrations

Abstract Toward the end of the Cirrus Regional Study of Tropical Anvils and Cirrus Layer–Florida Area Cirrus Experiment (CRYSTAL–FACE) field campaign held during July 2002, high concentrations of Saharan dust, which can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), and ice-forming nuclei (IFN) were observed over the peninsula of Florida. To investigate the impacts of enhanced aerosol concentrations on the characteristics of convective storms and their subsequent anvil development, sensitivity tests are conducted using the Regional Atmospheric Modeling System (RAMS) model, in which the initialization profiles of CCN, GCCN, and IFN concentrations are varied. These variations are found to have significant effects on the storm dynamics and microphysical processes, as well as on the surface precipitation. Updrafts are consistently stronger as the aerosol concentrations are increased. The anvils cover a smaller area but are better organized and have larger condensate mixing ratio maxima in the cases with greater aerosol concentrations. Cloud water mass tends to increase with increasing aerosol concentrations, with enhanced GCCN concentrations having the most significant influence. Increasing either the GCCN or IFN concentrations produces the most rainfall at the surface whereas enhanced CCN concentrations reduce surface rainfall. Higher IFN concentrations produce ice at warmer temperatures and deeper anvils, but simultaneously increasing the concentrations of CCN and GCCN leads to more supercooled liquid water available for freezing and greater ice mixing ratios. Graupel mixing ratios decrease and hail mixing ratios increase with increasing aerosol concentrations. Higher concentrations of GCCN and IFN result in greater accumulated surface precipitation initially. By the end of the simulation period, however, the accumulated precipitation is the greatest for the case in which the aerosol concentrations are lowest. Such changes in the dynamical and microphysical characteristics of convective storms as a result of the variations in aerosol concentrations have potential climate consequences, both through cloud radiative effects and the hydrological cycle. The impacts of varying CCN, GCCN, and IFN concentrations on the anvils will be discussed more fully in Part II.

Modeling Aerosol Impacts on Convective Storms in Different Environments

2010 ◽  
Vol 67 (12) ◽  
pp. 3904-3915 ◽  
Author(s):  
Rachel L. Storer ◽  
Susan C. van den Heever ◽  
Graeme L. Stephens
Keyword(s):  
Indirect Effects ◽  
Initial Conditions ◽  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Atmospheric Modeling ◽  
Condensation Nuclei ◽  
Surface Precipitation ◽  
Convective Storms ◽  
Cloud Resolving Model ◽  
Regional Atmospheric Modeling

Abstract Aerosols are known to have both direct and indirect effects on clouds through their role as cloud condensation nuclei. This study examines the effects of differing aerosol concentrations on convective storms developing under different environments. The Regional Atmospheric Modeling System (RAMS), a cloud-resolving model with sophisticated microphysical and aerosol parameterization schemes, was used to achieve the goals of this study. A sounding that would produce deep convection was chosen and consistently modified to obtain a variety of CAPE values. Additionally, the model was initiated with varying concentrations of aerosols that were available to act as cloud condensation nuclei. Each model run produced long-lived convective storms with similar storm development, but they differed slightly based on the initial conditions. Runs with higher initial CAPE values produced the strongest storms overall, with stronger updrafts and larger amounts of accumulated surface precipitation. Simulations initiated with larger concentrations of aerosols developed similar storm structures but showed some distinctive dynamical and microphysical changes because of aerosol indirect effects. Many of the changes seen because of varying aerosol concentrations were of either the same order or larger magnitude than those brought about by changing the convective environment.

Homogeneous Ice Nucleation in Subtropical and Tropical Convection and Its Influence on Cirrus Anvil Microphysics

2005 ◽  
Vol 62 (1) ◽  
pp. 41-64 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Larry M. Miloshevich ◽  
Carl Schmitt ◽  
Aaron Bansemer ◽  
Cynthia Twohy ◽  
...  
Keyword(s):  
Homogeneous Nucleation ◽  
Cloud Condensation Nuclei ◽  
Sea Breeze ◽  
Particle Growth ◽  
Ice Nucleation ◽  
Tropical Convection ◽  
Regional Study ◽  
The Core ◽  
Ice Particles ◽  
High Concentrations

Abstract This study uses a unique set of microphysical measurements obtained in a vigorous, convective updraft core at temperatures between −33° and −36°C, together with a microphysical model, to investigate the role of homogeneous ice nucleation in deep tropical convection and how it influences the microphysical properties of the associated cirrus anvils. The core and anvil formed along a sea-breeze front during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL–FACE). The updraft core contained two distinct regions as traversed horizontally: the upwind portion of the core contained droplets of diameter 10–20 μm in concentrations of around 100 cm−3 with updraft speeds of 5–10 m s−1; the downwind portion of the core was glaciated with high concentrations of small ice particles and stronger updrafts of 10–20 m s−1. Throughout the core, rimed particles up to 0.6-cm diameter were observed. The anvil contained high concentrations of both small particles and large aggregates. Thermodynamic analysis suggests that the air sampled in the updraft core was mixed with air from higher altitudes that descended along the upwind edge of the cloud in an evaporatively driven downdraft, introducing free-tropospheric cloud condensation nuclei into the updraft below the aircraft sampling height. Farther downwind in the glaciated portion of the core, the entrained air contained high concentrations of ice particles that inhibit droplet formation and homogeneous nucleation. Calculations of droplet and ice particle growth and homogeneous ice nucleation are used to investigate the influence of large ice particles lofted in updrafts from lower levels in this and previously studied tropical ice clouds on the homogeneous nucleation process. The preexisting large ice particles act to suppress homogeneous nucleation through competition via diffusional and accretional growth, mainly when the updrafts are < 5 m s−1. In deep convective updrafts > 5–10 m s−1, the anvil is the depository for the small, radiatively important ice particles (homogeneously nucleated) and the large ice particles from below (heterogeneously or secondarily produced, or recycled).

A Method for Forecasting Cloud Condensation Nuclei Using Predictions of Aerosol Physical and Chemical Properties from WRF/Chem

2011 ◽  
Vol 50 (7) ◽  
pp. 1601-1615 ◽  
Author(s):  
Daniel Ward ◽  
William Cotton
Keyword(s):  
Hydrological Cycle ◽  
Spatial Scales ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Atmospheric Modeling ◽  
Number Concentration ◽  
Integrated System ◽  
Condensation Nuclei ◽  
Field Campaign ◽  
Physical And Chemical

AbstractModel investigations of aerosol–cloud interactions across spatial scales are necessary to advance basic understanding of aerosol impacts on climate and the hydrological cycle. Yet these interactions are complex, involving numerous physical and chemical processes. Models capable of combining aerosol dynamics and chemistry with detailed cloud microphysics are recent developments. In this study, predictions of aerosol characteristics from the Weather Research and Forecasting Model with Chemistry (WRF/Chem) are integrated into the Regional Atmospheric Modeling System microphysics package to form the basis of a coupled model that is capable of predicting the evolution of atmospheric aerosols from gas-phase emissions to droplet activation. The new integrated system is evaluated against measurements of cloud condensation nuclei (CCN) from a land-based field campaign and an aircraft-based field campaign in Colorado. The model results show the ability to capture vertical variations in CCN number concentration within an anthropogenic pollution plume. In a remote continental location the model-forecast CCN number concentration exhibits a positive bias that is attributable in part to an overprediction of the aerosol hygroscopicity that results from an underprediction in the organic aerosol mass fraction. In general, the new system for predicting CCN from forecast aerosol fields improves on the existing scheme in which aerosol quantities were user prescribed.

scholarly journals Effects of Aerosols as Ice Nuclei on the Dynamics, Microphysics and Precipitation of Severe Storm Clouds

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 783
Author(s):  
Huiling Yang ◽  
Hui Xiao ◽  
Chunwei Guo
Keyword(s):  
Northern China ◽  
Atmospheric Modeling ◽  
Cloud Droplets ◽  
Severe Storm ◽  
Mixing Ratios ◽  
Convective Clouds ◽  
Ice Nuclei ◽  
High Concentrations ◽  
Regional Atmospheric Modeling

The Regional Atmospheric Modeling System (RAMS) is used to investigate the effect of aerosols acting as ice nuclei (IN) on the formation and growth of hydrometeor particles as well as on the dynamics and precipitation of a severe storm in Northern China. The focus of this study is to determine how the overall dynamics and microphysical structure of deep convective clouds are influenced if IN concentrations are somehow altered in a storm environment that is otherwise unchanged. Ice mixing ratios tend to increase and liquid mixing ratios tend to decrease with increasing IN concentrations. High concentrations of IN reduce the mean hail diameter and hail particles with smaller diameters melt more easily, which leads to a decrease in ground hailfall and an increase in surface rainfall. Liquid water plays a more important role in the process of hail formation, while the role of ice particles in the process of hail formation decreases with higher IN concentrations. The role of small cloud droplets in the formation of raindrops is increased and the role of hail melting in the process of raindrops formation is weakened with enhanced IN concentrations. Both latent heat release and absorption significantly increase with increasing IN concentrations. Increasing the concentration of IN by an appropriate amount is beneficial for increasing the total water content and strengthening the updraft, leading to enhancement of a storm, but excessive IN concentrations will inhibit the development of a storm.

scholarly journals A comparison of two chemistry and aerosol schemes on the regional scale and resulting impact on radiative properties and warm and cold aerosol-cloud interactions

2017 ◽  
Author(s):  
Franziska Glassmeier ◽  
Anna Possner ◽  
Bernhard Vogel ◽  
Heike Vogel ◽  
Ulrike Lohmann
Keyword(s):  
Cloud Condensation Nuclei ◽  
Regional Scale ◽  
Cloud Microphysics ◽  
Atmospheric Modeling ◽  
Sulfur Cycle ◽  
Radiative Properties ◽  
Saharan Dust ◽  
Modeling Framework ◽  
Sulfate Production ◽  
Aerosol Module

Abstract. The complexity of the atmospheric aerosol causes large uncertainties in its parameterization in atmospheric models. In a process-based comparison of two aerosol and chemistry schemes within the regional atmospheric modeling framework COSMO-ART, we identify key sensitivities of aerosol parameterizations. We consider the aerosol module MADE in combination with full gas-phase chemistry and the aerosol module M7 in combination with a constant-oxidant-field-based sulfur cycle. For a Saharan dust outbreak reaching Europe, modeled aerosol populations are more sensitive to structural differences between the schemes, in particular the consideration of aqueous-phase sulfate production, the selection of aerosol species and modes and modal composition, than to parametric choices like modal standard deviation and the parameterization of aerosol dynamics. The same observation applies to aerosol optical depth (AOD) and the concentrations of cloud condensation nuclei (CCN). Differences in the concentrations of ice-nucleating particles (INP) are masked by uncertainties between two ice-nucleation parameterizations and their coupling to the aerosol scheme. Differences in cloud droplet and ice crystal number concentrations are buffered by cloud microphysics as we show in a susceptibility analysis.

scholarly journals Uptake of NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> to Saharan dust, ambient urban aerosol and soot: a relative rate study

2010 ◽  
Vol 10 (6) ◽  
pp. 2965-2974 ◽  
Author(s):  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Mineral Dust ◽  
Relative Rate ◽  
Simultaneous Detection ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Ambient Aerosols ◽  
Mixing Ratios ◽  
A Value ◽  
Rate Study ◽  
Absolute Basis

Abstract. The uptake of NO3 and N2O5 to Saharan dust, ambient aerosols and soot was investigated using a novel and simple relative rate method with simultaneous detection of both NO3 and N2O5. The use of cavity ring down spectroscopy to detect both trace gases enabled the measurements to be carried out at low mixing ratios (<500 pptv or 1×1010 molecule cm−3). The uptake coefficient ratio, γ(NO3)/γ(N2O5), was determined to be 0.9±0.4 for Saharan dust, independent of relative humidity, NO3 or N2O5 mixing ratio and exposure time. Ambient (urban) aerosols showed a very limited capacity to take up N2O5 but were reactive towards NO3 with γ(NO3)/γ(N2O5)>15. A value of γ(NO3)/γ(N2O5)~1.5–3 was obtained when using candle generated soot. The relative rate obtained for Saharan dust can be placed on an absolute basis using our recently determined value of γ(N2O5)=1×10−2 to give γ(NO3)=9×10−3, which is significantly smaller than the single previous value. With the present uptake coefficient, reaction of NO3 with mineral dust will generally not contribute significantly to its NO3 loss in the boundary atmosphere or to the nitration of mineral dust.

scholarly journals Three-dimensional evolution of Saharan dust transport towards Europe based on a 9-year EARLINET-optimized CALIPSO dataset

2017 ◽  
Vol 17 (9) ◽  
pp. 5893-5919 ◽  
Author(s):  
Eleni Marinou ◽  
Vassilis Amiridis ◽  
Ioannis Binietoglou ◽  
Athanasios Tsikerdekis ◽  
Stavros Solomos ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Satellite Observation ◽  
Saharan Dust ◽  
Winter Period ◽  
Dust Transport ◽  
The Balkans ◽  
Potential Applications ◽  
The Mediterranean ◽  
Dust Evolution

Abstract. In this study we use a new dust product developed using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and EARLINET (European Aerosol Research Lidar Network) measurements and methods to provide a 3-D multiyear analysis on the evolution of Saharan dust over North Africa and Europe. The product uses a CALIPSO L2 backscatter product corrected with a depolarization-based method to separate pure dust in external aerosol mixtures and a Saharan dust lidar ratio (LR) based on long-term EARLINET measurements to calculate the dust extinction profiles. The methodology is applied on a 9-year CALIPSO dataset (2007–2015) and the results are analyzed here to reveal for the first time the 3-D dust evolution and the seasonal patterns of dust over its transportation paths from the Sahara towards the Mediterranean and Continental Europe. During spring, the spatial distribution of dust shows a uniform pattern over the Sahara desert. The dust transport over the Mediterranean Sea results in mean dust optical depth (DOD) values up to 0.1. During summer, the dust activity is mostly shifted to the western part of the desert where mean DOD near the source is up to 0.6. Elevated dust plumes with mean extinction values between 10 and 75 Mm−1 are observed throughout the year at various heights between 2 and 6 km, extending up to latitudes of 40° N. Dust advection is identified even at latitudes of about 60° N, but this is due to rare events of episodic nature. Dust plumes of high DOD are also observed above the Balkans during the winter period and above northwest Europe during autumn at heights between 2 and 4 km, reaching mean extinction values up to 50 Mm−1. The dataset is considered unique with respect to its potential applications, including the evaluation of dust transport models and the estimation of cloud condensation nuclei (CCN) and ice nuclei (IN) concentration profiles. Finally, the product can be used to study dust dynamics during transportation, since it is capable of revealing even fine dynamical features such as the particle uplifting and deposition on European mountainous ridges such as the Alps and Carpathian Mountains.

scholarly journals Measured and modelled cloud condensation nuclei number concentration at the high alpine site Jungfraujoch

2010 ◽  
Vol 10 (16) ◽  
pp. 7891-7906 ◽  
Author(s):  
Z. Jurányi ◽  
M. Gysel ◽  
E. Weingartner ◽  
P. F. DeCarlo ◽  
L. Kammermann ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Sensitivity Study ◽  
Research Station ◽  
Condensation Nuclei ◽  
Composition Data ◽  
Particle Mobility ◽  
Kohler Theory ◽  
Highly Correlated

Abstract. Atmospheric aerosol particles are able to act as cloud condensation nuclei (CCN) and are therefore important for the climate and the hydrological cycle, but their properties are not fully understood. Total CCN number concentrations at 10 different supersaturations in the range of SS=0.12–1.18% were measured in May 2008 at the remote high alpine research station, Jungfraujoch, Switzerland (3580 m a.s.l.). In this paper, we present a closure study between measured and predicted CCN number concentrations. CCN predictions were done using dry number size distribution (scanning particle mobility sizer, SMPS) and bulk chemical composition data (aerosol mass spectrometer, AMS, and multi-angle absorption photometer, MAAP) in a simplified Köhler theory. The predicted and the measured CCN number concentrations agree very well and are highly correlated. A sensitivity study showed that the temporal variability of the chemical composition at the Jungfraujoch can be neglected for a reliable CCN prediction, whereas it is important to know the mean chemical composition. The exact bias introduced by using a too low or too high hygroscopicity parameter for CCN prediction was further quantified and shown to be substantial for the lowest supersaturation. Despite the high average organic mass fraction (~45%) in the fine mode, there was no indication that the surface tension was substantially reduced at the point of CCN activation. A comparison between hygroscopicity tandem differential mobility analyzer (HTDMA), AMS/MAAP, and CCN derived κ values showed that HTDMA measurements can be used to determine particle hygroscopicity required for CCN predictions if no suitable chemical composition data are available.

scholarly journals Inclusion of biomass burning in WRF-Chem: impact of wildfires on weather forecasts

2011 ◽  
Vol 11 (11) ◽  
pp. 5289-5303 ◽  
Author(s):  
G. Grell ◽  
S. R. Freitas ◽  
M. Stuefer ◽  
J. Fast
Keyword(s):  
Biomass Burning ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Fire Season ◽  
Strong Impact ◽  
Emission Rates ◽  
Weather Forecasts ◽  
High Concentrations ◽  
The Impact

Abstract. A plume rise algorithm for wildfires was included in WRF-Chem, and applied to look at the impact of intense wildfires during the 2004 Alaska wildfire season on weather simulations using model resolutions of 10 km and 2 km. Biomass burning emissions were estimated using a biomass burning emissions model. In addition, a 1-D, time-dependent cloud model was used online in WRF-Chem to estimate injection heights as well as the vertical distribution of the emission rates. It was shown that with the inclusion of the intense wildfires of the 2004 fire season in the model simulations, the interaction of the aerosols with the atmospheric radiation led to significant modifications of vertical profiles of temperature and moisture in cloud-free areas. On the other hand, when clouds were present, the high concentrations of fine aerosol (PM2.5) and the resulting large numbers of Cloud Condensation Nuclei (CCN) had a strong impact on clouds and cloud microphysics, with decreased precipitation coverage and precipitation amounts during the first 12 h of the integration. During the afternoon, storms were of convective nature and appeared significantly stronger, probably as a result of both the interaction of aerosols with radiation (through an increase in CAPE) as well as the interaction with cloud microphysics.

scholarly journals Impacts of Aerosol Particle Size Distribution and Land Cover Land Use on Precipitation in a Coastal Urban Environment Using a Cloud-Resolving Mesoscale Model

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Nathan Hosannah ◽  
Jorge E. Gonzalez
Keyword(s):  
Land Use ◽  
Particle Size ◽  
Land Cover ◽  
Aerosol Particle ◽  
Mesoscale Model ◽  
Cloud Condensation Nuclei ◽  
Atmospheric Modeling ◽  
Urban Environments ◽  
Precipitation Event ◽  
Aerosol Particle Size

Urban environments influence precipitation formation via response to dynamic effects, while aerosols are intrinsically necessary for rainfall formation; however, the partial contributions of each on urban coastal precipitation are not yet known. Here, the authors use aerosol particle size distributions derived from the NASA aerosol robotic network (AERONET) to estimate submicron cloud condensation nuclei (CCN) and supermicron CCN (GCCN) for ingestion in the regional atmospheric modeling system (RAMS). High resolution land data from the National Land Cover Database (NLCD) were assimilated into RAMS to provide modern land cover and land use (LCLU). The first two of eight total simulations were month long runs for July 2007, one with constant PSD values and the second with AERONET PSDs updated at times consistent with observations. The third and fourth runs mirrored the first two simulations for “No City” LCLU. Four more runs addressed a one-day precipitation event under City and No City LCLU, and two different PSD conditions. Results suggest that LCLU provides the dominant forcing for urban precipitation, affecting precipitation rates, rainfall amounts, and spatial precipitation patterns. PSD then acts to modify cloud physics. Also, precipitation forecasting was significantly improved under observed PSD and current LCLU conditions.

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