3. RESEARCH STRATEGY
The ACE-1 scientific objectives will be addressed in several activities during the intensive measurement campaign
and during the transit flights and cruise between the United States and Australia. Six research questions, outlined
in section 2.1, have been defined to address these objectives. The strategies for answering these 6 questions are
outlined in this chapter. Chapter 5 contains the specific approaches that will be used to implement these
strategies, with the necessary instruments and platforms described in Chapter 4.
The ACE-1 scientific objectives and related research questions are directed toward the overall ACE goal: to provide
the necessary data to incorporate aerosols into global climate models and to reduce the uncertainty in the
calculation of climate forcing by aerosols. A critical part of aerosol radiative forcing calculations involves
relating the size-dependent chemical composition of aerosols to their radiative impact. In models, this module
makes the critical link between anthropogenic changes in the chemical composition of the atmosphere and the
associated impact on the Earth's radiation budget. Questions 1 and 2 address Objective 1 and are meant to provide
data to test and validate aerosol/climate models on local and column-integrated scales.
Process studies are also needed to evaluate the factors controlling the sources, formation and fate of aerosols and
the way these processes affect the number size distribution, chemical composition, and radiative and cloud
nucleating properties of the particles. Questions 3, 4 and 5 address Objective 2 and relate to models of the natural
biogeochemical processes that create atmospheric sulfate and its precursors and the processes that control the
aerosol population. Finally, question 6, which addresses Objective 3, integrates the closure experiments and
process studies into models on a variety of scales.
A simultaneous chemical, physical and radiative characterization of the atmospheric aerosol is needed to develop and
test model calculations of aerosol radiative effects and to refine and validate the algorithms used to interpret
satellite observations of the aerosol (Penner et al., 1994). These measurements will be made from ground, ship and
aircraft platforms (Figure 2) during the intensive experiment and during the transit flights (north and south bound)
and cruise (south bound only) between the
Figure 3. NCAR C-130 and NOAA Discoverer track lines for the transits between the United States and Australia.
The
C-130 will stop in Anchorage, Alaska; Oahu, Hawaii; Christmas Island; Pago Pago, American Samoa; and Christchurch,
New Zealand. The total transit will require about 2 weeks of time and will yield a free tropospheric latitudinal
transect of gas and aerosol measurements from approximately 78°N to 70°S. Measurements will also be made on the
north-bound transit with stops in Brisbane, Australia; Nadi, Fiji Islands; Christmas Island; Hilo, Hawaii; and
Moffett Field, California. The ship transit from Seattle to Hobart will require 28 days and will yield a boundary
layer trans-Pacific transect of gas and aerosol measurements from 48°N to 43°S. Measurements will be made only on
the south-bound transit.
US and Australia (Figure 3). To validate these measurements the Aerosol Characterization Experiments will attempt to
obtain "closure" between the various parameters. These closure studies will over-determine aerosol properties or
related processes using a variety of measurement and modelling techniques in order to examine the internal
consistency of these different measurement and modelling strategies. The closure experiments have four specific
goals:
1. to estimate measurement uncertainties from the internal consistencies of the data set,
2. to test the validity of models to predict:
a) aerosol radiative properties based on Mie theory and measurements of chemical and physical aerosol properties and
b) cloud nucleating properties based on Khler theory and measurements of chemical and physical aerosol and cloud
properties,
3. to test and calibrate remotely sensed and indirectly determined aerosol properties for use in climate models,
4. to identify areas where improvements in instrumentation or modelling are needed.
These closure experiments fall into two broad classes, local closure and column closure.
3.1.1 Local closure
A local closure experiment is one in which all measurements are made at a single location and time. Several
local closure experiments are required to address uncertainties in the estimated climate forcing by sulfate
aerosols. The unknowns include the aerosol mass scattering efficiency, aerosol hemispheric backscatter fraction,
fractional increase in aerosol scattering efficiency due to hygroscopic growth, and parameters affecting aerosol
activation (Penner et al., 1994). All of these experiments relate to one specific question:
- Can the measured physical and chemical properties of the aerosol be used to predict the radiative and cloud
nucleating properties of that same aerosol?
To address this question the following seven intercomparisons of measured and calculated parameters will be
made during ACE-1:
1. Aerosol mass as a function of particle size derived from the number size distribution, chemical analysis of
aerosol species and gravimetric analysis.
Key measurements for each prediction include the aerosol number concentration and chemical composition as a function
of particle size. It is important, therefore, to validate these measurements and to estimate their uncertainty.
This comparison will address the internal consistency of these measurements, i.e., can the chemically analyzed mass
account for the total aerosol mass? Is the mass derived from the aerosol chemical size distribution consistent with
that from the aerosol number size distribution? Measurements of total gravimetric aerosol mass, chemically analyzed
mass, and mass derived from the number size distribution will be made simultaneously.
2. Measured hygroscopic response of the aerosol size to changes in relative humidity (RH) and the hygroscopic
response calculated from the measured aerosol number and chemical mass size distributions, RH and published
functional relationships between chemical composition and water uptake.
This intercomparison adds an additional step of complexity to intercomparison 1 by varying the total water content
of the aerosol. It will address the ability to parameterize the response of ambient aerosol to changes in RH. The
hygroscopic growth characteristics of the aerosol will be measured directly with a tandem differential mobility
analyzer (TDMA) (McMurry and Stolzenberg, 1989) and gravimetrically in equilibrium with a range of humidities (Hnel,
1979).
3. Measured aerosol scattering and calculated aerosol scattering derived from Mie theory applied to measured number
and chemical mass size distributions.
This intercomparison directly addresses the uncertainty in determining the aerosol/climate parameters of aerosol
mass scattering efficiency and aerosol hemispheric backscatter fraction. Scattering and backscattering of visible
light by particles will be measured directly with an integrating nephelometer. These direct measurements of light
scattering properties will be compared with independent predictions from the aerosol number and chemical mass size
distributions, some simplifying assumptions (e.g. spherical particle shape, an externally mixed aerosol, particle
refractive index, and density), and Mie theory.
4. Measured increase in aerosol scattering due to hygroscopic growth and the calculated increase based on measured
number and chemical mass size distributions, RH, and published functional relationships between particle chemical
composition and water uptake.
This intercomparison adds an additional step of complexity to intercomparison 3 by varying the total water content
of the aerosol. It will address the aerosol/climate parameter of fractional increase in aerosol scattering
efficiency due to hygroscopic growth. Two nephelometers will be operated in parallel, to measure directly the
scattering and backscattering of visible light by particles at a low reference RH (40%) and at a higher RH. The
increase in aerosol scattering due to the aerosol hygroscopic growth will be independently calculated using the data
from intercomparisons 2 and 3.
5. Measured CCN supersaturation spectrum, the CCN supersaturation spectrum derived from Khler theory applied to the
measured aerosol number and chemical mass size distributions, the CCN supersaturation spectrum derived from TDMA
growth factors, and the CCN super-saturation spectrum derived from cloud droplet number concentration.
This intercomparison will address questions of aerosol activation that affect the indirect radiative influence of
aerosols on climate. The droplet-nucleating potential of the aerosol population will be measured directly with a
thermal diffusion cloud chamber that subjects the aerosol to a variety of supersaturations and counts the number of
droplets that are nucleated. This defines the number concentration of cloud condensation nuclei (CCN) as a function
of the supersaturation spectrum, CCN(S%). Growth times will be assessed to determine whether the particles are
obtaining a dynamic or equilibrium response. The supersaturation spectrum of the aerosol population will be
predicted independently by three methods. The first prediction will use the aerosol number and inorganic and
organic chemical mass size distribution, certain simplifying assumptions (e.g. an externally mixed aerosol and
insoluble content), and Khler theory. The second prediction will use the aerosol growth characteristics determined
from the TDMA (intercomparison 2). Finally, the supersaturation spectrum will be derived from the cloud-base
droplet number concentration, cloud microphysics and cloud structure.
6. Measured cloud droplet number concentration just above cloud base and the cloud droplet number concentration
calculated from the measured updraft velocity, aerosol number size distribution, aerosol chemical composition, and
CCN supersaturation below cloud base.
This intercomparison adds the complexity of real clouds to the measurements of intercomparison 5. It tests the
ability of cloud microphysical models to predict cloud droplet number concentrations from properties of the
sub-cloud aerosol as well as the suitability of parameterizations of cloud droplet number concentration used in
global-scale models. The methods used to determine the CCN supersaturation spectrum do not reproduce the
time-history of supersaturation encountered in real clouds. The cloud droplet size distribution just above cloud
base (but high enough to be above the level of peak supersaturation) will be calculated using the observed updraft
velocity in two ways, from the measured CCN supersaturation spectrum and from the measured aerosol size distribution
and chemical composition. The extent of agreement between the measured and calculated droplet number concentrations
and size distributions will provide a valuable indicator of the suitability of current models and measurement
approaches for representing the initial stages of cloud droplet nucleation and growth.
7. Measured index of refraction and index of refraction derived from the measured aerosol number and chemical mass
size distributions, RH and published functional relationships between chemical composition and water uptake.
This intercomparison will address an important link between the physical and chemical properties of the aerosol.
The multiangle scattering probe (MASP) determines light scattering at two angles from every particle counted. The
scattering data from the MASP can be used to calculate the particle index of refraction. These calculations of
refractive index will be compared with independent predictions using the measured aerosol number and chemical mass
size distributions, RH and published functional relationships between chemical composition and water uptake.
Needed measurements (local closure):
Aerosol number and mass (chemical and gravimetric) distributions
Aerosol size (number distribution and/or mass) at a range of humidities
Aerosol scattering and backscattering at a range of humidities
Cloud droplet number distribution
CCN supersaturation spectrum
Aerosol index of refraction
3.1.2 Column closure
A column closure experiment extends the local (zero-dimensional) closure to multiple altitudes (one-dimensional
closure) in order to compare and calibrate satellite and surface based column-integrated radiation measurements with
in-situ (aircraft) aerosol chemical, physical and radiative measurements. Specifically,
- Can the measured physical and chemical properties of the aerosol in a vertical column be used to accurately
predict the integrated effect of aerosols on radiative transfer?
During ACE-1, in-situ measurements of particle scattering at several altitudes will be used to
compute the clear-sky column-integrated particle scattering. An airborne aerosol lidar will be used to scale the
in-situ measurements over appropriate altitude intervals and to identify any layering that the in-situ
measurements might have missed. This column aerosol scattering derived from in-situ measurements will be
compared with estimated aerosol optical depths from the AVHRR satellites and from ground and ship sunphotometers.
The column closure experiments thus provide an important data base with which to test and calibrate remotely sensed
and indirectly determined aerosol properties for climate models.
Apart from the direct effect of aerosols on climate, aerosols in the lower atmosphere are known to control climate
indirectly through their influence on the cloud droplet number concentration. The depth of the cloud, together with
the cloud droplet number concentration define cloud optical depth (essentially cloud column closure) which is a
quantity closely related to cloud albedo. By observing aerosol below clouds, cloud droplets at several levels
inside the clouds, and up- and down-welling short-wave radiation above clouds, a unique data set is obtained linking
subcloud aerosol to a climate parameter (cloud albedo) in the pristine environment of the Southern Ocean.
Furthermore, cloud albedo is a parameter which can be retrieved from satellite observations. Thus, the in-situ data
set can be used to test optical depth retrieval algorithms. Although the instrumentation aboard the C-130 is not
optimized for cloud studies, some flight time will be devoted to this research effort.
Column closure experiments are also needed for reasons totally unrelated to climate. The impact of atmospheric
aerosol scattering must be estimated and corrected for in order to derive information such as water-leaving
radiances from satellite sensors. The atmospheric correction algorithms that have been developed for this purpose
(Gordon and Wang, 1994) require assumptions about the nature and concentration of the aerosol and its resulting
integrated radiative impact. The ACE-1 column closure experiments will help to improve the aerosol/radiative
corrections. The transit flights between the United States and Australia will provide aerosol chemical and physical
data to improve the regional aerosol corrections.
The area near Cape Grim, Tasmania was chosen for ACE-1 in part because it provides an opportunity to characterize
the natural aerosol and hence a background from which to quantify anthropogenic perturbations. However, measuring
aerosol radiative effects in this background low-optical-depth case (0.04 to 0.05; Forgan, 1990; Durkee et al.,
1991) presents a significant challenge requiring extremely careful calibrations and intercalibrations. Current
optical instruments (nephel-ometers and sunphotometers) are capable of making accurate and precise measurements in
this region, but the signal to noise ratio will be small.
To provide a contrasting natural high-optical-depth case to validate the column closure experimental approach, two
additional experiments will be conducted near Hawaii on the transit to Australia. The first experiment will use the
Kilauea volcano plume that provides a well-contained, soot-free source of sulfate aerosols with optical depths of
0.1 and higher. The degassing associated with Kilauea's ongoing eruptive phase (since 1983) constitutes a point
source for sulfur gases and associated sulfate aerosol into the relatively pristine atmosphere of the central
Pacific. The plume provides a strong signal that is readily detected by satellite (Porter et al., 1994) and
in-situ measurements (Quinn et al., 1990). Consequently, a radiative closure experiment carried out both during
descent through the plume and in the adjacent clean air will provide a range of responses for the in-situ
instrumentation aboard the C-130, including the specific effect of markedly increased sulfate concentrations
superimposed on a background aerosol. The direct comparison with adjacent clean air will help to quantify the
importance of aerosol sulfate in aerosol extinction and will help to refine the algorithms needed to interpret
satellite data by providing data at a much larger aerosol optical depth.
The second test of the column closure experimental approach will be performed near Hawaii over the SeaWiFS optical
mooring (Hooker et al., 1992). This mooring provides long-term time series comparisons between in-situ and
satellite measurements of normalized water-leaving radiance and hence provides an opportunity to intercalibrate the
C-130 optical measurements with the future SeaWiFS sensors.
Needed measurements (column closure):
AVHRR radiances
Water-leaving radiances
Upward and downward radiances measured at several altitudes
Aerosol number and mass distributions at several altitudes
Aerosol radiative properties at several altitudes
Aerosol optical depth spectra for the column above those altitudes
Lidar observations of aerosol scattering profiles above and below the aircraft altitudes at as many wavelengths as
possible
Cloud droplet number distribution
CCN supersaturation spectrum
3.2 Process studies
Determine the key physical and chemical processes controlling the formation and fate of
aerosols
and how these processes affect the number size distribution, the chemical composition, and the radiative and cloud
nucleating properties of the particles.
Three specific questions will be addressed as part of ACE-1 in order to quantify the key biological, chemical and
physical processes controlling the source, trans-formation and fate of aerosol particles in the marine boundary
layer. The questions along with relevant background information and measurements needed to study each problem are
outlined in the following discussion.
3.2.1 Biological DMS production and air-sea exchange
- What are the biological, chemical, and physical processes controlling the concentration of DMS in surface
seawater and its flux to the atmosphere?
The background sulfate aerosol over the oceans is largely derived from DMS (Charlson et al., 1987). To
evaluate the importance of this natural aerosol source and to predict how this source may change with a changing
climate, climate models require quantitative descriptions of the biological, chemical, and physical processes that
are involved. At this time, the processes controlling DMS production and air-sea exchange are highly uncertain.
DMS is one component of an active seawater sulfur cycle (Bates et al., 1994). The precursor of DMS, DMSP
(dimethylsulfonium propionate), is produced by many phytoplankton species as an osmolyte. During phytoplankton
senescence and/or grazing DMSP is released to the water column and enzymatically cleaved to DMS and other sulfur
compounds. DMS can be lost from the water column by air-sea exchange, microbial consumption, or photochemical
oxidation. The factors controlling the rate of DMS cycling in surface seawater and hence its seawater concentration
strongly affect the amount of DMS that is released to the atmosphere.
The 1991 Pacific Sulfur-Stratus Investigation (PSI) and the 1992 Pacific IGAC-MAGE cruise included studies of the
major sulfur reservoirs in surface seawater and the rates of exchange between these reservoirs. The results have
shown that in the temperate North Pacific, air-sea exchange is a very small sink for seawater DMS. In contrast, the
rates of air-sea exchange, microbial consumption and photochemical oxidation in the Equatorial Pacific are very
similar to each other. Similar experiments will be conducted in the South Pacific as part of ACE-1 intensive.
The air-sea flux of DMS is the starting point of the marine atmospheric sulfur cycle and thus limits the production
of sulfate aerosol. The need to improve measurements and models of air-sea exchange led IGAC to create the MAGE
activity and is one of the major motivators behind ACE-1. During the equatorial Pacific IGAC/MAGE 1992 experiment,
this flux was calculated by two independent methods: seawater DMS concentrations coupled with air-sea exchange
models and the atmospheric diurnal cycle of DMS concentrations coupled with atmospheric photochemical models
(Thompson et al., 1993; Yvon et al., 1994). ACE-1 investigators will repeat this approach during ACE-1 by measuring
the concentrations of seawater and atmospheric DMS and the photochemically important atmospheric parameters. DMS
surface fluxes will also be determined from the Lagrangian sulfur budget analysis (section 3.2.2).
The ocean surface can also be a source of ammonia and organic material, both of which are potentially important in
aerosol formation and growth. Fluxes of these species will be estimated based on air-sea exchange and micro-budget
techniques.
Needed measurements:
Seawater sulfur species (DMSP, DMS, DMSO, total organic sulfur)
Rate measurements of DMSP consumption, DMS production, DMS microbial consumption
Seawater chlorophyll, pigment and nutrient concentrations
Phytoplankton speciation
Atmospheric DMS concentrations
Atmospheric photochemically active species (CO, CH4, NMHC, H2O2, NO, NO2, NOy, and O3)
Meteorological data (wind speed, boundary layer height, etc.).
3.2.2 Gas phase sulfur chemistry
- What are the rates and efficiencies of the processes controlling DMS and SO2
oxidation in the marine boundary layer?
The oxidation rates and conversion efficiencies of the various sulfur species are critical input parameters
for calculating sulfate aerosol column burdens in aerosol/climate models (Langner and Rodhe, 1991; Erikson et al.,
1991; Benkovitz et al., 1994; Tarrason et al., 1995). While the oxidation of DMS is the presumed driving force for
the production of submicron marine aerosols, the details of this process are still controversial. Although
virtually all published models assume a high efficiency for conversion of DMS to SO2 and nss sulfate, some
observations suggest that the efficiency could be quite small and that SO2 may not even be a major participant
(Bandy et al., 1992; Huebert et al., 1993). Is SO2 the principal product of DMS oxidation? Is any nss sulfate
formed directly? How important is the oxidation pathway that forms DMSO, which is soluble and could be readily
dry-deposited, thus removing DMS-derived sulfur from the atmosphere? What fraction of the SO2 in the marine
boundary layer is removed through deposition to the ocean surface and onto seasalt particles and what fraction is
oxidized to sulfate aerosol? Answers to these questions require field observations that will challenge mechanistic
models.
Lagrangian experiments offer tremendous potential for studying these atmospheric oxidation processes and chemical
budgets. During the Atlantic Stratocumulus Transition Experiment (ASTEX), the MAGE Science Team tested a Lagrangian
experimental approach for observing changes in the chemical species in the marine boundary layer near the Azores.
Initial results suggest that this approach can yield process information without the confounding effects of air mass
changes. The Lagrangian strategy will continue to be developed during ACE-1 and will include gas phase DMS, DMSO,
DMSO2, SO2, methanesulfonic acid (MSA), and H2SO4 and particulate phase MSA and SO4. This suite of measurements, in
a region far from anthropogenic SO2 sources, will provide data to quantify rates and efficiencies of DMS and
SO2oxidation.
A variety of measurements are needed to clarify the oxidation and removal pathways of marine boundary layer sulfur.
For the Lagrangian observations the measurements will be repeated in the same airmass over a period of two days.
Needed measurements:
Seawater and atmospheric DMS concentrations
Gas phase DMS oxidation products (DMSO, DMSO2, SO2, MSA, H2SO4)
Photochemically active species concentrations (CO, CH4, NMHC, H2O2, NO, NO2, NOy, and O3)
Measurements of both sub- and super-micron nss sulfate and MSA.
Mass size distributions of nss sulfate and MSA.
Number size distributions from 3 nm to 10 mm diameter.
Air mass trajectories using smart balloons.
3.2.3 Aerosol nucleation, growth, and deposition
- What are the rates and efficiencies of the processes controlling the nucleation, growth, distribution and
removal of particles in the remote marine atmosphere?
The partitioning of DMS oxidation products between new particle production and particle growth will affect
the sub-micron aerosol size distribution and, in turn, the effect of these particles on climate. Parameters that
determine whether gaseous species condense to form new particles or condense onto existing particles include the
saturation vapor pressure of the condensing species (H2SO4, MSA, and NH3), RH, temperature, and the existing
particle number concentration and surface area.
The marine boundary layer aerosol generally offers a large amount of surface area upon which gases such as H2SO4 can
condense. It is therefore a rare event when the condensable vapors reach sufficiently high supersaturations to
nucleate new particles in large concentrations (Covert et al., 1992). Since precipitation, cloud processing, and
coagulation are continually removing particle number, some source of new particles is needed to explain why the
total number remains relatively constant over time.
Observations of high ultra-fine particle (3nm < Dp < 20nm) number concentrations in the clean upper tropospheric air
and process-model calculations suggest that this region may be a source of new nuclei (Ito, 1985; Clarke, 1993; Raes
et al., 1993). Air in cumulus updrafts may be scavenged of nearly all its aerosol mass, resulting in an air mass
with low particle surface area. In addition, low temperatures at these altitudes reduce saturation vapor pressures,
thus promoting bursts of nucleation, followed by coagulation. Subsidence and entrainment can then bring these fresh
nuclei into the boundary layer.
During ACE-1 measurements of the number size distribution between 3 and 600 nm diameter will be used to identify
events of new particle production in both the marine boundary layer and free troposphere. By also measuring gas
phase aerosol precursors it should be possible to directly compute aerosol nucleation and growth rates. Chemical
mass size distributions, the ammonium to nss sulfate molar ratio as a function of size, and single particle analysis
will be used to determine the role of specific chemical species in new particle production. These same measurements
will be used to define conditions that inhibit particle production.
In addition to homogeneous nucleation and subsequent growth through condensation, the aerosol size distribution can
be transformed by cloud processing. Sub-micron aerosols can cycle through non-precipitating clouds many times
before being removed from the atmosphere through rain (Hoppel et al., 1986). During a cycle, the larger particles
are activated and become cloud droplets. In addition, gas phase species and smaller particles can be absorbed into
the droplets. When the cloud droplet evaporates, the residue is larger than the original particle. The result is a
size distribution that contains two sub-micron peaks, one due to homogeneous nucleation and one due to cloud
cycling. A thin layer of stratocumulus clouds often exists over the proposed study region providing an opportunity
to investigate the effect of cloud cycling on the size distribution. These measurements will be used to estimate
the fraction of sulfur species oxidized in cloud.
The final stage in the atmospheric aerosol cycle is removal by wet or dry deposition. Although it will not be
possible to conduct an extensive deposition experiment, deposition rates will be estimated using precipitation
collectors. These deposition rates will be compared with calculated deposition fluxes and aerosol formation rates.
These rates can be used to calculate the average lifetime of atmospheric sulfate, a parameter that has a high
uncertainty factor in estimates of the climate forcing by sulfate aerosols (Penner et al., 1994).
Needed measurements:
Gas phase precursors: H2SO4, MSA, NH3.
Mass size distribution of the major cations, anions, and organic species.
The ammonium to nss sulfate molar ratio from 10 to 600 nm diameter.
Single particle analysis and TDMA measurements to determine internal/external mixing
Single particle analysis to identify other chemical components of the aerosol
Number size distribution from 3 to 10000 nm diameter.
CCN number concentration at the supersaturation of stratocumulus clouds.
Satellite measurements of the degree of cloud cover.
Estimates of the mixing time into clouds and the rainfall rate.
Measurements of wet deposition.
Temperature and RH.
3.3 Modelling activities
Assess the climatic importance of remote marine aerosols.
- How can observations be used to improve the accuracy of aerosol-climate models?
The climatic importance of the atmospheric aerosol requires improved paramet-erization of the processes that
control the aerosol sources, properties, evolution, and spatial distribution. While satellites offer observations
on a planetary scale, they lack any capability for chemical analysis of the aerosol particles and for coupling the
spatial distribution of the aerosol to spatially and temporally variable aerosol precursors and source processes.
Modelling of the aerosol system, including gaseous precursors and sources, aerosol production processes and
properties, and the three dimensional spatial and temporal distribution offers the only possibility for coupling
locally measured properties to global forcing and effects.
The observational data collected during ACE-1 will be useful for testing and improving a hierarchy of related models
(Penner et al., 1994):
Detailed process models to describe DMS production and air-sea exchange, atmospheric gas and liquid phase
chemical reaction rates and aerosol and cloud microphysical processes and properties,
One-dimensional single column models to evaluate the performance of process parameterizations and to provide
information on the vertical profiles of aerosol parameters needed for radiative transfer calculations,
Cloud scale three-dimensional large-eddy simulation (LES) models with explicit cloud microphysics to assess the
interaction between clouds and aerosols,
Regional and global three-dimensional models to reveal the geographical and temporal distributions of the
aerosol.
Rather than simply providing the modelling community with data, ACE-1 is being planned in concert with members of
the modelling community to ensure that the data will be useful for validating and refining models.