ATMOSPHERIC SCIENCES DIVISION

Program Summaries - 2006

AEROSOL CLOUD INTERACTIONS: FIELD STUDIES AND INTERPRETATION

EE-025-EECA [KP1202010]

The primary focus of this proposal is to provide an enhanced scientific basis for specifying the relationship between: aerosol, chemical, and physical properties, and their properties as cloud condensation nuclei (CCN); CCN and cloud-droplet microphysics; and, cloud-droplet microphysics and the initiation of drizzle in warm clouds. Aerosol activation, droplet formation, and drizzle production will be studied using the Department of Energy (DOE) G-1 aircraft as the primary measurement platform. The intention is to make measurements in diverse environments containing the major categories of aerosols that need to be represented in General Circulation Models (GCMs). Because of the necessity to separately identify anthropogenic impacts, the studies will start with urban, industrial, and power plant aerosol sources. The selection of proposed field venues also includes marine and biogenic organic environments. To make optimum use of the G-1 aircraft, it is proposed that aerosol/CCN studies be done during clear-air flights designed to investigate aerosol direct radiative effects. Separate field studies are proposed for the in-cloud work. In recognition of the fact that computational constraints dictate a compact description of aerosol composition and cloud microphysics, the focus is on determining the essential features of aerosols that need to be incorporated into GCMs to predict aerosol indirect effects.

CHARACTERIZATION OF AEROSOL ORGANIC MATTER: DETECTION, FORMATION AND OPTICAL AND RADIATIVE EFFECTS

EE-088-EECA [KP1202010]

P.I.: Yin-Nan Lee

A detailed understanding of organic aerosols regarding sources, formation, and properties is needed to improve the ability to predict atmospheric distributions of aerosol particles and to assess their radiative effects. A rapid on-line technique coupling a particle-into-liquid sampler (PILS) and a total organic carbon detector (TOCD) for measuring the TOC and water-soluble organic carbon (WSOC) in aerosol particles at a time resolution of better than one minute suitable for aircraft measurement will be developed. Using the fast data obtained, the rates of secondary organic aerosol formation in environments of different emission characteristics will be determined and compared to photochemical model predictions for mechanistic insights. The contributions of TOC and WSOC to the simultaneously determined aerosol properties, including hygroscopicity, light scattering, and cloud condensation nuclei (CCN) formation will be investigated to identify the roles of the organics in the aerosols direct and indirect radiative effects. In addition, the so-called humic-like substances (HULIS), which account for an appreciable fraction of WSOC, will be characterized to gain an understanding of their sources and effects.

CORE MEASUREMENTS FOR FIELD PROGRAMS

EE-090-EECA [KP1202010]

P.I.: Stephen R. Springston

This proposal is to provide a core set of field measurements essential to the study of aerosol-radiative forcing and its effects on climate. Existing research-grade instruments will be operated on behalf of the program for aerosol precursors, atmospheric oxidants, aerosol microphysical properties, aerosol composition, and ancillary trace gases. This equipment has been field-proven and meets the unique requirements of aircraft-based sampling. Multiple associated infrastructure activities are an important component of this proposal and include providing quality assurance, aircraft installation, trained operators, ‘first-look’ data in the field, final-data reduction and archival distribution of final-form results. To meet the needs of Atmospheric Science Program (ASP) goals, the instrument systems supported through this proposal will be expanded to encompass anticipated measurement capabilities as required by climate-related aerosol studies.

MODELING AEROSOL PROCESSES IN THE DOE ATMOSPHERIC SCIENCE PROGRAM

EE-093-EECA [KP1202010]

P.I.: Stephen R. Springston

Representing the processes responsible for aerosol loading, geographical distribution, and microphysical properties in chemical-transport models is essential to demonstrating understanding of these processes, to quantifying that understanding, to attributing aerosols to responsible source types, locations, and processes and, ultimately, to determining the influence of aerosols on climate and climate change. This project develops, applies, and evaluates aerosol-microphysical modules based upon a variety of designs and modeling approaches. Host gridded models of varying dimensionality (1-, 2-, and 3-dimensional) are used, where appropriate, specifically, including the Community Multiscale Air Quality (CMAQ) Modeling System for urban-to-regional scale modeling, which is well-suited for interchanging alternative modules for various processes, and the Brookhaven National Laboratory (BNL) Global Chemistry Model driven by Observation-derived meteorology (GChM-O). Novel methods are utilized to incorporate field measurements in host models. A key deliverable will be a new aerosol module for simulation of generally-mixed aerosols based on the quadrature method of moments. Model application and evaluation will focus on the locations and time periods of field projects to be conducted within the United States (US) Department of Energy (DOE) Atmospheric Science Program (ASP) and rely heavily on measurements conducted in those field projects. This project supports the ASP functional category "fundamental theoretical and process modeling" and addresses, primarily, the science category "transformation of particles and gaseous precursors".

SHORTWAVE RADIATIVE INFLUENCES OF TROPOSPHERIC AEROSOLS

EE-424-EECA [KP1202030]

P.I.: Stephen E. Schwartz

This project consists of experiments with data from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site to determine direct and indirect (through modification of cloud properties) aerosol shortwave radiative forcing and its relation to aerosol properties – column-optical depth, mass loading, scattering coefficient, and size distribution at the surface and vertically, when available. Examination will be made of aerosol influences on microphysical properties of clouds principally by remote-sensing techniques, and of resultant radiative forcing. Parameterizations of aerosol light-scattering properties necessary to describe aerosol forcing will be developed and evaluated. Uncertainty in shortwave forcing due to anthropogenic aerosols, which is presently estimated at about -1 watts per square meter, global average, uncertain by at least a factor of 2. In industrialized regions, the average aerosol forcing is an order of magnitude greater, and the instantaneous forcing can be several-fold greater still, -30 to -50 watts per square meter, a substantial perturbation on the shortwave budget that must be accounted for in measurements and models. The product of this project will be parameterizations, of reduced and known uncertainty, for representing aerosol forcing in climate models in terms of mass loading of pertinent aerosol substances.

FAST MEASUREMENTS OF AEROSOL SIZE DISTRIBUTION, HYGROSCOPICITY, AND VOLATILITY FOR AIRCRAFT DEPLOYMENT

EE-484-EECA [KP1202010]

P.I.: Jian Wang

Brookhaven National Laboratory (BNL) proposes to develop two novel instruments for aircraft-based measurements of aerosol-size distribution, hygroscopicity, and chemical composition. The proposed developments support field studies using aircraft as a primary measurement platform. The first instrument, referred to as an Aerosol Mobility Size Spectrometer (AMSS), separates charged aerosol particles into different flow streams according to their sizes. The separated particles are grown into supermicron droplets in a supersaturated environment and are, subsequently, detected by an imaging system. The imaging system records mobility-dependent particle positions and their numbers, which are then used to derive particle-size distribution spectra. By eliminating the necessity to scan over a range of particle sizes, AMSS significantly improves measurement speed and counting statistics. The second proposed instrument, referred to as an Aerosol Hygroscopicity and Volatility Spectrometer (AHVS), first selects monodisperse dry aerosol through a differential mobility analyzer. The monodispersed aerosol is then directed to either a humidifier (hygroscopicity measurements) or a thermal denuder (volatility measurements). The size distributions of processed aerosols, which are measured by an AMSS downstream, are used to derive aerosol hygroscopicity and volatility. The hygroscopicity and volatility measurements will also be combined to derive size-resolved aerosol-chemical compositions and mixing states.

CHIEF SCIENTIST FOR THE ATMOSPHERIC SCIENCE PROGRAM

EE-533-EECA [KP1202010]

P.I.: Stephen E. Schwartz

In recognition of the importance of aerosol-radiative forcing of climate change, the Department of Energy (DOE) is focusing research efforts in the Atmospheric Science Program (ASP) to improve understanding and model-based representation of the processes controlling aerosol loading, distribution, and pertinent properties, relevant to the influence of aerosols on climate. This project consists of the activities of the Chief Scientist for the ASP. The Chief Scientist provides scientific leadership and vision to this program and enhances, facilitates, and promotes application of the research conducted in this program; provides leadership and guidance to program participants regarding the direction and course of the science conducted in the program; draws generalizations and conclusions from the work as reflected in the measurements and model calculations of the several investigators; represents this program in the broader national and international arena of climate change research; arranges and leads meetings of the ASP Science Team and others, and of smaller groups as required. The chief scientist is also responsible for maintaining the project data archive and the program website.

FIELD STUDIES ON THE LIFE CYCLE OF AEROSOLS AND THEIR DIRECT RADIATIVE IMPACTS

EE-554-EECA [KP1202010]

P.I.: Lawrence I. Kleinman

The Department of Energy (DOE) G-1 aircraft will be used as the primary measurement platform in a series of field campaigns directed at obtaining a process-level understanding of aerosol production in diverse chemical and meteorological environments. Broadly speaking, the goal is to understand the processes controlling ambient levels of aerosols and their properties to the extent needed to predict their direct effect on the radiation balance of the atmosphere. Properties that are important include size distribution, chemical composition, light scattering, light absorption, and hygroscopicity. A focus of the proposed field work will be on the time evolution of aerosol properties downwind of various source regions to gain an understanding of the important processes that control aerosol properties, and the effects that these source regions have on modifying the properties of background aerosol. Measurements will be used to elucidate the processes responsible for creating cloud condensation nuclei. The activities will include the planning and execution of field campaigns, followed by data analysis. Proposed venues include the Midwest United States (US) and Mexico City, Mexico. By providing information that links emissions with the concentration and optical properties of ambient aerosols, the direct-radiative impact of these aerosols can be predicted, which will allow a more accurate assessment of the effects of increasing greenhouse gasses on climate.

ACCESS WORKSHOP

EE-564-EECA [KP1202010]

P.I.: Leonard Newman

The Atmospheric Chemistry Colloquium for Emerging Senior Scientists (ACCESS) Colloquia are held in conjunction with Gordon Research Conferences (GRC) on Atmospheric Chemistry to bring together—in scientific discussion and interaction—recent PhDs in atmospheric chemistry and doctoral candidates soon to receive their degrees, together with representatives of the principal federal government agencies that fund atmospheric chemistry research. The Colloquia in conjunction with the GRC provide an opportunity to forge future professional relationships, and the entire atmospheric science community benefits by becoming more aware of innovations in atmospheric chemistry through these researchers’ efforts.

STUDIES OF CLOUD MICROPHYSICAL AND OPTICAL PROPERTIES

EE-570-EECA [KP1201030]

P.I.: Yangang Liu

This project focuses on the specification of the microphysical properties of clouds and on the relationship between cloud microphysics and cloud radiative properties. The overall objective is to improve the treatment of cloud microphysics of liquid-water clouds in global circulation models (GCMs). A primary focus of this work is the specification of the cloud-droplet-effective radius, a key variable used to calculate cloud-radiative properties in GCMs, in terms of the major environmental variables (e.g., cloud updraft velocity, turbulence and antropogenic aerosols). Another focus is the scale dependency of droplet-size distributions and key quantities (e.g., droplet concentrations, liquid water content, spectral dispersion, and effective radius) and the relationship between scale dependency and cloud variability. Both analysis of observational data (e.g., in situ and cloud radar) and theoretical studies will be carried out to achieve the objectives, with an emphasis on the former. Theoretical studies will focus on developing a physical understanding of the effects of updraft, turbulence and anthropogenic aerosols on the properties of the droplet-size distributions, and to scale issues. The theoretical work will be driven/evaluated by analysis and examination of observational data.

RETRIEVAL OF CLOUD PROPERTIES AND DIRECT TESTING OF CLOUD AND RADIATION PARAMETERIZATION USING ATMOSPHERIC RADIATION MEASUREMENT (ARM) OBSERVATIONS

EE-580-EECA [KP1201030]

P.I.: Mark A. Miller

One important impact of clouds on the climate system is the atmospheric heating rate profile. This profile quantifies how the clouds interact with incoming and outgoing radiation to heat or cool the atmospheric column. This heating and cooling subsequently feeds back upon the general circulation of the atmosphere. Therefore, any changes in the cloud structure associated with accumulation of greenhouse gases in the atmosphere may change the atmospheric heating rate profile and cause changes in the general circulation. The heating rate profile is modulated by the microphysical structure of the clouds and can be computed by retrieving this structure using Atmospheric Radiation Measurement (ARM) active remote sensing systems and using it as input to radiation codes, in particular, line-by-line radiation codes. One problem faced by the ARM community is that there is no metric for judging the accuracy of retrieval algorithms applied to remote sensor data, although these fields are required to compute the heating rate profile. To address these issues and to provide information about the heating rate profile to modelers, ARM has undertaken a broadband heating rate project. Because the heating rate must be continuous, an immediate need is for a microphysical retrieval scheme that operates continuously, and such a scheme has been developed here at Brookhaven National Laboratory (BNL). These microphysical fields are then used to compute the downward fluxes of visible and infrared radiation, which can then be compared to observations of same made at the ARM Cloud and Radiation Test-bed sites. This initial, continuous, microphysical retrieval is, in essence, a baseline, due to its simplicity. More sophisticated, condition-dependent microphysical retrievals can be used when appropriate, so the combination of the baseline product and these higher level retrieval schemes presents an opportunity to judge which microphysical schemes are the best representations of nature. The object of this work is to create a skill-score procedure to determine which condition-dependent microphysical schemes are the most effective and should be used to calculate the atmospheric heating rate profile.

ATMOSPHERIC RADIATION MEASUREMENT MOBILE FACILITY SCIENTIST

EE-586-EECA [KP1201030]

P.I.: Mark A. Miller

The original experiment design of the Atmospheric Radiation Measurement (ARM) User Facility included five permanent sites and an ARM Mobile Facility (AMF) to be deployed episodically for periods on the order of one year. The AMF management plan includes an AMF scientist whose duties include organizing scientific stakeholders, executing the science plan for each deployment, tailoring the sampling strategy of the AMF instruments to accommodate the scientific needs of the deployment, analyzing data, producing scientific products, interfacing with the ARM science team, interfacing with the ARM Climate Research Facility Board, and with the broader scientific community. The AMF Site Scientist’s role is split equally between science and operations. The AMF was constructed during the second half of FY 2004 and deployed initially in March 2005 at Pt. Reyes, California, in support of the Marine Stratus Radiation, Aerosol, and Drizzle (MASRAD) campaign. It has since been deployed in Niamey, Niger, Africa, in support of the RAdiative Flux Divergence using AMF, Global Earth Radiation Budget, and African Monsoon Multidisciplinary Analysis (AMMA) STations (RADAGAST). Analysis work is proceeding for MASRAD and beginning for RADAGAST. A summary of past activities and a schedule for AMF Scientist activities during FY 2006 is outlined in this proposal.

INTERFEROMETER (AERI) DATA: RADIATIVE PROPERTIES, THERMODYNAMIC PHASE AND SEARCH FOR THE INDIRECT AEROSOL EFFECT

EE-588-EECA [KP1201030]

P.I.: Mark A. Miller

In support of Atmospheric Radiation Measurement (ARM) Program objectives, the Principal Investigators (PIs) propose a program designed to investigate aspects of aerosol and cloud properties that are necessary to understand the Arctic surface radiative energy balance. This will be accomplished by three research thrusts:

1) Develop a cloud retrieval algorithm that provides the essential cloud properties needed to investigate cloud behavior in the Arctic. The retrieved properties will include cloud thermodynamic phases (ice, mixed phase, liquid water), their effective radii, and the partitioning of optical depth between the ice and liquid phases for the mixed phase cases. The spectral information contained in both Extended Range Atmospheric Emitted Radiance Interferometer (AERI) channels will enable these retrievals with constraints from other ARM measurements. The objective is to generate an algorithm that can be used by the ARM infrastructure to produce a Value-Added Product (VAP) of the retrieved quantities.

2) Use the high daily volume of satellite imagery available in the Arctic, along with European Center for Medium-range Weather Forecasting (ECMWF) simulations, to evaluate the significance of the single-point ARM cloud property retrievals in the context of atmospheric dynamics, including polar lows, advection of moisture, and quiescent atmospheric states when cloud formation is driven by local thermodynamics.

Both of these thrusts are necessary preliminaries to the scientific objective it is hoped to achieve in the third thrust:

3) Examine the aerosol direct (longwave and shortwave) radiative effect in the Arctic, and search for the indirect radiative effect using microphysical retrievals, a variety of aerosol information, and satellite data.

Brookhaven National Laboratory researchers will maintain a willingness to collaborate with other groups working on similar retrievals with a variety of methods, and also similar research tasks, through individual group interactions, and participation with the ARM Working Groups.

CLOUD-FIELD RADIATIVE EFFECTS IN THE TROPICAL WESTERN PACIFIC: ANALYSES AND GENERAL CIRCULATION MODEL PARAMETERIZATIONS

EE-596-EECA [KP1201030]

P.I.: Andrew Vogelmann

This proposed research will use Atmospheric Radiation Measurement (ARM) observations from the Tropical Western Pacific (TWP) sites, blended with correlative satellite and field data, to improve the understanding of aerosol, cloud, and radiation physical processes, and to improve their interpretation and representation in general circulation models (GCMs). This program builds on expertise and unique algorithms that the Principal Investigator (PI) has developed for analyzing ARM observations and related satellite data. These objectives are addressed through two research thrusts:

· Thrust 1: The Role of Aerosols on the TWP Radiative Energy Budget: The effects of the seasonal biomass- burning aerosols on the radiative balance in the region will be determined and compared to those from other ARM sites, as well as the potential effects of their absence in GCM simulations.

· Thrust 2: Continuous TWP Cloud Microphysical Retrievals: ARM algorithms currently used at the Southern Great Plains (SGP) will be modified to provide continuous retrievals of TWP cloud microphysical properties over the ARM sites, and their uncertainties characterized.

· Thrust 3: Develop a Lagrangian Cloud Tracking Algorithm: A Lagrangian cloud-clustering and identification algorithm will be extended to enable tracking the cloud clusters and their evolution within the vicinity of the ARM sites.

DEVELOPING NEW THEORY AND PARAMETERIZATIONS FOR CLOUDS AND PRECIPITATION IN CLIMATE MODELS

EE-601-EECA [KP1201030]

P.I.: Robert L. McGraw

The proposed research will develop and apply new parameterizations for drizzle formation based on kinetic potential (KP) theory while making extensive use of Atmospheric Radiation Measurements (ARM) for validation. Drizzle formation is identified in the KP theory as a statistical barrier-crossing phenomenon that transforms cloud droplets to much larger drizzle size at a rate dependent on turbulent diffusion, droplet-collection efficiency, and properties of the underlying cloud droplet-size distribution. Observational evidence, including the threshold behavior of drizzle formation and the well-known effect that aerosols have on drizzle suppression, support the new model, which in turn, provides new insights into these effects. The proposed research will service ARM objectives through its focus on issues related to precipitation efficiency. Its objectives include improved understanding and parameterization of the negative contributions to radiative forcing from precipitation, brought about the increase in cloud lifetime and the average cloud cover associated with a decrease in precipitation efficiency at higher cloud droplet-number concentrations. The proposed research will extend the KP drizzle theory in order to parameterize the later stages of precipitation, taking into account cloud-droplet depletion and the resulting slowing-down and quenching of precipitation. Parameterizations derived from the model will be tested, validated through comparisons with ARM data, and implemented in cloud- resolving models (CRMs). The results gained from the proposed studies should lead to improved parameterizations for precipitation and the second aerosol indirect effect suitable for use in weather forecast and climate models.

MEASUREMENT OF AEROSOL ABSORPTION USING PHOTOTHERMAL INTERFEROMETRY

EE-603-EECA [KP1202010]

P.I.: Arthur J. Sedlacek III

One of the central goals in the community is to better quantify the individual roles that aerosol absorption and scattering have on radiative balance. However, despite focused work on this issue, significant discrepancies on aerosol absorption still exist between measurements inferred from remote sensing and those obtained by in situ techniques. This is due, in large part, to the simple fact that the scattering channel dominates aerosol extinction and, thereby, makes measurement of the absorption difficult.

An alternative method to measuring aerosol absorption is proposed herein: Measurement of the thermal dissipation of the spectrally-absorbed energy through interferometry. The use of this coherent optical detection technique is particularly well suited to measuring the refractive-index change that accompanies this energy-transfer process. The primary goal of this project is to conduct in situ measurements of aerosol absorption during Atmospheric Sciences Program (ASP) field campaigns. To meet this goal, construction of a prototype system will be undertaken to gain experience with the technique, characterize the sensitivity, and develop calibration. In addition to these activities, comparisons will be made with the filter-based technique [e.g., Particle-Soot Absorption Photometer (PSAP)] and with other in situ instruments [Cavity Ringdown (CRD) and photoacoustic spectroscopy (PAS)] both in the laboratory and in the field. It is envisioned that this instrument will find utility in a laboratory setting for measuring fundamental optical properties of prepared (well-characterized) aerosols, as a potential calibration tool for the widely-used PSAP method and as a fieldable instrument in ASP field studies.

NEW PARTICLE FORMATION: MECHANISMS AND INFLUENCE ON ATMOSPHERIC AEROSOL PROPERTIES

EE-605-EECA [KP1202010]

P.I.: Robert L. McGraw

The proposed research focuses on the nucleation mechanisms governing new particle formation in the atmosphere. Its objectives are to provide an interpretation for field measurements of new particle formation and to assess the importance of nucleation-mode particles as a contributor to both cloud- and climate-influencing properties of the atmospheric aerosol. While too small initially to have direct atmospheric significance, nucleation-mode particles may grow in size and, ultimately, become part of the larger particle population. The proposed research will examine the pathways and growth rates through which new particles grow and contribute as cloud condensation nuclei (CCN) and to the accumulation-mode particle population. The proposed research will examine the effect of atmospheric composition, especially atmospheric trace species (organic as well as inorganic precursors) and develop correlations between field measurements of atmospheric composition and observations of new particle formation. The so-called "nucleation theorem" will be used to correlate trace species measurements with nuclei size and chemical composition and rates of new particle formation. The parameterizations for coupled nucleation and growth processes developed under the proposed research will be in a form suitable for incorporation into regional-to-global scale atmospheric models currently under development in other programs.

PARAMETERIZATIONS OF CLOUD MICROPHYSICS AND INDIRECT AEROSOL EFFECTS

EE-612-EECA [KP1201030]

P.I.: Mark A. Miller

The goal of this project is to evaluate and upscale new cloud-microphysical parameterizations using Atmospheric Radiation Measurement (ARM) observations, satellite data, and process models, and introduce the new parameterizations into Cloud System Resolving Models (CSRMs) and Global Climate Models (GCMs). Existing parameterizations of cloud microphysics and aerosols fail to account for the multi-scale interaction between cloud dynamics, radiation, turbulence and aerosol loading due to lack of understanding of these physical processes and their coupling mechanisms. The specific scientific objective is to understand the role of dynamical mechanisms on indirect aerosol effects by relating updraft velocity and turbulence structure to droplet microphysics for a variety of aerosol loading conditions.

A major focus is the analysis of data collected by the ARM Mobile Facility (AMF) during the MArine Stratus Radiation Aerosol and Drizzle (MASRAD) Experiment. Multiple-sensor remote-sensing techniques, aircraft in situ observations, and satellite analysis are being used to investigate the cloud microphysical, radiative, and turbulent structure for the observed aerosol conditions and large-scale dynamics. New parameterizations that Brookhaven National Laboratory (BNL) is developing will be introduced into a CSRM and several GCM’s and improvements quantified through statistical comparisons with the detailed ARM data sets and interactions with the Climate Change and Prediction Program ARM Parameterization Testbed (CAPT).

AN INVESTIGATION OF THE MICROPHYSICAL, RADIATIVE, AND DYNAMICAL PROPERTIES OF MIXED-PHASE CLOUDS

EE-616-EECA [KP1201030]

P.I.: Pavlos Kollias

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program has established and continuously operates field research sites at several climatically-significant locations to study the effects of clouds on the Earth’s radiation budget. Recently, the ARM program has recognized the need for new observations to improve our understanding of mixed-phase cloud properties and processes. Uncertainties regarding the extent to which ice and liquid water coexist in mixed-phase clouds and the sensitivity of cloud radiative properties to phase make the parameterization of mixed-phase clouds in climate models a challenge. Brookhaven National Laboratory (BNL) propose to develop and implement an operational retrieval method for deriving the microphysical, radiative, and dynamical properties of mixed-phase clouds at the ARM Southern Great Plains (SGP) and North Slope of Alaska (NSA) cites. The zeroth-order objective of BNL’s approach will be the identification of mixed-phase clouds using existing ARM data streams and the development of a mixed-phase cloud climatology. This will be accomplished using a diverse collection of ARM measurements, including: radar reflectivity, mean Doppler velocity, and Doppler spectrum width, lidar backscatter and depolarization ratio, microwave radiometer-derived liquid water path, and temperature soundings. The main thrust of BNL’s proposed work will be to develop mixed-phase cloud microphysical retrieval techniques using current and future ARM measurements and to assess the uncertainty of the retrieval methods using in situ observations and radiative closure studies. The retrieval algorithms include a dual radar wavelength technique and a radar Doppler spectra technique. Furthermore, BNL proposes to design and implement an operational framework for these mixed-phase cloud retrievals at the ARM SGP and NSA sites. Selected mixed-phase cloud cases will be further analyzed (using process studies) to investigate the microphysical and dynamical factors responsible for the partitioning of phases, ice crystal growth, and vertical structure in mixed-phase clouds. The motivation for this study is the need for improved mixed-phase cloud parameterizations in numerical models.

DEVELOPMENT AND EVALUATION OF BOUNDARY LAYER CLOUDINESS PARAMETERIZATIONS USING ATMOSPHERIC RADIATION MEASUREMENT OBSERVATIONS

EE-617-EECA [KP1201030]

P.I.: Pavlos Kollias

This continuing project is designed to address key issues regarding the treatment of boundary-layer clouds in climate models. A major focus of this study will be to provide a comprehensive description of the large-eddy (LE) and turbulence structures in boundary-layer clouds. This will be accomplished by applying techniques developed by the principal investigators (PI) to high-temporal resolution Doppler data obtained from the Atmospheric Radiation Measurement (ARM) millimeter cloud radars. Such a product will improve the cloud detection (e.g. broken-cloud fields), the mode merging, (e.g. active remote-sensing cloud layer (ARSCL)) value added product (VAP), reduce the variance of the Doppler moment estimates, and improve the retrieval of cloud optical/radiative properties at less than 20 sec resolution. This would allow for the possibility of combining the liquid-water estimates with the vertical velocities to obtain liquid-water fluxes and developing realistic cloud characterizations for 3-dimensional (D) radiation calculations. Furthermore, these observations will be used to test cumulus mass-flux schemes applied to boundary-layer clouds and to provide high-resolution data sets for direct comparison of vertical velocity techniques with LE Simulations (LES) and cloud-resolving models, important test beds for parameterization development and evaluation. The principal focus will be on stratocumulus clouds and fair-weather cumuli over the ARM Southern Great Plains (SGP) site and fair-weather cumuli observed over the Nauru Island site.

CHIEF SCIENTIST FOR THE DOE ATMOSPHERIC RADIATION MEASUREMENT (ARM) PROGRAM

EE-618-EECA [KP1201030]

P.I.: Warren J. Wiscombe

This proposal outlines the duties and responsibilities of the Atmospheric Radiation Measurement (ARM) Program Chief Scientist. The duties of the Chief Scientist include, first and foremost, guiding the scientific strategy of the ARM program; also, developing performance measures to judge progress; providing Department of Energy (DOE) managers with regular one-page highlights about exciting ARM findings; interfacing with the three major climate modeling groups in the U.S. who use or could use ARM data and facilities; organizing the scientific content of the ARM Science Team Meeting (STM); outreaching to scientific groups and federal agencies to offer the services of the ARM user facility; updating the ARM Science Plan every three years; and serving on internal and external science committees including the ARM Climate Research Facility Board. The Chief Scientist is also responsible for coordinating and interfacing with the various ARM Science Team Working Groups, and attending their meetings. The ARM Chief Scientist’s Office is comprised of the Chief Scientist, four Associate Chief Scientists who interface with specific projects or Working Groups within the ARM Program, and an Administrator for the Chief Scientist Office. The ARM Chief Scientist also interfaces with DOE representatives in the Office of Biological and Environmental Research (OBER) by providing input, solicited and unsolicited, that is relevant to the ARM Program. In addition to managerial duties, the ARM Chief Scientist and Associate Chief Scientists actively conduct and publish ARM-related research. An avenue for some of this research will be a post-doctoral student who conducts ARM-related research in cloud tomography, funded entirely under this grant. A critical goal of the ARM Program is to improve the representation of clouds and radiation in Global Climate Models (GCMs). Toward that end, the ARM Chief Scientist is actively engaged in orchestrating a timely and efficient interface between ARM and the GCM community.

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