Research Summaries

To illustrate the nature and scope of the research conducted by ASP personnel, short descriptions of individual research projects are included in this section. The ASP seeks to maintain involvement in the broad range of research at NCAR. Almost all of these research projects have been conducted in collaboration with scientists in other divisions and programs, and in many cases more thematic descriptions of the research programs are available in the reports of those divisions and programs. Where appropriate, these descriptions are linked to those other sections of the Annual Scientific Report to indicate how these research projects contribute to the broader research program at NCAR.

Postdoctoral fellows research accomplishments

Ian Faloona studied fluxes in the atmospheric boundary layer using new instrumentation that he developed or improved during the past two years. In collaboration with scientists and engineers at the research aviation facility, he built a new fast ozone chemiluminescence instrument and assisted in the development and deployment of new instrumentation to measure CO and CO2. The primary focus of his research was measurement of the entrainment rate at the top of the stratocumulus-topped marine boundary layer. Working with Don Lenschow in MMM, he has been looking at eddy correlation measurements of ozone and dimethyl sulfide (DMS) from the DYCOMS-II (the Dynamics and Chemistry of Marine Stratocumulus) experiment. These measurements support estimates of entrainment rates and spatial scales of this type of boundary layer with heretofore-unrealized accuracy. Additionally, he has been indirectly looking at aqueous chemistry that may be occurring in the cloud and the sea surface to alter the ozone and DMS budgets over the subtropical oceans.

Andrew Gettelman conducted a survey of developing country scientists to understand the barriers to information exchange in the fields of meteorology and climatology. The survey consisted of a written and electronic survey, as well as field visits to a number of different countries throughout the year while on leave from ASP. The survey was supported by NCAR (ASP and ESIG), the World Meteorological Organization and the Intergovernmental Panel on Climate Change. The results of the survey are expected in late 2002 or early 2003. More information on the project can be found at http://www.asp.ucar.edu/infoex.

Alessandra Giannini compared results from climate models to observations in studies that focus on rainfall as a means of understanding the dynamics and predictability of climate in the tropical Atlantic. Her research examined two geographical regions, both characterized by a semi-arid climate: the Northeastern corner of Brazil and the Sahel, the transitional region in northern Africa between the Saharan desert and the tropical rainforest. With R. Saravanan (NCAR/CGD) and Ping Chang (Texas A&M, Dept of Oceanography), she evaluated the predictability of rainfall variability in Northeast Brazil during El Ninõ-Southern Oscillation (ENSO) events, finding that rainfall here depends on the state of the climate of the tropical Atlantic basin at the time that the Pacific ENSO event develops. Alessandra also analyzed an ensemble of simulations run with the NASA Seasonal to Interannual Prediction Project (NSIPP1) atmospheric general circulation model, a model developed at NASA/GSFC by the group led by Max Suarez and Michele Rienecker. She found that this model is capable of reproducing the observed trend in Sahel rainfall in recent years even when the only link to observed climate conditions is through the imposed ocean boundary conditions. This indicates that the observed trend was forced by changes in sea surface temperature and not, as previously argued, by a change in the local land cover.

David Gochis studied hydrometeorological interactions between the surface and the atmosphere with a focus on warm season convection and monsoon environments. He analyzed diurnal patterns in convective precipitation over the Sierra Madre Occidental mountains of northwest Mexico in order to prepare for a study that will use the Weather Research and Forecasting (WRF) model to determine critical links between topographic features and convective development.

Joshua Hacker, in collaboration with Chris Snyder (MMM) and Jeffrey Anderson (MMM/CGD), demonstrated that assimilating surface temperature into a model of the planetary boundary layer can improve the realism of the simulation. They used an ensemble Kalman filter (EnKF) for the assimilation, in part because an ensemble of mesoscale forecasts can develop anisotropic background error covariances. For the PBL model they chose a PBL parameterization scheme commonly employed in mesoscale forecast models. The resulting state of the PBL was more accurate than a state estimated with an idealized data assimilation system. An error term, representing both model error and forecast error that may be intrinsic to the real atmosphere, was also introduced with positive results. (Fig. 1: Click here for a movie that shows results from the simulation.). Surface-layer observations are a rich, accurate, and often dense data source, but they are generally underutilized in current operational data assimilation systems because complex interactions between the surface and the atmosphere aloft are difficult to handle. Using these observations to improve the initial PBL state in a mesoscale NWP model could lead to better short-range forecasts of convective outbreaks, slope flows, and frontal propagation.

Hacker also collaborated with Steven Thomas (SCD), Piotr Smolarkiewicz (MMM), and Roland Stull (University of British Columbia) to develop a horizontal spectral preconditioner for nonhydrostatic atmospheric models that is an alternative to a more-standard and simpler line-Jacobi relaxation scheme. Elliptic problems in semi-implicit nonhydrostatic atmospheric models are notoriously difficult. Typically they are poorly conditioned, nonseparable, contain cross derivative terms, and often are nonsymmetric. This development led to a class of effective Krylov methods --- a conjugate residual (GCR) algorithm preconditioned with a 3D direct solver (using standard tridiagonal inversion in the vertical). However, the efficacy of the spectral preconditioner requires neglecting the cross derivative terms and homogenization (e.g., averaging) metric coefficients over the computational domain. Because such a compromise causes a substantial departure of the preconditioner from the original elliptic operator, it is not obvious a priori whether it leads to a competitive solver. They evaluated the robustness of the proposed approach over a broad range of representative meteorological applications (Fig 1: bubble.mov), and documented its superior performance in the context of a three-time-level semi-implicit semi-Lagrangian all-scale weather-prediction/research model.

Current grid-point NWP models have filtering properties that slow error growth as measured quadratically. These properties arise from both finite-difference methods and explicit diffusion designed to control spurious features. The effects must be taken into account for quantitative prediction and predictability studies. A collaborative effort between Joshua Hacker (ASP) and David Baumhefner (CGD) compared error growth characteristics of current spectral (CCM3) and a future grid-point (WRF) model, and will calibrate the WRF so that quantitative results can be trusted. Because CCM3 has been extensively tuned to reproduce observed atmospheric statistics and spectra, the researchers are using it as a benchmark for calibration. With both models, they generated 6-day ensemble forecasts for five cases from the 2001-2002 cool season in the northern hemisphere. The experiments identified strong sensitivity of ensemble spread, and the associated error growth, to numerical diffusion. Spectral analysis is one approach that shows diffusion-dependent error growth relative to a forecast (Fig. 1: wrf_S.mov). The results demonstrated the need to characterize error growth in the WRF model and more generally in all grid-point models. They contributed to the WRF model development by finding classes of problems for which its statistical behavior is unlike the atmosphere.

Paul Harasti worked with Wen-Chau Lee (NCAR/ATD) and Michael Bell (NCAR/ATD) to apply Sir Horace Lamb's solution for a small amplitude disturbance superimposed upon a Rankine-combined vortex to the Ground-Based Velocity Track Display (GBVTD) method. Harasti et al. initially solved the equations for a wave number 2 elliptical disturbance but later generalized the solution for any combination of wave number "n" disturbances superimposed on non-Rankine type vortices as well. The resulting new GBVTD formulation was successfully tested on the elliptical Typhoon Herb (1996). Harasti also worked with John Tuttle (NCAR/MMM) to develop and test an operational version of the Tracking Radar Echoes by Correlation (TREC) method for real-time use at the National Hurricane Center in Miami, Florida. The operational TREC algorithm provided key insights into the intensity at landfall of Tropical Storm Barry (2001), which was marginally under hurricane status. In addition, Harasti further improved upon his Hurricane-customized Extension of the VAD method (HEVAD), first conceptualized by Harasti at the University of Toronto. Harasti successfully applied HEVAD to a case study of Hurricane Bret (1999), finding a strong anti-cyclonic shear in the background environmental wind. Harasti also showed how the HEVAD and GBVTD methods could be suitably combined to provide a more complete and accurate estimate of hurricane and environmental winds in the lower troposphere.

Todd Lane's research combined fundamental and applied research into turbulence generation by deep convective clouds and the jet stream. In collaboration with Robert Sharman (RAP) and Terry Clark (MMM), Lane completed a case study of turbulence that was encountered by a commercial aircraft, near a convective cloud in North Dakota. They demonstrated that the turbulence was caused by a combination of breaking gravity waves and highly nonlinear interactions at the cloud interface. In collaboration with Robert Sharman (RAP), James Doyle (Naval Research Laboratory), and Mel Shapiro (NOAA), Lane also modeled turbulence in the jet stream that was observed during two field experiments (NORPEX and SCATCAT01). The modeling results suggest that, in both cases, turbulence generation occurred when frontally forced waves interacted with the strong wind shear in the jet. These studies contribute to improved understanding of the generation of turbulence that is encountered by aircraft, and so should lead to improved ability to diagnose and forecast such turbulence.

Kimberly Mace's research is aimed at understanding the magnitude and sources of water-soluble organic nitrogen (N) in the global atmosphere. At least some proportion of the water-soluble component of rainwater and atmospheric aerosols may be bio-available and may impact the growth of ecosystems. However, little information exists regarding the flux of organic N from known and/or potential sources; or how the release of water-soluble organic N from sources may increase in the future due to anthropogenic influence on the global N cycle.

Mark Miesch has investigated turbulence and instabilities in the solar tachocline with 3D, nonlinear simulations. The tachocline is a stably-stratified shear layer located near the base of the convective envelope in the Sun. Although narrow, it is thought to play an important role in the global angular momentum balance of the solar interior and in the operation of the solar dynamo. Preliminary work demonstrated the ability of the model to produce realistic circulation patterns for the Sun. His recent work focused on the redistribution of angular momentum at the tachocline by randomly forced turbulence and shear instabilities. Collaborators in this work include Peter Gilman and Mausumi Dikpati (HAO/NCAR). Work has also continued on high-resolution numerical modeling of turbulent convection in the solar envelope with collaborators at the University of Colorado (J. Toomre, S. Brun) and Lockheed (M. DeRosa). Recent developments in these modeling efforts include the extension of the computational domain closer to the photosphere, the addition of magnetic fields, and a closer investigation of the effects of convective penetration.

Katharine Moore participated in the multi-investigator 2002 Atlanta Aerosol Nucleation and Real-Time Characterization Experiment, where the thermal desorption chemical ionization mass spectrometer, recently developed by the ACD Photochemical Oxidation/Products Group led by Fred Eisele, was used to obtain the first direct measurements of the chemical composition of freshly-nucleated aerosol in the sub-10 nm range. Working closely with Jim Smith, she also performed laboratory work to continue the development and validation of the measurement technique, which makes it possible to characterize the chemical composition of nanometer-sized particles. For further details, see http://acd.ucar.edu/~jimsmith/POP/

Rebecca Morss continued work with Roger A. Pielke, Jr. (Univ. of Colorado) on developing a framework for understanding and investigating the connections among meteorological observations, weather forecasts, and society. She also collaborated with David Battisti (Univ. of Washington) to study observing networks for ENSO prediction using a simple, linear, stochastically forced coupled atmosphere-ocean model.

Matthias Rempel modified the MHD code of Mark Rast (HAO) to allow for separation of the thermal conductivity into a turbulent and radiative component. This separation enables adjustment of the convective properties apart from the radiative ones in the lower half of the convection zone. He then employed a thermal relaxation scheme to accelerate the approach to equilibrium in the deep radiative layers. These modifications allowed him to apply the model to studies of the overshoot region at the base of the solar convection zone, where crucial storage of strong toroidal magnetic field is thought to play an important role in the solar dynamo. A 2D model with these modifications was able to reproduce many characteristics of previous overshoot models through different assumptions regarding the energy flux and Prandtl number. The model also shows how sensitively the overshoot depends on the structure of convection, which has to be considered when applying numerical results to solar overshoot. The accompanying figure shows a simulation of single downflows driven by cooling from the top boundary and entering a subadiabatic layer (below z = 2). Shown are the temperature perturbations with respect to the initial stratification. The length scale is made dimensionless with the pressure scale height at z = 2. In the upper part (z < 2) the Prandtl number is 1 in both cases, whereas in the lower part (z > 2) the Prandtl number is 0.25 for the left and 4 for the right case. Even though the Prandtl influences significantly the internal structure of the plume, it has only little influence on the penetration depth.

In a parallel study Rempel (collaborating with Mark Rast, HAO) investigated properties of single downflows driven by cooling at the top boundary were investigated (see Fig.1). In contrast to the full convection simulations these studies allow a much higher resolution of a single downflow. It was shown that the Prandtl number has nearly no influence on the penetration depth of a single downflow, whereas the full convection simulations show a significant increase of the overshoot depth with decreasing Prandtl number. Thus the dependence of the overshoot depths on the Prandtl number is caused by the different thermal adjustment of the mean stratification and not by a change of the deceleration of a single downflow. With the help of a semi-analytical convection model based on the assumption that the convection is driven by dominant downflows, fundamental results of the numerical simulations could be verified: the structure of the overshoot region is mainly determined by a) the Mach number of the downflows at the base of the convection zone and b) the efficiency of the mixing between downflow material and the surrounding plasma in the overshoot region.

Tian-You Yu collaborated with others in NCAR/ATD and NOAA/ETL to develop a new high-resolution wind profiling technique. By analyzing signals from multiple receivers and multiple frequencies simultaneously, variation of three-dimensional wind filed within a conventional range gate can be obtained. In other words, existing vertical wind shear within the radar volume may be detected by this technique. This high-resolution technique was tested using simulations and then implemented on the multiple antenna profiler antenna (MAPR) of NCAR for use during the IHOP observational program of summer 2002.

Qinghong (Alise) Zhang collaborated with Bill Kuo (MMM) to investigate the interaction between the concentric eyewalls observed in typhoon Winnie of 1997. With 3-km resolution in MM5, she found that the inner eyewall is a result of PV vortex Rossby wave propagation inward from the outer eyewall.

GTP members research accomplishments

Progress toward a new code for the numerical simulation of turbulent flows (Annick Pouquet and Duane Rosenberg)

GTP is currently developing an object-oriented spectral-element-based numerical modeling code --"GASpAR"-- for the numerical simulation of turbulent flows. The code features adaptive mesh refinement and is designed to operate on parallel systems with distributed memory architectures or on serial processors, although current plans call for the code to run optimally on shared/distributed hybrid systems.

While the solution to the incompressible Navier-Stokes equations is the intended goal, in reality GASpAR consists of a collection of operators and supporting objects for solving a variety of equations in multi-dimensions. The two-dimensional version of these operators is developed fully, including a choice of methods for solving the Stokes problem which forms the core of all time splittings of the Navier-Stokes equations. Both regular rectangular and deformed quadrilateral elements are supported, with support also planned for quadrilaterals with curved sides. The time stepping scheme is selectable, with Adams-Bashforth/BDF and Runge-Kutta splitting being offered presently.

The GASpAR framework allows the flow solution to refine or coarsen the grid adaptively to model transient or moving features in the flow with spectral accuracy. All operators and other structures have been developed with this design characteristic. Current efforts center on developing the structures required to handle this grid adaptivity from an upper-level management point of view and to communicate the grid changes to the processors that manage the affected elements.

Recent additions to the code include an HDF5-based I/O package (which will provide a platform-independent method for storing the large datasets anticipated from three-dimensional simulations) and a lower-overhead I/O alternative that uses MPI-IO to handle collective writing to files. A suite of utilities has also been developed for handling the datasets. One of these is a dataset profiler for obtaining critical information on the output data file. Another utility reassembles datasets consisting of any collection of elements to a regularly-shaped global domain, using the same high-order interpolation actually used in the numerical model.

The GASpAR code is currently being used in a study of a simple two-dimensional avalanche model (Hwa and Karder 1989), with forcing as expected in solar flares. The study with help determine if such models can predict aspects of the observed energy spectrum of these flares.

Nonlinearities in Climate Systems (Grant Branstator, CGD):

Some issues in climate dynamics revolve around whether, on interannual timescales, the climate system can be well approximated by linear dynamics or whether it is fundamentally nonlinear. To date most work aimed at making this distinction has considered probability density functions of the state vector, nonGaussian distributions being an indicator of nonlinearity. Working with J. Berner (University of Bonn and ASP), Branstator has been investigating the use of trajectories through phase space as an alternative approach. Their results indicate that distinct signatures of nonlinearity can be seen in the distribution of mean phase space tendencies for states from an extended integration of CCM0. Furthermore, using these mean tendencies as drift vectors in stochastic models, they have produced results that indicate that nonGaussian features in the GCM's PDFs can be attributed to nonlinearities in the mean tendencies. Additional work, in conjunction with F. Selten (KNMI), has concerned identifying which circulation features are primarily responsible for the nonlinearities. They have found that much of the GCM low-frequency behavior consists of regularly propagating features whose signatures mask the nonlinearities in the system. This helps explain why the nonlinearities have not been noticed in earlier studies.

Small-scale Turbulent Mixing in Clouds: (Wojciech Grabowski, MMM):

In collaboration with Miroslaw Andrejczuk and Szymon Malinowski (Warsaw University, Poland), Wojciech Grabowski and Piotr Smolarkiewicz (MMM), Grabowski completed a modeling study of decaying moist turbulence --- important, beyond fundamental understanding, for applications such as radiative transfer through clouds, initiation of precipitation in warm (i.e., ice-free) clouds, and parameterization of small-scale and microscale processes in models resolving larger scales. In the moist case, kinetic energy of small-scale motions originates not only from the classical downscale energy cascade, but it can be also generated/enhanced internally by the phase change processes and droplet sedimentation. They performed a series of moist simulations and contrasted them with corresponding dry reference runs. The results suggest that, as far as the evolution of turbulent kinetic energy and enstrophy is concerned, significant impact of moist processes is only possible at relatively low levels of the large-scale input of the kinetic energy. Then, phase change processes and droplet sedimentation invigorate substantially dry turbulent mixing. However, significant anisotropy --- consistent with that observed in laboratory experiments on mixing between cloudy and cloud-free air --- prevails even at high large-scale input of the kinetic energy.

Effects of Turbulence on the Collision Rate of Cloud Droplets (Wojciech Grabowski, MMM):

Prof. Lian-Ping Wang (University of Delaware), in collaboration with Wojciech Grabowski (MMM), studied the effects of turbulence on the collision of cloud droplets when droplet inertia, gravity, and turbulence microstructure are all considered. This is an important problem because the impact of cloud turbulence on microphysical processes (warm rain initiation in particular) remains ambiguous. Direct numerical simulations were used to generate the turbulent flow. The relative droplet inertia and settling velocity were specified according to the conditions typical for convective clouds. Numerical results show that droplet inertia and fluid turbulence can increase the collision kernel, relative to the gravity-only case, by as much as 70% for droplets of 10 to 50 micrometers in size, as a result of relative velocity fluctuations and preferential concentration of the droplets. For larger droplet sizes, the preferential concentration is a significant contributor. The relative velocity fluctuations play an important role for droplets of similar sizes, i.e., when gravity-only case results in no collisions. A leading order analysis was found to predict well the droplet-droplet relative velocity statistics.

2D Modeling of Atmospheric Convection in the PBL (Chin-Hoh Moeng, MMM):

Two-dimensional (2D) numerical models have documented successes in producing overall statistical properties of tropical deep convection and PBL shallow convection despite their fundamental limitations. With the increasing use of 2D modeling, it is important to understand what properties can be represented by a 2D model and how this is accomplished. Chin-Hoh Moeng (MMM), Jim McWilliams (UCLA/NCAR), Rich Rotunno (MMM), Peter Sullivan (MMM), and Jeff Weil (CIRES/CU) have investigated the 2D modeling technique using convective PBLs (with and without shear) as examples and large-eddy simulation (LES) as a database. A brief summary of the study can be found at this website: http://www.mmm.ucar.edu/caspp/caspp_boundary.html

Subfilter-Scale Motions in LES (Peter Sullivan, MMM):

Improved subfilter (or subgrid) scale (SFS) models for Large-Eddy Simulation (LES) are needed in order to develop reliable computational tools for simulating complex turbulent geophysical flows containing, for example, laminar-to-turbulent transition or strong stable stratification, or occurring near solid boundaries. GTP affiliated scientists Thomas Horst (ATD), Don Lenschow, Chin-Hoh Moeng, Peter Sullivan (MMM) and Jeff Weil (CIRES, MMM visitor) along with Jan Kleissl, Charles Meneveau, and Marc Parlange (Johns Hopkins University) are using observations of surface-layer turbulence from the Horizontal Array Turbulence Study (HATS) field campaign (see http://www.atd.ucar.edu/sssf/projects/hats/ for a description of the field campaign) to study the dynamics of subfilter scale variables at high Reynolds number with the long-term goal of improving SFS parameterization in LES models. They find that the SFS variances are anisotropic and noninertial, exhibiting a strong dependence on the stratification, large-scale shear, and proximity to the surface. Further highlights from this work can be found at http://www.mmm.ucar.edu/science/asr.html.

ASP Senior Research Associates research accomplishments

Jeffrey Anderson (MMM/CGD/ASP) investigated both basic and applied aspects of data assimilation. A prototype of the Data Assimilation Research Testbed software environment was completed including a variety of ensemble filter algorithms and both simple models and an atmospheric general circulation model. Anderson collaborated with scientists at the National Centers for Environmental Prediction to implement an ensemble filter data assimilation system in the operational global prediction model. Tests are ongoing to evaluate the performance of this system and to compare it to the operational data assimilation system. Collaboration with scientists in MMM also contributed to the implementation of ensemble filter assimilation systems in the WRF mesoscale model and in a cloud-scale model. These systems are now being used to evaluate the possibility of assimilation of doppler radar reflectivity observations. Anderson is continuing basic research aimed at better understanding the capabilities of small ensemble filters in large numerical models with many observations. Development of a theoretical motivation for heuristic aspects of ensemble filters has led to a partial theory for why filters can work with very small ensembles.

Hans Friedli (with colleagues from NCAR, U. Washington, Meteorological Services of Canada, Canadian Forest Service) has advanced the understanding of the cycling of mercury during biomass burning, progressing from laboratory to airborne measurements on wildland fuels and expansion to agricultural waste fuels The data indicate that all mercury contained in fuel is released as mostly elemental gaseous mercury with some fuel-dependent portion present in particulate form. The mercury release from fires in temperate US forests is relatively small (2-4 Mg/y), about 22 Mg/y for boreal forests and about 500 Mg/y for all biomass burning. These estimates reflect the carbon release from biomass burning and landscape-specific emission factors. For reference, the total mercury released to the atmosphere is about 6000 Mg/g.

Hans Friedli and Larry Radke measured elemental gaseous mercury from sea level to the tropopause as part of the ACE-Asia and ICTC2K2 experiments and detected its transport from the western to the eastern pacific. The ACE-Asia data are extremely complex representing dust storms, anthropogenic, volcanic and possibly biomass burning signatures contained in multiple layers. The mercury profiles measured over the eastern pacific challenge the currently accepted lifetime for elemental mercury of one year; they indicate that the lifetime may be closer to 100 days. They also identified a large new sink for mercury in the stratosphere as revealed by a stratospheric intrusion depleted of elemental gaseous mercury. An anthropogenic plume encountered off the California coast had back trajectories out of China and Mongolia passing over Korea and Japan.

Hans Friedli, with coworkers from ACD, CU and as part of the Wildland Fire R&D collaboratory, initiated laboratory experiments to determine the type and quantity of compounds emitted from live vegetation, simulating the conditions of an approaching wildfire. An understanding of the evolution of flammable volatiles is important because they are expected to modify flammability, fire dynamics, influence combustion chemistry and physics and, if not combusted, contribute directly and indirectly to the air pollution associated with wildfires. Roasting green or dry vegetation at increasing temperature to 300°C released methanol, acetaldehyde and acetone, readily measured by proton transfer reaction mass spectroscopy. The source of these compounds is not known at this time- they may be stored in the plant, be decomposition products of wood components or be partial oxidation products.

John Latham has published two papers on and has been extending his research into a novel idea for the amelioration of global warming by the advertent and controlled enhancement of the albedo and longevity of low-Level maritime clouds. His provisional calculations and some limited computer modelling support the quantitative validity of the proposed technique, which involves increasing the droplet concentration in such clouds, with a corresponding increase in both albedo and lifetime, and thus cooling. The idea involves the dissemination at the ocean surface of small seawater droplets in sufficient quantities to act as the dominant CCN on which cloud droplets form. Satellite control of the dissemination is envisaged. Collaborators include Dr Keith Bower, Prof. Tom Choularton & Dr Alan Gadian (UMIST, Manchester, UK), Dr Alan Blyth & Prof. Mike Smith (University of Leeds, UK), Prof. Stephen Salter, (University of Edinburgh, UK) and Dr Tom Wigley (CGD, NCAR). If this technique were to prove workable on the scales required, it could be of great societal importance.

John Latham and collaborators are examining the extent to which it is possible to determine thundercloud ice characteristics from satellite observations of lightning, which are now routinely made on a global scale, using NASA/MSFC devices. A specific goal is to ascertain whether measurements of lightning frequency f can yield estimates of precipitating and non-precipitating ice fluxes. Our computations predict that f is roughly proportional to the product of the downward flux fg of graupel through the body of the thundercloud and the upward flux fi of ice crystals into its anvil. This raises the possibility of determining, on a global basis, values of fg and/or fi from the lightning measurements. Such information could have considerable climatological and nowcasting importance. Collaborators include Dr Hugh Christian & Ms Wiebke Deierling (NASA/MSFC), Dr Alan Gadian (UMIST, UK), Dr Alan Blyth, (University of Leeds, UK), Dr Rumjana Mitzeva (University of Sofia, Bulgaria) and Dr Jim Dye (MMM, NCAR).

The main thrust of Jerry Mahlman's NCAR research and research-related activities in FY-2002 was focussed on "Climate Services and Outreach". In part, this involved giving "global warming" talks and seminars to highly diverse audiences. It also involved participating in a number of education-oriented communications for media preparations, as well as formal and informal advice on climate-oriented aspects of research programs in Canada (Canadian Climate Research Programme), and in the U.S.(University of Washington, NCAR, CIRES, EPA, and GFDL).

Dr. Mahlman has developed a stronger working relationship with NCAR's Environmental and Societal Impacts Group in FY 2002, concerning its research priorities, its staff empowerment, and its capacity building for a broader and more-targeted climate-change impacts research/outreach program at NCAR. Also, this has involved new efforts to nurture a broader U.S. base for more-effective climate-change impacts research and outreach programs.

Near the end of FY-2002, Mahlman became involved with the National Research Council on two very different climate-related projects under the National Academy of Sciences. First, he is Chairing an EPA-sponsored NRC Workshop on "Assessment of the Current State of Knowledge of Climate Sensitivity". This is to provide updated information on this key topic for EPA and for the U.S. policy process. Second, he is serving as part of a five-member Advisory Committee to oversee the scientific content and validity of a privately commissioned National Research Council preparation of a major Smithsonian Institute exhibit. This new exhibit will feature the science and implications of human-caused climate warming. This exhibit will first be displayed at the Smithsonian, and later will travel around the U.S. as a featured display.