Remote Sensing Institute Seminar Series

April 20

Vapor Deposition of Water Ice on Surrogates of Martian Dust: Implications for Cloud Formation and the Hydrologic Cycle
Laura T. Iraci, NASA Ames
The role of water ice clouds in the Martian water cycle and climate depends on cloud properties such as particle size and number distribution. These properties, in turn, depend on poorly understood heterogeneous nucleation parameters. Using classical nucleation theory, we have investigated the effect of substrate mineralogy and other parameters on model variables such as the contact parameter, m, and critical saturation ratio, S. Laboratory experiments have been performed under Martian temperature and water partial pressure conditions to determine S as a function of temperature and dust composition. Using infrared spectroscopy to monitor ice nucleation and growth, we find a significant barrier to ice formation (saturation ratios ranging from 1.1 to 3.3) and a pronounced temperature dependence between 158 and 185 K. Below 175 K, significant supersaturation conditions may be required to nucleate water ice clouds on dust particles. Even on clay minerals which show uptake of water before ice nucleation, we find a saturation ratio of 3 or more (RHice > 300 %) is needed to begin ice growth at temperatures near 160 K.

Current microphysical model predictions for water cloud formation use much lower saturation thresholds, and thus they will require significant revision to account for the new laboratory findings. In addition to the primary data, we will also present preliminary results from a Mars General Circulation Model updated with the measured critical saturation conditions. Changes are seen in both the atmospheric water content and the surface frost location and amount. In general, our laboratory findings suggest that cloud formation will be more difficult than previously thought, leading to drier conditions in the atmosphere and near-surface regions of Mars.

New results for water uptake and ice nucleation on JSC-1 Mars simulant will also be presented, and possible application of these data to the mesospheric clouds on Earth will also be discussed.

April 13

Real-time Air Quality Modeling (RAQMS) chemical and aerosol assimilation studies during the 2008 NOAA Aerosol, Radiation, and Cloud Processing affecting Arctic Climate (ARCPAC) field mission
Brad Pierce, NOAA/NESDIS/CIMSS
During April 2008, as part of the International Polar Year (IPY), NOAA’s Climate Forcing and Air Quality Programs engaged in an airborne field measurement campaign in the Alaskan Arctic. The Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) field mission (Fairbanks AK) focused on direct measurements of properties and processes designed to address four major areas of non-greenhouse-gas atmospheric climate forcing:
1. Direct warming of the lower troposphere by the absorption of solar radiation and IR emission by aerosol particles from anthropogenic and biomass burning sources.
2. Changes in snow melt due to deposition of soot (light-absorbing carbon) to the surface in springtime.
3. Increases in IR emissivity of wintertime and springtime clouds in the Arctic due to the effects of anthropogenic aerosol particles on cloud properties.
4. Direct radiative effects of tropospheric ozone in the Arctic.
The Real-time Air Quality Modeling System (RAQMS) chemical and aerosol forecasts, initialized with real-time satellite measurements (e.g. Aura OMI column ozone and MLS ozone profiles, Terra and Aqua MODIS AOD) where used for daily flight planning activities during ARCPAC. This seminar presents preliminary results from post mission studies focused on integration of RAQMS analyses, satellite, ground based, and airborne observations for evaluation of the impacts of long-range transport of anthropogenic pollution, halogen chemistry, and stratosphere-troposphere exchange on the chemical and aerosol composition of the Arctic.

April 6

Atmospheric Organic Matter Composition Analysis by Ultra-high Resolution Mass Spectrometry
Lynn Mazzoleni, Michigan Tech
Atmospheric organic matter is a complex mixture of organic compounds derived from both primary emissions and secondary oxidation processes. Atmospheric oxidation processes transform the composition of organic matter associated with aerosol particles and cloud droplets. As aerosol organic matter is oxidized it becomes more water soluble; this evolution affects the physical properties of aerosol particles (hygroscopicity, solubility, wettability, ice nucleation capability, & optical characteristics). Thus, understanding the molecular composition of organic compounds in cloud/fog droplets and aerosol particles is crucial for assessment of the effect aerosol particles have on Earth’s climate system. However despite many efforts, the nature, identity, and origin of these compounds are still not well understood. This stems largely from the many analytical challenges these compounds present. Ultra-high resolution mass spectrometry is an extremely powerful technique for separating and accurately measuring the mass of ionized molecules. One of the greatest benefits of this measurement is the ability to calculate with good certainty the empirical formulas of the individual analytes. Additionally, the high sensitivity of this instrument allows for the analysis of water samples without pre- concentration or chemical derivatization techniques. In our analysis of atmospheric fogwater , we used electrospray ionization with ultra-high resolution FT-ion cyclotron resonance mass spectrometry and found very complex mass spectra with hundreds of individual organic compounds within a short mass range. The identified atmospheric organic compounds appear to be polyfunctional with several polar functional groups often including oxides of nitrogen, oxides of sulfur, and/or both oxides of nitrogen and sulfur. In this seminar, I will present these findings and discuss the major challenges that remain in determining the composition of atmospheric organic matter.

March 30

Biogenic Volatile Organic Compound Emissions in a Changing Earth System
Alex Guenther, National Center for Atmospheric Research, Senior Scientist and Section Head
Biogenic Volatile Organic Compounds (BVOC) produced by living vegetation are the world’s largest source of hydrocarbon emissions into the atmosphere. The biological function of some VOC emissions are well known, including attraction of pollinators and repelling pests, but identifying the purpose of other compounds including the globally dominant VOC emission, isoprene (C5H8), has been elusive. Estimates of BVOC emissions have been an integral component of regional air quality and global atmospheric chemistry models for nearly two decades. These compounds play an important role in determining atmospheric distributions of ozone, aerosols, OH, and other constituents that control climate and air quality. Procedures were originally developed for generating static emission inventories but are now increasingly used for on-line dynamic models that can simulate earth system interactions. Current BVOC emission estimates are representative of unstressed plants in a stable environment. Improved estimates of present day emissions and future predictions require accurate simulations of the response of emissions to stress and a changing earth system. Stressors such as extreme weather, chemical pollution, and biological pests can modify BVOC emissions in ways that are difficult to quantify. Earth system changes that are expected to dramatically change BVOC emissions include land-use, warming, drying, and elevated carbon dioxide although the impact on regional to global BVOC emissions remains unclear. Major challenges associated with this task include both measurements of BVOC emission response to stress and the compilation of controlling variables that can be used to drive stress-dependent BVOC emission variations. Observations of BVOC emission response to stress and other controlling factors are presented and the need and approaches for their incorporation into regional and global models are described. Opportunities for university participation in ongoing earth system model development and upcoming field study programs are also discussed.

March 23

Carbonaceous Aerosol as Atmospheric Ice Nuclei
Anthony Prenni, Colorado State University
Ice nuclei (IN) are those particles which catalyze ice nucleation in the atmosphere. Ambient measurements suggest that the main particle types that function as IN are metal oxides and dust. However, carbonaceous particles often are the next most abundant IN particle type, although the source and exact chemical compositions of these particles are unknown. In this talk, I will present laboratory and field data aimed at characterizing the ice nucleating ability from several potential sources of carbonaceous aerosol. These include secondary organic aerosol, diesel exhaust, biomass burning particles and primary biological aerosol particles. These data suggest that biomass burning and primary biological particles both may impact IN concentrations on a regional scale.

March 16

Remote sensing of boundary-layer turbulence with lidars and radars
Donald H. Lenschow, National Center for Atmospheric Research
Measurements of backscattered electromagnetic radiation that has been transmitted in a narrow pulsed beam are now widely used for remote sensing of atmospheric phenomena. A particularly useful application is using the Doppler shift to measure the velocity of scatterers along the beam. The transmitted beam can be either coherent radio waves (radar), or infrared to visible waves (lidar). Radars mostly sense backscatter from precipitation and cloud droplets, while lidars can sense backscatter from clear-air atmospheric aerosols. Therefore, radars can measure particle motions within (and often beneath) clouds but not in clear air. In contrast to clear-air aerosols, water droplets can have fall velocities comparable to vertical air-velocity fluctuations, which needs to be taken into account in obtaining actual air velocity fluctuations from radars. Both radars and lidars exist that have the ability to measure turbulence in the planetary boundary layer (PBL).

I will discuss applications of this technology using two very different systems: (1) an airborne Doppler radar (the Wyoming Cloud Radar) mounted on the NCAR C-130 aircraft and used to probe the marine stratocumulus-capped PBL off the California coast; and (2) A ground-based High Resolution Doppler Lidar (HRDL) used to probe the clear-air convective PBL over farmland in central Illinois.

March 2

A New Model System Aimed to Simulate Interdisciplinary Multi-Scale Oceanic Processes: A Tool for Great Lakes’ Ecosystem Studies
Changsheng Chen, University of Massachusetts-Dartmouth
A state-of-art coastal ocean model requires 1) grid flexibility to resolve the complex coastline and steep continental slopes as well as multi-scale (global-basin-coastal region-estuarine) physical processes; 2) accurate numerical methods that conserve mass, heat and salt; 3) proper parameterization of vertical and lateral mixing, 4) advanced data assimilation methods to integrate observations with simulation results, 5) modular design to facilitate selection and/or addition of essential model components needed in both scientific or management applications. This model should be a robust and open-source system with a flexible user interface and supported by an expanding base of users that continue to improve it. A major step towards such a system has been taken by a team of University of Massachusetts-Dartmouth and Woods Hole Oceanographic Institution researchers who have developed a new prognostic, free-surface, three-dimensional primitive equations-based unstructured-grid, Finite-Volume Coastal Ocean Model (FVCOM). The finite-volume method used in this model combines the advantage of finite-element methods for geometric flexibility and finite-difference methods for simple discrete computation. FVCOM has been successfully applied in estuarine, continental shelf, regional, basin and global ocean studies involving realistic model domains (for more information go here). Several examples for multi-scale applications will be presented, including Lake Superior.

The present version of FVCOM includes a number of options and components, including: (1) choice of Cartesian or spherical coordinate system, (2) a mass-conservative wet/dry point treatment to simulate the flooding/drying process, (3) the General Ocean Turbulent Model (GOTM) modules for optional vertical turbulent mixing schemes, (4) several water-quality modules to simulate dissolved oxygen and other environmental indicators, (5) four-dimensional nudging, optimal interpolation, and Reduced/Ensemble Kalman Filters for data assimilation, (6) a fully nonlinear ice model for Arctic Ocean studies, (7) a three-dimensional sediment transport module for estuarine and near-shore applications, (8) a generalized biological module (GBM) for food-web dynamics, and (9) unstructured grid surface wave model modified from SWAN. GBM allows users to either select a prebuilt biological model or to build their own biological model using the pre-defined pool of biological variables and parameterization functions. FVCOM has been upgraded to the semi-implicit version, which allows users to choose either mode-split or semi-implicit schemes. Both schemes have included the non-hydrostatic dynamics, which can be used to resolve the small-scale internal waves and vertical convection. An automatic configuration of nesting module has been built into FVCOM, which allows to run multiple computational domain experiments through mass conservative nesting approach.

For hindcast and forecast applications, an integrated coastal ocean model system has developed. An example is the Northeast Coastal Ocean Forecast System (NECOFS), which has been used by the US National Weather Stations, local government agencies, and private companies. NECOFS is an integrated atmosphere-ocean model system in which the ocean model domain covers the northeast US coastal region (the New England Shelf, Georges Bank, the Gulf of Maine, and the Scotian Shelf) with a horizontal resolution of 10-15 km in the open ocean, 1-5 km on the shelf, and down to 20 m in estuaries, inner bays, inlets and harbors. The system includes: 1) two community atmospheric mesoscale models, WRF (Weather Research and Forecasting model) and MM5 (fifth generation NCAR/Penn State model), modified to incorporate the COARE 2.6 air-sea flux algorithm); 2) the unstructured-grid Finite-Volume Coastal Ocean Model configured for this region (FVCOM-GOM) with a nested higher resolution FVCOM configured for Massachusetts coastal waters (FVCOM-MASS); 3) the unstructured-grid surface wave model (FVCOM-SWAVES); and 4) the FVCOM-based unstructured-grid sediment model. In its present initial stage, the forecast system is built based on WRF, MM5 and FVCOM-GOM/FVCOM-MASS. Both meteorological and ocean models have been tested through comparison with field data in hindcast experiments covering the period 1979 to present. The system produces 3-day forecast fields of surface weather, surface waves, water temperature, salinity, and currents, with daily updating using hindcast data assimilated fields whenever field data are available. FVCOM-GOM and FVCOM-MASS are being upgraded with a new semi-implicit FVCOM code, which will allow regional and coastal as well as estuarine model runs with significant reduction in computational power. A brief description of NECOFS and some critical issues in the model application to the forecast operation are discussed in this presentation. This system is a potential candidate that can be set up for Lake Superior.

February 23

Effect of Aerosol Mixing State on Optical and CCN Activation Properties in an Evolving Urban Plume
Nicole Riemer, University of Illinois
Atmospheric aerosols can be composed of a complex mix of compounds such as soluble inorganic salts and acids, insoluble crustal materials (dust), trace metals, and carbonaceous materials, which include primary and secondary organic compounds of anthropogenic and biogenic origins as well as soot formed as result of fossil fuel combustion and biomass burning.

The composition of individual atmospheric aerosol particles, the so-called mixing state, is of crucial importance for assessing their impacts on precipitation and climate. However, tracking the mixing state in conventional aerosol models requires treating a multidimensional size distribution, which is computationally prohibitive. Therefore current models usually assume an internal mixture within one mode or size section. The uncertainties associated with this assumption, which artificially ages freshly emitted particles instantly, are not well quantified.

In this seminar I will present a new approach, the stochastic particle resolved model PartMC-MOSAIC, which explicitly resolves the composition of individual particles in a given population of different types of aerosol particles, and accurately tracks their evolution due to emission, dilution, condensation and coagulation. PartMC-MOSAIC is applied to an idealized urban plume case to simulate the evolution of urban aerosols of different types due to coagulation and condensation. For this urban plume scenario I will quantify the individual processes that contribute to the aging of the aerosol distribution and demonstrate the effect of aerosol mixing state on optical and CCN activation properties.

February 16

Potential methods for quantifying the ecophysiology of entire mountain watersheds
Tom Pypker, Michigan Tech
Abstract (pdf)

February 9

Characterization of vertical transport of fire smoke over North America using satellite observations
Maria val Martin, Harvard
Wildfires are a major source of reactive trace gases and aerosols in the atmosphere. Fire emissions can be injected above the boundary layer due to the strong buoyancy generated from the fires, with important implications for long-range transport of these emissions and their effects on atmospheric composition. Quantifying and modeling fire emission heights is a difficult task, due to the large variability in the types of fire regimes and ecological regions as well as the scarcity of plume height observations. Here, I present a study of aerosol injection heights over North America using five years of stereo-height retrievals and fire radiative power of wildfire plumes obtained from the NASA Terra Multi-angle Imaging SpectroRadiometer (MISR) and MODerate resolution Imaging Spectroradiometer (MODIS), respectively. The analysis of observed MISR plume heights in combination with meteorological and vegetation land cover data indicates that an important fraction (5-30%) of plumes from fires over North America injects smoke into the free troposphere. A further analysis shows that plume height depends on fire characteristics (e.g., fire intensity and size), atmospheric stability and year-to-year variations. The smoke rise behavior has important implications for modeling analysis and these results suggest that the use of a constant injection height in global and regional chemical transport models is not realistic. A parameterization of injection heights of wildfire plumes over North America is developed using a 1-D plume-resolving model driven by ambient conditions and MODIS-derived fire properties (e.g., fire area, heat flux). Simulated heights of the plumes are evaluated at a local scale using injection heights observed by MISR.

February 2

How simple radiative transfer helps to interpret satellite measurements; examples from active and passive remote sensing
Alexander Marshak, NASA, Goddard Space Flight Center
We discuss the two NASA’s Earth Observing System missions: one active and one passive remote sensing. As an example of active remote sensing, we illustrate a space-borne lidar that emits infrared and visible laser pulses and provides elevation data needed to determine ice sheet mass balance. As an example of passive remote sensing, we show a space-borne radiometer that uses solar radiation to retrieve cloud and aerosol properties. However, it is difficult to distinguish between cloudy and cloud-free areas in remote sensing observations. For space lidars, undetected clouds may increase the photon path length, thus making the surface appear farther from the satellite introducing errors in surface height change detection. For solar radiometers, due to extra illumination from clouds, clear sky areas near clouds may appear brighter, thus overestimating aerosol optical depth. We discuss simple radiative transfer models that can help us to better understand and correctly interpret those measurements. 

January 26

Volcanism, dust, and auroral spots: Exploring Jupiter's space environment
Peter Delamere, Laboratory for Atmospheric and Space Physics, University of Colorado - Boulder
Io, the innermost of Jupiter's four large satellites, is the most volcanically active moon in the solar system.  Io's prodigious volcanic activity may be 100 times greater than that found at Earth and leads to its sulfur dioxide atmosphere.  Perhaps the most dramatic observable phenomenon from Earth is the interaction of Io's atmosphere with Jupiter's rapidly rotating magnetosphere.  This plasma interaction generates a million amps of current, a million megawatts of power and removes about a ton of sulfur and oxygen atoms per second from Io's atmosphere.  We will explore the peculiar role of Io in Jupiter's magnetosphere through nearly 50 years of Earth-based and space-based observations of this complex system.