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Seminars (for Scientists) Spring 2011

Below is the schedule of LASP Science Seminars for the Fall 2011 semester. Most dates and speakers will be finalized within one week of the seminar, so check this site often for the most current information. All LASP seminars are open to the public EXCEPT those labeled “internal”.

LASP science seminars are generally on Thursdays from 4:00-5:00 p.m., with refreshments served at 3:45 p.m. Seminars at LSTB (in the East Campus Research Park) are in the main auditorium, room 299, while the seminars at the on-campus Duane building are in room D-142 unless otherwise noted.

Seminars with an asterisk (*) next to its date are not on Thursdays.

For more information or if you have questions contact:

  • Sebastian Schmid
    • Phone: 303-492-6401
    • email: firstname.lastname@lasp.colorado.edu

Spring Semester 2011 Schedule:

DATE Speaker/comment Title/abstract Location
Mar 31 Richard Hodges (LASP) The Lunar Atmosphere: Some Ado About Almost Nothing 

Prior to the Apollo era the lunar atmosphere was thought to be a collision-less, ballistic conduit for thermal evaporation that balances the inflow of solar wind ions with their loss as neutrals. However, the first atmospheric species to be identified on the moon was radiogenic argon-40, and its identification was the indirect result of a search for an explanation of implanted parentless argon-40 in Apollo 11 soil samples. Subsequently, a neutral mass spectrometer at the Apollo 17 site confirmed the presence of atmospheric argon-40 along with helium of both solar and radiogenic origin. These data, although meagre, have guided research into the processes that control the escape of gases from the moon and other bodies that have surface-bounded exospheres. Briefly, the dynamic characteristics of the atmosphere are dominated by ballistic transport, and perturbed by radiation pressure, charge exchange, photo-ionization, and escape to earth orbit. Other, more important, atmospheric processes are related to the surface physics of regolith grains, that is, diffusion, adsorption, desorption, and elastic scattering, which in turn are affected by the influences of orography and heat flow on regolith temperature. With the upcoming launch of the Lunar Atmosphere and Dust Environment Explorer mission, new light should be shed on these processes as well as on the much-expected existence of other constituents.

LSTB-299
Feb 24 Tamás Gombosi Title: TBD 

Abstract pending

LSTB
Feb 10 Lars Dyrud
(Johns Hopkins University, Applied Physics Laboratory)
Radar observation of meteor generated plasmas: understanding the impacts billions of sand and dust sized meteoroids 

Over 100 kilotons of meteoric material hits the Earth every year, yet the average mass, velocity (15-55 km/s), and chemical composition of the particles comprising this mass flux remain poorly constrained. This is because the vast majority of this flux is composed of particles of micron size that are no larger than a grain of sand or piece of dust. Such micro-meteoroids traditionally do not reach the ground becoming meteorites, and their trails are so dim that they are invisible to most optical systems. However, trails produced from micrometeroids generate 1014 or more free electrons at altitudes near 100 km, representing substantial enhancements to the natural ionosphere which presents a comparatively large radar cross section. This seminar will focus on the plasma processes that occur during meteor trail production and evolution and the associated radar reflections that occur during each stage of evolution. Our goal is that by understanding the plasma physics and radar reflection of meteor plasmas, we may provide answers regarding the meteor flux, its influence to the upper atmosphere and ionosphere, and its relation to planetary astronomy and the dangers posed to manned and unmanned space flight.

Duane D-142
Feb 3 Alexander Marshak (NASA Goddard) Title: TBD 

Abstract pending

LSTB
*Jan 28 Peter Bernath Title: TBD 

Abstract pending

Duane, Gamow tower
Jan 20 Graham Feingold
(NOAA ESRL CSD)
The Open-Cellular Cloud System as a Coupled Oscillator 

We explore the underlying principles of self-organization behind closed- and open-cellular mesoscale cloud structures in cloud fields off the west coast of continents. Early surface observations in the 1930s drew parallels to Rayleigh-Benard convection but it was only with the advent of meteorological satellites that observations of mesoscale cellular organization became commonplace. Recent evidence has shown that aerosol particles — through their influence on precipitation formation — help to determine whether cloud fields take on closed or open cellular patterns. Here we use satellite imagery, lidar, and numerical models to show how precipitating clouds produce an open cellular cloud pattern that oscillates between different, weakly stable states. The oscillations are a result of precipitation causing downward motion and outflow from clouds that were previously positively buoyant. The evaporating precipitation drives air down to the Earth’s surface, where it diverges and collides with the outflows of neighboring precipitating cells. These colliding outflows form surface convergence zones and new cloud formation. In turn, the newly formed clouds produce precipitation and new colliding outflow patterns that are displaced from the previous ones. As successive cycles of this kind unfold, convergence zones alternate with divergence zones and new cloud planforms emerge to replace old ones. The result is an oscillating, self-organized system with a characteristic cell size and precipitation frequency.

Duane D-142
*Jan 14 T.B. Ryerson
(Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO)
Deepwater Horizon atmospheric emissions constrain air-water partitioning, hydrocarbon fate, and leak rate 

The fate of deepwater releases of gas and oil is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this air-water partitioning is necessary to constrain simulations of gas and oil transport, to predict marine bioavailability of different fractions of the gas-oil mixture, and to develop a comprehensive picture of the fate of leaked hydrocarbons in the marine environment. Here we show massive amounts (exceeding 226,000 kg/day) of hydrocarbons evaporating from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. Our analysis quantifies the fraction of released hydrocarbons that dissolves in the water column (~33% by mass), the fraction that does not dissolve, and the fraction that is removed promptly by evaporation after surfacing (~14% by mass). This study provides a lower limit to the leak rate of 24,000 to 37,200 barrels of fluid per day, depending on reservoir fluid composition information, and demonstrates an effective new approach for rapid-response airborne assessment of future oil spills.

Duane D-142