Solar Incoming and Outgoing Radiometry for Climate Studies

While greenhouse gases are critical in climate studies, the main driver of Earth’s climate – by nearly a factor of 10,000 – is the incident total solar irradiance, which LASP is and will be measuring with the Total Irradiance Monitor instruments on the SORCE, Glory, and NPOESS missions. Water vapor and other greenhouse gases, aerosols, land use, and several additional natural and anthropogenic influences affect the absorption of this incoming energy and can be inferred from Earth outgoing radiance measurements that LASP is working toward acquiring on NASA’s future CLARREO mission.

I’ll discuss how LASP measurements are contributing toward improving the total solar irradiance data record and its relevance in estimating climate sensitivities, and describe a concept for a hyperspectral instrument having improved radiometric accuracy to benchmark the Earth’s outgoing shortwave radiation for future climate studies.

Characteristics of the Martian Cryolithhosphere in Zones of Outflow Channel Occurrence

Previous workers have suggested that chaotic terrain formation on Mars occurred in zones of elevated hydraulic head within a global hydrosphere.Our results indicate that chaotic terrain formation in the region of southern circum-Chryse may have resulted from the disruption of thick sedimentary deposits that contained large numbers of buried impact craters. The presented model suggests that these craters were surrounded by dense fracture systems formed during the impact events, and that both the impact crater cavities and their peripheral fractures may form zones of elevated concentrations of volatiles within the cryolithosphere. Overlapping systems of subsurface fractures and craters would have provided extensive systems of highly permeable upper crustal materials enabling distal groundwater migration into the chaotic terrains and the outflow channels, and accounting for the observed patterns of subsidence that extend beyond the margins of chaotic terrains. In addition, non-emergent thrust faults underlying wrinkle ridges may have also been zones of high permeability and aquifer formation. Formation of subsurface cavities filled with volatiles produced by melting of the permafrost and density differentiation (lithics settling relative to the volatile phase) may have also contributed to increasing the degree of subsurface interconnectivity. In summary, our work regarding the Martian cryolithosphere-hydrosphere system is indicative of an important control of tectonic fabrics on the patterns and magnitude of groundwater migration and emergence. In addition, volatile distribution appears highly heterogeneous. These results are consistent with more recent work that SUPPORT a compartmented hydrospheric system on Mars (Andrews-Hanna et al., 2007; Coleman et al., 2007; Harrison and Grimm, 2009).

Enhanced Thermospheric Density: The Roles of East-West and Northward Interplanetary Magnetic Field

ABSTRACT:

During 2005 solar EUV energy input to the thermosphere waned as Solar Cycle 23 declined. The reduction allowed a clearer delineation of episodic density disturbances caused by geomagnetic storms. We show new views of these disturbances based on Poynting flux calculations from the Defense Meteorological Satellite Program (DMSP) F-series satellites, as well as from 1) accelerometer data from polar orbiting satellites, 2) the assimilative mapping of ionospheric electrodynamics (AMIE) procedure.

The new Poynting flux estimates suggest that the origins of some disturbances are poorly specified by ground indices.  In particular we find that intervals of enhanced northward Interplanetary Magnetic Field (IMF) combined with strong east-west components of the IMF allow significant electromagnetic energy input into localized dayside regions of the high-latitude thermosphere. In some cases this energy deposition is consistent with IMF-geomagnetic field merging tailward of the Earth's magnetic cusps. In other cases the energy is deposited in the vicinity of an extremely narrow convection throat. This mode of interaction provides little energy to the magnetotail; and instead concentrates the energy in the dayside thermosphere.  The extreme localized energy flux also appears to be associated with unusual ion upflows.  I will discuss examples of poorly specified neutral density enhancements and their likely sources.

Joint ATOC/LASP seminar

Active and passive remote sensing of the Mesopause region: What do we learn from observing NoctiLucent Clouds (NLC)

Active remote sensing by lidar allows to study processes in the middle atmosphere from small (<1km, 5min) to medium scales (6h) and deliver reliable observations to investigate year to year fluctuations of the atmosphere. Due to the rather complicated instrumental setup only a few lidars are capable of sounding the mesosphere. Especially the polar summer mesopause region offers astonishing processes, e.g. the mean temperature is more than 60K below radiative equilibrium, although the sun is permanently above the horizon. NLC, forming in this region, are a visual manifestation of the extreme state of the atmosphere. These clouds give a very strong signal and can be seen even by eye from ground, although the vertical optical thickness is only about 10-5. Nevertheless from 1018 photons (~100 MW peak power) emitted by the laser only a few are recorded by the detectors. As lidars deliver information only in a small sounding volume the combination with observations from the polar mesosphere cloud imager (CIPS) on the AIM satellite allows to study the dynamics in the mesopause region on larger horizontal scales. Applying state of the art groud based imaging allows to study dynamical processes in NLC extending satellite and lidar observations to extremely small horizontal and temporal scales (<100m, 1sec). Instrumental aspects of lidars, observations and scientific results will be presented.

There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. Laboratory studies are needed for understanding physics of dust charging and dynamics on the lunar surface. Differential photoelectric charging and so-called "supercharging" on the surface near the lunar terminator region were created and studied in laboratory. Dust transport on surface in plasmas was investigated. A dust pile was observed to spread and form a diffusing dust ring on a negatively biased conducting surface in plasma. A dust patch was also found to spread on an electrically floating surface in plasma with an electron beam. Dust hopping was confirmed by noticing grains on protruding surfaces in both experiments. The 2-D electrostatic potential distributions were measured above the dusty surfaces and show electrostatic forces required for transport of the dust particles.