Bulletin of the American Physical Society
80th Annual Meeting of the APS Southeastern Section
Volume 58, Number 17
Wednesday–Saturday, November 20–23, 2013; Bowling Green, Kentucky
Session BC: The Role of Physics in Geosciences: Earth and Atmospheric Physics and Climate Physics |
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Chair: Solomon Bililign, North Carolina A&T Room: 2 |
Thursday, November 21, 2013 8:30AM - 9:06AM |
BC.00001: Visualizing the physics of the invisible atmosphere - the role of lidars and radiometers Invited Speaker: Belay Demoz In this talk, the ``role of physics'' is taken to be synonyms with ``first-principles'' way of looking at the atmospheric structures. The presentation will focus on the role of physics in the development of lidars (and microwave radiometers). A brief discussion of the history of the physics behind these techniques, their atmospheric application and highlights of their use in atmospheric instrumentation will be presented. A major portion of the atmosphere is then dedicated to the application of lidars in bringing out the invisible atmosphere. In the geosciences (specifically meteorology and atmospheric science) -- atmospheric water vapor and aerosol concentration are among the key ingredients. Phenomena that one hears about in print and visual daily life media: pollution, cloud development, precipitation, climate change, floods, draught etc are all mainly (or greatly) influenced by water vapor and aerosols that are around us at all times. The concentration of these quantities spans a large dynamic range and humans are privy (visually) only to a very small portion of that range. Visualization of the water vapor concentration and aerosols has opened our eyes to the abundance and structure of these quantities in the atmosphere. Lidars play a principal role in revealing the everyday atmosphere - its dynamic structure and evolution. We will present examples of ``every day'' atmospheric phenomenon and demonstrate the hidden treasure that lidars reveal. What is the physics behind lidars, what physics controls of the atmosphere do lidars reveal, how can we use them to check numerical models representation of the atmosphere and forecasts? What is the future? These are some of the questions that this talk will discuss. [Preview Abstract] |
Thursday, November 21, 2013 9:06AM - 9:42AM |
BC.00002: The Physics of Clouds: How Aircraft Observations Improve our Knowledge of Clouds for Weather and Climate Studies Invited Speaker: Greg McFarquhar The most fundamental and complex problems in climate and weather center around our poor understanding of cloud properties and our inability to determine effects of cloud processes on weather and climate. Clouds cool Earth by reflecting sunlight and warm it by absorbing infrared radiation: the net impact is a small difference between 2 large terms depending on the size, shape and phases of cloud particles. Clouds also determine how storms evolve, as the latent heat release that drives storms is sensitive to the characterization of cloud particles. Here a comprehensive set of data collected by aircraft probes during projects in the Arctic, Tropics and mid-latitudes is described. Because the base state and variability of cloud properties is used to develop and evaluate cloud parameterization schemes and remote sensing retrievals, the link between cloud properties (ice crystal aspect ratios, crystal shapes, ice crystal size distributions, liquid fractions of mixed-phase clouds) and environmental conditions (location, temperature, total water content, cloud formation mechanism) is presented. Implications for representing cloud microphysics in models and retrieval schemes are discussed. [Preview Abstract] |
Thursday, November 21, 2013 9:42AM - 10:18AM |
BC.00003: Physics in Constraining Observational Data Biases and Investigating Climate Changes in Hydrological Cycle Invited Speaker: Xiangdong Zhang Observations and climate change projections have indicated a wetting trend in northern high latitudes and Arctic. It is therefore imperative to understand underlying causal mechanisms. However, large biases existing in observational data and climate model output bring a great challenge to identify physical processes behind the observed changes in climate. In this study, we employed fundamental physical principals and theory to correct and constrain biases in the reanalysis products and developed a mass-corrected, temporally homogeneous atmospheric moisture transport data from 1948-2008. By using this data, we found that enhancement of poleward atmospheric moisture transport (AMT) decisively contributes to increased Eurasian Arctic river discharges. Net AMT into the Eurasian Arctic river basins captures 98{\%} of the gauged climatological river discharges. The trend of 2.6{\%} net AMT increase per decade accounts well for the 1.8 per decade increase in gauged discharges, and also suggests an increase in underlying soil moisture. A radical shift of the atmospheric circulation pattern induced an unusually large AMT and warm surface in 2006-07 over Eurasia, resulting in the record high discharge. The result from this study has significant implications for better understanding Arctic climate system changes and its interplay with global climate system. [Preview Abstract] |
Thursday, November 21, 2013 10:18AM - 10:30AM |
BC.00004: Active and Passive Optical Remote Sensing techniques for continuous probing of background SE Regional Aerosol vertical Structure Ben Madison, Kevin Holway, Ian Krintz, James Sherman A micro-pulsed lidar (MPL) and a CIMEL scanning sun/sky radiometer are employed by researchers at the Appalachian Atmospheric Interdisciplinary Research facility (AppalAIR) for long-term monitoring of column-averaged and vertically-distributed aerosol properties relevant to regional climate change and air quality. The measurements complement the comprehensive suite of lower tropospheric aerosol optical, microphysical, and chemical properties measured as part of the NOAA-ERSL aerosol monitoring network. Radiometer-measured aerosol optical depth (AOD), made as part of NASA AERONET, is used to calibrate the MPL, which is capable of measuring key aerosol properties over full diurnal cycles and under most meteorological conditions. MPL-derived aerosol properties measured near continuously from May 2012-October 2013 will be presented to illustrate seasonal and diurnal variability in aerosol loading and vertical aerosol structure. Lidar-derived AOD is highly-correlated with CIMEL-measured AOD for all seasons, with summer aerosol loading exceeding that in winter by a factor of 5-7. MPL-derived planetary boundary layer heights will also be presented, including comparisons with those derived from 75 radiosonde launches made as part of a summer 2013 field campaign. [Preview Abstract] |
Thursday, November 21, 2013 10:30AM - 10:42AM |
BC.00005: Hard X-Ray Imaging Spectroscopy of Solar Flares A. Gordon Emslie Large solar flares are characterized by copious emission of hard X-rays produced by bremsstrahlung of accelerated electrons on ambient protons and ions in the target solar atmosphere. Important information on the physics underlying the electron acceleration and transport can be obtained through analysis of the hard X-ray radiation field. The NASA RHESSI mission, launched in 2002, produces hard X\textunderscore ray images with exquisite energy resolution, with user-selectable time and energy bins. Since spatial information is encoded through a Rotating Modulation Collimator instrument design, the immediate data product is not a traditional pixel-by-pixel image but rather a set of two-dimensional spatial Fourier components termed ``visibilities.'' Obtaining information on the spatial distribution population of flare-accelerated electrons therefore involves two inversion steps -- one from the photon domain to the electron domain, and one from the Fourier domain to the spatial domain. I will report on a novel method of performing this analysis, which has provided some very meaningful constraints on the location and physical characteristics of the electron acceleration region, and on the efficiency of the acceleration process itself. [Preview Abstract] |
Thursday, November 21, 2013 10:42AM - 10:54AM |
BC.00006: Meteorological Influence on the Warm-Season Background SE U.S. Aerosol Properties James Sherman, Hadi Morrow, Michael Link, Yong Zhou, Baker Perry Aerosols affect weather and climate directly by scattering and absorbing solar radiation and indirectly through their effects on cloud lifetimes and microphysical properties. These effects represent the largest sources of uncertainty in climate models and may have contributed to the lack of 20$^{th}$ century warming in the SE U.S. The high-elevation site at Appalachian State University (APP) is home to the only co-located NOAA-ESRL / NASA AERONET aerosol monitoring stations in the SE U.S., with a near-continuous multi-year dataset of key aerosol radiative properties used to quantify the aerosol direct radiative effect. Aerosol loading, properties, and chemical composition measured at APP are influenced as much by local and synoptic meteorology as by aerosol source region, particularly during warm-season months, when aerosol radiative effects are largest. Approximately 67{\%} of the non-refractory aerosol mass measured over two summers is organic, with most of the remaining mass comprised of sulfates. The relative fractions, along with most aerosol properties, depend largely on temperature and relative humidity. For this reason, aerosols and meteorology must be studied together in order to better predict the effects of changing air quality on regional climate. [Preview Abstract] |
Thursday, November 21, 2013 10:54AM - 11:06AM |
BC.00007: The Role of Storm Activity in the Enhancement of Poleward Atmospheric Moisture Transport Gian Villamil-Otero, Jing Zhang, Xiangdong Zhang Enhanced poleward atmospheric moisture transport is a driver of streamflow increases into the Arctic Ocean. On the other hand, enhanced storm activities in the northern latitudes have also been detected in both observations and climate projections forced by the greenhouse gas. To investigate what role storm activity plays in enhancing poleward atmospheric moisture transport, this study analyzes the relationship between storm activity and poleward atmospheric moisture transport for the time period from 1948 to 2008 with the NCAR/NCEP reanalysis. The atmospheric moisture transport presents clear regional variations with poleward transport mainly over the North Atlantic Ocean, which contributes 57\% of total poleward transport, and North Pacific Ocean, adding another 33\%. The rest 10\% of total poleward transport is from the Eurasia and North America continents. Similarly storm activity also demonstrates regional variations. Annually, about 208 synoptic storms cross the 60$^{\circ}$N latitude and move northward, which include 68 (33\% of the total) from the North Atlantic Ocean, 56 (27\%) from Eurasia, 47 (23\%) from the North Pacific Ocean, and 37 (17\%) from North America. Correlations between the poleward moisture transport and storm activity include that cyclone intensity and number are generally well correlated with the poleward moisture transport and the regions that contribute the most are the North Atlantic and North Pacific Oceans. [Preview Abstract] |
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