Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 57, Number 11
Friday–Saturday, October 26–27, 2012; Socorro, New Mexico
Session H5: Atmospheric Physics II |
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Chair: Jeff Lapierre and Sharon Sessions, New Mexico Institute of Mining and Technology Room: Macey Center Agora |
Saturday, October 27, 2012 10:12AM - 10:24AM |
H5.00001: The Moist Entropy Change in Tropical Cyclones Ana Juracic Important part of moist entropy budget is the advection of moist entropy in or out of the system, due to interaction of wind and moist entropy fields. The dropwindsonde data from several tropical storms is used to calculate both of those fields, as well as the resulting flow. In order to determine if the storm is exporting or importing moist entropy, the advection is horizontally averaged and vertically integrated. The storms of interest were Alex, Karl, Gaston and Fanapi from 2010. First three occurred in Atlantic basin while Fanapi evolved over Pacific basin. Gaston is the only one that was not developing during dropsonde missions, so it can be used as some kind of indicator of non-developing features in the entropy flux. The data show that during the development of the storm, the values of the moist entropy export are lower than for non-developing systems. [Preview Abstract] |
Saturday, October 27, 2012 10:24AM - 10:36AM |
H5.00002: The sensitivity of multiple equilibria in a cloud resolving model to sea surface temperature changes in weak temperature gradient simulations Stipo Sentic, Sharon Sessions In the tropics, gravity waves quickly redistribute buoyancy anomalies, which leads to approximately weak temperature gradients (WTG) in the horizontal. In our cloud resolving model (CRM), the WTG approximation is enforced by relaxing potential temperature perturbations to a reference profile which represents the mean state of the atmosphere. To obtain reference profiles, the model is run in a non-WTG mode until radiative convective equilibrium (RCE). RCE vertical profiles of temperature and moisture are then used as reference profiles for WTG simulations. Continuing the work of Sessions et al (2010), we investigate the sensitivity of multiple equilibria in a CRM to changes in sea surface temperatures (SST). Multiple equilibria refers to a precipitating or non-precipitating steady state under identical forcing conditions. Specifically, we run RCE simulations for different SSTs to generate reference profiles representing different large scale environments for WTG simulations. We then perform WTG experiments for each SST with varying surface wind speeds. The model domain is initialized either with a completely dry troposphere, or with a RCE moisture profile. We find that the range of wind speeds maintaining both a dry and a precipitating steady state is strongly dependent on SST. [Preview Abstract] |
Saturday, October 27, 2012 10:36AM - 10:48AM |
H5.00003: Simulation Procedure for Optical Wave Propagation through Atmospheric Aerosols Mazen Nairat, David Voelz The effects of atmospheric aerosols on optical propagation have been studied primarily for a homogeneous medium and in a time-averaged sense. We describe an approach for including the effects of aerosol scatter in the wave optics simulation format. The aerosol medium is modeled using a series of phase screens placed along the propagation path in such a way that their distribution depends on the aerosol's density. The aerosol scattering point spread function is translated into a collection of phase screen realizations. The results obtained emphasize that the simulation procedure is applicable in non homogenous medium with varying scatter phase functions. Indeed, the procedure can be combined with other wave optics simulation procedures such as the propagation through turbulence. [Preview Abstract] |
Saturday, October 27, 2012 10:48AM - 11:00AM |
H5.00004: Understanding Stratospheric Air Motions using an Atmospheric Tape Recorder Kenneth Minschwaner, Gloria Manney, Hui Su, Jonathan Jiang The primary mode for the flow of air in Earth's stratosphere is the Brewer-Dobson circulation, which is characterized by upward motion in the tropics, a general flow towards higher latitudes, and downward motion at the poles. This circulation exerts a major influence on the distributions of stratospheric compounds such as ozone, water vapor, methane, nitrous oxide, and many other long-lived trace gases. The strength of the circulation, as assessed from vertical wind speeds in the tropics, is very difficult to quantify using direct measurements since speeds are so slow, on the order of tens of meters per day. A unique tool for quantifying this ascent is the ``tropical tape recorder'' - the upward propagation of seasonal variations imprinted on water vapor and carbon monoxide mixing ratios at the base of the tropical stratosphere. We will present results from the tape recorder signal using measurements from the NASA Microwave Limb Sounder satellite instrument, including vertical wind speeds and their connection to the radiative energy balance of the stratosphere. [Preview Abstract] |
Saturday, October 27, 2012 11:00AM - 11:12AM |
H5.00005: Using SDO-EVE Satellite Data to Model for the First Time how Large Solar Flares Influence the Earths Ionosphere Joseph Jensen, Jan Sojka, Robert Schunk, Michael David, Tom Woods, Frank Eparvier The earth's ionosphere is very important in our everyday life. During large solar flares the ionosphere expands to the point of disrupting communications from GPS, military, and commercial communications satellites, and even radio blackouts can occur. The EVE instrument on the SDO satellite has given unprecedented spectral resolution for the Extreme Ultraviolet(EUV) spectrum with a time cadence of 10 seconds. This has made it possible to analyze flare spectra as never before. Using the Time Dependent Ionospheric Model (TDIM) we have input this new spectral data for large solar flares and analyzed the effect on the ionosphere. We take as a test case the X1.6 flare on March 9, 2011. Even this minor X-class provides insight into how the ionospheric layers respond differently to solar flares. [Preview Abstract] |
Saturday, October 27, 2012 11:12AM - 11:24AM |
H5.00006: Characterization of Jupiter's Deep Circulation and Static Stability through Wide Channel Numerical Simulations of the Dynamics and Interactions of Southern Midlatitudes Vortices Raul Morales-Juberias, Timothy Dowling Previous studies have shown that the observed features and dynamics of Jovian vortices are sensitive to the underlying environmental structure of Jupiter's atmosphere, in particular to the vertical wind shear and the static stability, and that forward modeling techniques can be successfully used to eliminate a large range of possibilities in a self-consistent manner and hence constrain the atmospheric structure below the cloud regions (Youseff and Marcus 2003, Morales-Juberias et al. 2005). However, these studies have generally been done on a narrow latitude-band basis ($\approx 15^\circ$). Here we present wide channel simulations ($\approx 40 ^\circ$) of two major meteorological events observed in the southern atmosphere of Jupiter involving the interaction of the Great Red Spot (GRS) with other nearby vortices. By studying these two events using wide channel simulations, not unlike the strategy used in terrestrial synoptic meteorology, we show that we can gain new insights into the patterns governing Jupiter's global circulations, drawing a coherent picture of the vertical structure of the atmosphere for the whole southern mid-latitudinal regions of Jupiter over time. [Preview Abstract] |
Saturday, October 27, 2012 11:24AM - 11:48AM |
H5.00007: What Makes Precipitating Atmospheric Convection Different? Invited Speaker: David Raymond The word ``convection'' refers to the upward and downward motions induced by the buoyant release of gravitational potential energy in an unstably stratified fluid. Convection occurs in many contexts, including oceans, planetary atmospheres, stars, and in laboratory and industrial processes. Convection in the earth's atmosphere can be subdivided into three types; that with no condensed water, that with condensed water but no precipitation, and that with precipitation. The first two categories have similar characteristics and are both similar in character to many other forms of convection, e.g., in the atmospheres of stars. Convection with precipitation differs in a fundamental way from other convection because of the fallout of condensed water substance from ascending parcels in the form of rain, hail, and snow. The net effect of this fallout is that the narrow convective updrafts are heated rapidly via the release of latent heat, whereas much of the descending air subsides only slowly over a vast area under the influence of thermal radiative cooling. Other descending parcels have their descent hastened by the evaporative cooling of precipitation falling through them. A final complication comes from the processes responsible for the formation of precipitation from the tiny droplets produced by condensation in updrafts. Rain and snow formation depend heavily not only on the kinematics of updraft motion, but also on the population of atmospheric aerosols. The representation of precipitating atmospheric convection in large-scale numerical models of the atmosphere is one of the greatest unsolved problems facing weather and climate prediction. [Preview Abstract] |
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