Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Scientific Magazine Articles (9)
- Gravity waves (4)
- Mesosphere (3)
- Publications (3)
- Sediment Transport (3)
-
- Atmospheric gravity waves (2)
- Conference Papers (2)
- Density measurement , Ecosystems , Lagrangian functions , Ocean temperature , Oceanographic techniques , Sea measurements , Temperature distribution , Temperature sensors , Testing , Water , bathymetry , ecology , oceanographic equipment , pressure measurement , pressure sensors , spatial variables measurement , Netburner microprocessor , altitude measurements , altitude sensor , coastal marine ecosystems , dynamic auto-ballasting system , highly varied bathymetry , piston style volume changing mechanism , pressure measurements , pressure sensor , profile sampling , rechargeable lithium ion battery system , seawater density , shallow water Lagrangian float , water densities , drifter , float , sensor platform (2)
- Imagers (2)
- Journal Publications (2)
- Mesospheric dynamics (2)
- SABER (2)
- Temperature (2)
- Acoustic-gravity waves (1)
- Adaptation (1)
- Advective acceleration (1)
- Aggregation (1)
- Airglow (1)
- Airglow layers (1)
- Arctic , Chemistry , Earth , Geology , High-resolution imaging , Ice , Oceans , Robots , Sea floor , Vents , mobile robots , oceanographic techniques , sea ice , seafloor phenomena , underwater vehicles , Earth , autonomous underwater vehicle , deep sea underwater robotic exploration , design decision , ice-covered Arctic ocean , operational change (1)
- Asphalt (1)
- Atmospheric measurement (1)
- Atomic oxygen (1)
- Autonomous robotic vehicles (1)
- Autonomous underwater vehicles, deep-submergence archaeology, towed sidescan sonars, mine-hunting technologies (1)
- Autonomous vehicles (1)
- Be (1)
- Blob removal (1)
- Boundary line extraction (1)
- Breaking acceleration (1)
- Publication
- File Type
Articles 1 - 30 of 64
Full-Text Articles in Physical Sciences and Mathematics
Statistical Characteristics Of Polar Mesospheric Gravity Waves Observed Over Alaska, Michael Negale, Kim Nielsen, Mike J. Taylor, Dominique Pautet, Margit Dyrland
Statistical Characteristics Of Polar Mesospheric Gravity Waves Observed Over Alaska, Michael Negale, Kim Nielsen, Mike J. Taylor, Dominique Pautet, Margit Dyrland
Michael Negale
Short-period (<1 hr) gravity wave observations over the Arctic region are few and their impact on the Arctic mesosphere lower thermosphere (MLT) region via momentum deposition is of high interest, but has yet to be determined. The Mesospheric Airglow Imaging and Dynamics (MAID) project was initiated in January 2011 to investigate the presence and dynamics of these waves over the interior of Alaska. Observations were made from the Davis Building at Poker Flat Research Range (PFRR) (65N) using an all-sky imager. This site provides an exceptional opportunity to establish a long-term climatology of short-period gravity waves in the Arctic. Here, we present summary measurements of prominent gravity waves focusing on their winter-time spatial and temporal characteristics. Measurements were made over two consecutive winters in 2011 and 2012 yielding 117 quasi-monochromatic wave events obtained from sequential OH (715-930 nm) images. Their characteristics are compared with recent gravity wave observations at Resolute Bay, Canada (75N), ALOMAR Station, Norway (69N), Svalbard (78N) in the Arctic, and with Rothera Station (76S) in Antarctic. The distributions of the wave parameters measured at PFRR were found to be similar to those of the other high-latitude sites, except for the direction of propagation. The wave headings observed at PFRR exhibited dominant preference for motion towards the east, while the other high-latitude observations reported westward motion. To investigate the preferred wave directionality, we look at the effects of critical level filtering using zonal and meridional winds obtained from NASA’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) and the Horizontal Wind Model 2007 (HWM07).
Satellite And Ground-Based Measurements Of Mesospheric Temperature Variability Over Cerro Pachon, Chile (30.3° S), Jonathan R. Pugmire, Michael J. Taylor, Yucheng Zhao, P Dominique Pautet, James M. Russell Iii
Satellite And Ground-Based Measurements Of Mesospheric Temperature Variability Over Cerro Pachon, Chile (30.3° S), Jonathan R. Pugmire, Michael J. Taylor, Yucheng Zhao, P Dominique Pautet, James M. Russell Iii
Jonathan Pugmire
Observations of mesospheric OH (6,2) rotational temperatures by the Utah State University Mesospheric Temperature Mapper (MTM) located at the Andes Lidar Observatory, Cerro Pachon, Chile (30.3° S, 70.7° W) reveal a large range of nightly variations induced by atmospheric gravity waves and tides, as well as strong seasonal oscillations. This study investigates MTM temperature variability over the past 4 years comprising over 800 nights of high-quality data and compares the results with MTM measurements from Maui, Hawaii (2001-2005) and coincident mesospheric temperature measurement by the SABER instrument on the NASA TIMED satellite.
Gravity Wave Characteristics In The Lower Atmosphere At South Pole, Matt Pfenniger, Alan Z. Liu, George C. Papen, Chester S. Gardner
Gravity Wave Characteristics In The Lower Atmosphere At South Pole, Matt Pfenniger, Alan Z. Liu, George C. Papen, Chester S. Gardner
Alan Z Liu
A 4-year (1993-1996) temperature and wind data set obtained from over 2000 high-resolution balloon soundings at South Pole is used to study gravity wave characteristics in the atmosphere and lower stratosphere. Extensive analyses of energy density, spectra, and static stability are performed to present a comprehensive view of the gravity waves are ubiquitous and often fairly strong at the South Pole, even though the generation mechanisms are not clear. Gravity wave characteristics are, in general, similar to those obtained at other high-latitude southern hemisphere stations. Potential energies vary between about 0.5 J/kg and 5 J/kg with season and altitude. Variations …
On The Variability Of Mesospheric Oh Emission Profiles, Romina Nikoukar, Gary R. Swenson, Alan Z. Liu, Farzad Kamalabadi
On The Variability Of Mesospheric Oh Emission Profiles, Romina Nikoukar, Gary R. Swenson, Alan Z. Liu, Farzad Kamalabadi
Alan Z Liu
Mesospheric OH radiance limb profiles measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft were inverted to yield altitude profiles of OH volume emission rates. The Abel inversion results of two months of data (from 1 June to 31 July 2004) were analyzed for the layer mean and standard deviation as a function of latitude and local time. Statistical analysis of SABER data shows that the global difference between the mean and standard deviation profiles for the OH(vu = 7, 8, 9; ∆v = 2) emission …
Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner
Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner
Alan Z Liu
Vertical heat flux profiles induced by dissipating gravity waves in the mesopause region (85–100 km altitude) are derived from Na lidar measurements of winds and temperatures at Maui (20.7ºN, 156.3ºW), Hawaii, and compared with earlier results from Starfire Optical Range (SOR, 35.0ºN, 106.5ºW), New Mexico. The heat flux profile at SOR has a single downward maximum of 2.25 ± 0.3 K m/s at 88 km, while the profile at Maui has two downward maxima of 1.25 ± 0.5 K m/s and 1.40 ± 0.5 K m/s at 87 and 95 km, respectively. The common maximum below 90 km can be …
Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson
Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
Characteristics of convective and dynamical instabilities in the mesopause region (between 85 and 100 km) over Maui, Hawaii (20.7ºN, 156.3ºW) are investigated using 19 nights, ~133 hours of high-resolution wind and temperature data obtained by the University of Illinois Na wind/temperature lidar during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaigns. The mean probabilities of convective and dynamical instabilities are observed to be ~3 and 10%, respectively, but there is considerable night-to-night variation. At any given time the probability that an unstable condition is found at some altitudes in the 85–100 km range is 90%. The Maui MALT data …
Vertical Dynamical Transport Of Mesospheric Constituents By Dissipating Gravity Waves, Alan Z. Liu, Chester S. Gardner
Vertical Dynamical Transport Of Mesospheric Constituents By Dissipating Gravity Waves, Alan Z. Liu, Chester S. Gardner
Alan Z Liu
Over 400 h of Na wind/temperature lidar observations, obtained at the Star5re Optical Range, NM, are used to study the vertical dynamical transport of Na in the mesopause region between 85 and 100 km. Dynamical transport occurs when dissipating, non-breaking gravity waves impart a net vertical displacement in atmospheric constituents as they propagate through a region. We show that the vertical constituent flux can be related in a simple way to the vertical heat flux. Breaking gravity waves also contribute to eddy transport by generating turbulence. Because eddy transport is a mixing process, it only occurs in the presence of …
Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson
Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
Atmospheric gravity waves play a significant role in the dynamics and thermal balance of the upper atmosphere. In this paper, we present a novel technique for automated and robust calculation of momentum flux of high-frequency quasi-monochromatic wave components from spectroscopic imaging and horizontal radar wind measurements. Our approach uses the two-dimensional (2-D) cross periodogram of two consecutive Doppler-shifted time-differenced (TD) images to identify wave components and estimate intrinsic wave parameters. Besides estimating the average perturbation of dominant waves in the whole field of view, this technique applies 2-D short-space Fourier transform to the TD images to identify localized wave events. …
O(1s), Oh, And O2(B) Airglow Layer Perturbations Due To Agws And Their Implied Effects On The Atmosphere, Fabio Vargas, Gary Swenson, Alan Liu, Delano Gobbi
O(1s), Oh, And O2(B) Airglow Layer Perturbations Due To Agws And Their Implied Effects On The Atmosphere, Fabio Vargas, Gary Swenson, Alan Liu, Delano Gobbi
Alan Z Liu
The O(1S) (green line) night airglow emission in response to atmospheric gravity wave (AGW) perturbations was simulated with a linear, one-dimensional model. The results were combined with previously modeled O2(b, 0–1) atmospheric band and OH Meinel band emission response (Liu and Swenson, 2003) to derive amplitude and phase relations among multiple airglow layers in response to gravity waves with various intrinsic parameters and damping rates (β). The simulations show that the vertical profile of the standard deviation of the perturbed green line volume emission rate (VER) has a centroid altitude that is 3 km …
An Overview Of Observations Of Unstable Layers During The Turbulent Oxygen Mixing Experiment (Tomex), J. H. Hecht, Alan Z. Liu, R. L. Bishop, J. H. Clemmons, C. S. Gardner, M. F. Larsen, R. G. Roble, G. R. Swenson, R. L. Walterscheid
An Overview Of Observations Of Unstable Layers During The Turbulent Oxygen Mixing Experiment (Tomex), J. H. Hecht, Alan Z. Liu, R. L. Bishop, J. H. Clemmons, C. S. Gardner, M. F. Larsen, R. G. Roble, G. R. Swenson, R. L. Walterscheid
Alan Z Liu
The Turbulent Oxygen Mixing Experiment (TOMEX) was designed to measure the atmospheric response to the existence of unstable layers as determined by wind and temperature measurements from 80 to 105 km. TOMEX combined Na lidar measurements, from Starfire Optical Range in Albuquerque, New Mexico, with a launch of a payload from White Sands Missile Range, located between 100 and 150 km south of Starfire. The payload included a trimethyl aluminum chemical release to measure winds and diffusion, a 5-channel ionization gauge to measure neutral density fluctuations at high vertical resolution, and a 3-channel photometer experiment to measure atomic oxygen related …
Younger Dryas Interval And Outflow From The Laurentide Ice Sheet, T. C. Moore Jr, J. C. G. Walker, D. K. Rea, C. F. M. Lewis, L. C. K. Shane, Alison Smith
Younger Dryas Interval And Outflow From The Laurentide Ice Sheet, T. C. Moore Jr, J. C. G. Walker, D. K. Rea, C. F. M. Lewis, L. C. K. Shane, Alison Smith
Alison Smith
A boxmodel of the Great Lakes is used to estimate meltwater flow into the North Atlantic between 8000 and 14,000 calendar years B.P. Controls on the model include the oxygen isotopic composition of meltwaters and lake waters as measured in the shells of ostracodes. Outflow rates are highest when oxygen isotopic values of the lake waters are most negative, denoting a maximum glacial meltwater component. Flow rates reach maximum values before the onset of the Younger Dryas and after it ends. These maxima appear to be correlative with the major meltwater pulses MWP 1A and 1B. Although the resumption of …
Steady-State Aerosol Distributions In The Extra-Tropical, Lower Stratosphere And The Processes That Maintain Them, J. Wilson, Shan-Hu Lee, J. Reeves, C. Brock, H. Jonsson, B. Lafleur, M. Loewenstein, J. Podolske, E. Atlas, K. Boering, G. Toon, D. Fahey, T. Bui, G. Diskin, F. Moore
Steady-State Aerosol Distributions In The Extra-Tropical, Lower Stratosphere And The Processes That Maintain Them, J. Wilson, Shan-Hu Lee, J. Reeves, C. Brock, H. Jonsson, B. Lafleur, M. Loewenstein, J. Podolske, E. Atlas, K. Boering, G. Toon, D. Fahey, T. Bui, G. Diskin, F. Moore
Shan-Hu Lee
Measurements of aerosol, N2O and OCS made in the Northern Hemisphere below 21 km altitude following the eruption of Pinatubo are presented and analyzed. After September 1999, the oxidation of OCS and sedimentation of particles in the extra-tropical overworld north of 45 N are found to maintain the aerosol in a steady state. This analysis empirically links precursor gas to aerosol abundance throughout this region. These processes are tracked with age-of-air which offers advantages over tracking as a function of latitude and altitude. In the extra-tropical, lowermost stratosphere, normalized volume distributions appear constant in time after the fall of 1999. …
Isoprene Suppression Of New Particle Formation In A Mixed Deciduous Forest, V. P. Kanawade, B. T. Jobson, A. B. Guenther, M. E. Erupe, S. N. Pressley, S. N. Tripathi, Shan-Hu Lee
Isoprene Suppression Of New Particle Formation In A Mixed Deciduous Forest, V. P. Kanawade, B. T. Jobson, A. B. Guenther, M. E. Erupe, S. N. Pressley, S. N. Tripathi, Shan-Hu Lee
Shan-Hu Lee
Production of new particles over forests is an important source of cloud condensation nuclei that can affect climate. While such particle formation events have been widely observed, their formation mechanisms over forests are poorly understood. Our observations made in a mixed deciduous forest with large isoprene emissions during the summer displayed a surprisingly rare occurrence of new particle formation (NPF). Typically, NPF events occur around noon but no NPF events were observed during the 5 weeks of measurements. The exceptions were two evening ultrafine particle events. During the day, sulfuric acid concentrations were in the 106 cm−3 range with very …
The Effect Of Trimethylamine On Atmospheric Nucleation Involving H2so4, M. E. Erupe, A. A. Viggiano, Shan-Hu Lee
The Effect Of Trimethylamine On Atmospheric Nucleation Involving H2so4, M. E. Erupe, A. A. Viggiano, Shan-Hu Lee
Shan-Hu Lee
Field observations and quantum chemical calculations have shown that organic amine compounds may be important for new particle formation involving H2SO4. Here, we report laboratory observations that investigate the effect of trimethylamine (TMA) on H2SO4-H2O nucleation made under aerosol precursor concentrations typically found in the lower troposphere ([H2SO4] of 106−107 cm−3; [TMA] of 180–1350 pptv). The threshold [H2SO4] needed to produce the unity J was from 106−107 cm−3 and the slopes of Log …
A Chemical Ionization Mass Spectrometer For Ambient Measurements Of Ammonia, D. R. Benson, A. Markovich, M. Al-Refai, Shan-Hu Lee
A Chemical Ionization Mass Spectrometer For Ambient Measurements Of Ammonia, D. R. Benson, A. Markovich, M. Al-Refai, Shan-Hu Lee
Shan-Hu Lee
his study presents a chemical ionization mass spectrometer (CIMS) for fast response, in-situ measurements of gas phase ammonia (NH3). The NH3 background level detected with the CIMS ranged between 0.3–1 ppbv, with an uncertainty of 30 pptv under optimized conditions. The instrument sensitivity varied from 4–25 Hz/pptv for >1 MHz of reagent ion signals (protonated ethanol ions), with a 30% uncertainty estimated based on variability in calibration signals. The CIMS detection limit for NH3 was ~60 pptv at a 1 min integration time (3 sigma). The CIMS time response was <30 s. This new NH3-CIMS has been used for …
New Particle Growth And Shrinkage Observed In Subtropical Environments, L. H. Young, Shan-Hu Lee, V. P. Kanawade, T-C. Hsiao, Y. L. Lee, B-F. Hwang, Y-J. Liou, H-T. Hsu, P-J. Tsai
New Particle Growth And Shrinkage Observed In Subtropical Environments, L. H. Young, Shan-Hu Lee, V. P. Kanawade, T-C. Hsiao, Y. L. Lee, B-F. Hwang, Y-J. Liou, H-T. Hsu, P-J. Tsai
Shan-Hu Lee
We present the first systematic analysis for new particle formation (NPF), growth and shrinkage of new particles at four different sites in subtropical central Taiwan. A total of 14 NPF events were identified from 137 days of ambient measurements during a cold and warm season. The measured formation rates of 10 nm particles (J10) and growth rates were in the range of 4.4–30 cm−3s−1 and 7.4–24 nm h−1, respectively. The onset of NPF events coincided with decreases of condensation sink (CS) and increases of SO2 under enhanced atmospheric mixing and dilution. …
Ternary Homogeneous Nucleation Of H2so4, Nh3, And H2o Under Conditions Relevant To The Lower Troposphere, D. Benson, J. Yu, A. Markovich, Shan-Hu Lee
Ternary Homogeneous Nucleation Of H2so4, Nh3, And H2o Under Conditions Relevant To The Lower Troposphere, D. Benson, J. Yu, A. Markovich, Shan-Hu Lee
Shan-Hu Lee
Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements of THN have failed to reproduce atmospheric observations. Here, we report first laboratory observations of THN made under conditions relevant to the lower troposphere ([H2SO4] of 106–107 cm−3, [NH3] of 0.08–20 ppbv, and a temperature of 288 K). Our observations show that NH3 can enhance atmospheric H2SO4aerosol nucleation and the enhancement factor (EF) in nucleation rate (J) due to NH3 (the ratio of Jmeasured with vs. without NH3) increases linearly with increasing [NH3] and increases with …
Alongshore Momentum Balance Analysis On A Cuspate Foreland, Nirnimesh Kumar, George Voulgaris, Jeffery H. List, John C. Warner
Alongshore Momentum Balance Analysis On A Cuspate Foreland, Nirnimesh Kumar, George Voulgaris, Jeffery H. List, John C. Warner
George Voulgaris
Nearshore measurements of waves and currents off Cape Hatteras, North Carolina, U.S.A, are used to investigate depth-averaged subtidal circulation and alongshore momentum balances in the surf and inner shelf region around a cuspate foreland. Data were collected on both sides of the cape representing shorefaces with contrasting shoreline orientation (north-south vs. northwest-southeast) subjected to the same wind forcing. In the nearshore, the subtidal flow is aligned with the local coastline orientation while at the cape point the flow is along the existing submerged shoal, suggesting that cape associated shoals may act as an extension of the coastline. Alongshore momentum balance …
Sediment Resuspension, Flocculation And Settling In A Macrotidal Estuary, Ya Ping Wang, George Voulgaris, Yan Li, Yang Yang, Jianhua Gao, Jia Chen, Shu Gao
Sediment Resuspension, Flocculation And Settling In A Macrotidal Estuary, Ya Ping Wang, George Voulgaris, Yan Li, Yang Yang, Jianhua Gao, Jia Chen, Shu Gao
George Voulgaris
Estuarine boundary layer and water column in situ measurements of hydrodynamics, sediment resuspension and sediment particle size distribution are presented for a macrotidal environment in SE China. Vertical and tidal variability of sediment size and its relation to turbulence and hydrodynamic forcing are examined using time-series from two week long experiments after they are phase averaged to reconstruct typical neap and spring tidal cycles. In situ particle size distributions obtained using laser diffraction show clear evidence of flocculation processes that change dynamically during the tidal cycle. Mean particle size of particles in suspension is found to be one order of …
Uncertainty Associated With Modeling The Global Ionosphere, Janelle Jenniges, Ariel Acebal, Larry Gardner, Robert Schunk, Lie Zhu
Uncertainty Associated With Modeling The Global Ionosphere, Janelle Jenniges, Ariel Acebal, Larry Gardner, Robert Schunk, Lie Zhu
Janelle V Jenniges
A study has been conducted of the effect that different physical assumptions have on global models of the electron density distribution. The study was conducted with the Ionosphere Forecast Model (IFM) and the Ionosphere Plasmasphere Model (IPM) developed by Utah State University. Both physics-based, time-dependent, global models use the same empirical models for the neutral atmosphere (MSIS) and neutral wind (Horizontal Wind Model, HWM), but the altitude range, thermal structure, number of ion species, and magnetic 2ield are different. The IFM covers the altitude range from 90-1400 km, calculates the densities for four ions (NO+, O2+, N2+, O+), has a …
A Model For Calculating Acoustic Gravity Wave Energy And Momentum Flux In The Mesosphere From Oh Airglow, Gary R. Swenson, Alan Z. Liu
A Model For Calculating Acoustic Gravity Wave Energy And Momentum Flux In The Mesosphere From Oh Airglow, Gary R. Swenson, Alan Z. Liu
Alan Z Liu
Acoustic gravity and tidal waves propagating in the mesosphere/lower thermosphere (80-110 km) perturb the airglow layer intensities. The OH airglow has recently been modeled to determine the relationship between the relative perturbed atmospheric density and temperature (ρ’/ ρ, T’/T) to the OH intensity ( I’OH/IOH ) at the OH emission altitudes [Swenson and Gardner, 1997]. A model is presented here which relates wave perturbed OH airglow to the wave energy and momentum flux as they propagate through the emission layer. The model is dependent on the wave horizontal and vertical wavelengths (or phase speed as related through the dispersion relationship), …
A Native American Scientist's Story, Michael Negale
A Native American Scientist's Story, Michael Negale
Michael Negale
No abstract provided.
Eight Aggies Honored In 2013 Nsf Graduate Research Fellow Search, Michael Negale
Eight Aggies Honored In 2013 Nsf Graduate Research Fellow Search, Michael Negale
Michael Negale
No abstract provided.
Airborne Dual-Polarization Observations Of The Sea-Surface Nrcs At C-Band In High Winds, Joseph W. Sapp, Stephen J. Frasier, Jason Dvorsky, Paul S. Chang, Zorana Jelenak
Airborne Dual-Polarization Observations Of The Sea-Surface Nrcs At C-Band In High Winds, Joseph W. Sapp, Stephen J. Frasier, Jason Dvorsky, Paul S. Chang, Zorana Jelenak
Joseph W Sapp
Airborne dual-polarization observations of sea-surface normalized radar cross-section (NRCS) were conducted over the North Atlantic during Jan–Feb 2011. Observations were made using the University of Massachusetts’ Imaging Wind and Rain Airborne Profiler (IWRAP) radar system installed on the National Oceanic and Atmospheric Administration’s (NOAA) WP-3D research aircraft during several winter storm events to determine the high-wind response of the sea-surface NRCS for both horizontal and vertical polarizations. During the flights, the aircraft performed several constant-roll circle maneuvers to allow collection of NRCS over a range of incidence angles. We find consistency with prior reports in the polarization ratio observed at …
Predicting Wave-Induced Ripple Equilibrium Geometry, Timothy R. Nelson, George Voulgaris, Peter Traykovski
Predicting Wave-Induced Ripple Equilibrium Geometry, Timothy R. Nelson, George Voulgaris, Peter Traykovski
George Voulgaris
A comprehensive database of existing (since 1954) field and laboratory measurements of ripple geometry is compiled and combined with newly collected field data to examine the performance of ripple equilibrium predictors. Re-analysis of this enlarged ripple geometry data set reveals that ripples formed from monochromatic waves scale differently than ripples formed from random waves for many existing ripple predictors. Our analysis indicates that ripple wavelengths from the two data sets collapse into a single scaling when the semi-orbital excursion and sediment grain diameter are used as normalizing factors. Ripple steepness remains relatively constant for both regular and irregular wave conditions …
Observations Of Mesospheric Temperature Variability Over The Andes, Jonathan R. Pugmire, Michael J. Taylor, Yucheng Zhao, P Dominique Pautet, James M. Russell Iii
Observations Of Mesospheric Temperature Variability Over The Andes, Jonathan R. Pugmire, Michael J. Taylor, Yucheng Zhao, P Dominique Pautet, James M. Russell Iii
Jonathan Pugmire
Observations of mesospheric OH(6,2) rotational temperatures by the Utah State University Mesospheric Temperature Mapper (MTM) located at the Andes Lidar Observatory, Cerro Pachon, Chile (30.3°S, 70.7°S) reveal a large range of nightly variations induced by atmospheric gravity waves and tides, as well as strong seasonal oscillations. This study investigates MTM temperature variability over the past 3.5 years comprising over 700 nights of high-quality data and compares the results with Maui-MALT, Hawaii MTM (2001-2005) measurements and coincident mesospheric temperature measurement by SABER on the NASA TIMED satellite.
Winter Climatology Of Short-Period Mesospheric Gravity Waves Over Alaska, Michael Negale, Kim Nielsen, Mike Taylor, Dominique Pautet
Winter Climatology Of Short-Period Mesospheric Gravity Waves Over Alaska, Michael Negale, Kim Nielsen, Mike Taylor, Dominique Pautet
Michael Negale
Observations of short-period (<1 hr) gravity waves over the Arctic region are few and their impact on the Arctic MLT region via momentum deposition is of high interest, but has yet to be determined. The Mesospheric and Airglow Imaging (MAID) project was initiated in January 2011 to investigate the presence and dynamics of these waves over the interior of Alaska. Observations were made from the Davis building at Poker Flat Research Range (65○ N). This site provides an exceptional opportunity to establish a long-term climatology of short-period gravity waves in the Arctic. Here we present summary measurements of prominent gravity waves focusing on their winter-time spatial and temporal characteristics as observed using the all-sky imager. Measurements were made over two consecutive winters 2011 and 2012 yielding 117 quasi-monochromatic events. Their characteristics are compared with recent gravity wave observations at Resolute Bay, Canada (75○ N) and ALOMAR, Norway (69○ N) in the Arctic and Rothera station (67○ S) in the Antarctic.
Recent Advances In Drought Monitoring, Mark D. Svoboda, Michael J. Hayes, Donald A. Wilhite, Tsegaye Tadesse
Recent Advances In Drought Monitoring, Mark D. Svoboda, Michael J. Hayes, Donald A. Wilhite, Tsegaye Tadesse
Tsegaye Tadesse
Recent widespread, severe, and long-lasting droughts across North America have heightened awareness of and interest in how to better monitor drought and its impacts. Since its inception in 1999, the National Drought Mitigation Center (NDMC), United States Department of Agriculture (USDA) and NOAA’s Climate Prediction Center (CPC) and National Climatic Data Center (NCDC) have partnered to produce the weekly U.S. Drought Monitor (http://droug ht.unl.edu/m onitor/), a comprehensive drought assessment product based on a simple 5- category severity classification. On the heels of its widespread acceptance and usage, the NCDC, CPC, USDA, NDMC and scientists from Canada and Mexico have worked …
The Need For Integration Of Drought Monitoring Tools For Proactive Food Security Management In Sub-Saharan Africa, Tsegaye Tadesse, Menghestab Haile, Gabriel Senay, Brian D. Wardlow, Cody L. Knutson
The Need For Integration Of Drought Monitoring Tools For Proactive Food Security Management In Sub-Saharan Africa, Tsegaye Tadesse, Menghestab Haile, Gabriel Senay, Brian D. Wardlow, Cody L. Knutson
Tsegaye Tadesse
Reducing the impact of drought and famine remains a challenge in sub-Saharan Africa despite ongoing drought relief assistance in recent decades. This is because drought and famine are primarily addressed through a crisis management approach when a disaster occurs, rather than stressing preparedness and risk management. Moreover, drought planning and food security efforts have been hampered by a lack of integrated drought monitoring tools, inadequate early warning systems (EWS), and insufficient information flow within and between levels of government in many sub-Saharan countries. The integration of existing drought monitoring tools for sub-Saharan Africa is essential for improving food security systems …
Coastal Lagoons And Climate Change: Ecological And Social Ramifications In The U.S. Atlantic And Gulf Coast Ecosystems, Abigail Anthony, Joshua Atwood, Peter August, Carrie Byron, Stanley Cobb, Cheryl Foster, Crystal Fry, Arthur Gold, Kifle Hagos, Leanna Heffner, D. Kellogg, Kimberly Lellis-Dibble, James Opaluch, Candace Oviatt, Anna Pfeiffer-Herbert, Nicole Rohr, Leslie Smith, Tiffany Smythe, Judith Swift, Nathan Vinhateiro
Coastal Lagoons And Climate Change: Ecological And Social Ramifications In The U.S. Atlantic And Gulf Coast Ecosystems, Abigail Anthony, Joshua Atwood, Peter August, Carrie Byron, Stanley Cobb, Cheryl Foster, Crystal Fry, Arthur Gold, Kifle Hagos, Leanna Heffner, D. Kellogg, Kimberly Lellis-Dibble, James Opaluch, Candace Oviatt, Anna Pfeiffer-Herbert, Nicole Rohr, Leslie Smith, Tiffany Smythe, Judith Swift, Nathan Vinhateiro
Peter August
Lagoons are highly productive coastal features that provide a range of natural services that society values. Their setting within the coastal landscape leaves them especially vulnerable to profound physical, ecological, and associated societal disturbance from global climate change. Expected shifts in physical and ecological characteristics range from changes in flushing regime, freshwater inputs, and water chemistry to complete inundation and loss and the concomitant loss of natural and human communities. Therefore, managing coastal lagoons in the context of global climate change is critical. Although management approaches will vary depending on local conditions and cultural norms, all management scenarios will need …