Atmospheric Sciences Commons^™

Optical Estimation Of Auroral Ion Upflow: Theory, M. Zettergren, J. L. Semeter, P. L. Blelly, M. Diaz

Publications

This work presents a systematic analysis of optical emissions related to auroral ion upflow. Optical intensities and field‐aligned ion transport are computed for a set of monoenergetic incident electron beams using a combined fluid‐kinetic model. The kinetic portion models the energetic particle transport with a multiple stream approach and provides ionization, excitation, and heating rates to an eight‐moment fluid model of the ionosphere, which then calculates the resulting ion upflow. The analysis is used to develop a technique for estimating upward ion flux from photometric measurements at five discrete wavelengths: 427.8 nm, 557.7 nm, 630.0 nm, 732 nm, and 844.6 …

Validation Of The Aura Microwave Limb Sounder Hnomeasurements, M L. Santee, A Lambert, W G. Read, N J. Livesey, R E. Cofield, D T. Cuddy, W H. Daffer, B J. Drouin, L Froidevaux, R A. Fuller, R F. Jarnot, B W. Knosp, G L. Manney, V S. Perun, W V. Snyder, P C. Stek, R P. Thurstans, P A. Wagner, J W. Waters, G Muscari, R L. De Zafra, Jack E. Dibb, D W. Fahey, P J. Popp, T P. Marcy, K W. Jucks, G C. Toon, R A. Stachnik, P F. Bernath, C D. Boone, K A. Walker, J Urban, D Murtagh

Earth Sciences

We assess the quality of the version 2.2 (v2.2) HNO₃ measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS HNO₃ product has been greatly improved over that in the previous version (v1.5), with smoother profiles, much more realistic behavior at the lowest retrieval levels, and correction of a high bias caused by an error in one of the spectroscopy files used in v1.5 processing. The v2.2 HNO₃ data are scientifically useful over the range 215 to 3.2 hPa, with single-profile precision of ∼0.7 ppbv throughout. Vertical resolution is 3–4 km …

Total Depletion Of Hg° In The Upper Troposphere-Lower Stratosphere, R. Talbot, Huiting Mao, Jack E. Dibb, M A. Avery

Earth Sciences

Our current understanding of atmospheric mercury lacks fundamental details. Gas phase elemental mercury (Hg°) was measured aboard the NASA DC-8 research aircraft during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) conducted in spring 2006 over the North Pacific. Our data confirm efficient chemical cycling of Hg° in the tropopause region and show that it is strongly anti-correlated with O₃ there, yielding a tropospheric-stratospheric mixing curve of ∼−0.20 ppqv Hg°/ppbv O₃. In addition, we found frequent total depletion of Hg° in upper tropospheric (8–12 km) air masses impacted by stratospheric influence. When O₃ mixing ratios were >300 …

Diagnosis Of The July 6, 2002 Ogallala, Nebraska Flash Flood, David B. Radell, Mark R. Anderson, John W. Stoppkotte, James R. Mccormick

Department of Earth and Atmospheric Sciences: Faculty Publications

During the early morning hours of 6 July 2002, a mesoscale convective system (MCS) traversed southwestern Nebraska and produced more than 40 cm of precipitation, resulting in a flash flood that closed Interstate 80 and caused one fatality near Ogallala, Nebraska. Regional climatology yields that this flash flood ranked first in precipitation amount for a 24 hour period over the past one hundred years. Synoptic and mesoscale features similar to other flash flooding events and conducive to extremely heavy precipitation were in place over the Central Plains, including a weak upper level ridge, high precipitable water values (180% of normal), …

A Summer Time Series Of Particulate Carbon In The Air And Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb

Earth Sciences

Carbonaceous particulate matter is ubiquitous in the lower atmosphere, produced by natural and anthropogenic sources and transported to distant regions, including the pristine and climate-sensitive Greenland Ice Sheet. During the summer of 2006, ambient particulate carbonaceous compounds were characterized on the Greenland Ice Sheet, including the measurement of particulate organic (OC) and elemental (EC) carbon, particulate water-soluble organic carbon (WSOC), particulate absorption coefficient (σ_ap), and particle size-resolved number concentration (PM_0.1–1.0). Additionally, parallel ∼50-day time series of water-soluble organic carbon (WSOC), water-insoluble organic carbon (WIOC), and elemental carbon (EC) were quantified at time increments of 4–24 …

A Statistical Model To Forecast Short-Term Atlantic Hurricane Intensity, Kevin Law, Jay S. Hobgood

Geography Faculty Research

An alternative 24-h statistical hurricane intensity model is presented and verified for 13 hurricanes during the 2004–05 seasons. The model uses a new method involving a discriminant function analysis (DFA) to select from a collection of multiple regression equations. These equations were developed to predict the future 24-h wind speed increase and the 24-h pressure drop that were constructed from a dataset of 103 hurricanes from 1988 to 2003 that utilized 25 predictors of rapid intensification. The accuracy of the 24-h wind speed increase models was tested and compared with the official National Hurricane Center (NHC) 24-h intensity forecasts, which …

Seasonal And Diel Variation Of Atmospheric Mercury Concentrations In The Reno (Nevada, Usa) Airshed, Jelena Stamenkovic, Seth Lyman, Mae S. Gustin

USU Uintah Basin Faculty Publications

This paper describes total gaseous mercury (TGM) concentrations measured in Reno, Nevada from 2002 to 2005. The 3-year mean and median air Hg concentrations were 2.3 and 2.1 ng m−3, respectively. Mercury concentrations exhibited seasonality, with the highest concentrations in winter, and the lowest in summer and fall. A well-defined diel pattern in TGM concentration was observed, with maximum daily concentrations observed in the morning and minimum in the afternoon. A gradual increase of TGM concentration was observed in the evening and over night. The early morning increase in TGM was likely due to activation of local surface emission sources …

Droughtscape, Fall 2007, National Drought Mitigation Center

DroughtScape: Quarterly Newsletter of the National Drought Mitigation Center (2007–2023)

Fall 2007 Outlook

Diverse Impacts Reported in Summer of 2007

Decadal Climate Cycles Hold Predictive Potential

Drought Experts Take Roadmap to Congress

NDMC Research Updates

Particulate And Water-Soluble Carbon Measured In Recent Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb, Casey Anderson, Eric J. Steig

Earth Sciences

Water-soluble organic carbon (WSOC), waterinsoluble particulate organic carbon (WIOC), and particulate elemental carbon (EC) were measured simultaneously for the first time on the Greenland Ice Sheet in surface snow and in a 3-meter snow pit. Snow pit concentrations reveal that, on average, WSOC makes up the majority (89%) of carbonaceous species, followed by WIOC (10%) and EC (1%). The enhancement of OC relative to EC (ratio 99:1) in Greenland snow suggests that, along with atmospheric particulate matter, gaseous organics contribute to snow-phase OC. Comparison of summer surface snow concentrations in 2006 with past summer snow pit layers (2002 – 2005) …

Impact Of Multiscale Dynamical Processes And Mixing On The Chemical Composition Of The Upper Troposphere And Lower Stratosphere During The Intercontinental Chemical Transport Experiment–North America, T D. Fairlie, Melody A. Avery, R B. Pierce, J Al-Saadi, Jack E. Dibb, G W. Sachse

Earth Sciences

We use high-frequency in situ observations made from the DC8 to examine fine-scale tracer structure and correlations observed in the upper troposphere and lower stratosphere during INTEX-NA. Two flights of the NASA DC-8 are compared and contrasted. Chemical data from the DC-8 flight on 18 July show evidence for interleaving and mixing of polluted and stratospheric air masses in the vicinity of the subtropical jet in the upper troposphere, while on 2 August the DC-8 flew through a polluted upper troposphere and a lowermost stratosphere that showed evidence of an intrusion of polluted air. We compare data from both flights …

An Overview Of Snow Photochemistry: Evidence, Mechanisms And Impacts, A M. Grannas, A E. Jones, Jack E. Dibb, M Ammann, Cort Anastasio, H J. Beine, M Bergin, J Bottenheim, C S. Boxe, G Carver, G Chen, J H. Crawford, Florent Domine, M M. Frey, M I. Guzman, D E. Heard, D Helmig, M R. Hoffmann, R E. Honrath, L Gregory Huey, Manuel Hutterli, H W. Jacobi, P Klan, Barry Lefer, J Mcconnell, J Plane, R Sander, J Savarino, P B. Shepson, W R. Simpson, J R. Sodeau, R Von Glasow, R Weller, E W. Wolff, T Zhu

Earth Sciences

It has been shown that sunlit snow and ice plays an important role in processing atmospheric species. Photochemical production of a variety of chemicals has recently been reported to occur in snow/ice and the release of these photochemically generated species may significantly impact the chemistry of the overlying atmosphere. Nitrogen oxide and oxidant precursor fluxes have been measured in a number of snow covered environments, where in some cases the emissions significantly impact the overlying boundary layer. For example, photochemical ozone production (such as that occurring in polluted mid-latitudes) of 3-4 ppbv/day has been observed at South Pole, due to …

Mesosphere And Lower Thermosphere Neutral Winds Observations Using Rocket-Released Chemical Trails At Poker Flat, Alaska, Tianyu Zhan

All Dissertations

Sounding rocket campaigns ARIA I through ARIA IV, CODA 2, HEX 1, JOULE 1 and JOULE 2 all carried out at Poker Flat Research Range at Alaska, covering the geomagnetic condition from quiet to highly disturbed. Trimethyl aluminum (TMA) were released during the rocket flights to study the mesosphere and lower thermosphere neutral wind at high-latitude region. The results of horizontal neutral wind profiles are presented. The comparison shows that under disturbed condition the wind velocity is stronger and the jet feature at the bottom side of wind maximum with unstable wind shear is lifted to a higher altitude. Under …

Multimodel Projections Of Stratospheric Ozone In The 21st Century, V. Eyring, D. W. Waugh, G. E. Bodeker, Eugene C. Cordero, H. Akiyoshi, J. Austin, S. R. Beagley, B. A. Boville, P. Braesicke, C. Brühl, N. Butchart, M. P. Chipperfield, M. Dameris, R. Deckert, M. Deushi, S. M. Frith, R. R. Garcia, A. Gettelman, M. A. Giorgetta, D. E. Kinnison, E. Mancini, E. Manzini, D. R. Marsh, S. Matthes, T. Nagashima, P. A. Newman, J. E. Nielsen, S. Pawson, G. Pitari, D. A. Plummer, E. Rozanov, M. Schraner, J. F. Scinocca, K. Semeniuk, T. G. Shepherd, K. Shibata, B. Steil, R. S. Stolarski, W. Tian, M. Yoshiki

Faculty Publications, Meteorology and Climate Science

[1] Simulations from eleven coupled chemistry-climate models (CCMs) employing nearly identical forcings have been used to project the evolution of stratospheric ozone throughout the 21st century. The model-to-model agreement in projected temperature trends is good, and all CCMs predict continued, global mean cooling of the stratosphere over the next 5 decades, increasing from around 0.25 K/decade at 50 hPa to around 1 K/decade at 1 hPa under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario. In general, the simulated ozone evolution is mainly determined by decreases in halogen concentrations and continued cooling of …

Droughtscape, Summer 2007, National Drought Mitigation Center

DroughtScape: Quarterly Newsletter of the National Drought Mitigation Center (2007–2023)

Summer 07 Outlook

Hayes Named Director of NDMC

NDMC & UN Plan for Drought

Book Review: The Worst Hard Time

Drought Tools Workshops Underway

U.S. Drought Monitor Forum October 10-11, 2007 Portland, Oregon

Climate. Stern Review: The Economics Of Climate Change, Nicholas Stern

New England Journal of Public Policy

This chapter examines the increasingly serious impacts on people as the world warms. Climate change is a serious and urgent issue. The Earth has already warmed by 0.7°C since around 1900 and is committed to further warming over coming decades simply due to past emissions. On current trends, average global temperatures could rise by 2–3°C within the next fifty years or so, with several degrees more in the pipeline by the end of the century if emissions continue to grow. This chapter examines how the physical changes in climate . . . affect the essential components of lives and livelihoods …

Climate. Scrubbing The Sky: Climate Change And The Productive Center, Marcy Murninghan

New England Journal of Public Policy

This article sketches out the efforts of government, business, and civil society to address the problem of climate change. It identifies some of the key initiatives underway — including proposals for more stringent caps on greenhouse gas (GHG) emissions; the creation of a market-based trading system that provides incentives and profits for entities that reduce their GHG emission levels; more robust research and development of alternative energy sources as well as new approaches to traditional ones; and continued public education — and portrays the bipartisan, collaborative, multilateral nature of saving Mother Nature. While acknowledging that ultimately these efforts may be …

A Global Mhd Simulation Of An Event With A Quasi-Steady Northward Imf Component, V G. Merkin, J G. Lyon, B J. Anderson, H Korth, C C. Goodrich, K Papadopoulos

Dartmouth Scholarship

We show results of the Lyon-Fedder-Mobarry (LFM) global MHD simulations of an event previously ex- amined using Iridium spacecraft observations as well as DMSP and IMAGE FUV data. The event is chosen for the steady northward IMF sustained over a three-hour pe- riod during 16 July 2000. The Iridium observations showed very weak or absent Region 2 currents in the ionosphere, which makes the event favorable for global MHD model- ing. Here we are interested in examining the model’s per- formace during weak magnetospheric forcing, in particular, its ability to reproduce gross signatures of the ionospheric currents and convection pattern …

Chemical Data Assimilation Estimates Of Continental U.S. Ozone And Nitrogen Budgets During The Intercontinental Chemical Transport Experiment-North America, R B. Pierce, T Schaack, J Al-Saadi, T D. Fairlie, Chieko Kittaka, Gretchen Lingenfelser, M Natarajan, J R. Olson, Amber Soja, Tom Zapotocny, A Lenzen, M A. Avery, James Stobie, Donald Johnson, Melody A. Avery, G W. Sachse, A M. Thompson, Ronald C. Cohen, Jack E. Dibb, J Crawford, Didier Rault, Randall Martin, Jim Szykman, Jack Fishman

Earth Sciences

Global ozone analyses, based on assimilation of stratospheric profile and ozone column measurements, and NOy predictions from the Real-time Air Quality Modeling System (RAQMS) are used to estimate the ozone and NOy budget over the continental United States during the July-August 2004 Intercontinental Chemical Transport Experiment-North America (INTEX-A). Comparison with aircraft, satellite, surface, and ozonesonde measurements collected during INTEX-A show that RAQMS captures the main features of the global and continental U.S. distribution of tropospheric ozone, carbon monoxide, and NOy with reasonable fidelity. Assimilation of stratospheric profile and column ozone measurements is shown to have a positive impact on the …

Improving Regional Ozone Modeling Through Systematic Evaluation Of Errors Using The Aircraft Observations During The International Consortium For Atmospheric Research On Transport And Transformation, M Mena-Carrasco, Youhua Tang, Gregory R. Carmichael, Tianfeng Chai, Narisara Thongbongchoo, J Elliott Campbell, S Kulkarni, Larry Horowitz, Jeffrey Vukovich, Melody A. Avery, William H. Brune, Jack E. Dibb, L K. Emmons, F Flocke, Glen Sachse, David Tan, R E. Shetter, R. Talbot, David G. Streets, D R. Blake

Earth Sciences

During the operational phase of the ICARTT field experiment in 2004, the regional air quality model STEM showed a strong positive surface bias and a negative upper troposphere bias (compared to observed DC-8 and WP-3 observations) with respect to ozone. After updating emissions from NEI 1999 to NEI 2001 (with a 2004 large point sources inventory update), and modifying boundary conditions, low-level model bias decreases from 11.21 to 1.45 ppbv for the NASA DC-8 observations and from 8.26 to −0.34 for the NOAA WP-3. Improvements in boundary conditions provided by global models decrease the upper troposphere negative ozone bias, while …

Reactive Nitrogen Distribution And Partitioning In The North American Troposphere And Lowermost Stratosphere, H B. Singh, L Salas, D Herlth, R Koyler, M A. Avery, J H. Crawford, R B. Pierce, Glen Sachse, D R. Blake, Ronald C. Cohen, T H. Bertram, A E. Perring, Paul J. Wooldridge, Jack E. Dibb, L Gregory Huey, R C. Hudman, S Turquety, L K. Emmons, F Flocke, Youhua Tang, Gregory R. Carmichael, Larry Horowitz

Earth Sciences

A comprehensive group of reactive nitrogen species (NO, NO₂, HNO₃, HO₂NO₂, PANs, alkyl nitrates, and aerosol-NO₃⁻) were measured over North America during July/August 2004 from the NASA DC-8 platform (0.1–12 km). Nitrogen containing tracers of biomass combustion (HCN and CH₃CN) were also measured along with a host of other gaseous (CO, VOC, OVOC, halocarbon) and aerosol tracers. Clean background air as well as air with influences from biogenic emissions, anthropogenic pollution, biomass combustion, convection, lightning, and the stratosphere was sampled over the continental United States, the Atlantic, …

Summertime Influence Of Asian Pollution In The Free Troposphere Over North America, Q Liang, L Jaegle, R C. Hudman, S Turquety, D J. Jacob, Melody A. Avery, E V. Browell, G W. Sachse, D R. Blake, William H. Brune, Xinrong Ren, Ronald C. Cohen, Jack E. Dibb, A Fried, H Fuelberg, M Porter, B J. Heikes, Greg Huey, H B. Singh, Paul Wennberg

Earth Sciences

We analyze aircraft observations obtained during INTEX-A (1 July to 14 August 2004) to examine the summertime influence of Asian pollution in the free troposphere over North America. By applying correlation analysis and principal component analysis (PCA) to the observations between 6 and 12 km, we find dominant influences from recent convection and lightning (13% of observations), Asia (7%), the lower stratosphere (7%), and boreal forest fires (2%), with the remaining 71% assigned to background. Asian air masses are marked by high levels of CO, O3, HCN, PAN, C2H2, C6H6, methanol, and SO4 2 –. The partitioning of NOy species …

Biomass Burning And Pollution Aerosol Over North America: Organic Components And Their Influence On Spectral Optical Properties And Humidification Response, A D. Clarke, Cameron Mcnaughton, V Kapustin, Yohei Shinozuka, S G. Howell, Jack E. Dibb, J Zhou, B Anderson, V Brekhovskikh, H Turner, M Pinkerton

Earth Sciences

Thermal analysis of aerosol size distributions provided size resolved volatility up to temperatures of 400°C during extensive flights over North America (NA) for the INTEX/ICARTT experiment in summer 2004. Biomass burning and pollution plumes identified from trace gas measurements were evaluated for their aerosol physiochemical and optical signatures. Measurements of soluble ionic mass and refractory black carbon (BC) mass, inferred from light absorption, were combined with volatility to identify organic carbon at 400°C (VolatileOC) and the residual or refractory organic carbon, RefractoryOC. This approach characterized distinct constituent mass fractions present in biomass burning and pollution plumes every 5–10 min. Biomass …

Surface And Lightning Sources Of Nitrogen Oxides Over The United States: Magnitudes, Chemical Evolution, And Outflow, R C. Hudman, D J. Jacob, S Turquety, Eric M. Leibensperger, L T. Murray, S Wu, A B. Gilliland, M A. Avery, T H. Bertram, William H. Brune, Ronald C. Cohen, Jack E. Dibb, F Flocke, A Fried, J S. Holloway, J A. Neuman, R Orville, A E. Perring, Xinrong Ren, G W. Sachse, H B. Singh, Aaron L. Swanson, Paul J. Wooldridge

Earth Sciences

We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution, and export of NOx. The boundary layer NOx data provide top-down verification of a 50% decrease in power plant and industry NOx emissions over the eastern United States between 1999 and 2004. Observed NOx concentrations at 8–12 km altitude were 0.55 ± 0.36 ppbv, much larger than in previous U.S. aircraft campaigns (ELCHEM, SUCCESS, SONEX) though consistent with data from …

Numerical Modeling Of A Gravity Wave Packet Ducted By The Thermal Structure Of The Atmosphere, Yonghui Yu, Michael P. Hickey Ph.D.

Publications

A time-dependent and fully nonlinear numerical model is employed to solve the Navier-Stokes equations in two spatial dimensions and to describe the propagation of a Gaussian gravity wave packet generated in the troposphere. A Fourier spectral analysis is used to analyze the frequency power spectra of the wave packet, which propagates through and dwells within several thermal ducting regions. The frequency power spectra of the wave packet are derived at several discrete altitudes, which allow us to determine the evolution of the packet. This spectral analysis also clearly reveals the existence of a stratospheric duct, a mesospheric and lower thermospheric …

Simulated Ducting Of High-Frequency Atmospheric Gravity Waves In The Presence Of Background Winds, Yonghui Yu, Michael P. Hickey Ph.D.

Publications

A new nonlinear and time-dependent model is used to derive the total perturbation energy flux of two gravity wave packets propagating from the troposphere to the lower thermosphere. They are excited by a heat source and respectively propagate in an eastward and westward direction in the presence of a zonal wind. Analysis of the refractive index, the power spectra and the total perturbation energy flux allows us to correctly interpret the ducting characteristics of these two wave packets. In our study the wind acts as a directional filter to the wave propagations and causes noticeable spectral variations at higher altitudes. …

Influence Of Lateral And Top Boundary Conditions On Regional Air Quality Prediction: A Multiscale Study Coupling Regional And Global Chemical Transport Models, Youhua Tang, Gregory R. Carmichael, Narisara Thongbongchoo, Tianfeng Chai, Larry Horowitz, R B. Pierce, J Al-Saadi, G G. Pfister, Jeffrey Vukovich, Melody A. Avery, Glen Sachse, Thomas B. Ryerson, J S. Holloway, E L. Atlas, F Flocke, Rodney J. Weber, L Gregory Huey, Jack E. Dibb, David G. Streets, William H. Brune

Earth Sciences

The sensitivity of regional air quality model to various lateral and top boundary conditions is studied at 2 scales: a 60 km domain covering the whole USA and a 12 km domain over northeastern USA. Three global models (MOZART-NCAR, MOZART-GFDL and RAQMS) are used to drive the STEM-2K3 regional model with time-varied lateral and top boundary conditions (BCs). The regional simulations with different global BCs are examined using ICARTT aircraft measurements performed in the summer of 2004, and the simulations are shown to be sensitive to the boundary conditions from the global models, especially for relatively long-lived species, like CO …

Droughtscape, Spring 2007, National Drought Mitigation Center

DroughtScape: Quarterly Newsletter of the National Drought Mitigation Center (2007–2023)

2007 Spring Drought Outlook & Winter Summary

VegDRI Expands to 15 States, Refines Views

DroughtScape

State Spotlight: Utah

International Panel Foresees Drought as Part of Climate Change

NIDIS Portal Advancing

Doppler Ducting Of Short-Period Gravity Waves By Midaltitude Tidal Wind Structure, Jonathan B. Snively, Victor P. Pasko, Michael J. Taylor, Wayne K. Hocking

Publications

Multiwavelength airglow image data depicting a short-period (∼4.9 min) atmospheric gravity wave characterized by a sharp leading front have been analyzed together with synoptic meteor radar wind data recorded simultaneously from Bear Lake Observatory, Utah (41.6°N, 111.6°W). The wind data suggest the presence of a semidiurnal tide with horizontal winds peaking at around 60 m/s along the SSE direction of motion (170° from north) of this short-period wave. It was found that the gravity wave was most probably ducted because of the Doppler shift imposed by this wind structure. A marked 180° phase shift was observed between the near-infrared OH …

Holes: Ionospheric Scintillation, Gps And Imputation, Robert A. Steenburgh

Theses and Dissertations

Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within ± 20 degrees of the geomagnetic equator. This belt also hosted roughly half of the completed U.S. military operations in the last decade. The authors examined scintillation data from Ascension Island, United Kingdom, and Ancon, Peru, in the Atlantic longitudinal sector as well as data from Parepare, Indonesia, and Marak Parak, Malaysia, in the Pacific longitudinal sector. From these data, they calculate percent probability of occurrence …

Assessment Of The Impact Of Various Ionospheric Models On High Frequency Signal Raytracing, Joshua T. Werner

Theses and Dissertations

An assessment of the impact of various ionospheric models on high-frequency (HF) signal raytracing is presented. Ionospheric refraction can strongly affect the propagation of HF signals. Consequently, Department of Defense missions such as over-the-horizon RADAR, HF communications, and geo-location all depend on an accurate specification of the ionosphere. Five case studies explore ionospheric conditions ranging from quiet conditions to solar flares and geomagnetic storms. It is shown that an E layer by itself can increase an HF signal’s ground range by over 100 km, stressing the importance of accurately specifying the lower ionosphere. It is also shown that the GPSII …