Mobile Ka-Band Polarimetric Doppler Radar Observations Of Wildfire Smoke Plumes

Remote sensing techniques have been more recently used to study and track wildfire smoke plume structure and evolution; however, knowledge gaps remain due to the limited availability of observational datasets aimed at understanding the fine-scale fire-atmosphere interactions and plume microphysics. In this study, we present a new mobile millimeter-wave (Ka-band) Doppler radar system acquired to sample the fine-scale kinematics and microphysical properties of active wildfire smoke plumes from both wildfires and large prescribed fires. Four field deployments were conducted in the fall of 2019 during two wildfires in California and one prescribed burn in Utah. An additional dataset of precipitation observations was obtained prior to the wildfire deployments to compare the Ka-band specific signatures of precipitation and wildfire smoke plumes. Radar parameters investigated in this study include reflectivity, radial velocity, Doppler spectrum width, Differential Reflectivity (ZDR), and copolarized correlation coefficients (HV). Observed radar reflectivity ranged between -15 and 20 dBZ in plume and radial velocity ranged 0 to 16 m s-1. Dual-polarimetric observations revealed that scattering sources within wildfire plumes are primarily nonspherical and oblate shaped targets as indicated by ZDR values measuring above 0 and HV values below 0.8 within the plume. Doppler spectrum width maxima were located near the updraft core location and were associated with radar reflectivity maxima

Mobile Ka-Band Polarimetric Doppler Radar Observations of Wildfire Smoke Plumes

Remote sensing techniques have been used to study and track wildfire smoke plume structure and evolution; however, knowledge gaps remain because of the limited availability of observational datasets aimed at understanding finescale fire-atmosphere interactions and plume microphysics. Meteorological radars have been used to investigate the evolution of plume rise in time and space, but highly resolved plume observations are limited. In this study, we present a new mobile millimeter-wave (Ka band) Doppler radar system acquired to sample the fine-scale kinematics and microphysical properties of active wildfire smoke plumes from both wildfires and large prescribed fires. Four field deployments were conducted in autumn of 2019 during two wildfires in California and one prescribed burn in Utah. Radar parameters investigated in this study include reflectivity, radial velocity, Doppler spectrum width, differential reflectivity ZDR, and copolarized correlation coefficient rHV. Observed radar reflectivity ranged between 215 and 20 dBZ in plume, and radial velocity ranged from 0 to 16ms21. Dual-polarimetric observations revealed that scattering sources within wildfire plumes are primarily nonspherical and oblate-shaped targets as indicated by ZDR values measuring above 0 and rHV values below 0.8 within the plume. Doppler spectrum width maxima were located near the updraft core region and were associated with radar reflectivity maxima

A characterization of autumn nocturnal migration detected by weather surveillance radars in the northeastern USA

Billions of birds migrate at night over North America each year. However, few studies have described the phenology of these movements, such as magnitudes, directions, and speeds, for more than one migration season and at regional scales. In this study, we characterize density, direction, and speed of nocturnally migrating birds using data from 13 weather surveillance radars in the autumns of 2010 and 2011 in the northeastern USA. After screening radar data to remove precipitation, we applied a recently developed algorithm for characterizing velocity profiles with previously developed methods to document bird migration. Many hourly radar scans contained windborne “contamination,” and these scans also exhibited generally low overall reflectivities. Hourly scans dominated by birds showed nightly and seasonal patterns that differed markedly from those of low reflectivity scans. Bird migration occurred during many nights, but a smaller number of nights with large movements of birds defined regional nocturnal migration. Densities varied by date, time, and location but peaked in the second and third deciles of night during the autumn period when the most birds were migrating. Migration track (the direction to which birds moved) shifted within nights from south-southwesterly to southwesterly during the seasonal migration peaks; this shift was not consistent with a similar shift in wind direction. Migration speeds varied within nights, although not closely with wind speed. Airspeeds increased during the night; groundspeeds were highest between the second and third deciles of night, when the greatest density of birds was migrating. Airspeeds and groundspeeds increased during the fall season, although groundspeeds fluctuated considerably with prevailing winds. Significant positive correlations characterized relationships among bird densities at southern coastal radar stations and northern inland radar stations. The quantitative descriptions of broadscale nocturnal migration patterns presented here will be essential for biological and conservation applications. These descriptions help to define migration phenology in time and space, fill knowledge gaps in avian annual cycles, and are useful for monitoring long-term population trends of migrants. Furthermore, these descriptions will aid in assessing potential risks to migrants, particularly from structures with which birds collide and artificial lighting that disorients migrants.This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://esajournals.onlinelibrary.wiley.com/hub/journal/10.1002/%28ISSN%291939-5582/Keywords: spatio-temporal patterns, BirdCast, quantitative description, nocturnal migration, WSR-88D, radar ornitholog

Complex permittivity and scattering characteristics of forest fire ash particles at microwave and millimetre wave frequencies

The geometric, physical, dynamic and scattering properties of ash particulates resulting from Australian biomass, along with the complex permittivity, have been presented within this dissertation. The rationale behind this work relates to the characterisation of the fundamental scattering properties of ash particulates, with the primary goals being to aid active radar system design and to provide a basic framework for a complex inverse scattering model. The reflectivity coefficient for a volumetrically dispersed medium has been defined by characterising three distinct properties of ash. Firstly, statistical modelling of ash created from various plant and tree species was conducted in order to describe its geometric and material behaviour. Here, similarities between plant and tree species with comparable foliage were noted. Three probability distribution functions (PDF) relating to the projected area, aspect ratio and through thickness dimensions for large ash particles (>0.2mm2) have been mapped. Material investigation has included analysis of the effects of temperature on biomass and the resultant geometric changes this incurs. Furthermore, the effects of natural moisture absorption rates and porosity estimations using measured and micro-computer-tomography (Micro-CT) techniques have been presented. An analysis of the dynamic behaviour of ash particles within a defined volume of space displaying different modes provides the second area of investigation. Particular focus has been given to the ascent and descent phases of the ash particles, with analysis of three dynamic stability modes; namely tumbling, fluttering and chaotic random. Probability distribution functions for orientation and analysis of velocities and Reynolds numbers have been established using video processing techniques. The complex permittivity of ash at both low and high temperatures has been measured. Here, an empirically derived mixing law has been established to theoretically model the complex permittivity of ash. This model also takes into account concentrations of water that may be absorbed by the highly porous material. By applying the knowledge gained from the analysis of ash particles, extensive modelling and measurement work has been carried out to determine their reflectivity. Simulated modelling of the ash has been achieved using a hybrid simulation scheme to accurately implement statistical models over a wide range of frequencies (1-40GHz)

Terrestrial Environment (Climatic) Criteria Guidelines for use in Aerospace Vehicle Development

This document provides guidelines for the terrestrial environment that are specifically applicable in the development of design requirements/specifications for NASA aerospace vehicles, payloads, and associated ground support equipment. The primary geographic areas encompassed are the John F. Kennedy Space Center, FL; Vandenberg AFB, CA; Edwards AFB, CA; Michoud Assembly Facility, New Orleans, LA; John C. Stennis Space Center, MS; Lyndon B. Johnson Space Center, Houston, TX; George C. Marshall Space Flight Center, Huntsville, AL; and the White Sands Missile Range, NM. This document presents the latest available information on the terrestrial environment applicable to the design and operations of aerospace vehicles and supersedes information presented in NASA-HDBK-1001 and TM X-64589, TM X-64757, TM-78118, TM-82473, and TM-4511. Information is included on winds, atmospheric thermodynamic models, radiation, humidity, precipitation, severe weather, sea state, lightning, atmospheric chemistry, seismic criteria, and a model to predict atmospheric dispersion of aerospace engine exhaust cloud rise and growth. In addition, a section has been included to provide information on the general distribution of natural environmental extremes in the conterminous United States, and world-wide, that may be needed to specify design criteria in the transportation of space vehicle subsystems and components. A section on atmospheric attenuation has been added since measurements by sensors on certain Earth orbital experiment missions are influenced by the Earth s atmosphere. There is also a section on mission analysis, prelaunch monitoring, and flight evaluation as related to the terrestrial environment inputs. The information in these guidelines is recommended for use in the development of aerospace vehicle and related equipment design and associated operational criteria, unless otherwise stated in contract work specifications. The terrestrial environmental data in these guidelines are primarily limited to information below 90 km altitude

Federal Register

Daily publication of the U.S. Office of the Federal Register contains rules and regulations, proposed legislation and rule changes, and other notices, including "Presidential proclamations and Executive Orders, Federal agency documents having general applicability and legal effect, documents required to be published by act of Congress, and other Federal agency documents of public interest" (p. ii). Table of Contents starts on page iii

2015 Oklahoma Research Day Full Program

This document contains all abstracts from the 2015 Oklahoma Research Day held at Northeastern State University

Reports to the President

A compilation of annual reports for the 1999-2000 academic year, including a report from the President of the Massachusetts Institute of Technology, as well as reports from the academic and administrative units of the Institute. The reports outline the year's goals, accomplishments, honors and awards, and future plans