Publications
Towards the detection of aircraft icing conditions using operational dual-polarimetric radar
June 25, 2012
Conference Paper
Published in:
7th European Conf. on Radar in Meteorology and Hydrology, ERAD, 25-29 June 2012.
Summary
In anticipation of the dual-polarimetric upgrade to the National Weather Service operational radar network (WSR-88D) research is being conducted to utilize this extensive new data source for remote aircraft icing detection. The first challenge is to accurately locate the melting layer. A new image-processing-based algorithm is proposed and demonstrated. The next challenge is to use the dual-polarimetric data above the melting level to distinguish regions containing super-cooled liquid water, which constitutes an aviation icing hazard, from regions of pure ice and snow. It has been well documented that the S-band dual-polarimetric radar signatures at individual range gates of super-cooled liquid water and ice crystals overlap significantly, complicating the identification of icing conditions using individual radar measurements. Recently several investigators have found that the aggregate characteristics of dual-polarimetric radar measurements over regions on the order of several kilometers show distinguishing features between regions containing super-cooled liquid and those with ice only. In this study, the features found in the literature are evaluated, extended and combined using a fuzzy-logic framework to provide an icing threat likelihood. The results of this new algorithm are computed using data collected in Colorado from the Colorado State University CHILL radar and the National Center for Atmospheric Research S-Pol radar (collectively called FRONT – The Front Range Observational Testbed) collected in the winter of 2010/2011 in coordination with the NASA Icing Remote Sensing System (NIRSS) and compared to pilot reports on approach or departure from nearby airports. The preliminary results look encouraging and will be presented. The ultimate goal is to produce an end-to-end algorithm to produce a reliable icing threat product that can then be combined with existing icing detection systems to improve their performance.
Summary
In anticipation of the dual-polarimetric upgrade to the National Weather Service operational radar network (WSR-88D) research is being conducted to utilize this extensive new data source for remote aircraft icing detection. The first challenge is to accurately locate the melting layer. A new image-processing-based algorithm is proposed and demonstrated. The...
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Dual polarization radar winter storm studies supporting development of NEXRAD-based aviation hazard products
September 29, 2011
Conference Paper
Published in:
35th Conf. on Radar Meteorology, 26-30 September 2011.
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The Next Generation Weather Radar (NEXRAD) dual polarization upgrade has begun adding a functional enhancement to classify hydrometeors. MIT Lincoln Laboratory (LL) develops NEXRAD-based weather radar products for Federal Aviation Administration (FAA) weather systems such as Corridor Integrated Weather System (CIWS), Integrated Terminal Weather System (ITWS), and Weather and Radar Processor (WARP). Without dual polarization, those products are limited to providing information on precipitation location and intensity. With dual polarization, LL is now developing new aviation weather products to determine locations of hydrometeor-based hazards. A product for Icing Hazards Level (IHL) is expected to benefit the FAA. LL has partnered with Valparaiso University (VU) in northern Indiana near Chicago since 2008 to study the evolution of winter storms prior to the NEXRAD dual polarization upgrade. VU contributes to the study a C-band dual polarization weather radar, an on-demand local sounding capability, and a surface winter weather verification team. Additionally, the Wolcott, IN wind profiler is about 70 km south within viewing range of the VU radar, and provides information on the fall speeds of the hydrometeors of interest. This resource-rich location has allowed for substantive study of many winter storm types: synoptic, lake effect, and frontal passages. A key to development of the IHL product is the ability to interpret dual polarization radar signatures from the winter microphysical states and precipitation structures. Evolution of the structures is a response to the microphysical water and ice saturation (sub or super) states. The magnitude of the vertical lift may affect the saturation states. Methods to segregate the radar signatures will be important regarding the inferred presence of a supercooled water icing hazard. The blizzard of Feb. 1 and 2, 2011 produced four distinct precipitation periods (snow, sleet, freezing drizzle, and lake effect snow), all of which will be discussed. The paper and presentation will also detail findings from the study of multiple winter storms and how they inform the development of the IHL product.
Summary
The Next Generation Weather Radar (NEXRAD) dual polarization upgrade has begun adding a functional enhancement to classify hydrometeors. MIT Lincoln Laboratory (LL) develops NEXRAD-based weather radar products for Federal Aviation Administration (FAA) weather systems such as Corridor Integrated Weather System (CIWS), Integrated Terminal Weather System (ITWS), and Weather and Radar...
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The FAA AWRP oceanic weather program development team
January 28, 2006
Conference Paper
Published in:
12th Conf. on Aviation, Range, and Aerospace Meteorology (ARAM), 28 January - 2 February 2006.
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Summary
Remote, oceanic regions have few, if any, high resolution weather products that indicate the current or future locations of aviation hazards such as volcanic ash, convection, turbulence, icing or adverse headwinds. Moreover, oceanic regions present unique challenges due to severely limited data availability, the long duration of transoceanic flights and the difficulty of transmitting critical information into the cockpit. In 2001, the Oceanic Weather Program Development Team (OWPDT; Herzegh et al. 2002) was organized within the Federal Aviation Administration (FAA) Aviation Weather Research Program (AWRP) to focus on resourceful methods for overcoming these limitations through the use of a diverse range of satellite observations, global model results and satellite-based communications. Resulting products focus on the needs of pilots, dispatchers, air traffic managers and forecasters within the oceanic aviation community. The team is a leader in the inflight display of weather products and will continue to develop new displays as products become available.
Summary
Remote, oceanic regions have few, if any, high resolution weather products that indicate the current or future locations of aviation hazards such as volcanic ash, convection, turbulence, icing or adverse headwinds. Moreover, oceanic regions present unique challenges due to severely limited data availability, the long duration of transoceanic flights and...
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The identification and verification of hazardous convective cells over oceans using visible and infrared satellite observations
January 1, 2006
Conference Paper
Published in:
86th AMS Ann. Mtg., 1st Symposium on Policy Research, 2006.
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Three algorithms based on geostationary visible and infrared (IR) observations, are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The algorithms were developed at the Naval Research Laboratory (NRL), National Center for Atmospheric Research (NCAR), and Aviation Weather Center (AWC). The performance of the algorithms in detecting potentially hazardous cells is determined through verification based upon data from National Aeronautical and Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM) satellite observations of lightning and radar reflectivity, which provide internal information about the convective cells. The probability of detection of hazardous cells using the satellite algorithms can exceed 90% when lightning is used as a criterion for hazard, but the false alarm ratio with all three algorithms is consistently large (~40%), thereby exaggerating the presence of hazardous conditions. This shortcoming results in part from limitations resulting from the algorithms' dependence upon visible and IR observations, and can be traced to the widespread prevalence of deep cumulonimbi with weak updrafts but without lightning, whose origin is attributed to pronounced departures from non-dilute ascent.
Summary
Three algorithms based on geostationary visible and infrared (IR) observations, are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The algorithms were developed at the Naval Research Laboratory (NRL), National Center for Atmospheric Research (NCAR), and Aviation Weather Center (AWC). The...
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The physical origin of the land-ocean contrast in lightning activity
January 1, 2002
Journal Article
Published in:
Comptes Rendus Physique, Vol. 3, No. 10, 2002, pp. 1277-1292.
Summary
New tests and older ideas are explored to understand the origin of the pronounced contrast in lightning between land and sea. The behavior of islands as miniature continents with variable area supports the traditional thermal hypothesis over the aerosol hypothesis for lightning control. The substantial land-ocean contrast in updraft strength is supported globally by TRMM (Tropical Rainfall Measuring Mission) radar comparisons of mixed phase radar reflectivity. The land-ocean updraft contrast is grossly inconsistent with the land ocean contrast in CAPE (Convective Available Potential Energy), from the standpoint of parcel theory. This inconsistency is resolved by the scaling of buoyant parcel size with cloud base height, as suggested by earlier investigators. Strongly electrified continental convection is then favored by a larger surface Bowen ratio, and by larger, more strongly buoyant boundary layer parcels which more efficiently transform CAPE to kinetic energy of the updraft in the moist stage of conditional instability.
Summary
New tests and older ideas are explored to understand the origin of the pronounced contrast in lightning between land and sea. The behavior of islands as miniature continents with variable area supports the traditional thermal hypothesis over the aerosol hypothesis for lightning control. The substantial land-ocean contrast in updraft strength...
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Positive charge in the stratiform cloud of a mesoscale convective system
January 16, 2001
Journal Article
Published in:
J. Geophys. Res., Vol. 106, No. D1, 16 January 2001, pp. 1157-1163.
Summary
A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The two positive charge regions are the likely sources of six positive cloud-to-ground flashes with large peak currents (>32 kA) that occurred within 60 km of the balloon during its flight. The amount of charge transferred by three of these positive flashes that made Q bursts is calculated in the range of 97-196 C. Flashes of this sort are known to produce sprites and elves in the mesosphere. The positive charge regions in this stratiform cloud are substantially lower than the 10-km altitude commonly assumed for the positive charge in many sprite modeling studies.
Summary
A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The...
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Sprites, elves, and glow discharge tubes
January 1, 2001
Journal Article
Published in:
Phys. Today, Vol. 54, No. 11, November 2001, pp. 41-47.
Summary
In the 1920's, the Scottish physicist C.T.R. Wilson predicted the existence of brief flashes of light above large thunderstorms. Almost 70 years later, Bernard Vonnegut of SUNY Albany realized that evidence for Wilson's then-unconfirmed predictions might appear in video imagery of Earth's upper atmosphere recorded by space-shuttle astronauts. He encouraged NASA's William Boeck and Otha Vaughan to look for evidence. Their search was successful. At the 1990 fall meeting of the American Geophysical Union, Boeck and Vaughan presented evidence for upper-atmosphere flashes. Evidence of a different nature came from the University of Minnesota's John Winckler and his colleagues, who had serendipitously observed a flash in moonless night-time skies over Minnesota in 1989. These early findings inspired two independent field programs to target the new phenomenon. In the summer of 1993, Walter Lyons of FMA Research set up detectors on Yucca Ridge in the foothills of the Rocky Mountains. That same summer, Davis Sentman of the University of Alaska Fairbanks (UAF) sought to record the flashes from an aircraft flying over the Great Plains. Within a day of each other, the two research teams had documented what turned out to be a common phenomenon in the mesosphere. In doing so, they initiated not only a new kind of continental-scale field experiment but also—and more important—a new interdisciplinary area of research.
Summary
In the 1920's, the Scottish physicist C.T.R. Wilson predicted the existence of brief flashes of light above large thunderstorms. Almost 70 years later, Bernard Vonnegut of SUNY Albany realized that evidence for Wilson's then-unconfirmed predictions might appear in video imagery of Earth's upper atmosphere recorded by space-shuttle astronauts. He encouraged...
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Weather sensing and data fusion to improve safety and reduce delays at major west coast airports
November 30, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-290
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The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco (SFO), Seattle (SEA) and Portland, OR (PDX) international airports. A number of visits were made to the various ATC facilities to better understand their weather decision support operational needs. Analyses were made of an incident of lightning strikes to two aircraft at SEA in February 1999, and a prototype terminal winds product was developed for LAX that uses profilers as well as plane reports to update the the National Weather Service (NWS) Rapid Update Cycle (RUC) winds estimates. We found that an augmented ITWS could potentially address safety concerns for triggered lightning strikes and vertical wind shear in winter storms at Portland and Seattle. An augmented ITWS terminal winds product (that uses wind profiler data in addition to the current ITWS sensors) could provide very large delay reductions for LAX and SFO during winter storms as a component of a wake vortex advisory system. This augmented product also could provide significant delay reduction benefits at SEA. The sensors required to obtain the projected benefits at SFO do not exist currently. Portland may warrant additional sensors to address the vertical wind shear problems, and LAX would require additional sensors for a wake vortex advisory system. We recommend near-term experimental measurements at PDX to determine the optimum sensor mix and that an operational evaluation of the prototype augmented ITWS terminal winds product be carried out at LAX to determine if the current sensor mix can meet operational needs. Lightning strike data at SEA and PDX should be analyzed to determine if a proposed triggered lightning predictant is accurate.
Summary
The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco...
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The behavior of total lightning activity in severe Florida thunderstorms
July 1, 1999
Journal Article
Published in:
Atmos. Res., Vol. 51, Nos. 3-4, July 1999, pp. 245-265.
Summary
The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate preceeds the severe weather at the ground by 5-20 min. A distinguishing feature of severe storms is the presence of lightning 'jumps' -- abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds -- wind, hail, tornadoes -- is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity.
Summary
The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier...
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Comparisons of long-term Schumann resonance records in Europe and North America
June 7, 1999
Conference Paper
Published in:
11th Int. Conf. on Atmos. Electr. 7-11 June 1999, pp. 705-708.
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Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This is a unique opportunity, as Schumann resonance stations are scarce and even fewer station have records with 5-6 year durations. The main purpose of this paper is to make comparisons in the SR time series measured simultaneously at the two field sites, thereby providing access to global behavior on the seasonal and interannual time scales. The comparative measurements described here point out distinct differences in the nature of convection in South America and in Africa, and reveal new aspects about the behavior of tropical continental convection on the ENS0 time scale.
Summary
Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This...
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