Publications
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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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 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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Comparison of the performance of the Integrated Terminal Weather System (ITWS) and Terminal Doppler Weather Radar (TDWR) microburst detection algorithms
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and a common set of truth criteria. Examples are presented illustrating common scenarios which create the performance differences. Detail is presented on the impact of the ITWS VIL (Vertically Integrated Liquid water) test in reducing algorithm false alarms. This algorithm feature is currently being considered as a retrofit to the TDWR algorithm.
Summary
This paper describes the designs of the TDWR and ITWS Microburst Detection algorithms, and compares their performances in the Orlando, FL and Memphis, TN environments. This is the first study in which the performance of the TDWR and ITWS microburst detection algorithms are compared using an identical data set and...
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A comparison of the performance of two gust front detection algorithms using a length-based scoring technique
May 8, 1992
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-185
Summary
The Terminal Doppler Weather Radar (TDWR) Gust Front Algorithm provides, as products, estimates of the current locations of gust fronts, their future locations, the wind speed and sirection behind the gust fronts, and the wind shear hazard to landing or departing aircraft. These products are used by air traffic controllers and supervisors to warn pilots of potentially hazardous wind shears during take-off and landing and to plan runway reconfigurations. Until recently, an event-based scoring system was used to evaluate the performance of the algorithm. With the event-based scoring scheme, if any part of a gust front length was detected, a valid detection was declared. Unfortunately, this scheme gave no indication of how much of the gust front length was detected; nor could the probabilities be easily related to the probability of issuing a wind shear alert for a specific approach or departure path which was being impacted by a gust front. To make the scoring metric more nearly reflect the operational use of the product, a new length-based scoring scheme was devised. This scheme computes the length of the gust front detected by the algorithm. When computed over a large number of gust fronts, this length-based scoring scheme yields the probability that any part of the gust front will be detected. As improvements to the algorithm increase the length detected, the probability of detecting any part of a gust front increases. In particular, an improved algorithm means an increased probability of correctly issuing wind shear alerts for the runways impacted by a gust front, and length-based scoring is a more accurate technique for assessing this probability of detection. This paper describes the length-based scoring scheme and compares it with event-based scoring of the algorithm's gust front detection and forecast performance. The comparison of the scoring methods shows that recent enhancements to the gust front algorithm provide a substantial, positive impact on performance.
Summary
The Terminal Doppler Weather Radar (TDWR) Gust Front Algorithm provides, as products, estimates of the current locations of gust fronts, their future locations, the wind speed and sirection behind the gust fronts, and the wind shear hazard to landing or departing aircraft. These products are used by air traffic controllers...
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Characteristics of gust fronts
July 1, 1991
Conference Paper
Published in:
Fourth Int. Conf. on Aviation Weather Systems, 24-28 June 1991, pp. 387-392.
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Summary
A gust front is the leading edge of a thunderstorm outflow. A gust frontal passage is typically characterized by a drop in temperature, a rise in relative humidity and pressure, and an increase in wind speed and gustiness. Gust front detection is of concern for both Terminal Doppler Weather Radar (TDWR) and Next Generation Weather Radar (NEXRAD) systems. In addition, airborne systems using radar, lidar, and infrared sensors to detect hazardous wind shears are being developed. The automatic detection of gust fronts is desirable in the airport terminal environment so that warnings of potentially hazardous gust front-related wind shears can be delivered to arriving and departing pilots. Information about estimated time of arrival and accompanying wind shifts can be used by an Air Traffic Control (ATC) supervisor to plan runway changes. Information on expected wind shifts and runway changes is also important for terminal capacity programs such as Terminal Air Traffic Control Automation (TATCA) and wake vortex advisory systems. In addition, the convergence associated with gust fronts is often a factor in thunderstorm initiation and intensification. Knowledge of gust front locations, strengths, and movement can aid forecasters with thunderstorm-specific predictions. Current gust front detection systems generally are reliable in that the probability of false alarms is low. However the probability of detecting gust fronts with these systems is less than desired. Improved characterization of gust fronts is a key element in improving detection capability. Typically, the basic products from the algorithms are the location of the gust front (for hazard assessment) and its propagation characteristics (for forecasting). This paper discusses the thermodynamic and radar characteristics of gust fronts from three climatic regimes, highlighting regional differences and similarities of gust fronts. It also compares propagation speeds, estimated by two techniques, to measured propagation speeds.
Summary
A gust front is the leading edge of a thunderstorm outflow. A gust frontal passage is typically characterized by a drop in temperature, a rise in relative humidity and pressure, and an increase in wind speed and gustiness. Gust front detection is of concern for both Terminal Doppler Weather Radar...
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Characteristics of thunderstorm-generated low altitude wind shear: a survey based on nationwide Terminal Doppler Weather Radar testbed measurements
December 1, 1990
Conference Paper
Published in:
Proc. 29th IEEE Conf. on Decision and Control, 5-7 December 1990, Vol. 2, pp. 682-688.
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The characteristics of microbursts and gust fronts, two forms of aviation-hazardous low altitude wind shear, are presented. Data were collected with a prototype terminal Doppler weather radar and a network of surface weather stations in Memphis, Huntsville, Denver, Kansas City, and Orlando. Regional differences and features that could be exploited in detection systems such as the associated reflectivity, surface wind shear, and temperature change are emphasized.
Summary
The characteristics of microbursts and gust fronts, two forms of aviation-hazardous low altitude wind shear, are presented. Data were collected with a prototype terminal Doppler weather radar and a network of surface weather stations in Memphis, Huntsville, Denver, Kansas City, and Orlando. Regional differences and features that could be exploited...
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Observed differences between Denver and Kansas City gust fronts and their impact upon the performance of the gust front detection algorithm
October 22, 1990
Conference Paper
Published in:
16th Conf. on Severe Local Storms/Conf. on Atmospheric Electricity, 22-26 October 1990, pp. 236-239.
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Summary
The Terminal Doppler Weather Radar (TDWR) testbed radar (known as FL-2) collected data near Denver's Stapleton Airport during 1988 and near the Kansas City International Airport (MCI) during 1989. One objective of the TDWR Program is to detect gust fronts and their associated wind shifts. This information can be used by an Air Traffic Control (ATC) supervisor to plan runway changes and for warnings of potentially-hazardous gust front-related wind shears to arriving and departing pilots. This function is performed by the gust front detection algorithm. An ongoing assessment of the performance of the current TDWR gust front algorithm is necessary to ensure that the algorithm performs consistently in different environments. Such assessments were performed after the 1988 TDWR Operational Test and Evaluation in Denver and after the 1989 operational season in Kansas City. This paper presents a comparison of gust front characteristics such as length, duration, strength, and propagation speed and direction that occurred in Denver and Kansas City and a comparison of algorithm performance at each location. In the following, the term gust front refers to the leading edge of the thunderstorm outflow throughout its life cycle. A gust front event is a single observation of a gust front (on a radar volume scan) by the National Severe Storms Laboratory (NSSL) ground-truth analyst.
Summary
The Terminal Doppler Weather Radar (TDWR) testbed radar (known as FL-2) collected data near Denver's Stapleton Airport during 1988 and near the Kansas City International Airport (MCI) during 1989. One objective of the TDWR Program is to detect gust fronts and their associated wind shifts. This information can be used...
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Selected wind shear events observed during the 1987 evaluation of enhancements to the FAA low level wind shear alert system at Stapleton International Airport
February 15, 1989
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-158
Summary
The Federal Aviation Administration (FAA) Technical Center (FAATC) conducted a test of the enhancements to the FAA Low Level WInd Shear Alert System (LLWAS) at Denver Stapleton International Airport from 3 August through 4 September 1987. Upon completion of the test, the performance of the LLWAS during selected microburst and gust front test cases was investigated in detail. Additional sources of "true" wind shear information were sought to help evaluate the performance of the LLWAS. In support of these efforts, Lincoln Laboratory supplied complete data sets, including single Doppler radar data from the FAA-Lincoln Laboratory FL-2 radar, dual Doppler radar data from the FAA-Lincoln Laboratory FL-2 radar, dual Doppler analyses of the surface wind fields (when possible), mesonet data from the Lincoln network of 30 automatic weather stations in the vicinity of Stapleton, and LLWAS data to the FAATC. This report provides a summary of salient features for a number of FAATC selected wind shear events which occured during the evaluation of the enhanced LLWAS, and documents the data that Lincoln Laboratory has provided to the FAA as part of its project responsibilities.
Summary
The Federal Aviation Administration (FAA) Technical Center (FAATC) conducted a test of the enhancements to the FAA Low Level WInd Shear Alert System (LLWAS) at Denver Stapleton International Airport from 3 August through 4 September 1987. Upon completion of the test, the performance of the LLWAS during selected microburst and...
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