scholarly journals Improving Lidar Windshear Detection Efficiency by Removal of “Gentle Ramps”

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1539
Author(s):  
Kai Kwong Hon ◽  
Pak Wai Chan
Keyword(s):  
Detection Efficiency ◽  
State Of The Art ◽  
Detection Algorithm ◽  
Doppler Lidar ◽  
Hit Rate ◽  
Glide Path ◽  
The World ◽  
Alerting System ◽  
The Difference ◽  
Hong Kong International Airport

The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world.

scholarly journals Applications of an Infrared Doppler Lidar in Detection of Wind Shear

2008 ◽  
Vol 25 (5) ◽  
pp. 637-655 ◽  
Author(s):  
C. M. Shun ◽  
P. W. Chan
Keyword(s):  
Hong Kong ◽  
Wind Shear ◽  
Spatial And Temporal Variability ◽  
Doppler Lidar ◽  
Glide Path ◽  
Alerting System ◽  
Hong Kong International Airport ◽  
Detection Technologies ◽  
Gust Front ◽  
Glide Paths

Abstract In December 2005, operational wind shear alerting at the Hong Kong International Airport (HKIA) reached an important milestone with the launch of the automatic Lidar (light detection and ranging) Windshear Alerting System (LIWAS). This signifies that the anemometer-based and radar-based wind shear detection technologies deployed worldwide in the twentieth century have been further advanced by the addition of the lidar—a step closer to all-weather coverage. Unlike the microburst and gust front, which have a well-defined coherent vertical structure in the lowest several hundred meters of the atmosphere, terrain-induced wind shear tends to have high spatial and temporal variability. To detect the highly changeable winds to be encountered by the aircraft under terrain-induced wind shear situations, the Hong Kong Observatory devises an innovative glide path scan (GPScan) strategy for the lidar, pointing the laser beam toward the approach and departure glide paths, with the changes in azimuth and elevation angles concerted. The purpose of the GPScans is to derive the headwind profiles and hence the wind shear along the glide paths. Developed based on these GPScans, LIWAS is able to capture about 76% of the wind shear events reported by pilots over the most-used approach corridor under clear-air conditions. During the past two years, further developments of the lidar took place at HKIA, including the use of runway-specific lidar to further enhance the wind shear detection performance.

scholarly journals A performance assessment of the World Wide Lightning Location Network (WWLLN) via comparison with the Canadian Lightning Detection Network (CLDN)

2010 ◽  
Vol 3 (2) ◽  
pp. 1861-1887 ◽  
Author(s):  
D. Abreu ◽  
D. Chandan ◽  
R. H. Holzworth ◽  
K. Strong
Keyword(s):  
Standard Deviation ◽  
World Wide ◽  
Detection Efficiency ◽  
Low Frequency ◽  
High Peak ◽  
Peak Current ◽  
Lightning Detection ◽  
The World ◽  
The Mean ◽  
The Difference

Abstract. The World Wide Lightning Location Network (WWLLN) uses globally-distributed Very Low Frequency (VLF) receivers in order to observe lightning around the globe. Its objective is to locate as many global strokes as possible, with high temporal and spatial (<10 km) accuracy. Since detection is done in the VLF range, signals from high peak current lightning strokes are able to propagate up to ~104 km before being detected by the WWLLN sensors, allowing for receiving stations to be sparsely spaced. Through a comparison with measurements made by the Canadian Lightning Detection Network (CLDN) between May and August 2008 over a 4° latitude by 4° longitude region centered on Toronto, Canada, this study found that WWLLN detection was most sensitive to high peak current lightning strokes. Events were considered shared between the two networks if they fell within 0.5 ms of each other. Using this criterion, 19 128 WWLLN strokes (analyzed using the Stroke_B algorithm) were shared with CLDN lightning strokes, producing a detection efficiency of 2.8%. The peak current threshold for WWLLN detection is found to be ~20 kA, with the detection efficiency increasing to ~70% at peak currents of ±120 kA. The detection efficiency is seen to have a clear diurnal dependence, with a higher detection efficiency at local midnight than at local noon; this is attributed to the difference in the thickness of the ionospheric D-region between night and day. The mean time difference (WWLLN – CLDN) between shared events was −6.44 μs with a standard deviation of 35 μs, and the mean absolute location accuracy was 7.24 km with a standard deviation of 6.34 km. These results are generally consistent with previous comparison studies of the WWLLN with other regional networks around the world. Additional receiver stations are continuously being added to the network, acting to improve this detection efficiency.

scholarly journals An estimate of global glacier volume

2012 ◽  
Vol 6 (5) ◽  
pp. 3647-3666
Author(s):  
A. Grinsted
Keyword(s):  
Scaling Laws ◽  
State Of The Art ◽  
Inventory Data ◽  
Glacier Inventory ◽  
Ice Caps ◽  
Ice Volume ◽  
Scaling Relationships ◽  
Global Ice Volume ◽  
The World ◽  
The Difference

Abstract. I asses the feasibility of multi-variate scaling relationships to estimate glacier volume from glacier inventory data. I calibrate scaling laws against volume observations of optimized towards the purpose of estimating the total global ice volume. This is applied individually to each record in the Randolph Glacier Inventory which is the first globally complete inventory of glaciers and ice caps. I estimate that the total volume of all glaciers in the world is 0.35 ± 0.07 m sea level equivalent. This is substantially less than a recent state-of-the-art estimate. Area volume scaling bias issues for large ice masses, and incomplete inventory data are offered as explanations for the difference.

scholarly journals Aviation Applications of the Pulsed Doppler LIDAR – Experience in Hong Kong

2009 ◽  
Vol 3 (1) ◽  
pp. 138-146 ◽  
Author(s):  
P.W. Chan
Keyword(s):  
Hong Kong ◽  
Power Distribution ◽  
Lidar Data ◽  
Doppler Lidar ◽  
Pulsed Doppler ◽  
Mixing Height ◽  
Wind Retrieval ◽  
Glide Path ◽  
Crucial Information ◽  
Hong Kong International Airport

The Hong Kong Observatory (HKO) introduced a Doppler LIDAR to the Hong Kong International Airport (HKIA) in 2002, the first LIDAR for aviation alerting services in the world. Since then, HKO has developed a number of weather products based on the LIDAR’s velocity and backscatter power data. LIDAR is found to provide crucial information in a wide variety of aviation applications. This paper gives a review of the experience in Hong Kong in the development of aviation-related weather products using the LIDAR data. Applications include: automatic windshear alerting from the HKO-developed glide-path scans, detection of low-level turbulence, 2D wind retrieval for intense convective events from LIDAR-radar dual Doppler analysis, 3D wind retrieval from a single LIDAR for terrain-disrupted airflow, visibility map based on backscatter power distribution in conical scans, and mixing-height monitoring in vertical scans.

scholarly journals A performance assessment of the World Wide Lightning Location Network (WWLLN) via comparison with the Canadian Lightning Detection Network (CLDN)

2010 ◽  
Vol 3 (4) ◽  
pp. 1143-1153 ◽  
Author(s):  
D. Abreu ◽  
D. Chandan ◽  
R. H. Holzworth ◽  
K. Strong
Keyword(s):  
Standard Deviation ◽  
World Wide ◽  
Detection Efficiency ◽  
Low Frequency ◽  
High Peak ◽  
Peak Current ◽  
Lightning Detection ◽  
The World ◽  
The Mean ◽  
The Difference

Abstract. The World Wide Lightning Location Network (WWLLN) uses globally-distributed Very Low Frequency (VLF) receivers in order to observe lightning around the globe. Its objective is to locate as many global lightning strokes as possible, with high temporal and spatial (< 10 km) accuracy. Since detection is done in the VLF range, signals from high peak current lightning strokes are able to propagate up to ~104 km before being detected by the WWLLN sensors, allowing for receiving stations to be sparsely spaced. Through a comparison with measurements made by the Canadian Lightning Detection Network (CLDN) between May and August 2008 over a 4° latitude by 4° longitude region centered on Toronto, Canada, this study found that WWLLN detection was most sensitive to high peak current lightning strokes. Events were considered shared between the two networks if they fell within 0.5 ms of each other. Using this criterion, 19 128 WWLLN strokes (analyzed using the Stroke_B algorithm) were shared with CLDN lightning strokes, producing a detection efficiency of 2.8%. The peak current threshold for WWLLN detection is found to be ~20 kA, with its detection efficiency increasing from 11.3% for peak currents greater than 20 kA to 75.8% for peak currents greater than 120 kA. The detection efficiency is seen to have a clear diurnal dependence, with a higher detection efficiency at local midnight than at local noon; this is attributed to the difference in the thickness of the ionospheric D-region between night and day. The mean time difference (WWLLN − CLDN) between shared events was −6.44 μs with a standard deviation of 35 μs, and the mean absolute location accuracy was 7.24 km with a standard deviation of 6.34 km. These results are generally consistent with previous comparison studies of the WWLLN with other regional networks around the world. Additional receiver stations are continuously being added to the network, acting to improve this detection efficiency.

Inter-country inequality as a dynamic process and the problem of post-industrial development

2018 ◽  
pp. 5-29 ◽  
Author(s):  
L. M. Grigoryev ◽  
V. A. Pavlyushina
Keyword(s):  
Economic Growth ◽  
Political Institutions ◽  
Industrial Development ◽  
Modern World ◽  
New Approach ◽  
Development Level ◽  
The World ◽  
Long Time ◽  
The Difference ◽  
Post Industrial

The phenomenon of economic growth is studied by economists and statisticians in various aspects for a long time. Economic theory is devoted to assessing factors of growth in the tradition of R. Solow, R. Barrow, W. Easterly and others. During the last quarter of the century, however, the institutionalists, namely D. North, D. Wallis, B. Weingast as well as D. Acemoglu and J. Robinson, have shown the complexity of the problem of development on the part of socioeconomic and political institutions. As a result, solving the problem of how economic growth affects inequality between countries has proved extremely difficult. The modern world is very diverse in terms of development level, and the article offers a new approach to the formation of the idea of stylized facts using cluster analysis. The existing statistics allows to estimate on a unified basis the level of GDP production by 174 countries of the world for 1992—2016. The article presents a structured picture of the world: the distribution of countries in seven clusters, different in levels of development. During the period under review, there was a strong per capita GDP growth in PPP in the middle of the distribution, poverty in various countries declined markedly. At the same time, in 1992—2016, the difference increased not only between rich and poor groups of countries, but also between clusters.

Speculative Realism and Science Fiction

2017 ◽  
Author(s):  
Brian Willems
Keyword(s):  
Science Fiction ◽  
Identity Formation ◽  
Cormac Mccarthy ◽  
Doris Lessing ◽  
Speculative Realism ◽  
Neil Gaiman ◽  
The World ◽  
The Difference ◽  
Quentin Meillassoux

A human-centred approach to the environment is leading to ecological collapse. One of the ways that speculative realism challenges anthropomorphism is by taking non-human things to be as valid objects of investivation as humans, allowing a more responsible and truthful view of the world to take place. Brian Willems uses a range of science fiction literature that questions anthropomorphism both to develop and challenge this philosophical position. He looks at how nonsense and sense exist together in science fiction, the way in which language is not a guarantee of personhood, the role of vision in relation to identity formation, the difference between metamorphosis and modulation, representations of non-human deaths and the function of plasticity within the Anthropocene. Willems considers the works of Cormac McCarthy, Paolo Bacigalupi, Neil Gaiman, China Miéville, Doris Lessing and Kim Stanley Robinson are considered alongside some of the main figures of speculative materialism including Graham Harman, Quentin Meillassoux and Jane Bennett.

Between High Culture and Low Culture; and also The Difference Between Popular Culture and Folk Culture

2019 ◽  
Vol 7 (8) ◽  
pp. 12
Author(s):  
Kunal Debnath
Keyword(s):  
Popular Culture ◽  
Folk Culture ◽  
Common People ◽  
High Culture ◽  
The World ◽  
The Common ◽  
The Difference ◽  
Low Culture

High culture is a collection of ideologies, beliefs, thoughts, trends, practices and works-- intellectual or creative-- that is intended for refined, cultured and educated elite people. Low culture is the culture of the common people and the mass. Popular culture is something that is always, most importantly, related to everyday average people and their experiences of the world; it is urban, changing and consumeristic in nature. Folk culture is the culture of preindustrial (premarket, precommodity) communities.

L'anglicisme dans la langue française

2019 ◽  
Vol 3 ◽  
pp. 00013
Author(s):  
Danny Susanto
Keyword(s):  
English Language ◽  
Oil Industry ◽  
English Word ◽  
Public Institutions ◽  
Font Size ◽  
The World ◽  
French Speaking ◽  
The Difference ◽  
Definition Of ◽  
Bibliographic Study

<p class="Abstract">The purpose of this study is to analyze the phenomenon known as&nbsp;<span style="font-size: 1rem;">“anglicism”: a loan made to the English language by another language.&nbsp;</span><span style="font-size: 1rem;">Anglicism arose either from the adoption of an English word as a&nbsp;</span><span style="font-size: 1rem;">result of a translation defect despite the existence of an equivalent&nbsp;</span><span style="font-size: 1rem;">term in the language of the speaker, or from a wrong translation, as a&nbsp;</span><span style="font-size: 1rem;">word-by-word translation. Said phenomenon is very common&nbsp;</span><span style="font-size: 1rem;">nowadays and most languages of the world including making use of&nbsp;</span><span style="font-size: 1rem;">some linguistic concepts such as anglicism, neologism, syntax,&nbsp;</span><span style="font-size: 1rem;">morphology etc, this article addresses various aspects related to&nbsp;</span><span style="font-size: 1rem;">Anglicisms in French through a bibliographic study: the definition of&nbsp;</span><span style="font-size: 1rem;">Anglicism, the origin of Anglicisms in French and the current situation,&nbsp;</span><span style="font-size: 1rem;">the areas most affected by Anglicism, the different categories of&nbsp;</span><span style="font-size: 1rem;">Anglicism, the difference between French Anglicism in France and&nbsp;</span><span style="font-size: 1rem;">French-speaking Canada, the attitude of French-speaking society&nbsp;</span><span style="font-size: 1rem;">towards to the Anglicisms and their efforts to stop this phenomenon.&nbsp;</span><span style="font-size: 1rem;">The study shows that the areas affected are, among others, trade,&nbsp;</span><span style="font-size: 1rem;">travel, parliamentary and judicial institutions, sports, rail, industrial&nbsp;</span><span style="font-size: 1rem;">production and most recently film, industrial production, sport, oil industry, information technology,&nbsp;</span><span style="font-size: 1rem;">science and technology. Various initiatives have been implemented either by public institutions or by&nbsp;</span><span style="font-size: 1rem;">individuals who share concerns about the increasingly felt threat of the omnipresence of Anglicism in&nbsp;</span><span style="font-size: 1rem;">everyday life.</span></p>

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