Within Sensor Operators
When weather bends radar into UFOs
Temperature inversions and anomalous propagation can put convincing radar blips on a screen without proving an exotic object was present.
On this page
- How radar beams can bend
- Why false tracks can look operationally real
- What investigators need to test ducting
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Introduction
Radar contacts are often treated as some of the strongest evidence in UFO reports because they appear to provide an objective, instrument-based record. However, radar does not observe the atmosphere in a vacuum. Under certain weather conditions, especially temperature inversions and sharp changes in humidity, radar beams can bend far more than expected. This phenomenon, known as radar ducting or anomalous propagation, can create convincing radar targets where no unusual airborne object exists. For investigators examining possible causes of UFO reports, radar ducting is important because it can generate apparently solid tracks, repeated returns and even operational concern among trained personnel without requiring an exotic craft to be present. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear…
Understanding ducting does not mean every radar UFO is explained away. Rather, it shows why radar evidence must be interpreted alongside weather data, other sensors and independent observations before conclusions are drawn. [AARO]aaro.milAAROAARO HomeWelcome to the website for the All-domain Anomaly Resolution Office (AARO). Our team of experts leads the U.S. government's…
How radar beams can bend
Radar systems are designed around assumptions about how radio waves normally travel through the atmosphere. In standard conditions, the beam curves gently because atmospheric density decreases with height. However, strong temperature inversions—where warmer air sits above cooler air—or abrupt moisture changes can alter the atmosphere’s refractive properties and force radar energy to bend downward. In extreme cases, the beam becomes trapped within a layer of air and travels much farther than intended, a condition known as ducting. [American Meteorological Society Journals]journals.ametsoc.orgAmerican Meteorological Society JournalsRadar Beam Tracing Methods Based on Atmospheric…by Y Zeng · 2014 · Cited by 72 — A duct can oc… [Radar Tutorial]radartutorial.euinversion layer.Read more…
When this happens, radar energy that would normally pass harmlessly overhead may strike the ground, hills, buildings or the sea surface and then reflect back to the radar. The system receives a return signal and interprets it as a target at a particular range and position. Yet the apparent target may actually be terrain, distant ships, coastline features or other objects outside the radar’s expected coverage area. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear… [canada]canada.caCanadaAbout Canadian historical weather radarAnomalous Propagation (AP). In the low levels of the atmosphere when a layer of warm air l… Meteorological agencies routinely encounter this problem. Weather radars can display what appear to be rain bands or storm cells even when skies are clear. These false echoes are commonly referred to as anomalous propagation (AP) returns. The same physical mechanism can affect surveillance and air-defence radars. [NOAA]noaa.govNOAAJetStream Max: Anomalous Propagation9 Aug 2023 — False echoes are known as anomalous propagation (AP) - an echo that is not precipita… [National Weather Service]weather.govUsing and Understanding Doppler RadarSometimes though, the atmosphere will cause the beam to superrefract or duct through the atmosphere…
Why false tracks can look operationally real
One reason radar ducting remains relevant to UFO investigations is that the resulting targets do not always resemble obvious glitches. Under the right conditions, false returns can appear persistent, structured and geographically coherent.
Several factors contribute to this:
- The radar receives a genuine signal return. The display is not simply malfunctioning; it is processing reflected energy and producing what appears to be a legitimate contact. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear…
- Targets may appear at significant ranges. Ducting can extend radar coverage far beyond its intended horizon, allowing distant terrain or vessels to generate unexpected contacts. [Radar Tutorial]radartutorial.euinversion layer.Read more…
- Returns can persist for hours. Stable inversion layers often remain in place throughout the night or early morning, causing repeated detections that seem consistent and therefore credible. [Canada]canada.caCanadaAbout Canadian historical weather radarAnomalous Propagation (AP). In the low levels of the atmosphere when a layer of warm air l…
- Operators may see multiple contacts. Historical naval and air-defence literature describes inversion-related clutter, rings and clusters of returns that can resemble organised traffic rather than random noise. [U.S. Naval Institute]usni.orgdont fall radar holeNaval InstituteDon't Fall in the Radar Hole | ProceedingsFalse radar returns such as the bright circular return shown below and known as…
The U.S. Federal Aviation Administration explicitly warns that anomalous propagation can create numerous extraneous blips on radar displays when beams are bent toward the ground. Conversely, upward bending can cause genuine targets to disappear or become harder to detect. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear…
This combination can produce a particularly confusing operational picture: some contacts appear where nothing should be, while real objects may be degraded or absent.
Why UFO cases are especially vulnerable to this explanation
Many radar UFO reports emerge during unusual environmental conditions. Coastal regions, marine environments and areas affected by strong inversions are particularly susceptible to ducting. These are also locations where military and civilian radar systems frequently operate. [ResearchGate]researchgate.netResearchGateMonthly and daily variations of radar anomalous…Most radars of the network will be lo-cated in coastal areas, which could…
A radar operator confronted with unexpected targets faces a genuine observational problem. The display may show contacts behaving consistently enough to justify attention. If visual confirmation is unavailable because of darkness, distance or weather, the radar track itself can become the primary source of information. In later retellings, the phrase “it was on radar” can be interpreted as proof of a physical craft when the original situation was more ambiguous. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear…
Historically, some famous radar-related UFO episodes have prompted later discussions about atmospheric propagation effects, particularly when reports occurred during conditions favourable to temperature inversions. While ducting does not automatically solve every case, it remains one of the first mechanisms investigators examine because it is a documented and recurring source of misleading radar contacts. [U.S. Naval Institute]usni.orgdont fall radar holeNaval InstituteDon't Fall in the Radar Hole | ProceedingsFalse radar returns such as the bright circular return shown below and known as…
What investigators need to test ducting
Determining whether ducting played a role requires more than noting that a radar contact existed. Investigators typically seek environmental and technical evidence capable of confirming or excluding anomalous propagation.
Key questions include:
- Were temperature inversions present at the time of the event?
- Did weather balloon, atmospheric sounding or meteorological data indicate super-refraction or ducting conditions?
- Were the contacts strongest on lower radar elevation angles, where anomalous propagation is most common?
- Did neighbouring radar systems observe the same targets?
- Were there matching visual observations, transponder responses or independent sensor detections?
- Did the targets remain fixed relative to terrain features or coastlines?
- Did the returns disappear as atmospheric conditions changed after sunrise or weather transitions? AMS Conference Management [National Weather Service]weather.govUsing and Understanding Doppler RadarSometimes though, the atmosphere will cause the beam to superrefract or duct through the atmosphere… [National Weather Service]weather.govUsing and Understanding Doppler RadarSometimes though, the atmosphere will cause the beam to superrefract or duct through the atmosphere…
Modern radar networks increasingly use filtering, Doppler processing, moving-target indicators and multi-sensor comparisons to reduce the impact of anomalous propagation. Even so, technical literature continues to describe AP clutter as a significant challenge that requires ongoing detection and mitigation efforts. [American Meteorological Society Journals+2American Meteorological Society Journals]
The main lesson for UFO investigations
Radar evidence can be extremely valuable, but radar is not a direct window onto reality. It is an interpretation of reflected radio energy travelling through a dynamic atmosphere. When temperature inversions or other refractive conditions bend radar beams, the system can generate convincing targets that appear operationally significant despite not representing unusual airborne vehicles. [Federal Aviation Administration]faa.govFederal Aviation Administration Section 5Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear… [Radar Tutorial]radartutorial.euinversion layer.Read more…
For that reason, a radar UFO report becomes most persuasive when the radar data are supported by independent observations and environmental analysis. Without those checks, atmospheric ducting remains a well-established mechanism capable of producing some of the most convincing false UFO targets ever recorded on a radar screen. [NOAA]noaa.govNOAAJetStream Max: Anomalous Propagation9 Aug 2023 — False echoes are known as anomalous propagation (AP) - an echo that is not precipita… [AARO]aaro.milAAROAARO HomeWelcome to the website for the All-domain Anomaly Resolution Office (AARO). Our team of experts leads the U.S. government's…
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Endnotes
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Source: noaa.gov
Link: https://www.noaa.gov/jetstream/anomalous-propagationSource snippet
NOAAJetStream Max: Anomalous Propagation9 Aug 2023 — False echoes are known as anomalous propagation (AP) - an echo that is not precipita...
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Source: [aaro]({{ ‘aaro/’ | relative_url }}). mil
Link: https://www.aaro.mil/Source snippet
AAROAARO HomeWelcome to the website for the All-domain Anomaly Resolution Office (AARO). Our team of experts leads the U.S. government's...
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Source: canada.ca
Link: https://www.canada.ca/en/environment-climate-change/services/weather-general-tools-resources/radar-overview/about.htmlSource snippet
CanadaAbout Canadian historical weather radarAnomalous Propagation (AP). In the low levels of the atmosphere when a layer of warm air l...
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Source: weather.gov
Link: https://www.weather.gov/mkx/using-radarSource snippet
Using and Understanding Doppler RadarSometimes though, the atmosphere will cause the beam to superrefract or duct through the atmosphere...
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Source: weather.gov
Link: https://www.weather.gov/mlb/Doppler_Dual_Pol_Weather_RadarSource snippet
National Weather ServiceNWS Weather RadarAnomalous Propagation (AP) refers to meteorological situations where a signal comes back to the...
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Source: usni.org
Title: dont fall radar hole
Link: https://www.usni.org/magazines/proceedings/1973/december/dont-fall-radar-holeSource snippet
Naval InstituteDon't Fall in the Radar Hole | ProceedingsFalse radar returns such as the bright circular return shown below and known as...
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Source: researchgate.net
Link: https://www.researchgate.net/publication/228809127_Monthly_and_daily_variations_of_radar_anomalous_propagation_conditions_How_normal_is_normal_propagationSource snippet
ResearchGateMonthly and daily variations of radar anomalous...Most radars of the network will be lo-cated in coastal areas, which could...
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Source: researchgate.net
Link: https://www.researchgate.net/publication/249603794_Identification_and_Removal_of_Ground_Echoes_and_Anomalous_Propagation_Using_the_Characteristics_of_Radar_EchoesSource snippet
(PDF) Identification and Removal of Ground Echoes...This paper explores the removal of normal ground echoes (GREs) and anomalous propaga...
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Source: researchgate.net
Link: https://www.researchgate.net/figure/Radar-beam-propagation-conditions-adapted-from-US-NOAA-National-Weather-Service_fig1_224829985Source snippet
To study the phenomenon, the analysis...Read more...
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Source: faa.gov
Title: Federal Aviation Administration Section 5
Link: https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap4_section_5.htmlSource snippet
Surveillance SystemsThe bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to appear...
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Source: journals.ametsoc.org
Link: https://journals.ametsoc.org/view/journals/atot/31/12/jtech-d-13-00152_1.xmlSource snippet
American Meteorological Society JournalsRadar Beam Tracing Methods Based on Atmospheric...by Y Zeng · 2014 · Cited by 72 — A duct can oc...
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Source: radartutorial.eu
Link: https://www.radartutorial.eu/07.waves/wa17.en.htmlSource snippet
inversion layer.Read more...
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Source: journals.ametsoc.org
Title: 1520 0426 1998 015 0098 oioedt 2 0 co 2.xml
Link: https://journals.ametsoc.org/view/journals/atot/15/1/1520-0426_1998_015_0098_oioedt_2_0_co_2.xmlSource snippet
Serious contamination of weather radar data can occur in atmospheric conditions that cause anomalous propagation of the radar beam.Read more...
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Source: faa.gov
Title: Federal Aviation Administration4-5-2
Link: https://www.faa.gov/air_traffic/publications/atpubs/aim/aim0405.htmlSource snippet
Air Traffic Control Radar Beacon System (ATCRBS)8 Jan 2015 — (b) The bending of radar pulses, often called anomalous propagation or ducti...
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Source: journals.ametsoc.org
Title: American Meteorological Society Journals Weather Radar Ground Clutter
Link: https://journals.ametsoc.org/view/journals/atot/26/7/2009jtecha1160_1.pdfSource snippet
Part II - AMS Journalsby JC Hubbert · 2009 · Cited by 227 — The identification and mitigation of anomalous propagation (AP) and normal pr...
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Source: Wikipedia
Title: Anomalous propagation
Link: https://en.wikipedia.org/wiki/Anomalous_propagationSource snippet
Anomalous propagationAnomalous propagation refers to false radar echoes usually observed when calm, stable atmospheric conditions, oft...
Additional References
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Source: faa.gov
Link: https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.1.htmlSource snippet
ENR 1.1: General Rulesb) The bending of radar pulses, often called anomalous propagation or ducting, may cause many extraneous blips to a...
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Source: secjhuapl.edu
Link: https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/V09-N02/09-02-Lee.pdfSource snippet
JHU Applied Physics LabPREDICTING CLUTTER DURING ANOMALOUS...This article describes methods that can be used to predict anomalous clutte...
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Source: wx.erau.edu
Link: https://wx.erau.edu/faculty/mullerb/Wx365/Radar_anomalous_propagation/false_echoes.htmlSource snippet
erau.edufalse_echoesAnomalous propagation of radar echoes refers to meteorological situations where a signal comes back to the radar ante...
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Source: journals.lib.unb.ca
Link: https://journals.lib.unb.ca/index.php/ihr/article/download/26697/1882519457/1882519692Source snippet
PROPAGATION IN RADARSuper-refraction may be caused by (1) a temperature inversion (2) a moisture lapse; (3) a combination of (1) and (2)...
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Source: backend.orbit.dtu.dk
Link: https://backend.orbit.dtu.dk/ws/files/4995451/phd201_thb-net.pdfSource snippet
of Weather Radar ClutterWeather radar clutter, echoes from non-precipitating targets, occur frequently in the data, resulting in lowered...
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Source: theweatherprediction.com
Link: https://www.theweatherprediction.com/habyhints/247/Source snippet
AP and false echoes are one of the biggest enemies of the radar meteorologist. Those without experience in radar...Read more...
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Source: youtube.com
Link: https://www.youtube.com/watch?v=Blf5gfwTtlsSource snippet
RADAR COVERAGE DIAGRAM & DUCT PROPAGATIONRadar Basic such as Anoprop and its effect on radar display. Lecture ends with explanation on ra...
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Source: scispace.com
Title: effects of anomalous propagation conditions on weather radar 2rktpuem1c
Link: https://scispace.com/pdf/effects-of-anomalous-propagation-conditions-on-weather-radar-2rktpuem1c.pdfSource snippet
J Bech · 2012 · Cited by 12 — The effect of atmospheric propagation on rada...
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Source: medium.com
Title: ufos and radar targets clutter safety and false certainty c3eab7a878ad
Link: https://medium.com/%40timventura/ufos-and-radar-targets-clutter-safety-and-false-certainty-c3eab7a878adSource snippet
UFOs and Radar: Targets, Clutter, Safety, and False CertaintyFrom Washington 1952 to the [Nimitz]({{ 'nimitz/' | relative_url }}) encounter, this story explores UFOs, rada...
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Source: altpropulsion.com
Title: ufos and radar targets clutter safety and false certainty
Link: https://www.altpropulsion.com/ufos-and-radar-targets-clutter-safety-and-false-certainty/Source snippet
UFOs and Radar: Targets, Clutter, Safety, and False Certainty30 Mar 2026 — Not whether every UFO is an alien craft, but whether modern ra...
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