Why Fog Beats Rain Against Ship Lasers

Introduction

For naval laser weapons, fog is often a more serious obstacle than rain even though both are made of water. The reason is not simply how much water is in the air. What matters is how that water is distributed along the beam path. Fog fills the atmosphere with vast numbers of tiny suspended droplets that continuously interact with the laser over its entire route to the target. Rain, by contrast, consists of much larger drops separated by relatively large gaps, allowing much of the beam to travel between them. As a result, a shipboard laser can often retain useful energy through moderate rain, while dense fog can dramatically reduce the power and focus delivered to a target. This difference is one of the most important atmospheric limits on naval directed-energy weapons. [Springer+2Naval Postgraduate School]link.springer.comMicrophysics and Optical Attenuation in FogMicrophysics and Optical Attenuation in Fog - Springer Natureby Q Wang · 2021 · Cited by 17 — For fog/mist conditions, the main a…

Droplet Size and Spacing

The key distinction between fog and rain is the relationship between droplet size and droplet concentration.

Rain contains relatively large drops, typically hundreds or thousands of micrometres across. Although individual raindrops can scatter and absorb laser light, they occupy only a small fraction of the beam’s total path volume. Large regions of air remain unobstructed between drops. A laser therefore experiences intermittent encounters with water rather than continuous interaction. [Wiley Online Library]onlinelibrary.wiley.comWiley Online LibraryPropagating Characteristics of Pulsed Laser in RainSep 7, 2015 — As pulsed laser propagates in rain, the interaction…

Fog behaves differently. It consists of enormous numbers of much smaller droplets suspended throughout the atmosphere. While each droplet contains little water, their combined cross-sectional area is extremely large. For a laser beam, that means there are constantly droplets available to intercept, scatter and redirect energy. Research on atmospheric optical propagation repeatedly identifies fog attenuation as being dominated by droplet scattering in the size range most effective at disrupting common military laser wavelengths. [Springer+2MDPI]link.springer.comMicrophysics and Optical Attenuation in FogMicrophysics and Optical Attenuation in Fog - Springer Natureby Q Wang · 2021 · Cited by 17 — For fog/mist conditions, the main a…

An important consequence is that two atmospheric conditions containing similar total amounts of liquid water can affect a laser very differently. A distribution with many small droplets presents a much larger collective scattering surface than the same water concentrated into fewer large drops. Experimental and modelling work has shown that increased droplet cross-sectional area leads to increased scattering losses. [Elib DLR]elib.dlr.deMarch 18, 2016 — by C Pargmann · 2016 · Cited by 4 — Hence, a droplet distribution with the same total volume but increased cross-section…Published: March 18, 2016

Beam Scattering Along the Path

A naval laser must keep enough energy concentrated on a target for a sufficient dwell time to heat, weaken or destroy it. Fog attacks that requirement at every point along the beam path.

When laser light encounters fog droplets, much of the energy is scattered away from the beam’s original direction. Instead of remaining tightly focused, part of the beam is redirected into surrounding angles. This reduces the intensity that reaches the target and enlarges the spot size at the far end of the engagement. The target therefore receives less energy per unit area, which can significantly lengthen engagement times or reduce effective range. [Springer+2mlml.sjsu.edu]link.springer.comMicrophysics and Optical Attenuation in FogMicrophysics and Optical Attenuation in Fog - Springer Natureby Q Wang · 2021 · Cited by 17 — For fog/mist conditions, the main a…

The effect is cumulative. A beam travelling through a kilometre of fog may interact with droplets continuously along the entire route. Naval and defence research programmes studying high-energy laser propagation specifically identify fog and low clouds as environments that create substantial scattering losses requiring dedicated performance modelling. [Naval Postgraduate School]nps.eduThese effects need to be characterized in terms of descriptive…Read more…

Cloud-propagation studies further illustrate the problem. Clouds and fog are both collections of suspended water droplets, and models of high-energy laser transmission through such environments show that droplet populations can dominate beam degradation and energy loss. [Optica]opg.optica.orgPropagation of high energy lasers through cloudsby A Lawrence · 2020 · Cited by 4 — A model for 10.6 µm high energy laser beam inte…

For ships operating near the ocean surface, the challenge can be even greater because maritime fog often contains higher liquid-water content than many inland fog conditions. Studies of optical propagation in marine environments report stronger scattering effects in marine fog, making it a particularly difficult environment for naval lasers. [ResearchGate]researchgate.netMultiple Scattering in Rain and Fog on Free-Space Optical…The multiple scattering effects of light propagation in rain and…

What Changes in Heavy Rain

This does not mean rain is harmless to laser weapons.

Raindrops still absorb and scatter light, and heavy rainfall can noticeably reduce laser effectiveness. As rainfall intensity increases, attenuation rises and the beam suffers greater distortion. Very heavy rain can therefore shorten engagement range and reduce the energy delivered to a target. [Wiley Online Library]onlinelibrary.wiley.comWiley Online LibraryPropagating Characteristics of Pulsed Laser in RainSep 7, 2015 — As pulsed laser propagates in rain, the interaction…

However, heavy rain usually has to become quite intense before it rivals the optical penalties imposed by dense fog. The reason is again geometric. Even in strong rain, much of the beam’s path remains open air between falling drops. Dense fog creates a more uniform field of scatterers distributed throughout the propagation volume. Consequently, fog often causes severe visibility reduction and laser attenuation at ranges where rain remains manageable. Models comparing optical transmission in rain and fog generally find fog to be the more damaging condition for free-space laser propagation. [ResearchGate+2McMaster University Engineering]researchgate.netMultiple Scattering in Rain and Fog on Free-Space Optical…The multiple scattering effects of light propagation in rain and…

Another practical difference is stability. Rain consists of rapidly moving drops passing through the beam, whereas fog forms a persistent suspended medium. A laser can occasionally benefit from momentary gaps in rainfall. Dense fog provides far fewer such opportunities because the scattering layer is effectively continuous from the laser aperture to the target. [ResearchGate]researchgate.netMultiple Scattering in Rain and Fog on Free-Space Optical…The multiple scattering effects of light propagation in rain and…

Why This Matters for Shipboard Lasers

The fog-versus-rain distinction helps explain why naval laser demonstrations often emphasise atmospheric characterisation rather than raw laser power alone. A more powerful laser cannot fully overcome a propagation environment that continuously scatters energy before it reaches the target. The Navy and other defence organisations therefore invest heavily in modelling maritime atmospheric conditions, including fog, low clouds, aerosols and turbulence, to predict when laser weapons will be effective. [Naval Postgraduate School+2Naval Postgraduate School]nps.eduThe goal is real-time atmospheric characterization to…Read more…

In practical terms, fog is usually the harsher test because it combines three disadvantages:

That combination makes dense fog one of the most challenging natural environments for naval directed-energy weapons, often imposing a greater penalty on beam quality and delivered energy than ordinary rainfall. mlml.sjsu.edu+3Springer+3Naval Postgraduate School [link.springer.com]link.springer.comMicrophysics and Optical Attenuation in FogMicrophysics and Optical Attenuation in Fog - Springer Natureby Q Wang · 2021 · Cited by 17 — For fog/mist conditions, the main a…

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Endnotes

1. Source: link.springer.com
   Title: Microphysics and Optical Attenuation in Fog
   Link: https://link.springer.com/article/10.1007/s10546-021-00675-5
   Source snippet

   Microphysics and Optical Attenuation in Fog - Springer Natureby Q Wang · 2021 · Cited by 17 — For fog/mist conditions, the main a...

2. Source: onlinelibrary.wiley.com
   Link: https://onlinelibrary.wiley.com/doi/10.1155/2015/292905
   Source snippet

   Wiley Online LibraryPropagating Characteristics of Pulsed Laser in RainSep 7, 2015 — As pulsed laser propagates in rain, the interaction...

3. Source: researchgate.net
   Link: https://www.researchgate.net/publication/260327811_Multiple_Scattering_in_Rain_and_Fog_on_Free-Space_Optical_Links
   Source snippet

   Multiple Scattering in Rain and Fog on Free-Space Optical...The multiple scattering effects of light propagation in rain and...

4. Source: mdpi.com
   Link: https://www.mdpi.com/2073-4433/16/2/210
   Source snippet

   Research on the Attenuation Characteristics of LiDAR...by X Yang · 2025 · Cited by 6 — This paper focuses on analyzing the distribution...

5. Source: researchgate.net
   Link: https://www.researchgate.net/publication/367037857_The_Multiple_Scattering_of_Laser_Beam_Propagation_in_Advection_Fog_and_Radiation_Fog
   Source snippet

   (PDF) The Multiple Scattering of Laser Beam Propagation...The characteristics of laser beam scattering in different types of fogs are st...

6. Source: elib.dlr.de
   Link: https://elib.dlr.de/104676/1/2016%20SPIE%20Baltimore%20Manuscript%20Propagation.pdf
   Source snippet

   March 18, 2016 — by C Pargmann · 2016 · Cited by 4 — Hence, a droplet distribution with the same total volume but increased cross-section...

   Published: March 18, 2016

7. Source: mlml.sjsu.edu
   Link: https://mlml.sjsu.edu/2025/04/08/seminar-quantifying-the-impact-of-the-atmospheric-boundary-layer-on-optical-signal-propagation/
   Source snippet

   Quantifying the Impact of the Atmospheric Boundary Layer...8 Apr 2025 — Fog and aerosol particles and molecular constituents along the p...

8. Source: mdpi.com
   Link: https://www.mdpi.com/2073-4433/12/7/918
   Source snippet

   Laser Beam Atmospheric Propagation Modelling for...by T Fahey · 2021 · Cited by 109 — In this paper, the atmospheric radiative transfer...

9. Source: opg.optica.org
   Link: https://opg.optica.org/ao/abstract.cfm?uri=ao-59-33-10207
   Source snippet

   Propagation of high energy lasers through cloudsby A Lawrence · 2020 · Cited by 4 — A model for 10.6 µm high energy laser beam inte...

10. Source: ece.mcmaster.ca
    Link: https://www.ece.mcmaster.ca/~hranilovic/woc/resources/local/spie2000b.pdf
    Source snippet

    McMaster University EngineeringComparison of laser beam propagation at 785 nm and...by II Kim · Cited by 1438 — A modification to the pu...

11. Source: opg.optica.org
    Link: https://opg.optica.org/abstract.cfm?uri=ao-59-33-10207
    Source snippet

    of high energy lasers through cloudsby A Lawrence · 2020 · Cited by 4 — In this section, we present a model for high energy laser propaga...

12. Source: researchgate.net
    Link: https://www.researchgate.net/publication/307435846_Atmospheric_Propagation_of_High-Energy_Laser_Beams
    Source snippet

    (PDF) Atmospheric Propagation of High-Energy Laser BeamsLaser sources are widely used for exploring the atmosphere, in particular, its ga...

13. Source: nps.edu
    Link: https://nps.edu/web/research/-/quantifying-hel-weapon-system-performance-through-a-layer-of-fog-or-low-level-clouds-2018
    Source snippet

    These effects need to be characterized in terms of descriptive...Read more...

14. Source: nps.edu
    Link: https://nps.edu/web/research/-/propagation-of-high-energy-lasers-for-various-wavelengths-power-levels-and-atmospheric-conditions-2018
    Source snippet

    The goal is real-time atmospheric characterization to...Read more...

15. Source: nps.edu
    Link: https://nps.edu/web/nps-video-portal/-/hqcylde62bydsgh0nr54mhcjrrw25nmu
    Source snippet

    d Energy Physics Group at the Naval Postgraduate School developed a laser...

Additional References

1. Source: spiedigitallibrary.org
   Link: https://www.spiedigitallibrary.org/proceedings/Download?downloadType=proceedings+article&isResultClick=True&urlId=10.1117%2F12.2037779
   Source snippet

   Evaluating the Damage process of Dynamic Target by High...the laser energy will be severe attenuation by marine atmosphere dense water m...

2. Source: eureka.patsnap.com
   Title: report atmospheric effects on long range laser power transmission
   Link: https://eureka.patsnap.com/report-atmospheric-effects-on-long-range-laser-power-transmission
   Source snippet

   Effects On Long-Range Laser Power...28 Aug 2025 — Weather conditions dramatically affect transmission [efficiency]({{ 'efficiency/' | relative_url }}), with fog, rain, snow...

3. Source: army.mil
   Title: developing lasers that pierce fog dust to destroy targets
   Link: https://www.army.mil/article/195650/army_developing_lasers_that_pierce_fog_dust_to_destroy_targets
   Source snippet

   Army developing lasers that pierce fog, dust to destroy targets23 Oct 2017 — A lot of people think that high-energy lasers, or HELs, can'...

4. Source: laserwars.net
   Title: navy laser weapons challenges atmosphere fog
   Link: https://www.laserwars.net/p/navy-laser-weapons-challenges-atmosphere-fog
   Source snippet

   Fog of War: The Biggest Challenge for Naval Laser Weapons22 May 2025 — Welcome to the literal fog of war, where high-energy lasers run fa...

   Published: May 2025

5. Source: pubmed.ncbi.nlm.nih.gov
   Link: https://pubmed.ncbi.nlm.nih.gov/33361948/
   Source snippet

   of high energy lasers through cloudsby A Lawrence · 2020 · Cited by 4 — A model for 10.6 µm high energy laser beam interaction with a uni...

6. Source: usna.edu
   Link: https://www.usna.edu/Users/weaprcon/avramov/Lasers.php
   Source snippet

   Research Lasers in maritime environment:: User SitesThe Academy grounds provide a natural maritime environment for our laser beam propag...

7. Source: scholar.afit.edu
   Link: https://scholar.afit.edu/cgi/viewcontent.cgi?article=1774&context=facpub%2F1000
   Source snippet

   Propagation of High Energy Lasers: Thermal...High Energy Laser (HEL) propagation through turbulent atmosphere is examined via numerical...

8. Source: youtube.com
   Title: Can a $1 Laser Stop a Million-Dollar Missile?
   Link: https://www.youtube.com/watch?v=IdGyrTcX-jA
   Source snippet

   Iron Beam In Fog: Can Laser Weapons Work Without Visibility? | WION Podcast - YouTube WION · 1.7K views...

9. Source: scispace.com
   Link: https://scispace.com/pdf/high-energy-laser-propagation-in-various-atmospheric-3h3lb87qng.pdf
   Source snippet

   Absorption occurs when.Read more...

10. Source: defencesciencereview.com.pl
    Title: pdf 216776 135052
    Link: https://www.defencesciencereview.com.pl/pdf-216776-135052?filename=Laser-Based-[Directed-Ener
    Source snippet

    DEFENCE SCIENCE REVIEWby A Karkadakattil · 2026 · Cited by 1 — This review aims to evaluate the current capabilities of laser- based Dire...