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San Diego Phenomena

Phenomena in Science Education

Phenomena are the natural and man-made observable events that provide context for the work of scientists and engineers. Recent science standards changed the focus from learning about science to figuring out science. Phenomena are a powerful way to engage students and empower them to wonder and investigate.

Sometimes, we look too hard for the phenomenal events and miss the every-day occurrences that are just as intriguing. The list below is a constant work in progress and will be updated as new submissions are received and new occurrences are observed in and around San Diego County.

Submit a Phenomenon

Did you observe something that made you stop and wonder? Share your phenomena and any supporting material like photographs, videos or additional resources.

Air pollution spikes dramatically in July

Image: LA Times

On July 5, 2018, San Diegans received cell phone notifications warning of poor air quality in San Diego. Similar warnings went out in 2017 and 2016 around the same time.

The graph above from the LA Times was generated using 2017 data from the California Air Resource Board. The graph shows a dramatic jump in air pollution around Los Angeles, and graphs using data collected from air monitoring stations closer to San Diego show a similar spike.

What is the cause and effect relationship behind this pattern? What man-made event is causing this impact on the environment? What are some ways we can reduce this air pollution?


CA.gov, California Air Resource Board

LA Times, Fourth of July brings some of the year's worst pollution

AirNow.gov, California

NGSS & Grade:

MS-ESS3-3, ESS3.C: Human Impacts on Earth Systems

Some rainbows are white

Image: Delinda, Ocean Beach Chronicle

Some rainbows are white and are called white rainbows or fogbows. The image above was captured in May 2018 near Ocean Beach in San Diego.

What do fogbows and rainbows have in common? What is different? What do you think might cause this difference? As the name implies, fogbows are the result of fog. When compared to rain, fog water droplets are much smaller, creating less diffraction and less visible color than rainbows. Fogbows can be completely white or contain faint traces of color. Many of the conditions necessary to create a rainbow, including the position of the sun (or light source), the viewer and the water droplets, are the same as with a fogbow.

Fogbows can be used to bridge physical science and earth science through the crosscutting concepts. 


Ocean Beach Chronicle, White Rainbow aka Fogbow

Popular Science, What the heck are white rainbows, and where do they come from?

Mashable, White rainbows are the phenomenon you've never heard of

NGSS & Grade

4-PS4-2, PS4.B: Electromagnetic Radiation

3-ESS2-1, ESS2.D: Weather and Climate

MS-ESS2-4, ESS2.C: The Roles of Water in Earth's Surface Processes



Rain disappears in mid-air

Image: NWS San Diego

When precipitation occurs, we expect to see and feel it on the ground. However, not all precipitation reaches the ground, and when this happens, we call it virga.

In August 2015, Jason Martinez from News 10 reported on virga in San Diego. Countless others have taken to social media to share rain that seemingly disappears as it falls to the ground. Of course, rain doesn't just disappear, it evaporates, and what we are witnessing is the mid-air evaporation of rain. This phenomenon can serve as an interesting entry-point into the water cycle and local weather.

What causes rain? Where does the rain go if it doesn't hit the ground? Why does virga happen sometimes but not others?


San Diego Union-Tribune, Rain falls on a sunny day

San Diego CBS 8, Matt's MicroClimate Definitions

NGSS & Grade

3-ESS2-1, ESS2.D: Weather and Climate

5-ESS2-1, ESS2.A: Earth Materials and Systems

MS-ESS2-4, MS-ESS2-5, ESS2.C: The Roles of Water in Earth's Surface Processes



Halos form around the Sun


In February 2017, this halo was spotted in San Diego and shared on Twitter. Halos are occasionally observed around the sun and moon. Halos are caused by ice crystals in high-altitude clouds and the appearance of a halo can indicate certain weather patterns.

Are halos like rainbows, and if so, how? What causes a halo to appear around the sun? What does the appearance of a halo tell us about the weather? Are sun halos always the same size?


EarthSky, What makes a halo?

Weather Channel, What are sun halos?

NGSS & Grade

3-ESS2-1, ESS2.D: Weather and Climate

Moon appears larger when closer to the horizon

Image: Moon rise through Downtown San Diego buildings. Craig Carter, @SeeMyPhotos

Like the sun, the moon rises and sets in the sky at predictable times. When the moon is close to the horizon during moon rise or moon set, it appears to be much larger than when it is above us. 

Is the moon larger at certain times of the day? How can we determine if the moon is a different size depending on its position in the sky?


National Geographic, Why the moon looks bigger near the horizon?

Discover Magazine, Why does the moon look so huge on the horizon?

NGSS & Grade

1-ESS1-1, ESS1.A: The Universe and its Stars

5-ESS1-2, ESS1.A: The Universe and Its Stars

MS-ESS1-1, ESS1.A: The Universe and Its Stars

The Catalina Eddy

Image: NASA Earth Observatory

On June 13, 2018, the National Weather Service reported a small but well-defined eddy off the coast near the border of Orange County and San Diego County. An eddy is a counter-clockwise circulation pattern of fog and clouds. The Catalina eddy typically brings cool moist air to the coast. A similar eddy was also reported in 2013 (pictured) by the NASA Earth Observatory.

Why do the clouds take on a whirlpool shape? What causes the Catalina eddy and when does it typically appear?


NASA Earth Observatory: Catalina eddy

San Diego Union Tribune: The beauty of a Catalina eddy

Times of San Diego: Catalina eddy phenomenon spotted off San Diego coast

NGSS & Grade

MS-ESS2-6, ESS2.D: Weather and Climate

Hot air balloons in Temecula float in the sky

Image: Fleet Science Center

Use hot air balloons, like those found in Temecula, to explore weather patterns and properties of air. 


HowStuffWorks: How Hot Air Balloons Work 

Planet-Science: Make a teabag fly

Sciencing: Why does hot air rise and cold air sink?

NGSS & Grade:

5-PS1-1, PS1.A: Structure and Properties of Matter

5-ESS2-1, ESS2.A: Earth Materials and Systems

Scuba divers can breathe under water

Image: PADI

The La Jolla coast is a popular scuba diving destination. How can a scuba tank carry enough air for a diver for such a long period of time? What are the properties of the air in the tank? 


Carolina: Scuba Diving and Gas Laws

NGSS & Grade:

MS-PS1-4, PS1.A: Structure and Properties of Matter

Thousands of leopard sharks gather off the coast of La Jolla

Image: Andy Nosel

Every year, starting in June, thousands of leopard sharks gather off the coast of La Jolla near the Marine Room restaurant. 

Why is this one spot so special? According to Scripps Institution of Oceanography, 97 percent of the sharks are pregnant females.  


KPBS, NPR: Increasing number of Leopard Sharks off La Jolla attracting snorkelers, scientists

NGSS & Grade

3-LS1-1, LS1.B: Growth and Development of Organisms

MS-LS1-4, LS1.B: Growth and Development of Organisms