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Weather of the San Francisco Bay Area 

Bay Model 3D map: important concepts 

Prevailing westerly winds are deflected to the right by coriolis effacts due to the rotation of the earth.

These winds blow water away from the coast, cold deeper waters rise (upwelling) to replace the displaced water.

Winds pick up water vapor from the ocean then blow over colder water where water drops condense forming fog.

Sun warms the central valley causing upward convection.

Air moves from the ocean toward the central  valley bringing fog inland through gaps in coastal topography.

Microclimates in San Francisco  an Exploratorium Video

Cloud drop formation:

Air temperature drops below the dew point with cloud condensation nuclei present this is well illustrated by the cloud in a bottle Snack. In the snack there is a pressure reduction resulting in cooling.

Cloud in a bottle (Exploratorium snack)

Cloud production by cooling.(NOAA activity) v

This activity also has a second part showing convection using ice and hot water.

Dew Point (UCDavis) Measure the dew point by cooling a can with ice until droplets form on the outside.

Cloud Condensation Nuclei

Coriolis model NOAA

Convection Currents
This model demonstrates convection currents in water, which we can generalize to understand the movement of water vapor in our atmosphere as part of the water cycle. Try this adaptation to really drive the convection: Support your plastic box with two coffee mugs – one filled with hot water, and the other one empty. Add the red food coloring to the hot water side of the box.


Exploring the Exploratorium at the Piers

Look at temperatures of objects in the city using a far infrared thermal camera.
Measure an urban heat island using an infrared thermometer NESTA, infrared thermometers cost about $30 in 2011 from amazon.

Look at the world in the near infrared using acrylite 1146 acrylic filters.  (Little Shop of Physics)

Solar Motion  record the path of the sun across the sky.

Observe cloud motion in a mirror using a nephoscope.

Build a nephoscope

Cloud drop growth model

The aggregation of raindrops and ice crystals can be modelled by floating aluminum circles or squares on the surfacetension of water. They seem to attract as they fallinto each others depressions assembling into clusters. Clusters of two coins are easily disrupted by slight vibration. Larger clusters require larger vibration to disprupt. This is why cloud condensation nuclei speed up the formation of water drops, the hydrophillic nuclei attract water molecules and bind them in place.


Build a thermometer by Eric Muller

Measuring Raindrops a NASA lesson. (Allow rain to fall onto a 1/4 inch thick layer of flour, or to hit light colored card stock.)


Scientific Explorations with Paul Doherty

© 2011

1 April 2011