EOS115 midterm 1

Storms–2 Types
–>Mid-Latitude systems (winter, ‘low pressure systems’)
–>Tropical Systems (tropical storm, hurricane)
Tropical Storms
Start as collection of T-Storms, grow from positive feedback
How do thunderstorms form?
Warm, moist air parcel rises and grows thru positive feedback. (see notes for specifics)
vortex formation
centrifigul “force” pushes air out, low pressure gradient is pushing in, eventually equilibrium forms and the vortex is formed (eg. whirlpool, tornado, hurrican eye)
Cyclonic Circulation (why c.c. in northern hemisphere?)
Coriolis effect–playing catch on a merry go round example
Storm Surge (2 causes)
Low Pressure (sucked up under low pressure of storm), Wind Drag (water blown ashore)
Storm surge from wind drag–circulation cause
wind drag only affects the surface, pressure gradient forms with depth and forces water out to sea in the deeper sections
Storm Surge Effects
waves reaching much further–destruction thru erosion
Land and Sea Breezes (cause)
Heat capacity of earth vs. water, warmer air rises en masse and causes pressure gradient on the surface
Ocean Waves (causes)
Landslides, earthquakes, moon/sun (tide), WIND
Wind Wave Formation
Starts as ripple, grows as it goes through combining with others
Waves (how they work)
Variations in horiz. velocity lead to stretching and squeezing which causes height changes (see notes…)
Water parcel path within wave
orbital/circular
Wave effects with depth
pressure gradient, velocity, and acceleration reduced with depth
Propagation velocity (definition)
velocity of “hill” through water
Propagation velocity with relation to wavelength
longer wavelength=faster propagation
Linear Theory (waves)
Sinsusoidal shape, circular (and closed) orbits, perfect ‘superposition’
Actual Waves (rather than linear theory)
Complex shapes; not closed orbits of parcels (wave drift…increases with wave height)
Superposition
Sum of many different waves can create any shape. Ocean waves combine to create irregular wave surface. Often leads to surfers ‘sets’.
Waves entering shallow water…
Wavelength decreases, height increases, speed decreases.
Waves Breaking (2 types)
Spilling (front wave edge is ‘too steep’, water falls down) and Plunging (wave crest is ‘too fast’ and falls off the front, creating pipes)
Wave Refraction
Waves coming near shore at some angle are bent (or ‘refracted’) toward the shore.
Shoaling/refraction vs. wavelength
Larger effects on longer period waves (larger swing from fast to slow, all waves same speed at low depth)
Wave-Driven Currents
Water parcels pushed along in front of wave (‘surf’ the wave), pile water onshore much like storm surge
Storm Erosion
Storm surge circulation goes out at depth, where more sediment is concentrated. This caries out sediment to the edge of the surf zone (sand bar formation, positive feedback)
Post-Storm recovery
Waves alone (with no currents) tend to sweep sand onshore. The water moves fastest at the crests (onshore direction) and sand motion is sensitive to velocity (higher velocity has proportionally higher effects).
Storm Erosion Cycle
During surge, sand is carried out due to pressure gradient. After storm, waves alone are acting on the sand and the beach is rebuilt (finds equilibrium with gravity)…..(see notes)
Rip Currents
One area along beach loses wave power, water rushes out. This often forms rip channel in the sand, perpetuating the effects