Storms 2 Flashcards
what is a remote sensor?
an instrument from outside of the storm that can measure the storm
What are some REMOTE sensors that measure storms?
Radar
Satellite
What do radars see?
rain inside storm
up and downdraft stem of mushroom cloud
Using radars, the Disaster Intensity Scale for… indicates …
Radar-Echo Strength (dBZ)
- indicate rainfall rate
What are squall lines?
a line of many thunderstorms
- forms along a cold front
- hail, lots of lightning, possibly tornadoes
Three types of supercells
- Low precipitation
- lots of hail - Classic
- rainy downdraft, rain free updraft - high precipitation
- updraft surrounded by rain
what are mixed mode or hybrid storms?
Contains features of 2 or more types of supercells
Downpours can cause
flash floods
- dBZ scale is extreme
can arc clouds occur at the anvil?
no!
describe thunderstorm diagram
Thunderstorm
|
V arc cloud + warm air
precipitation downburst gust front + haboob
downdraft speeds
20-90 km/h
horizontal wind speeds near ground
up to 250km/h
i.e. outburst
Microbursts
small diameter downbursts
~ 1km
What are downbursts?
cold & dense air sinking
Why do downbursts occur?
Tstorm can create dense air where rain falls
- due to evaporative cooling
Hazards of downbursts
often invisible but a hazard to aircraft
What are Gust Fronts?
leading edge of cold, horizontal, straight-line winds
Why do gust fronts occur?
downburst air hits ground & spreads outward in straight lines, in all directions
What can gust fronts look like?
- haboob = if dry ground
- arc cloud = if moist air
- gustnado
Safety measures
avoid weak buildings & trees that can fall
Arc clouds are along…
gust fronts
What are haboobs
sand storms that occur at edge of gustfronts
What is the fuel for storms?
moist air
Storms can ____ (4 things)
- draw in humid air
- cause air to condense
- release heat into the storm
- result in precipitation & violent winds
Humidity
amount of water vapour in the air
What is the mixing ratio (humidity)
amount of water vapour
÷
amount of all OTHER gases (not including water)
Saturation
the maximum humidity that air can hold
- Equilibrium between Evaporation and Condensation (i.e. the rate matches)
What is important in controlling atmospheric humidity?
saturation value
How does Saturation Mixing Ratio increase with Temperature?
increases exponentially
What air can hold more water vapour at equilibrium, warm or cold?
warmer air!
When it is not cloudy, what does this mean in terms of air and water vapour?
unsaturated
air is holding less water vapour
when it is cloudy or foggy, what does this mean in terms of air and water vapour?
air contains max amount of water vapour (i.e. is saturated)
Advection
movement of air by the wind
ex/ water vapour can be advected into a Tstorm by the wind
Adiabatic cooling
removing heat by evaporating water
when a thermal of unsaturated air rises adiabatically (with no heat transfer to the environment), the thermal cools roughly 10C/km of rise
What process releases latent heat?
condensation
Why does condensation occur?
cooler air can hold less water vapour, so they condense into droplets
i.e. oversaturated!
When the saturation humidity value < actual humidity
What does condensation do? (3 things)
- release latent heat into sensible heat -> make storms warmer
- reduce humidity down to equilibrium (saturation) value
- increase liquid cloud drops, can grow to be rain drops
What is a mesocyclone
A rotating thunderstorm
What is the typical humidity value?
1/ (78+21) ~ 1/99
Most thunderstorms contain how many cells?
2 or more
Multicell thunderstorms
