METR 1014
Review for the
Final Exam
Reminder: The final is on Thursday, December 14, 2000
from 8:00 a.m. to 10:00 a.m.
If you have questions, I will probably be in my office in the mornings from 10-12 during finals week. I will also have office hours on Wednesday December 13 from 7-9 p.m. If these times don’t work for you, email me to set up an appointment.
The final will be the same format as the three midterm exams, multiple choice and true/false. It will be comprehensive, with probably 80-90% covered on the old exams, and 10-20% new material. Your best bet would be to review your notes and study the old exams. Any topic covered in class is fair game for the final, but I will probably put emphasis on the following topics:
·
The
different gases that make up the atmosphere
·
How
density and pressure changes with height in the atmosphere
·
The
four temperature layers of the atmosphere
·
The
difference between kinetic and potential energy
·
The
three methods of energy transfer
·
How
temperature affects the amount and wavelength of emitted energy
(Stefan-Boltzmann and Wien’s Laws)
·
The
cause of the seasons, and how tilt affects the length of a day
·
The
difference between Rayleigh, Mie, and non-selective scattering
·
The
different things radiation can do in the atmosphere (absorption, scattering,
reflection)
·
What
latent and sensible heat are
·
How
temperature varies with altitude and nearness to water
·
What
saturation is
·
How
relative humidity changes with temperature
·
What
the dew point is
·
How
temperature changes when air expands or is compressed
·
What
heterogeneous nucleation is
·
The
different types of condensation on the ground
·
The
four ways air can rise
·
The
different lapse rates and what the lifted condensation level is
·
What
makes air stable or unstable
·
What
an inversion is
·
The
basic types of clouds
·
The
collision-coalescence processes
·
How
ice crystals grow
·
The
different types of precipitation and how they form
·
The
relationship between pressure, temperature, and density (Ideal Gas Law)
·
The
different forces that make up wind (pressure gradient, Coriolis, centripetal,
and friction)
·
The
difference between geostrophic and gradient wind
·
The
wind flow around cyclones and anticyclones
·
How
wind flows in the upper levels of the atmosphere
·
The
basics of the three-cell model
·
El
Niño and La Niña
·
The
types of air masses
·
The
difference between cold, warm, occluded, and stationary fronts
·
The
life cycle of a thunderstorm
·
The
types of severe thunderstorms
·
The
different manifestations of severe weather
·
How,
where, and when tornadoes occur
On homework #5, I had you rate how each TV station
forecasted and hoped you noted how the forecasts got worse over time. Though it was not in your book, I went over
why this occurs. The complex equations
that computers use to forecast the weather are subject to chaos, so a small
difference in initial numbers causes a large difference in the final
result. Since the observations we put
into computer models will never be perfect, the final forecasts will always be
chaotic. Thus forecasts get worse over
time and are usually useless beyond 14 days.
Tropical storms are known by
different names in various parts of the globe.
In the Atlantic and the eastern Pacific ocean, they are known as
hurricanes. Farther west in the Pacific
near Asia, the storms are called typhoons, while in the Indian Ocean and near
Australia they are called cyclones. The
majority of storms occur in the western Pacific, averaging 16 per year. No storms at all occur in the southern
hemisphere Atlantic ocean.
In order for hurricanes to occur,
the ocean temperatures need to be very warm, over 27oC (81oF). Since the storm rotates, the Coriolis force
is necessary to start that rotation, thus the storms cannot form near the
equator. Unstable air over the oceans
without a low trade wind inversion allows thunderstorms to develop. These thunderstorms usually form in
organized groups just upstream of easterly waves. This group of thunderstorms is called a tropical
disturbance. Most tropical disturbances
die, but some begin to have lowering pressures and cyclonic rotation. Once a tropical disturbance has a closed
isobar on an analysis, it becomes a tropical depression. If the tropical depression intensifies and
the maximum sustained surface winds become greater than 37 mph, it reaches
tropical storm status. At this point
the storms gets a name from a designated list.
Once the storm has winds greater than 74 mph, it is classified as a
hurricane.
Hurricanes rotate cyclonically
(counterclockwise in the Northern Hemisphere and clockwise in the Southern
Hemisphere). The very low pressure in
their centers provides a strong pressure gradient and strong winds. Bands of thunderstorms rotate around the
storm, forming spiral rainbands. The
most intense part of the storm is in the eyewall, where the storm has strong
rising air and highest winds. In
contrast, the eye is an area of sinking air in the center of the storm. The sinking air suppresses cloud development
and a clear spot in the middle of the storm develops. The hurricane is powered by the latent heat released when water
vapor condenses into liquid.
Hurricanes, in contrast to mid-latitude low pressure systems, have a
warm core and have the greatest wind speeds at the surface.
Hurricanes in the Atlantic ocean
usually form between June 1 and November 30.
In the early stages the storm moves westward with the trade winds. Once it reaches the tropical storm stage,
the storm is influenced more by the upper level winds and ocean surface
temperatures. Still, the storm usually
moves in a westward direction, turning towards the poles late in its life, but
the paths can be very erratic.
Hurricanes are rated by the strength
of their winds on the Saffir-Simpson scale, from the minimal category 1 to the
catastrophic category 5. Once a
hurricane makes landfall, it is cut off from its supply of latent heat and
begins to die. Still, the storm can
have an enormous effect on land. The
most damaging to lives and property is storm surge, the rise in ocean level due
to winds. The hurricane can also bring
high winds, heavy rain, and spawn tornadoes.
The right side of the storm is the most dangerous (in the Northern
Hemisphere), since the winds rotating around the storm and the direction of
movement act together on that side of the storm instead of opposing each other
like on the left side.
Forecasting for hurricanes in the U.S. is the
responsibility of the National Hurricane Center in Florida. The NHC sends out planes that fly through
the storm and send out dropsondes that measure temperature, pressure, moisture,
and winds. This data, along with data
from buoys and satellites, is input into several different computer models to
forecast the hurricane’s track and intensity.
Like all computer models, the hurricane models become less accurate over
time and are only useful for about 72 hours.
Once the NHC decides that a hurricane is headed towards land, they will
issue a hurricane watch. When the
hurricane comes within 24 hours of reaching land, the NHC will issue a hurricane
warning for a section of the coast. The
warnings are often accompanied by the probability of a direct strike for an
area. The forecasters at NHC must
strike a balance between evacuating areas to save lives and avoiding false
alarms. As more people move to coastal
regions prone to hurricanes, this issue becomes even more important.
Know: