Transcript Main Title - University of Wisconsin–Madison

AOS 101 Weather and Climate
Lisha M. Roubert
University of Wisconsin-Madison
Department of Atmospheric & Oceanic Sciences
Recap of Last Week’s Class-Wisconsin
Climate
• In Wisconsin we experience all 4 seasons.
▫ summer temperatures- between 70- 80 degrees
▫ winter temperatures-well below freezing
• Wisconsin is becoming “less cold”.
▫ Average increase of 1.1˚F
▫ Northwest Wisconsin is warming more
• Projections indicate that Wisconsin will warm
from 4-9˚F.
Today
• You will be studying
extreme temperatures of
selected WI cities.
• You will be studying
periods of unusually high
and unusually cold
temperatures in different
WI cities.
Heat Waves
• Heat waves constitutes several
consecutive days of extremely
high temperatures.
• They are accompanied by very
high humidity levels.
• We can say that there is a heat
wave when daily maximum
temperature of more than five
consecutive days exceeds the
average maximum temperature
by 5 Celsius degrees (9
Fahrenheit degrees).
How do Heat Waves occur?
• In the summer in warm climates, in
an area of high pressure with little
or no rain or clouds, the air and
ground easily heats to excess. A
static high pressure area can
impose a very persistent heat wave.
• The position of the jet
stream allows air on one side to be
considerably warmer than the other
side.
Jet stream-a current of fast moving
air in the upper levels of the
troposphere. Its position and
strength relate to the surface
temperature contrast between warm
and cold areas on Earth.
Cold Waves
• A cold wave is distinguished by a rapid
cooling of air in a 24 hour period. It is
marked by an entry of a very cold mass
of air into a large area.
• A Cold Wave may also be a period of
extremely cold and bad weather. This
weather can produce winds that lead to
strong wind chills. Cold waves can also
occur before or after phenomena such
as ice storms and blizzards.
• The precise criterion for a cold wave is
determined by the rate at which the
temperature falls, and the minimum to
which it falls.
How do cold waves occur?
• The jet stream develops a
large wave pattern with a
surface low and surface
high.
• Warm air transported
northward in the region
of the Pacific contributes
to intensify the ridge.
• Cold air transported
southward from Canada
east of the High amplifies
the trough.
Movement of Air Masses
Techniques you will need for today’s
lab:
• Last time you learned how to calculate in Excel:
▫ Means
▫ Medians
▫ Standard Deviations
• Today you will be making box plots and
calculating temperature anomalies.
Anomalies
Purpose: Anomalies tell us how much values depart from the average.
• Why are anomalies
used?
Anomalies are used to
determine if there are
noticeable changes in
temperature,
precipitation, etc. For
example: we use SST
anomalies to detect
changes in SST
associated to El Nino or
La Nina.
How are anomalies illustrated in a
plot?
Temperature Anomaly =Temperature-Average Temperature
Box Plots
Purpose: Good tool for conveying location and variation information in data sets.
In a box plot we:
• Calculate the median and
the quartiles (the lower quartile is the
25th percentile and the upper quartile
is the 75th percentile).
• Plot a symbol at the median (or draw a
line) and draw a box (hence the name-box plot) between the lower and upper
quartiles; this box represents the
middle 50% of the data.
• Draw a line from the lower quartile to
the minimum point and another line
from the upper quartile to the
maximum point. Typically a symbol is
drawn at these minimum and
maximum points, although this is
optional.
Thus the box plot identifies the middle
50% of the data, the median, and the
extreme points.
Vertical axis: Response variable
Horizontal axis: The factor of
interest
Homework:
• Study for quiz #1 Next Week.
▫ The material in the quiz will be from the first two
labs: Lab#1 and Lab#2