The 1995 Heat Wave: How Likely is a Recu
By: Thomas R. Karl & Richard W. Knight
Heat
Waves
Contribution of Land-Atmosphere Coupling to Recen
QuickTime™ and a
By: Fischer,
Seneviratne,
decompressor
are
needed
to see this picture.
Lüthi,
& Schär
By: Kathryn Bullinger
Double Major: Geography and Earth Sciences
Kathryn Bullinger
Geography and Earth Sciences Double Major
Lets Start with the Basics:
What are they? …(if the name alone isn’t enough of a clue…

Defined: It is a prolonged period of excessive
heat, often accompanied by excessive
humidity.
 Qualifications:



The weather is noticeably warmer than normal for
the time of year and climate.
The unusual weather continues for a prolonged
period of time long enough to be considered a
specific phase.
The weather will most likely bring about some sort
of increased risk to humans and animals, and may
place an increased strain on power supplies.
How Does This Happen?

When an air mass becomes quasistatic/stationary over a region (and it meets
all those qualifiers), it is labeled a heat wave.
QuickTime™ and a
decompressor
are needed to see this picture.
Why they are Dangerous:

Heat kills by taxing
the body beyond its’
normal abilities.

QuickTime™ and a
decompressor
are needed to see this picture.

On average, < 1000
Americans die heatrelated deaths each
year (as reported by
the American
Meteorological
Society)
Heat waves kill
more Americans
than any other type
Why they are Dangerous:
Cont’d.

People who live in
urban areas are at a
greater risk from
heat wave effects.



Stagnant
atmospheric
conditions trap
pollutants.
Poor air quality
aggravates health
problems.
Asphalt and concrete
store heat longer,
which results in
higher nighttime
QuickTime™ and a
decompressor
are needed to see this picture.
The Chicago Heat Wave of
‘95:



July 12th - 16th, 1995.
Approximately 700 people died in just 5 days.
July 13th:



Chicago’s infrastructure had a meltdown
(almost literally).




The temperature in the city hit 106° F.
Including the heat index, it felt hotter than 120° F.
Communities lost water pressure.
Train rails and roads buckled.
Paramedics, hospitals, and morgues
overwhelmed.
Majority of deaths were elderly men who lived
alone.
On to the 1st Paper!

The analysis:



Considers the apparent
temperature, Tap , which
attempts to quantify the
effects of temp. and
moisture on the human
body.
“Focuses on the severity
and duration of extreme
heat waves relative to
changes of mean T,
variance, day-to-day
persistence of T, and the
cross correlations of
these quantities.”
Also created future
QuickTime™ and a
decompressor
are needed to see this picture.
Notable Points that they
Took into Account for their
Analysis:
High dewpoints play a key role in high
Tap values.
 Minimum T may be especially
important.
 Deaths due to heat are greatest during
the 1st few days of a heat wave.
 Acclimatization factors also seem to be
important.

Assessing the Wave:

QuickTime™ and a
decompressor
are needed to see this picture.
Use the Tap
algorithm developed
by Steadman.
 Tap values apply to
shaded daytime
conditions and night.
 Focus on the the full
distribution of hourly
T’s during the 1st
few days for 26
stations in and
around the Chicago
Min, 25P,
50P, 75P,
and Max T
plotted for
the
warmest
annual 1, 2,
and 3-day
events in
Chicago
history.
Calculated the
average Tap for
any 2-day period
during the ‘95 heat
wave to help
delineate the
aerial extent of the
wave.
Calculating Trends of Tap

Used values from 1,
2, and 3-day
intervals between
June 15th and
August 15th (the
period of most
intense summertime
heat in the
Midwest).
 “The analysis was
performed for both
observed Tap and
those adjusted for
the effects of the

Heat island
adjustments applied
based on the
algorithm developed
by Karl et al.
 “Used the algorithm
to help develop an
interval that would
bound the effects of
urbanization on T
trends.”
Applying the Algorithm


Assumed the hourly T’s
at 1500 LT were
associated with the max
and T’s at 0600 LT with
the min.
Started with a
population of 0 for each
urban area, with the
final population
estimate equal to the
1990 city census (“to
provide an upper bound
for the effect of
urbanization on the
QuickTime™ and a
decompressor
are needed to see this picture.
The Probability of
Recurrence

QuickTime™ and a
decompressor
are needed to see this picture.
10,000 sequences on
monthly July daily
max and min values
were simulated using
various values of a 4parameter model.


Mean Tap
Sa - the variance of
monthly mean Tap
calculated across
years
 Sm - the variance of Tap
calculated for a given
month using daily
values
 r - persistence

“Using the simulated
July values of daily
max and min Tap, the
probability of
exceeding specific
thresholds of T can
be easily calculated
relative to what
actually occurred
during 1995.”
Their Results
Is there a looming doomsday in our future?

The stationarity of Tap:


The overall trends of
Tap in the Midwest are
more moderate than
the Chicago results.
 However, the climate
in the Midwest appears
to be stationary.



Sensitivity of the
probabilistic model:

Changes in mean Tap
are important, but
other parameters are
also critical, such as
persistence and
variance.
Recurrence for the ‘95
heat wave in the
present climate:

The probability of max Tap
exceeding 48.9° C two
consecutive days in a
row is < 1 %, or 1 in 150
years.
The probability of having
min Tap values above
31.6° C for two
consecutive days is
extremely rare.
Recurrence for the ‘95
heat wave in a changed
climate:

Projected increases in T
The Sensitivity of
Multivariate and Univariate
Changes
Daily
Daily
Their Summary
An event like the Chicago heat wave of
‘95 is quite rare, due to the elevated 2day nighttime (min) temperatures.
 Duration and intensity of heat waves
have been shown to be affected by 4
parameters.
 Min Tap probability results especially
rare and unusual.
 In their opinion, and event like the
Chicago heat wave will not be repeated

Guess What!? I’m Not Done
Yet!
Paper Number Two…omg

QuickTime™ and a
decompressor
are needed to see this picture.
Most of the recent
European heat
waves have been
preceded by a
spring precipitation
deficit.
 Regional climate
simulations
conducted with and
w/o
land/atmosphere
coupling for 4 major
An Intro to European Heat
Waves

2003 heat wave
record-breaking;
over 40,000 deaths.
 Crop shortages.
 Forest fires.
 These highlight the
importance of
understanding what
causes these
extreme events.
QuickTime™ and a
decompressor
are needed to see this picture.
The Experiment:



Focuses on Europe and
the north-eastern
Atlantic.
Performs a 46-year
simulation (1960-2005)
with a coupled landsurface scheme (CL
simulation).
Repeat the simulations
for ‘76, ‘94, ‘03, and ‘05,
but with soil moisture
uncoupled from
atmospheric evolution
(UCL simulation).
QuickTime™ and a
decompressor
are needed to see this picture.
The 4 Major Waves


1976:
 Confined to northern
France and southern
England
 > 35 hot days
observed.
 16-month period of
precip. deficits prior.
1994:
 Affected central
Europe and parts of
the Mediterranean.
 Somewhat weaker
on the seasonal
scale.

2003:




Record-breaking.
Affected central
Europe and the
Mediterranean.
40-60 hot days
observed.
2005:

Confined to the
Iberian Peninsula
and southern
France.
 Heat wave most
Simulations
What the Figures Show Us:
“Based on these simulations, it can be
seen that the NHD as well as the HWD
is substantially reduced if the soil
moisture is prescribed (or dictated) by
climatological mean conditions (UCL
simulations).”
 T amplification through CL is stronger
for daily max T’s than for min and mean
T’s.
 “CL interactions contribute to an

So Basically…

QuickTime™ and a
decompressor
are needed to see this picture.

Each of the 4
waves was
preceded by a
mean precip.
deficit of at least 4
months.
CL simulations
show excess in
surface net rad.
leading to an
increase in
evaporation.
My Thoughts…

There is no eminent
danger of us being
fried by a drastic
spike in summer
temperatures.
 Heat waves do
happen, but they are
very infrequent.
 Lack of precipitation
plays a role in hotter
temperatures for the
approaching

Future Study:

I would be curious to
see if there is a
connection to heat
waves on different
continents during the
same year. I think
some investigation
into that could be
interesting…
Questions?
QuickTime™ and a
decompressor
are needed to see this picture.