By DAVE FISHER/ecoRI.org News
staff
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| This satellite image shows high and low U.S. land surface temperatures for July. Click for larger image. (NASA) |
Southern New England has already had a couple of
"official" heat waves this summer. A heat wave is defined in these
parts as a period of three or more days where the ambient air temperature is
more than 90 degrees. Chances are good that we will see more of them this
summer, but what really happens during a heat wave?
Heat waves form when
high-pressure systems in the mid-levels of the atmosphere strengthen and remain
over a region for at least several days. This is a common occurrence in the
summer for both the Northern and Southern hemispheres, as the jet stream
"follows the sun." On the equator side of the jet stream, in the
middle layers of the atmosphere, is the high-pressure area.
Summertime weather patterns
generally move more slowly than wintertime patterns. Consequently, these mid-level
high-pressure systems also move slowly. High-pressure systems basically
compress air towards the earth’s surface; the “sinking” air acts as a dome that
traps heat instead of allowing it to lift. Without lift, there are fewer clouds
and minimal chance for rain. The end result is a continual build-up of heat on
the surface. This compressed air, coupled with high humidity, is what gives the
feeling of “thickness” in the air during a heat wave.
When a heat wave descends on
notoriously humid southern New England, stepping outside can feel like walking
into someone’s mouth.
Cooking the air
Heat waves are by far the deadliest weather phenomenon in the United States.
Between 1992 and 2001, deaths from excessive heat numbered 2,190, compared with
880 deaths from floods and 150 from hurricanes. Furthermore, it is widely
accepted that heat-related deaths are frequently misreported or not reported.
Fortunately, most
heat-related illnesses, ranging from the annoying heat rash to the
life-threatening hyperthermia, or heat stroke, are non-lethal if diagnosed in
time. Most heat-related illnesses are treated by hydrating the patient with
isotonic fluids orally — think sports drinks — or in more severe cases fluids
are introduced to the overheated patient intravenously.
As with many other illnesses,
heat-related ones disproportionately affect the young, old and poor. These
groups are less likely to have access to the preventive measures, such as air
conditioning, required to stave off these effects.
Heat waves can affect air
quality, triggering respiratory reactions in those suffering from lung ailments
such as asthma and emphysema.
Excessive heat basically
“cooks” the atmosphere. Coupled with the forcing of air — and all of the
pollutants and particles therein — toward the surface under high-pressure
"domes," this cooked and compressed air becomes a soup of ozone,
carbon soot and pollutants from tailpipes to smokestacks.
Heat waves may be worsened in
urban areas due to the heat-island effect. Every bit of infrastructure, from
roads to skyscrapers, absorbs heat and slowly releases it back into the
atmosphere. This heat energy has a cumulative effect on the ambient air
temperature in highly developed areas.
High-pressure domes create a
sort of temporary, quasi-closed system, at least when it comes to pollutants
and heat energy. These systems trap not only the sun’s direct heat energy but
also the heat reflected by infrastructure, as well as absorbed and released by
every surface under the dome. All of that heat energy accumulates under the
high-pressure system.
Soil, water and food
impacts
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Heat and drought top the
list of natural hazards that can kill
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Though a heat wave isn’t necessarily accompanied by drought — nor a drought by
a heat wave, as Rhode Island
nearly experienced thanks to
a virtually snow-less winter followed by a dry spring — each can have a
distinct and cumulative impact on the other.
As topsoil dries out in a
drought, plants die. When the things that are converting the sun’s energy
directly and shading the soil to prevent evaporation die, the exposed soil is
more likely to dry out if a drought is accompanied or followed by a heat wave.
When soil dries out, it actually absorbs more energy than wet soil, adding
another input to the compressed soup under a high-pressure system.
Heat waves and drought don’t
really affect water quality so much as demand for water. Whether for
irrigation, drinking or showering, water usage goes up in both scenarios, so
when coupled, water is at a premium.
The tandem of heat and
drought is destroying crops and soil throughout the United States. Drought and
heat have hit America’s farmlands hard this summer, and food prices are
expected to spike dramatically. CNN has reported that crop insurance claims
from American soy, wheat and corn farmers may hit $20 billion this year. Corn prices are expected to hit $9 a bushel by
summer’s end. The average is anywhere from $3-$4 a bushel.
Watch this National Oceanic and Atmospheric Administration (NOAA) video on the spread of the most recent heat wave across the United States. Satellite imagery from July 13-21.
Energy usage
As a rule, energy usage goes up in the summer — thank you air conditioners —
but a heat wave can see a 30 percent to 60
percent spike in that
already elevated rate.
Turning on all of those air
conditioners in an area, virtually at once and for long periods of time, wreaks
havoc with the local power production and distribution system. On top of that,
the heat energy exhausted by those air conditioners is added to the
already-heat-energy-rich soup of surface air, exacerbating heat waves. During
the last heat wave that hit the Midwest, power demand in the Detroit area rose
to the point that rolling blackouts were instituted in some suburbs.
Global and local
warming
Until recently, the scientific community has been reticent to link any
particular weather event to the effects of climate change, but in the past few
months, that has begun to change. From Somalian famine to freak weather events such as floods in Russia,
scientists of all stripes have begun to view these events as signals of a
larger pattern of change.
Climatologists are indicating
that the increase and frequency of severe weather events — such as the
windstorm that recently swooped from Chicago to D.C., killing 17 and leaving 2
million without power, and the heat and drought that are gripping much of the
United States — are examples of a larger pattern of extreme weather that
science has long predicted would be caused by the warming of the planet.
A recent study sanctioned by Environment Rhode Island showed that the
occurrence of extreme rainstorms and snowstorms are up 90 percent between 1948
and 2011. In other words, heavy downpours or snowstorms that happened once
every 12 months on average in 1948 now happen 6.3 months, on average.
Storms with extreme
precipitation also increased in frequency by 85 percent in the New England
region during the period studied, and New England ranks first nationwide for
the largest increase in the frequency of storms with heavy precipitation.
The biggest rainstorms and
snowstorms are getting bigger. The amount of precipitation released by the
largest annual storms in the Northeast increased by 26 percent from 1948 to
2011, according to Environment Rhode Island.
Stay cool, but don’t
beat the heat
The recommended response to a heat wave is to remain inside and crank up the
A/C, but running that machine on "sub-arctic" will actually worsen
heat events in the near and long terms.
Air conditioning has a magnifying effect on localized heat events. All
that exhaust becomes trapped under the high-pressure dome, but more troubling
is the potential worsening of global warming.
As the heat rolls into Rhode
Island, on go the A/C units, releasing heat to be trapped in the immediate
atmosphere, and drawing more energy from fossil fuel-fired power plants,
releasing more pollutants and greenhouse gases, accelerating climate change,
worsening heat waves, causing more energy draw for air conditioning, et cetera,
ad nauseam. This is known as the positive feedback loop.
When the heat settles in for
an extended period, you shouldn’t need to set the thermostat lower than 80
degrees. Most air conditioners act as dehumidifiers, as well, which will
significantly lower the humidity in your home, making the heat a bit more
tolerable. By adjusting the thermostat on your A/C unit, you can significantly
reduce your energy consumption.
Though extreme heat has a
host of impacts to our society, it seems our society is exerting an even
greater influence on weather patterns both local and global. To mangle an
oft-heard expression in these parts: It’s not the heat, it’s the humanity.