Flight Training - May 2023 - 26

PREFLIGHT WEATHER
BY THOMAS A. HORNE
APPLY NOW FOR
AOPA'S FLEXIBLE
AVIATION LOAN
DO YOU WANT QUICK & EASY?
Fill out a quick online application and be
approved in one business day.
DO YOU WANT AFFORDABLE?
A $10,000 flight training loan with monthly
payments as low as $250 a month. AOPA
Member rates starting at WSJ Prime +5%.
DO YOU WANT FLEXIBILITY?
You can borrow as much as 3x your monthly
income (up to a max of $100k).
UPSIDE-DOWN TEMPERATURES
BE ON THE LOOKOUT: WARM OVER COLD
Go to
aopa.org/financemytraining
to apply today.
AOPA's Flexible Aviation Loan can be put
to work right now to get you on your way as
a better trained, more proficient pilot.
GENERALLY SPEAKING, AIR TEMPERAtures
aloft are colder than air
temperatures at lower altitudes. The
standard temperatures we learn in ground
school back this up. Sea level standard
temperature is 15 degrees Celsius/59
degrees Fahrenheit, but up at 10,000 feet
it's a brisk -5 degrees Celsius/23 degrees
Fahrenheit. But those are standard temperatures.
In the real world, temperatures
can be topsy-turvy. Sometimes temperatures
can increase with altitude and be
colder at or near the surface than aloft.
These situations are called temperature
inversions, or simply inversions.
One of the ways inversions happen
is when the ground cools overnight. The
ground heats up and cools down more
rapidly than air aloft, so if there's a big
high-pressure system overhead and skies
are clear, surface temperatures drop
faster than those aloft. If there's enough
moisture in this low-level air, surface
temperatures can drop to the dew point
temperature and fog can form.
Valleys are prime locations for nighttime
or early morning inversions, and
their fogs form as cold, dense air draining
from high terrain that cools as it sinks.
It will take the heat of the day to heat up
the ground, burn off the fog, and break up
the inversion layer. Coastal areas where
warmer air aloft moves over lower layers
created by cold ocean currents-think
26
FLIGHT TRAINING MAY 2023
California's coastal marine layers-can
also create inversions.
Fronts can also create inversions.
When fronts move through, they typically
bring warmer air with them. With
warm fronts, warm air aloft rides up and
over the colder, denser air masses below.
In the colder months, any precipitation
falling from the frontal surface aloft will
go from warm air to cold. Snow, freezing
rain, and other icing conditions can
be the result. Cold fronts can push and
lift the warmer air ahead of them. This
warm air aloft may act as what's called
a capping inversion, or " cap " to prevent
any heat rising from low-level air
percolating upwards during the day-but
if that heated air is warm enough, and
rising fast enough, it will " break the cap, "
and the stage is set for thunderstorms
and broad areas of rain.
Inversions are great for trapping air
and creating reduced visibilities in fog,
smoke, haze, and pollutants. It's natural
for air near the surface to make thermals
that mix with the air above it, but if the
air aloft is warmer than the air below,
then that can't happen. You might see a
thin cumulus layer that marks the warmover-cold
border, but that's about it. As
always, warm air rises, but only if the air
around it is colder.
tom.horne@aopa.org
http://www.aopa.org/financemytraining
Flight Training - May 2023

Table of Contents for the Digital Edition of Flight Training - May 2023
