Thermal inversions occur when a layer of warm air traps cooler air near the Earth's surface, preventing the normal dispersion of air pollutants and exacerbating their negative impacts on human health and the environment. This phenomenon is often linked to the urban heat island effect.
Mind Map
Clicca per espandere
Clicca per esplorare la mappa mentale interattiva completa
hey everybody it's Mr smees welcome to
Apes video notes for topic 7.3 which
will cover thermal
inversions our objective today is to be
able to describe thermal inversions and
how they relate to pollution and the
skill that we'll practice at the end of
today's video we'll be explaining an
environmental process or concept that is represented
represented
visually before we get into a thermal
inversion we have to understand the
urban heat island effect because it
helps explain how we actually form
thermal inversion so the urban heat
island effect refers to this idea that
urban areas are often warmer than
surrounding rural or Suburban areas and
that's due to a couple factors and so
the first factor is going to be their
lower albo so remember that albo refers
to how reflective a surface is and
because black top and Asal are really
prevalent in cities and there's less
vegetation they're going to be darker in
color and so they're going to absorb
more of the sun's Rays now remember that
when a surface absorbs absorbs more
sunlight and reflects less it's going to
radiate some of that absorbed energy out
as infrared radiation now infrared
radiation is perceived by humans as heat
and so this is why the sun's Rays
striking a surface make it warmer so
let's take a look here at a graphic to
help us out so we have our son back from
uh video 7.2 he's really getting you
know prominently featured in our air
pollution unit here and so we have sun
rays coming out and they're going to
strike both the downtown area and a
rural area that has a more trees now we
have red squiggly lines here to
represent all of the infrared radiation
that's given off by this black top and
by this asphal in the urban area the
downtown here in our diagram when it is
absorbing the sunf phace now rural areas
you know still are heated by the sun of
course but it's just going to be less
pronounced and that's because vegetation
reflects more sunlight compared to these
downtown areas it's a little lighter in
color and so here's a graphic again to
help you remember that because of Alo
being lower in the downtown or the urban
area we're going to have a higher surface
surface
temperature another reason for the urban
heat island effect is evapo
transpiration so try to think all the
way back to unit one the water cycle
where we learned that evapo
transpiration is the combination of
evaporation of water from you know
surfaces on land and then also the
transpiration which is water leaving you
know the pores of leaves and so it's
that combined effect where water is
leaving the surface of an area and
that's going to provide a cooling effect
so we can represent that here with these
large Blue squiggly arrows coming out of
our rural area all of these trees are
transpiring and so that's actually
taking a lot of the heat in that area
and dispersing it out into the
atmosphere carrying it away from the
surface so that's going to cool the area
now in the downtown urban area we have
fewer trees and so we have less
transpiration we're also probably going
to have less evaporation because we have
so much runoff and so we're not going to
be experiencing that evaporative and
transpirational cooling that's more
prominent when you have more vegetation
such as our rural area
here now we'll take a look at how a
thermal inversion or a temperature
inversion forms and so first we have to
understand the normal temperature
gradient for atmospheric temperature
near Earth and so normally Earth is
going to be heating the atmosphere the
most you know closest to its surface and
so we should expect to find the warm air
near Earth surface and we should expect
air to get cooler As We rise in altitude
and so this is for a couple reasons one
Earth surface is absorbing that sunlight
and then it's releasing as infrared
radiation and then also we have lower
pressures at higher altitudes remember
that lower pressure is going to result
in lower temperature and so a couple
reasons for this normal temperature
gradient that we see here what we have
to understand though is that this is
going to help disperse air pollutants
and and so because warm air rises we
have pollutants that form near Earth
these could be things like tropospheric
ozone or things like Smog or particulate
matter and because that warm air rises
we get convection currents and those are
going to be moving up so think all the
way back to the Hadley cell topic 4.5
you know we had warm air rising at the
equator and so this is beneficial from a
pollution standpoint because it helps
carry those air pollutants up and away
from our urban areas so let's take a
look now at what happen with a thermal
inversion so in a thermal inversion
we're going to invert or change or alter
this temperature gradient and so this
can happen for a couple reasons one we
could have a warm front that just moves
in uh this is especially prominent in
coastal areas you know like California
there's often times a warm air mass
moving in from the ocean and that's
going to cover up a colder air mass
below however we can also have this at
night in the summertime in dense urban
areas where they're basically absorbing
sunlight all day storing that energy and
then releasing it at night and the
surface of Earth cools off when the sun
you know goes down but that Heat's still
being released and so what happens is we
get this warm air mass that's trapped
beneath a colder air mass above and then
it's keeping this cooler air near Earth
surface and what that does is it shuts
off convection so here we have instead
of our air pollutant Rising away from
the urban areas they were in our normal
temperature gradient we have air plutons
being trapped close to Earth and again
this is because we basically have this
warm air mass kind of sandwiched between
a colder air mass above and a cooler air
mass below and it's not really allowing
for normal convection to carry these air
plutons away one thing we should notice
in this diagram or this picture here and
it's not explicitly in the notes on the
screen is that this becomes more
pronounced in you know geographical
Basin so when we have mountains on
either side this becomes especially you
you know worsened because there's not
going to be as much wind to disperse the
smog or the particulate matter that may
be collecting and it's going to be
harder for that warm air mass to move
out of the way as well and so basically
we have these conditions just
exacerbated or worsened when there are
geological factors that play like a mountain
mountain
range and then finally we'll wrap up by
talking about effects of thermal
inversions in a little more depth and
we'll start out here with a picture from
La that I think is just a really kind of
shocking image to help you really grasp
how extreme these thermal inversions can
be and so one of the major problems here
is that all of these air pollutants and
so this could be anything we've
discussed in unit 7even so far they're
going to be trapped closer to Earth and
by this time hopefully you see where
this is going which is that these are
all going to make respiratory irritation
in humans worse so we could have asthma
flareups and in fact there's some
studies that have linked increased
emergency room visits due to asthma ma
in the days that immediately follow a
thermal inversion event and so this is
you know scientifically supported by
data that we have you know increased
hospitalizations due to asthma it could
be also you know chronic uh obstructive
pulmonary Disorder so COPD or empyema
being worsened so all of these
respiratory diseases can put people in
the hospital uh you know normally and
then that gets even more pronounced when
we have a thermal inversion so it's
going to have economic costs it it taxes
our health care System you cost people
time at work they may lose income you
know jobs may lose productivity so
there's a lot of economic problems that
come along with a thermal inversion
event we also have potential for
decreased Revenue so if you're a tourist
and you were planning to visit La you
know it's feasible that you might look
ahead at the weather and you might look
at pictures like this you might be less
likely to go and so it can cost you know
countries or specific cities you know
revenue from tourism and then finally we
are going to experience decreased
photosynthetic activity so plants are
also going to suffer because of this
it's harder for sunlight to penetrate
this thick blanket of smog that's
trapped due to this thermal inversion
and so again we have reduced
photosynthetic activity so for practice
frq 7.3 today I want you to take a look
at this diagram where we have normal
conditions on the left and a temperature
or thermal inversion on the right I want
you to explain what these arrows
indicate about how temperature
inversions impact air plutons such as smog
Clicca su qualsiasi testo o timestamp per andare direttamente a quel momento del video
Condividi:
La maggior parte delle trascrizioni è pronta in meno di 5 secondi
Copia in un clicOltre 125 lingueCerca nel contenutoVai ai timestamp
Incolla l'URL di YouTube
Inserisci il link di qualsiasi video YouTube per ottenere la trascrizione completa
Modulo di estrazione trascrizione
La maggior parte delle trascrizioni è pronta in meno di 5 secondi
Installa la nostra estensione per Chrome
Ottieni le trascrizioni all'istante senza uscire da YouTube. Installa la nostra estensione per Chrome e accedi con un clic alla trascrizione di qualsiasi video direttamente dalla pagina di riproduzione.
