0:03 hey everybody it's Mr smees welcome to
0:06 Apes video notes for topic 7.3 which
0:08 will cover thermal
0:10 inversions our objective today is to be
0:12 able to describe thermal inversions and
0:14 how they relate to pollution and the
0:16 skill that we'll practice at the end of
0:18 today's video we'll be explaining an
0:20 environmental process or concept that is represented
0:22 represented
0:24 visually before we get into a thermal
0:26 inversion we have to understand the
0:28 urban heat island effect because it
0:30 helps explain how we actually form
0:32 thermal inversion so the urban heat
0:33 island effect refers to this idea that
0:36 urban areas are often warmer than
0:39 surrounding rural or Suburban areas and
0:41 that's due to a couple factors and so
0:43 the first factor is going to be their
0:46 lower albo so remember that albo refers
0:48 to how reflective a surface is and
0:50 because black top and Asal are really
0:52 prevalent in cities and there's less
0:55 vegetation they're going to be darker in
0:56 color and so they're going to absorb
0:58 more of the sun's Rays now remember that
1:00 when a surface absorbs absorbs more
1:02 sunlight and reflects less it's going to
1:04 radiate some of that absorbed energy out
1:06 as infrared radiation now infrared
1:09 radiation is perceived by humans as heat
1:11 and so this is why the sun's Rays
1:14 striking a surface make it warmer so
1:16 let's take a look here at a graphic to
1:19 help us out so we have our son back from
1:21 uh video 7.2 he's really getting you
1:23 know prominently featured in our air
1:25 pollution unit here and so we have sun
1:27 rays coming out and they're going to
1:28 strike both the downtown area and a
1:31 rural area that has a more trees now we
1:32 have red squiggly lines here to
1:34 represent all of the infrared radiation
1:37 that's given off by this black top and
1:39 by this asphal in the urban area the
1:42 downtown here in our diagram when it is
1:45 absorbing the sunf phace now rural areas
1:47 you know still are heated by the sun of
1:48 course but it's just going to be less
1:51 pronounced and that's because vegetation
1:53 reflects more sunlight compared to these
1:55 downtown areas it's a little lighter in
1:57 color and so here's a graphic again to
2:00 help you remember that because of Alo
2:02 being lower in the downtown or the urban
2:03 area we're going to have a higher surface
2:04 surface
2:07 temperature another reason for the urban
2:09 heat island effect is evapo
2:11 transpiration so try to think all the
2:13 way back to unit one the water cycle
2:15 where we learned that evapo
2:17 transpiration is the combination of
2:19 evaporation of water from you know
2:22 surfaces on land and then also the
2:24 transpiration which is water leaving you
2:27 know the pores of leaves and so it's
2:28 that combined effect where water is
2:31 leaving the surface of an area and
2:33 that's going to provide a cooling effect
2:35 so we can represent that here with these
2:37 large Blue squiggly arrows coming out of
2:39 our rural area all of these trees are
2:41 transpiring and so that's actually
2:43 taking a lot of the heat in that area
2:45 and dispersing it out into the
2:46 atmosphere carrying it away from the
2:49 surface so that's going to cool the area
2:51 now in the downtown urban area we have
2:53 fewer trees and so we have less
2:55 transpiration we're also probably going
2:57 to have less evaporation because we have
2:59 so much runoff and so we're not going to
3:02 be experiencing that evaporative and
3:04 transpirational cooling that's more
3:06 prominent when you have more vegetation
3:08 such as our rural area
3:11 here now we'll take a look at how a
3:13 thermal inversion or a temperature
3:15 inversion forms and so first we have to
3:17 understand the normal temperature
3:20 gradient for atmospheric temperature
3:23 near Earth and so normally Earth is
3:26 going to be heating the atmosphere the
3:28 most you know closest to its surface and
3:30 so we should expect to find the warm air
3:32 near Earth surface and we should expect
3:35 air to get cooler As We rise in altitude
3:37 and so this is for a couple reasons one
3:40 Earth surface is absorbing that sunlight
3:42 and then it's releasing as infrared
3:44 radiation and then also we have lower
3:47 pressures at higher altitudes remember
3:48 that lower pressure is going to result
3:51 in lower temperature and so a couple
3:53 reasons for this normal temperature
3:54 gradient that we see here what we have
3:57 to understand though is that this is
3:59 going to help disperse air pollutants
4:02 and and so because warm air rises we
4:04 have pollutants that form near Earth
4:05 these could be things like tropospheric
4:08 ozone or things like Smog or particulate
4:10 matter and because that warm air rises
4:12 we get convection currents and those are
4:14 going to be moving up so think all the
4:17 way back to the Hadley cell topic 4.5
4:19 you know we had warm air rising at the
4:22 equator and so this is beneficial from a
4:23 pollution standpoint because it helps
4:26 carry those air pollutants up and away
4:28 from our urban areas so let's take a
4:30 look now at what happen with a thermal
4:32 inversion so in a thermal inversion
4:36 we're going to invert or change or alter
4:38 this temperature gradient and so this
4:40 can happen for a couple reasons one we
4:42 could have a warm front that just moves
4:44 in uh this is especially prominent in
4:47 coastal areas you know like California
4:49 there's often times a warm air mass
4:50 moving in from the ocean and that's
4:52 going to cover up a colder air mass
4:56 below however we can also have this at
4:59 night in the summertime in dense urban
5:01 areas where they're basically absorbing
5:04 sunlight all day storing that energy and
5:05 then releasing it at night and the
5:08 surface of Earth cools off when the sun
5:10 you know goes down but that Heat's still
5:13 being released and so what happens is we
5:15 get this warm air mass that's trapped
5:17 beneath a colder air mass above and then
5:19 it's keeping this cooler air near Earth
5:21 surface and what that does is it shuts
5:24 off convection so here we have instead
5:26 of our air pollutant Rising away from
5:28 the urban areas they were in our normal
5:30 temperature gradient we have air plutons
5:32 being trapped close to Earth and again
5:33 this is because we basically have this
5:36 warm air mass kind of sandwiched between
5:38 a colder air mass above and a cooler air
5:40 mass below and it's not really allowing
5:43 for normal convection to carry these air
5:45 plutons away one thing we should notice
5:48 in this diagram or this picture here and
5:50 it's not explicitly in the notes on the
5:52 screen is that this becomes more
5:54 pronounced in you know geographical
5:56 Basin so when we have mountains on
5:59 either side this becomes especially you
6:01 you know worsened because there's not
6:04 going to be as much wind to disperse the
6:05 smog or the particulate matter that may
6:07 be collecting and it's going to be
6:09 harder for that warm air mass to move
6:12 out of the way as well and so basically
6:13 we have these conditions just
6:16 exacerbated or worsened when there are
6:18 geological factors that play like a mountain
6:18 mountain
6:21 range and then finally we'll wrap up by
6:22 talking about effects of thermal
6:24 inversions in a little more depth and
6:26 we'll start out here with a picture from
6:29 La that I think is just a really kind of
6:31 shocking image to help you really grasp
6:33 how extreme these thermal inversions can
6:36 be and so one of the major problems here
6:38 is that all of these air pollutants and
6:40 so this could be anything we've
6:42 discussed in unit 7even so far they're
6:44 going to be trapped closer to Earth and
6:46 by this time hopefully you see where
6:47 this is going which is that these are
6:50 all going to make respiratory irritation
6:52 in humans worse so we could have asthma
6:54 flareups and in fact there's some
6:57 studies that have linked increased
7:00 emergency room visits due to asthma ma
7:01 in the days that immediately follow a
7:04 thermal inversion event and so this is
7:06 you know scientifically supported by
7:08 data that we have you know increased
7:10 hospitalizations due to asthma it could
7:13 be also you know chronic uh obstructive
7:16 pulmonary Disorder so COPD or empyema
7:17 being worsened so all of these
7:19 respiratory diseases can put people in
7:22 the hospital uh you know normally and
7:23 then that gets even more pronounced when
7:25 we have a thermal inversion so it's
7:27 going to have economic costs it it taxes
7:30 our health care System you cost people
7:32 time at work they may lose income you
7:34 know jobs may lose productivity so
7:36 there's a lot of economic problems that
7:37 come along with a thermal inversion
7:40 event we also have potential for
7:42 decreased Revenue so if you're a tourist
7:45 and you were planning to visit La you
7:47 know it's feasible that you might look
7:49 ahead at the weather and you might look
7:50 at pictures like this you might be less
7:53 likely to go and so it can cost you know
7:55 countries or specific cities you know
7:58 revenue from tourism and then finally we
7:59 are going to experience decreased
8:01 photosynthetic activity so plants are
8:03 also going to suffer because of this
8:05 it's harder for sunlight to penetrate
8:06 this thick blanket of smog that's
8:09 trapped due to this thermal inversion
8:11 and so again we have reduced
8:13 photosynthetic activity so for practice
8:16 frq 7.3 today I want you to take a look
8:17 at this diagram where we have normal
8:19 conditions on the left and a temperature
8:21 or thermal inversion on the right I want
8:23 you to explain what these arrows
8:25 indicate about how temperature
8:28 inversions impact air plutons such as smog
