0:01 in this video we're gonna talk about
0:03 heat transfer we're gonna talk about
0:06 heat energy and we're gonna talk about
0:08 temperature and this is very important
0:10 in beginning to understand how weather
0:13 works so when we talk about energy what
0:14 is energy
0:16 well energy is the capacity to do work
0:20 so whether it's heating of the Earth's
0:24 surface or changing water in different
0:27 phases it requires energy to do so so we
0:29 need to discuss energy before we can
0:31 talk about how weather actually works
0:34 because this would be the foundation to
0:36 how weather actually occurs in our
0:38 atmosphere so when we talk about energy
0:41 we talk about two forms of energy
0:43 kinetic energy and potential energy
0:46 kinetic energy is energy that is in
0:49 motion or already in motion so think
0:53 about a car a car is driving therefore
0:56 it's in motion and that is what kinetic
0:59 energy is potential energy is energy
1:02 that is possessed by system that has the
1:06 potential to be kinetic energy down the
1:08 road so if we think about a car for an
1:10 example but a car is parked it's not
1:12 moving if it's not moving it's not doing
1:15 any work therefore not giving off any
1:20 energy however we know that cars can and
1:23 are in motion and so when we drive our
1:25 car therefore it is in motion we are
1:27 doing work because we are traveling from
1:28 one place to the other
1:31 therefore it is then kinetic energy so
1:32 that's the difference between kinetic
1:35 energy and potential energy but since
1:37 we're talking about meteorology we want
1:39 to talk about heat energy because that's
1:42 what temperature is when we talk about
1:45 temperature what in the normal world we
1:48 talk about how hot or cold the air is
1:50 outside boy in the scientific community
1:53 what temperature is it's the measure of
1:56 the average kinetic energy of all the
2:01 constituents of air molecules so all of
2:04 the nitrogen molecules all of the oxygen
2:07 molecules all of the argon air molecules
2:10 so all of those molecules moving is
2:12 kinetic energy it's heat
2:16 and that's what we relate to as
2:19 temperature so the faster that these
2:21 molecules are moving the higher their
2:23 kinetic energy the higher their kinetic
2:25 energy the higher the heat energy and
2:29 therefore we say that the warmer the air
2:32 is and so when these molecules are not
2:34 very excited and they're moving slowly
2:37 we say that the kinetic energy is less
2:39 therefore the heat energy is less and
2:42 therefore the temperature is cooler and
2:45 so when we talk about heat we can
2:47 actually break heat down into three
2:51 different sub parts we talk about latent
2:53 heat specific heat and sensible heat and
2:55 this becomes very important in the
2:57 physics of our atmosphere because this
3:00 is how water plays a role and
3:02 temperature plays a role in our
3:03 atmosphere and we're going to discuss
3:05 this a little bit in greater detail in
3:08 week four but to define these terms when
3:10 we talk about specific heat we're
3:11 talking about the amount of energy that
3:15 is required to change a unit of mass by
3:19 one degree so in this case we're talking
3:22 about water here and so how much energy
3:24 is required to raise the temperature of
3:29 water by one degree and so that is what
3:31 specific he is you can easily remember
3:35 that by saying specific heat one degree
3:37 Celsius that's a specific number so
3:39 specific heat the amount of energy
3:41 needed to raise waters temperature by
3:43 one degree
3:45 now latent heat is also extremely
3:49 important in our atmosphere now lady he
3:51 is the energy that is required to change
3:55 the state of water in this case since
3:57 we're talking about meteorology how much
4:01 energy is required to change water from
4:05 a gas to a liquid a liquid to a solid or
4:08 a liquid to a gas whatever combination
4:10 you want to make that is what latent
4:12 heat is and latent heat is going to be
4:14 very important and we're gonna discuss
4:16 it in greater detail again when we get
4:18 to week four
4:21 now sensible heat sensible heat is the
4:23 energy required to change the
4:26 temperature of a substance but with
4:29 the phase-change so sensible heat and
4:31 specific key are essentially the same
4:34 thing except specific heat is more
4:36 specific as we're talking about how much
4:38 energy was required to raise the
4:42 temperature of water by one degree now
4:44 when we talk about heat transfer
4:47 throughout the earth how is heat
4:51 transferred from one entity to the other
4:54 so when we talk about heat flow we talk
4:58 about things going from hot to cold and
5:02 so heat flows via three different ways
5:04 either by conduction convection or
5:07 radiation now the earth receives all
5:10 three now starting with conduction
5:12 conduction is the transfer of heat
5:16 through matter by molecular motion so
5:18 this would be an example of you're
5:22 cooking and you touch a hot pan and you
5:24 don't realize it and you burn yourself
5:26 slightly that would be an example of
5:29 heat transfer by conduction there was
5:32 some source of heat that heated the pan
5:33 or the pot or whatever you're cooking
5:37 with you touched the pot the pot was hot
5:39 because of molecular transfer the matter
5:41 that or the molecules that make up the
5:44 matter of the pot was heated you touched
5:48 the pot that was hot you got burned it
5:51 transferred heat to your hand your brain
5:53 told you hey that's hot and that is how
5:55 heat is transferred that's what
5:58 conduction is convection is the transfer
6:00 of heat by mass motion or via
6:03 circulation so if you've ever seen water
6:07 boil before that is conduction you have
6:11 water or air that is heated either at
6:13 the bottom of the pan or the surface of
6:18 the earth is heated by the Sun hot air
6:21 rises or hot water rises and then cold
6:24 air comes down to replace the hot air
6:27 that's rising so when we look at boiling
6:30 water this is exactly what we see and so
6:34 here you notice that the hot water rises
6:36 and in the cold water that was at the
6:40 top of the pot comes down to replace the
6:42 water that has now risen to the top of
6:44 the pot okay and so this is what that
6:46 bubbling motion does and this is
6:49 actually what happens in our atmosphere
6:51 well we talk about radiation this is how
6:54 the whole machine works and so we know
6:57 that the earth receives its energy via
6:59 the Sun so we're talking about
7:01 electromagnetic radiation
7:03 aka we're just talking about solar
7:06 energy so solar radiation and that is
7:08 the transfer of electromagnetic energy
7:10 via electromagnetic waves and that's
7:13 what the Sun does the Sun shines its
7:15 solar energy reaches the surface of the
7:17 earth and the earth heats either by
7:21 conduction and/or convection so all
7:26 three heat transfers occur on the earth
7:29 and it's actually what makes weather
7:31 happen so when we break it down
7:34 radiation if you're talking about you
7:37 know cooking with an open fire radiation
7:39 right that's the heat that you feel from
7:41 fire and if you've ever had a bonfire
7:43 before you got close to that fire
7:46 you can feel how hot that fire is well
7:48 those are the electromagnetic waves that
7:51 are traveling towards you that give off
7:54 heat and so that's what radiational heat
7:57 is convection would be water boiling so
7:59 here in this diagram you see that the
8:02 hot water is at the bottom of the pot it
8:06 boils it bubbles hot water or hot air
8:09 works the same way Rises and then cold
8:12 water at the top row cold air from
8:14 higher up in the surface comes down and
8:17 replaces the hot air or hot water that
8:20 has now risen so this is what convection
8:23 is it's just one big giant loop and then
8:24 conduction right that would be the
8:28 transfer of heat through matter and so
8:30 when we actually look at it in a
8:33 meteorological terms the Sun comes out
8:35 and heats the surface of the earth now
8:37 remember that the sun's rays do not
8:40 directly heat air molecules all air
8:43 molecules are transparent so how does
8:47 the air actually get warmed while the
8:49 Sun comes out and heats the surface of
8:51 the earth the surface of the earth is
8:54 there heated and the air that
8:56 lies right above the surface of the
8:59 earth is therefore heated by conduction
9:02 because it's in close contact with the
9:05 ground that air that sits right above
9:08 the surface of the earth becomes hotter
9:10 than the surrounding environment hot air
9:12 rises if you've ever watched a hot air
9:14 balloon hot air balloons work because
9:18 hot air rises in cold air sinks same
9:21 thing with water warm water rises to the
9:24 top and cold water sinks so in this
9:27 diagram over here on the left in Part A
9:29 you see that the Sun heats the surface
9:31 of the earth the surface of the earth
9:33 heats the air that lies right above the
9:36 surface of the earth and those air
9:39 parcels become warmer than the
9:41 surrounding environment and they rise so
9:43 then what happens is that those air
9:45 parcels will rise to a certain level
9:49 become saturated and form a cloud so
9:52 when air is rising cool air has to come
9:54 down to replace it and this is what's
9:56 known as convection so whenever you see
9:59 clouds occur this is what happens and
10:01 this is what we call convection now
10:01 we're going to talk more about
10:04 convection and more about how clouds
10:06 form later on in the semester but for
10:09 right now know that these are the three
10:11 ways that heat is transferred throughout
