 All right let's talk sea breeze and land breeze. Where do they come from? Why do they occur? So let's say we've got a body of water right here and here is our land mass. Let's just say the beach for all intents and purposes. What is a sea breeze? A sea breeze is when the air that's above the water is flowing in across the land. So this is a sea breeze. Air originates from the sea and goes to the land. A land breeze is going to be the exact opposite where the air is flowing from the land and going to the sea. Question is why? Ask yourself when do you recall being in a really big sea breeze? Was the sun shining? Was it maybe a nice hot summer day? If your answer is yes to those questions then you're right. That's typically when a sea breeze occurs. So what's happening? Well what we're going to get is differential heating of the water versus the land. So during the day the sun is shining, it's baking down. If you walk on the sand, if you go to the beach on a day like this, that sand is pretty hot and if you're barefoot you notice right? You're either going to have your sandals on or sometimes if you don't have sandals you're going to go throw your towel down, walk on the towel, pick the towel up, throw the towel down again and walk as far as you can because that sand can get really really toasty. So during the course of the day the sand is going to heat up as the sun is baking down. So we're going to say that the ground is heated up. Now if you compare the temperature of the sand to the temperature of the water the water of course is going to be quite cool and chilly. So we're going to say cool even cold certainly depends upon where you live but if you're in southern California you go out on the beach then you go in the water you're getting that nice Alaska cold water coming down with the California current. It can be pretty chilly. So we've got a differential heating pattern. The sand is going to get really hot the water is not and it's going to maintain a relatively similar temperature almost throughout the year. It's going to be relatively cool to cold. Why? That's a big question. Why isn't that we get this differential heating? Well there's something called specific heat. Specific heat is the amount of heat necessary to change the temperature of one gram of a substance by one degree centigrade. So if I want to the temperature of one gram of a substance by one degree centigrade I need for that substance to absorb heat energy in order to raise the temperature and the same is true in reverse. If I want to lower the temperature of a substance then I need to remove heat from that substance. So again specific heat is the amount of heat needed to raise or lower the temperature of one gram of a substance by one degree centigrade. Well as it turns out water H2O has one of the higher specific heats of known substances where land in this case we're talking about sand, granitic materials, sediments that has a relatively low heat. So if I have a high specific heat that means I need lots of heat to change the temperature of the substance. If I have low specific heat that means I need little heat to change the temperature of a substance. So now we go outside it's a nice bright sunny day the sun is beating down on the landscape. If you have beach or land land has that low specific heat which means it takes only a little bit of heat to raise the temperature of that substance. So if I have a lot of heat coming down and I have a low specific heat threshold that means that the temperature of that substance is going to change rather dramatically. So land has a low specific heat which means it's going to get really really hot during the course of the day and also keep in mind that the mixing depth of heat energy is land is relatively shallow. That means in the top handful of inches that's where you're going to maintain most of that heat. Now if you look at water on the other hand water has a high specific heat which means it's going to take a whole lot more heat in order to change the temperature of that substance. So even during the course of a nice bright hot sunny day and the water is absorbing a lot of heat it's still not enough to dramatically change the temperature of that substance. In addition to that when you take a look at water water has a very deep mixing depth. So when the heat is absorbed in the water it's going to mix in a very long water column and therefore the heat is going to be distributed in a greater depth than it would on land. Okay so what does all of this mean? Well that means during the course of a nice bright sunny day the land is going to get heated and if the land gets heated then what's going to happen is you're going to generate a low pressure system because the air above the land which is in contact with the land is also going to get heated and when that heated air expands because that's what heated air does it expands it becomes less dense than the surrounding air and this air is going to lift up or rise into the sky. So again we are fabricating a low pressure system. On the other hand water is going to maintain a relatively cool temperature and air that's in contact with the cool water is going to maintain a cool temperature. So here we're going to generate a higher pressure system and again in this high pressure system is generated because the air is colder and cold air is denser air and denser air is heavier air so it is going to tend to sink. So we have a nice high pressure system generated. This high pressure system by the way is emphasized even further because when this low pressure air lifts up into the sky that's above the land that air has got to be replaced right. You don't just have air that goes up and then you've got this empty void. So what happens is air from the sea flows in to replenish the low pressure air that is lifted up. So we've got two things going on. We've got the replenishment of air but then we also have the high pressure system generated because of the temperature differential. So you'll notice now we've got air flowing from high pressure to low pressure. It's originating over the sea. It's going to land. We've got our sea breeze and by the way the air up here from the land goes back toward the ocean to replenish this air and so we now have this great convection of air that's occurring and once again this is our sea breeze. So now the flip side of the sea breeze is the land breeze. So when we take a look at the land breeze instead of having the sun up that's put the moon so now you're back at the beach. You're going to have your bonfire. How about that? That's always fun to have a bonfire at the beach. Now we take a look at specific heat again. We don't have any heat coming from the sun right? So now what's going to happen is both the land and the sea are going to lose heat. The heat's not being replenished by the absorption of solar energy so now we are losing heat. Land remember has a low specific heat. It loses some air and the temperature drops a lot. Water on the other hand loses some heat and it drops temperature a little so the high specific heat of water moderates its temperature. Again if you have a high specific heat it takes a lot of heat lost to lower the temperature just like it takes a lot of heat gain to increase the temperature and land with its low specific heat means if you lose just a little bit of heat you're going to lower the temperature quite dramatically. If you absorb a little bit of heat you're going to increase the temperature potentially dramatically that's low specific heat versus high specific heat. So now what's going to happen is the land during the night is going to get pretty cold and air that's in contact with the land is also going to get rather cold. So here the air is going to once again become dense it's going to become heavy and sink. We've just created a high pressure system. Water on the other hand is going to be relatively warm compared to the cold land because remember the the temperature of the water has not changed dramatically from day to night. It stayed relatively the same whereas the land is the one that went from hot to really cold. So now if water is relatively warm then the air above the water is going to be relatively warm it will expand it will lift up into the sky and it will create a low pressure system. So now take a look air is going to flow from high to low there it is and here is our land breeze. So if you go outside at night and you're at the beach and you're at a bonfire don't sit here because you're going to get smoked. The best place is on this side of the fire and is better anyway because you can look at the ocean waves at night it's really cool. Now in this little discussion I talked about density of air is being density of air being different. So let's say we've got our parcel of air and we have our molecules in our parcel of air. If I cool this air then the air is going to contract it's going to become more dense. So now this would be the air notice I've got one two three four five six seven eight nine molecules of air in my picture one two three four five six seven eight nine. You'll notice that in this cold air it's a lot denser than this original air. What if I heated the air if I heated the air then the air is going to expand and now you'll notice that my molecules are further apart this warm air is less dense than the surrounding air. So again less dense air will lift higher density air will sink and that's why we see this high low pressure differential when we differentially heat the land versus the water. All right so that's our land breeze and that's our sea breeze. You find land breeze and sea breezes over different coastal regions around the world. Next time you're out at the ocean check out the direction with which the air flows see if it matches up to what the physics and the chemistry suggests it should be. All right thank you and I'll see you in the next video.