[MUSIC]. Let's continue with the lecture. We leave the previous one saying that we have to know the energy and mass exchanges between the ocean and the other components of the system, of the planet system. That they are the air and the land, and we are going to see in which conditions. Let's remember, first of all, what were is the distribution, in this table. Or we can also see at this scheme. In these schematics, we'll see very, is the water in the ocean and also on the continents, this is the river. The river discharge to the ocean. These are water condensation in the atmosphere, clouds, and the arrows. So, the volume of exchanges, this is the maximum, the regression over the ocean it's 7.5 volume or 13.5 cubic hectometers per second. This is the precipitation over the ocean. This is evaporation from land, from plants and from the land, and from rivers and lakes. And this is the precipitation on land. And finally, this is the discharge from land to the ocean. Note that there is no flow from, direct flow from the ocean to the land. Because it's almost negligible, the washing water of waves, (the effects of) washing the shores are almost negligible. We are talking about these figures. The other interesting thing in this diagram is that some of this flow can be measured. And they are actually measured, some of them. For example, precipitation can be measured. Typically, it is measured on land, not everywhere. In the ocean, it is very strange, very rare to find data from precipitation, because there is no, perhaps the ships could collect it, but typically it shows the approximate. There are approximations with and I love these things. The rivers are more or less controlled, so the flow from the rivers is typically controlled. But, the flow, for example, of water when there is a big storm, a big rain storm, near the coast, and all this water. Washing the coast is not elevated. So, the flows which are measured have big uncertainties, but the main important flow is not known. So, it's only approximate. So, let's have an idea of what happens with the ocean. Let's start with the landscape. This is a mountain range. Here are mountains, move all these off, and let's put some water here, some ocean. Here is the ocean. If we want to put this water from the ocean to the mountain, we need a system to pump this water up to here. Who is doing that? This is done by the sun. Here, let's imagine that this is a sun. The sun is hitting all. And here is carrying the moisture, the water vapor to the atmosphere, and then precipitating to the mountain. So, there is no way. Starts precipitating, after evaporating. And this is the scheme that we have seen. There is no way from the ocean to go over land. This is a more important difference between the two fluids that are wrapping our planet. The air, the fluid, the air, which is here, can go up the mountain, and go down, and it can go everywhere. The ocean is restricted by the distribution of continents, and cannot overcome. We'll see this has strong consequences that we'll see later. We have seen that the two wrapping fluids, there are one which is free to go everywhere, and the other is constrained. But the oceans, which represents this fluid, which is constrained by the continents, have much more heating capacity, and also have most of the water. So if, but what happens is that we live in dry earth, so, we're not as humans, we're not living on the sea. So, we don't know, we don't know almost nothing in comparison with the others. So, we have much more heat capacity, we have the transport this. The water is about almost all the water, experience the flow of water from the ocean to the atmosphere is the maximum. However, we have a very little information on this, because most of the water cycle is known just on land, on dry land. And what happens is that the moisture is not measured. Remember, we say that we don't have any way to measure the flow of the operation. We have a formula, which is this one. This is a formula that is proportional. This is a constant, is proportional to wind velocity, and this is a function of the difference between the specific water humidity of the saturation and the water temperature, and the specific humidity of the air. So, if the air in coming to the water has low specific humidity, then it's dry air, these are an important number. But if this value is high, or even higher than this, this is almost zero, or negative, so we don't have evaporation. But there's no way to do, so this is only an approximation. So, is something like, the operation is something like this sponge going there. And if we have in such conditions, it's moving with the wind across the sea surface, and absorbing the humidity. If the density of the air at the water level is higher than the density of the air incoming, this water retained by this point is kept here, because it cannot go up. While if there is this, if the density of the air at the water level is lower than the density of the incoming air, then you can see how this is moving upwards, because of this difference in density. So, it is important to be effective, that the temperature of the air should be lower than temperature of the water. Or in other words, if temperature of the air is higher, the incoming is higher than the temperature of the water, our equation will not be effective. And this is an important thing, because it can affect the system. It is well known that in global warming conditions, as the air increases it’s temperature, it increases it’s capacity to collect water vapor. And it's assumed that all the water cycle will accelerate so we'll have a stronger precipitation, we'll have more hurricanes and so on. What happens, however, if the, sorry, at the beginning of the heating process, as the air is more easily warmed than water, because has lower heat capacity. So, temperature of the air is increasing faster than temperature of the water, so that may, remember, that this is the condition for the evaporation to be less effective. Then if this decreases, the evaporation on the ocean may decrease, or may decrease in certain places. And the proportion of new water arriving to the continent will also decrease, but there is also another thing that is interesting. It's that evaporation is, at the same time, cooling the water surface, because it's losing latent heat. So, it's forming convection on the ocean. And this is one of the main, the main mechanism for the thermal circulation. If we have a vigorous thermal circulation, we will have deep convection in places where there is, in cold places of cold air, and relatively warm water. But if this is cold water, or fresh water, or both, then the convection is just here. And there is no convection, convection, and then may be effect to slow the circulation, as we will see later. This is just a scheme to follow, and another way to estimate, more or less, what are the zones where the evaporation is higher than others, is with the salinity. The salinity distribution will reflect, more or less closely, what is the evaporation minus precipitation. Because one thing, compensates the other. But note, that in case of evaporation, over the air pollution is deep convection or convection, why this one, precipitation, we are putting fresh water on the surface, so limiting this. So, the behavior, the value may be the same, but it depends on each one of the terms, precipitation or evaporation. So, you can have this difference constant, but if the operation is higher. So, if the operation is higher, you have also more precipitation at play, so you can have a more enhanced thermohaline situation. And finally, just have a, sorry, this is a separate, the other operation. The operation, it's similar, the patterns are similar. So, these are the... The big nucleus of evaporation are more or less in the tropics. And at the Equator, you have the higher precipitation. So, what's evaporating here is precipitating here. And the global views we will be this way. And that's all for this chapter.
