[MUSIC] We will see now, how we are able to measure the salinity of the ocean surface, using a new technology that has been developed recently in the framework of a mission of the European Space Agency, the SMOS mission. This mission has the objective of providing information to study the evolution of the global water cycle. And why is salinity very important for this objective? We have here a series of characteristics that we have to take into account. For example, salinity is very important in determining the density of seawater, and then the determining the global currents of the world ocean. Second, salinity can always be modified through the atmosphere, so it strongly linked to any phenomenon. That is, let's say, providing or modifying the interaction between the ocean and the atmosphere. It's important to take into account that a very high percentage of the evaporation that takes place on Earth is over the ocean, 86%. And also precipitation. 78% of the precipitation is just occurring over the ocean. It means that the part of the global water cycle that is corresponding to the ocean is extremely important. Here, we have some numbers that will help you to understand what are the amounts of water that we're considering when we examine the ocean. Compare the water that is on the oceans to what is on land. See what are the amounts of exchanges between the atmosphere and the ocean, compare between the atmosphere and land. So, it's clear that if we want to know what is happening with the exchanges of water through this global water cycle, we have to look at the ocean and we have to be able to measure salinity. How can we do this? This is a figure that represents here different microwave frequencies from very low to 5 gigahertz. Remember that this is the frequency we use to measure temperature. And this is again, the sensitivity, as higher is the sensitivity, we'll have more chances of measuring this variable. In this case, salinity should be measured at around 1 gigahertz or lower than this. And the same time and considering that we have to take into account all the processes that participate in the radiation that will be captured by the radio emitter. Here, we have another figure, where, again the vertical we have the sensitivity, in the horizontal we have the different frequencies. But here we depict the sensitivity for different variables. Salinity is in this case here. Salinity has maximum salinity at lower frequencies. The effect of wind speed on the surface, the effect of the clouds, the effect of water vapor, the effect of temperature, it's clear that we want to measure salinity using low microwave frequencies. And to do this, we use a specific frequency band. This one here, that is protected by international agreements. This means that no one can emit at this frequency because this frequency is reserved for passive observations. Here, we have a figure that for different temperatures indicates what is the range of what we call brightness temperature. That’s the variable that is measured by the radiometer. And these four different salinities. So, it appears that for the range of salinities in the ocean, that range of measurements is really very low. It means that we need a very accurate instrument to be able to retrieve salinity. In this other figure here, we see that, in fact, using different incident angles, that is looking at the ocean at different inclinations. And using what we call the polarized radiation, we obtain more data. So that the amount of information we need to retrieve salinity can come from different observations of the same water spot on the ocean. So, what is this new technology that has been introduced, developed in this mission. What you have here is what is called a radio telescope. Radio astronomers are using these configurations for 50 years now. So, there are an array of antennas distributed over a large area. This way, the astronomers can catch the information from far galaxies, for example. But through a system that is through a mechanism that is called interferometry, the information captured by the different antennas can be mixed. And provide a single information as if in fact, it was a very big antenna here. So, with SMOS mission, we have done something similar. We have built a satellite that has three arms, and in these arms there are small antennas. An array of antennas distributed in a similar way than radio astronomers do. This way, we can obtain information from the same part of the ocean, but with slide differences along the different antennas. And through the interferrometric mechanism, we can reconstruct the information as it was a very big antenna. This way, we intend to obtain salinity with an accuracy of the order of 0.1 salinity units with a spatial resolution of the order 100 to 200 kilometers and with a temporal resolution between 10 and 30 days. This is what this satellite is providing. This is an orbital satellite, we get these orbits. This is what we call an ascending orbit, when the satellite is moving this way. This is a descending orbit, when the satellite is moving this way. And these maps show through different colors the different salinities that are observed by the satellite. As we're required a very precise calibration, this information is not as perfect as we would like. It contains a lot of noise. But this can be solved by averaging different orbits, building maps. And this is the kind of information we can obtain. This is not like SST map that has been obtained over large areas with the single radiometer. Here, we need to put together different orbits in a temporal window in this case this has been down in 10 days and averaging in cells of one degree latitude by one degree longitude. This is the kind of sea surface salinity maps we are able to provide with this SMOS mission. That is using a completely new technology that had never been used in Earth observation before. And what kind of information we obtain from this. For example, look here at the Gulf Stream. These are thermal images of the Gulf Stream, and this is a typical situation for winter. This is a typical situation for summer, in winter, you see here, we can observe the Gulf Stream. In summer, as the water has been hit by solar radiation, it's much more difficult to identify exactly the stream as it was in winter. Here we have the maps we are obtaining with smog sea surface salinity map. This is a sea surface salinity map where we have superimposed the ocean currents derived by other means. We are at the salinity structures coincide very well with the motion, of the complicated motion with meanders and adding something of the Gulf Stream. If we observe the temperature map, we see that the complicated current circuit is not well-identified through the thermal circuit. It's clear that this new satellite that for the first time is providing salinity over the ocean is able to give us some information that we could not obtain with thermal sensors. Even the special resolution, the original special resolution in thermal satellites is higher. What we have here are examples of different kinds of studies that can be done using this sensor where we have strong contrast of salinity. We are not worried about noise and we can use higher special resolution. For example, in river, this chart is like the Mississippi here, like the Amazon here. In the case of the Gulf Stream, as we said before, or in the case of the upwelling that we have off Panama. So in all these cases, the salinity sensor can provide information that no other sensor was able to provide until now with the same accuracy. Then we show here. We have shown that with this new technology, ocean observation from satellite is a real added value we have in comparison to the regular. Not only in city, but other satellite observations of the ocean.
