Skip to 0 minutes and 17 seconds The atmosphere is a very important component of the earth’s system. It’s important because it protects us from cosmic rays but also because it protects us from other forms of radiation and serves as a regulator for temperature on the planet. So life as we know it is possible on Earth because of the presence of the atmosphere. And the atmosphere is extremely important. And it’s extremely important also to study its characteristics and observe it from space. The atmosphere is 99% oxygen and nitrogen, and this is what we breathe in. But at the same time, there are also gases and particulates that are quite important. For example, in the atmosphere, we have CO2, which is very important greenhouse gases.
Skip to 1 minute and 3 seconds We have ozone, which is extremely important to regulate the amount of ultraviolet radiation that we receive. And then we have other compounds, for example, so-called aerosols that are also important in the climate system. Because they regulate the amount of radiation that we receive from the sun, interact with our radiation, serve as cloud forming particles, and also, they regulate the amount of radiation that is emitted and that gets back out to space from the earth’s surface. So all of these tiny particles and gases, so-called trace gases, are extremely important for the climate. These gases cannot be observed with naked eye. You need special sensors that can measure at different so-called wavelengths.
Skip to 1 minute and 57 seconds And they can infer information about trace gases from the radiation. So we don’t directly measure the presence of these gases or the amounts. But indirectly, we can find their signatures in the electromagnetic radiation that is emitted by the earth and that has to travel through the atmosphere to reach the satellite. So the view from space is extremely important. And, in fact, a lot of things were discovered enabled by satellite observations, because we couldn’t really see them from down below. So the view from above is very important. And it has been instrumental to the development of earth monitoring and modelling and in the general sense. There are several techniques from a satellite that could be applied to viewing the atmosphere.
Skip to 2 minutes and 47 seconds There is the so-called nadir-view, in which the satellite looks directly at what’s below and just observes what comes out of the earth’s atmosphere. There is the so-called limb-view, in which the satellite observes from a side. And those are important techniques because one enables a more horizontal resolution. And that is the nadir view. You can really look at high resolution. But you don’t have vertical information, because you sense the total column in the atmosphere. But the limb-sounding view, on the contrary, allows you to especially sense the higher levels of the atmosphere, the stratosphere, for example, and also get the vertical information.
Skip to 3 minutes and 31 seconds Because you’re dissecting the atmosphere and cut it into different levels, and then you get the information from the various levels. So both are extremely important. The horizontal resolution for nadir-looking is more coarse. But still, you get the vertical information, which is extremely important. So aerosols are interacting with the radiation that comes from the sun to the earth and then also with the radiation that comes from the earth and is emitted back to space. And because of this, it’s possible to sense them from satellites, because satellites sense the radiation. And then you can infer properties about the aerosols through analysis of this radiation that the satellite has sensed.
Skip to 4 minutes and 18 seconds And that is extremely important in my job, which is that of predicting the aerosol state with few days ahead. And I use the satellite information, the observations derived from the satellite, to initialise the model and constrain the model so that the prediction is as accurate as possible or as close as possible to current observations of the state of the aerosols in the atmospheres. And a similar thing is applied to other trace gases, ozone, carbon monoxide, as well as observing wildfires and emissions of carbon dioxide and biomass burning from fires. So it’s the same principle. Some instruments, for example, the so-called images, they look at the refracted solar radiation. And they sense mainly clouds, aerosols.
Skip to 5 minutes and 8 seconds They can give information about surface characteristics, surface albedo. And those are the visible images. Then you have a set of still passive sensors that instead measure if you want the temperature of the planet. And they also, because they sense the emitted radiation, but in the infrared spectrum. So this is not the visible part, but the infrared part. And some trace gases, you can see the signature of these gases in the infrared part, for example, CO2, CO, and ozone, and other trace gases, methane. So you use the infrared part of the spectrum to sense the atmosphere. You can also go to microwave wavelengths, and you also get other information about other parameters, including precipitation, for example.
Topic 2b - Looking at the atmosphere
The atmosphere plays a vital role in making the Earth habitable, including shielding us from harmful UV electromagnetic radiation, holding the air we breathe, and helping keep Earth at the necessary temperature for maintaining a good supply of liquid water – thus making life possible on our planet. In order to assess the condition of the atmosphere, and to study its evolving complexity, it is important to monitor the status of, and changes in, atmospheric properties - such as chemical composition, temperature, pressure, wind speed and wind direction. Earth observation techniques provide the opportunity to collect global measurements of such parameters, and is therefore essential to monitoring and forecasting our weather, and to improving our understanding of atmospheric science, especially climate change.
This video will introduce you to some of the ways in which we can assess atmospheric properties using EO data collected by satellites. Dr Angela Benedetti will explore why it is vital that we measure a range of atmospheric parameters, and will explain how such Earth observations are advancing our understanding of the atmosphere and its role in the climate system.
- Dr Angela Benedetti
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Explore the Imagery, Data and Satellites:
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