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Claire Parkinson discusses uses of the Aqua satellite data

“Prior to satellites,” said Parkinson, “communities would be struck by a hurricane with pretty much no warning at all. Now, any hurricane that starts to form, satellites will pick it up.”

Claire Parkinson: Aqua is one of quite a few satellites that NASA has in orbit now around the Earth, and all of these satellites are providing us with a phenomenal picture of the Earth system as a whole, the entire globe.

Claire Parkinson is a climate scientist at NASA’s Goddard Space Flight Center. She’s Project Scientist with the Aqua satellite mission. Aqua’s six instruments measure in the visible, microwave, and infrared parts of the spectrum to get different perspectives on Earth processes, within moments after they happen.

Claire Parkinson: People have made use of the near-real time data for a large variety of uses, one being forest fires and the help in distributing where the fire fighters go in order to most efficiently handle the forest fires, but another being dust storms. The fact that the Aqua satellite can see the dust storms, major dust storms really well has been very helpful to people about to be struck by a dust storm.

For example, the Aqua satellite captured images in 2009 of Iraq’s biggest dust storm in living memory. And Aqua produces hurricane images for scientists and others who live near a coast.

Claire Parkinson: Prior to satellites, some communities would be struck by a hurricane with pretty much no warning at all. Now, any hurricane that starts to form, satellites will pick it up. And the fact that you can see the hurricane forming and start to see where it’s likely to be going with the use of the satellite data to see where the hurricane is, and then the use of computer models to forecast where it’s likely to be headed, this is just a tremendous value to society.

Dr. Parkinson talked about the highlights of NASA’s Aqua mission, which launched on May 4, 2002 and is expected to continue to perform well for years after its six-year design life.

Claire Parkinson: First off, one of the things that we’ve been particularly pleased with is the fact that the Aqua data are able to be received pretty close to real time through a direct broadcast system. And indeed, people have made use of the near-real-time data for a large variety of uses, one being for monitoring forest fires and thereby helping forest services to determine where best to deploy fire fighters to most efficiently handle the fires, and another being for monitoring dust storms. The fact that the Aqua satellite can see the major dust storms really well has been very helpful to people about to be struck by a dust storm.

Another practical application is for weather forecasting. The atmospheric temperatures and water vapor derived from Aqua data show enough improvement that they are making an impact on weather forecasting for the agencies that are using them. That includes NOAA in the United States, and also quite a few weather forecasting agencies elsewhere around the world.

So there’ve been a lot of practical applications of the Aqua data, which have been really pleasing to see. In addition, in terms of the science impact, the data from Aqua are being used by many hundreds of scientists from around the world, with over a thousand papers a year being published using Aqua data.

One particular highlight that I’ll mention is the monitoring of carbon dioxide with the AIRS instrument on Aqua. Carbon dioxide is a key greenhouse gas in the Earth’s atmosphere, and its importance has been known for decades. Back in the 1950s, during the International Geophysical Year, the IGY, Charles David Keeling started measuring carbon dioxide from a station in Hawaii, the Mauna Loa station, and that record has been kept up ever since. So since the late 1950s, we have an excellent record of carbon dioxide from that one station in Hawaii. We also have records from other stations that were created later. But all these stations, each of them gets data from just one point. The AIRS instrument on Aqua gets the data globally. Now these carbon dioxide data have some really interesting features in them. For instance the Mauna Loa station, which is the gold standard of carbon dioxide measurements, gets a wonderful depiction of the seasonal cycle of carbon dioxide, wherein carbon dioxide goes up during the Northern hemisphere fall and winter, and then as vegetation starts growing in the spring and starts pulling in carbon dioxide from the atmosphere to use during photosynthesis, the carbon dioxide amounts in the atmosphere go down. The result is a notable seasonal cycle every year where the carbon dioxide in the atmosphere increases in the fall and winter, then decreases in the spring and summer as vegetation breathes in the carbon dioxide for photosynthesis. This happens year after year after year.

Well, Charles David Keeling, after just a year of his measurements at Mauna Loa, had recorded the seasonal cycle really well. But as the years went by, and it didn’t take many, after just a few years, it was clear to him that he was recording not just the seasonal cycle but also an overall upward trend, an upward trend that has continued all the way to the present and is a result of human activities that add carbon dioxide to the atmosphere. Now with the Aqua data, we can see both those features, the seasonal cycle and also the upward trend, for the period since the Aqua launch back in 2002, and we can see them not just at Mauna Loa or any other individual points but on a global basis. An animation of the daily global maps of carbon dioxide from the AIRS data shows the carbon dioxide level going up and down in the seasonal cycle and also reaching higher and higher levels each year over the course of the record. This is one of the primary science highlights that has recently come from the Aqua data.

In explaining what the Aqua satellite does, Parkinson referred to the ancient practice of ‘sounding,’ where mariners drop lines with weights overboard to determine the water’s depth. She said three of the six instruments onboard the Aqua satellite, the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), and the Humidity Sounder for Brazil (HSB), act like sounders through Earth’s atmosphere.

Claire Parkinson: This threesome is a sounding system that’s sounding through the atmosphere, allowing scientists to derive all sorts of information at many different levels in the atmosphere. This information includes atmospheric temperatures, water vapor amounts, and the concentrations of some of the key greenhouse gases that are producing so much attention now because of the warming of the climate system. Among those key greenhouse gases that the AIRS instrument is able to measure for us are carbon dioxide and methane. We’re also getting measurements from AIRS of ozone, which is a greenhouse gas but additionally has an impact in terms of the stratospheric ozone layer. Ozone is actually desirable in the upper atmosphere, because the ozone helps block ultraviolet radiation from getting down to the Earth’s surface. Through the ozone measurements with AIRS, the ozone hole is another topic that scientists can examine with the Aqua satellite.

Of the other three instruments on Aqua, one is called the MODIS instrument, and that stands for MODerate resolution Imaging Spectroradiometer. Another is called the AMSR-E instrument, and that stands for Advanced Microwave Scanning Radiometer for the Earth Observing System. And the last of the six Aqua instruments is the CERES, which stands for Clouds and the Earth’s Radiant Energy System. The MODIS instrument is the instrument that gets the highest spatial resolution of any of the Aqua instruments; what that means is that it gets the greatest spatial detail. It’s measuring visible and infrared radiation, and it’s seeing lots of things on the Earth’s surface as well as in the atmosphere.

Among the variables that the MODIS instrument monitors are cloud cover and aerosols in the atmosphere, and a wide range of surface features including vegetation, fires, dust, and snow cover. Some of the importance of the MODIS instrument is the fact that, because it’s obtaining fires and dust really well from space, it’s able to help such agencies as the US Forest Service and other forest services around the world. When a major forest fire is occurring, it shows up on the MODIS data in a way such that forest services can use the data to help deploy their fire fighters most efficiently. That is one of the ways in which Aqua data become really useful in a practical sense, complementing the primary purpose of the Aqua mission, which is for the science.

Dr. Parkinson talked more about being able to ‘see the science’ happening inside a hurricane through Aqua’s satellite images.

Claire Parkinson: Aqua instruments can see hurricanes in different ways, and it is cool to see the variety. For instance, the MODIS instrument gets beautiful pictures of a hurricane using visible radiation and showing the hurricane as you would see it if you were flying above it in an airplane.

But because of the different types of instruments we’ve got on Aqua we can also see other things highlighted. For instance, the eye wall and rain bands in a hurricane get highlighted with certain channels from the AMSR-E instrument. And also, after a hurricane passes by, the sea surface temperatures that the AMSR-E instrument records actually sometimes show what’s called the ‘cold wake’, where the sea surface temperatures have dropped. The cold wake forms because as the hurricane goes by, it churns up the water, bringing up some colder water from beneath, and that churning up of the water ends up very visible from the satellite data in terms of revealing the cooling of the sea surface temperatures. Also, the AIRS instrument can get us further information about the hurricanes by getting us things like the cloud top temperature and pressure.

The Aqua data are helping so many people in so many ways, and it’s a wonderful honor and privilege to be able to be a prime player in a mission that is doing so much.

Jorge Salazar

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