The total solar eclipse that will occur later this month in the United States will help researchers improve the modeling capabilities of the Earth's energy system.
It was mid-afternoon, but pitch black in Boulder, Colorado on August 3, 1998. A thick cloud appeared overhead and darkened the land below for more than thirty minutes. Well-calibrated radiometers showed that very low levels of light reached the ground, so low that researchers decided to simulate this interesting event using computer models. Now in 2017, inspired by the Boulder event, NASA scientists will study the lunar eclipse to learn more about Earth's energy system.
On August 21, 2017, scientists look forward to this year's total solar eclipse passing over the Americas to improve Earth's energy modeling capabilities. Guiong Wen, a NASA scientist who works at Morgan State University in Baltimore, heads a team that will collect data from the ground and satellites before, during and after the eclipse so they can simulate this year's eclipse using an advanced computer model, called a XNUMXD radiative transition model. If they succeed, Vonn and his team will help develop new calculations that will improve our estimates of how much solar energy reaches the ground, and our understanding of one of the key players in regulating Earth's energy system, the clouds.
The Earth's energy system is a constant dance to maintain a balance between incoming radiation from the sun and outgoing radiation from the Earth into space, which scientists call the Earth's energy budget. Clouds, both thick and thin, play an important role in influencing the energy balance.
Like a giant cloud, the moon during the 2017 total solar eclipse will cast a large shadow over a swath of the United States. Vonn and his team already know the moon's dimensions and light-blocking properties, but will use instruments on the ground and in space to study how this large shadow affects the amount of light reaching Earth's surface, especially around the edges of the shadow.
"This is the first time we can use measurements from the ground and from space to simulate the movement of the moon's shadow over the land in the United States and calculate the energy that reaches the land," said Won. Scientists have made extensive atmospheric measurements during previous solar eclipses, but this is the first opportunity to collect coordinated data from the ground and a spacecraft viewing the entire Earth in sunlight during an eclipse, thanks to the National Oceanic and Atmospheric Administration's Deep Space Climate Observatory (DSCOVR) launched in February 2015.
Although a moon blocking the sun during a solar eclipse and clouds blocking sunlight reaching the face of the earth are two different phenomena, both require similar mathematical calculations to accurately understand their effects. Vonn predicts that this experiment will help improve calculations in current models and our knowledge of clouds, especially thick low clouds that can cover about 30 percent of the Earth at any given time.
In this experiment, Wen and his team simulated the total solar eclipse in a XNUMXD radiative flux model, which helps scientists understand how energy spreads across Earth. Today the models tend to show clouds in one dimension. In many cases, these one-dimensional calculations can create useful scientific models for understanding the atmosphere. But sometimes a XNUMXD model is needed to get more accurate results. The big difference is that XNUMXD clouds reflect or scatter solar energy in many directions, from above and below, and also from the sides of the clouds. As a result of this three-dimensional behavior, the amounts of energy that reach the ground are different from what a one-dimensional model can predict.
"We're testing the ability to perform a certain type of complex calculation, testing a three-dimensional mathematical technique, to see if it's an improvement over the previous technique," said Jay Herman, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a researcher participating in the project. . "If this is successful, then we will have a better tool to implement in climate models and we can use it to answer questions about the Earth's energy budget and climate."
For the upcoming solar eclipse, Vonn and his team will be in Casper, Wyoming and Columbia, Missouri to collect information about the amount of energy being transferred to and from Earth before, during and immediately after the eclipse using several ground-based instruments.
A Pandora spectrometer device developed by NASA and placed on the ground will provide information on the degree of presence of each given wavelength of light, and a solar radiation meter will measure the total solar energy from all directions that descends on the earth's surface. Immediately before and after the eclipse, the scientists will measure other information such as the amount of absorbing trace gases in the atmosphere, such as ozone, nitrogen dioxide and small aerosol particles, which will also be used in the XNUMXD model.
At the same time in space, NASA's Earth Color Imaging Camera (EPIC) aboard the DSCOVR spacecraft will observe the light leaving Earth and allow scientists to estimate how much light has reached Earth's surface. In addition, NASA's two MODIS satellite instruments, aboard its Terra and Aqua satellites, launched in 1999 and 2002, respectively, will provide observations of conditions in the atmosphere and on the Earth's surface in the times before and after the solar eclipse. The scientists will then combine the ground measurements with the measurements observed by the spacecraft.
This experiment completes NASA's decade-long commitment to observe and understand contributions to the Earth's energy budget. For more than 30 years, NASA has measured and calculated the amount of energy that hits the upper part of our atmosphere, the amount of solar energy that is reflected back into space and how much thermal energy our planet emits into space. These measurements were made possible thanks to instruments and tasks such as ACRIMSAT and SOLSTICE (launch year: 1991) andSOURCE (Launch year: 2003) and also the device series CERES which are in Terra, Aqua and Suomi-NPP (launch year: 2011).
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