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MODIS Data Product Non-Technical Description - MOD 07

As well as being the place where weather systems are born, travel, and die, the atmosphere is a dynamic system that forms a protective shell around the planet. Without this protective layer, life on the planet would not be possible. There would be no air to breathe, we would have to protection from the Sun’s powerful radiative energy, temperatures would skyrocket during the day and plummet at night, and we’d have no protection from debris moving through the solar system. Without the atmosphere, the Earth would be much like the Moon – barren and inhospitable to life. The importance of our atmosphere to life on Earth cannot be understated, which is why so much effort is made to understand it and why, for example, the “hole” in the ozone layer over Antarctica receives so much public attention.

In order to help scientists study and gain an understanding of earth’s protective layer of gasses, MODIS scientists have developed the MOD 07 Atmospheric Profile product, which describes the atmosphere in four ways: total-column ozone, atmospheric stability, atmospheric temperature- and moisture-sounding, and total-column precipitable water. These profiles are based on MODIS' sequential observations of the columns of atmosphere between the satellite and the Earth's surface as the satellite orbits overhead.

The total-column ozone product provides data for monitoring ozone levels – and thereby helps to evaluate potential harm via anthropogenic (human) sources. It also helps weather forecasters to predict the position and intensity of jet streams (wind currents 10-15 miles up in the atmosphere moving at very high speeds, often exceeding 250 mph) and to identify turbulent regions of the atmosphere for airplanes to avoid.

The total-column precipitable-water (i.e., water vapor) is an estimate of how much precipitation could be produced by the moisture contained in a column of the atmosphere. This product can be used to track regional and global climate phenomena, like monsoons. The presence of water vapor in the atmosphere influences heat and energy budgets (water vapor is the most powerful greenhouse gas) and cloud formation, and of course, plays a major role in the hydrological cycle.

Both the ozone and total precipitable water products are needed to develop and refine atmospheric correction algorithms. Corrections are needed for MODIS' observations of surface features, since those observations may be influenced by the conditions in the atmosphere at the time of the observation. The correction algorithms that MODIS scientists develop must be extremely accurate so that the data products that they help to produce, such as vegetation amount and health, surface reflectance, and ocean color, are of the highest possible quality.

The atmospheric stability observations provide key indications of how likely a portion of the atmosphere is to produce thunderstorms, resulting in precipitation on a large scale. For example, having very dense air resting on top of less dense air is unstable because within a confined volume (like a column of atmosphere) the denser air will be heavier and will want to sink, while the less dense air is more buoyant, and will want to rise. To interpret how the environment affects thunderstorm potential and severity, meteorologists have invented several stability indices that characterize the stability of the atmosphere in a single number. MODIS provides stability indices at a high spatial resolution, which helps forecasters identify local regions with chances of severe thunderstorms.

The atmospheric temperature and moisture profiles provide temperature and moisture readings at twenty different levels between the surface of the earth and the top of the atmosphere under cloud-free conditions. These profiles provide basic information about how the atmosphere itself is constructed. This basic understanding of the atmosphere, or baseline, is necessary for both fundamental studies of climate and the greenhouse effect.
When these four portions are pulled together into the Atmospheric Profile product, the result is a data set that will have many powerful and far-reaching applications and will enhance our understanding the atmosphere. Further, understanding how our atmosphere works is an important step in understanding how our planet functions as a whole – from life to land to ocean to atmosphere.

 

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Curator: Brandon Maccherone
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