The EOS AQUA AMSR-E measures geophysical parameters supporting several global change science and monitoring efforts, including precipitation, oceanic water vapor, cloud water, near-surface wind speed, sea surface temperature, soil moisture, snow cover, and sea ice parameters. All of these measurements are critical to understanding the Earth's climate.
Water vapor is the Earth's primary greenhouse gas, essential to keeping the Earth habitable. Since it contributes the most to future projections of global warming, it is critical to understand how it varies naturally in the Earth system. The evaporation of water from the surface carries away excess heat, preventing unbearably hot temperatures in most regions. The image to the left is a monthly composite of the AMSR-E water vapor product for the month of September 2005, courtesy of Remote Sensing Systems.
Almost all of the water
that evaporates eventually returns to the Earth's Surface as precipitation.
In the process of precipitation formation, heat that was absorbed during
evaporation is released to the atmosphere. This process provides over
half of the energy needed for the global atmospheric circulation and is
the prime mechanism for transferring the effects of local climate anomalies
such as El Nino to other regions. Cloud water reflects sunlight back out
to space, cooling the Earth. Over the ocean, the AMSR-E microwave frequencies
can probe through smaller cloud particles to measure the microwave emission
from the larger raindrops. Over land, the AMSR-E can measure the scattering
effects of large ice particles which later melt to form raindrops. These
measurements, though an indirect measure of rainfall intensity, are converted
to a rain rate with the help of cloud models.
Over the ocean, AMSR-E provides sea surface temperatures (SST) through most types of cloud cover, supplementing infrared based measurements of SST that are restricted to cloud-free areas. SST fluctuations are known to have a profound impact on weather patterns across the globe, and the AMSR-E all weather capability provides a significant improvement in our ability to monitor SST's and the processes controlling them.
Ocean surface roughness is also measured by AMSR-E, which will be converted into a near-surface wind speed. These winds are one important component of how much water is evaporated from the surface of the ocean. The winds help to maintain the water vapor content of the atmosphere while precipitation continually removes it.
Soil moisture is a key state variable in land surface hydrology. It controls the proportion of rainfall that percolates, runs off, or evaporates from land. Soil moisture also enables photosynthesis in plants that use solar energy to convert carbon dioxide and water into the oxygen and food necessary for animal life on Earth. Soil moisture is important for maintaining crop and vegetation health, and its monitoring on a global basis will allow drought prone areas to be monitored for signs of drought
Sea Ice reflects sunlight away from the Earth, but it also helps the ocean to retain thermal energy by restricting evaporation and other heat transfers from the ocean surface. Monitoring of sea ice parameters, such as ice type and extent, is necessary to understand how this frozen blanket over the ocean acts to change climate through its ability to insulate the water against heat loss to the frigid atmosphere above it, and through its ability to reflect sunlight that would otherwise warm the ocean.
Snow cover over sea ice further restricts
heat loss from the ocean. Similarly, snow cover over land reduces the
amount of sunlight absorbed by the Earth, while also limiting the flow
of heat from the ground to the atmosphere. Snow cover is also an important
part of the land hydrology and provides a yearly replenishment of water
resources in many regions. In much the same
way as the AMSR-E can see large ice particles in the upper reaches of
rain systems, it also measures the scattering effects of snow cover. These
measurements are empirically related to snow cover depth and water content
based upon field measurements. (photo: Extracting ice cores in a meltpond
area of a multiyear floe. Courtesy of J. Maslanik, CU.)
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