The atmosphere is in constant change as air moves around the globe, causing solar energy to take on different values across the Earth as it rotates. One of the significant effects from this seemingly chaotic situation is the creation and dissipation of clouds and fog. Figure 7.1 illustrates examples of both. To understand what is happening, we need atmospheric measurements frequently, and at several locations, to get a feel for the statistical nature of atmospheric physics. Although radiosondes attempt to do this, we cannot afford measurements with these entities at the level needed for statistical significance. Fortunately, over the last few decades, satellite remote sensing of the atmosphere has emerged as one of the most powerful techniques for observing and quantifying global atmospheric characteristics. Available systems include the spaceborne precipitation radar, or microwave imager, on NASA’s Global Precipitation Mission (GPM) satellite, and multi-spectral imaging radiometers such as MODIS, MISR, and ASTER on NASA’s Terra satellite. These satellites can measure the changing patterns of vegetation growth, snow cover, oceans, and land use at frequent time intervals.
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