Cloud layer seen from an airplane
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Clouds play a major role in determining the planet's solar and longwave energy balance and, thus, are important in governing the Earth's climate. SAGE III will provide measurements of mid and high level clouds including thin or "sub-visual" clouds that are not detectable by nadir-viewing passive remote sensors. These observations are important because:
While low clouds primarily reflect incoming solar radiation back into space (acting to cool the planet), mid and high level clouds enhance the "greenhouse" effect by trapping infrared radiation (acting to warm the planet).
The presence of thin cloud near the tropopause may play a significant role in heterogeneous chemical processes that lead to ozone destruction in mid-latitudes.
Clouds play an important role in feedback processes (such as changes in altitude or amount of cloud) associated with climate change. Currently neither the sign nor magnitude is known for the climate impact of cloud response to changes in radiative processes brought about by increasing levels of human-derived greenhouse gases (like carbon dioxide) and aerosols.
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