Water vapor is a small but significant constituent of the atmosphere, warming the planet due to the greenhouse effect and condensing to form clouds. As moisture-laden air rises, the relative humidity increases until it saturates the air, at which time precipitation occurs. If the uplift of air is due to large-scale atmospheric motion, then the precipitation is called large-scale, or dynamic. This animation shows the large-scale precipitation for the whole globe from September 1, 2004, through September 5, 2004, during the period of Hurricane Frances in the western Atlantic Ocean and Typhoon Songda in the western Pacific Ocean. Large-scale precipitation tends to be continuous and to come from decks of stratus clouds rather than from thunderstorms.
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