The Atlantic multidecadal oscillation and extreme daily precipitation over the US and Mexico during the hurricane season |
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Authors: | Scott Curtis |
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Institution: | (1) Atmospheric Science Laboratory, Department of Geography, East Carolina University, Brewster A232, Greenville, NC 27858, USA |
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Abstract: | The tail of the distribution of daily precipitation for August–September–October was examined over the United States and Mexico
in relation to the Atlantic Multidecadal Oscillation (AMO). As expected from previous studies linking the AMO to hurricane
activity, Florida and the coastal Southeast US showed an increase in precipitation intensity when the Atlantic was in a warm
phase (AMO+). Also during AMO+ Northwest Mexico was dry and exhibited a reduction of extreme events and the Mid-Atlantic Appalachian
Mountains showed evidence of an increase in heavy precipitation compared to when the Atlantic was cool. It is proposed that
the aforementioned decadal variations in extreme rainfall are forced by changes in the large-scale surface winds and air temperature
in conjunction with the AMO. Namely, an anomalous cyclonic circulation is observed off the Southeast coast, leading to a reduction
of moisture flux into the decaying North American monsoon, and an increase in moisture flux into the Mid-Atlantic. Further,
the Mid-Atlantic shows a relatively strong increase in the mid-tropospheric lapse rate. Thus, the unique combination of low-level
humidity, potential instability, and elevated topography are consistent with an enhanced risk of intense rainfall during AMO+. |
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Keywords: | Atlantic multidecadal oscillation Precipitation Extremes Drought Atmospheric circulation |
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