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Multidecadal Regime Shifts in U.S. Streamflow, Precipitation, and Temperature ...

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    Multidecadal Regime Shifts in U.S. Streamflow, Precipitation, and Temperature at the End of the Twentieth Century Steven A. Mauget U.S. Department of
    Message 1 of 1 , Feb 2, 2004
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      Multidecadal Regime Shifts in U.S. Streamflow, Precipitation,
      and Temperature at the End of the Twentieth Century
      Steven A. Mauget
      U.S. Department of Agriculture�Agricultural Research Service,
      USDA Plant Stress and Water Conservation Laboratory,
      Lubbock, Texas ( 13 May 2003)
      Journal of Climate: Vol. 16, No. 23, pp. 3905�3916.
      ABSTRACT
      Intra- to multidecadal variation in annual streamflow, precipitation, and
      temperature over the continental United States are evaluated here through
      the calculation of Mann�Whitney U statistics over running-time windows of
      6�30-yr duration. When this method is demonstrated on time series of
      nationally averaged annual precipitation and mean temperature during
      1896�2001, it reveals that 8 of the 10 wettest years occurred during the
      last 29 yr of that 106-yr period, and 6 of the 10 warmest years during
      the last 16. Both of these results indicate highly significant departures
      from long-term stationarity in U.S. climate at the end of the twentieth
      century. The effects of increased wetness are primarily evident in the
      central and eastern United States, while evidence of warmth is found
      throughout the Rocky Mountain region and in the West. Analysis of annual
      streamflow records across the United States during 1939�98 shows broadly
      consistent effects. Initial evidence of the recent wet regime is most
      apparent in eastern streamflow, which shows a clear pattern of
      high-ranked mean annual values during the 1970s. Over the midwestern
      states, a coherent pattern of high-ranked annual flow is found during
      multidecadal periods beginning during the late 1960s and early 1970s and
      ending in either 1997 or 1998. During the late 1980s and early 1990s, a
      significant incidence of low-ranked annual flow conditions throughout the
      West was roughly
      coincident with the onset of western warmth during the mid-1980s.
      Evidence of highly significant transitions to wetter and warmer
      conditions nationally, and consistent variation in streamflow analyses,
      suggests that increased hydrological surplus in the central and eastern
      United States and increased hydrological deficit in the West may be
      representative of the initial stages of climate change over the
      continental United States.

      Steve Mauget
      USDA - Agricultural Research Service
      3810 4th Street
      Lubbock, Texas, 79415
      1-806-723-5237





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