Role of Multiple-Level Tropospheric Circulations in Forcing ENSO Winter Precipitation Anomalies

Abstract Regionally organized winter (DJF) precipitation anomalies over North America are presented in association with cold and warm phases of the El Nino–Southern Oscillation. Variations in low-level flow from moisture sources and in upper-level dynamic properties are diagnosed for each anomalous precipitation region using DJF composites of upper- and lower-tropospheric winds, sea level pressure, divergence, and vorticity advection. Variance analysis determines which precipitation and circulation patterns are robust and evaluates the predictability of the extreme phase composites with respect to the climatology. In cold phases, the Pacific Northwest and the lower Mississippi Valley regions have above-normal precipitation totals. The heavier precipitation over the Pacific Northwest is the result of a multilevel onshore flow forced by an amplified Pacific high off the California coast and a single zonal upper-tropospheric jet. In the Lower Mississippi and Tennessee Valleys, the equatorward entrance region...

[1]  A. J. Troup,et al.  The ‘southern oscillation’ , 1965 .

[2]  A. Shabbar,et al.  Canadian Precipitation Patterns Associated with the Southern Oscillation , 1997 .

[3]  R. A. Madden,et al.  The Southern Oscillation. Part I: Global Associations with Pressure and Temperature in Northern Winter , 1981 .

[4]  Russell S. Vose,et al.  The Global Historical Climatology Network: Long-term monthly temperature, precipitation, sea level pressure, and station pressure data , 1992 .

[5]  J. Namias,et al.  CONFLUENCE THEORY OF THE HIGH TROPOSPHERIC JET STREAM , 1949 .

[6]  Michael H. Glantz,et al.  Currents of Change: El Niño's Impact on Climate and Society , 1996 .

[7]  Henry F. Diaz,et al.  Global climatic anomalies associated with extremes in the Southern Oscillation , 1989 .

[8]  D. Bromwich,et al.  Evolution of the Tropospheric Split Jet over the South Pacific Ocean during the 1986–89 ENSO Cycle , 1996 .

[9]  G. K. Bhattacharyya,et al.  Statistical Concepts And Methods , 1978 .

[10]  K. Mo,et al.  The 200-mb Climatological Vorticity Budget during 1986–1989 as Revealed by NMC Analyses , 1993 .

[11]  E. Evan Brown.  Federal Republic of Germany (West Germany) , 1983 .

[12]  J. O'Brien,et al.  Marginal Probabilities of the Extremes of ENSO Events for Temperature and Precipitation in the Southeastern United States , 1994 .

[13]  Chester F. Ropelewski,et al.  Quantifying Southern Oscillation-Precipitation Relationships , 1996 .

[14]  J. O'Brien,et al.  Low-Frequency Variability of the Equatorial Pacific Ocean Using a New Pseudostress Dataset: 1930–1989 , 1995 .

[15]  L. Bengtsson,et al.  On the impact of the El Niño/Southern Oscillation phenomenon on the atmospheric circulation in the northern hemisphere extratropics , 1996 .

[16]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[17]  H. Diaz,et al.  Relationships between extremes of the Southern oscillation and the winter climate of the Anglo‐American Pacific Coast , 1986 .

[18]  W. Emery,et al.  Atmospheric forcing of interannual variability in the northeast Pacific Ocean: Connections with El Niño , 1985 .

[19]  H. Loon,et al.  The Southern Oscillation. Part II: Associations with Changes in the Middle Troposphere in the Northern Winter , 1981 .