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Scott J. Weaver Megan E. Linkin

Scott J. Weaver Megan E. Linkin. Contemporaneous and Antecedent Links of Atlantic and Pacific Circulation Features with North American Hydroclimate: Structure and Interannual Variability. Link to Mid-term presentation.

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Scott J. Weaver Megan E. Linkin

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  1. Scott J. Weaver Megan E. Linkin Contemporaneous and Antecedent Links of Atlantic and Pacific Circulation Features with North American Hydroclimate: Structure and Interannual Variability Link to Mid-term presentation

  2. Attempted to ascertain the leading modes of variability in both MAM and JJA Obtain spatio-temporal structure of these patterns Determine antecedent links between spring and summer Motivation/Objective • Natural modes of variability in both the Atlantic and Pacific basins generate anomalous large scale circulation patterns. • These patterns can result in anomalous temperature and moisture advection over North America.

  3. Regressed multiple hydroclimate variables to determine remote influences on soil moisture, moisture flux convergence and precipitation NCEP/NCAR monthly reanalysis used to diagnose circulation NARR used to diagnose hydroclimate anomalies Methodology/Data • Performed traditional and extended empirical orthogonal function analysis (EOF and EEOF) on sea level pressure anomalies over each individual ocean basin • Regressed geopotential height anomalies to establish circulation anomalies

  4. Springtime positive NAO phase characterized by broad longitudinal ridge Would suppress precipitation and result in anomalously warm temperatures Also displaced jet stream further north Antecedent condition for summertime drought In 1988, NAO was positive during MAM Courtesy of CPC/NOAA

  5. Ridge suppressed precipitation during summer months An already dry spring was followed by a dry summer Land surface processes served to exacerbate the situation Summer 1988 • ENSO ending a cycle • Shifts in convection centers in tropics induced an anomalous wave train in the upper troposphere • Resulted in a ridge positioned over the Great Plains

  6. Warm ENSO events cause an increase in precipitation in Great Plains region. During JJA1993, a long warm ENSO event was occurring (1992-1994) Nino3.4 index was greater than zero from 1990-1995 Resulted in anomalously large amounts of precipitation over central US Courtesy of CPC/NOAA

  7. NAO index was negative both spring and summer of 1993 Nothing to suppress anomalous precipitation that was occurring Summer 1993 • Persistent ENSO event resulted in numerous seasons with anomalous precipitation • Plenty of soil moisture present from past seasons • Continuing warm ENSO conditions supplied dynamics for enhanced precipitation

  8. Future Work • Assess Pacific Basin effect on MAM hydroclimate • Perform statistical analysis to determine if patterns and teleconnections are significant • Investigate possible potential predictability of any mode (“Shanghai express”) due to its relationship with SST

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