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Grouping ENSO: The ENSO -related West Pacific SST Gradient and Associated Climate Modifications

Grouping ENSO: The ENSO -related West Pacific SST Gradient and Associated Climate Modifications. Andy Hoell UCSB Climate Hazards Group hoell@geog.ucsb.edu. Overview. Identification of the ENSO-related west Pacific SST Gradient (WPG) Quantification of WPG Trends of WPG

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Grouping ENSO: The ENSO -related West Pacific SST Gradient and Associated Climate Modifications

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  1. Grouping ENSO:The ENSO-related West Pacific SST Gradient and Associated Climate Modifications Andy Hoell UCSB Climate Hazards Group hoell@geog.ucsb.edu

  2. Overview • Identification of the ENSO-related west Pacific SST Gradient (WPG) • Quantification of WPG • Trends of WPG • Relationship of ENSO-related WPG with the Global Climate • Global Precipitation • African Precipitation • African Precipitation: Competing Factors

  3. Identification of ENSO-related WPG (a) The canonical ENSO-related SST pattern is identified using the leading principal component of SST (b) Equatorial average SST indicates an out-of-phase relationship between west and central Pacific SST separated by a gradient over 150°E-170°E Hoell and Funk (2012), The Anomalous Circulation Associated with the ENSO-related West Pacific Sea Surface Temperature Gradient, in review, J. Climate

  4. Quantification of ENSO-related WPG ENSO events are quantified using the leading principal component of SST WPG = standardized(N4 – WP) Hoell and Funk (2012), The Anomalous Circulation Associated with the ENSO-related West Pacific Sea Surface Temperature Gradient, in review, J. Climate

  5. Trends in ENSO-related WPG The second principal component of SST indicates an intensified WPG due to warming WP SST relative to the CP 10-year running means of N4, WP and WPG indicate a recent sharp change in WPG as a result of rapidly warming WP Hoell and Funk (2012), The Anomalous Circulation Associated with the ENSO-related West Pacific Sea Surface Temperature Gradient, in revision, J. Climate

  6. Overview • Identification of the ENSO-related west Pacific SST Gradient (WPG) • Quantification of WPG • Trends of WPG • Relationship of ENSO-related WPG with the Global Climate • Global Precipitation • African Precipitation • African Precipitation: Competing Factors

  7. La Nina-WPG and Global Changes

  8. Strong WPG La Nina Precipitation Hoell et al. (2012), Global Drought and the ENSO-related West Pacific Sea Surface Temperature Gradient, In Prep, J. Climate

  9. Strong WPG La Nina Precipitation Hoell et al. (2012), Global Drought and the ENSO-related West Pacific Sea Surface Temperature Gradient, In Prep, J. Climate

  10. ENSO and JFM Southern Africa Precipitation Strong WPG La Nina Mixed El Nino Understand the mechanisms by which strong WPG La Nina influence southern Africa precipitation Improve understanding of the links between El Nino-related SST patterns and southern Africa precipitation Hoell et al. (2012), ENSO Diversity and Summertime Southern Africa Precipitation, In Prep.

  11. Overview • Identification of the ENSO-related west Pacific SST Gradient (WPG) • Quantification of WPG • Trends of WPG • Relationship of ENSO-related WPG with the Global Climate • Global Precipitation • African Precipitation • African Precipitation: Competing Factors

  12. Competing Factors – JFM 2008 Strong WPG La Nina events were associated with the top 4 southern Africa JFM pluvials Though JFM 2008 was a strong WPG La Nina, southern Africa precipitation was mixed We need to consider competing factors with ENSO, such as the MJO, if we are to improve sub-seasonal to seasonal precipitation forecasts

  13. Competing Factors JFM 2008 Southern Africa was mixed despite strong WPG La Nina MJO-related precipitation dries southern Africa for nearly one month Hoell et al. (2012), Disruptions of the ENSO teleconnection by the MJO, In Prep, GRL

  14. Summary • ENSO events are oftentimes accompanied by a gradient in SST between the central and west Pacific Ocean (WPG) • Strong WPG La Nina events are related to strong global circulation and precipitation modifications • The recent rapid warming of the west Pacific relative to the central Pacific has led to an increased WPG during La Nina • Strong WPG La Nina appears to have predictive capabilities for southern Africa precipitation during JFM. However, this is not the case for El Nino • While strong WPG La Nina oftentimes lead to southern Africa pluvials during JFM, other factors such as the MJO influence seasonal precipitation and must be closely considered

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