Event Title

The missing PDO-ENSO teleconnection explaining weather variability in the United States Intermountain West

Presenter Information

Boniface Fosu
Shih-Yu Wang

Location

Eccles Conference Center

Event Website

http://water.usu.edu

Start Date

4-1-2014 3:20 PM

End Date

4-1-2014 3:40 PM

Description

Understanding the variability and precipitation regimes in the United States Intermountain West is of utmost importance for agriculture planning and water management. Although the accuracy of weather and climate models in predicting precipitation has significantly improved over the last three decades, overall model performance in the United States Intermountain West (U.S. IMW) is weaker and less accurate when compared to the model-skill for the rest of the country. In this study, we show that the Pacific Decadal Oscillation (PDO) can be used to facilitate forecasting of precipitation regimes in the U.S. IMW. A linear analysis of a twenty-years sliding (SCORR) correlation between the Palmer Drought and Severity Index (PDSI) and the Nino 3.4 index bears a great resemblance to the PDO signal constructed from tree ring data from 1930 to 2000. It was found that positive PDO phases correspond to wet periods in the U.S. IMW whiles the reversed PDO pattern introduces a dry regime. A similar analysis using historical simulation of the Community Earth System Model (CESM), a fully coupled global climate model reveals a pattern consistent with the ones observed in PDO-SCORR analyses. But here, precipitation anomalies are used rather than the PDSI index. A difference in streamfunction composite between El Nino and La Nina years is computed for two historical periods: the PDO cold phase (1784-1864) during which twice as many La Nina’s were observed, and the PDO warm phase (1874-1954) during which twice as many El Nino’s were observed. The result shows a wave train that transports moisture to the entire South-Western U.S. during El Nino years.

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Apr 1st, 3:20 PM Apr 1st, 3:40 PM

The missing PDO-ENSO teleconnection explaining weather variability in the United States Intermountain West

Eccles Conference Center

Understanding the variability and precipitation regimes in the United States Intermountain West is of utmost importance for agriculture planning and water management. Although the accuracy of weather and climate models in predicting precipitation has significantly improved over the last three decades, overall model performance in the United States Intermountain West (U.S. IMW) is weaker and less accurate when compared to the model-skill for the rest of the country. In this study, we show that the Pacific Decadal Oscillation (PDO) can be used to facilitate forecasting of precipitation regimes in the U.S. IMW. A linear analysis of a twenty-years sliding (SCORR) correlation between the Palmer Drought and Severity Index (PDSI) and the Nino 3.4 index bears a great resemblance to the PDO signal constructed from tree ring data from 1930 to 2000. It was found that positive PDO phases correspond to wet periods in the U.S. IMW whiles the reversed PDO pattern introduces a dry regime. A similar analysis using historical simulation of the Community Earth System Model (CESM), a fully coupled global climate model reveals a pattern consistent with the ones observed in PDO-SCORR analyses. But here, precipitation anomalies are used rather than the PDSI index. A difference in streamfunction composite between El Nino and La Nina years is computed for two historical periods: the PDO cold phase (1784-1864) during which twice as many La Nina’s were observed, and the PDO warm phase (1874-1954) during which twice as many El Nino’s were observed. The result shows a wave train that transports moisture to the entire South-Western U.S. during El Nino years.

https://digitalcommons.usu.edu/runoff/2014/2014Abstracts/10