Event Title

Intermountain Hydroclimate as a Quadrature Amplitude Modulation from Pacific Quasi-Decadal Oscillation

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-2-2009 9:30 AM

End Date

4-2-2009 9:35 AM

Description

The hydroclimate of the lntermountain Region poses two challenges: 1) it is located in a marginal zone from direct impacts of the El Nino-Southern Oscillation (ENSO), and 2) the precipitation and other hydrological variables exhibit pronounced 'cycles' in the quasi-decadal frequency (-12 yrs). The quasi-decadal oscillation (QDO) is a known signal in the Pacific Ocean and the ENSO/ENSO-related activities, but the QDO in the lntermountain precipitation does not correlate with the QDO in the Pacific. On the other hand, the lake level variation of the Great Salt Lake is very coherent alongside the Pacific QDO, suggesting that the precipitation is linked to the Pacific QDO. Our analysis indicates that the lntermountain precipitation QDO consistently lags the Pacific QDO by about 3 yrs. The Pacific QDO not only forms an ENSO-like teleconnection pattern, it also triggers a very different teleconnection pattern during the rising and falling transition phases. ln contrast to the long-wave Pacific-North America pattern, this "transition-phase" teleconnection emerges as a short-wave train emanating from the tropical Western Pacific across the midlatiude North Pacific. The short-wave train connects to the northeast Pacific forming an anomalous cell in the Gulf of Alaska and an opposite-phase cell off the U.S. West Coast. This circulation dipole modulates the jet stream entering the lntermountain Region and affects the synoptic transient activity that produces rainfall. The volumetric change of the Great Salt Lake follows the precipitation variation, so the coherence between the Great Salt Lake level the Pacific QDO supports the lagged coupling between the lntermountain precipitation and the Pacific QDO. A quadrature amplitude modulation of the Pacific QDO on the lntermountain hydroclimate is thus proposed: The Pacific QDO evolves into a transition phase in between the warm and cool phases, while the transition-phase teleconnection modulates the lntermountain precipitation and generates the QDO in the hydrological cycle. The hydrological QDO is then transferred to the volumetric change of the Great Salt Lake and subsequently to the lake level. Such processes amount to an approximate 6 year response for the Great Salt Lake level to react to the Pacific QDO, creating a half-phase delay of the Great Salt Lake level rise (decline) to the warm-phase (cool-phase) Pacific QDO. As a result, monitoring the Pacific QDO (or the quasi-decadal ENSO activity) may help long-term prediction of the lntermountain hydroclimate.

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Apr 2nd, 9:30 AM Apr 2nd, 9:35 AM

Intermountain Hydroclimate as a Quadrature Amplitude Modulation from Pacific Quasi-Decadal Oscillation

Eccles Conference Center

The hydroclimate of the lntermountain Region poses two challenges: 1) it is located in a marginal zone from direct impacts of the El Nino-Southern Oscillation (ENSO), and 2) the precipitation and other hydrological variables exhibit pronounced 'cycles' in the quasi-decadal frequency (-12 yrs). The quasi-decadal oscillation (QDO) is a known signal in the Pacific Ocean and the ENSO/ENSO-related activities, but the QDO in the lntermountain precipitation does not correlate with the QDO in the Pacific. On the other hand, the lake level variation of the Great Salt Lake is very coherent alongside the Pacific QDO, suggesting that the precipitation is linked to the Pacific QDO. Our analysis indicates that the lntermountain precipitation QDO consistently lags the Pacific QDO by about 3 yrs. The Pacific QDO not only forms an ENSO-like teleconnection pattern, it also triggers a very different teleconnection pattern during the rising and falling transition phases. ln contrast to the long-wave Pacific-North America pattern, this "transition-phase" teleconnection emerges as a short-wave train emanating from the tropical Western Pacific across the midlatiude North Pacific. The short-wave train connects to the northeast Pacific forming an anomalous cell in the Gulf of Alaska and an opposite-phase cell off the U.S. West Coast. This circulation dipole modulates the jet stream entering the lntermountain Region and affects the synoptic transient activity that produces rainfall. The volumetric change of the Great Salt Lake follows the precipitation variation, so the coherence between the Great Salt Lake level the Pacific QDO supports the lagged coupling between the lntermountain precipitation and the Pacific QDO. A quadrature amplitude modulation of the Pacific QDO on the lntermountain hydroclimate is thus proposed: The Pacific QDO evolves into a transition phase in between the warm and cool phases, while the transition-phase teleconnection modulates the lntermountain precipitation and generates the QDO in the hydrological cycle. The hydrological QDO is then transferred to the volumetric change of the Great Salt Lake and subsequently to the lake level. Such processes amount to an approximate 6 year response for the Great Salt Lake level to react to the Pacific QDO, creating a half-phase delay of the Great Salt Lake level rise (decline) to the warm-phase (cool-phase) Pacific QDO. As a result, monitoring the Pacific QDO (or the quasi-decadal ENSO activity) may help long-term prediction of the lntermountain hydroclimate.

https://digitalcommons.usu.edu/runoff/2009/AllPosters/19