Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer

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  • Boreal summer intraseasonal (30–90-day time scale) sea surface temperature (SST) variability in the east Pacific warm pool is examined using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) sea surface temperatures during 1998–2005. Intraseasonal SST variance maximizes at two locations in the warm pool: in the vicinity of 9°N, 92°W near the Costa Rica Dome and near the northern edge of the warm pool in the vicinity of 19°N, 108°W. Both locations exhibit a significant spectral peak at 50–60-day periods, time scales characteristic of the Madden–Julian oscillation (MJO). Complex empirical orthogonal function (CEOF) and spectra coherence analyses are used to show that boreal summer intraseasonal SST anomalies are coherent with precipitation anomalies across the east Pacific warm pool. Spatial variations of phase are modest across the warm pool, although evidence exists for the northward progression of intraseasonal SST and precipitation anomalies. Intraseasonal SSTs at the north edge of the warm pool lag those in the vicinity of the Costa Rica Dome by about 1 week. The MJO explains 30%–40% of the variance of intraseasonal SST anomalies in the east Pacific warm pool during boreal summer. Peak-to-peak SST variations of 0.8°–1.0°C occur during MJO events. SST is approximately in quadrature with MJO precipitation, with suppressed (enhanced) MJO precipitation anomalies leading positive (negative) SST anomalies by 7–10 days. Consistent with the CEOF and coherence analyses, MJO-related SST and precipitation anomalies near the Costa Rica Dome lead those at the northern edge of the warm pool by about 1 week.
  • Keywords: Warm pool, Tropics, Madden-Julian oscillation, Sea surface temperature
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  • Maloney, Eric D., Dudley B. Chelton, Steven K. Esbensen, 2008: Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer. Journal of Climate, 21, 4149–4167.
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  • 21
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  • 17
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  • This research was prepared by Eric Maloney and Steve Esbensen under Award NA05OAR4310006 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. Eric Maloney was also supported by the Climate and Large-Scale Dynamics Program of the National Science Foundation under Grant ATM-0632341. Dudley Chelton was supported by NASA Grant NNG05GN98G.
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