Effect of high-frequency wind on intraseasonal SST variabilities over the mid-latitude North Pacific region during boreal summer
The effect of high-frequency (period <20 days) wind on the intraseasonal (period 20–100 days) sea surface temperature (SST) anomalies over the mid-latitude North Pacific region (35°–45°N, 160°E–170°W) during boreal summer was examined through the diagnosis of reanalysis data and numerical experiments. The reanalysis data diagnosis shows that the near-surface high-frequency (HF) wind is weaker (stronger) during the intraseasonal SST warming (cooling) phase. The phase-dependent amplitude of HF wind is controled by the strength change of the upper-tropospheric westerly jet stream. Because the magnitude of the HF wind over the target region shows significantly positive correlation with the total wind speed, a weaker (higher) HF wind in the SST warming (cooling) phase tends to decrease (increase) total wind speed, which can further suppress (enhance) upward surface latent heat and sensible heat fluxes and strengthen the intraseasonal SST variability. The numerical experiments with an oceanic general circulation model demonstrate that the HF wind can amplify the intraseasonal SST variability over the target region mainly through nonlinearly rectifying intraseasonal surface latent and sensible heat fluxes. The HF wind can explain about 20 % of the intraseasonal SST variability in the target region.
KeywordsSea surface temperature Intraseasonal oscillation High frequency wind Air-sea interaction Upscale feedback North Pacific
This study was supported by China National 973 Project 2015CB453200, NSFC grants 41475084, ONR Grant N00014-1210450, and by the International Pacific Research Center that is sponsored by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). We thank the European Center for Medium-Range Weather Forecast for providing reanalysis data available on their homepage. This is SOEST contribution number 9264, IPRC contribution number 1099, and ESMC contribution 033.
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