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The planetary waves form at preferred locations both in the North and South Pacific Ocean, and the teleconnection pattern is established within 2–6 weeks. During El Niño events, deep convection and heat transfer to the troposphere is enhanced over the anomalously warm sea surface temperature, this ENSO-related tropical forcing generates Rossby waves that propagate poleward and eastward and are subsequently refracted back from the pole to the tropics. Additionally sea surface temperature anomalies have some winter to winter persistence due to the reemergence mechanism.ĮNSO teleconnections, the atmospheric bridge ĮNSO can influence the global circulation pattern thousands of kilometers away from the equatorial Pacific through the "atmospheric bridge". Thus, unlike El Niño–Southern Oscillation (ENSO), the PDO is not a single physical mode of ocean variability, but rather the sum of several processes with different dynamic origins.Īt inter-annual time scales the PDO index is reconstructed as the sum of random and ENSO induced variability in the Aleutian Low, whereas on decadal timescales ENSO teleconnections, stochastic atmospheric forcing and changes in the North Pacific oceanic gyre circulation contribute approximately equally. Several studies have indicated that the PDO index can be reconstructed as the superimposition of tropical forcing and extra-tropical processes. A PDO 'signal' has been reconstructed as far back as 1661 through tree-ring chronologies in the Baja California area. This PDO index is the standardized principal component time series. The Pacific decadal oscillation index is the leading empirical orthogonal function (EOF) of monthly sea surface temperature anomalies ( SST-A) over the North Pacific (poleward of 20°N) after the global average sea surface temperature has been removed. Hare, who noticed it while studying salmon production pattern results in 1997. The Pacific decadal oscillation was named by Steven R. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.ĭuring a " warm", or "positive", phase, the west Pacific becomes cooler and part of the eastern ocean warms during a "cool", or "negative", phase, the opposite pattern occurs. There is evidence of reversals in the prevailing polarity (meaning changes in cool surface waters versus warm surface waters within the region) of the oscillation occurring around 1925, 1947, and 1977 the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales (meaning time periods of a few years to as much as time periods of multiple decades). The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Such an EOS has previously been used to model liquid nitromethane.The Pacific decadal oscillation ( PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. This corresponds to the limiting case of two temperature scales with one of the scales in the high temperature limit. If the EOS domain does not include the zero isotherm, then a specific heat with a single temperature scale leads to a generalization of the Mie-Gr¨uneisen EOS in which the pressure is linear in both the specific energy and the temperature. In addition we show that if the more » domain of the EOS extends to T = 0 and the specific heat vanishes on the zero isotherm then a function of only V is equivalent to a specific heat with a single temperature scale. A complete extension is uniquely determined by the temperature dependence of the specific heat at a fixed reference density. Thermodynamic consistency requires that the specific heat is a function of a single scaled-temperature. This enables the extension to a complete EOS. Expressions are derived for isentropes and isotherms. It is an incomplete EOS characterized by a Gr¨uneisen coefficient, = -V, that is a function of only V. The Mie-Gruneisen equation of state (EOS) is frequently used in hydro simulations to model solids at high pressure (up to a few Mb). Finally, the assumed temperature dependence of the Steinberg-Guinan strength model obtained from scaling with the bulk shear modulus is examined at ambient pressure. = shear modulus becomes negative indicating the onset of unexpectedly strong anharmonic effects.