New Insights into Annual and Semiannual Cycles of Sea Level Pressure

Abstract

Sea level pressure (SLP) acts, on the one hand, as a ''bridge parameter'' to which geophysical properties at the air-sea interface (e.g., wind stress and sea surface height) are linked, and on the other hand, as an ''index parameter'' by which major atmospheric oscillations, including the well-known Southern Oscillation, are defined. Using 144 yr (1854-1997) of extended reconstructed SLP data, seasonal patterns of its variability are reinvestigated in detail. New features on fundamental structure of its annual and semiannual cycles are revealed in two aspects. First, the spatiotemporal patterns of yearly and half-yearly SLPs are basically determined by a network of ''amphidromes,'' which are surrounded by rotational variations. Fourteen cyclonic and anticyclonic annual SLP amphidromes (half each and often in pair) are found in the global ocean, while the numbers of the two types of semiannual amphidrome are 11 and 9, respectively. The second dominant feature in SLP variability is the pattern of oscillation or seesaw for both annual and semiannual components. At least eight oscillation zones are identified for the annual cycle, which can be categorized into a boreal winter mode and an austral winter mode. As for the semiannual cycle, the seesaw pattern is geographically divided into three regimes: the North Pacific regime, the North Atlantic regime, and the Southern Ocean regime. These findings serve as a new contribution to characterizing and understanding the seasonality of the global ocean-atmosphere system.

Systematic Error Mitigation in DORIS‐Derived Geocenter Motion

“…Annual variations surround the main continental regions of active terrestrial hydrological processes. Half‐yearly variations are coherent and in phase with reported atmospheric pressure semiannual oscillations over northern Greenland and East Antarctica in Chen et al (, their Figure 3). Understanding the physical sources of the full spectrum of geocenter variations should be a major goal in the future analysis.…”

Radiational tides: their double-counting in storm surge forecasts and contribution to the Highest Astronomical Tide

“…4 indicates typical changes. In the Baltic, the seasonal change is wind forced, but elsewhere it is consistent with the annual and semi-annual cycles in sea-level atmospheric pressure (Chen et al, 2012). MS f is affected by the surge component, as a side effect of the interaction between M 2 and S 2 .…”

Annual and semiannual cycles of midlatitude near-surface temperature and tropospheric baroclinicity: reanalysis data and AOGCM simulations

“…Previous studies provided evidences for some kind of midwinter suppression of baroclinic wave activity in the NH Pacific, with large variances during spring and autumn (see Nakamura, 1992, and references therein). This finding was supported by the harmonic analysis of air temperature and sea level pressure fields carried out by Yashayaev and Zveryaev (2001), by observations as illustrated by Chang (2003), or the recent study by Chen et al (2012).…”