On the origin of the tropical Atlantic decadal oscillation based on the analysis of the ICOADS

Abstract

SUMMARYFrom an analysis of the International Comprehensive Ocean-Atmosphere Data Set, we were able to confirm salient features of the tropical Atlantic decadal oscillation illustrated in previous works. These features include antisymmetric behaviour of surface air pressure and sea surface temperature with two centres of action residing in the tropical North and South Atlantic Oceans. In addition to the recognized features of the oscillation, we found a new aspect: the principal mechanism regulating the oscillation differs between the north and south centres of action. Decadal components of the relative humidity time series show a maximum value of lag cross-correlation at a lag of −2 years. Such a temporal evolution was irrespective of the centres of action and the reference time series. The two reference series employed are the sunspot numbers and the southerlies over the western equatorial Atlantic. Associated with this, statistically significant phase shifts between the decadal components of variables exist, especially in the tropical North Atlantic Ocean. For the decadal oscillation, relative humidity change was dominated by specific humidity change over the tropical North Atlantic and by air temperature change over the tropical South Atlantic. For the frequency band of the solar cycle, the variation of relative humidity seemed to amplify the Earth's response to the sun's radiation changes that had previously been considered too small to affect the Earth's climate. By incorporating our new findings with the known features of the oscillation, we can suggest that the variability of solar radiation may be crucial as an originator, or at least as a regulator, of the oscillation in combination with the climate distribution of clouds and water vapour over the tropical Atlantic.

A Coupled Air–Sea Response Mechanism to Solar Forcing in the Pacific Region

“…Analyses of observations have suggested that the effect on the earth's climate system of the small-amplitude variations in solar radiation that occur during the approximately 11-yr solar cycle [the decadal solar oscillation (DSO)] may produce significant responses in the troposphere (e.g., Haigh 1996Haigh , 2001Haigh , 2003Lean and Rind 2001;Rind 2002;Lean et al 2005;van Loon and Labitzke 1998;van Loon andShea 1999, 2000;Gleisner and Thejll 2003;van Loon et al 2004;Crooks and Gray 2005;Wang et al 2005;Bhattacharyya and Narasimha 2005;Lim et al 2006) and ocean (White et al 1997(White et al , 1998Bond et al 2001;Weng 2005). Specifically for the Indo-Pacific region, van Loon et al (2004van Loon et al ( , 2007 have demonstrated that the state of the climate system during peaks in the DSO resembles cold events (also known as La Niña events) in the Southern Oscillation.…”

The characteristics of the band‐pass filtered time series of the zonal averages of monthly mean values based on ERA‐40 reanalysis

“…We used essentially the same filter devised by Lim et al (2006) and employed also by Suh and Lim (2006) but with different cut-off frequencies. The digital filter was carved based on the wavelet analysis by Torrence and Compo (1998).…”

Solar Arctic-Mediated Climate Variation on Multidecadal to Centennial Timescales: Empirical Evidence, Mechanistic Explanation, and Testable Consequences

“…Lim et al (2006) found that solar irradiance modulation of local and regional relative humidity, in combination with the related climatic distribution of clouds and water vapor over the tropical Atlantic, is sufficient to explain the observed tropical Atlantic decadal oscillation.…”

“…The present study indirectly assumes the optimal climatic response filter of the Earth ocean-atmosphere-ice system to peak around such multidecadal to centennial scales, which can be taken to be roughly 50 to 500 years (i.e., much less than 1000 years). The challenge of this research, then, must lie in the identification of relevant and/or dominant centers of climatic action (COAs; Table 1 lists acronyms used in this paper) and interactions among those COAs (Christoforou and Hameed, 1997;Rodionov et al, 2005;Huth et al, 2006;Lim et al, 2006). Huth et al (2006) found a general tendency for atmospheric circulation modes 1 to be more zonal, with COAs covering wider areas and ARCTIC-MEDIATED CLIMATE VARIATION 145 teleconnection among different regions spanning longer distances when solar activity is strong.…”