Abstract
Abstract. We identify solar cycle signals in 155 years of global sea level pressure (SLP) and sea surface temperature (SST) data using a multiple linear regression approach. In SLP we find in the North Pacific a statistically significant weakening of the Aleutian Low and a northward shift of the Hawaiian High in response to higher solar activity, confirming the results of previous authors using different techniques. We also find a weak but broad reduction in pressure across the equatorial Pacific. In SST we identify a weak El Niño-like pattern in the tropics for the 155 year period, unlike the strong La Niña-like signal found recently by some other authors. We show that the latter have been influenced by the technique of compositing data from peak years of the sunspot cycle because these years have often coincided with the negative phase of the ENSO cycle. Furthermore, the date of peak annual sunspot number (SSN) generally falls a year or more in advance of the broader maximum of the 11-year solar cycle so that analyses which incorporate data from all years represent more coherently the difference between periods of high and low solar activity on these timescales. We also find that studies of the solar signal in SST over the second half of the 20th century may alias as ENSO signal if this is not properly taken into account.
Highlights
Signals of the 11-year solar cycle in various meteorological fields of the lower atmosphere, and in sea surface temperatures, have been presented by a number of authors
Reproduce the pattern found by vL07, using the HadSLP1 dataset, which placed a negative anomaly around 10–30◦ N in the mid-Pacific
We identify solar cycle signals in the North Pacific in 155 years of sea level pressure and sea surface temperature data
Summary
Signals of the 11-year solar cycle in various meteorological fields of the lower atmosphere, and in sea surface temperatures, have been presented by a number of authors. A large response is found in the Pacific in boreal winter: a positive anomaly in the Bay of Alaska, consistent with Christoforou and Hameed results, and a reduction in SLP near the date line around 20–40◦ N with a positive anomaly south of the equator (van Loon et al, 2007) (subsequently vL07) This has been interpreted as a strengthening of the SE trade winds crossing the equator, driving increased ocean upwelling and cooler equatorial temperatures (van Loon and Meehl, 2008). This is consistent with the vL07 analysis of sea surface temperatures (SSTs) which shows a strong La Nina (Cold Event, CE)-like signal when the Sun is more active. There is no clear picture of the SST response at solar maximum
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