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The Troposphere-Ocean Response to 11-Year Solar Forcing and Feedbacks on the Lower Stratosphere
Abstract
The lower stratospheric response to 11-year solar forcing plays a
significant role in our understanding of how solar variability
influences climate. If the observed lower stratospheric response is
primarily a consequence of ``top-down'' forcing from the (mainly)
solar-UV induced response of the upper stratosphere, then it would
follow that top-down UV forcing could also be an important driver of
tropospheric climate change. If, on the other hand, the observed lower
stratospheric response is primarily a consequence of ``bottom-up''
dynamical feedbacks from a troposphere-ocean response that is driven
mainly by changes in total solar irradiance (TSI), then it would follow
that direct TSI forcing of near-surface climate is the main driver of
solar-induced climate change. Here, we investigate whether a
statistically significant solar cycle response of the troposphere-ocean
system exists that has characteristics consistent with producing a major
part of the observed solar cycle response in the tropical lower
stratosphere. To characterize the troposphere-ocean response, a multiple
linear regression statistical model is applied to Hadley Centre sea
level pressure (SLP) and sea surface temperature (SST) data, which are
available back to ~ 1870. In agreement with previous authors, the most
statistically significant response is obtained for SLP in the North
Pacific during northern winter, consisting of a strengthening and
eastward shift of the Aleutian low near solar minima relative to solar
maxima. An associated response of North Pacific wintertime SST is also
obtained but is less repeatable for separate time periods. In addition,
a marginally significant SLP increase over eastern Europe is obtained
near solar minima relative to solar maxima. The North Pacific response
can be described as ``La Niña-like'' near solar maxima, in
agreement with previous analyses using compositing methods (van Loon et
al., JGR, 2007) and with some climate model studies (e.g., Meehl et al.,
Science, 2009). Both the negative North Pacific SLP response and the
positive eastern European SLP response under solar minimum conditions
correspond to known troposperic precursors of anomalous stratospheric
circulation changes, including weakening of the polar vortex and
acceleration of the mean meridional (Brewer-Dobson) circulation (e.g.,
Garfinkel et al., J. of Climate, 2010). The observed SLP response is
therefore most consistent with a bottom-up mechanism for driving the
tropical lower stratospheric response, involving acceleration of the
tropical upwelling rate near solar minima which would decrease ozone
mixing ratios and temperature relative to solar maximum conditions. A
simplified analytic model suggests that much of the observed tropical
lower stratospheric response, including the solar cycle variation of
total ozone, can be explained by this mechanism.
... In particular, Labitzke and Van Loon (1995) iden- tified a similar decadal oscillation signature to that of the solar cycle, and also proved correlations as high as 0.7 for selected temporal subsets of the 30-hPa geopotential height above North America and over the North Pacific Ocean (Fig. 3(a) and (b), E). Lateral variations of the correlations between solar cycles and the atmosphere have also been explored by some of the previous references, as well as in Hood and Soukharev (2012), who found notable connec- tions between sea level pressure and SSNs in the northern Pacific, as well as additional broad areal patterns of statis- tically significant similarities. ...
Trade winds localized within the western equatorial Pacific express lagged and statistically significant correlations to sunspot numbers as well as to streamflow in rivers of the Southern Rocky Mountains. Both correlation sets were integrated in a linear regression analysis to produce relatively accurate sub-decadal streamflow forecasts for an annual and a 5-year average. In comparison to the auto-correlation technique, the prototyped method yielded the highest correlations, the highest goodness-of-fit scores, and the lowest root mean squared errors, for both the 5-year average and the annual average assignments. Of all of the cases examined, the highest Kolmogorov-Smirnov test scores between observation and prediction were found for the single solar-based forecast 5 years in advance for the 60-month average streamflow of the Animas River in New Mexico.
... If it is possible to find a physical explanation for the lags of the TO response to the SA variations (positive lags), it is quite complicated to imagine the mechanisms conditioning the advance of the quasi-decadal variations of TO relative to those of SA. One of the reasons of the TO modulation by the SA variations is, possibly, the decadal variations of the Brewer-Dobson circulation (Hood and Soukharev, 2012;WMO, 2014). According to current conceptions, ozone generated in the equatorial region is transported to the high latitudes due to the Brewer-Dobson circulation for several years (Weber, 2011). ...
This paper presents the results of an analysis of the phase relationships between the variations of solar activity (SA) with periods ranging from 8 to 13 years and the quasi-decadal variations (QDVs) of zonally and globally average values of total ozone (TO), and some parameters of the lower stratosphere at 50 and 100 GPa based on the NCEP-NCAR and satellite data. Analysis of the temporal and spatial variability of meteorological parameters and TO has been performed by Fourier, correlation and composite analysis for the period from 1979 to 2015 in the 90° S– 90° N latitudinal belt. The TO spectra have basic oscillations with periods of 116–140 months at all latitudes. The oscillations with periods of 87–96 months are also observed at the high southern latitudes. Significant oscillations of temperature and geopotential height with periods ranging from 95 to 102 and from 127 to 148 months are observed in the 90° S– 55° N latitudinal belt. The oscillations of the meridional and zonal wind velocity have periods within intervals of 85–100 and 120–150 months; their significance varies with altitude. The maxima of the TO QDVs advance the SA maxima by 20 months at the middle and high north latitudes and lag behind by 21 months at the high latitudes of the Southern Hemisphere. The lag between the SA and TO variations reverses its sign at 35°–40° S. On average, the phase of the QDVs of temperature and geopotential height within the 90° S–55° N latitudinal belt lags behind the SA variations approximately by one year and half a year, respectively. The phase relationships between the meridional and zonal wind variations and the 11-year SA cycle vary considerably with time and latitude. The quasi-decadal variations of the globally average TO values coincide with the SA variations.
... However, Chiodo et al. (2014) used a model with a prescribed ocean (WACCM), and there are reasons to think that feedbacks from the tropical troposphere/ocean response could be important in increasing the amplitude of the lower stratospheric response (e.g. Hood and Soukharev, 2012). Note that recent experiments with the upgraded WACCM including an interactive ocean already reveal a lower stratospheric warming due to the 11-year solar cycle obtained with MLRA during volcanically quiet periods (Lon Hood, November 2016, private communication). ...
The solar rotational variability (27-day) signal in the Earth's middle atmosphere has been studied for several decades, as it was believed to help in the understanding of the Sun's influence on climate at longer timescales. However, all previous studies have found that this signal is very uncertain, likely due to the influence of the internal variability of the atmosphere. Here, we applied an ensemble modeling approach in order to decrease internal random variations in the modeled time series. Using a chemistry-climate model (CCM), SOCOLv3, we performed two 30-member 3-year long (2003–2005) ensemble runs: with and without a rotational component in input irradiance fluxes. We also performed similar simulations with a 1-D model, in order to demonstrate the system behavior in the absence of any dynamical feedbacks and internal perturbations. For the first time we show a clear connection between the solar rotation and the stratospheric tropical temperature time-series. We show tropical temperature and ozone signal phase lag patterns that are in agreement with those from a 1-D model. Pronounced correlation and signal phase lag patterns allow us to properly estimate ozone and temperature sensitivities to irradiance changes. While ozone sensitivity is found to be in agreement with recent sensitivities reported for the 11-year cycle, temperature sensitivity appears to be at the lowest boundary of previously reported values. Analysis of temperature reanalysis data, separate ensemble members, and modeling results without a rotational component reveals that the atmosphere can produce random internal variations with periods close to 27 days even without solar rotational forcing. These variations are likely related to tropospheric wave-forcing and complicate the extraction of the solar rotational signal from observational time-series of temperature and, to a lesser extent, of ozone. Possible ways of further improving solar rotational signal extraction are discussed.
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