Variability of the Northern Hemisphere polar stratospheric cloud potential: the role of North Pacific disturbances

Abstract

ABSTRACT:The potential of the Arctic stratosphere to sustain the formation of Polar Stratospheric Clouds (PSCs) is a key factor in determining the amount of ozone destroyed each winter, and is often measured as a 'PSC volume'. The latter quantity has been shown to closely follow a near-linear compact relationship with winter-averaged column ozone loss, and displays a high variability from monthly to decadal time-scales. We examine the connection between meteorological conditions in the troposphere and the variability of lower polar stratospheric temperatures over the last four decades, and specifically, conditions leading to a high PSC volume. In addition to the well-established connection between the North Atlantic Oscillation (NAO) and the polar vortex, we demonstrate the large influence of precursory disturbances over the North Pacific and the Far East, the region of maximum climatological upward wave activity flux. Namely, very high monthly PSC volume (in the top 12%) predominantly follows the development of positive tropospheric height anomalies over the Far East, which lead to a weakening of the background planetary wave trough, and lessened upward wave activity flux into the stratosphere. Precursory anomalies over the Far East are reminiscent of East Asian monsoon amplification episodes.

The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate

“…MSWs resulting in a splitting of the vortex are preceded by Pacific BHs or simultaneous BHs over the Atlantic and Pacific Oceans Castanheira and Barriopedro (2010) confirmed the results of Martius et al However, they also linked Pacific BHs to a destructive interference of climatological wavenumber-1 PW activity that sometimes is followed by an intensification of the polar vortex. This was also stated by Orsolini et al (2009) and Nishii et al (2010), but only for western Pacific BHs. This geographical dependence of the influence of BHs on the vertical PW propagation might explain the lack of statistical relationship between BHs and MSWs in Taguchi (2008).…”

“…While some recent studies have already analyzed this response for the recent past by using reanalysis data and model simulations (Martius et al 2009;Orsolini et al 2009;Castanheira and Barriopedro 2010;Nishii et al 2010;Woollings et al 2010;N11;Bancalà et al 2012;Vial et al 2013), none has explored this relationship in the future yet, as far as we know.…”

The Arctic vortex in March 2011: a dynamical perspective

“…Orsolini et al (2009) found that the largest observed Arctic PSC volumes were on average preceded by a weakening of the climatological, tropospheric low in the subpolar Far East and North Pacific regions. This type of "blocking" event in the North Pacific, also known as the positive phase of the Western Pacific teleconnection pattern (WP; Wallace and Gutzler, 1981), effectively weakens the upward propagation of upper tropospheric planetary waves (see e.g., Woollings et al, 2010).…”

“…Equally, winters when the subarctic SST index was most negative (e.g., 1987-1988) include months with strongly positive values of the PNA and WP indices. Previous work has linked weakening of the PNA and WP teleconnection patterns with stratospheric variability: Orsolini et al (2009) andGarfinkel et al (2010) found that variability in the Aleutian low modulates the strength of the Arctic vortex in mid-and late winter. Nishii et al (2010) found that extreme positive WP events in early winter can lead to persistent stratospheric cold periods and high PSC volumes in later months.…”

Accuracy and precision of polar lower stratospheric temperatures from reanalyses evaluated from A-Train CALIOP and MLS, COSMIC GPS RO, and the equilibrium thermodynamics of supercooled ternary solutions and ice clouds

“…Polar processes, such as the potential for ozone loss via heterogeneous reactions (Solomon, 1999;Solomon et al, 2015), depend critically on temperature. The potential ozone loss is related to the volume of stratospheric air that is below certain critical temperature thresholds associated with formation of PSCs (Rex et al, 2004;Orsolini et al, 2009;Harris et al, 2010). Mean winter temperatures in the Arctic stratosphere are significantly higher than those in the Antarctic (e.g., Waugh and Polvani, 2010), such that the propensity for the formation of persistent Arctic PSCs is much lower, and the development of widespread synoptic ice PSCs is quite rare .…”