Simulations of winter blocking episodes using observed sea surface temperatures

Abstract

The formation of major northern hemisphere blockings during January 1979 is studied in numerical simulations of the global atomosphere with a sea surface temperature (s.s.t.) field updated with observations during the model integration. Both the standard 4 x 5 degrees latitude-longitude and high-resolution 2 x 2-5 degrees versions of the Goddard Laboratory for Atmospheres general circulation models (GCMs) are employed. The s.s.t. field is provided by a blend analysis of in situ and satellite-retrieved data.The simulations by the high-resolution GCM with a realistic s.s.t. field of the ocean surface are shown to be capable of producing two successive realistic major blockings in the Pacific and Atlantic through a onemonth period. The skill in predicting the blocking formation as obtained in the simulations is due to improved skill in forecasting of ultralong waves. Although the results are encouraging, only one initial state is involved in this series of simulations; therefore, the results should not be generalized yet at this stage of investigation.

The anomalous structures of atmospheric and oceanic variables associated with the frequency of North Pacific winter blocking

“…In terms of blocking, many studies have emphasized the role of internal atmospheric transient eddies [e.g., Kalnay‐Rivas and Merkine , 1981; Shutts 1983; Holopainen and Fortelius , 1987; Nakamura et al , 1997; Huang et al , 2002]. Whereas, some studies have proposed that ocean heat forcing is able to reinforce blocking [e.g., Kung et al , 1990; Huang et al , 2002; Tilly et al , 2008].…”

“…On the other hand, many experiments have been conducted to assess atmospheric changes in response to SST anomalies at midlatitudes [e.g., Lau and Nath, 1990;Peng and Whitaker, 1999;Rodwell et al, 1999;Huang et al, 2002;Liu and Wu, 2004;Ferreira and Frankignoul, 2005]. Regarding experiments carried out to examine the influence of SST on blocking formation, Kung et al [1990] conducted a simulation of blocking formation for January 1979, applying global observed SST anomalies as a boundary condition of the General Circulation Model (GCM). Tilly et al [2008] proposed that diabatic processes contribute to the two cases of Southern Hemisphere blocking intensification through the theoretical study using vorticity equations; however, the previous studies on heating as a contributor of blocking were not generalized.…”

Impact of land–sea thermal contrast on interdecadal variation in circulation and blocking

“…The decrease in Ural blocking contributed to the higher frequency of warm winters in China (Wang et al 2010). Several theories regarding the formation and maintenance of blocking events have been proposed, including nonlinear interactions between planetary waves or between large-scale flow and transient eddies (Egger 1978;Kung et al 1990). A number of studies recognized that blocking may be the result of the adjustment of planetary waves to deviations in the zonal-mean flow or the linear resonance of planetary waves with surface forcing (Kaas and Branstator 1993).…”

The Effect of Boreal Late Autumn Snow Cover over Western and Central China on the Northern Hemisphere Wintertime Blocking Frequency

“…However, the mechanisms of the formation and maintenance of blocking are controversial because a variety of factors are known to act on blocking, such as nonlinear effects of atmospheric motion, orographic effects, tropical forcing, and energy supply by baroclinic transient eddies (Shutts 1983;Mullen 1987;Nakamura and Wallace 1993). Kung et al (1990) insisted that global sea surface temperature anomalies are related to blocking frequency (BF) based on model experiments. Renwick and Wallace (1996) have shown that the phases of El Niño-Southern Oscillation are highly related with North Pacific BF on the interannual time scale, and Renwick (1998) has argued that southeast Pacific BF increases in El Niño years but decreases in La Niña years.…”