On the persistence and predictability properties of north atlantic climate variability
Journal of Climate 24:2 (2011) 466-472
Abstract:
The persistence and climate noise properties of North Atlantic climate variability are of importance for trend identification and assessing predictability on all time scales from several days to many decades. Here, the authors analyze these properties by applying empirical mode decomposition to a time series of the latitude of the North Atlantic eddy-driven jet stream. In previous studies, it has been argued that a slow decay of the autocorrelation function at large lags suggests potential extended-range predictability during the winter season. The authors show that the increased autocorrelation time scale does not necessarily lead to enhanced intraseasonal predictive skill. They estimate the fraction of interannual variability that likely arises due to climate noise as 43%-48% in winter and 70%-71% in summer. The analysis also indentifies a significant poleward trend of the jet stream that cannot be explained as arising from climate noise. These findings have important implications for the predictability of North Atlantic climate variability. © 2011 American Meteorological Society.The solar influence on the probability of relatively cold UK winters in the future
Environmental Research Letters 6:3 (2011)
Abstract:
Recent research has suggested that relatively cold UK winters are more common when solar activity is low (Lockwood et al 2010 Environ.Res.Lett. 5 024001). Solar activity during the current sunspot minimum has fallen to levels unknown since the start of the 20th century (Lockwood 2010 Proc. R. Soc. A 466 303-29) and records of past solar variations inferred from cosmogenic isotopes (Abreu et al 2008 Geophys.Res.Lett. 35 L20109) and geomagnetic activity data (Lockwood et al 2009 Astrophys. J. 700 937-44) suggest that the current grand solar maximum is coming to an end and hence that solar activity can be expected to continue to decline. Combining cosmogenic isotope data with the long record of temperatures measured in central England, we estimate how solar change could influence the probability in the future of further UK winters that are cold, relative to the hemispheric mean temperature, if all other factors remain constant. Global warming is taken into account only through the detrending using mean hemispheric temperatures. We show that some predictive skill may be obtained by including the solar effect. © 2011 IOP Publishing Ltd.Atmospheric blocking and mean biases in climate models
Journal of Climate 23:23 (2010) 6143-6152
Abstract:
Models often underestimate blocking in the Atlantic and Pacific basins and this can lead to errors in both weather and climate predictions. Horizontal resolution is often cited as the main culprit for blocking errors due to poorly resolved small-scale variability, the upscale effects of which help to maintain blocks. Although these processes are important for blocking, the authors show that much of the blocking error diagnosed using common methods of analysis and current climate models is directly attributable to the climatological bias of the model. This explains a large proportion of diagnosed blocking error in models used in the recent Intergovernmental Panel for Climate Change report. Furthermore, greatly improved statistics are obtained by diagnosing blocking using climate model data corrected to account for mean model biases. To the extent that mean biases may be corrected in low-resolution models, this suggests that such models may be able to generate greatly improved levels of atmospheric blocking. © 2010 American Meteorological Society.Winds of change?
Planet Earth (2010) 18-19
Abstract:
Tim Woollings discusses the reasons behind the natural events such as the cold European winter of 2009-10, heatwave in Russia, and devastating floods in Pakistan. The jet streams are literally jets of fast-moving air that are strongest about 10km up in the atmosphere - around the level where airliners fly. Jet streams vary in strength from week to week. One of the most common variations in the North Atlantic jet stream is for the whole jet to shift to the north or the south. While the North Atlantic jet stream generally points roughly due east, straight across the Atlantic, it often meanders north and south. When waves on the ocean surface become too large they overturn and break, resulting in very turbulent motion. When Rossby waves break, the resulting weather situation is known as blocking.Enhanced signature of solar variability in Eurasian winter climate
Geophysical Research Letters 37:20 (2010)