Global atmospheric pressure variability and storminess reconstruction
Global atmospheric pressure variability and storminess reconstruction from meteorological observations and climate models, using our novel pressure variability index, dp(abs) (Jónsson and Hanna, Meteorologische Zeitschrift, 2007); exploration of the pressure-variability spectrum in time and space and links with climatic change. This aspect of the research includes collaborations with the Hadley Centre, Icelandic Meteorological Office and Danish Meteorological Institute, among others. New animated movie of European and north Atlantic interannual winter (January) barometric pressure variability/storminess constructed based on technique described in Jónsson & Hanna (2007) and on Hadley Centre EMSLP (Ansell et al 2006) data (see downloads). A new improved history and insights into North Atlantic, European and global surface atmospheric pressure variability, storminess and links with climatic change since 1850 Until recently, the North Atlantic Oscillation Index (NAOI) has been the only means to infer the atmospheric circulation over the European/North Atlantic region prior to the period of plentiful observations. However, as with all statistical indices, it is a 1D representation of what is in reality a complex 4D dynamical atmospheric process. Thus the NAOI is sensitive to (1) early barometric index errors and (2) migration of the bipolar centres of action under different climatic regimes; yet it is often used uncritically by climatic (and many other) researchers (Jόnsson & Hanna 2007). Cyclone detection and tracking algorithms are useful for deriving the frequency and intensity of individual storm systems but don't provide homogeneous information on atmospheric pressure fluctuations across various spatial and temporal scales from local through to global and from sub-hourly through to monthly. Since the latter are a more spatially continuous measure of atmospheric dynamics, they are likely to provide a more complete and detailed complementary record of changes in storminess as well as general variations in surface pressure systems (high as well as low), which are also often related to changes in mid-upper air circulation/jet streams. Our new pressure-variability index, dp(abs) (nominally 24-hourly MSLP variation), which we are now applying across the North Atlantic and European regions for the past century and a half, is intended to supplement the limited, inaccurate and sometimes misleading information on North Atlantic storminess available from the NAOI. This will be particularly valuable for 'filling in' the early (Nineteenth Century) part of the period and for evaluating recent/ongoing climatic change. The breakdown of long-term relationships between the NAOI and other climatic parameters has been of concern. The relation between the temperature in Northern Europe and the NAO is typical case: the two are highly correlated in recent decades but the relation is much more diffuse during some earlier periods. The new dp(abs) index might throw some light on the issue. A particular strength of the dp(abs) spectrum is its ability to reveal climate as being not just made up of weather but periods of variable length (typically several days to weeks) with similar weather (eg blocking vs. unsettled). A preliminary example of dp(abs) for London Heathrow is shown below:
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The London Heathrow 1919-2005 annual dp(abs) data appear to show (time-dependent) 7- and 17-/18-year periods in the wavelet spectrum, which may merit further investigation.
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The results of our proposed research will be useful not only for improving the historical record of global storminess but also for feeding into and/or helping validate models of changing mid- to high-latitude storminess under climate-change (eg global warming) scenarios. The proposed work has practical benefits, eg for the insurance industry, as well as helping to improve scientific knowledge of climatic change.
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