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    Miscellaneous Research Papers (e.g. blocking, past severe winters and heatwaves)

    Blessed Weather

    Here are the current Papers & Articles under Miscellaneous. Click on the title of a paper you are interested in to go straight to the full paper.

    Exploring recent trends in Northern Hemisphere blocking
    2014 paper. Abstract:
    Observed blocking trends are diagnosed to test the hypothesis that recent Arctic warming and sea ice loss has increased the likelihood of blocking over the Northern Hemisphere. To ensure robust results, we diagnose blocking using three unique blocking identification methods from the literature, each applied to four different reanalyses. No clear hemispheric increase in blocking is found for any blocking index, and while seasonal increases and decreases are found for specific isolated regions and time periods, there is no instance where all three methods agree on a robust trend. Blocking is shown to exhibit large interannual and decadal variability, highlighting the difficulty in separating any potentially forced response from natural variability.

    Extreme weather events in early summer 2018 connected by a recurrent hemispheric wave-7 pattern.
    2019 paper. Abstract:
    The summer of 2018 witnessed a number of extreme weather events such as heatwaves in North America, Western Europe and the Caspian Sea region, and rainfall extremes in South-East Europe and Japan that occurred near-simultaneously. Here we show that some of these extremes were connected by an amplified hemisphere-wide wave number 7 circulation pattern. We show that this pattern constitutes an important teleconnection in Northern Hemisphere summer associated with prolonged and above-normal temperatures in North America, Western Europe and the Caspian Sea region. This pattern was also observed during the European heatwaves of 2003, 2006 and 2015 among others. We show that the occurrence of this wave 7 pattern has increased over recent decades.

    Ocean and atmosphere influence on the 2015 European heatwave
    2019 paper. Abstract:
    During the summer of 2015, central Europe experienced a major heatwave that was preceded by anomalously cold sea surface temperatures (SSTs) in the northern North Atlantic. Recent observation-based studies found a correlation between North Atlantic SST in spring and European summer temperatures, suggesting potential for predictability. Here we show, by using a high-resolution climate model, that ocean temperature anomalies, in combination with matching atmospheric and sea-ice initial conditions were key to the development of the 2015 European heatwave. In a series of 30-member ensemble simulations we test different combinations of ocean temperature and salinity initial states versus non-initialised climatology, mediated in both ensembles by different atmospheric/sea-ice initial conditions, using a non-standard initialisation method without data-assimilation. With the best combination of the initial ocean, and matching atmosphere/sea-ice initial conditions, the ensemble mean temperature response over central Europe in this set-up equals 60% of the observed anomaly, with 6 out of 30 ensemble-members showing similar, or even larger surface air temperature anomalies than observed.

    Origin of variability in Northern Hemisphere winter blocking on interannual to decadal timescales
    2015 paper. Abstract:
    Variability of mid-latitude blocking in the boreal winter Northern Hemisphere is investigated for the period 1960/1961 to 2001/2002 by means of relaxation experiments with the model of the European Centre for Medium‐Range Weather Forecasts. It is shown that there is pronounced interannual and decadal variability in blocking, especially over the Eurasian continent, consistent with previous studies. The relaxation experiments show that realistic variability in the tropics can account for a significant part of observed interannual blocking variability but also that about half of the observed variability can only be explained by extratropical tropospheric variability. On the quasi‐decadal timescale, extratropical sea surface temperature and sea ice, in addition to tropical variability, play a more important role. The stratosphere, which has been shown to influence interannual variability of the North Atlantic Oscillation in previous studies, has no significant influence on blocking according to our analysis.

    The climate in the UK from November 1994 to October 1995
    No abstract, but this paper looks at the exceptional warmth of this 12 month period.

    The meteorology of the exceptional winter of 2015/2016 across the UK and Ireland
    2016 paper. Abstract:
    The meteorological winter of 2015/2016 will be remembered as another exceptional winter across the UK and Ireland, with numerous climate records broken and high impact weather events causing considerable disruption from flooding and high winds. A succession of winter storms tracked across the region, bringing persistent and in places record‐breaking rainfall, including the highest 24 and 48 h rainfall accumulations on record, from storm Desmond on 4–6 December. Persistent rain, particularly through the first half of the winter, resulted in new records for both monthly and seasonal rainfall accumulations widely across Ireland, Scotland, Wales and northern England. Temperatures were also exceptionally high through much of December and in late January. In this paper we document the main meteorological and climate features that defined this exceptional winter season, and consider its wider historical context.

    The UK winter of 2009/2010 compared with severe winters of the last 100 years
    2010 paper. Abstract:
    When severe British winters of the last 100 years are considered, those of 1963 and 1947 are usually the first that come to mind. More recent candidates include 1979 and 1982. Should winter 2010 now also be added to this list? To assist with a ranking in terms of temperature (maximum, minimum and mean), we can analyse monthly series from 1910 and daily series from 1960, based upon 5km grids. These series were assembled using the methods of Perry and Hollis (2005) and have been used to create (i) areal values for the UK, England, Wales, Scotland, Northern Ireland and regions and (ii) colour‐shaded maps. The monthly Central England Temperature series from 1659 provides a longer‐term perspective (Manley, 1974). For snowfall, there are monthly 5km grids of days with snow lying from 1961 (based upon 0900 utc station observations), as well as station records of snow depth at 0900 utc, mostly digitised from 1959.

    The 1962/1963 winter as observed at Belstead Hall (Suffolk) and through investigation of the synoptic charts
    2013 paper. Abstract:
    When I was a schoolboy in Ipswich in the early 1960s, weather readings from the nearby Belstead Hall were reported in the local newspaper, the East Anglian Daily Times. Recently I was asked about preserving the records, and the whole of the archive material from the owner has now been passed to the Chilterns Observatory Trust, a charity set up by Philip Eden (2010). I have copied the data covering the severe winter of 1962/1963, and this article describes the highlights of it from those readings together with some of my personal recollections of that remarkable season.

    Tropical origin of the severe European winter of 1962/1963
    2014 paper. Abstract:
    A set of relaxation experiments using the European Centre for Medium‐Range Weather Forecasts (ECMWF) atmospheric model is used to analyze the severe European winter of 1962/1963. We argue that the severe winter weather was associated with a wave train that originated in the tropical Pacific sector (where weak La Niña conditions were present) and was redirected towards Europe, a process we suggest was influenced by the combined effect of the strong easterly phase of the Quasi‐Biennial Oscillation (QBO) and unusually strong easterly winds in the upper equatorial troposphere that winter. A weak tendency towards negative North Atlantic Oscillation (NAO) conditions in December, associated with extra-tropical sea‐surface temperature and sea‐ice anomalies, might have acted as a favourable preconditioning. The redirection of the wave train towards Europe culminated in the stratospheric sudden warming at the end of January 1963. We argue that in February the sudden warming event helped maintain the negative NAO regime, allowing the severe weather to persist for a further month. A possible influence from the Madden–Julian Oscillation, as well as a role for internal atmospheric variability, is noted.

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