Atmospheric Circulation Reconstructions  over the Earth
Applications Climate Science
Climate Science Applications (detailed) The   major   culmination   of   ACRE         activities   is   the   20CR   reanalysis   system   conceived   and   run   by   the Earth   Systems   Research   Laboratory   (CIRES,   University   of   Colorado)   with   the   support   of   the   Earth System   Research   Laboratory   (ESRL,   of   NOAA).      Using   relatively   sparse   input   of   surface   pressure data,   much   provided   and   facilitated   by   ACRE   and   its   partners,   the   system   recreates   a   rich   4D   global dynamical   reconstruction   of   historical   weather   events.   Climate   scientists   can   use   this   output   to   analyse in   detail   a   range   of   climate   phenomenon.   Below   is   a   representative   sample   of   this   research   work   made possible   by   ACRE   and   20CR.      A   greater   range   of   scientific   research   that   relied   on   20CR   is   available here  and here : Land surface temperatures Confirmation of global warming Even   though   20CR   does   not   assimilate   surface   temperature   observations,   Compo   et   al.   (2013) were   able   to   confirm   the   robustness   of   previous   conclusions   regarding   global   warming.   20CR only   uses   synoptic   barometric   pressure,   monthly   sea   surface   temperature,   and   monthly   sea- ice   concentration   to   reproduce   up   to   56   realisations   of   annual   variations   and   centennial   trends in   the   land   air   temperature   data   sets.   It’s   output   confirming   global   warming   without   using   land           surface   temperature   records,   is   free   of   any   possible   inconsistencies   in   such   data   that   have been proposed previously by climate change sceptics Hemispheric to regional surface temperature variations Yu   et   al.   (2014)    focused   on   decadal   modulations   of   Northern   Hemisphere   winter   land   surface air   temperatures   and   atmospheric   circulation,   while   Richard   et   al.   (2012)   examined   mid   to   high latitude   changes   in   Southern   Hemisphere   land   surface   air   temperatures.      More   regionally, Soon   et   al.   (2011)   focused   on   variations   in   land   surface   air   temperatures   in   China,   Vose   et   al. (2012)   examined   trends   in   US   land   surface   air   temperatures   using   observed   and   various reanalyses,   while   Turco   et   al.   (2012)   looked   at   Spanish   instrumental   and   downscaled   20CR output. Precipitation Regional Zhang   et   al.   (2012)   focusing   on   southern   Africa,   used   8   global   reanalyses   to   study   African monthly-mean   precipitation   and   compared   their   outputs   to   the   gridded   precipitation   dataset from   the   Climate   Research   Unit   (CRU)   at   the   University   of   East   Anglia.      They   found   that:   “the preferential   reanalysis   for   investigating   the   climate   variability   over   southern   Africa   is   20CRv2 that    furthermore    spans    the    longest    time    period,    hence    permitting    the    most    precise investigations of interannual to decadal variability”. Sub Regional A   pilot   project   was   initiated   by   the   Met   Office   PRECIS   group   using   their   regional   climate modelling   system   to   downscale   20CR   to   study   the   rainfall   associated   with   the   1894   River Thames/Southern   England   flooding   event   (Brugge,   1994).   The   study   aimed   to   simulate   the precipitation    drivers    of    the    1894    flooding    of    the    River    Thames.    It    demonstrated    that    the downscaled   member   37   of   the   56   ensemble   member   output   from   20CR   provides   the   best representation   of   the   precipitation   conditions   over   the   most   heavily   impacted   regions   of   the   UK.     As    noted    previously,    the    PRECIS    team    are    now    downscaling    20CR    to    provide    a    high          resolution   baseline   of   UK   droughts   from   1850-2014   under   the   MaRUIS   Project   (Managing   the        Risks, Impacts and Uncertainties of drought and water Scarcity) Storms 20CR   contributed   to   the   analysis   of   an   1888   blizzard   and   a   1925   tornado   in   the   US,   and   storms   in   the UK in both the 19th and 20th centuries. Wave Heights A   number   of   researchers   have   used   20CR   to   reanalyse   wave   heights   and   storm   surges.     They   came   to the   conclusion   that   the   data   in   the   model   is   incomplete,   pointing   to   the   need   for   more   Old   World   data recovery, digitisation and assimilation into 20CR model, activities championed by ACRE. Heat Waves and cold spells 20CR   contributed   to   the   analyses   of   likely   causes   of   a   recent   heatwave   in   Russia   and   causes   of   ice sheet   melting   in   Greenland.   Ouzeau   et   al.   (2011)   used   20CR   to   establish   the   uniqueness   of   the European   cold   winter   of   2009-2010.   A   weather   regime   analysis   showed   that   the   frequency   of   the negative   North Atlantic   Oscillation   was   unprecedented   since   the   winter   of   1939–1940,   which   was   then used   as   a   dynamical   analogue   of   the   winter   of   2009–2010   to   demonstrate   that   the   latter   might   have been   much   colder   without   the   background   global   warming   observed   during   the   twentieth   century. They further   used   20CR   products   to   highlight   the   relevance   of   the   stratosphere   for   understanding,   if   not predicting, such anomalous winter seasons. Floods and Droughts A   number   of   studies   have   used   20CR   to   analyse   historic   floods   and   droughts   in   Europe   and   North America   up   to   150   years   ago.      They   also   examined   the   synoptic,   interannual,   decadal   and   multi- decadal conditions underlying them. El Niño Southern Oscillation Studies   using   20CR   and   other   reanalyses   have   looked   to   improve   understanding   of   ENSO   dynamics. They   re-examined   ENSO   events   to   determine   their   connection   with   other   climate   anomalies   including ocean   winds,   sea   subsurface   temperatures,   SW   Pacific   rainfall   and   global   drought.      A   study   of   the 1877-1878    El    Niño,    and    the    conditions    leading    up    to    and    following    it,    using    20CR    is    in    under development. Global warming hiatus In   a   draft   of   work   led   by   Li   Qingxiang    (China   Met.   Admin.,   Beijing),   a   comparison   was   made   between surface   air   temperature   trends   from   20CR   and   observed   trends   over   China.   For   1961-2012,   20CR produced   year-round   warming,   as   observed.   For   the   global   warming   “hiatus”   period   1998-2012,   20CR reproduced   cooling   over   China   in   winter,   in   agreement   with   observations,   with   little   change   in   summer. As   20CR   does   not   use   air   temperature   data   or   aerosol   forcings,   it   was   concluded   that   the   winter cooling   must   have   come   from   the   atmospheric   circulation,   i.e.   an   increase   in   winds   from   the   north responding to the assimilated atmospheric pressure data. Other Historical events Tambora Eruption and the ‘Year without a Summer’ (1815-1817) Reaching very far back into climate history, this is a reanalysis of the period around the Tambora volcanic eruption using 20CRv2c, but with climatological SST and sea-ice, and no stratospheric aerosols.  Imperial Trans-Antarctic Expedition (1914–17) The Imperial Trans-Antarctic Expedition led by Sir Ernest Shackleton, failed to reach its exploration objectives, but it did allow groups of scientists to spend many months in the Antarctic, where they made careful observations of the weather. Though the expedition records have not been published or systematically analysed, they provide the data required for a reanalysis of the Antarctic weather 1914-1916.
“Climate scientists can use this output to analyse in detail a range of climate phenomenon.”
“..used 8 global reanalyses to study African monthly- mean precipitation”
“…the frequency of the negative North Atlantic Oscillation was unprecedented since the winter of 1939–1940”
“Reaching very far back into climate history…”
LINKS 20CR   Publications    -   an   extensive,   linked   list   of   publications   outlining   the   use,   mainly   in   climate   science,     of 20CR Reanalysis system products. 20CR in the News - news-style articles covering a wide array of uses of Reanalysis systems products