Start Submission Become a Reviewer

Reading: Convection forced by a descending dry layer and low-level moist convergence

Download

A- A+
Alt. Display

Original Research Papers

Convection forced by a descending dry layer and low-level moist convergence

Authors:

Andrew Russell ,

Centre for Atmospheric Science, University of Manchester, GB
X close

Geraint Vaughan,

Centre for Atmospheric Science, University of Manchester, GB
X close

Emily G. Norton,

Centre for Atmospheric Science, University of Manchester, GB
X close

Hugo M. A. Ricketts,

Centre for Atmospheric Science, University of Manchester, GB
X close

Cyril J. Morcrette,

Met Office, Exeter, GB
X close

Tim J. Hewison,

Met Office, Exeter, GB
X close

Keith. A. Browning,

School of Earth and Environment, University of Leeds, GB
X close

Alan M. Blyth

School of Earth and Environment, University of Leeds, GB
X close

Abstract

A narrow line of convective showers was observed over southern England on 18 July 2005 during the Convective Storm Initiation Project (CSIP). The showers formed behind a cold front (CF), beneath two apparently descending dry layers (i.e. sloping so that they descended relative to the instruments observing them). The lowermost dry layer was associated with a tropopause fold from a depression, which formed 2 d earlier from a breaking Rossby wave, located northwest of the UK. The uppermost dry layer had fragmented from the original streamer due to rotation around the depression (This rotation was also responsible for the observations of apparent descent—ascent would otherwise be seen behind a CF). The lowermost dry layer descended over the UK and overran higher θw air beneath it, resulting in potential instability. Combined with a surface convergence line (which triggered the convection but had less impact on the convective available potential energy than the potential instability), convection was forced up to 5.5 km where the uppermost dry layer capped it. The period when convection was possible was very short, thus explaining the narrowness of the shower band. Convective Storm Initiation Project observations and model data are presented to illustrate the unique processes in this case.

How to Cite: Russell, A., Vaughan, G., Norton, E.G., Ricketts, H.M.A., Morcrette, C.J., Hewison, T.J., Browning, K.A. and Blyth, A.M., 2009. Convection forced by a descending dry layer and low-level moist convergence. Tellus A: Dynamic Meteorology and Oceanography, 61(2), pp.250–263. DOI: http://doi.org/10.1111/j.1600-0870.2008.00382.x
  Published on 01 Jan 2009
 Accepted on 12 Nov 2008            Submitted on 25 Jun 2008

References

  1. Bader , M. J. , Forbes , G. S. , Grant , J. R. , Lilley , R. B. E. and Waters , A. J. 1995 . Images in Weather Forecasting: A Practical Guide for In-terpreting Satellite and Radar Imagery . Cambridge University Press , Cambridge , 499 pp .  

  2. Bennett , L. J. , Browning , K. A. , Blyth , A. M. , Parker , D. J. and Clark , P. A. 2006 . A review of the initiation of precipitating convection in the United Kingdon . Quart. J. R. Meteorol. Soc . 132 , 1001 – 1020 .  

  3. Bjerknes , J. and Solberg , H. 1922 . Life cycle of cyclones and the polar front theory of atmospheric circulation . Geophys. PubL 3 , 1 – 18 .  

  4. Browning , K. A. 1997 . The dry intrusion perspective of extra-tropical cyclone development . Meteorol. Appl . 4 , 317 – 324 .  

  5. Browning , K. A. and Monk , G. A. 1982 . A simple model for the synoptic analysis of cold fronts . Quart. J. R. Meteorol. Soc . 108 , 435 – 452 .  

  6. Browning , K. A. and Roberts , N. M. 1994 . Use of satellite imagery to diagnose events leading to frontal thunderstorms: part I of a case study . Meteorol. Appl . 1 , 303 – 310 .  

  7. Browning , K. A. and Roberts , N. M. 1995 . Use of satellite imagery to diagnose events leading to frontal thunderstorms: part H of a case study . Meteorol. Appl . 2 , 3 – 9 .  

  8. Browning , K. A. , Blyth , A. M. , Clark , P. A. , Corsmeier , U. , Morcrette , C. J. and co-authors. 2007 . The Convective Storm Initiation Project . Bull. Am. Meteorol. Soc . 88 , 1939– 1955 .  

  9. Clark , P. A. and Lean , H. 2006 . An overview of high resolution UM performance for CSIP cases. JCMM Internal Report, No. 155 , 42pp.  

  10. Cullen , M. J. P. 1993 . The unified forecast/climate model . Meteorol. Mag . 122 , 81 – 94 .  

  11. Danielsen , E. E 1964 . Project Springfield Report. Defense Atomic Sup-port Agency, 20301, DASA 1517(NTIS#AD-607980), Washington DC. , 99 pp .  

  12. Danielsen , E. F. 1968 . Stratospheric-troposheric exchange based on ra-dioactivity, ozone and potential voracity. J. Atmos. Sc i . 25 , 502 – 518 .  

  13. Emanuel , K. A. 1994 . Atmospheric Convection . Oxford University Press , Oxford , 580 pp .  

  14. Gage , K. S. and Green , J. A. 1981 . Evidence for specular reflection from monostatic VHF radar observations of the stratosphere . Radio Sc i . 13 , 991 – 1001 .  

  15. Goddard , J. W. F. , Eastment , J. D. and Thurai , M. 1994 . The Chilbolton Advanced Meteorological Radar: a tool for multidisciplinary atmo-spheric research . Electron. Commun. Eng. J . 6 , 77 – 86 .  

  16. Golding , B. 1998 . Nimrod: a system for generating automated very short range forecasts . Meteorol. Appl . 5 , 1 – 16 .  

  17. Golding , B. , Clark , P. A. and May , B. 2005 . The Boscastle flood: meteo-rological analysis of the conditions leading to flooding on 16 August 2004 . Weather 60 , 230 – 235 .  

  18. Griffiths , M. , Thorpe , A. J. and Browning , K. A. 2000 . Convective desta-bilization by a tropopause fold diagnosed using potential-vorticity inversion . Quart. J. R. Meteorol. Soc . 126 , 125 – 144 .  

  19. Heath , D. F. , Krueger , A. J. , Roeder , H. A. and Henderson , B. D. 1975 . The solar back-scatter ultraviolet and total ozone mapping spectrom-eter (SBUV/T’OMS) for Nimbus G. Opt. Eng. 14 , 323 - 331.  

  20. Hill , E F. and Browning , K. A. 1987 . Case study of a persistent mesoscale cold pool . Meteorol. Mag . 116 , 297 – 309 .  

  21. Hoskins , B. J. , McIntyre , E. M. and Robertson , A. W. 1985 . On the use and significance of isentropic potential vorticity maps . Quart. J. R. Meteorol. Soc . 111 , 877 – 946 .  

  22. Hunt , J. C. R. , On , A. , Rottman , J. W. and Capon , R. 2004 . Coriolis effects in mesoscale flows with sharp changes in surface conditions . Quart. J. R. Meteorol. Soc . 130 , 2703 – 2731 .  

  23. Marsham , J. H. and Parker , D. J. 2006 . Secondary iniation of multiple bands of cumulonimbus over southern Britain, part H: dynamics of secondary initiation . Quart. J. R. Meteorol. Soc . 132 , 1053 – 1072 .  

  24. Marsham , J. H. , Morcrette , C. J. , Browning , K. A. , Blyth , A. M. , Parker , D. J. and co-authors. 2007 a. Variable cirrus shading during CSIP IOP 5. I: effects on the initiation of convection . Quart. J. R. Meteorol. Soc . 133 , 1643– 1660 .  

  25. Marsham , J. H. , Blyth , A. M. , Parker , D. J. , Beswick , K. , Browning , K. A. and co-authors. 2007 b. Variable cirrus shading during CSIP IOP 5. II: effects on the convective boundary layer . Quart. J. R. MeteoroL Soc . 133 , 1661– 1675 .  

  26. Morcrette , C. J. , Browning , K. A. , Blyth , A. M. , Bozier , K. E. , Clark , P. A. and co-authors. 2006. Secondary iniation of multiple bands of cumulonimbus over southern Britain, part I: an observational case study . Quart. J. R. MeteoroL Soc . 132 , 1021 - 1051 .  

  27. Morcrette , C. J. , Lean , H. , Browning , K. A. , Roberts , N. , Clark , P. A. and co-authors . 2007. Combination of mesoscale and synop-tic mechanisms for triggering of an isolated thunderstorm: a case study of CSIP IOP 1. Mon. Wea. Rev . 135 , 3728 - 3749 .  

  28. Muschinslci , A. and Wode , C. 1998 . First in situ evidence for coex-isting submeter temperature and humidity sheets in the lower free troposphere . J. Atmos. Sci . 55 , 2893 – 2906 .  

  29. Norton , E. G. , Vaughan , G. , Methven , J. , Coe , H. , Brooks , B. and co-authors . 2006. Boundary layer structure and decoupling from synoptic scale flow during NAMBLEX. Atmos. Chem. Phys . 6 , 433 - 445 .  

  30. Roberts , N. M. 2000 . The relationship between water vapour imagery and thunderstorms . JCMM Internal Report, No . 110 , 40 pp .  

  31. Russell , A. , Vaughan , G. , Norton , E. G. , Morcrette , C. J., Brown-ing , K. A. and co-authors. 2008 . Convective inhibition beneath an upper-level PV anomaly. Quart. J. R. MeteoroL Soc . 134 , 371 - 383 .  

  32. Schmetz , J. , Pili , P. , Tjemkes , S. , Just , D. , Kerkmann , J. and co-authors. 2002. An introduction to Meteosat Second Generation (MSG) . Bull. Am. Meteorol. Soc . 83 , 977 - 992 .  

  33. Simpson , J. E. 1997 . Gravity Currents in the Environment and the Lab-oratory 2nd Edition . Cambridge University Press , Cambridge , 244 pp .  

  34. Thorncroft , C. D. , Hoskins , B. J. and McIntyre , E. M. 1993 . Two paradigms of baroclinic-wave life cycle behaviour. Quart. J. R. Mete-oroL Soc . 119 , 17 - 55 .  

  35. Vaughan , G. 2002 . The UK MST radar . Weather 57 , 67 – 73 .  

  36. Vaughan , G. , Price , J. D. and Howells , A. 1994 . Transport into the troposphere in a tropopause fold . Quart. J. R. MeteoroL Soc . 120 , 1085 – 1103 .  

  37. Ware , R. , Solheim , F. , Carpenter , R. , Gueldner , J. , Liljegren , J. and co-authors . 2003. A multi-channel radiometric profiler of temperature, humidity and cloud liquid. Radio Sci . 38 , 8079 - 8092 .  

comments powered by Disqus