Adler_7th_COPS_WS

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					The impact of convergence zones on the
     Initiation of Deep Convection




B. Adler*, N. Kalthoff, Ch. Barthlott, U. Corsmeier, S. Khodayar,
  Ch. Kottmeier, K. Träumner, S. Mobbs, S. Crewell, V. Smith


        * Institut für Meteorologie und Klimaforschung, IMK
                    Karlsruhe Institute of Technology, KIT


           7th COPS Workshop
                                                The impact of convergence zones on the initiation
       Collège Doctoral Européen
                                                               of deep convection                   1
Strasbourg, France, 27 - 29 October 2008                           Bianca Adler
1. Evolution of deep convection
      IOP 8b (15 July 2007)

             1500 UTC
            1230 UTC
            1430 UTC




  •
  •    1400 UTC: both convection intensified
       1115 UTC: deep cloud bandssoutheast of Freudenstadt with rain rate of roughly
       1500 UTC: first cumulus clouds over Black Forest
        21-35 mm h-1
  •    1230      cumulus clouds over Vosges; with rain north-south oriented
       1430 UTC: isolated deep convective cells two weak rates of roughly 5-8 mm h-1
  •    cloud bands Why did Forest crest
       Question:east of Blackdeep convection develop and why only over
       the Black Forest area?

                    7th COPS Workshop
                                                        The impact of convergence zones on the initiation
                Collège Doctoral Européen
                                                                       of deep convection                   2
         Strasbourg, France, 27 - 29 October 2008                          Bianca Adler
2. Synoptic conditions

                                                                                                              hPa h-1




                                1200 UTC                                                    1200 UTC

•   COPS area was in the transition zone between an eastern Atlantic trough and an eastern
    European ridge
•   Surface low in the west (south-westerly wind) and surface high in the east (easterly wind),
    convergence in between
•   No significant upper level lifting in the COPS area



                   7th COPS Workshop
               Collège Doctoral Européen                                                1800 UTC
                                                          The impact of convergence zones on the initiation
                                                                         of deep convection                     3
        Strasbourg, France, 27 - 29 October 2008                             Bianca Adler
  2. Convective conditions
   Achern,
Heselbach, 1100 UTC

                                                                          CAPE             CIN       LFC         CCL
                                                                UTC       (J kg-1)       (J kg-1)   (m asl)     (m asl)

                                                      FZK        1100       408            147       3229           2797

                                                    Burnhaupt    1100       483            253       3676           2438

                                                     Achern      1059        90            327       3577           2579

                                                    Heselbach    1129       361             78       3260           3022

                                                    Achern (Rhine valley): low CAPE, high CIN
                                                    Heselbach (Black Forest): moderate CAPE,
                                                    lower CIN
                                                    • Conditions not too favourable for deep
                                                    convection
                                                    • If trigger mechanism present, convection
                                                    most likely in Black Forest area



                    7th COPS Workshop
                                                                The impact of convergence zones on the initiation
                Collège Doctoral Européen
                                                                               of deep convection                     4
         Strasbourg, France, 27 - 29 October 2008                                    Bianca Adler
    3.1 PBL processes relevant for triggering of convection
      western slope                                   eastern slope




•    0700 to 0800 UTC: Onset of up-slope winds resulting in convergence over the
     mountain crest

                      7th COPS Workshop
                                                         The impact of convergence zones on the initiation
                  Collège Doctoral Européen
                                                                        of deep convection                   5
           Strasbourg, France, 27 - 29 October 2008                         Bianca Adler
3.2 Evolution of a convergence zone between the surface
low and high




                 7th COPS Workshop
                                                 The impact of convergence zones on the initiation
             Collège Doctoral Européen
                                                                of deep convection                   6
      Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
  3.2 Evolution of a convergence zone between the surface
  low and high
Meistratzheim
• change from
SE to SW wind
finished at 1000
UTC in lowest 2
km




                      7th COPS Workshop
                                                      The impact of convergence zones on the initiation
                  Collège Doctoral Européen
                                                                     of deep convection                   7
           Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
  3.2 Evolution of a convergence zone between the surface
  low and high
Achern
• change from
SE to NW wind
finished at 1030
UTC




                      7th COPS Workshop
                                                      The impact of convergence zones on the initiation
                  Collège Doctoral Européen
                                                                     of deep convection                   8
           Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
3.2 Evolution of a convergence zone between the
surface low and high              Hornisgrinde:
                                                • 1100 UTC change from SE to W wind
                                                • convergence zone SUPERIMPOSES on
                                                the stationary slope-wind generated one
                                                • updrafts of 2 m s-1 extend up to 3100 m
                                                asl penetrate capping inversion and
                                                nearly reach LFC
                                                • 15 min after the convergence zone
                                                passed the Black Forest crest first
                                                clouds formed




                7th COPS Workshop
                                                 The impact of convergence zones on the initiation
            Collège Doctoral Européen
                                                                of deep convection                   9
     Strasbourg, France, 27 - 29 October 2008                       Bianca Adler
3.2 Evolution of a convergence zone between the
surface low and high
                                                                                  Barongartenhütte

                                                                                  • change from
                                                                                  SE to NW wind
                                                                                  finished at 1330
                                                                                  UTC




                7th COPS Workshop
                                                The impact of convergence zones on the initiation
            Collège Doctoral Européen
                                                               of deep convection                   10
     Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
3.2 Evolution of a convergence zone between the
surface low and high              Heselbach

                                                • change in wind direction from SE to SW
                                                in lowest 2 km finished at 1400 UTC

                                                • base of deep convection at 2.5 km agl (3
                                                km asl)

                                                • at the same time increase of humidity




                7th COPS Workshop
                                                  The impact of convergence zones on the initiation
            Collège Doctoral Européen
                                                                 of deep convection                   11
     Strasbourg, France, 27 - 29 October 2008                        Bianca Adler
3.2 Evolution of a convergence zone between the
surface low and high
                                                                                  Igelsberg
                                                                                  • change from
                                                                                  SE to SW wind
                                                                                  finished at 1400
                                                                                  UTC




                7th COPS Workshop
                                                The impact of convergence zones on the initiation
            Collège Doctoral Européen
                                                               of deep convection                   12
     Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
3.2 Evolution of a convergence zone between the
surface low and high
                                                    • near Barongartenhütte vertical
DO 128: 1217 – 1328 UTC, flight level: 1500 m asl   updrafts up to 3.5 m s-1 (DO 128)
                                                    • over Murg valley updrafts up to
                                                    5 m s-1 (BA 146; flight level: 1900
                                                    m asl)




                    7th COPS Workshop
                                                     The impact of convergence zones on the initiation
                Collège Doctoral Européen
                                                                    of deep convection                   13
         Strasbourg, France, 27 - 29 October 2008                       Bianca Adler
Summary

 •   15 July 2007 deep convection developed over the Black Forest area

 •   Conditions were not too favourable for convection, because
      – high CIN and moderate CAPE
      – no significant upper air lifting
      – If a trigger mechanism was present, the Black Forest area would be
        slightly favourable to the evolution of deep convection

 •   The reason for development of convection was an optimal superposition of
     different convergence zones over the Black Forest resulting in vertical updrafts
     of about 2 m s-1 which penetrated the lids and triggered convection

 •   East of the Black Forest crest the convergence zone intensified, strong
     updrafts of up to 5 m s-1 below convective cells were measured



                  7th COPS Workshop
                                                   The impact of convergence zones on the initiation
              Collège Doctoral Européen
                                                                  of deep convection                   14
       Strasbourg, France, 27 - 29 October 2008                       Bianca Adler
                    Thanks for your attention!




           7th COPS Workshop
                                           The impact of convergence zones on the initiation
       Collège Doctoral Européen
                                                          of deep convection                   15
Strasbourg, France, 27 - 29 October 2008                      Bianca Adler
• 0748-0900 UTC: Dornier 128 flight at level 1500 m asl SW wind in the whole COPS domain
• along Black Forest crest vertical velocity up to 0.5 m s-1
• 1217-1328 UTC: SW wind in most parts

                    7th COPS Workshop
                                                       The impact of convergence zones on the initiation
                Collège Doctoral Européen
                                                                      of deep convection                   16
         Strasbourg, France, 27 - 29 October 2008                         Bianca Adler

				
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posted:8/4/2011
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