7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 1 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

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler UTC: deep convection southeast of Freudenstadt with rain rate of roughly mm h -1 Question: Why did deep convection develop and why only over the Black Forest area? 1500 UTC 1115 UTC: first cumulus clouds over Black Forest 1230 UTC: cumulus clouds over Vosges; two weak north-south oriented cloud bands east of Black Forest crest 1230 UTC 1430 UTC 1400 UTC: both cloud bands intensified 1430 UTC: isolated deep convective cells with rain rates of roughly 5-8 mm h -1 IOP 8b (15 July 2007) 1. Evolution of deep convection

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 3 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 2. Synoptic conditions 1200 UTC 1800 UTC hPa h UTC

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 4 Achern, 1100 UTC 2. Convective conditions Heselbach Achern Burnhaupt FZK CCL (m asl) LFC (m asl) CIN (J kg -1 ) CAPE (J kg -1 )UTC 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 Heselbach, 1100 UTC

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler to 0800 UTC: Onset of up-slope winds resulting in convergence over the mountain crest 3.1 PBL processes relevant for triggering of convection western slopeeastern slope

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

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

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 8 Achern change from SE to NW wind finished at 1030 UTC 3.2 Evolution of a convergence zone between the surface low and high

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

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler Evolution of a convergence zone between the surface low and high Barongartenhütte change from SE to NW wind finished at 1330 UTC

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 11 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 3.2 Evolution of a convergence zone between the surface low and high

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

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler Evolution of a convergence zone between the surface low and high DO 128: 1217 – 1328 UTC, flight level: 1500 m asl near Barongartenhütte vertical 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)

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

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 15 Thanks for your attention!

7 th COPS Workshop Collège Doctoral Européen Strasbourg, France, October 2008 The impact of convergence zones on the initiation of deep convection Bianca Adler 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 UTC: SW wind in most parts