DIURNAL CYCLE IN CONVERGENCE PATTERNS IN THE BOUNDARY LAYER EAST OF THE ANDES AND CONVECTION

NICOLINI, MATILDE; GARCÍA SKABAR, YANINA

Landshut, Alemania

Conferencia; 5th European Conference on Severe Storms; 2009

European Severe Storms Laboratory

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-TRAD; mso-fareast-language:ES-TRAD;} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The South American Low level Jet Experiment (SALLJEX) provided a data set unique to progress in the characterization of the low-level circulation both over the region where is typically located and southward ahead of the maximum wind where convergente dominates and generation of cvonvection is favored. Presenrt work builds upon high-resolution enriched analyses produced assimilating the data collected during this field campaign (November 15, 2002 to February 15, 2003) using BRAMS. With the purpose of progressing in the study of the mechanisms that control the diurnal cycle of precipitation and convection in subtropical latitudes east of the Andes during summer, this work focuses in exploring the capability of the enriched analysis with SALLJEX data to reproduce the diurnal cycle in mesoscale circulations in the boundary layed over northern and central Argentina not resolved by the low density observational network avalilable in this region. Diurnal cycle of convergence/divergence and rising/subsiding motions at the top of the boundary layer  related to a northwestern mountains-central plain flow regime is described in different synoptic situationbs. During weakly forced environments a regime characterized by nocturnal drainage flow and convergence and daytime upslope flow and divergence over the plains dominates. Mesoscale circulations are altered once deep convective circulations driven by convective heating dominates in the presence of convergence downstream the nocturnal maximum in the low-level jet above the shallow nocturnal boundary layer. The relationship between the nocturnal phases in the diurnal cycle in the convergence patterns and convection is also addressed in weakly and strongly forced environments.