Numerical investigation of the multi-scale processes inducing convection initiation for the 12 June 2002 IHOP_2002 case study

This study, using numerical simulations, investigates a case of convection initiation observed during the International H2O Project (IHOP_2002) experiment that took place in the South Great Plains of the U.S. during May-June 2002. The aim of this study is to better understand the influence of the processes at different scales, from the synoptic scale down to the scale of horizontal convective rolls, on the location and timing of convection.

On June 12, the synoptic forcing is propitious to the development of deep convection, with the formation of a dryline and an outflow boundary that intersect near the north Oklahoma/Kansas border. Radar reflectivity measurements, however, show that the storms did not form directly along these mesoscale boundaries. Other physical processes in the boundary layer affect the initiation of convection. In particular, observations show the existence of gravity waves, a mesocyclone and horizontal convective rolls in the area where the convection developed.

Simulations were performed using the NCAR-PSU MM5 mesoscale model to assess the impact of forcing at different scales on the modeled pre-storm environment. The model is initialized using a high-resolution land-surface data assimilation system (HRLDAS) to ensure a better surface forcing. Sensitivity studies using different nested domains are conducted to identify the processes that initiate convection at this location. A better understanding of the physical processes in the atmospheric boundary layer affecting convection initiation will allow for the improvement of forecasting of such storms that can cause serious damage.