PESSACG Natalia Liz
congresos y reuniones científicas
Predictability Study of a Baroclinic Wave: Comparison between a Real Case and Idealized Experiment
J. BLAZQUEZ; N. L. PESSACG; P. L. GONZÁLEZ
Foz de Iguazu
Congreso; The Meeting of the Americas AGU; 2010
American Geophysical Union
This work presents the results of a sensitivity study to perturbations in the initial conditions in the simulation of an observed cyclogenesis affecting southeastern South America. The WRF (Weather Research and Forecasting) regional model was used for simulating the real case, using GDAS (Global Data Assimilation System) as boundary and initial conditions. Both the analysis and the model output were able to reproduce the main features of the different stages of the cyclogenesis´ development. Several perturbation structures were considered, ranging from random to sinusoidal noise, and they were applied to different atmospheric variables. The results of the previous analysis were compared with those obtained for an idealized case. This set of experiments was also performed using WRF model. In this case, WRF´s module for idealized simulations was considered, in particular, the case of a 3D baroclinic wave on a baroclinically unstable jet on an f-plane. In addition, the effect of changing the parameterizations was also evaluated. The case of the idealized cyclogenesis revealed that the errors showed a maximum growth when the perturbations were applied to temperature fields. In particular, when the convective scheme was turned off, the growth of the errors was more dependent on the perturbations´ structure than the variable they were applied to, the biggest increases were observed for the sinusoidal perturbations. The results also show the existence of a direction of maximum error growth for this particular case, since the errors tended to organize with the same structures throughout the experiments. The comparison between the real case and the idealized experiment allowed evaluating the differences between the evolution of the errors focusing in the sensitivity to perturbations and the direction of maximum growth observed in each case. The results also provide knowledge about the limit of predictability in the case of an unstable baroclinic wave related to error growth associated with small-scale motions and the transfer to larger scales.