Ciclo diurno da precipitação no Nordeste do Brasil

Abstract

Understanding and simulating the daily cycle of precipitation in a region is important for weather forecasting and for evaluating the efficiency of dynamic models of the climate system. Few works have investigated the behavior of the diurnal cycle of precipitation in the region of the NEB and, knowing that the evaluation of the diurnal cycle of precipitation is an important test for the analysis of consistency of a regional dynamic model, the objective of the present work is to analyze the characteristics of the diurnal cycle of precipitation over the NEB from the perspective of in situ observations and with regional dynamics modeling. The simulations were carried out with the Regional Climate Model version 4.6 (RegCM4.6) in different periods. For the evaluation of the simulations, three years (2009, 2012 and 2014) of data were chosen, which are years considered wet, dry and neutral respectively. The validation of the simulation data in relation to the observed data was carried out through statistical tests such as: ANOVA, F Test and t-Student Test; Mean Absolute Error (MAE) and Root Square Error (RMSE), Probability of Detection (POD) and False Alarm Ratio (FAR); and correlations (Pearson and Kendall). Precipitation observations were obtained from 76 automatic stations managed by the Instituto Nacional de Meteorologia (INMET). According to the results, the behavior of the diurnal cycle of precipitation is different between the five sub-regions, with rates between 0.05-0.6 mm/h. The model in some sub-regions is not able to represent the behavior of rainfall, due to sensitivity in not following its variation. The RSME and MAE values were lower than 0.08 mm/h, showing the model's dexterity in simulating daily precipitation in the studied regions. It is concluded that the model presented a dry bias, underestimating the observed rainfall and was able to represent the seasonal variation in the three years studied. Furthermore, the best statistical results were found in areas N3 and N4; and in the dry period N1, N2, N3 and N4.