Dry Spells in Brazil: Observations and Modelling (CMIP5)

Abstract In South America, the water disponibility in several regions is a limit condition on socioeconomic development. More constant impacts are observed in social and economic areas due to the drought, for example, in the Northeast of Brazil (NEB) and Central West of Brazil (COB), mainly in activities such as agriculture, animal husbandry, electricity distribution and Water supply and tourism. The objective of this work is to investigate quantitatively and qualitatively the characteristics of five and ten day dry spells in Brazil during the southern seasons and the relation of these drought events in climatic contrasts such as El Niño, La Niña in the Tropical Pacific (1971-1999) and future period (2021-2050) with the aim of improving the knowledge of the seasonal variation of rainfall in the country with emphasis on the dry spells to potentiate socioeconomic actions that depend on their variability with less scratches. Data of daily precipitation (1971-1999) from the National Center Environment Prediction - Climate Prediction Center - NCEP - CPC of the National Oceanic and Atmospheric Administration (NOAA) of the United States on Brazil were used in grid points (1° x 1° of latitude and longitude). For the comparisons with these observed data and for the future periods will be used of the CMIP5 (Coupled Model Intercomparison Project 5th Phase) project, using daily precipitation data of models in the periods 1971-1999 and projected for the Period: 2021-2050, with configurations of the RCP8.5 experiment to analyze the current observed variability of in Brazil and its future projections. The results showed that for the period 2021-2050 compared to the 1971-1999 observations, the CMIP5 models projected a higher probability of more 10 events to dry spells of ten days in the COB and more events minor or equal the five days to five days dry spells over the NEB to summer and autumn season.

摘要：在南美洲，多个区域的水资源可获得性已成为制约社会经济发展的关键瓶颈。干旱对社会经济领域造成的持续性影响尤为突出，例如巴西东北部（Northeast of Brazil, NEB）与巴西中西部（Central West of Brazil, COB）的农业、畜牧业、电力供应、供水服务及旅游业均受其严重冲击。本研究旨在定量与定性分析巴西南半球季节内5天连旱期与10天连旱期的特征，并探讨1971-1999年热带太平洋厄尔尼诺、拉尼娜气候背景下此类干旱事件的关联，以及2021-2050年的未来变化趋势，以期深化对巴西降雨季节变化规律的认知，重点聚焦连旱期特征，助力依赖降水变异性的社会经济活动降低其受干旱影响的损失。本研究使用美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）下属国家环境预测中心-气候预测中心（National Center for Environmental Prediction - Climate Prediction Center, NCEP-CPC）提供的1971-1999年巴西区域逐日降水格点数据，空间分辨率为1°×1°经纬度。为对比验证上述观测数据并开展未来时段分析，本研究采用第五阶段耦合模式比较计划（Coupled Model Intercomparison Project Phase 5, CMIP5）的模式数据，包含1971-1999年的模式逐日降水数据与2021-2050年的预估降水数据，并设置RCP8.5典型浓度路径试验方案，以此分析巴西当前观测到的降水变异性及其未来预估结果。结果显示，相较于1971-1999年的观测时段，CMIP5模式预估在2021-2050年期间，巴西中西部（COB）的10天连旱事件发生概率显著提升，且出现10次以上的10天连旱事件；而巴西东北部（NEB）在夏季与秋季的5天连旱期，其5天及以下连旱事件的发生数量明显增多。