西南地区是中国玉米主要产区之一，干旱是该地区最主要的农业气象灾害，研究干旱时空分布特征及规律对西南地区玉米种植布局和防旱减灾有重大意义。该文收集西南地区玉米种植区60个代表气象站50a（1960年-2010年）的气象资料和玉米作物资料，选用基于土壤-植被-大气系统并以天为时间尺度的农业干旱参考指数（ARID）作为干旱指标，研究西南地区玉米生育期内干旱频率空间分布特征，并分析近50a干旱发生的年代际变化，验证ARID在西南地区的适用性。结果表明：1）近50a来西南地区发生的干旱具有显著的区域特征，高发区位于云南中北和东北部以及四川南部；其次为川东北的广元地区、川西南山地以及滇西北、滇南部的元江地区；少发区位于重庆大部、贵州北部等地区。2）阶段性干旱明显，受旱频率最高的时段为出苗至拔节期，受旱频率最低在抽雄至灌浆期，且随着发育进程，干旱有向东部转移的趋势。3）西南地区各分区玉米生长季内ARID变化差异较大，总体上来看干旱程度大多处于轻旱，个别区域处于中旱，或者在轻旱与中旱之间波动。4）ARID的年际变化特征表明：20世纪80年代受干旱影响最低，21世纪初受干旱影响最严重。%Maize, as a major grain crop in Southwest China, has contributed significantly to total grain production in the region. Drought is the most prominent agro-meteorological disaster which poses serious threat to maize production. Therefore, it is important to analyze its temporal and spatial distribution characteristics and occurring regularities to provide technical supports for disaster prevention and reasonable layout of maize production in Southwest China. In this study, daily meteorological data, collected from 60 stations in maize planting areas of Southwestern China during 1960-2010, were used to calculate the Agricultural Reference Index for Drought (ARID) which computed daily and based on three important factors (soil ,vegetation and atmosphere). The spatial distribution of drought frequency at maize growth periods and annual variations of drought in recent 50 years were analyzed to validate the application of ARID in this region. The results showed there were obviously regional characteristics in recent 50 years. Drought happened most frequently in north center and northeast of YunNan and south of SiChuan,followed by GuanYuan of SiChuan areas, mountains of southwestern SiChuan, northwestern YunNan, YuanJiang and its surrounding areas. Areas with the lowest incidence of drought mainly located in the most regions of ChongQing, the north of GuiZhou and other regions. Drought occurred with the highest frequency at the stage of emergence to jointing and the lowest frequency at the stage of tasseling to filling. In addition, with the development of the growth, drought occurrence had the tendency to move to the east. ARID extremely differed in sub-regions of Southwestern China during maize growing periods. In general, light drought happened in higher frequency than moderate and severe drought. Specifically, only a few regions were moderate drought or fluctuated between light drought and moderate drought. The inter-annual change feature of ARID showed that drought was light in 1980s and became more serious at the beginning of the 21st century.
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