未来气候变化对我国南方水稻主产区季节性干旱的影响评估

研究我国水稻主产区季节性干旱受未来气候变化的影响, 对调整水稻种植布局、提高水稻生产适应气候变化能力具有重要意义。本文通过对比时间跨度为1981-2030 年水稻生产可用水量和季节性干旱的时空分布和干旱程度, 得出气候变化对未来我国水稻主产区季节性干旱有显著影响。主要结论有:2001-2030 年(对照期) 与1980-2000 年(基准期) 对比, (1) 早稻和晚稻生长季可用水量均值增加了10%以上, 中稻生长季可用水量保持不变。同时, 中稻和晚稻的生长季可用水量的空间分布更加均匀, 表明由于气候变化的影响, 水稻主产区水稻生长季可用水量从整体上会更加充沛、空间分布会更加均匀, 有利于缓解季节性干旱的发生。(2)水稻的季节性干旱均呈下降趋势, 早稻季节性干旱减少1.25 万km², 中稻季节性干旱减少8.00万km², 特别是晚稻季节性干旱减少25 万km², 几乎占晚稻种植面积的20%。表明由于气候变化的影响, 水稻主产区水稻季节性干旱总体趋于缓解, 特别是晚稻季节性干旱问题有明显改善。(3) 通过建立水文循环过程中可用水量与作物生长季需水量之间的关系, 构建的基于分布式水文模型的水分供需指数(WSDI) 适用于评估未来气候对水稻主产区季节性干旱的影响。

Assessing Climate Change Impact on Seasonal Drought in Main Rice Cropping Regions in the South of China

Impact of climate change on seasonal drought in main rice cropping regions in China is important for adjusting rice planting pattern and improving adaptation ability. By comparing the level and spatial and temporal distribution of available water and seasonal drought during 1981-2030, this paper assesses impact of climate change on seasonal drought in main rice cropping regions in the south of China. The results are shown as follows. (1) The mean available water of early rice and late rice will increase by more than 10% in the growing season, while mean available water of medium rice will keep invariant. Meanwhile, the spatial distribution of available water of early rice and later rice becomes more homogeneous. This means that, due to climate change, available water of main rice cropping regions generally in the growing season will be more abundant, and spatial distribution of available water is more homogeneous, which is conductive to mitigate seasonal drought. (2) The area of seasonal drought of early rice will reduce by 12,500 km², medium rice by 80,000 km², and especially later rice will decrease by 250,000 km², accounting for 20% of the planting area of later rice. This means that, under climate change, the seasonal drought on the whole will tend to weaken, especially seasonal drought of later rice will obviously be weakened. (3) Based on the relationship between available water from hydrologic circulation process and water demands for crop growing season, the Water Supplies and Demands Index (WSDI) is suitable for assessing the impact of climate change on seasonal drought in main rice cropping regions.