云南气象和土壤干旱至植被干旱传播的累积与滞后效应

Cumulative and Lag Effects of Meteorological and Soil Drought Propagation to Vegetation Drought in Yunnan

摘要: 愈加频繁和严重的干旱对农业生产和生态环境将造成严重影响。对气象干旱到生态农业干旱间传播的特征，特别是时滞和累积效应进行定量识别，有助于生态农业干旱监测能力的提升。使用ERA5land再分析数据和AVHRR植被指数数据，分别获得气象干旱指数(NSPEI)、土壤干旱指数(SSMI)和植被干旱指数(VHI)，分析云南气象、土壤、植被干旱的时空分布特征，揭示气象干旱到植被干旱、土壤干旱到植被干旱传播的滞后效应和累积效应，并讨论不同下垫面与不同生态地理区的空间异质性及其主导效应。结果表明：云南全境均易发生不同程度的气象干旱，土壤干旱的易发区集中于云南高原的东部和丘陵平原、滇南谷地大部分区域，丘陵平原的北部和云南高原的西部发生植被干旱的频率较高，大部分区域均超过0.2的干旱频率。整体来看，云南气象干旱均呈现不显著变化趋势；土壤干旱显著加重的区域主要集中于川藏高山东部区域、云南高原西侧与东北侧区域；植被干旱显著减缓的区域主要集中于云南高原和丘陵平原的大部分区域。气象干旱和土壤干旱向植被干旱传播的累积时长整体低于滞后时长，川藏高山和云南高原西北部的滞后时间较长(高于18个月)，云南中东部的滞后时间较短(接近1个月)。通过对云南区域不同类型干旱传播过程中累积效应与滞后效应的区域分异性进行分析和主导效应探究，研究结果可为当地农业(植被)干旱的预警提供理论支持。

Abstract: Increasingly frequent and severe droughts will significantly impact agricultural production and the ecological environment. Quantifying the characteristics of drought propagation from meteorological to agroecological droughts, particularly the time lag and cumulative effects, can enhance the monitoring capability of agroecological droughts. Using ERA5-Land reanalysis data and AVHRR vegetation index data, we derived the meteorological drought index (NSPEI), soil drought index (SSMI), and vegetation drought index (VHI) to analyze the spatiotemporal distribution characteristics of meteorological, soil, and vegetation droughts in Yunnan. The study reveals the lag and cumulative effects of drought propagation from meteorological to vegetation drought and from soil to vegetation drought, while also discussing spatial heterogeneity and dominant effects across different underlying surfaces and eco-geographical zones. The results indicate that meteorological droughts of varying severity are prone to occur across Yunnan, while soil droughts are concentrated in the eastern Yunnan Plateau, hilly plains, and most parts of the southern Yunnan valleys. Vegetation droughts occur more frequently in the northern hilly plains and western Yunnan Plateau, with drought frequencies exceeding 0.2 in most areas. Overall, meteorological droughts in Yunnan show no significant trend. Areas with a significant intensification of soil drought are primarily located in the eastern part of the Chuan-Tibet mountains, as well as the western and northeastern sides of the Yunnan Plateau. Areas with a significant mitigation of vegetation drought are mainly found in most parts of the Yunnan Plateau and the hilly plains. The cumulative duration of meteorological and soil drought propagation to vegetation drought is generally shorter than the lag duration. The lag time is longer in the Chuan-Tibet mountains and the northwestern Yunnan Plateau (over 18 months), while it is shorter in central and eastern Yunnan (nearly one month). By analyzing the spatial differentiation of cumulative and lag effects during the propagation of different drought types in Yunnan and exploring their dominant effects, the research results can provide theoretical support for early warning of local agricultural (vegetation) drought.