Agricultural Stress Index (Global - Annual - 1 km ) - FAO ASIS

The Agricultural Stress Index (ASI) is a quick-look indicator that facilitates the early identification of cropped land with a high likelihood of water stress (drought). ASI related products (maps, spatial aggregation based on administrative unit) are processed by FAO GIEWS (Global Information and Early Warning System on Food and Agriculture) every 10 days. ASI Annual Summary is processed at the end of crop season, globally defined as 30 June. It depicts the percentage of arable land, within an administrative area, that has been affected by drought conditions over the entire cropping season. It differs from ASI dekadal product (10-days), which is based on conditions from the start of the season up to the current dekad. Phenomenon Mapped: Agricultural Stress Index Units: Percent Time Interval: 1-year Time Extent: 1984-Present Cell Size: 1 km Pixel Type: 32-bit Signed Integer Data Projection: WGS 1984 Mosaic Projection: WGS 1984 Web Mercator Source: Food and Agriculture Organization of the United Nations Update Cycle: Annual, 5th of July for the previous crop year The Index is based on the integration of the Vegetation Health Index (VHI) in two dimensions that are critical in the assessment of a drought event in agriculture: temporal and spatial. The first step of the ASI calculation is a temporal averaging of the VHI, assessing the intensity and duration of dry periods occurring during the crop cycle at the pixel level; this calculation includes the use of crop coefficients, which introduces sensitivity of a crop to water stress during each phenological phase. The second step determines the spatial extent of drought events by calculating the percentage of pixels in arable areas with a VHI value below 35 percent (this value was identified as a critical threshold in assessing the extent of drought in previous research by Kogan, 1995). Each administrative area is classified according to the percentage of the affected area to facilitate the quick interpretation of results. This index is computed in two temporal granularities: Near Real Time (10 days) and Annual Summary. Historic Drought Frequency dataset is also computed based on the entire ASI Annual Summary datasets (1984-2021). Explore this and related data in this web application. More information please visit FAO GIEWS Earth Observation website农业压力指数（Agricultural Stress Index, ASI）是一款快速研判指标，可辅助早期识别存在较高水分胁迫（干旱）风险的耕地。与ASI相关的产品（包括地图、基于行政单元的空间聚合数据）由联合国粮食及农业组织（Food and Agriculture Organization of the United Nations, FAO）旗下的全球粮食及农业信息与预警系统（Global Information and Early Warning System on Food and Agriculture, GIEWS）每10天处理更新一次。年度ASI汇总数据于作物季结束时生成，全球统一的作物季截止日期为6月30日。该汇总数据展示了某一行政区域内，在整个作物季受干旱影响的耕地占比，其与每10天更新的ASI旬度产品存在显著差异：旬度产品统计的是从作物季开始至当前旬度的干旱状况。 ### 数据集基础信息 制图对象：农业压力指数 单位：百分比 时间间隔：1年 时间范围：1984年至今 像元分辨率：1千米 像素类型：32位有符号整数 数据投影：WGS 1984 镶嵌投影：WGS 1984 Web墨卡托（WGS 1984 Web Mercator） 数据源：联合国粮食及农业组织 更新周期：年度更新，每年7月5日发布上一作物季的汇总数据。 该指数基于植被健康指数（Vegetation Health Index, VHI）在农业干旱评估中至关重要的两个核心维度——时间与空间维度的融合构建。ASI的计算分为两步：第一步为像元级的VHI时间平均，用于评估作物生长周期内干旱时段的强度与持续时长；该计算过程引入了作物系数，从而使指数能够反映作物在各物候期对水分胁迫的敏感性差异。第二步则通过计算耕地区域内VHI值低于35%的像元占比，确定干旱事件的空间范围（该临界阈值由Kogan于1995年的既往研究中确定）。每个行政区域会根据受影响面积占比进行分级，以方便快速解读结果。 该指数支持两种时间粒度的计算模式：近实时（10天周期）与年度汇总。历史干旱频率数据集同样基于1984-2021年的全部ASI年度汇总数据生成。您可通过本Web应用探索该数据集及相关数据。如需了解更多信息，请访问FAO GIEWS地球观测网站。