geoskill-drought-severity-assessment

干旱严重度评估 | Drought Severity Assessment

A combined drought assessment fusing meteorological (precipitation) and remote-sensing vegetation information, suitable for regional drought monitoring, agricultural drought early warning, and time-series drought comparison. It implements two complementary indices:

• SPI (Standardized Precipitation Index): fits a Gamma distribution to the precipitation series (including the mixed zero-precipitation probability p0), then applies the standard-normal inverse (via norm.ppf) to the cumulative probability. SPI < 0 indicates drier-than-normal conditions; the larger the absolute value, the drier. Its distribution approximates the standard normal.
• VHI (Vegetation Health Index): based on the standardized NDVI anomaly (current NDVI relative to the multi-year mean / standard deviation). A negative anomaly indicates vegetation stress (agricultural drought).

SPI and VHI are combined with equal weights into a composite drought index (both are approximately standard-normal), then classified by thresholds into five grades: no drought / mild / moderate / severe / extreme. Outputs a drought-grade raster, an SPI raster, and per-grade area statistics.

--synthetic mode generates multi-epoch precipitation + NDVI data (precipitation plunges and NDVI drops in the right-side region at the final epoch, simulating a regional meteorological–agricultural drought), letting you validate the workflow without network access or real data.

Dependencies / 依赖

pip install numpy rasterio scipy

Usage / 使用方法

Basic usage (synthetic data, offline)

python geoskill-drought-severity-assessment.py --bbox 116.0 39.0 117.0 40.0 --n-dates 12 --output-dir ./output

Example 1: drought assessment on synthetic data

python geoskill-drought-severity-assessment.py \
    --bbox 116.0 39.0 117.0 40.0 \
    --n-dates 12 \
    --synthetic \
    --output-dir ./drought_syn

Example 2: more time steps

python geoskill-drought-severity-assessment.py \
    --bbox 116.0 39.0 117.0 40.0 \
    --n-dates 24 \
    --synthetic \
    --output-dir ./drought_24

Example 3: real precipitation time series

python geoskill-drought-severity-assessment.py \
    --input precip_monthly.tif \
    --output-dir ./real_drought

(The input is a multi-band GeoTIFF, one band per precipitation epoch; this mode grades with SPI only.)

Example 4: different region

python geoskill-drought-severity-assessment.py --bbox 121 31 122 32 --n-dates 12 --synthetic --output-dir ./shanghai --quiet

Output / 输出

Data Source / 数据源 / Source

• Precipitation: local multi-band GeoTIFF, or from CHIRPS / GPM IMERG / station interpolation
• NDVI: generated in synthetic mode; real applications may use MODIS / Landsat time series
• Synthetic mode: generated locally, no external data source

Privacy / 隐私声明 / Privacy

• Runs fully offline by default and makes no network requests
• --synthetic mode reads no external data
• All computation is done locally; no user data is uploaded

License / License

MIT

---

---

name: geoskill-drought-severity-assessment description: '融合 SPI（标准化降水指数，Gamma 分布拟合+正态反演）与 VHI（植被健康指数）的综合干旱分级。Combined drought grading fusing SPI (Gamma-fit standardized precipitation index) and VHI (vegetation health index). 输出干旱等级/SPI 栅格 + 面积统计 JSON。'

干旱严重度评估 | Drought Severity Assessment

融合气象（降水）与遥感植被信息的综合干旱评估，适用于区域旱情监测、农业干旱 预警、时序旱情对比等场景。实现两个互补指数：

• SPI（Standardized Precipitation Index，标准化降水指数）：对降水序列拟合 Gamma 分布（含零降水混合概率 p0），经累积概率后用标准正态反演 （norm.ppf）。SPI < 0 表示偏干，绝对值越大越干；其分布近似标准正态。
• VHI（Vegetation Health Index，植被健康指数）：基于 NDVI 标准化距平 （当期 NDVI 相对多年均值/标准差）。负距平表示植被受胁迫（农业干旱）。

将 SPI 与 VHI 等权合成为综合干旱指数（两者均近似标准正态），按阈值分为五级： 无旱 / 轻旱 / 中旱 / 重旱 / 特旱。输出干旱等级栅格、SPI 栅格与逐等级面积统计。

支持 --synthetic 模式生成多期降水 + NDVI 数据（右侧区域末期降水骤降、NDVI 下降，模拟一场区域性气象—农业干旱），无需网络和真实数据即可验证流程。

依赖

pip install numpy rasterio scipy

使用方法

基本用法（合成数据，离线）

python geoskill-drought-severity-assessment.py --bbox 116.0 39.0 117.0 40.0 --n-dates 12 --output-dir ./output

示例 1：合成数据干旱评估

python geoskill-drought-severity-assessment.py \
    --bbox 116.0 39.0 117.0 40.0 \
    --n-dates 12 \
    --synthetic \
    --output-dir ./drought_syn

示例 2：更多时间步

python geoskill-drought-severity-assessment.py \
    --bbox 116.0 39.0 117.0 40.0 \
    --n-dates 24 \
    --synthetic \
    --output-dir ./drought_24

示例 3：真实降水时间序列

python geoskill-drought-severity-assessment.py \
    --input precip_monthly.tif \
    --output-dir ./real_drought

（输入为多波段 GeoTIFF，每个波段 = 一期降水；此模式仅用 SPI 分级。）

示例 4：不同区域

python geoskill-drought-severity-assessment.py --bbox 121 31 122 32 --n-dates 12 --synthetic --output-dir ./shanghai --quiet

输出

数据源 / Source

• 降水：本地多波段 GeoTIFF，或来自 CHIRPS / GPM IMERG / 地面站点插值
• NDVI：合成模式生成，真实应用可来自 MODIS / Landsat 时序
• 合成模式：本地生成，无外部数据源

隐私声明 / Privacy

• 默认完全离线运行，不发起任何网络请求
• --synthetic 模式不读取任何外部数据
• 所有计算在本地完成，不上传用户数据

License

MIT