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Swiss monthly vegetation condition

Vegetation condition is a standardized indicator, shown here over the whole country so it serves farmland as readily as forest, that compares current vegetation condition with the long-term average for the same calendar month, derived from monthly Sentinel-2 Level-2A Surface Reflectance composites (June–August, 2017–present) after cloud and shadow masking. It combines four vegetation indices (NDVI, GNDVI, NDRE and NDWI), capturing vegetation greenness, chlorophyll content and canopy water status. By comparing each month against historical conditions for the same month (leave-one-out), the indicator removes normal seasonal cycles and highlights where vegetation is performing better or worse than usual.

Interpretation

> +2 – Very healthy vegetation

Much better condition than the long-term average for that month (>2 standard deviations above the mean).

+1 to +2 – Healthy vegetation

Better-than-average condition (1–2 standard deviations above the mean).

−1 to +1 – Typical vegetation condition

Close to the long-term average (within ±1 standard deviation).

−2 to −1 – Moderately stressed vegetation

Below-average condition (1–2 standard deviations below the mean).

< −2 – Severely stressed vegetation

Much poorer condition than the long-term average (>2 standard deviations below the mean).

Note

A relative indicator, not an absolute measure of vegetation health or drought severity. Differences from the long-term average may reflect drought, heat stress, pests, disease, storm damage or forest management, and should be interpreted alongside local conditions and complementary datasets.

Vegetation indices

NDVI (Normalized Difference Vegetation Index)

$$\frac{\text{B8}-\text{B4}}{\text{B8}+\text{B4}} = \frac{\text{NIR}-\text{Red}}{\text{NIR}+\text{Red}}$$Values close to +1 indicate dense, healthy vegetation, values around 0 indicate sparse vegetation or bare soil, and values < 0 typically represent water, snow or clouds.

GNDVI (Green Normalized Difference Vegetation Index)

$$\frac{\text{B8}-\text{B3}}{\text{B8}+\text{B3}} = \frac{\text{NIR}-\text{Green}}{\text{NIR}+\text{Green}}$$Higher values indicate greater chlorophyll content and photosynthetic activity, while lower values indicate sparse or stressed vegetation.

NDRE (Normalized Difference Red Edge Index)

$$\frac{\text{B8A}-\text{B5}}{\text{B8A}+\text{B5}} = \frac{\text{NIR}-\text{RedEdge}}{\text{NIR}+\text{RedEdge}}$$Higher values indicate healthy, chlorophyll-rich vegetation, while lower values may indicate vegetation stress or senescence.

NDWI (Normalized Difference Water Index)

$$\frac{\text{B8}-\text{B11}}{\text{B8}+\text{B11}} = \frac{\text{NIR}-\text{SWIR}}{\text{NIR}+\text{SWIR}}$$Higher values indicate greater canopy water content, while lower values indicate drier vegetation or water stress.

Standardization

Standardized index

$$z_i = \frac{x_i - \mu_i}{\sigma_i}$$where $x_i$ is the vegetation index value for the selected year; $\mu_i$ is the historical monthly mean calculated from all other available years for the same calendar month (leave-one-out); $\sigma_i$ is the corresponding historical monthly standard deviation.

Vegetation Condition

$$V.\text{condition} = \frac{z_{NDVI}+z_{GNDVI}+z_{NDRE}+z_{NDWI}}{n} = \frac{\sum_{i=1}^{n} z_i}{n}$$where $n$ is the number of valid vegetation indices available for each pixel ($1 \le n \le 4$). If one or more vegetation indices are unavailable, the Vegetation Condition is calculated using only the available standardized indices.

Data source

Satellite

Sentinel-2 Level-2A Surface Reflectance (COPERNICUS/S2_SR_HARMONIZED).

Spatial resolution

20 m.

Temporal resolution

Monthly median composites (June–August, 2017–present).

Cloud masking

QA60, Scene Classification Layer (SCL), Cloud Score+ (cs_cdf ≥ 0.70) and scenes with ≤20% cloud cover.

-2-1012

StressedHealthy

z-score against the same month, 2017–2026.

Month

Index

Map year

Opacity 100%

Mean inside a 50 m buffer, one line per month.