🌧️ Online climate anomaly (SPI)
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Online climate anomaly SPI — drought and wetness, no software, in under a minute
A Moroccan platform to compute the Standardized Precipitation Index (SPI) of any study station: precipitation is accumulated over 1 to 24 months and compared with the reference period to identify dry and wet months and drought episodes, their duration and severity. No GIS software, no tables to process: pick the location and period.
- Daily ERA5-Land precipitation since 1950
- Gamma distribution and class classification according to the WMO
- Automatic detection of drought episodes, their duration and severity
- Free Word report for approved orders
How does it work?
- Choose a point: Click on the map to select the study station.
- Set the timescale and periods: Choose the timescale (1–24 months), the displayed period and the reference period (30 years recommended).
- Compute and customize: Click "Compute SPI", adjust the colours, then download.
Who is it for?
- Meteorology, hydrology and water-resource management
- Agriculture, crop insurance and drought early warning
- Theses, study reports and teaching
- Planning, environment and climate change
Related tool: Gaussen diagram (dry and wet months)
Frequently asked questions
How do I calculate the SPI of my site?
Click a point on the map, choose the timescale (1 to 24 months), the displayed period and the reference period, then press "Compute SPI". The chart appears in under a minute with monthly bars coloured by drought or wetness class.
What do SPI values mean?
The SPI expresses the deviation of precipitation from normal in standard deviations: negative values mean drought, positive values wetness. According to the WMO classification: ≤ −2 extremely dry, −1.5 to −1.99 severely dry, −1 to −1.49 moderately dry, −0.99 to 0.99 near normal, and symmetrically for wetness.
Which timescale should I choose?
SPI-1 to SPI-3 for meteorological and agricultural drought (soil moisture), SPI-6 for agricultural–hydrological drought, SPI-12 to SPI-24 for hydrological drought (streamflow, reservoirs, groundwater).
What is the reference period?
It is the period on which the gamma distributions are fitted to define "normal". The WMO recommends at least 30 years; the default here is 1991–2020. The reference period is independent of the displayed period.
Is the platform free?
Generation, preview and customization are free. The watermark-free PNG and the Word report require an approved order (5 image downloads per order; the report is free for the holder of an approved order).
What is the data source?
ERA5-Land reanalysis (Copernicus / ECMWF): daily precipitation totals, available since 1950 via Open-Meteo. Values are aggregated monthly and then converted to SPI.