Global Wet-Dry Cycles (Mean Annual Count) ERA5
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Map Information
This raster represents the average annual number of dry-to-wet transitions derived from daily total precipitation. A dry day is defined as precipitation < 1 mm, and a wet day is defined as precipitation ≥ 1 mm. A wet–dry cycle is counted when a dry day is immediately followed by a wet day.
Data Legend
Location Analysis
Technical Specifications
This dataset represents the global mean annual number of wet-to-dry transition cycles per year, derived from ERA5 reanalysis precipitation data for the period 2020–2024.
A wet–dry cycle is defined as a transition from a dry condition to a wet condition based on a precipitation threshold.
Hourly ERA5 data were used, including:
Total precipitation (tp)
A wet condition is defined as:
Precipitation ≥ 1 mm (0.001 meters)
Wet–dry transitions were calculated at each grid cell by identifying time steps where precipitation changes from below the threshold (dry) to equal to or above the threshold (wet).
Annual wet–dry cycle rasters were generated for each year (2020–2024) by summing all transition events. A mean annual wet–dry cycle raster was then computed as the average across all five years.
The dataset is provided in:
Native ERA5 spatial resolution (~0.25°, ~27–31 km), and
Resampled ~1 km resolution (bilinear interpolation)
For tile-based web visualization and scoring applications, a tileview version of the dataset is generated in which:
All zero values are replaced with 0.001 to ensure stable rendering and prevent numerical issues in downstream processing.
Units:
Cycles per year (cycles/year)
Spatial Reference:
WGS 84 (EPSG:4326)
Temporal Coverage:
January 1, 2020 – December 31, 2024
Data Source:
ERA5 hourly reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), accessed via the Copernicus Climate Data Store (CDS)
Data Distribution Analysis
These histograms show the distribution of pixel values across the entire raster dataset, helping you understand the range and frequency of different measurements.