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Wissmann

The Wissmann scheme partitions climates into six major groups (from Tropical through Polar) and within each applies moisture thresholds to distinguish rainforest, monsoonal, steppe and desert subtypes.

<figure> <img src="assets/outputwissmannexample.svg" alt="Example Wissmann climate regions (groups I–VI with moisture subtypes)" width="100%"> <figcaption><strong>Figure.</strong> Example Wissmann classification map.</figcaption> </figure>

In the provided function, the twelve monthly temperatures and precipitations are first summarized (min, max, mean temperatures; total and minimum precipitation; plus seasonal sums for “winter” and “summer” based on hemisphere). A dynamic precipitation threshold (t_threshold) is computed as ten times the mean annual temperature (shifted by +14 °C if summer is wetter than winter). The main classes are applied with thresholds:

  • Polar — Group VI if t_max < 0 °C; Group V if t_max < 10 °C.
  • Boreal — Group IV when t_mean < 4 °C, with four moisture subtypes (IVF humid, IVT winter-dry, IVS steppe, IVD desert) based on precipitation relative to 1×, 2×, or 2.5× t_threshold.
  • Cool temperate — Group III when t_min < 2 °C, with analogous moisture splits and a winter-vs-summer dry distinction for Ts/Tw subtypes.
  • Warm temperate — Group II when 2 °C ≤ t_min < 13 °C; hot summers (t_max > 23 °C) split Fa/Fb (humid), and Ts/Tw or IS/ID for intermediate/arid regimes.
  • Tropical — Group I when t_min ≥ 13 °C; driest-month check (precip_min ≥ 60 mm) yields IA rainforest, otherwise IF (weak dry period), IT (monsoonal), IS (savanna) or ID (desert) via the same 1–2.5× threshold bins.

How to run it

using Biome
using Rasters

# Minimal inputs
tempfile = "/path/to/temp.nc"   # monthly mean temperature (stacked in 3rd dim)
precfile = "/path/to/prec.nc"   # monthly precipitation (same grid/stacking)

temp_raster = Raster(tempfile, name="temp")
prec_raster = Raster(precfile,  name="prec")

setup = ModelSetup(WissmannModel();
                   temp=temp_raster,
                   prec=prec_raster)

# Process full grid (or pass "lonmin/lonmax/latmin/latmax")
run!(setup; coordstring="alldata", outfile="output_Wissmann.nc")

References

  • Wissmann, H. (1939). In Die Klima- und Vegetationsgebiete Eurasiens: Begleitworte zu einer Karte der Klimagebiete Eurasiens (pp. 81–92). Erdk. Berlin.