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Soil climate of the Canadian system from climate normals

Source: R/npdb-scenario.R
npdb_soil_climate.Rd

Estimates, from monthly climate normals (as returned by fetch_aafc_normals), what the Canadian System of Soil Classification reads as the soil climate (Ch 2, p. 16, criterion 7 of the chernozemic A; the soil temperature classes and moisture subclasses of its Tables 3 and 4, after the map Soil Climates of Canada, Clayton et al. 1977):

  • the mean annual air temperature (MAAT, the mean of the twelve monthly means) and, for the mean annual soil temperature (MAST), the range from the MAAT to the MAAT plus mast_offset degrees: in Canada the soil under snow is warmer than the air;

  • the climatic moisture index (CMI) of Table 4, the growing-season precipitation as a percentage of the water crops would use: here the precipitation over the potential evapotranspiration (PET) of the months of the growing season (April to October) whose mean temperature is above 5 degrees. The PET is computed in two ways: by Thornthwaite (monthly mean temperatures and day length), the central estimate, which matches the zones the book gives the Chernozem great groups on the NPDB (Brown subarid to semiarid, Dark Brown semiarid, Black and Dark Gray subhumid); and by Hargreaves and Samani (monthly minimum and maximum temperatures and extraterrestrial radiation), the other end of the range (on the NPDB mostly drier, sometimes wetter);

  • the moisture subclass from each index (Table 4): perhumid above 84, humid 74-84, subhumid 59-73, semiarid 46-58, subarid 25-45, arid below 25.

Usage

npdb_soil_climate(normals, mast_offset = c(0, 4))

Arguments

normals

A data frame with id, lat and the columns of fetch_aafc_normals.

mast_offset

The range added to the MAAT for the MAST, in degrees (two numbers, read from the lower to the higher).

Value

A data frame: id, maat, mast_lo, mast_hi, p_gs (mm), gs_months, pet_gs and cmi and moisture_subclass (Thornthwaite), pet_gs_hargreaves, cmi_hargreaves and moisture_subclass_hargreaves.

References

Soil Classification Working Group (1998). The Canadian System of Soil Classification, 3rd ed., Tables 3 and 4. Clayton, J.S. et al. (1977). Soils of Canada. Thornthwaite, C.W. (1948). Geographical Review 38: 55-94. Hargreaves, G.H., Samani, Z.A. (1985). Applied Engineering in Agriculture 1: 96-99. Allen, R.G. et al. (1998). FAO Irrigation and Drainage Paper 56.