Melocactus violaceus Pfeiff.

This species’ habitat figures, and what two fixed rules read from them.

The rain rule reads a sharp season: 70% of the year's rain (976 mm of 1316 mm) falls in March to August. The temperature curve is flat, 2.9 °C between the warmest and coldest month, so the growing-season rule does not infer a growing season from it. Months are the habitat's, southern hemisphere; with a flat temperature curve there is no season to reverse, so they are not shifted for a collection elsewhere.

Read from the median year of CHELSA monthly rainfall and mean temperature across the envelope cells: the rain rule takes the smallest set of months carrying 70% of the rain and calls it winter when its mean is more than half a degree below the year's, summer when more than that above, and neither in between; the temperature rule, used only under 120 mm, names the cooler six months when they are at least a degree cooler than the other six. Months are shifted for the other hemisphere only where the temperature curve gives a season to reverse. A reading of the curves, not an observation of the plant.

This species’ habitat figures, with their source.

1316 mm a year at the habitat, 976 mm of it March to August. Wettest month June at 202 mm, driest November at 36 mm. Across the envelope cells the year's total runs 830 mm to 1693 mm (10th to 90th percentile of each cell's own year) (median year across the envelope cells, CHELSA; habitat calendar, southern hemisphere).

CHELSA monthly precipitation, median year across the envelope cells. The rain that falls where the species is recorded; nothing about how the plant takes water.

This species’ habitat figures, with their source.

Open sky over the habitat: 26 to 41 mol/m²/day across the year (daily light integral, median year across the envelope cells, CHELSA; the lowest 10th-percentile month across the cells is 23, the highest 90th-percentile month 43).

CHELSA shortwave radiation at each envelope cell, a daily-mean flux taken to a daily total and converted at 2.07 mol of PAR per MJ. The sky over the habitat, measured; what reaches a plant under a rock, a shrub or a shade cloth is not.

This species’ habitat figures, with their source.

Coldest: the 1st-percentile night over 44 years at the typical cell is 22.9 °C, the absolute minimum 22.1 °C, no frost in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 30.3 °C. Monthly means: coldest night 21.4 °C in August (across the envelope cells 18.3 °C to 23.3 °C), warmest day 28.9 °C in February (median year across the envelope cells, CHELSA). Cold floor: 22.9 °C, which is the 1st-percentile night over 44 years at the typical cell (NASA POWER).

NASA POWER daily minima and maxima 1981–2024 at the typical cell, lapse-corrected to its elevation; CHELSA monthly means, median year across the envelope cells, CHELSA. The cold floor is the figure named in its sentence. Not a measured survival limit for any plant in a pot.

Relative humidity at the habitat: 62 to 65% across the year (monthly means, median year across the envelope cells, CHELSA). A figure about the air, saying nothing about how the plant takes water.

CHELSA relative humidity, median year across the envelope cells.