No, it's literally done with a log-normal distribution: https://www.hydrol-earth-syst-sci.net/12/1339/2008/hess-12-1339-2008.pdf https://www.hydrol-earth-syst-s

No, it's literally done with a log-normal distribution: https://www.hydrol-earth-syst-sci.net/12/1339/2008/hess-12-1339-2008.pdf https://www.hydrol-earth-syst-sci.net/12/1339/2008/hess-12-1... Log-normal is extremely common in hydrology. Turns out an anomaly in this case is defined as outside one standard deviation[1], so in a perfectly normal year you would expect ~15.9% of soil to be dryer than normal. [1]: http://edo.jrc.ec.europa.eu/documents/factsheets/factsheet_soilmoisture.pdf http://edo.jrc.ec.europa.eu/documents/factsheets/factsheet_s...