Simulated 50% rain-snow air temperature thresholds (linear regression)

Map of simulated 50% rain-snow air temperature thresholds based on a bivariate binary logistic regression phase prediction model applied to 27 years of MERRA-2 reanalysis data. The probability of snowfall was predicted for each precipitation event in the record as a function of air temperature and relative humidity. For each MERRA-2 grid cell, the probabilities were binned by 1°C air temperature bins to produce a snow frequency curve. The 50% rain-snow air temperature threshold was then calculated using a linear regression on snow frequency between 0.5°C and 6.5°C. This approach was used for grid cells without enough snow and rain events to compute the threshold using a hyperbolic tangent.