The convection-permitting climate model (CPCM), WRF-ARW at 4 km resolution, is able to capture the observed
relationships between precipitation extremes and temperature (PT scaling) in western Canada. By analyzing the
CPCM simulated PT scalings, we found they have robust patterns at different percentiles of precipitation intensity
and even between the current and future climate. This is due to the stable annual cycle of the regional climate.
The PT scaling pattern is physically governed by the amount of water vapour and the ascending velocity of air.
Approximately 95% of the precipitation intensity variation can be explained by the vertical velocity and precipitable
water in western Canada. The PT scaling for the current climate does not tell how precipitation extremes
would response to a warmer climate. Trend scaling theory was utilized to estimate the intensification of
precipitation extremes in a warmer climate. It shows that, in western Canada, the coast is particularly vulnerable
to precipitation extremes under global warming. Precipitation extremes are projected to increase at a super
Clausius-Clapeyron (CC) scale over the coast, approximately at a CC scale over the prairies and mountains, and a
sub-CC scale over the northern region. The warming effect on precipitation extremes is even stronger when the
concept of  "wet-day trend scaling” is introduced.

Extreme precipitation,The Clausius-Clapeyron relation,PT scaling,Global warming