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Rain-on-snow events over North America based on two Canadian regional climate models

Here, I provide a short summary of a recent research that we undertook to assess climate change impacts on Rain-on-Snow events over North America.

We evaluated projected changes to Rain-on-Snow (RoS) characteristics (i.e., frequency, rainfall amount, and runoff) for the future 2041-2070 period with respect to the current 1976-2005 period over North America using six simulations, based on two Canadian RCMs, driven by two driving GCMs for RCP4.5 and 8.5 emission pathways. Analysis of current and future simulations suggest general increases in RoS characteristics during the November to March period for most regions of Canada and for northwestern US for the future period, due to an increase in the rainfall frequency with warmer air temperatures in future. Future ROS runoff is often projected to increase more than future ROS rainfall amounts, particularly for northeastern North America, during snowmelt months, as RoS events usually accelerate snowmelt. The simulations show that RoS event is a primary flood generating mechanism over most of Canada and north-western and -central US for the January-May period for the current period and this is projected to continue in the future period. More focused analysis over selected basins shows decreases in future spring runoff due to decreases in both snow cover and RoS runoff. The above results highlight the need to take into consideration RoS events in water resources management adaptation strategies for future climate. Minimum, mean, and maximum projected changes to the three RoS characteristics for the January-May months for the future period with respect to the current period, based on the six future RCM-GCM simulations, are presented in Figure 1.

Figure 1. Ensemble averaged values of three RoS characteristics for the January-May months for the current (1976-2005) period (first column) and minimum, mean, and maximum projected changes (%) to the characteristics for the future (2041-2070) period (second-forth columns), based on the three current and six future RCM-GCM simulations, respectively. Zonally averaged values of projected changes to the three characteristics are also shown in fifth column.

Further details can be obtained from

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