Characterizing the Predictability and Sensitivity of Streamflow to Monsoon Season Precipitation

Research Need: In the Western US, warm-season precipitation has historically provided a secondary water source to snowmelt runoff (Serreze et al., 1999). However, increasing temperatures and decreasing snowpack suggest that it may gain importance for water resources management. As such, there is an interest in understanding the predictability of warm-season precipitation, as well as the sensitivity of water resources and management to this source.

Understanding the predictability of warm-season precipitation is of particular interest in the U.S. Southwest, a region that is influenced by the North American Monsoon in summer (Adams and Comrie 1997). One of the barriers to using monsoon forecasts has been their low skill in simulating precipitation. However, it has been recommended that any examination of monsoon should consider large-scale circulation, rather than examining precipitation directly (Seneviratne et al. 2012). To this point, Prein (2019) identified large-scale conditions over the U.S. Southwest associated with monsoon precipitation anomalies, and found that they are robustly captured by NCAR’s Community Earth System Model (CESM) and other general circulation models. This provides motivation to evaluate monsoon circulation patterns in forecast ensemble products.