Ronald Stewart

    Dr. Ronald Stewart

    Department of Environment and Geography, University of Manitoba

    Research areas

    Precipitation is one of the most critical issues for CCRN because it is directly related to numerous types of extremes and it plays a central role for driving many hydrological and ecological processes. Given its importance, the objective of my research has been to examine factors leading to precipitation (and related extremes) as well as its future occurrence.

    The strategy to accomplish this has utilized several developments. These included the examination of recent precipitation-related extremes, the utilization of new high resolution modelling products, as well as the acquisition of special precipitation information.

    Some of the most significant progress resulted from collaborative studies of recent events. The best example is the 2013 Alberta floods. I do not recall a comparable atmospheric effort being mounted on a single event before; several studies revealed key features of the complex chain-of-events leading to the precipitation. A collaborative effort was carried out with the 2014 NWT forest fires to again highlight a cascade of responsible factors. Connections between extremes are also critical such as in 2009-11 when regions with little and substantial precipitation were sustained simultaneously and led to, for example, 2011 Assiniboine flooding.

    Studies were carried out of the occurrence of freezing precipitation across the CCRN domain. This was documented in unprecedented detail and it was shown that chinook flows can lead to such conditions and that only 5 occurrence patterns over the annual cycle are possible. This somewhat overlooked issue is now being examined countrywide.

    Despite its importance, relatively few measurements have been made of the detailed nature of precipitation and its lower tropospheric driving mechanisms. To begin to address this, a modest 2015 field project in Kananaskis was carried out. Through the analysis of the ensuing information, it was found that there are many means through which precipitation in its numerous forms was produced (often simultaneously) although accretion is often critical.
    Exploratory work has been carried out on future changes. This utilized CMIP5 information to consider how large scales may change to drive future precipitation extremes. There may well be more Assiniboine floods and more forest fires across the region. The analyses also led to several studies utilizing the WRF pseudo-global warming dataset. In general, more precipitation would fall although, such as in the 2013 Alberta flooding situation, this would not necessarily occur in the same locations and so enhanced flooding would not necessarily follow.

    Progress has had to overcome challenges but substantial output was generated. A major impediment has been accessing, merging and analyzing vast amounts of information. There is a critical need for better information management including online analysis capabilities. Output has been journal articles, conference and public presentations, interviews as well as undergraduate/graduate course lecture material.

    In summary, a good project. New insights on atmospheric and precipitation-related issues have been developed including future occurrences of several related types of extremes.