The Office of Graduate Programs is pleased to announce that Aseem Sharma will be defending their dissertation entitled “Role of Atmospheric Rivers on the Hydrology of Western Canada” as a candidate for the degree Doctor of Philosophy in Natural Resources and Environmental Studies. We encourage you to view the defence online. The details on the defence and how to join are included below.

DATE:                                    April 17, 2020

TIME:                                    10:00 AM

LINK TO JOIN:                      Meeting URL https://bluejeans.com/837170936?src=join_info Meeting ID 837 170 936

To ensure the defence proceeds with no interruptions, please mute your audio and video on entry and do not share your screen inadvertently.  The meeting will be locked to entry 5 minutes after it begins, ensure you are on time.

Atmospheric rivers (ARs) are synoptic-scale atmospheric phenomena that transport moisture from the (sub)-tropical regions of the Pacific Ocean to British Columbia and southeastern Alaska. Despite the substantial role of ARs on water resources in this region, understanding of their climatology and contributions to hydrology remains limited. I use a combination of a regional AR catalog, reanalysis datasets, gridded precipitation, observed river runoff data, and topographic information, to provide insights on the climatology of landfalling ARs (LARs) and to quantify changes in the contribution of LARs to the precipitation, river runoff, and their extremes in British Columbia and southeastern Alaska (BCSAK). Each year BCSAK experiences 35±5 LARs with the highest number in autumn (13±2) and an average duration of 2±1.8 days. The frequency of LARs significantly increases (p <0.05) at 1.8 events decade-1 during 1979-2016. Higher numbers of LARs occur during the neutral phase of El Niño-Southern Oscillation, the positive phases of the Pacific Decadal Oscillation and the Pacific-North American Pattern, and the 2013/2014 Pacific oceanic blob years. LARs contribute 13% of annual total precipitation with higher contributions (up to 33%) along coastal regions with more modest values (~9%-15%) in the Interior Mountains during 1979-2012. LARs contribute >90% (spatial range: <5%-97%) of annual extreme precipitation in BCSAK during 1979-2012 with the higher values over elevated terrain.

AR-related precipitation days increase significantly during 1979-2012. LARs contribute 14±6% (spatial range: 3%-29%) of the total annual runoff in BCSAK during water years

(WYs) 1979-2012. Coastal watersheds experience >80% of their annual maximum runoff from LARs during WYs 1979-2016. ARs control the distribution of peak runoff in most of BCSAK with >60%of the 168 watersheds analyzed having greater than five of the top 10 annual maxima runoff associated with them. Local (field) significance tests show that AR-related annual maximum runoff magnitude is significantly higher than non-AR-related annual maximum runoff for 30% (17%) of the watersheds studied. My work quantifies the linkages between ARs and their impacts on hydrological processes across BCSAK that has broader implications on community water supply and management, hydropower operations,  and flood risk assessment and mitigation.