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Estimating North American montane snowpack with regional climate model simulations

Wrzesien, Melissa Leigh
http://orcid.org/0000-0003-4958-9234
http://rave.ohiolink.edu/etdc/view?acc_num=osu1522762079858684

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Earth Sciences.
Seasonal snowpack modulates the global hydrological cycle, releasing meltwater in warm months, providing crucial resources for agriculture, ecosystems, and human uses. Despite its importance, global snow storage estimates are highly uncertain, particularly for mountain regions. Observational networks are too sparse to characterize entire mountain ranges, while satellite-based snow observations perform poorly in the mountains. Due to these challenges, the role of snow in the hydrologic cycle at continental scales has never been adequately quantified. Recent advances in regional climate models (RCM) coupled with snowpack models show promise in estimating snow water equivalent (SWE) over large mountainous areas at relatively high (<10 km) spatial resolution. These tools enable a reassessment of continental scale snow water storage (SWS). We assess the Weather Research and Forecasting (WRF) RCM SWS accuracy at the mountain range scale with a case study for the Sierra Nevada, USA. Since a spatially-continuous SWE truth does not exist, three datasets derived from, or validated against, in situ data were used to build a “reference” SWS dataset for three water years representing high, average, and low snow accumulation. WRF matched the reference peak SWS to within ±50% for all three years when run at either 3 km or 9 km spatial resolution, with 9 km simulations within ±30%. Moreover, WRF produces more reasonable SWS estimates than global/continental models, which were often 60-70% lower than the reference SWE. We then present a new WRF-based climatology of North American SWS. WRF was run over individual mountain ranges for representative years; mountain SWS was combined with lowland SWS from a global data product to produce a new climatology of North American SWS. We show that SWS peaks at 1684 km3, 55% greater than previous estimates. Though mountains comprise 25% of continental land area, we suggest that mountains hold 60% of the continent’s seasonal snow, as compared with previous estimates of 31%. Thus, the importance of snow in North American water budgets has been radically underestimated. ¬¬ We further explore the implications of increased SWS estimates in the water balance of five major North American river basins. We compare the new SWS climatology and associated cool-season precipitation estimates to three global data products. We find that observation-based precipitation datasets underestimate precipitation (compared with WRF) for the high latitudes and for mountainous watersheds. The reanalysis, on the other hand, is comparable to WRF. The reanalysis has far less SWS than WRF, however, despite having similar precipitation and snowfall. Thus, the reanalysis underestimates snow residence time on the landscape, possibly due to surface energy balance biases. In summary, we show that snow has been significantly underestimated in North American water budgets. Indeed, there is a surprising lack of consensus for existing estimates of large river basin water balances, including for cool-season precipitation. This is primarily due to challenges associated with mountainous terrain. Models and measurement methods must be adapted for montane regions if we are to quantify the state of the large-scale water cycle, and ultimately predict future hydrological changes in a warming world.
Michael Durand (Advisor)
Howat Ian (Committee Member)
Thompson Lonnie (Committee Member)
Mark Bryan (Committee Member)
Sivandran Gajan (Committee Member)
165 p.
Earth

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Citations

  • Wrzesien, M. L. (2018). Estimating North American montane snowpack with regional climate model simulations [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1522762079858684

    APA Style (7th edition)

  • Wrzesien, Melissa. Estimating North American montane snowpack with regional climate model simulations. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1522762079858684.

    MLA Style (8th edition)

  • Wrzesien, Melissa. "Estimating North American montane snowpack with regional climate model simulations." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1522762079858684

    Chicago Manual of Style (17th edition)

osu1522762079858684
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This open access ETD is published by The Ohio State University and OhioLINK.