Modeling Winter Precipitation Over the Juneau Icefield, Alaska, Using a Linear Model of Orographic Precipitation

Frontiers in Digital Humanities

Pelto, Mauri¹  Schuler, Thomas V.²  Bieniek, Peter A.³  Roth, Aurora⁴  Hock, Regine⁴  Aschwanden, Andy⁵ 

[1] Department of Arctic Geophysics, University Centre in Svalbard UNIS, Norway;Department of Earth Sciences, Uppsala University, Sweden;Department of Geosciences, University of Oslo, Norway;Geophysical Institute, University of Alaska Fairbanks, United States;International Arctic Research Center, University of Alaska Fairbanks, United States

关键词: orographic precipitation;    Glacier mass balance;    Snow accumulation;    modeling;    Juneau Icefield;    Alaska;    downscaling;   

DOI  :  10.3389/feart.2018.00020

学科分类：社会科学、人文和艺术（综合）

来源: Frontiers

【 摘 要 】

Assessing and modeling precipitation in mountainous areas remains a major challenge in glacier mass balance modeling. Observations are typically scarce and reanalysis data and similar climate products are too coarse to accurately capture orographic effects. Here we use the linear theory of orographic precipitation model (LT model) to downscale winter precipitation from a regional climate model over the Juneau Icefield, one of the largest ice masses in North America ($>$4000 km\textsuperscript{2}), for the period 1979--2013. The LT model is physically-based yet computationally efficient, combining airflow dynamics and simple cloud microphysics. The resulting 1 km resolution precipitation fields show substantially reduced precipitation on the northeastern portion of the icefield compared to the southwestern side, a pattern that is not well captured in the coarse resolution (20 km) WRF data. Net snow accumulation derived from the LT model precipitation agrees well with point observations across the icefield. To investigate the robustness of the LT model results, we perform a series of sensitivity experiments varying hydrometeor fall speeds, the horizontal resolution of the underlying grid, and the source of the meteorological forcing data. The resulting normalized spatial precipitation pattern is similar for all sensitivity experiments, but local precipitation amounts vary strongly, with greatest sensitivity to variations in snow fall speed. Results indicate that the LT model has great potential to provide improved spatial patterns of winter precipitation for glacier mass balance modeling purposes in complex terrain, but ground observations are necessary to constrain model parameters to match total amounts.

【 授权许可】

CC BY