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Lake-Atmosphere Interactions in Great Lakes Basin

Collaborators: Val Bennington, Katie Holman, David Lorenz, Azar Zarrin, Elody Fluck, Steve Vavrus, Drew Gronewold

Funding: UW-Madison CPEP, NOAA GLERL

Publications:

Bennington, V., M. Notaro, and K.D. Holman, 2014: Improving climate sensitivity of deep lakes within a regional
climate model and its impact on simulated climate. Journal of Climate, doi:http://dx.doi.org/10.1175JCLI-D-13-
001101.1

Holman, K.D., D.J. Lorenz, and M. Notaro, 2014: Influence of the background state on Rossby wave propagation
into the Great Lakes region based on observations and model simulations. Journal of Climate, in review.

Notaro, M., K. Holman, A. Zarrin, E. Fluck, S. Vavrus, and V. Bennington, 2013: Influence of the Laurentian Great
Lakes on regional climate. Journal of Climate, 26, 789-804.

Holman, K.D., A. Gronewold, M. Notaro, and A. Zarrin, 2012: Improving historical precipitation estimates over the
Lake Superior basin. Geophysical Research Letters, 39, L03405, doi:10.1029/2011GL050468.

Methods: The influence of the Laurentian Great Lakes on climate is assessed by comparing two decade-long simulations, with the lakes either included or excluded, using the ICTP RegCM4 regional climate model.

Key finding: The Great Lakes dampen the variability in near-surface air temperature across the surrounding region while reducing the amplitude of the diurnal cycle and annual cycle of air temperature. Changes in the hydrologic budget due to the presence of the Great Lakes include increases in evaporation and precipitation during October–March and decreases during May–August, along with springtime reductions in snowmelt-related runoff. Circulation responses consist of a regionwide decrease in sea level pressure in autumn–winter and an increase in summer, with enhanced ascent and descent in the two seasons, respectively. The most pronounced simulated impact of the Great Lakes on synoptic systems traversing the basin is a weakening of cold-season anticyclones.

Seasonal mean differences (LAKE-NOLAKE) during 1980-1989 in (a-d) sea-level pressure (hPa), (e-h) 10-m u-wind component (m/s), (i-l) 10-m v-wind component (m/s), and (m-p) 2-m water vapor mixing ratio (g/kg) (Notaro et al. 2013). The upper and lower color bars apply to (a-d) and (e-p), respectively. Simulations LAKE and NOLAKE are produced using ICTP RegCM4 regional climate model, with the Great Lakes either present or absent, respectively.