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Howard P. Hanson
,
Claire S. Hanson
, and
Brenda H. Yoo

Analysis of ice observations made by cooperative observers from shoreline stations reveals significant changes in the ice season on the North American Great Lakes over the past 35 years. Although the dataset is highly inhomogeneous and year-to-year variability is also quite large, there is a statistically significant indication that the end of the ice season (as defined by the time at which ice departs from the observer stations in spring) has come increasingly early at a number of locations. The earlier ice departure is reflected in a somewhat earlier spring runoff through the St. Lawrence River over the same time period and correlates with increases in springtime temperatures at stations in the region. This example of a trend toward warmer, earlier springs in the upper Midwest is consistent with results from a number of other regional datasets. Because the ice observations began in the mid-1950s, other analyses, including comparisons with modern satellite datasets, could provide a useful tool for monitoring future climate change.

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V. E. Derr
,
R. S. Stone
,
H. P. Hanson
, and
L. S. Fedor

Abstract

Surface measurements of solar flux and total integrated liquid-water content, radiosonde data, and infrared satellite images are analyzed in conjunction with radiative transfer calculations to derive an empirical parameterization for the shortwave transmissivity of continental stratiform water clouds. The data were collected near Denver, Colorado, over a period of six years. Seventeen days on which uniform stratiform clouds persisted over the observing site were selected for detailed analysis, and form the basis for deriving the parameterization. A mulitiple reflection radiative transfer model is employed to estimate stratus cloud transmissivity in terms of the measurable liquid-water path (LWP). A nonlinear fit of estimated transmissivities to the corresponding observations of LWP yields close agreement with a previous, more complicated parameterization. The derived expression for cloud transmissivity is used to predict mean daily surface fluxes for 61 days during which periods of stratiform clouds were observed over the Denver area. A comparison between predicted and measured fluxes shows agreement to within ±4%, with best agreement for clouds of moderate optical thickness. Potential sources of error are identified with sensitivity studies.

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Power from the Florida Current

A New Perspective on an Old Vision

Howard P. Hanson
,
Susan H. Skemp
,
Gabriel M. Alsenas
, and
Camille E. Coley
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