Climatology of Lake-Effect Precipitation Events over Lake Tahoe and Pyramid Lake

Abstract

he frequency, timing, and environmental conditions of lake-effect (LE) precipitation over Lake Tahoe and Pyramid Lake in northern California and western Nevada were examined for the 14 winters (September?March) from 1996/97 through 2009/10. Weather Surveillance Radar-1988 Doppler (WSR-88D) data from Reno, Nevada (KRGX), were used to identify 62 LE events. LE precipitation occurred as single bands extending downwind from overlake areas, and as isolated regions of overlake precipitation with little or no extension over land. Mesoscale vortices were also identified during both Lake Tahoe and Pyramid Lake LE events. An average of 4.4 LE events occurred each winter in the Lake Tahoe and Pyramid Lake region, with events occurring most frequently in October. LE events had an average duration of 6.3 h, approximately half the duration of LE events observed over Lake Champlain, the New York State Finger Lakes, or the Great Salt Lake. The observed conditions during LE events in the Lake Tahoe and Pyramid Lake region typically had 1) mean surface air temperatures below freezing, 2) mean surface wind speeds of <2.0 m s?1 (notably weaker than during lake effect in other areas), 3) a mean lake?air temperature difference of 11.5°C, and 4) a mean lake?700-hPa temperature difference of 20.9°C.