THERMAL AND DYNAMIC CHARACTERISTICS OF ALPINE LAKE BREEZES, LAKE-TEKAPO, NEW-ZEALAND

Thermodynamic characteristics and temporal variation of alpine lake br eezes in the eastern Southern Alps are examined. Research was conducte d in a large glacially excavated basin dominated by an 87 square kilom etre melt-water lake as part of a study of windblown dust dispersion. The surrounding mountain ranges were found to shelter the lake basin f rom most synoptic winds, thereby allowing local and regional thermally generated circulations to develop to ridge height, approximately 1300 m above the surrounding landscape. During favourable synoptic conditi ons the local lake breeze becomes embedded within the regional valley wind forming an extended lake breeze. Tethersonde flights during these conditions made using a kite based sounding system identified both st able internal (SIBL) and thermal internal boundary layer (TIBL) condit ions over the down wind shoreline. Two equations for estimating the he ight of both boundary-layer types were tested against observations and found to provide good first order predictive estimates of boundary-la yer height.