Development and Verification of Daily Gridded Climate Surfaces in the Okanagan Basin of British Columbia

Gridded estimates of daily minimum and maximum temperature and precipitation from 1960 to 2005 were prepared for the Okanagan Basin of British Columbia. The procedure utilized available daily climate data from 182 stations and employed a regression based interpolation scheme at 500 metre grid spacing. Spatial distribution of temperature took into account variations in temperature with elevation, an observed north-south temperature gradient, and proximity to several large lakes in the valley bottom. An inverse distance weighting scheme was used for the interpolation, and a constrained lapse rate approach was used to interpolate in areas that lie above the highest climate station. Temperature inversions were handled by fitting a second order polynomial and introducing a two-layer model. The precipitation routine differs from the temperature model in that the regressions were based on monthly precipitation totals, thus producing daily precipitation surfaces that incorporate an orographic component along with...