An irrigated grassed park set in generally drier urban surroundings is subject to advection at several scales. In particular it experiences microscale "edge" effects at its periphery and local scale "oasis" effects over the whole park. We present the results of measurements of the surface energy balance and related climatic variables for an irrigated park in a residential suburb of Sacramento, CA during summer. The energy balance measurements are taken from a transect of three sites (each with radiometers, lysimeters and soil heat flux plates) across the park, aligned parallel to the mean wind direction. Evaporation rates show an approximately exponential decline across the park due to edge effects. Moreover, this spatial pattern is superimposed on a base of absolutely high evaporation rates forced by oasis influences due to the park being in relatively drier urban environs. This is demonstrated by the fact that the park rates exceed even those of an irrigated rural site (a sod farm) outside the city. Comparison of surface temperatures between the park and nearby urban materials suggests that the park behaves like a "giant leaf" and contributes a thermostatting effect to the thermal climate.