The distinction between canopy and boundary‐layer urban heat islands

Air temperature measurements from car traverses in and near Vancouver, B.C. are used to test two urban heat island models: one an empirical model, the other a theoretical advective model. The empirical model describes the Vancouver observations well, whereas the advective one performs rather poorly. This discrepancy may be attributed to a failure to distinguish between meteorological conditions in the urban canopy, and those in the overlying urban boundary layer. This leads to a reassessment of the explanation of the relationship between city size (as measured by population) and the heat island intensity (as measured in the urban canopy).