Results from Tokyo simulations using the ensemble system indicate a positive spread-skill relationship, with the addition of urban perturbations enabling the ensemble variance to distinguish a larger range of forecast error variances. For a pre-frontal period (stronger synoptic flow), there is less variability among ensemble members in the strength of the urban heat island and its interaction with the sea breeze front. During the post-frontal time period the sea breeze frontal position is very sensitive to the details of the urban representation, with large horizontal frontal variability relative to the width of the urban center, and displaying significant impacts on the development and strength of the heat island. Moreover, the dosage values of a tracer released at offshore and urban sites have considerable variability among ensemble members in response to small-scale features such as coastally upwelled water, enhanced anthropogenic heating, and variations in building heights. Realistic variations in SST produce subtle sea breeze alterations that dramatically impact tracer distributions.
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