Measured Influence of the Nocturnal Urban Heat Island on Pollutant Transport


Roland R. Draxler


5th Symposium on Applications of Air Pollution Meteorology, American Meteorological Society


Summary - Extensive meteorological measurements over Washington, D.C. at night have shown that the airflow turns anti-cyclonically (clockwise) as the air passes over the urban area.  Vertical temperature profiles downtown and in the adjacent suburban area indicate that the magnitude of the turning, on the order of 10 to 25 deg was related to both the vertical extent and magnitude of the urban heat island. These results were anticipated by previous modeling studies.  However, the modeling study used only surface based measurements as a boundary condition to represent the urban heat island. The results from the METREX intensive experiments have shown that surface based measurements may not present a realistic picture of the urban environment and the depth to which the urban are alters the rural temperature profile can be more important that the urban-rural surface temperature difference.



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