10:15 AM - 10:30 AM
[AAS13-06] Nocturnal Temperature Distribution under Fine and Weak Wind Conditions Based on Spatially High Density Observation Data in the Tokyo Metropolitan Area: Features in Winter
Keywords:urban heat island, nocturnal temperature distribution, spatially high density observation, Tokyo wards area, winter
In winter (from November to February), the high temperatures in the metropolitan area were concentrated throughout the night near the southern area of Chuo ward. In particular, it is noted that several zones of steep horizontal temperature gradients (HTGZ) were detected in the metropolitan-ward area. The HTGZs appeared during the period several hours before and after sunset, and gradually became more noticeable near sunrise. The distribution of temperature-decrease rate around sunset also showed steep horizontal gradient zones, which corresponded to the HTGZs between the inner city and outer area. After midnight, though wind speed decreased in the suburban inland region corresponding to the development of a near surface stable layer, that observed inner area of HTGZs remained comparatively large. This is likely due to the less stable atmospheric condition in central Tokyo with its high temperatures and/or large surface roughness. It is possible that this wind prevents the development of a stable layer, thus maintaining high temperatures downwind from the central Tokyo.
Summertime (July and August) features will be presented separately.