The authors performed the field measurements in the microclimate around the building that has the large stepped roof garden for three times. In this paper, the results of the last long time measurements are mainly presented, the aim of which is to grasp the occurrences of down stream along by the green slope due to the gravity flow at nighttime. From these measurements, following results are obtained. 1. In the calm night, the intermittent down stream with small turbulence was observed at the bottom of green slope. The duration of the down stream is about twenty to eighty minutes. 2. The maximum wind speed of down stream at the bottom of green slope is about 0.5 meter per second and the maximum difference of air temperature between the top and bottom of green slope is about 1 degree. 3. The frequency of the occurrences of down stream was clarified under the twenty conditions, which are classified by the wind direction, wind velocity and net radiation at the rooftop.
