Fig. 7From: First imaging and identification of a noctilucent cloud from multiple sites in Hokkaido (43.2–44.4°N), JapanAveraged meridional wind at an altitude of 84 km observed by Wakkanai middle-frequency (MF) radar with intervals of 4 km and 30 min for altitude and time, respectively. The red solid line shows the result of nonlinear fitting with harmonic functions (period = 24, 12, 8 h). The time of the NLC event in universal time is indicated by the dashed line Back to article page