Tropical mesopause climatology over the Arecibo Observatory

We report on the first annual cycle of mesopause‐region (82–105 km) temperature profiles at a tropical latitude site, the Arecibo Observatory (18.35°N, 66.75°W), measured by potassium resonance lidar. Based on 74 night‐time temperature profiles of observing periods greater than 5 hours we observe a mean temperature profile with a mesopause altitude of 98 km and temperature of 193 K. The annual mean nighttime temperature profile is similar to that seen at mid‐latitudes, but there are striking differences in seasonal structure. The mesopause region mean seasonal structure at Arecibo experiences a temperature minimum of 176 K at 100 km during mid‐summer. The winter period minimum of about 190 K is found mostly in a broad flat distribution between 90 and 95 km, and less frequently near 100 km.