Differences between morning and evening temperatures of cloud tops over tropical continents and oceans

Abstract Longwave radiation measurements made in the water vapour window by the satellite NOAA‐2 are examined for the period 15 June to 30 September 1974, in two oceanic and two continental tropical areas. Satellite overpasses are near 09 and 21 local time. It is found that convective cloud tops over land are much colder (and higher) in the evening than in the morning. The reverse is true over sea; further, the absolute frequency of very cold clouds is less there than over land. A specific cloud mass which could be followed for one week shows a morning‐evening variation in cloud top temperature in agreement with statistical deductions.