The changes of value, for example, of a meteorological element within the course of a (solar) day. More especially, it denotes the systematic changes that occur during the average day.
This term is used to indicate the changes, in the course of an average day, in the magnitude of a meteorological element. The most striking example of this is the diurnal variation of barometric pressure in the tropics, the chief component of which has a 12-hourly period. The maxima of this variation are about 10 a. m. and 10 p.m., the minima about 4 a.m. and 4 p.m. local time.
A regular swing in mood, usually starting the day in deep depression but feeling less gloomy as the day progresses. This is one characteristic sign of DEPRESSION (qv).
fluctuations that occur during each day
daily variation in the Earth's magnetic field caused by solar radiation and lunar effects. back
When used in meteorology, this usually refers to the daily pattern of winds and temperatures.
The variance in temperature between day and night
This is the tendency for meteor rates from the sporadic background to be significantly higher late in the night than early in the night. It is due to the fact that before midnight an observer is looking in the direction from which the Earth is travelling (and so some meteors are being left behind) whereas after midnight the observer is on the side of the Earth facing the direction of travel (and the Earth is 93catching up94 with some meteors).
Changes which occur during the day such as the rise and fall of temperature or the regular variations of pressure.