in meteorology, diurnal means daily, especially pertaining to actions which are completed in 24 hours and are repeated every 24 hours; this can be seen in the diurnal temperature variation. An alternative word for diurnal in this sense is diel.
in astronomy, diurnal motion refers to the apparent motion of stars around the Earth, caused by the Earth's rotation around its axis. More generally it means repeating daily as in e.g. diurnal effect
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Diurnal motion is an astronomical term referring to the apparent daily motion of stars in "orbit" around the Earth, caused by the Earth's rotation around its axis.
Diurnal motion can be seen in time-exposure photography [1].
Conversely, following the diurnal motion with the camera, to eliminate it on the photograph, can best be done with an equatorial mount, which requires adjusting the right ascension only; a telescope may have a motor to do that automatically (sidereal drive).
With regard to latitude, the diurnal cycle has an amplitude around 1.16 hPa at the equator, and elsewhere it is proportional to the cube of the cosine of the latitude angle.
Numerical models and surface observations show that deep convection in the Amazon basin acts like a pump (4, 5), lifting the air and heating it (due to latent heat release by condensation) in the afternoon, and sinking and cooling it (by radiative flux divergence mainly in the lower troposphere) around dawn.
This is quite obvious along coastlines in warm climates, where the daytime heating of the PBL over land (but not over the ocean) produces a lower sea level pressure inland, and hence a pressure gradient which drives the sea breeze.
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