global overview

A World perspective on daytime cloudiness

Mean climatological features

We have used available 5 km pixel imagery from the two daytime MODIS satellite observations to develop cloud climatologies at 1030 and 1330 local time.  These are shown in Fig 1a-b.

Averaging the two times together gives a good perspective of the cloudiness around mid-day (Fig 1c).  There are many interesting aspects shown in these averages.

ITCZ, subtropical highs, continentality, ice features

Seasonality of cloudiness

One can divide the annual mean into 6-monthly means, reflecting the boreal summer (May-Oct) and boreal winter (Nov-Apr) period.  These averages (Fig 2) composed of months that are displaced with respect to the shortest and longest days to reflect the seasonal lag of the ocean temperatures – which are about 2 months lagged with respect to the solar heating maximum (June 21 approx) and minimum (Dec 21 approx).

The semiannual climatologies are simplifications to be sure – one can produce monthly climatologies (Wilson and Jetz 2016) that can provide more insight into local climatologies.  But as a first pass, the semiannual climatologies can help one understand the importance of seasonality in different parts of the world.