1. Characteristic Daily Rainfall Patterns Detected in the Tropics
K. Kikuchi and B. Wang
(d) PCs of 3G68
mm / hour
: PC1
: PC2
(a) 3B42 EOF1 (62 %)
(b) 3B42 EOF2 (27 %)
×0.01
(c) Schematic summary of tropical daily rainfall patterns
: continental
: ocean
:off-shore coastal
:on-shore coastal
Local solar time (hour)
The daily rainfall cycle in the tropics has clear patterns that depend upon where the rain falls, according to this IPRC study. The conclusion is based on an analysis of two complementary satellite data sets from TRMM (3B42 and 3G68) for 1998 – The EOF analysis of the data shows that the first two modes account for almost 90% of the diurnal precipitation variance. Charting the typical rainfall propagation and peak times revealed three daily rainfall cycle regimes: (1) The oceanic regime with an early morning peak (06~09 LST); (2) the continental regime with an afternoon peak (15~18 LST); and (3) the coastal regime with strong propagation and peaks that depend on whether the movement is inland or off shore. The on-shore coastal regime peaks from noon to evening (12~21 LST); the off-shore coastal regime peaks from late evening to noon the next day (21~12 LST).
The threshold for the mean diurnal range, which measures diurnal cycle intensity, was 4.8 mm/day, and regions with a smaller range are thus in white in panel c.