We show that in the tropics, tropical atmospheric dynamics force the
subcloud moist static energy (MSE) over land and ocean to be very
similar in, and only in, regions of deep convection. Using observed
rainfall as a proxy for convection and reanalysis data to calculate MSE,
we show that subcloud MSE in the non-convective regions may differ
substantially between land and ocean but is uniform across latitudes in
convective regions even on a daily timescale. This result holds also in
CMIP5 model simulations of past cold and future warm climates.
Furthermore, the distribution of rainfall amount in subcloud MSE is very
similar over land and ocean with the peak at 343 J/g and a half width at
half maximum of 3 J/g. As a result, the annual-maximum subcloud MSE at
each location over land and ocean is subject to a common upper bound set
by the convective regions.