  Rainfall in coastal areas of the tropics is often shaped by the presence of
circulations directly associated with the topography, such as land-sea and/or
mountain-valley breezes. In many regions the coastally-affected rainfall
consitutes more than half of the overall rainfall received. Weather and climate
models with parametrized convection produce large errors in rainfall in
tropical coastal regions, most commonly underestimating rainfall over land and
overestimating it over the ocean. Building on an algorithm to objectively
identify rainfall that is associated with land-sea interaction we investigate
whether the relationship between rainfall in coastal regions and the
large-scale atmosphere differs from that over the open ocean or over inland
areas. We combine 3-hourly satellite estimates of rainfall with estimates of
the large-scale atmospheric state from reanalyses. We find that when grouped by
rainfall intensity, medium-intensity coastal rainfall in the tropics occurs in
more stable conditions and drier atmospheres and is associated with less
large-scale convergence than its open-ocean and inland counterparts. Overall,
the dependence of the amount of rainfall on the large-scale state is
significantly weaker when the rainfall is coastally influenced. Our findings
indicate that the representation of convection in weather and climate models
must cater for the special character of the large-to-small scale relationship
near coasts rather than rely on a common set of rules across the globe.
