Using a sophisticated version of weather radar imaging, scientists
have now been able to track the movement of rainstorms and even to measure
the amount of rainfall released, and from which altitudes. At the AGU
meeting members of the Tropical Rainfall Measuring Mission (TRIM) reported
the most precise rain maps ever achieved for the region within 38 degrees
latitude north and south of the equator, a zone crucial to worldwide
weather because of its vast ocean currents, rain forests, and the huge
amount of solar radiation falling there.
Daniel Rosenfeld
of the Hebrew University of Jerusalem said that when air over the Amazon
rainforest was clean, storms there unexpectedly rivaled those over the
ocean in the amount of rainfall. In other words, Brazil was acting more
like a "green ocean" than like a continental land mass. Rosenfeld explained
that although some particulate matter is useful for seeding raindrops,
when too many fine particles are present (from wood fires, say) then
water droplets are actually inhibited from forming into drops large
enough to precipitate. Brazil then, at least during a period of very
clear air, could approximate the conditions over the ocean (TRIM
website ).
