TITLE:
Convective Rainfall in Amazonia and Adjacent Tropics
AUTHORS:
Augusto J. Pereira Filho, Richard E. Carbone, John D. Tuttle, Hugo A. Karam
KEYWORDS:
Satellite-Derived Rainfall, Organized Convection, La Plata Basin, Amazon Basin, Diurnal Cycle
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.5 No.2,
April
30,
2015
ABSTRACT: Hourly rainfall estimates from integrated satellite data are used to build
a dynamically based climatology of convectively generated rainfall across South
America, including tropical, sub-tropical and oceanic regions. Herein, we focus
on 0S to 15S, including greater Amazon and NE Brazil leeward of the South Atlantic
Ocean. Emphasis is placed on rainfall resulting from organized convective regimes,
which are known to produce the majority of seasonal rainfall in various parts of
South America and other continents. The statistical characteristics of individual
events are quantified and examined with respect to regional atmospheric conditions.
Among the factors considered are steering winds and wind shear, convective available
potential energy (CAPE), sea and land breezes, and the occurrence of transient disturbances
such as Kelvin Waves and Easterly Waves. Forcing and convective triggering mechanisms
are inferred from the diagnosis of systematic patterns as evidenced in the continental
diurnal cycle and longer periods of natural variability. The episodes of organized
convection are analyzed in terms of their duration, span, phase speed, starting
and ending time, starting and ending longitude, month and year through frequency
distribution analysis. Most episodes of organized convection tend to move westward
across the Amazon Basin. Descriptive statistics indicate average phase speed of
westward and eastward episodes of convection in the Amazon basin at -11.8 m.s-1 and 13.0 m.s-1, respectively. Eastward propagating systems are influenced
by northeastward moving cold fronts in Southern South America and tend to trigger
and to organize convection across the Amazon Basin. Hourly rainfall analyses indicate
that convection over the Amazon region is often organized.