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Advances in Meteorology
Volume 2015 (2015), Article ID 176238, 20 pages
http://dx.doi.org/10.1155/2015/176238
Research Article

Easterly Wave Disturbances over Northeast Brazil: An Observational Analysis

1Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo, 05508-090 São Paulo, SP, Brazil
2CPTEC-INPE, 12630-000 Cachoeira Paulista, SP, Brazil
3NERC Centre for Earth Observation, University of Reading, Reading RG6 6BB, UK
4Capixaba Institute of Research, Technical Assistance and Rural Extension, 29052-010 Vitoria, ES, Brazil

Received 19 January 2015; Revised 8 May 2015; Accepted 11 May 2015

Academic Editor: Luis Gimeno

Copyright © 2015 Helber Barros Gomes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper aims to identify the circulation associated with Easterly Wave Disturbances (EWDs) that propagate toward the Eastern Northeast Brazil (ENEB) and their impact on the rainfall over ENEB during 2006 and 2007 rainy seasons (April–July). The EWDs identification and trajectory are analyzed using an automatic tracking technique (TracKH). The EWDs circulation patterns and their main features were obtained using the composite technique. To evaluate the TracKH efficiency, a validation was done by comparing the EWDs number tracked against observed cases obtained from an observational analysis. The mean characteristics of EWDs are 5.5-day period, propagation speed of ~9.5 m·s−1, and a 4500 km wavelength. A synoptic analysis shows that between days −2 d and 0 d, the low level winds presented cyclonic relative vorticity and convergence anomalies both in 2006 and 2007. The EWDs signals are strongest at low levels. The EWDs propagation is associated with relative humidity and precipitation positive anomalies and OLR and omega negative anomalies. The EWDs tracks are seen over all ENEB and their lysis occurs between the ENEB and marginally inside the continent. The tracking captured 71% of EWDs in all periods, indicating that an objective analysis is a promising method for EWDs detection.