Climatological Behavior of Precipitating Clouds in the Northeast Region of Brazil

Abstract

This study aims to analyze the climatological classification of precipitating clouds in the Northeast of Brazil using the radar on board the Tropical Rainfall Measuring Mission (TRMM) satellite. Thus, for this research a time series of 15 years of satellite data (period 1998-2012) was analyzed in order to identify what types of clouds produce precipitation estimated by Precipitation Radar (PR) and how often these clouds occur. From the results of this work it was possible to estimate the average relative frequency of each type of cloud present in weather systems that influence the Northeast of Brazil. In general, the stratiform clouds and shallow convective clouds are the most frequent in this region, but the associated rainfall is not as abundant as precipitation caused by deep convective clouds. It is also seen that a strong signal of shallow convective clouds modulates rainfall over the coastal areas of Northeast of Brazil and adjacent ocean. In this scenario, the main objective of this study is to contribute to a better understanding of the patterns of cloud types associated with precipitation and building a climatological analysis from the classification of clouds.

Spatial distribution of the level of return of extreme precipitation events in Northeast Brazil

“…While JJA corresponds to the dry period in most of NEB (Rao et al, 1993), it corresponds to the rainy season in the NEB east coast region (Oliveira et al, 2013(Oliveira et al, , 2017. According to Palharini and Vila (2017), this is strongly influenced by shallow convection.…”

Sub-hourly rainfall patterns by hyetograph type under distinct climate conditions in Northeast of Brazil: a comparative inference of their key properties

“…This is in accordance with Back (2011), which showed that in Brazil the rainfall events tend to concentrate their rainfall depths mainly in the first and second quartiles. The presence of R-events after the reclassification in GEB typifies the slight and uniform rainfall event commonly found in shallow convective clouds, which occur more frequently over the ocean and coastal areas from March to August in tropical Northeast region of Brazil (BRINGI et al, 2003;DILMI et al, 2016;PALHARINI;VILA, 2017;TEIXEIRA, 2008).…”

“…Intriguingly, the CEB and GEB featured similar hyetograph classification, even though they belonged to distinct climates and biomes. From Palharini and Vila (2017), this may likely be explained because the CEB is located in the eastern semi-arid region susceptible to some influence of the moisture transport from the Atlantic Ocean towards the Continent, which may affect the rainfall temporal distribution near to the transition Sub-hourly rainfall patterns by hyetograph type under distinct climate conditions in Northeast of Brazil: a comparative inference of their key properties zone between tropical wet and semi-arid climates (see Figure 1 and Table 1). The SL-events rainfall depths decreased to 2%, 9% and 2% after the reclassification in AEB, CEB and GEB, a reduction of 86%, 75% and 90% in rainfall depth, respectively.…”

“…The mean rainfall rates of all unimodal hyetographs ranged from ~10 to ~25 mm h -1 , slightly higher than the B-events, from 5 to ~14 mm h -1 ; the latter, however, showed a significant difference in AEB (p < 0.0001), before and after the reclassification. The deep convective and stratiform clouds may explain the higher data dispersion in AEB and CEB, for they lead to a great concentration of intense events, from December to April in AEB, and from November to February in CEB (CAMARASA-BELMONTE; SORIANO, 2014;PALHARINI;VILA, 2017;ZHANG et al, 2016).…”

“…The rainfall durations were not longer than 12 h due to the rigorous MIT criterion (equals to 30 min) used in this study, which eventually separated some near rainfall events (DUNKERLEY, 2010) (Figure 7c and d). The longest rainfall event was detected in GEB due to the shallow convective clouds observed in the extreme coastal zones of the tropical Northeast of Brazil (BRINGI et al, 2003;DILMI et al, 2016;PALHARINI;VILA, 2017;TEIXEIRA, 2008). The highest mean durations among hyetograph types were featured by the SL-events, varying from ~1.9 h (in GEB) to ~3.1 h (in AEB), which turned out to be reclassified, leading to a shrinking on the significant differences, only found in B-events (p < 0.0001).…”