Top co-authors See all
22 shared publications
Michelle Simões Reboita
21 shared publications
Universidade Federal de Itajubá, UNIFEI
Rita Yuri Ynoue
6 shared publications
University of São Paulo, DCA/IAG/USP
Lívia Márcia Mosso Dutra
5 shared publications
University of São Paulo
3 shared publications
UNESP, Bauru, Brasil
Distribution of Articles published per year
(2004 - 2014)
(2004 - 2014)
Total number of journals
Publications See all
Article 0 Reads 3 Citations Trend and teleconnection patterns in the climatology of extratropical cyclones over the Southern Hemisphere Published: 24 December 2014
Climate Dynamics, doi: 10.1007/s00382-014-2447-3
This study investigated the annual and seasonal trend of the extratropical cyclones occurrence, from 1980 to 2012, considering the whole Southern Hemisphere (SH). The influence of El Niño-Southern Oscillation (ENSO), Southern Annular Mode (SAM) and Indian Ocean Dipole (IOD) in the cyclones track density during the austral spring was also evaluated. Mean sea level pressure from National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis was used in an automatic scheme for cyclones tracking. The influence of the teleconnection patterns in the cyclones location is assessed through two methodologies: composite analysis and partial correlation technique. For whole SH and considering the total of cyclones and the stronger ones (with central pressure lower than 980 hPa in some period of their lifecycle) there is a statistically significant positive trend, while for weak cyclones the negative trend is not statistically significant. These patterns of trend occur along the year except in the spring. Regionally, the trend signal (positive or negative) of the cyclones occurrence varies spatially in each austral ocean. We suggested that the positive trend of the cyclones in high latitudes of the South Atlantic and South Pacific Oceans would be associated with the last decades global warming. The number of cyclones in the different phases of the ENSO, SAM and IOD is similar to that of neutral periods. However, these teleconnection patterns are important to modify the preferential regions of cyclones occurrence. The composite analysis of the cyclones track density during ENSO and SAM events is similar to that obtained in the partial correlation; but it is not true for IOD. Isolating ENSO and SAM effects in the cyclones track density, it is observed that the IOD positive phase contributes to the decrease in the cyclones density in large part of SH, particularly over the Indian and western South Pacific Oceans.
Article 0 Reads 0 Citations Statistical detection of spurious variations in daily raingauge data caused by changes in observation practices, as appl... Published: 15 October 2014
International Journal of Climatology, doi: 10.1002/joc.4183
In the instrumental records of daily precipitation, we often encounter one or more periods in which values below some threshold were not registered. Such periods, besides lacking small values, also have a large number of dry days. Their cumulative distribution function is shifted to the right in relation to that for other portions of the record having more reliable observations. Such problems are examined in this work, based mostly on the two‐sample Kolmogorov–Smirnov (KS) test, where the portion of the series with more number of dry days is compared with the portion with less number of dry days. Another relatively common problem in daily rainfall data is the prevalence of integers either throughout the period of record or in some part of it, likely resulting from truncation during data compilation prior to archiving or by coarse rounding of daily readings by observers. This problem is identified by simple calculation of the proportion of integers in the series, taking the expected proportion as 10%. The above two procedures were applied to the daily rainfall data sets from the European Climate Assessment (ECA), Southeast Asian Climate Assessment (SACA), and Brazilian Water Resources Agency (BRA). Taking the statistic D of the KS test >0.15 and the corresponding p‐value <0.001 as the condition to classify a given series as suspicious, the proportions of the ECA, SACA, and BRA series falling into this category are, respectively, 34.5%, 54.3%, and 62.5%. With relation to coarse rounding problem, the proportions of series exceeding twice the 10% reference level are 3%, 60%, and 43% for the ECA, SACA, and BRA data sets, respectively. A simple way to visualize the two problems addressed here is by plotting the time series of daily rainfall for a limited range, for instance, 0–10 mm day−1.
Article 0 Reads 0 Citations Observed summer weather regimes and associated extreme precipitation over Distrito Federal, west-central Brazil Published: 27 August 2014
Environmental Earth Sciences, doi: 10.1007/s12665-014-3607-9
The spatial and temporal variabilities of summer precipitation in west-central Brazil result in water supply variability and impact on water resources, agriculture and urban infrastructure. The diagnostic study of the variability of summer rainfall is accomplished through the relationship between the global atmospheric circulation and extreme precipitation over the Distrito Federal applying the technique of neural networks, the self-organizing (Kohonen) map and hierarchical ascendant classification. Nine weather regimes were identified (WRs), one group with four wet WRs with extreme precipitation, representing spatial variability of the active phase of South American Monsoon System (SAMS). One WR with the convergence zone in the central position of the country, two WRs positioned farther north suggesting be influenced by Madden–Julian Oscillation, and another WR further south may be influenced by Rossby waves. Five other dry WRs were associated with the break phases of the SAMS, or transitional regimes, without the formation of the convergence zone, but with an active low-level jet. In this group, less extreme precipitation events occurred in the central part of the country. The WRs relating large-scale atmospheric circulation and local precipitation enable better understanding of the intraseasonal variability in the regional scale.
Article 0 Reads 0 Citations Analysis of RegCM3 generated weather regimes over central Brazil: a case study in Distrito Federal Published: 31 May 2014
Environmental Earth Sciences, doi: 10.1007/s12665-014-3340-4
Low level atmospheric circulations downscaled by regional climate model are used to identify austral summer (December–January–February) weather regimes (WRs) over central Brazil. For the period 1989–2006, the Kohonen’s self-organizing maps method is applied to provide simulated weather patterns and their relationship with daily rainfall. Six WRs were defined: two related to the active phase of the South American monsoon system (SAMS), with the large occurrence of days with extreme rainfall; two related to the break phase and few occurrences of extreme rainfall; and two others resembling transient WRs, those with fewer extreme rainfall. The WRs formed a cycle obtained from their transition probabilities, which suggests alternating phases of the convergence zone and their association with extreme rainfall. Thus, the variability of summer precipitation, related to the behavior of the simulated WRs enables the verification of the regional dynamic model on intraseasonal time scale.
Article 0 Reads 9 Citations Interannual variability associated with ENSO: present and future climate projections of RegCM4 for South America-CORDEX ... Published: 06 May 2014
Climatic Change, doi: 10.1007/s10584-014-1119-y
Interannual variability over South America (SA) is mainly controlled by the El Niño-Southern Oscillation (ENSO) phenomenon. This study investigates the ENSO precipitation signal during austral spring (September–October–November-SON) over SA. Three global circulation models-GCMs-(MPI, GFDL and HadGEM2) are used for RegCM4 (Regional Climate Model version 4) downscaling of the present (1975–2005) near-future (2020–2050) and far-future (2070–2098) climates using two greenhouse gas stabilization scenarios (RCP4.5 and RCP8.5). For the present climate, only HadGEM2 simulates a frequency of El Niño (EN) and La Niña (LN) years similar to the observations. In terms of ENSO frequency changes, only in the far-future RCP8.5 climate there is greater agreement among GCMs, indicating an increase (decrease) of EN (LN) years. In the present climate, validation indicates that only the RegCM4 ensemble mean provides acceptable precipitation biases (smaller than ±20 %) in the two investigated regions. In this period, the GCMs and RegCM4 agree on the relationship between ENSO and precipitation in SA, i.e., both are able to capture the observed regions of positive/negative rainfall anomalies during EN years, with RegCM4 improving on the GCMs’ signal over southeastern SA. For the near and far future climates, in general, the projections indicate an increase (decrease) of precipitation over southeastern SA (northern-northeastern SA). However, the relationship between ENSO and rainfall in most of RegCM4 and GCM members is weaker in the near and far future climates than in the present day climate. This is likely connected with the GCMs’ projection of the more intense ENSO signal displaced to the central basin of Pacific Ocean in the far future compared to present climate.
Article 0 Reads 6 Citations Air–Sea Interaction Processes Influencing the Development of A Shapiro–Keyser Type Cyclone over the Subtropical South At... Published: 15 September 2012
Pure and Applied Geophysics, doi: 10.1007/s00024-012-0584-3
This study analyzes the impacts of latent and sensible heat exchanges between the atmosphere and the ocean in a non-explosive Shapiro–Keyser type cyclogenesis event that occurred over the southwestern South Atlantic Ocean. The synoptic evolution shows a relatively strong warm front and a cold frontal fracture during the system’s development and a warm seclusion in its mature stage, characterizing a Shapiro–Keyser type cyclone. Numerical experiments with the ARW-WRF Model version 3.3 were used to investigate the influences of sensible and latent fluxes on the track of the surface low, intensity of the fronts and coupling of the lower and upper troposphere. The simulations indicate that in the presence of these fluxes the cyclone underwent greater intensification, had a longer life time and longer trajectory, and presented a typical southeastward movement. In the absence of these fluxes, the cyclone developed a weaker warm front with consequent reduction of diabatic heating due to grid scale precipitation along it. This reduced the negative pressure tendency southeast of the cyclone center and the surface cyclone moved northeastward, showing a decoupling of the lower- and upper-level waves. A consequence of this anomalous tracking is the location of the surface cyclone beneath the upper-level trough axis, where there is no upper-level divergence associated with cyclonic vorticity advection contributing to the further system intensification. Numerical experiments suggest that for this Shapiro–Keyser type cyclone the air–sea interaction processes are crucial to obtain a cyclone with features similar to the observations.