@InProceedings{LucioMoliAbre:2006:BrMaCi,
author = "Lucio, Paulo S{\'e}rgio and Molion, Luiz Carlos B. and de Abreu,
Magda Luzimar",
affiliation = "{Centre of Geophysics of {\'E}vora (CGE) - Portugal} and
{Universidade Federal de Alagoas (UFAL) - Brazil} and
{Universidade Federal de Minas Gerais (UFMG) - Brazil}",
title = "Changes in occurrences of meteorological extreme events. Case
Study: Brazilian main cities",
booktitle = "Proceedings...",
year = "2006",
editor = "Vera, Carolina and Nobre, Carlos",
pages = "1539--1544",
organization = "International Conference on Southern Hemisphere Meteorology and
Oceanography, 8. (ICSHMO).",
publisher = "American Meteorological Society (AMS)",
address = "45 Beacon Hill Road, Boston, MA, USA",
keywords = "air-temperature, Generalised Pareto Distribution, rainfall,
seasonal trend, threshold exceedance.",
abstract = "Extreme weather and climate events have received increased
attention in the last few years, due to the often-large loss of
human life and exponentially increasing costs associated with
them. Short-duration episodes of extreme heat or cold waves are
often responsible for major impacts on society. Conversely, the
location, timing, and magnitude of local and regional changes
remain unknown because of uncertainties on future changes in the
frequency and intensity of meteorological systems that cause
extreme weather and climate events. It is likely that
anthropogenic forcing will eventually cause global increases in
extreme precipitation, primarily because of probable increases in
atmospheric water vapour content and destabilization of the
atmosphere. Relatively little work has been accomplished relating
changes in high frequency extreme temperature events such as heat
waves, cold waves, and number of days exceeding temperature
thresholds. In this research, we explicitly model the tail regions
of air-surface temperature, using the recent developments of
extreme value theory, estimating the tails by fitting a
Generalised Pareto Distribution (GPD) to the observations lying
beyond certain thresholds that mark the beginning of the tail
regions. There are different approaches to characterise the
spatial behaviour of climatological phenomenon, and a particular
elegant formulation is derived from the theory of point process
governing peaks-over-threshold. Analysis of (1) trends in the
number of warm days in Brazil and changes in the aestival season
(spring throughout summer) length are investigated; (2)
significant trends to fewer extreme minimum cold days and also
trends to fewer warm maximum temperatures as well are analysed.
The aim of this study is to verify whether extreme values related
to weather attributes from several regions of Brazil (regional
scale) show structural change, which can reflect the intended
global change during the last century. For this purpose, daily
extremes of air-surface temperatures and precipitation as well as
the clustering of extreme temperatures defined by the
peaks-overthreshold (POT) methodology are strongly indicated. The
analysis of meteorological extreme events indicates that there has
been a sizable change in their frequency in Brazil (urban
behaviour). This suggests that natural variability of the climate
system could be the cause of the recent changes, although
anthropogenic forcing due to increasing greenhouse gases
concentration cannot be disregarded. Like the exponential
distribution, the GPD is often used to model the tails of another
distribution. However, while the normal distribution might be a
good model near its mode, it might not be a good fit to real data
in the tails and a more complex model might be needed to describe
the full range of the data. The GPD allows a continuous range of
possible shapes that includes both the exponential and Pareto
distributions as special cases. The empirical distributions
focused in this study lead to a negative shape parameter, whose
tails are finite. The number of warm nights is increasing on
spring, summer and autumn! The number of warm days is increasing
on summer! Almost certainly the summer nights are contaminating
the spring nights and the autumn nights (maybe due to the urban
heat island effect)! The longterm trend detected for TMIN and TMAX
in some Brazilian regions indicate that the magnitude of the air
temperature for the winter, spring and autumn are increasing.
Probably the summer is invading or contaminating spring and spring
is invading or contaminating winter in Brazil.",
conference-location = "Foz do Igua{\c{c}}u",
conference-year = "24-28 Apr. 2006",
language = "en",
organisation = "American Meteorological Society (AMS)",
ibi = "cptec.inpe.br/adm_conf/2005/10.29.12.13",
url = "http://urlib.net/ibi/cptec.inpe.br/adm_conf/2005/10.29.12.13",
targetfile = "1539-1544.pdf",
type = "Understanding long-term climate variations in the SH",
urlaccessdate = "11 maio 2024"
}