The Northeast Brazil (NEB) is known for its temporal and spatial variability of precipitation. Several studies have investigated this variability in order to understand the damaging episodes such as droughts and flood...The Northeast Brazil (NEB) is known for its temporal and spatial variability of precipitation. Several studies have investigated this variability in order to understand the damaging episodes such as droughts and floods. The phenomenon of drought in the NEB is a complex topic due to affecting?millions of people and being?the object of study in several fields of knowledge. One way to try to argue about this phenomenon is through the concept of vulnerability. The “operability” of this broad concept in natural disasters is a complex task. In order to measure an indicator of vulnerability it is necessary large amount of data from different areas of knowledge, among which?include: meteorology, socio-environmental, economic, public health, among other areas. The main objective of this study is to create an index of vulnerability to climate extremes (drought and flood) for the NEB and to compare this rate with those found in the scientific literature. The data that will be used in this study are from ANA (Agência Nacional das águas), IBGE (Instituto Brasileiro de Georgrafia e Estatística), and Ministry of National integration.展开更多
This article evaluated the plausible causes of floods and droughts, the relative roles of large-scale climate variability in regional environmental trends, and the prospects for the future of the semiarid Sahel region...This article evaluated the plausible causes of floods and droughts, the relative roles of large-scale climate variability in regional environmental trends, and the prospects for the future of the semiarid Sahel region in the context of periodic climate change. It is pointed out that the most significant rainfall climatological changes in the Sahel probably occurred between 1950 and 1980 with the decrease of the annual rainfall, a very high deficit (about 70%) over the whole region. The last three decades considered in this research (1981-2010) showed some improvement. The more humid conditions were from the last decade 2001 to 2010. One of the most significant climatic variations has been the persistent rainfall decline in the Sahel since late 1960s. Remarkable latitudinal shift of ITF mean position towards the South generated an overall reduction of annual rainfall. Basically, in this manuscript one analyzes the dynamical features on rainfall time series and the association of the cyclic periods with teleconnections under the hypothesis that no alteration has occurred. The results supply a reliable base to develop a methodology for medium to long-term seasonal forecast.展开更多
The advance and retreat of the Sahara Desert are repetitive in decadal time scale. This climate variability, unique in the world, results from the irregular motion of the Intertropical Front (ITF), a discontinuity ori...The advance and retreat of the Sahara Desert are repetitive in decadal time scale. This climate variability, unique in the world, results from the irregular motion of the Intertropical Front (ITF), a discontinuity originated from the convergence of two air masses over the African continent. It results from the convergence of a dry air mass flowing off the North African anticyclone and a southwestern warm and humid air mass that originates off the South Atlantic anticyclone. As it crosses the equator, this air stream is shifted rightwards, becoming southwesterly winds and transporting moisture into the continent. The equatorial thermal low associated with ITF over the continent is deeper and more intense than the Intertropical Convergence Zone (ITCZ) one and its thermodynamic properties differ remarkably, moisture concentration in particular. The ITF annual latitudinal displacement is larger than that of the Atlantic ITCZ, reaching 20?N commonly during the North Hemisphere summer. In this manuscript one discuss about the possibility that Pacific Decadal Oscillation (PDO) is not a regular physical oscillation and its phases duration may not be predictable and be dependent of large magnitude seismic events, which are rare and random. An important point, however, is that the Pacific sea surface temperature (SST) pattern, once established and recognized, may remain for a relative long (decades) period. Its SST pattern, due to its large area extension, modulates the global climate forcing the large scale general circulation features, ENSO in particular, to produce distinct regional impacts, depending on the signal and strength of the SST anomalies. This happened with the ITF in the Sahel and may possibly have occurred with other large scale atmospheric structures, such as the Asian Monsoon, convergence zones and subtropical anticyclones centers positioning.展开更多
文摘The Northeast Brazil (NEB) is known for its temporal and spatial variability of precipitation. Several studies have investigated this variability in order to understand the damaging episodes such as droughts and floods. The phenomenon of drought in the NEB is a complex topic due to affecting?millions of people and being?the object of study in several fields of knowledge. One way to try to argue about this phenomenon is through the concept of vulnerability. The “operability” of this broad concept in natural disasters is a complex task. In order to measure an indicator of vulnerability it is necessary large amount of data from different areas of knowledge, among which?include: meteorology, socio-environmental, economic, public health, among other areas. The main objective of this study is to create an index of vulnerability to climate extremes (drought and flood) for the NEB and to compare this rate with those found in the scientific literature. The data that will be used in this study are from ANA (Agência Nacional das águas), IBGE (Instituto Brasileiro de Georgrafia e Estatística), and Ministry of National integration.
基金sponsored by a POCTI grant from FCT(Portugal)at the present time he is sponsored by a PQ2 grant from CNPq(Brazil)C.E.A.Valadao is sponsored by CAPES(Brazil).
文摘This article evaluated the plausible causes of floods and droughts, the relative roles of large-scale climate variability in regional environmental trends, and the prospects for the future of the semiarid Sahel region in the context of periodic climate change. It is pointed out that the most significant rainfall climatological changes in the Sahel probably occurred between 1950 and 1980 with the decrease of the annual rainfall, a very high deficit (about 70%) over the whole region. The last three decades considered in this research (1981-2010) showed some improvement. The more humid conditions were from the last decade 2001 to 2010. One of the most significant climatic variations has been the persistent rainfall decline in the Sahel since late 1960s. Remarkable latitudinal shift of ITF mean position towards the South generated an overall reduction of annual rainfall. Basically, in this manuscript one analyzes the dynamical features on rainfall time series and the association of the cyclic periods with teleconnections under the hypothesis that no alteration has occurred. The results supply a reliable base to develop a methodology for medium to long-term seasonal forecast.
基金sponsored by a POCTI grant(SFRH/BPD/5614/2001)from FCT(Portugal)at the present time he is sponsored by a PQ2 grant(Proc.302493/2007-7)from CNPq(Brazil).
文摘The advance and retreat of the Sahara Desert are repetitive in decadal time scale. This climate variability, unique in the world, results from the irregular motion of the Intertropical Front (ITF), a discontinuity originated from the convergence of two air masses over the African continent. It results from the convergence of a dry air mass flowing off the North African anticyclone and a southwestern warm and humid air mass that originates off the South Atlantic anticyclone. As it crosses the equator, this air stream is shifted rightwards, becoming southwesterly winds and transporting moisture into the continent. The equatorial thermal low associated with ITF over the continent is deeper and more intense than the Intertropical Convergence Zone (ITCZ) one and its thermodynamic properties differ remarkably, moisture concentration in particular. The ITF annual latitudinal displacement is larger than that of the Atlantic ITCZ, reaching 20?N commonly during the North Hemisphere summer. In this manuscript one discuss about the possibility that Pacific Decadal Oscillation (PDO) is not a regular physical oscillation and its phases duration may not be predictable and be dependent of large magnitude seismic events, which are rare and random. An important point, however, is that the Pacific sea surface temperature (SST) pattern, once established and recognized, may remain for a relative long (decades) period. Its SST pattern, due to its large area extension, modulates the global climate forcing the large scale general circulation features, ENSO in particular, to produce distinct regional impacts, depending on the signal and strength of the SST anomalies. This happened with the ITF in the Sahel and may possibly have occurred with other large scale atmospheric structures, such as the Asian Monsoon, convergence zones and subtropical anticyclones centers positioning.
