Classification of mechanisms, climatic context, areal scaling, and synchronization of floods: the hydroclimatology of floods in the Upper Paraná River basin, Brazil
Floods are the main natural disaster in Brazil, causing substantial economic damage and loss of life. Studies suggest that some extreme floods result from a causal climate chain. Exceptional rain and floods are determined by large-scale anomalies and persistent patterns in the atmospheric and oce...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-12-01
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| Series: | Earth System Dynamics |
| Online Access: | https://www.earth-syst-dynam.net/8/1071/2017/esd-8-1071-2017.pdf |
| Summary: | Floods are the main natural disaster in Brazil, causing substantial economic
damage and loss of life. Studies suggest that some extreme floods result
from a causal climate chain. Exceptional rain and floods are determined by
large-scale anomalies and persistent patterns in the atmospheric and oceanic
circulations, which influence the magnitude, extent, and duration of
these extremes. Moreover, floods can result from different generating
mechanisms. These factors contradict the assumptions of homogeneity, and
often stationarity, in flood frequency analysis. Here we outline a
methodological framework based on clustering using self-organizing maps (SOMs)
that allows the linkage of large-scale processes to local-scale observations. The
methodology is applied to flood data from several sites in the flood-prone
Upper Paraná River basin (UPRB) in southern Brazil. The SOM clustering
approach is employed to classify the 6-day rainfall field over the UPRB into
four categories, which are then used to classify floods into four types based
on the spatiotemporal dynamics of the rainfall field prior to the observed
flood events. An analysis of the vertically integrated moisture fluxes,
vorticity, and high-level atmospheric circulation revealed that these four
clusters are related to known tropical and extratropical processes,
including the South American low-level jet (SALLJ); extratropical cyclones;
and the South Atlantic Convergence Zone (SACZ). Persistent anomalies in the
sea surface temperature fields in the Pacific and Atlantic oceans are also
found to be associated with these processes. Floods associated with each
cluster present different patterns in terms of frequency, magnitude, spatial
variability, scaling, and synchronization of events across the sites and
subbasins. These insights suggest new directions for flood risk
assessment, forecasting, and management. |
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| ISSN: | 2190-4979 2190-4987 |