@article{fdi:010057315,
  title = {{W}eather regimes over {S}enegal during the summer monsoon season using self-organizing maps and hierarchical ascendant classification. {P}art {II} : interannual time scale},
  author = {{G}u{\`e}ye, {A}. {K}. and {J}anicot, {S}erge and {N}iang, {A}. and {S}awadogo, {S}. and {S}ultan, {B}enjamin and {D}iongue-{N}iang, {A}. and {T}hiria, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he aim of this work is to define over the period 1979-2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over {S}enegal. "{I}nterannual" synoptic weather regimes are defined by removing the influence of the mean 1979-2002 seasonal cycle. {T}his is different from {P}art {I} where the seasonal evolution of each year was removed, then removing also the contribution of interannual variability. {A}s in {P}art {I}, the self-organizing maps approach, a clustering methodology based on non-linear artificial neural network, is combined with a hierarchical ascendant classification to compute these regimes. {N}ine weather regimes are identified using the mean sea level pressure and 850 h{P}a wind field as variables. {T}he composite circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity and rainfall. {T}hey are also consistent with the distribution of rainfall extremes. {T}hese regimes have been then gathered into different groups. {A} first group of four regimes is included in an inner circuit and is characterized by a modulation of the semi-permanent trough located along the western coast of {W}est {A}frica and an opposite modulation on the east. {T}his circuit is important because it associates the two wettest and highly persistent weather regimes over {S}enegal with the driest and the most persistent one. {O}ne derivation of this circuit is highlighted, including the two driest regimes and the most persistent one, what can provide important dry sequences occurrence. {A}n exit of this circuit is characterised by a filling of the {S}aharan heat low. {A}n entry into the main circuit includes a southward location of the {S}aharan heat low followed by its deepening. {T}he last weather regime is isolated from the other ones and it has no significant impact on {S}enegal. {I}t is present in {J}une and {S}eptember, and missing in {J}uly and {A}ugust, meaning that this is a weather regime more specific of the intermediate seasons than the summer. {I}t is included in a large-scale pattern covering the northern latitudes of {E}urope. {T}he correspondence between these "interannual" synoptic weather regimes and the "pure" synoptic regimes defined in {P}art {I} has been established. {B}y selecting a high statistical significance level for these correspondences, each of five out of nine "interannual" weather regimes has a close correspondence with one "pure" synoptic weather regime, one out of them have links with two "pure" regimes, and the last three regimes have no significant correspondence in terms of "pure" regimes. {H}owever when considering more moderate links, two out of these three regimes show a connection with a "pure" regime, and the last one remains isolated. {T}he ensemble of the weather regimes occurrences can explain a significant part of interannual variability of summer rainfall amount over {S}enegal, especially linked to the driest and the wettest weather regimes occurrences. {I}t is also shown that {S}enegal rainfall state is very sensitive to a small displacement or deformation of the weather regime patterns.},
  keywords = {{W}eather regimes ; {S}enegal ; {S}elf-organizing maps ; {H}ierarchical ascendant classification},
  booktitle = {},
  journal = {{C}limate {D}ynamics},
  volume = {39},
  numero = {9-10},
  pages = {2251--2272},
  ISSN = {0930-7575},
  year = {2012},
  DOI = {10.1007/s00382-012-1346-8},
  URL = {https://www.documentation.ird.fr/hor/fdi:010057315},
}