The role of the subtropical and equatorial forcing in the development of the Atlantic Niños after 1970s.
International audience; Previous works have reported a connection betweeen Atlantic and Pacific Niños occurring since 1970s. Accordingly, an Atlantic Niño (Niña) seems to favor the development of a Pacific la Niña (Niño) next winter, through an alteration of the Walker circulation. These Atlantic Niños occurring since 1970s are characterized by anomalous SSTs covering the entire tropical band during the summer months, which differs from a more equatorial warming pattern observed in previous decades. The development of this striking spatial pattern of the Atlantic Niños after 70s seems to be associated with an alteration of both North and South Subtropical Highs during the previous Winter-sp…
Cambios en la frecuencia de los Regímenes de Tiempo sobre la región Euro-Atlántica y Mediterránea y su relación con las temperaturas anómalas sobre el Mar Mediterráneo
An exercise has been carried out to assess to what extent the Euro-Atlantic Weather Regimes (WR), described from the ERA-interim Reanalysis in the summer season, projects onto a pool of AGCMAMIP simulations in which sea surface temperatures (SST) are prescribed from observations. Although the model simulations present some biases in the spatial structure and seasonality of WRs, exhibiting also less variability, they are able to capture main WR over the region in summer season: +Middle East –Middle East, +NAO, -NAO. WR paradigm is used to quantify changes in the atmosphere under warmer/colder than normal conditions over the Mediterranean Sea. To address this problem, firstly, changes in the …
Weather Regimes in the Euro-Atlantic and Mediterranean Sector, and Relationship with West African Rainfall over the 1989–2008 Period from a Self-Organizing Maps Approach
Abstract Weather regimes (WRs) have been defined over the Euro-Mediterranean region (15°–70°N, 60°W–60°E) from May to October using the daily sea level pressure, 700-hPa geopotential height, and specific humidity from the European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA)-Interim over the 1989–2008 period. Computations are based on a neural network classification technique referred to as self-organizing maps, and the WRs produced can be used by the scientific community for comparison with other periods, projection onto model outputs, seasonal prediction, or teleconnection studies. The article particularly examines the relationship between WRs and West Africa (WA) rainfall,…
Interannual and decadal SST-forced responses of the West African monsoon
International audience; We review the studies carried out during the African Monsoon Multidisciplinary Analysis (AMMA)-EU on the changes of interannual sea surface temperature (SST)-West African monsoon (WAM) covariability at multidecadal timescales, together with the influence of global warming (GW). The results obtained in the AMMA-EU suggest the importance of the background state, modulated by natural and anthropogenic variability, in the appearance of different interannual modes. The lack of reliability of current coupled models in giving a realistic assessment for WAM in the future is also stated.