Low-frequency climate variability in the Atlantic basin during the 20th century

From joint sea surface temperature/sea level pressure (SST/SLP) EOF analyses, lowfrequency variability modes are compared. The multi-decadal oscillation (MDO) changed phases twice during the 20th century, with its north Atlantic SST patterns resembling the Atlantic multi-decadal oscillation (AMO). The quasi-decadal oscillation (QDO) SST patterns displayed a double tripole configuration over the entire Atlantic basin, leading to tropical inter-hemispheric out-of-phase relationship. From the mid-1960s onward, while ST anomalies were negative to the north (negative phases of MDO/AMO), the Sahelian drought persisted with a weaker hurricane power dissipation index (PDI). During that period, the QDO modulated the intensity of the Sahelian drought

7. L'atmosphère comme chef d'orchestre

L’atmosphère est une enveloppe d’une extrême finesse, telle un fragile voile de gaze déposé à la surface de la Terre. Depuis l’espace, le Soleil – turbulent, mais constant réacteur nucléaire – inonde cette planète bleue d’une chaleur vivifiante. Le Soleil et la Lune unissent leurs effets pour faire danser la Terre, entraînée dans une sarabande bien réglée, mue par rayonnement et gravitation. Chaque soir, immuablement, la Terre renvoie vers le ciel un peu de son énergie, sous forme d’ondes lon..

Is there an Indian Ocean dipole and is it independent of the El Niño-Southern Oscillation?

The papers by Saji et al (1999) and Webster et al (1999) describe an equatorial Indian Ocean sea surface temperature (SST) dipole pattern (IOD) which they claim modulates rainfall in East Africa and Indonesia, and operates independently of the global-scale El Nino-Southern Oscillation (ENSO). The concept of possible independence of Indian Ocean SST variability form ENSO has been shaped by research focusing on climate events during the 1990s (eg Behera et al, 1999; Murtugudde et al., 2000). However, in an earlier paper Nicholls (1989) describes a different IOD pattern of variability related to Australian winter rainfall, and argues that this pattern operates largely independently of ENSO. In this paper we demonstrate clearly that with consideration of the evolution of ENSO events, the varying lag correlations between IOD end ENSO indices, and using seasonally stratified data, the apparent ENSO independence disappears form both IODs

An inverse daylighting model for CAAD

International audienceThis paper presents an inverse daylighting model devoted to the design of building openings. The inverse daylighting model includes sky lighting as well as light reflected by surroundings, and therefore combines near-field and far-field light sources. Input data is a heterogeneous lighting distribution on indoor faces called "lighting intention". Openings are considered as a set of intermediate anisotropic light sources. Therefore the geometric reconstruction problem is seen as a source emittance problem. A pin-hole model generates anisotropic light sources and computes light contribution on each indoor faces. An image metric evaluates the distance between this light contribution and lighting intention. Intermediate light sources which have the smallest distance are selected to be part of opening, and therefore define opening shape. This technique is intended to aid opening design in the early stage of architectural design. Our model is validated by test cases and illustrated by a case study in order to show the opening reconstruction process