El Hermanito: El Niño's overlooked little brother in the Atlantic

An oscillation with a period of about 30 months has been identified in the equatorial Atlantic by analyzing sea surface temperature (SST) observations for the period 1949-1991. The 30-month time scale was also found in numerical simulations with an atmospheric general circulation model (AGCM) that was forced by these SSTs and a coupled ocean atmosphere general circulation model (CGCM). Consistent with the theory of tropical air-sea interactions, the Atlantic oscillation (El Hermanito) is an inherently coupled air-sea mode and can be viewed as the Atlantic analogon of the El Nino/Southern Oscillation (ENSO) phenomenon in the equatorial Pacific. El Hermanito is an internal Atlantic mode and appears to be independent of the quasi-biennial (QB) variability observed in the tropical Indian and Pacific Oceans. The discovery of El Hermanito is important to the prediction of Atlantic climate anomalies. (orig.

Subskalige partielle Meereisbedeckung in einem globalen atmosphaerischen Zirkulationsmodell

In dieser Arbeit wird der Einfluss einer subskaligen, partiellen Meereisverteilung und deren Parameterisierung in einem globalen atmosphaerischen Zirkulationsmodell untersucht. Nach einer kurzen Uebersicht ueber die Bedeutung des Meereises im Klimasystem wird ausfuehrlich geschildert, wie von einem derartigen Modell nicht aufloesbare Inhomogenitaeten des Untergrundes parameterisiert werden koennen. Es werden unterschiedliche Verfahren dargestellt und mit Hilfe von Beispielen erlaeutert. (orig./KW)The influence of a subscale, partial sea ice cover and its parametrisation in a global model of atmospheric circulation are investigated. After an outline of the role of sea ice within the cllimate system, the report shows how this model parametrizes non-resolvable background inhomogeneities. Several methods are presented and illustrated by examples. (orig./KW)SIGLEAvailable from TIB Hannover: RR 1857(19) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

El Hermanito: El Nino’s overlooked little brother in the Atlantic

An oscillation with a period of about 30 months has been identified in the equatorial Atlantic by analyzing sea surface temperature (SST) observations for the period 1949-1991. The 30-month time scale was also found in numerical simulations with an atmospheric general circulation model (AGCM) that was forced by these SSTs and a coupled ocean atmosphere general circulation model (CGCM). Consistent with the theory of tropical air-sea interactions, the Atlantic oscillation (El Hermanito) is an inherently coupled air-sea mode and can be viewed as the Atlantic analogon of the El Nifio/Southern Oscillation (ENSO) phenomenon in the equatorial Pacific. El Hermanito is an internal Atlantic mode and appears to be independent of the quasi-biennial (QB) variability observed in the tropical Indian and Pacific Oceans. The discovery of El Hermanito is important to the prediction of Atlantic climate anomalies

El Hermanito: El Nino's overlooked little brother in the Atlantic

An oscillation with a period of about 30 months has been identified in the equatorial Atlantic by analyzing sea surface temperature (SST) observations for the period 1949-1991. The 30-month time scale was also found in numerical simulations with an atmospheric general circulation model (AGCM) that was forced by these SSTs and a coupled ocean atmosphere general circulation model (CGCM). Consistent with the theory of tropical air-sea interactions, the Atlantic oscillation (El Hermanito) is an inherently coupled air-sea mode and can be viewed as the Atlantic analogon of the El Nino/Southern Oscillation (ENSO) phenomenon in the equatorial Pacific. El Hermanito is an internal Atlantic mode and appears to be independent of the quasi-biennial (QB) variability observed in the tropical Indian and Pacific Oceans. The discovery of El Hermanito is important to the prediction of Atlantic climate anomalies. (orig.)Available from TIB Hannover: RR 1347(196) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Interannual to decadal predictability in a coupled ocean-atmosphere general circulation model

The predictability of the coupled ocean-atmosphere climate system on interannual to decadal time scales has been studied by means of ensemble forecast experiments with a global coupled ocean-atmosphere general circulation model. Over most parts of the globe the models predictability can be sufficiently explained by damped persistence as expected from the stochastic climate model concept with damping times of considerably less than a year. Nevertheless, the tropical Pacific and the North Atlantic Ocean exhibit oscillatory coupled ocean-atmosphere modes, which lead to longer predictability time scales. While the tropical mode shares many similarities with the observed ENSO phenomenon, the coupled mode within the North Atlantic region exhibits a typical period of about 30 years and relies on an interaction of the oceanic thermohaline circulation and the atmospheric North Atlantic oscillation. The model's ENSO-like oscillation is predictable up to 1/3-1/2 (2-3years) of the oscillation period both in the ocean and the atmosphere. The North Atlantic yields considerably longer predictability time scales (of the order of a decade) only for quantities describing the model's thermohaline circulation. For surface quantities and atmospheric variables only marginal predictability (of the order of a year) was obtained. The predictability of the coupled signal at the surface is destroyed by the large amount of internally generated (weather) noise. This is illustrated by means of a simple conceptual model for coupled ocean-atmosphere variability and predictability. (orig.)30 refs.Available from TIB Hannover: RR 1347(262) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

North Atlantic interdecadal variability: A coupled air-sea mode

We describe in this paper a coupled air-sea mode in the North Atlantic with a period of about 35 years. The mode was derived from a multi-century integration with a coupled ocean-atmosphere general circulation model and involves interactions of the thermohaline circulation with the atmosphere. If, for instance, the thermohaline circulation is anomalously strong, the North Atlantic is covered by positive sea surface temperature (SST) anomalies. The atmospheric response to these SST anomalies involves a strengthened North Atlantic Oscillation, which leads to anomalous fresh water fluxes off Newfoundland and in the Greenland Sea and the generation of negative sea surface salinity (SSS) anomalies. These SSS anomalies are advected by the subpolar gyre, reaching eventually the convectively active region south of Greenland. The convection and subsequently the strength of the thermohaline circulation are weakened. This leads to a reduced poleward heat transport and the formation of negative SST anomalies, which completes the phase reversal. The mode must be regarded as an inherently coupled air-sea mode. The memory of the coupled ocean-atmosphere system, however, resides in the ocean. The similarity of the model salinity anomalies to the great salinity anomaly which originated in the late 1960s and lasted for roughly 10 years is discussed. Further, we study also the possibility of Atlantic-Pacific interactions. It appears that the Atlantic mode is introduced into the North Pacific Ocean through the atmosphere. (orig.)61 refs.Available from TIB Hannover: RR 1347(223) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Impact of the reduction of calcineurin inhibitors on renal function in heart transplant patients: a systematic review and meta-analysis

International audienceAIMS: Calcineurin inhibitors (CNIs) taken after heart transplantation lead to excellent short-term outcomes, but long-term use may cause chronic nephrotoxicity. Our aim was to identify, appraise, select and analyse all high-quality research evidence relevant to the question of the clinical impact of CNI-sparing strategies in heart transplant patients. METHODS: We carried out a systematic review and meta-analysis of randomized controlled trials on CNI reduction in heart transplant recipients. Primary outcomes were kidney function and acute rejection after 1 year. Secondary outcomes included graft loss, all-cause mortality and adverse events. RESULTS: Eight open-label studies were included, with 723 patients (four tested de novo CNI reduction and four maintenance CNI reduction). Calcineurin inhibitor reduction did not improve creatinine clearance at 12 months 5.46 [-1.17, 12.03] P = 0.32 I(2) = 65.4%. Acute rejection at 12 months (55/360 vs. 52/332), mortality (18/301 vs. 15/270) and adverse event rates (55/294 vs. 52/281) did not differ between the low-CNI and standard-CNI groups. There was significant benefit on creatinine clearance in patients with impaired renal function at 6 months [+12.23 (+5.26, +18.82) ml min(-1) , P = 0.0003] and at 12 months 4.63 [-4.55, 13.82] P = 0.32 I(2) = 75%. CONCLUSIONS: This meta-analysis did not demonstrate a favourable effect of CNI reduction on kidney function, but there was no increase in acute rejection. To provide a better analysis of the influence of CNI reduction patterns and associated treatments, a meta-analysis of individual patient data should be performed