Recent climatological trend of the Saharan heat low and its impact on the West African climate

The Saharan heat low (SHL) plays a pivotal role in the West African monsoon system in spring and summer. The recent trend in SHL activity has been analysed using two sets of numerical weather prediction (NWP) model reanalyses and Atmospheric Models Intercomparison Project simulations from 15 climate models performed in the framework of the 5th Coupled Models Intercomparison Project (CMIP5) exercise. A local increase of temperature in the Sahara during the 90s is found in the two sets of NWP models temperature. This increase is stronger within the SHL region than over the surrounding areas. Using different temporal filters (under 25 days, 25–100 days and above 300 days), we show that this is accompanied by a slight but widespread increase of temperature, and a change in the filtered signal under 25 days during the transition period of the 90s. We also show that SHL pulsations occurring at different time scales impact the West Africa climate on a variety of spatial scales, from the regional scale (for the high band pass) to the synoptic scale (for the low band pass signal). Despite a large variability in the temporal trends for 15 climate models from the CMIP5 project, the warming trend in the 90s is observed in the models ensemble mean. Nevertheless, large discrepancies are found between the NWP models reanalyses and the climate model simulations regarding the spatial and temporal evolutions of the SHL as well as its impact on West African climate at the different time scales. These comparisons also reveal that climate models represent the West African monsoon interactions with SHL pulsations quite differently. We provide recommendations to use some of them depending on the time scales of the processes at play (synoptic, seasonal, interannual) and based on key SHL metrics (location, mean intensity, global trend, interaction with the West African monsoon dynamics).JRC.H.7-Climate Risk Managemen

Magnetobiostratigraphy of the Spathian to Anisian (Lower to Middle Triassic) Kçira section, Albania

Magnetobiostratigraphic data are presented from three Early/Middle Triassic Han-Bulog Limestone successions from Kçira, northern Albania. A total of 206 standard palaeomagnetic samples were obtained for thermal demagnetization and statisticalanalysis from the 42, 10 and 5m thick sections. The reversal-bearing characteristic component, carried by haematite and magnetite, defines a composite sequence of six main polarity intervals (Kçln to Kç3r) in which are embedded four short polarity intervals, one at the base of Kçln and three towards the top of Kçlr. The early acquisition of the characteristic remanence is supported by the lateral correlation of magnetozones between sections. The Early/Middle Triassic boundary, approximated by the first occurrence of the conodont Chiosella timorensis, falls close to the Kçlr/Kç2n polarity transition. This is in good agreement with recently published magnetobiostratigraphic data from the coeval Chios (Greece) sections. The palaeomagnetic pole calculated from the Kçira characteristic directions lies close to the Triassic portion of the apparent polar wander path for Laurussia (in European coordinates). However, a 40-45" clockwise rotation of the external zone of the Albano-Hellenic Belt to the south of the Scutari-Pec Line is thought to have occurred since the Early-Middle Miocene. The Kçira pole acquires a West Gondwana affinity when restored for the Neogene clockwise rotation. If the clockwise rotation was entirely related to Neogene tectonics, the Kçira area was evidently associated with West Gondwana and located at 12-16"N of the western Tethys margin

Towards a better definition of the Middle Triassic magnetostratigraphy and biostratigraphy in the Tethyan realm

Magnetostratigraphic and biostratigraphic data for the Middle Triassic (Anisian) were obtained from the Han-Bulog facies in the Nderlysaj section from the Albanian Alps and the Dont and Bivera formations in the Dont–Monte Rite composite section from the Dolomites region of northern Italy. The Nderlysaj section is biochronologically bracketed between the late Bithynian and early Illyrian substages (i.e., late-early and early-late Anisian), whereas the Dont–Monte Rite section comprises the late Pelsonian and the early Illyrian substages. The data from Nderlysaj and Dont–Monte Rite, in conjunction with already published data, allow us to construct a nearly complete composite geomagnetic polarity sequence tied to Tethyan ammonoid and conodont biostratigraphy from the late Olenekian (late-Early Triassic) to the late Ladinian (late-Middle Triassic). New conodont data require revision of the published age of the Vlichos section (Greece)

L’Ecloga II. La vita silenziosa di Andrea Zanzotto

The «Ecloga II. The silent life» is included in one of the most influential books of poetry of the late italian twentieth century, «IX Ecloghe»(1962) by Andrea Zanzotto (1921-2011). This work is very important because it announces one of the masterpieces of contemporary Italian poetry, «La Beltà», published by Zanzotto in 1968, but also for the great artistic value of many poems that includes. The article analyzes in detail the text of «Ecloga II» and proposes an interpretation substantially different from those now prevalent. Close examination of the poem shows that the expression of the title (“silent life”) has a meaning very articulate and ambivalent axiology. This interpretation considers the most reliable studies on Zanzotto and «IX Ecloghe» and emphasizes the importance (for the Venetian poet between the Fifties and Sixties) of phenomenological existentialist thought. In particular, it is assumed that the poet alludes to an idea of silence (and "silent life") that may be related to some theoretical clarifications of «Phenomenology of Perception» by Merleau-Ponty (but not only). This interpretation differs from the hermeneutics of silence generally offered by the most accredited critics of Zanzotto (from Agosti to Dal Bianco, until the recent book by Luigi Tassoni). Zanzotto believes the “silence” is not only a subjective and objective experience as opposed to the noise (verbal and non-verbal), but it is essentially an ontological dimension connected to give “mute” of Nature and Being ("Physics" and Ontology in the work of the author are closely linked). A dimension pre-linguistic but saturated of Sense, the expression of which is not attributable only to a particular rhetorical (reticence, blank, breaks, etc.) but involves the origin of the transaction poetic. The article also proposes some ideas for a possible re-consideration of the overall character of the different stages of production poetic of Zanzotto, from «Dietro il paesaggio» (1951) to «Conglomerati» (2009)

A synoptic characterization of the dust transport and associated thermal anomalies in the Mediterranean basin

Presentación realizada para las XXXII Jornadas Científicas de la Asociación Meteorológica Española y 13º Encuentro Hispano-Luso de Meteorología celebrados en Alcobendas (Madrid), del 28 al 30 de mayo de 2012

The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign

The radiative effects of biomass burning aerosols (BBAs) on low-level atmospheric circulation over southern Africa are investigated on 5 September 2017 during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign. This is conducted using a variety of in situ and remote sensing observations, as well as two 5 d ensemble simulations made with the Meso-NH mesoscale model, one including the direct and semi-direct radiative effects of aerosols and one in which these effects are not included. We show that the radiative impact of BBA building up over a period of 5 d in the Meso-NH simulations can lead to significantly different circulations at low and middle levels, thereby affecting dust emissions over southern Namibia and northwestern South Africa as well as the transport of BBA in a so-called “river of smoke”. While most of the regional-scale dynamics, thermodynamics and composition features are convincingly represented in the simulation with BBA radiative effects, neglecting the radiative impact of BBA leads to unrealistic representations of (i) the low-level jet (LLJ) over the plateau, which is the main low-level dynamic feature fostering dust emission, and (ii) the mid-level dynamics pertaining to the transport of BBA from the fire-prone regions in the tropics to the mid-latitudes. For instance, when the BBA radiative impacts are not included, the LLJ is too weak and not well established over night, and the developing convective planetary boundary layer (PBL) is too deep compared to observations. The deeper convective PBL over Etosha and surrounding areas is related to the enhanced anomalous upward motion caused by the eastern displacement of the river of smoke. This eastern displacement is, in turn, related to the weaker southerly African easterly jet. Both ensemble simulations provide clear evidence that the enhanced near-surface extinction coefficient values detected from observations over Etosha are related to the downward mixing of BBA in the developing convective boundary layer rather than dust being emitted as a result of the LLJ breakdown after sunrise. This study suggests that the radiative effect of BBAs needs to be taken into account to properly forecast dust emissions in Namibia

The fast response of Sahel precipitation to climate change allows effective mitigation action

Climate change will drive major perturbations of the West African summer monsoon. A zonal contrast in precipitation will develop at the end of the century, with an increase in precipitation over the central Sahel and a decrease in precipitation over the western Sahel. Such a zonal contrast results from the antagonist effects of the fast (due to enhanced radiative warming over land, and over the North Hemisphere, relative to the South Hemisphere) and slow (associated with long-term changes in oceanic circulation) responses of precipitation to increasing greenhouse gases. While such changes have already been assessed, less attention has been given to their temporality, an issue of major importance to promote efficient mitigation and adaptation measures. Here, we analyse the future evolution of precipitation changes decomposed into a fast and a slow response, showing that the fast response dominates the slow one. From this evidence, we highlight that mitigation strategies may be successful at reducing the effect of climate change on Sahel precipitation within a few decades, by muting the fast response. This decomposition also allows for a better understanding of the uncertainty of climate model predictions in Africa