scholarly journals Mediterranean Summer Climate and the Importance of Middle East Topography*

2015 ◽  
Vol 28 (5) ◽  
pp. 1977-1996 ◽  
Author(s):  
Isla R. Simpson ◽  
Richard Seager ◽  
Tiffany A. Shaw ◽  
Mingfang Ting
Keyword(s):  
Middle East ◽  
Large Scale ◽  
Stationary Wave ◽  
Mountain Range ◽  
North African ◽  
Incident Flow ◽  
Low Level ◽  
Community Atmosphere Model ◽  
Moisture Deficit ◽  
The Mediterranean

Abstract In summer, the atmospheric circulation over the Mediterranean is characterized by localized intense subsidence and low-level northerlies over the central to eastern portion of the basin. Here, simulations with the Community Atmosphere Model, version 5 are used to investigate the influence of the elevated terrain of North Africa and the Middle East on this summertime circulation. This builds on previous work that recognized a role for North African topography in localizing the Mediterranean subsidence. By flattening the two regions of elevated terrain in the model, it is demonstrated that, while they both conspire to produce about 30% of the summertime subsidence, contrary to previous work, the mountains of the Middle East dominate in this topographic contribution by far. This topography, consisting primarily of the Zagros mountain range, alters the circulation throughout the depth of the troposphere over the Mediterranean and farther east. The model results suggest that about 20% of the Mediterranean summertime moisture deficit can be attributed to this mountain-induced circulation. This topography, therefore, plays an important role in the climate of the Mediterranean and the large-scale circulation over the rest of Eurasia during the summer. Further stationary wave modeling reveals that the mountain influence is produced via mechanical forcing of the flow. The greatest influence of the topography occurs when the low-level incident flow is easterly, as happens during the summer, primarily because of the presence of condensational heating over Asia. During other seasons, when the low-level incident flow is westerly, the influence of Middle East topography on the Mediterranean is negligible.

scholarly journals On the Orographically Generated Low-Level Easterly Jet and Severe Downslope Storms of March 2006 over the Tacheng Basin of Northwest China

2018 ◽  
Vol 146 (6) ◽  
pp. 1667-1683 ◽  
Author(s):  
Guangxing Zhang ◽  
Da-Lin Zhang ◽  
Shufang Sun
Keyword(s):  
Large Scale ◽  
Inversion Layer ◽  
Dust Storms ◽  
Frozen Soil ◽  
Gradient Force ◽  
Mountain Range ◽  
Pressure Gradient Force ◽  
Low Level ◽  
Downslope Winds ◽  
The Impact

A high-latitude low-level easterly jet (LLEJ) and downslope winds, causing severe dust storms over the Tacheng basin of northwestern China in March 2006 when the dust source regions were previously covered by snow with frozen soil, are studied in order to understand the associated meteorological conditions and the impact of complex topography on the generation of the LLEJ. Observational analyses show the development of a large-scale, geostrophically balanced, easterly flow associated with a northeastern high pressure and a southeastern low pressure system, accompanied by a westward-moving cold front with an intense inversion layer near the altitudes of mountain ridges. A high-resolution model simulation shows the generation of an LLEJ of near-typhoon strength, which peaked at about 500 m above the ground, as well as downslope windstorms with marked wave breakings and subsidence warming in the leeside surface layer, as the large-scale cold easterly flow moves through a constricting saddle pass and across a higher mountain ridge followed by a lower parallel ridge, respectively. The two different airstreams are merged to form an intense LLEJ of cold air, driven mostly by zonal pressure gradient force, and then the LLEJ moves along a zonally oriented mountain range to the north. Results indicate the importance of the lower ridge in enhancing the downslope winds associated with the higher ridge and the importance of the saddle pass in generating the LLEJ. We conclude that the intense downslope winds account for melting snow, warming and drying soils, and raising dust into the air that is then transported by the LLEJ, generated mostly through the saddle pass, into the far west of the basin.

Southern hemisphere low level wind circulation statisticsfrom the Seasat scatterometer

1994 ◽  
Vol 12 (1) ◽  
pp. 65-79 ◽  
Author(s):  
Gad Levy
Keyword(s):  
Large Scale ◽  
Intraseasonal Variability ◽  
Flow Regimes ◽  
Stationary Wave ◽  
Remotely Sensed ◽  
Meridional Flow ◽  
Eof Analysis ◽  
Vector Data ◽  
Mean Flow ◽  
Low Level

Abstract. Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September) of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM) and the National Meteorological Center (NMC) surface analyses. In southern latitudes the remotely sensed winds are stronger than what the weather services' analyses suggest, indicating underestimation by ABM and NMC in these regions. The evolution of the low-level jet and the major stormtracks during the season are studied and different flow regimes are identified. The large-scale variability of the meridional flow is studied with the aid of empirical orthogonal function (EOF) analysis. The dominance of quasi-stationary wave numbers 3, 4, and 5 in the winter flow is evident in both the EOF analysis and the mean flow. The signature of an exceptionally strong blocking situation is evident in July and the special conditions leading to it are discussed. A very large intraseasonal variability with different flow regimes at different months is documented.

scholarly journals Mechanisms for the Dipolar Patterns of Rainfall Variability over Large Islands in the Maritime Continent Associated with the Madden–Julian Oscillation

2020 ◽  
Vol 77 (6) ◽  
pp. 2257-2278
Author(s):  
Jian-Hua Qian
Keyword(s):  
Large Scale ◽  
Rainfall Variability ◽  
Reanalysis Data ◽  
Mountain Range ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Wake Effect ◽  
Low Level ◽  
Rainfall Anomalies ◽  
Normal Rainfall

Abstract Before the eastward-propagating rainy envelope of a Madden–Julian oscillation (MJO) arrives at the Maritime Continent (MC), some islands in the MC experience dipolar patterns of rainfall variability with opposite signs of rainfall anomalies in two neighboring regions within an island. Similar incoherent rainfall anomalies are also observed after the MJO passed the MC. The mechanisms for these dipolar patterns of rainfall anomalies are investigated by using observed and reanalysis data. It is found that the response of rainfall in the MC depends on the direction of wind anomalies and the availability of atmospheric moisture in different phases of the MJO. The low-level wind anomalies over the MC are easterlies in MJO phases 1–3, which cause above-normal rainfall over the mountainous areas in Java, and in western Borneo, western Sumatra, and western Malay Peninsula, respectively. In phases 5–6, the low-level wind anomalies are westerlies and the positive rainfall anomalies are over the eastern part of the islands. Two physical mechanisms are responsible for this phenomenon of the dipolar patterns of rainfall anomalies: 1) the monsoonal damping effect on rainfall over elongated narrow islands—an inverse relationship between the intensity of the diurnal cycle of sea breezes and valley breezes and the large-scale monsoonal wind speed, and 2) the wake effect on rainfall over large and wide islands—above-normal rainfall on the downwind wake side of an island or mountain range with respect to large-scale wind anomalies.

scholarly journals Elements of the dynamical response to climate change over the Mediterranean

2020 ◽  
pp. 1-34
Author(s):  
Alexandre Tuel ◽  
Paul A. O’Gorman ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Large Scale ◽  
Vertical Structure ◽  
Static Stability ◽  
Hadley Cell ◽  
Dynamical Response ◽  
Near Surface ◽  
Low Level ◽  
External Mode ◽  
The Mediterranean ◽  
Circulation Changes

AbstractFuture climate simulations indicate that the Mediterranean Basin will experience large low-level circulation changes during winter, characterized by a strong anomalous ridge that drives a regional precipitation decline. Previous research highlighted how shifts in stationary wave structure and the atmospheric response to reduced warming of the Mediterranean Sea compared to land could explain the development of this anomalous pressure high. Here, we expand on these results and provide new arguments for why and how the Mediterranean is projected to experience large circulation changes during winter. First, we find that zonal asymmetries in the vertical structure of stationary waves are important to explain the enhanced circulation response in the region, and that these asymmetries are related through the external mode to the vertical structure of the mean zonal wind. Second, in winter, the Mediterranean is located just to the north of the Hadley cell edge and consequently relatively free of large-scale descent; together with low near-surface static stability above the sea, this allows the weaker warming trend above the sea to propagate to the low troposphere and trigger a major circulation response. During summer, however, remotely-forced descent and strong static stability prevent the cooling anomaly from expanding upwards. Most of the inter-model scatter in the projected low-level circulation response is related to the spread in upper-tropospheric dynamical trends. Importantly, because climate models exhibit too much vertical coherence over the Mediterranean, our results suggest they overestimate the sensitivity of Mediterranean near-surface circulation to large-scale dynamical changes.

scholarly journals The Modulation of Stationary Waves, and Their Response to Climate Change, by Parameterized Orographic Drag

2017 ◽  
Vol 74 (8) ◽  
pp. 2557-2574 ◽  
Author(s):  
Annelize van Niekerk ◽  
John F. Scinocca ◽  
Theodore G. Shepherd
Keyword(s):  
Climate Change ◽  
Wave Field ◽  
General Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Circulation Model ◽  
Stationary Wave ◽  
Low Level ◽  
The North ◽  
Orographic Drag

Abstract The parameterization of orographic drag processes in atmospheric models remains uncertain because of a lack of observational and theoretical constraints on their formulation and free parameters. While previous studies have demonstrated that parameterized orographic drag acting near the surface has a significant impact on the atmospheric circulation, this work follows a more systematic approach to investigate its impacts on the large-scale circulation and the circulation response to climate change. A set of experiments with a comprehensive atmospheric general circulation model is used to ascertain the range of climatological circulations that may arise from parameter uncertainty. It is found that the Northern Hemisphere (NH) wintertime stationary wave field is strongly damped over the North Pacific (NP) and amplified over the North Atlantic (NA) as a result of increased low-level parameterized orographic drag, both of which are shown to be conducive to higher-latitude westerlies. A comparison with the stationary wave field presented in other studies suggests that the too-zonal NA jet and equatorward NP jet biases that are prevalent in climate models may be at least partly due to their representation of orographic drag. The amplitude of the stationary wave response to climate change across the experiments is shown to scale with the magnitude of low-level parameterized orographic drag through its influence on the present-day climatological stationary wave amplitudes over different sectors of the NH, which is consistent with linear stationary wave theory. This work highlights the importance of fidelity in a model’s basic state for regional climate change projections.

Danaus chrysippus chrysippus (Linnaeus, 1758) ff. 'alcippus' and 'alcippoides' (Lepidoptera: Nymphalidae, Danainae) from Cyprus

2019 ◽  
Vol 70 (3) ◽  
pp. 135-146 ◽  
Author(s):  
Eddie John ◽  
Richard I. Vane-Wright
Keyword(s):  
Middle East ◽  
North Africa ◽  
Recent Observation ◽  
Old World ◽  
The Mediterranean ◽  
Old World Tropics ◽  
Vast Range ◽  
Previous Occasion

We report a recent observation of D. c. chrysippus f. 'alcippus' in Cyprus, a variant of the Plain Tiger or African Queen butterfly infrequently seen in the Mediterranean, especially in the east of the region. D. c. chrysippus f. 'alcippus' appears to have been recorded from Cyprus on just one previous occasion, by R. E. Ellison, in 1939. However, a specimen of the similar f. 'alcippoides' collected by D. M. A. Bate in Cyprus in 1901 could perhaps be the source of Ellison's otherwise undocumented claim. These records are assessed in relation to the known distributions of the various forms of D. chrysippus across the Mediterranean, North Africa and Middle East, and more briefly with respect to the vast range of this butterfly across much of the Old World tropics and subtropics. The ambiguity and potential confusion caused by using an available name to designate both a geographically circumscribed subspecies or semispecies, and a genetically controlled phenotype that can be found far beyond the range of the putative subspecies or semispecies, is also discussed.

Alexandria, Kom el-Dikka. Fieldwork in the 2019 season

2020 ◽  
pp. 469-496
Author(s):  
Grzegorz Majcherek
Keyword(s):  
Large Scale ◽  
Direct Evidence ◽  
Geometric Design ◽  
Late Antique ◽  
Construction Work ◽  
Floor Tiles ◽  
Stone Material ◽  
The Mediterranean ◽  
Late Roman

The report offers an account of archaeological and conservation work carried out at the site. Excavations in the central part of the site (Sector F) were continued for the fourth season in a row. Exploration of remains of early Roman houses led to the discovery of a well preserved multicolored triclinium mosaic floor with a floral and geometric design. A large assemblage of fragments of polychrome marble floor tiles, recorded in the house collapse, showed the scale of importation of decorative stone material from various regions of the Mediterranean. Overlying the early Roman strata was direct evidence of intensive construction work carried out in the vicinity in the form of large-scale kilnworks, supplying lime most probably for the building of the late Roman bath and cistern. Included in the presentation is a brief review of the limited conservation work that was conducted in the complex of late antique auditoria.

Transitions Within Queer North African Cinema

Screen Bodies ◽  
2017 ◽  
Vol 2 (2) ◽  
pp. 64-77 ◽  
Author(s):  
Walter S. Temple
Keyword(s):  
Social Media ◽  
Middle East ◽  
North Africa ◽  
Film Festivals ◽  
Global Awareness ◽  
Critical Factors ◽  
North African ◽  
Mena Region ◽  
African Cinema ◽  
Queer Cinema

In recent years, North African queer cinema has become increasingly visible both within and beyond Arabo-Orientale spaces. A number of critical factors have contributed to a global awareness of queer identities in contemporary Maghrebi cinema, including the dissemination of films through social media outlets and during international film festivals. Such tout contemporain representations of queer sexuality characterize a robust wave of films in the Middle East and North Africa (MENA) region, inciting a new discourse on the condition of the marginalized traveler struggling to locate new forms of self and being—both at home and abroad.

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