Seasonal Distribution of the Boundary Layer Depths Over the Mediterranean Basin

Dayan, Uri; Heffter, J.L.; Miller, J. M.

doi:10.1007/978-94-017-3354-0_10

Cited by 8 publications

(8 citation statements)

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“…In particular, several studies were undertaken to characterize the spatial and temporal behavior of the MLD (Neumann, 1952;Halevy and Steinberger, 1974;Rindsberger, 1974Rindsberger, , 1976Dayan et al, 1988Dayan et al, , 1996Glaser et al, 1993;Lieman and Alpert, 1993;Dayan and Rodnizki, 1999;Ziv et al, 2004) using sounding measurements at the Israel Meteorological Service permanent site in The atmospheric noon-time mixed layer during the summer over the EM region is indicated by a persistent elevated inversion base formed by a clear boundary line separating two differing air masses, a cool and humid mass above ground capped by much warmer and subsiding dry air. The MLD is controlled by the interlaced relationship between the downward motion of the subsiding air aloft and the depth of the PT at the surface (Fig.…”

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

“…Much earlier in the unique study of this type that we are aware of, Dayan et al (1996) evaluated the spatial and seasonal distribution of the MLD over the whole Mediterranean Basin. Based on ∼ 65 000 air measurements from 45 radiosonde stations within and surrounding the basin from spring 1986 through winter 1988, the MLD was derived from the potential temperature gradient measured within the boundary layer and the capping stable layer above it.…”

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

“…The Figure 12. Seasonal map of the mixing layer depth (m) for the summer (June, July, August) of 1987 over the Mediterranean region at 12:00 UTC (from Dayan et al, 1996; used with permission from Kluwer Academic Publishers).…”

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

“…Dayan et al (1996) found that the most striking temporal effect on MLD distribution over the basin is caused by synoptic weather systems and the intensity of the sea breeze along the coast. The diminishing of the MLD over the Mediterranean Basin moving from its center eastwards toward the EM coast that they have observed is consistent with the unique series of measurements of the temperature profiles performed during the summer of 1987 near the Port of Ashdod (31.82 • N, 34.65 • E), some 40 km south of Tel Aviv (Israel) at 2 to 22 km from shore using a tethered balloon where prominent inversion bases of 350 to 600 m a.s.l.…”

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

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Atmospheric pollution over the eastern Mediterranean during summer – a review

et al. 2017

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Abstract. The eastern Mediterranean (EM) is one of the regions in the world where elevated concentrations of primary and secondary gaseous air pollutants have been reported frequently, mainly in summer. This review discusses published studies of the atmospheric dispersion and transport conditions characterizing this region during the summer, followed by a description of some essential studies dealing with the corresponding concentrations of air pollutants such as ozone, carbon monoxide, total reactive nitrogen, methane, and sulfate aerosols observed there.The interlaced relationship between the downward motion of the subsiding air aloft induced by global circulation systems affecting the EM and the depth of the Persian Trough, a low-pressure trough that extends from the Asian monsoon at the surface controlling the spatiotemporal distribution of the mixed boundary layer during summer, is discussed. The strength of the wind flow within the mixed layer and its depth affect much the amount of pollutants transported and determine the potential of the atmosphere to disperse contaminants off their origins in the EM. The reduced mixed layer and the accompanying weak westerlies, characterizing the summer in this region, led to reduced ventilation rates, preventing an effective dilution of the contaminants. Several studies pointing at specific local (e.g., ventilation rates) and regional peculiarities (long-range transport) enhancing the build-up of air pollutant concentrations are presented.Tropospheric ozone (O 3 ) concentrations observed in the summer over the EM are among the highest over the Northern Hemisphere. The three essential processes controlling its formation (i.e., long-range transport of polluted air masses, dynamic subsidence at mid-tropospheric levels, and stratosphere-to-troposphere exchange) are reviewed. Airborne campaigns and satellite-borne initiatives have indicated that the concentration values of reactive nitrogen identified as precursors in the formation of O 3 over the EM were found to be 2 to 10 times higher than in the hemispheric background troposphere. Several factors favor sulfate particulate abundance over the EM. Models, aircraft measurements, and satellite-derived data have clearly shown that sulfate has a maximum during spring and summer over the EM. The carbon monoxide (CO) seasonal cycle, as obtained from global background monitoring sites in the EM, is mostly controlled by the tropospheric concentration of the hydroxyl radical (OH) and therefore demonstrates high concentrations over winter months and the lowest concentrations during summer when photochemistry is active. Modeling studies have shown that the diurnal variations in CO concentration during the summer result from long-range CO transport from European anthropogenic sources, contributing 60 to 80 % of the boundary-layer CO over the EM. The values retrieved from satellite data enable us to derive the spatial distribution of methane (CH 4 ), identifying August as the month with the highest levels over the EM. The outcomes of a...

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Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

Section: Atmospheric Dispersion Conditions Over the Eastern Mediterramentioning

confidence: 99%

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Atmospheric pollution over the eastern Mediterranean during summer – a review

et al. 2017

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“…The advanced parcel method and the evaluation of the gradient of the mixing ratio of water vapour seems to be most appropriate (Seibert et al, 2000;De Tomasi and Perrone, 2006) for convective and near neutral conditions; in stable conditions approaches based on the Richardson number and on the low level wind profile are more suitable (Joffre et al, 2001). In both stable and unstable cases, the detection of a critical inversion in the temperature profile, located at the top of the mixing layer, renders a mixing height estimate (Heffter, 1980;Dayan et al, 1996). In this analysis, we developed and used a modified version of the temperature-inversion method, as it requires only temperature measurements that are more reliable and usually available.…”

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confidence: 99%

Setup of tools and dataset selection for MBL investigation over a coastal Mediterranean site – preliminary results

Velea

Liberti

Sempreviva³

et al. 2009

Adv. Sci. Res.

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Abstract. We propose the height zi of the inversion in the vertical profile of potential temperature, on the top of a mixed layer or of a residual layer as a relevant parameter for retrieving information related to water vapour in the lower layers of the atmosphere, from currently available operational satellites information. We estimated zi using an algorithm where a set of threshold values in the vertical gradients of potential temperature are used to analyse the available profiles in order to find relevant inversions. Thresholds are derived from the subjective analysis of a set of high vertical resolution soundings from the coastal site of the Italian Meteorological Service of Pratica di Mare (WMO #16245, lat. 41.66° N, lon. 12.45° E). The sensitivity of the method to vertical sampling is tested comparing results obtained by applying the method to two sets of about 6500 raw and sampled radiosoundings during the period 2002–2008. Differences in average seasonal and six-hourly values of zi from the two datasets are found within the range 5–10%. The method was then applied to a larger set of soundings from coastal and continental Mediterranean sites collected in a standard archive. It was found that mean summer values of zi at coastal sites are lower than in winter, conversely to continental sites. Furthermore, values of zi found using the proposed algorithm show a systematically higher inversion if compared to height found using the Richardson Number method, although there are cases when both identify the inversion at the same height.

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Synoptic Scale Circulation and Mesoscale Processes

Dayan¹

2023

Atmospheric Chemistry in the Mediterranean Region

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Seasonal Distribution of the Boundary Layer Depths Over the Mediterranean Basin

Cited by 8 publications

References 8 publications

Atmospheric pollution over the eastern Mediterranean during summer – a review

Atmospheric pollution over the eastern Mediterranean during summer – a review

Setup of tools and dataset selection for MBL investigation over a coastal Mediterranean site – preliminary results

Synoptic Scale Circulation and Mesoscale Processes

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