Semi‐objective classification for daily synoptic systems: application to the eastern Mediterranean climate change

Alpert, Pinhas; Osetinsky, I.; Ziv, Baruch; Shafir, H.

doi:10.1002/joc.1036

Cited by 263 publications

(378 citation statements)

References 43 publications

Supporting

Mentioning

365

Contrasting

Unclassified

Order By: Relevance

“…The changes in the frequency of occurrence and the magnitude of major RST-generated floods in the Negev, Arava and Dead Sea western watersheds stand in good agreement with previous conclusions (Alpert et al 2004) concerning: (i) the trend in the annual frequencies of the Red Sea Trough (RST) systems in the Eastern Mediterranean (EM) region for 1948-2000 which has nearly doubled since the 1960s from 50 to about 100 days per year, and (ii) a dominant decreasing trend of rainfall in most of the EM, along with an increase in the southern part of the EM region (when the RST is deep enough to bring tropical moisture over this area), both of which are explained by the increase in the active and stormy types of RST situations.…”

Section: Rst Floods and Climate Changesupporting

confidence: 78%

“…The present synoptichydrologic flood analysis differs from the latter study by a longer flood series, more informative samples of major events and using a classification of synoptic systems over the Eastern Mediterranean (Alpert et al 2004) as a tool for categorizing floods to synoptic oriented classes.…”

Section: Introductionmentioning

confidence: 94%

“…Categorizing flood events to synoptic oriented classes was based on data verification for the paired databases of: (1) floods in the research area (Israel Hydrological Service) and (2) synoptic systems over the Eastern Mediterranean (Alpert et al 2004(Alpert et al , updated to 2007. Sea-level pressure (SLP) charts of the major synoptic systems are depicted in Fig.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Shentsis

Laronne

Alpert

2012

Hydrological Sciences Journal

View full text Add to dashboard Cite

Results of a comprehensive synoptic-hydrological analysis of major flood events in the Negev are presented. A low threshold for major flood data was set to be the 10-year recurrence interval of peak discharge and/or flood volume magnitude. Altogether, 75 major flood events, or 133 hydrometrically monitored floods, were extracted. These events were categorized according to synoptic oriented classes by verification of the paired databases of: (a) floods in the study area, and (b) synoptic systems over the Eastern Mediterranean. For the study area, two of the most frequent flood-generating synoptic systems are the autumn Red Sea Trough (RST), 31%, and winter cyclones, 49%. The entire RST series consists of 24 major flood events (55 floods). The synoptic definition was corroborated by analysing the specific form of flood hydrographs and the ratio of flood volume to peak discharge. Regional analysis shows increased contribution of RST events southwards from 30% to 90% with a respective decrease in the number of cyclone events. By comparing two 22-year sub-periods (1964-1985 and 1986-2007), a positive trend in the frequency and magnitudes of RST flood events is discerned. There is also an increased tendency for the occurrence of cyclone floods.Key words floods; synoptic system; Red Sea Trough (RST); climate change; Negev; Arava; Dead Sea; Mediterranean Crues dans le Néguev, Israël (1964-2007) dues à des dépressions sur la Mer RougeRésumé Nous présentons les résultats d'une analyse exhaustive synoptique/hydrologique des crues majeures dans le Néguev (1964Néguev ( -2007. Le seuil inférieur pour les crues majeures a été défini comme le débit de pointe ou le volume de la crue de récurrence 10 ans. Au total, 75 crues majeures, ou 133 crues observées hydrométriquement, ont été extraites. Ces événements ont été classifiés selon des classes synoptiques par vérification des bases de données appariées : (a) des crues dans la zone d'étude, et (b) des systèmes synoptiques sur la Méditerranée orientale. Pour la zone d'étude, deux des systèmes synoptiques générant le plus fréquemment des crues sont les dépressions sur la Mer Rouge (DMR) en automne, 31%, et les cyclones d'hiver, 49%. La série DMR complète est constituée de 24 crues majeures (55 crues). La définition synoptique a été corroborée par l'analyse de la forme spécifique des hydrogrammes de crues et le rapport entre volume et débit de pointe des crues. L'analyse régionale montre une contribution des événements DMR augmentant de 30% à 90% vers le Sud avec une diminution correspondante du nombre d'événements cycloniques. En comparant deux sous-périodes de 22 ans (1964-1985 et 1986-2007), on discerne une tendance positive dans la fréquence et la magnitude des crues DMR. Il ya aussi une tendance croissante à l'apparition de crues d'origine cyclonique.

show abstract

Section: Rst Floods and Climate Changesupporting

confidence: 78%

Section: Introductionmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Shentsis

Laronne

Alpert

2012

Hydrological Sciences Journal

View full text Add to dashboard Cite

show abstract

“…This striking finding contradicts the widely accepted idea that the Sharav cyclone is the main contributor to the suspended dust over this region. The annual occurrence distribution of the two most effective synoptic types explains why the yearly maximum is in the late winter and early spring, when these two systems are most frequent (Alpert et al, 2004). For 4.1% of the dust observations the synoptic types were difficult to classify, or coincided with transition between different distinct synoptic types (termed 'undefined' in Table II).…”

Section: Relation To Synoptic and Large-scale Systemsmentioning

confidence: 99%

Suspended dust over southeastern Mediterranean and its relation to atmospheric circulations

Dayan

Ziv

Shoob

et al. 2007

Intl Journal of Climatology

143

View full text Add to dashboard Cite

ABSTRACT:The Middle East deserts are often subjected to dust, which reduces horizontal visibility to 5 km, and sometimes even to <1 km. The present study examines the annual and inter-annual occurrences of dust events based on 37 years of visibility observations from Hazerim (near Beer Sheba) correlated with PM 10 dust concentration. The visibility data was converted to PM 10 dust concentration, using concurrent data for three years. We then analyse the linkage between dust and synoptic-to global-scale weather systems.The monthly data indicate that the dust season starts in October and ends in May, with a maximum in March. More than 89% of the total annual dust is accumulated between December and May, the 'high dust season'. The annual totals vary as much as an order of magnitude from year to year.The synoptic system that produces the majority of the dust over the northern Negev is the Cyprus Low, contributing 2/3 of both the total yearly dust yield and of the number of dust observations. This suggests that a positive relationship exists between the dust in the Negev and rainfall in north Israel, both of which are generated by Cyprus Lows. Indeed, a significant (at 0.05 level) correlation of +0.30 was found between the two. Correlation maps evidence that in dustrich years the cyclonic activity over the Mediterranean is abnormally high and in poor-dust years it is low. A highly significant negative correlation (−0.66) was found between the dust yield and the intensity of the North Atlantic oscillation (NAO), which modulates the cyclonic activity over Europe and the northern Mediterranean. This may also imply that periods in which more dust accumulated as loess in the northern Negev may indicate the existence of negative NAO phase, and concurrently, warmer conditions over the Sahara, colder conditions over Europe and enhanced rainfall over the Mediterranean Basin.

show abstract

“…Maheras et al, 2000;Alpert et al, 2004). These studies are mainly based on geopotential height or sea-level pressure patterns.…”

Section: Introductionmentioning

confidence: 99%

Climatic features of atmospheric stability in the Mediterranean region (1948–2006): spatial modes, inter‐monthly and inter‐annual variability

Lolis

2007

Meteorological Applications

View full text Add to dashboard Cite

ABSTRACT:The predominant spatial modes of atmospheric stability over the Mediterranean region are revealed by applying factor analysis and cluster analysis on the daily 2.5°× 2.5°grid point values of K-index for the period 1948-2006. At first, S-mode factor analysis is applied on the K-index time series in order to reduce the dimensionality of the data set. The k-means cluster analysis is then applied to the factor scores time series, and the days are classified into 12 clusters with distinct and characteristic spatial distributions of the K-index. The 12 spatial modes revealed are associated with the prevailing atmospheric circulation types and/or the thermal and humidity characteristics of the lower and the middle troposphere. The inter-monthly variations of their frequency reveal the seasonal factors that contribute to their predominance. The seasonality of the 12 clusters shows that three of them prevail mainly in winter, three of them prevail mainly in summer, and the other six clusters present a relatively even seasonal distribution. The inter-annual variations of their frequency exhibit considerable long-term changes, providing also some possible indications of the oncoming climatic change. The continuous decrease of the typical high instability pattern of late spring and early summer and the recent increase of one of the typical high instability winter patterns provide some useful information about climate variability in the Mediterranean.

show abstract

Semi‐objective classification for daily synoptic systems: application to the eastern Mediterranean climate change

Cited by 263 publications

References 43 publications

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Suspended dust over southeastern Mediterranean and its relation to atmospheric circulations

Climatic features of atmospheric stability in the Mediterranean region (1948–2006): spatial modes, inter‐monthly and inter‐annual variability

Contact Info

Product

Resources

About