Timing and rate of exhumation of Central Sredna Gora Zone basement, Bulgaria

2021 ◽  
Author(s):  
Eleonora Balkanska ◽  
Stoyan Georgiev ◽  
Alexandre Kounov ◽  
Irena Peytcheva ◽  
Takahiro Tagami ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Balkan Peninsula ◽  
Metamorphic Complex ◽  
Thrust Belt ◽  
Ministry Of Education ◽  
The South ◽  
Exhumation Rate ◽  
The North ◽  
Thrace Basin ◽  
Exhumation Rates

<p>Sredna Gora Zone in Bulgaria is confined between the Balkan fold-thrust belt to the north and the Rhodope metamorphic complex to the south. The pre-Mesozoic basement of the central parts of the zone consists of Variscan high-grade metamorphic rocks intruded by Late Carboniferous granitoid plutons. They are transgressively overlaid by Triassic epicontinental, arc-related Upper Cretaceous volcaniclastic and Paleocene continental deposits. The Paleogene-Neogene sediments of the Thrace basin cover unconformably the older rock sequences. The zone experienced several compressional and extensional events during the Alpine time followed by post-orogenic extension in the Cenozoic.</p><p>We performed apatite fission-track analysis on rocks from the central, topographically highest parts of the Sredna Gora Zone in order to constrain the cooling history of the Variscan basement. With this aim four granitic samples were collected at different altitude (between 565 and 1604 m) from the tectonically uninterrupted section along the slope of Sredna Gora Mountains. The samples were processed and analyzed in the newly established Low-Temperature Thermochronology Laboratory in Bulgaria using LA-ICP-MS technique.</p><p>The samples yield apatite FT ages between 41.6 ± 2.6 (the highermost sample) and 39.4 ± 3.1 (the lowermost sample). The obtained confined mean tracks lengths are between 12.81 and 14.06 µm with standard deviation between 0.99 and 2.11 µm. The Dpar values vary from 1.75 µm to 1.46 µm (with standard deviation of approx. 0.20 µm).</p><p>The obtained positive age-altitude correlation suggests indeed that the studied part of the basement has cooled as one single block. The apparent exhumation rate is estimated to 0.46 mm/year. However, the positive Dpar-age correlation implies that the age dispersion could be influenced by apatite kinetic variability and hence relatively different closure temperature for the analysed samples may be suggested. Therefore, we consider the estimated apparent exhumation rate as only the minimum possible rate. The thermal models of the analysed samples (using HeFTy software) also show moderate cooling rates in the period between 45 and 35 Ma. This cooling could be related to the period of post-orogenic denudation and extension during the Eocene, associated with formation of the Thrace basin to the south-southeast. This extensional event, known from the whole Balkan Peninsula, is well documented in the neighbouring Balkan fold-thrust belt and the Rhodope metamorphic complex from where much faster exhumation rates were reported.</p><p> </p><p><strong>Acknowledgements</strong>. The study is supported by the grant 04/9 funded by the National Science Fund, Ministry of Education and Science, Bulgaria.</p>

scholarly journals The Dabie Extensional Tectonic System: Structural Framework

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Quanlin Hou ◽  
Hongyuan Zhang ◽  
Qing Liu ◽  
Jun Li ◽  
Yudong Wu
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Metamorphic Complex ◽  
The South ◽  
Magma Intrusion ◽  
The North ◽  
Extensional Tectonic ◽  
Mechanism Transition ◽  
Tectonic System

A previous study of the Dabie area has been supposed that a strong extensional event happened between the Yangtze and North China blocks. The entire extensional system is divided into the Northern Dabie metamorphic complex belt and the south extensional tectonic System according to geological and geochemical characteristics in our study. The Xiaotian-Mozitan shear zone in the north boundary of the north system is a thrust detachment, showing upper block sliding to the NNE, with a displacement of more than 56 km. However, in the south system, the shearing direction along the Shuihou-Wuhe and Taihu-Mamiao shear zones is tending towards SSE, whereas that along the Susong-Qingshuihe shear zone tending towards SW, with a displacement of about 12 km. Flinn index results of both the north and south extensional systems indicate that there is a shear mechanism transition from pure to simple, implying that the extensional event in the south tectonic system could be related to a magma intrusion in the Northern Dabie metamorphic complex belt. Two 40Ar-39Ar ages of mylonite rocks in the above mentioned shear zones yielded, separately, ~190 Ma and ~124 Ma, referring to a cooling age of ultrahigh-pressure rocks and an extensional era later.

Zircon U–Pb geochronology of the Zanhuang metamorphic complex: reappraisal of the Palaeoproterozoic amalgamation of the Trans-North China Orogen

2013 ◽  
Vol 150 (4) ◽  
pp. 756-764 ◽  
Author(s):  
LING-LING XIAO ◽  
GUO-DONG WANG ◽  
HAO WANG ◽  
ZONG-SHENG JIANG ◽  
CHUN-RONG DIWU ◽  
...  
Keyword(s):  
High Resolution ◽  
North China Craton ◽  
North China ◽  
Metamorphic Complex ◽  
Middle Section ◽  
The South ◽  
The North ◽  
Facies Metamorphism ◽  
Isothermal Decompression ◽  
Metamorphic Terranes

AbstractAmphibolites and metapelites exposed in the Zanhuang metamorphic complex situated in the south-middle section of the Trans-North China Orogen (TNCO) underwent upper-amphibolite-facies metamorphism and record clockwise P–T paths including retrograde isothermal decompression. High-resolution zircon U–Pb geochronological analyses indicate that the metamorphic peak occurred during ~ 1840–1860 Ma, which is in accordance with the ubiquitous metamorphic ages of ~ 1850 Ma retrieved by miscellaneous geochronologic methods throughout the metamorphic terranes of the northern TNCO, confirming that the south-middle section of the TNCO was involved in the amalgamation of the Eastern and Western Blocks of the North China Craton during the Palaeoproterozoic.

scholarly journals Interannual Variability of Northwest Australian Tropical Cyclones

2010 ◽  
Vol 23 (17) ◽  
pp. 4538-4555 ◽  
Author(s):  
Kevin H. Goebbert ◽  
Lance M. Leslie
Keyword(s):  
Standard Deviation ◽  
North America ◽  
Atlantic Ocean ◽  
Southern Oscillation ◽  
South Atlantic ◽  
Conclusive Evidence ◽  
South Atlantic Ocean ◽  
Northwest Pacific ◽  
The South ◽  
The North

Abstract Tropical cyclone (TC) activity over the southeast Indian Ocean has been studied far less than other TC basins, such as the North Atlantic and northwest Pacific. The authors examine the interannual TC variability of the northwest Australian (NWAUS) subbasin (0°–35°S, 105°–135°E), using an Australian TC dataset for the 39-yr period of 1970–2008. Thirteen TC metrics are assessed, with emphasis on annual TC frequencies and total TC days. Major findings are that for the NWAUS subbasin, there are annual means of 5.6 TCs and 42.4 TC days, with corresponding small standard deviations of 2.3 storms and 20.0 days. For intense TCs (WMO category 3 and higher), the annual mean TC frequency is 3.0, with a standard deviation of 1.6, and the annual average intense TC days is 7.6 days, with a standard deviation of 4.5 days. There are no significant linear trends in either mean annual TC frequencies or TC days. Notably, all 13 variability metrics show no trends over the 39-yr period and are less dependent upon standard El Niño–Southern Oscillation (ENSO) variables than many other TC basins, including the rest of the Australian region basin. The largest correlations with TC frequency were geopotential heights for June–August at 925 hPa over the South Atlantic Ocean (r = −0.65) and for April–June at 700 hPa over North America (−0.64). For TC days the largest correlations are geopotential heights for July–September at 1000 hPa over the South Atlantic Ocean (−0.7) and for April–June at 850 hPa over North America (−0.58). Last, wavelet analyses of annual TC frequencies and TC days reveal periodicities at ENSO and decadal time scales. However, the TC dataset is too short for conclusive evidence of multidecadal periodicities. Given the large correlations revealed by this study, developing and testing of a multivariate seasonal TC prediction scheme has commenced, with lead times up to 6 months.

Constraint of Active Deformation between the African Platform and the Maghrebian Thrust Belt: Current Plate Motion from Permanent GNSS data in Algeria

2021 ◽  
Author(s):  
Mustapha Meghraoui ◽  
Hassen Abdellaoui ◽  
Frédéric Masson
Keyword(s):  
Suture Zone ◽  
Plate Motion ◽  
Thrust Belt ◽  
The South ◽  
Active Deformation ◽  
The North ◽  
Gps Velocities ◽  
Gnss Data ◽  
Tectonic Boundary ◽  
North And South

<p>The kinematic of tectonic motions between the African (Sahara) platform and the Maghrebian thrust belt remained unexplored since the onset of space geodesy. Here, we use data of 6 permanent GNSS stations located north and south of the Atlas thrust belt in Algeria to constrain shortening and transpression at the tectonic boundary. The permanent GPS data and results are obtained from the network in Algeria operative from 2013 to 2019, presented with the results of the REGAT network in Algeria since 2007. The south Atlas suture zone constitutes the limit between African (Sahara) shield domain considered as a stable continental interior and the Sahara Atlas that belong to the Alpine orogeny. The tectonic boundary is marked by a E-W to ENE-WSW, en echelon fold belt system with deformed Plio-Quaternary formations to the North and flat laying Mesozoic and Tertiary sedimentary units south of the suture zone. The GNSS data are processed using Gamit-GlobK and results show tectonic motions with a predominant 5 to 6 mm/yr velocities trending NNW-SSE to NW-SE (westward) in the Sahara Platform. The GPS velocities show uniform trend in the African platform from which we infer 0.5 to 1.0 mm/yr convergence across the south Atlas suture zone. The intraplate convergence is attested by the moderate but permanent seismic activity at the tectonic boundary.</p>

scholarly journals The Neogene lakes on the Balkan land

2012 ◽  
pp. 37-60 ◽  
Author(s):  
Nadezda Krstic ◽  
Ljubinko Savic ◽  
Gordana Jovanovic
Keyword(s):  
Black Sea ◽  
Main Part ◽  
Balkan Peninsula ◽  
The Black Sea ◽  
Geological Data ◽  
The South ◽  
Deep Subsurface ◽  
Upper Miocene ◽  
The North

Palaeogeographic maps of the lacustrine Miocene and Pliocene have been constructed according to all the known geological data. The Lakes of the Balkan Land, depending on the tectonics, migrated due to causes from the deep subsurface. There are several phases of the Miocene lakes: the lowermost Miocene transiting from marine Oligocene, Lower, Middle, Upper Miocene covering, in patches, the main part of the Land. The Pliocene lakes spread mostly to the north of the Balkan Land and covered only its marginal parts. Other lake-like sediments, in fact freshened parts of the Black Sea Kuialnician (Upper Pliocene), stretched along the middle and southern portions of the Balkan Peninsula (to the south of the Balkan Mt.). Subsequently, the Balkan Peninsula was formed.

scholarly journals Origin and distribution of slightly biconical bowls with facetted or channeled rim from the end of bronze and the beginning of iron ages on the Balkan peninsula: Contribution to the study of ethnic and cultural movements in southeast Europe at the end of bronze and the beginning of iron ages

Starinar ◽  
2009 ◽  
pp. 89-108 ◽  
Author(s):  
Aleksandar Bulatovic
Keyword(s):  
Bronze Age ◽  
Iron Age ◽  
Balkan Peninsula ◽  
Type I ◽  
Cultural Groups ◽  
Southeast Europe ◽  
The South ◽  
The Balkans ◽  
The North ◽  
Middle Europe

Slightly biconical shaped bowls, the upper cone (rim and shoulder) of which is decorated with horizontal and slanted facets or slanted channels, as well as semi-globular bowls of inverted rim decorated with horizontal facets or slanted channels are characteristic of the end of Bronze Age and mark the beginning of Iron Age in many cultural groups within the Balkan Peninsula. Problem of their origin, chronology and distribution is present in archaeological literature for a long time. Many authors perceived the significance of this ceramic shape for the chronological, ethnic and cultural interpretation of the Late Bronze, that is, of the Early Iron Ages within the territory of the Balkans. Pottery from the burned layers in Vardina and Vardaroftsa sites in the north of Greece, among which there were bowls with inverted, slanted channeled rim, was designated way back by W. Heurtley as Danubian pottery or Lausitz ware, connecting its origin with the Danube Basin. Anumber of conclusions have been reached upon the study of finds of slightly biconical bowls and bowls of inverted rim, decorated with channels or facets, from several indicative sites from Late Bronze and Early Iron Ages within the Balkan Peninsula and south part of the Middle Europe. It has been stated that the bowls appear first within the southwest Slovakia and northwest Hungary in the Br D period, to spread very fast, already in the Br D/Ha A1 period, from its home territory to the east, to the northeast Hungary and northwest Romania. Namely, this first spreading wave into these territories brought along only variety Ia bowls, which were further distributed to the south, during the Ha A1 period, to the central parts of the Balkan Peninsula and consequently it can be concluded that these bowls are somewhat older than other varieties. In the period Br D - Ha A1, in north Hungary, under the influence of Gava Culture, on one hand, and Caka Culture, on the other, appear also variety IIa bowls (turban dish), distributed to the east with a new migration wave, in the same manner as was the case with the first migration wave, but also to the south, along the Bakonjska Range, to the present day Croatia and Slovenia, where, in the Ha A1/A2 periods, were stated exclusively variety IIa bowls. Representatives of the variety Ia bowls remained in the Pomoravlje region and Juzna Morava Basin, as confirmed by a large number of these bowls and also by other ceramic shapes of that stylistic and typological pattern, prevailing within this region in the Ha A1/A2 periods. First variety IIa bowls (Mediana, Krzince) appear only during the second migration wave coming from the north of the Balkans to the central part of the Balkan Peninsula (Ha A2 period). These bowls, however, are particularly characteristic of Macedonia and lower Povardarje, where variety Ia bowls were not stated at all. The second migration wave representatives, with turban dish bowls (variety IIa), were much more aggressive as witnessed by many burned settlements from that period in the Vranjska-Bujanovacka Valleys and Povardarje. During Ha B-C periods, bowls of both types (particularly variety IIa) became inevitable part of ceramic inventory of nearly all cultural groups in the Balkan Peninsula, which could be explained by the spread of cultural influence of the new stylistic trend, though, however, it could be possible that migrations, which at the time were numerous and of greater or lesser intensity, were one of the spreading causes of this ceramic shape into the east, south and west parts of the Balkan Peninsula in the Ha B period. Representatives of the mentioned migrations, which were carried out in at least two larger migration waves, bringing along bowls to the Balkan Peninsula, are protagonists of historically known migrations from that period, known under names of Doric and Aegean migrations. The assumed direction of these migrations coincides mainly with the distribution direction of bowl types I and II. Migrations spreading the bowl types I and II started in the south part of the Middle Europe, but were initiated by the representatives of the Urnenfelder cultural complex from the Middle Europe, as observed in certain ceramic shapes, stated together with type I bowls and originating from cultures of the Urnenfelder complex, and in numerous metal finds, which were produced in Middle European workshops. It is of interest to point out that bowl movements could be followed up to the northwest shores of the Aegean Sea, but they are not stated in the south Trace and in Troy, thus imposing conclusion that their representatives did not reach Troy. Consequently, their possible participation in destruction of VIIb2 layer settlements is utterly uncertain. The migrations, however, started chain reaction of ethnic movements in the Balkans, causing many ethnic and cultural changes within this territory which will lead to creation of new cultural groups to mark the developed Iron Age. To what extent bowls of this type, particularly variety IIa, left deep trace in the Iron Age Cultures in the central Balkans, is shown in the fact that survivals of this variety remained within these regions even several centuries later, in late phases of the Ha C period (VI/V century BC).

Crustal material recycling induced by subduction erosion and subduction-channel exhumation: A case study of central Tibet (western China) based on P-T-t paths of the eclogite-bearing Baqing metamorphic complex

2020 ◽  
Author(s):  
Xin Jin ◽  
Yu-Xiu Zhang ◽  
Donna L. Whitney ◽  
Kai-Jun Zhang ◽  
Natalie H. Raia ◽  
...  
Keyword(s):  
Mantle Wedge ◽  
Crustal Material ◽  
Metamorphic Complex ◽  
The South ◽  
Subduction Channel ◽  
Crustal Recycling ◽  
The North ◽  
Subduction Erosion ◽  
Proterozoic Basement ◽  
Central Tibet

Subduction and exhumation processes, interacting with each other, play a key role in crustal recycling. Downgoing oceanic lithosphere constitutes the dominant input at subduction margins, but subduction erosion, the removal of crustal material from the overriding plate, may add additional ingredients and complexity to the subduction factory. Different exhumation models have been proposed to explain how subducted materials are exhumed and therefore contribute to crustal recycling, e.g., exhumation up the subduction channel versus diapiric rise through the mantle wedge that overlies the subducted plate. The recently discovered Baqing eclogite-bearing high-pressure metamorphic complex, central Tibet, China, provides an excellent opportunity to decode the exhumation process, the origin of subduction-related magmatism, and the crustal structure of the North Qiangtang block, in addition to elucidating processes of crustal recycling. Pressure-temperature-time (P-T-t) paths and zircon U-Pb ages and trace-element compositions for Baqing high-pressure rocks were used to evaluate exhumation processes and to determine the geochemical and tectonic affinity of the Baqing metamorphic complex. The Baqing metamorphic complex is mainly composed of eclogite, gneiss, and schist. It is located between two geologically distinct terranes—the South Qiangtang block, which has early Paleozoic basement, and the North Qiangtang block, which has Proterozoic basement. In the schist, zircon cores with steep heavy rare earth element (HREE) slopes and oscillatory zoning yielded inherited ages that are similar to detrital zircon ages for the South Qiangtang block schist; in contrast, zircon rims with flat HREE slopes yielded metamorphic ages of 224 Ma that are similar to the metamorphic ages obtained for the Baqing eclogite. In contrast, zircons from the gneiss yielded an upper-intercept age of 1033 ± 32 Ma (interpreted as the crystallization age) and a lower-intercept metamorphic age of 198 ± 4 Ma. Field relations indicate that gneiss and eclogite/amphibolite were exhumed together, so the ∼20 m.y. gap between the gneiss and the metabasite metamorphism may indicate a long exhumation duration. In the region, Proterozoic ages of ca. 1000 Ma are known only from the North Qiangtang block; we thus propose that the Baqing gneiss originated from North Qiangtang block Proterozoic basement, which, along with North Qiangtang block Triassic arc magmatic rocks and the discrepancies between ancient and current arc-trench distances, results in estimates of ∼20−170 km of Triassic subduction erosion. Results of P-T analyses show that most eclogite, amphibolite, and schist shared a similar clockwise P-T path, different from that of the gneiss, which records a higher geothermal gradient. The clockwise P-T trajectory, long exhumation duration, lack of significant heating during exhumation, and the South Qiangtang block affinity of the schist (host rock of the Baqing eclogite) are consistent with subduction-channel exhumation rather than diapiric rise through the mantle wedge. Geochemical similarities between the North Qiangtang block Triassic subduction-related rocks and the Baqing gneiss may signal the involvement of unexhumed Baqing metamorphic complex in the recycling of the Qiangtang crust.

scholarly journals Timing and magnitude of vertical-axis rotations in the eastwards-flanking synorogenic sediments of the South-Pyrenean fold-and-thrust belt. Kinematics and origin of the salient curvature.

2020 ◽  
Author(s):  
Charlotte Peigney ◽  
Elisabet Beamud ◽  
Óscar Gratacós ◽  
Luis Valero ◽  
Ruth Soto ◽  
...  
Keyword(s):  
Foreland Basin ◽  
Structural Data ◽  
Vertical Axis ◽  
Central Unit ◽  
Thrust Belt ◽  
The South ◽  
The North ◽  
South Central ◽  
Fold And Thrust Belt ◽  
Thrust Sheets

<p>The South-Pyrenean fold-and-thrust belt consists of three major thin-skinned thrust sheets (Bóixols, Montsec and Serres Marginals) made up of uppermost Triassic to Oligocene cover rocks emplaced during Late Cretaceous-Oligocene times. In its central part, it forms a major salient (the Pyrenean South-Central Unit) whose geometry is controlled by the areal distribution of the pre-orogenic Upper Triassic and synorogenic Eocene salt décollement layers. Both westwards and eastwards, the salient is fringed by Paleogene synorogenic deposits that are deformed by detachment folds with orientations ranging from N-S to E-W. In the western edge of the salient, the varying trend of the folds is a result of synorogenic vertical axis rotations (VAR) which caused the clockwise rotation of the folds from an initial predominant E-W trend to the current NW-SE to NNW-SSE trend. The salient, at least on its western part, developed from a progressive curve originated from divergent thrust transport directions and distributed shortening.</p><p>The aim of our study is to get a better understanding of the whole salient, by studying the kinematics of the deformation on the most frontal part of its eastern edge. Here, some sparse anticlockwise rotations have been reported but their origin and their possible relationship with the distribution of the salt décollements has not yet been addressed. For this purpose, 78 paleomagnetic sites have been sampled on the synorogenic upper Eocene-Oligocene materials of the NE Ebro foreland Basin, in the Artesa de Segre area, focusing on the limbs of oblique salt-cored anticlines (Ponts, Vilanova de l’Aguda, Cardona) which are detached above the synorogenic Eocene-Oligocene evaporites of the Cardona and the Barbastro formations. VAR analyses principally show anticlockwise rotations similar to those previously identified to the North in the Oliana Anticline, although a small number of clockwise rotations were also detected.</p><p>In addition to the VAR analysis, a magnetostratigraphic study of the Eocene-Oligocene continental materials of the northern limb of the Sanaüja Anticline has been conducted in order to constrain the age of these rotations from stratigraphic correlations. The demagnetization of 104 samples from a ca. 1100 m thick magnetostratigraphic section shows Priabonian to Rupelian ages for this succession. The integration of our results on timing, direction and magnitude of foreland VAR with previous paleomagnetic and structural data from both the western and eastern boundaries of the frontal thrust of the Pyrenean South-Central Unit will allow the understanding of the kinematics of the thrust salient as a whole.</p>

scholarly journals Particular ceramic forms in the central Balkan and northern shores of the Aegean sea in the late bronze age

Starinar ◽  
2011 ◽  
pp. 121-140 ◽  
Author(s):  
Aleksandar Bulatovic
Keyword(s):  
Bronze Age ◽  
Aegean Sea ◽  
Balkan Peninsula ◽  
Late Bronze Age ◽  
Cultural Group ◽  
Cultural Groups ◽  
The South ◽  
14Th Century ◽  
The North ◽  
15Th Century

This paper deals with the appearance and development of particular ceramic forms that were prevalent on the wider territory from the lower Danube to the northern shores of the Aegean sea during the middle and Late Bronze Age. These forms relate to globular beakers, pear shaped vessels with everted rims with arch shaped handles, cups with handles with plastic applications on their upper surface, etc. Particular attention is devoted to the phenomenon of globular beakers of the LBA in the valleys of Varder, Mesta and Struma rivers. All information collected primarily through analysis of stylistic-typological characteristics of ceramics of the middle and Late Bronze Age - that took into account ritual burials, layout of settlements, trade routes and climactic conditions during that period - points to population movements from the north to the south already by the LBA, i.e. in 15th century BC. These movements contributed to the creation of particular cultural groups in the LBA in the central Balkans, such as the Brnjica cultural group. However, these movements cannot be clearly linked to the so-called Aegean Migration, and for this reason their character and chronology are subject to debate. Ultimately it can be concluded that beakers of the Zimnicea -Cherkovna-Plovdiv type appeared in the late Bronze Age in the Vlasine depression and the Danube valley through the evolution of beaker forms of cultural groups of earlier periods. Almost contemporaneously, during LBA, a variant of this ceramic form, richly ornamented (mostly with spirals) and similar in manner to the cultural group Dubovac-Zuto Brdo-Grla Mare- Krna, appeared in the LBA culture in northern Greece. Clearly this stylistic mannerism, with spirals as characteristic elements, spread relatively quickly through successive migrations in the period of 15th-14th century BC, toward the south of the Balkan Peninsula, thus covering the wider territory from the southern tip of the Carpathian mountains down to the northern shores of the Aegean Sea. Participants in those migrations are in fact representatives of cultural groups that were created in the northern Balkan Peninsula during the 16th and 15th centuries BC through the breakdown of Vatic culture. As the result of pressures from the north and north-west they headed south, contributing to the creation and development of cultural groups on the territory of the central Balkans. The final destination of the migrations were the valleys of the Mesta, Struma and Vardar rivers where, starting in the 15th century BC, a noticeable foreign cultural influence can be felt that became most pronounced during 14th century BC.

scholarly journals Comparing Reanalyses Using Analysis Increment Statistics

2008 ◽  
Vol 9 (6) ◽  
pp. 1535-1545 ◽  
Author(s):  
Jean Fitzmaurice ◽  
Rafael L. Bras
Keyword(s):  
Standard Deviation ◽  
North American ◽  
Meridional Wind ◽  
Department Of Energy ◽  
Specific Humidity ◽  
South American ◽  
The South ◽  
The North ◽  
Uncertainty Estimates ◽  
Global Reanalysis

Abstract Reanalysis data are an important source of information for hydrometeorology applications, which use data assimilation to combine an imperfect atmospheric model with uncertain observations. However, uncertainty estimates are not normally provided with reanalyses. The model “first guess” (6-h forecast) is sometimes saved along with reanalysis estimates, which allows the calculation of the analysis increment (AI), defined as the analysis minus the model first guess. Analysis increment statistics could provide a quantitative index for comparing models in regions with sufficient observations. Monthly analysis increment statistics for the NCEP–NCAR Global Reanalysis 1 (NCEP-R1) and the NCEP/Department of Energy Global Reanalysis 2 (NCEP-R2) are computed for a North American and South American location for zonal and meridional wind and specific humidity at three atmospheric levels for 1998–2001. NCEP-R2 specific humidity was found to have a smaller mean monthly standard deviation of the analysis increment than NCEP-R1 at the North American location at the 300-mb level. The NCEP-R2 specific humidity monthly standard deviation at the South American location is much larger than NCEP-R1 for September–November 1998, which may be related to the transition to La Niña. For both zonal and meridional wind, the monthly AI standard deviations are similar for NCEP-R1 and NCEP-R2 at all atmospheric levels for the North American location. The South American location exhibits similar behavior for the wind AI statistics as for specific humidity: NCEP-R2 has a much larger monthly standard deviation of the AI for September–November 1998. The analysis increment statistics could be one method for quantitatively comparing reanalyses. First guess information should be available to the user in reanalysis archives.

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