scholarly journals Wind profiler observations on orographic effects of typhoon wind structure modification over Taiwan (120.38° E, 22.6° N)

2010 ◽  
Vol 28 (1) ◽  
pp. 141-147 ◽  
Author(s):  
C. J. Pan ◽  
K. Krishna Reddy ◽  
H. C. Lai ◽  
S. S. Yang ◽  
C. J. Wong
Keyword(s):  
Mountain Range ◽  
Wind Profiler ◽  
Structure Modification ◽  
Observation Site ◽  
Orographic Effects ◽  
Tropical Depression ◽  
The North ◽  
Wind Structure ◽  
New Finding ◽  
Upper Level

Abstract. The interaction of the storm circulation with the Central Mountain Range (CMR) of Taiwan is studied with a wind profiler located at the leeside during the invasions of two (Kaemi (200605) and Bopha (200609)) typhoons. The moderate typhoon Kaemi upgraded from a tropical depression on 21 July 2006. It then was made landfall at 15:45 UTC on 24 July 2006 near Cheng-Kung. The weak typhoon Bopha formed at about 12:00 UTC on 5 August 2006 and also landed near Cheng-Kung at around 19:20 UTC on 8 August. A new finding from both typhoons is the vortex splitting into upper and lower parts with the two typhoons that have passed the observation site nearly. For the typhoon Kaemi, demarcation height of the upper-level vortex and lower level is at 2.8 km and passed the site about 3 h earlier than the low-level one. For the typhoon Bopha, the center of the lower-level vortex at 3.5 km locates to the north of the upper-level one at 5.2 km. The re-organization of the split vortexes is found in typhoon Kaemi but not for typhoon Bopha.

Middle Miocene rise of the Greater Himalaya establishing a new orographic barrier

2021 ◽  
Author(s):  
Rasmus Thiede ◽  
Dirk Scherler ◽  
Christoph Glotzbach
Keyword(s):  
Middle Miocene ◽  
Shear Zones ◽  
Tectonic Deformation ◽  
Surface Erosion ◽  
Mountain Range ◽  
Close Coupling ◽  
The North ◽  
New Finding ◽  
Exhumation Rates ◽  
Greater Himalaya

<p>The Himalaya is the highest and steepest mountain range on Earth and an efficient north-south barrier for moisture-bearing winds. The close coupling of changes in topography, erosion rates, and uplift has previously been interpreted as an expression of a climatic control on tectonic deformation. Here, we present 17 new zircon U/Th-He (ZHe) bedrock-cooling ages from the Sutlej Valley that – together with >100 previously published mica <sup>40</sup>Ar/<sup>39</sup>Ar, zircon and apatite fission track ages – allow us to constrain the crustal cooling and exhumation history over the last ~20 Myr. Using 1D-thermal modeling, we observe a rapid decrease in exhumation rates from >1 km/Myr to <0.5 km/Myr that initiated at ~17-15 Ma across the entire Greater and Tethyan Himalaya, as far north as the north-Himalayan Leo Pargil gneiss dome. This decrease is recognized both in the hanging and footwall of major Miocene shear zones and suggests that cooling is associated to surface erosion rather than to tectonic unroofing. We explain the middle Miocene deceleration of exhumation with major reorganization of Himalayan deformation and the onset of the growth of the Lesser Himalayan duplex. This resulted in accelerated uplift of the Greater Himalaya above a mid-crustal ramp, and thus forming a new efficient orographic barrier. The period of slow exhumation in the upper Sutlej Valley coincides with a period of internal drainage in the south-Tibetan Zada Basin further upstream, which we interpret to be a consequence of tectonic damming of the upper Sutlej River. External drainage of the Zada Basin was re-established ~1 Ma, when we observe exhumation rates in the upper Sutlej Valley to accelerate again. Our new finding document that the location of tectonic deformation processes control the first order spatial pattern of both climatic zones and erosion across the orogen.</p>

scholarly journals The Secondary Low and Heavy Rainfall Associated with Typhoon Mindulle (2004)

2008 ◽  
Vol 136 (4) ◽  
pp. 1260-1283 ◽  
Author(s):  
Cheng-Shang Lee ◽  
Yi-Chin Liu ◽  
Fang-Ching Chien
Keyword(s):  
Heavy Rainfall ◽  
Numerical Study ◽  
North Coast ◽  
Mountain Range ◽  
Mountain Area ◽  
The North ◽  
Main Circulation ◽  
Upper Level ◽  
The Taiwan Strait ◽  
Strong Vorticity

Abstract This paper presents an observational and numerical study of Typhoon Mindulle (2004) as it affected Taiwan. Mindulle made landfall on the east coast of Taiwan at 1500 UTC 1 July 2004, and after 13 h, it exited Taiwan from the north coast. Severe rainfall (with a maximum amount of 787 mm) occurred over central-southwestern Taiwan on 2 July 2004. During the landfall of Mindulle’s main circulation, a secondary low formed over the Taiwan Strait. However, the secondary low, after it developed significantly (vorticity exceeded 5 × 10−4 s−1 over a 30-km radius), did not replace the original center as was observed in many other storms. Instead, it moved inland and dissipated after the original center redeveloped near the north coast of Taiwan. In this study, the evolution of the secondary low, the redevelopment of the primary center, and the processes leading to the severe rainfall were examined. Results showed that the processes leading to the formation and the development of the secondary low were similar to those described in previous studies. These processes include the leeside subsidence warming, the horizontal transport of vorticity around the northern tip of the Central Mountain Range (CMR), and the overmountain upper-level vorticity remnant. However, because of the northward track, Mindulle preserved some strong vorticity on the eastern slope of the CMR. This strong vorticity remnant was steered northward over the ocean offshore from the north coast where the redevelopment of the primary center occurred. This “quasi-continuous track” of Mindulle has not been documented in previous studies. The vortex interaction between the redeveloped primary center and the secondary low resulted in the northeastward movement of the secondary low, which then dissipated after making landfall. Analyses also showed that even though heavy rainfall would occur over the mountain area when only the southwesterly flow prevailed, as on 3 July 2004, Typhoon Mindulle and the secondary low provided extra convergence that resulted in the west–east-oriented convective bands. These convective bands and the orographic lifting of the circulation associated with the secondary low resulted in the heavy rainfall over the central-western plains area.

Spurious Grid-Scale Precipitation in the North American Regional Reanalysis

2007 ◽  
Vol 135 (6) ◽  
pp. 2168-2184 ◽  
Author(s):  
Gregory L. West ◽  
W. James Steenburgh ◽  
William Y. Y. Cheng
Keyword(s):  
North American ◽  
Prediction Models ◽  
Weather Prediction ◽  
Regional Climate ◽  
Potential Temperature ◽  
Climate Data ◽  
The North ◽  
North American Regional Reanalysis ◽  
Upper Level ◽  
Regional Reanalysis

Abstract Spurious grid-scale precipitation (SGSP) occurs in many mesoscale numerical weather prediction models when the simulated atmosphere becomes convectively unstable and the convective parameterization fails to relieve the instability. Case studies presented in this paper illustrate that SGSP events are also found in the North American Regional Reanalysis (NARR) and are accompanied by excessive maxima in grid-scale precipitation, vertical velocity, moisture variables (e.g., relative humidity and precipitable water), mid- and upper-level equivalent potential temperature, and mid- and upper-level absolute vorticity. SGSP events in environments favorable for high-based convection can also feature low-level cold pools and sea level pressure maxima. Prior to 2003, retrospectively generated NARR analyses feature an average of approximately 370 SGSP events annually. Beginning in 2003, however, NARR analyses are generated in near–real time by the Regional Climate Data Assimilation System (R-CDAS), which is identical to the retrospective NARR analysis system except for the input precipitation and ice cover datasets. Analyses produced by the R-CDAS feature a substantially larger number of SGSP events with more than 4000 occurring in the original 2003 analyses. An oceanic precipitation data processing error, which resulted in a reprocessing of NARR analyses from 2003 to 2005, only partially explains this increase since the reprocessed analyses still produce approximately 2000 SGSP events annually. These results suggest that many NARR SGSP events are not produced by shortcomings in the underlying Eta Model, but by the specification of anomalous latent heating when there is a strong mismatch between modeled and assimilated precipitation. NARR users should ensure that they are using the reprocessed NARR analyses from 2003 to 2005 and consider the possible influence of SGSP on their findings, particularly after the transition to the R-CDAS.

scholarly journals Barotropic Regeneration of Upper-Level Synoptic Disturbances in Different Configurations of the Zonal Weather Regime

2008 ◽  
Vol 65 (10) ◽  
pp. 3159-3178 ◽  
Author(s):  
Gwendal Rivière
Keyword(s):  
Large Scale ◽  
Deformation Field ◽  
Regeneration Process ◽  
Barotropic Model ◽  
Weather Regime ◽  
The North ◽  
The Difference ◽  
Upper Level ◽  
Composite Maps ◽  
Large Scale Flow

Barotropic dynamics of upper-tropospheric midlatitude disturbances evolving in different configurations of the zonal weather regime (i.e., in different zonal-like large-scale flows) were studied using observational analyses and barotropic model experiments. The contraction stage of upper-level disturbances that follows their elongation stage leads to an increase of eddy kinetic energy that is called the barotropic regeneration process in this text. This barotropic mechanism is studied through notions of barotropic critical regions (BtCRs) and effective deformation that have been introduced in a previous paper. The effective deformation field is equal to the difference between the square of the large-scale deformation magnitude and the square of the large-scale vorticity. Regions where the effective deformation is positive correspond to regions where the large-scale flow tends to strongly stretch synoptic disturbances. A BtCR is an area separating two large-scale regions of positive effective deformation, one located upstream and on the south side of the jet and the other downstream and on the north side. Such a region presents a discontinuity in the orientation of the dilatation axes and is a potential area where the barotropic regeneration process may occur. Winter days presenting a zonal weather regime in the 40-yr ECMWF Re-Analysis dataset are decomposed, via a partitioning algorithm, into different configurations of the effective deformation field at 300 hPa. A six-cluster partition is obtained. Composite maps of the barotropic generation rate for each cluster exhibit a succession of negative and positive values on both sides of the BtCRs. It confirms statistically that the barotropic regeneration mechanism occurs preferentially about BtCRs. Numerical experiments using a forced barotropic model on the sphere are performed. Each experiment consists of adding a synoptic-scale perturbation to one of the zonal-like jet configurations found in observations, which is kept fixed with time. The combined effects of the effective deformation and nonlinearities are shown to be crucial to reproduce the barotropic regeneration process about BtCRs.

Trends and Variability of North American Cool-Season Extratropical Cyclones: 1979–2019

2021 ◽  
Author(s):  
Robert Fritzen ◽  
Victoria Lang ◽  
Vittorio A. Gensini
Keyword(s):  
North American ◽  
Research Question ◽  
Weather Conditions ◽  
Extratropical Cyclones ◽  
Mountain Range ◽  
Cool Season ◽  
The North ◽  
Primary Driver ◽  
Regional Reanalysis ◽  
Log Linear

AbstractExtratropical cyclones are the primary driver of sensible weather conditions across the mid-latitudes of North America, often generating various types of precipitation, gusty non-convective winds, and severe convective storms throughout portions of the annual cycle. Given ongoing modifications of the zonal atmospheric thermal gradient due to anthropogenic forcing, analyzing the historical characteristics of these systems presents an important research question. Using the North American Regional Reanalysis, boreal cool-season (October–April) extratropical cyclones for the period 1979–2019 were identified, tracked, and classified based on their genesis location. Additionally, bomb cyclones—extratropical cyclones that recorded a latitude normalized pressure fall of 24 hPa in 24-hr—were identified and stratified for additional analysis. Cyclone lifespan across the domain exhibits a log-linear relationship, with 99% of all cyclones tracked lasting less than 8 days. On average, ≈ 270 cyclones were tracked across the analysis domain per year, with an average of ≈ 18 year−1 being classified as bomb cyclones. The average number of cyclones in the analysis domain has decreased in the last 20 years from 290 year−1 during the period 1979–1999 to 250 year−1 during the period 2000–2019. Spatially, decreasing trends in the frequency of cyclone track counts were noted across a majority of the analysis domain, with the most significant decreases found in Canada’s Northwest Territories, Colorado, and east of the Graah mountain range. No significant interannual or spatial trends were noted with bomb cyclone frequency.

The Invasion of Plague in Early Modern Italy

2019 ◽  
pp. 23-50
Author(s):  
John Henderson
Keyword(s):  
Early Modern ◽  
Preventive Measures ◽  
Northern Italy ◽  
Reggio Emilia ◽  
Health Board ◽  
Mountain Range ◽  
Physical Barrier ◽  
The North ◽  
Early Modern Italy ◽  
The Dead

This chapter discusses the origins and spread of plague in northern Italy. Plague arrived in Italy in 1629 with French and German troops. It is no accident that the initial cases of plague identified in October of 1629 were first in Piedmont in the Val di Susa, west of Turin and near the border with France, and secondly in the Valtellina in Lombardy, subsequently travelling to Lake Como to the north of Milan. Other cities in northern Italy soon became infected and on May 6, 1630, the authorities as far south as Bologna announced the official outbreak of plague. Judging by the rapidity with which plague spread between these northern urban centres, one would have expected the epidemic to have arrived in Tuscany by early May, given that Bologna is only 65 miles north of Florence, but it was delayed by both natural and man-made factors. Tuscany is separated from Reggio-Emilia by the Apennine mountain range, which provided a physical barrier and facilitated the control of traffic coming from the north. The chapter then traces the preventive measures adopted by the health board as the plague approached Tuscany, including cordons sanitaires along frontiers, the removal of the sick to quarantine centres, and the rapid burial of the dead.

scholarly journals Geological evolution of the Chalk Group in the northern Dutch North Sea: inversion, sedimentation and redeposition

2018 ◽  
Vol 156 (07) ◽  
pp. 1265-1284
Author(s):  
EVA VAN DER VOET ◽  
LEONORA HEIJNEN ◽  
JOHN J. G. REIJMER
Keyword(s):  
North Sea ◽  
Late Cretaceous ◽  
Seismic Survey ◽  
Structural Elements ◽  
The North ◽  
Show Evidence ◽  
New Finding ◽  
The North Sea ◽  
Thickness Variations ◽  
Well Data

AbstractIn contrast to the Norwegian and Danish sectors, where significant hydrocarbon reserves were found in chalk reservoirs, limited studies exist analysing the chalk evolution in the Dutch part of the North Sea. To provide a better understanding of this evolution, a tectono-sedimentary study of the Late Cretaceous to Early Palaeogene Chalk Group in the northern Dutch North Sea was performed, facilitated by a relatively new 3D seismic survey. Integrating seismic and biostratigraphic well data, seven chronostratigraphic units were mapped, allowing a reconstruction of intra-chalk geological events.The southwestward thickening of the Turonian sequence is interpreted to result from tilting, and the absence of Coniacian and Santonian sediments in the western part of the study area is probably the result of non-deposition. Seismic truncations show evidence of a widespread inversion phase, the timing of which differs between the structural elements. It started at the end of the Campanian followed by a second pulse during the Maastrichtian, a new finding not reported before. After subsidence during the Maastrichtian and Danian, renewed inversion and erosion occurred at the end of the Danian. Halokinesis processes resulted in thickness variations of chalk units of different ages.In summary, variations in sedimentation patterns in the northern Dutch North Sea relate to the Sub-Hercynian inversion phase during the Campanian and Maastrichtian, the Laramide inversion phase at the end of the Danian, and halokinesis processes. Additionally, the Late Cretaceous sea floor was characterized by erosion through contour bottom currents at different scales and resedimentation by slope failures.

scholarly journals Passive imaging of collisional orogens: a review of a decade of geophysical studies in the Pyrénées

2022 ◽  
Vol 193 ◽  
pp. 1
Author(s):  
Sébastien Chevrot ◽  
Matthieu Sylvander ◽  
Antonio Villaseñor ◽  
Jordi Díaz ◽  
Laurent Stehly ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Mountain Range ◽  
Seismic Signals ◽  
Passive Imaging ◽  
Tomographic Images ◽  
Bouguer Anomalies ◽  
The North ◽  
Eastern Pyrenees ◽  
Collisional Orogens ◽  
Central Pyrenees

This contribution reviews the challenges of imaging collisional orogens, focusing on the example of the Pyrenean domain. Indeed, important progresses have been accomplished regarding our understanding of the architecture of this mountain range over the last decades, thanks to the development of innovative passive imaging techniques, relying on a more thorough exploitation of the information in seismic signals, as well as new seismic acquisitions. New tomographic images provide evidence for continental subduction of Iberian crust beneath the western and central Pyrénées, but not beneath the eastern Pyrénées. Relics of a Cretaceous hyper-extended and segmented rift are found within the North Pyrenean Zone, where the imaged crust is thinner (10–25 km). This zone of thinned crust coincides with a band of positive Bouguer anomalies that is absent in the Eastern Pyrénées. Overall, the new tomographic images provide further support to the idea that the Pyrénées result from the inversion of hyperextended segmented rift systems.

scholarly journals The Ancient City of Babylon

2020 ◽  
Vol 2 (40) ◽  
pp. 617-656
Author(s):  
Mohammed S. Mahan ◽  
Ghassan Muslim Hamza
Keyword(s):  
Historical Development ◽  
Large Scale ◽  
Building Materials ◽  
Large City ◽  
Aerial Photos ◽  
The North ◽  
City Gates ◽  
Upper Level ◽  
Materials Used ◽  
The City

       Babylon during Nebuchadnezzar II (604-562 BC) was a great city. It had been a large city since Old Babylonian times, but Nebuchadnezzar’s expansion of the city and large-scale rebuilding of important buildings with good baked brick instead of the traditional unbaked mudbrick created something exceptional. Babylon now was larger than Nineveh had been and larger than any of the cities in the known world. The political and economic base for this development was of course that it was the centre of the Neo-Babylonian empire created by Nebuchadnezzar’s father Nabopolassar (625–605 BC) and succeeding the Neo Assyrian empire as the main political entity in the Middle East.         An attempt for the first time to bring together the main results of the German excavations in Babylon with the main results from the Iraqi excavations there and thereby make use of the available cuneiform documentation and a selected use of the best of the classical tradition. With the help of a GIS software (QGIS) and a BIM program (ArchiCAD) the use of satellite images and aerial photos combined with inspection on the site, the historical development of the site has been studied and a digital research model of Babylon for different periods of the city’s history has been created.          Only main buildings and constructions have been considered and placed in the appropriate historical and archaeological context. Part 1 includes some information about the historical development of buildings and nature in Babylon, the rivers and groundwater in Baybylon, as well as basics about the building materials used in Babylon. Part 2 discuss the city walls and city gates, introductory matters about the history, excavation and other documentations of the walls and gates. The chapter also includes presentation of the walls and gates during Nabopolassar followed by a detailed discussion of the walls and gates during Nebuchadnezzar. The Ištar gate and the area around it with the different levels and the upper level glazed decoration have been treated separately. Detailed interpretations about the palaces, development of the main traditional South Palace and the new constructed North are discussed in part 3. Reasonable suggestions for the Hanging Gardens in the North Palace have be provided.          The temples are discussed in part 4 detailing the Marduk temple and the zikkurrat. The historical development of the four temples reconstructed on the site in Babylon on their old foundations, i.e. Nabû, Ištar, Ašratum, and Ninmaḫ temples, is discussed with indication which levels have been used for the reconstructions. The historical development of the other excavated temples, i.e. the Ninurta and Išḫara temples, are discussed in a similar way. Attention will be paid to the remains of wall decorations in the temples.  

scholarly journals Observation of Shaheen Falcon Falco peregrinus peregrinator (Aves: Falconiformes: Falconidae) in the Nilgiris, Tamil Nadu, India

2017 ◽  
Vol 9 (10) ◽  
pp. 10850
Author(s):  
Arockianathan Samson ◽  
Balasundaram Ramakrishnan ◽  
Palanisamy Santhoshkumar ◽  
Sivaraj Karthick
Keyword(s):  
Tamil Nadu ◽  
Mountain Range ◽  
Falco Peregrinus ◽  
The North ◽  
The Nilgiris

A total of 45 sightings of 57 individual Shaheen Falcons were recorded from 2014–2016 from different locations in the Nilgiris mountain range, and eight nests were located on separate rocky cliffs.  Most of the nests (n= 6) were situated at elevations ranging from 1500–2500 m and 45% of the nests were located on the north facing exposures.

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