scholarly journals Eulerian and Lagrangian Comparison of Primary and Secondary Wind Jets in the Tokar Gap Region

2020 ◽  
Author(s):  
Larry Pratt ◽  
E. Jason Albright ◽  
Irina Rypina ◽  
Houshuo Jiang
Keyword(s):  
Saudi Arabia ◽  
Wind Speed ◽  
Red Sea ◽  
Wrf Model ◽  
High Elevation ◽  
Strong Wind ◽  
Structure And Dynamics ◽  
Wind Event ◽  
Bernoulli Function ◽  
Horizontal Momentum

The Lagrangian and Eulerian structure and dynamics of a strong wind event in the Tokar Gap region are described using a WRF model hindcast for 2008. Winds in the Tokar Gap reach 25 m s-1 and remain coherent as a jet far out over the Red Sea, whereas equally strong wind jets occurring in neighboring gaps are attenuated abruptly by a jump-like hydraulic transition that occur just offshore of the Sudan coast. The transition is made possible by the supercritical nature of the jets, which are fed by air that spills down from passes at relatively high elevation. By contrast, the spilling flow in the ravine-like Tokar Gap does not become substantially supercritical and therefore does not undergo a jump, and also carries more total horizontal momentum. The Tokar Wind Jet carries some air parcels across the Red Sea and into Saudi Arabia, whereas air parcel trajectories in the neighboring jets ascend as they cross through the jumps, then veer sharply to the southeast and do not cross the Red Sea. The mountain parameter Nh/U is estimated to lie in the rage 1.0-4.0 for the general region, a result roughly consistent with a primary gap jet having a long extension, and supercritical jets spilling down from higher elevation passes. The strong event is marked by the formation of a cyclonic cell near the upstream entrance to the Tokar Gap, a feature absent from the more moderate events that occur throughout the summer. The cell contains descending air parcels that are fed into the primary and secondary jets. An analysis of the Bernoulli function along air parcel trajectories reveals an approximate balance between the loss of potential energy and gain of internal energy and pressure, with surprisingly little contribution from kinetic energy, along the path of the descending flow. All jets attain the critical wind speed nominally required to loft dust into the atmosphere, though only the Tokar Gap has a broad, delta region with plentiful deposits of silt.

scholarly journals Eulerian and Lagrangian Comparison of Wind Jets in the Tokar Gap Region

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 193
Author(s):  
Larry J. Pratt ◽  
E. Jason Albright ◽  
Irina Rypina ◽  
Houshuo Jiang
Keyword(s):  
Red Sea ◽  
Wrf Model ◽  
High Elevation ◽  
Dust Storms ◽  
Weather Research And Forecasting ◽  
Strong Wind ◽  
Wind Event ◽  
Bernoulli Function ◽  
Horizontal Momentum ◽  
Supercritical Flows

The Lagrangian and Eulerian structure and dynamics of a strong wind event in the Tokar Gap region are described using a Weather Research and Forecasting (WRF) model hindcast for 2008. Winds in the Tokar Gap reach 25 m s−1 and remain coherent as a jet far out over the Red Sea, whereas equally strong wind jets occurring in neighboring gaps are attenuated abruptly by jump-like hydraulic transitions that occur just offshore of the Sudan coast. The transition is made possible by the supercritical nature of the jets, which are fed by air that spills down from passes at relatively high elevation. By contrast, the spilling flow in the ravine-like Tokar Gap does not become substantially supercritical and therefore does not undergo a jump, and also carries more total horizontal momentum. The Tokar Wind Jet carries some air parcels across the Red Sea and into Saudi Arabia, whereas air parcel trajectories in the neighboring jets ascend as they cross through the jumps, then veer sharply to the southeast and do not cross the Red Sea. The mountain parameter Nh/U is estimated to lie in the range of 1.0–4.0 for the general region, a result roughly consistent with a gap jet having a long extension, and supercritical flows spilling down from higher elevation passes. The strong event is marked by the formation of a feature with a vertical cellular structure in the upstream entrance region of the Tokar Gap, a feature absent from the more moderate events that occur throughout the summer. The cell contains descending air parcels that are fed into the Tokar Gap and one of the neighboring gaps. An analysis of the Bernoulli function along air parcel trajectories reveals an approximate balance between the loss of potential energy and gain of internal energy and pressure, with surprisingly little contribution from kinetic energy, along the path of the descending flow. The winds in all gaps attain the critical wind speed nominally required to loft dust into the atmosphere, though only the Tokar Gap has a broad, silty delta region capable of supplying particulate matter for dust storms.

Topographical effect of the Antarctic Peninsula on a strong wind event

2021 ◽  
pp. 1-11
Author(s):  
Hataek Kwon ◽  
Seong-Joong Kim ◽  
Sang-Woo Kim ◽  
Sinu Kim
Keyword(s):  
Wind Speed ◽  
Antarctic Peninsula ◽  
Critical Role ◽  
Wrf Model ◽  
Strong Discontinuity ◽  
Strong Wind ◽  
Easterly Wind ◽  
Wind Event ◽  
Topographical Effect ◽  
The Antarctic

Abstract The topographical effect on a strong wind event that occurred on 7 January 2013 at King Sejong Station (KSJ), Antarctica, was investigated using the Polar Weather Research and Forecasting (WRF) model. Numerical experiments applying three different terrain heights of the Antarctic Peninsula (AP) were performed to quantitatively estimate the topographical effect on the selected strong wind event. The experiment employing original AP topography successfully represented the observed features in the strong wind event, both in terms of peak wind speed (by ~94%; ~19.7 m/s) and abrupt transitions of wind speed. In contrast, the experiment with a flattened terrain height significantly underestimated the peak wind speeds (by ~51%; ~10.4 m/s) of the observations. An absence of AP topography failed to simulate both a strong discontinuity of sea-level pressure fields around the east coast of the AP and a strong south-easterly wind over the AP. As a result, the observed downslope windstorm, driven by a flow overriding a barrier, was not formed at the western side of the AP, resulting in no further enhancement of the wind at KSJ. This result demonstrates that the topography of the AP played a critical role in driving the strong wind event at KSJ on 7 January 2013, accounting for ~50% of the total wind speed.

scholarly journals Calibration of the depth invariant algorithm to monitor the tidal action of Rabigh City at the Red Sea Coast, Saudi Arabia

2020 ◽  
Vol 12 (1) ◽  
pp. 1666-1678
Author(s):  
Mohammed H. Aljahdali ◽  
Mohamed Elhag
Keyword(s):  
Remote Sensing ◽  
Saudi Arabia ◽  
Wind Speed ◽  
Red Sea ◽  
Remote Sensing Data ◽  
Microwave Remote Sensing ◽  
Optical Data ◽  
Mean Values ◽  
Sensing Data ◽  
The Mean

AbstractRabigh is a thriving coastal city located at the eastern bank of the Red Sea, Saudi Arabia. The city has suffered from shoreline destruction because of the invasive tidal action powered principally by the wind speed and direction over shallow waters. This study was carried out to calibrate the water column depth in the vicinity of Rabigh. Optical and microwave remote sensing data from the European Space Agency were collected over 2 years (2017–2018) along with the analog daily monitoring of tidal data collected from the marine station of Rabigh. Depth invariant index (DII) was implemented utilizing the optical data, while the Wind Field Estimation algorithm was implemented utilizing the microwave data. The findings of the current research emphasis on the oscillation behavior of the depth invariant mean values and the mean astronomical tides resulted in R2 of 0.75 and 0.79, respectively. Robust linear regression was established between the astronomical tide and the mean values of the normalized DII (R2 = 0.81). The findings also indicated that January had the strongest wind speed solidly correlated with the depth invariant values (R2 = 0.92). Therefore, decision-makers can depend on remote sensing data as an efficient tool to monitor natural phenomena and also to regulate human activities in fragile ecosystems.

scholarly journals On the Effect of Red Sea and Topography on Rainfall over Saudi Arabia: Case Study

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 669
Author(s):  
Al-Mutairi ◽  
Abdel Basset ◽  
Morsy ◽  
Abdeldym
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Sea Water ◽  
Wrf Model ◽  
Temporal Distribution ◽  
Surface Fluxes ◽  
Sensitivity Experiment ◽  
Low Level ◽  
Spatio Temporal ◽  
The Impact

This paper aimed to investigate the impact of Red Sea topography and water on the development and rainfall of a case of cyclogenesis occurs over Saudi Arabia during the period 16–18 November 2015 using the Weather Research and Forecasting (WRF) model. The WRF Control Run (WRF-CR) experiment was performed with presence of actual topography and surface water of the Red Sea, while the other three sensitivity experiments were carried out without (i) Red Sea Topography (NRST), (ii) Red Sea Water (NRSW), and (iii) Red Sea Topography and Water (NRSTW). The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission (TRMM) rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results demonstrate that rainfall intensity and spatio-temporal distribution significantly changes through each sensitivity experiment compared to the WRF-CR, where the significant variation was found in the NRST experiment. The absence of topography (NRST) leads to formation of strong convergence area over the middle of Red Sea which enhanced uplift motion that further strengthened the low-level jet over Red Sea and the surrounding regions, which enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the cyclonic system. The absence of Red Sea water (NRSW) changed rainfall spatial distribution and reduced its amount by about 30–40% due to affecting of the dynamics of the upward motion and moisture gradient, suggesting that surface fluxes play an important role in regulating the low-level moist air convergence prior to convection initiation and development.

scholarly journals Atmospheric forcing of sea ice anomalies in the Ross Sea Polynya region

2016 ◽  
Author(s):  
Ethan R. Dale ◽  
Adrian J. McDonald ◽  
Jack H.J. Coggins ◽  
Wolfgang Rack
Keyword(s):  
Wind Speed ◽  
Sea Ice ◽  
Ross Sea ◽  
Strong Wind ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Wind Speeds ◽  
Wind Event ◽  
Wind Events ◽  
Ice Production

Abstract. Despite warming trends in global temperatures, sea ice extent in the Southern Hemisphere has shown an increasing trend over recent decades. Wind-driven sea ice export from coastal polynyas is an important source of sea ice production. Areas of major polynyas in the Ross Sea, the region with largest increase in sea ice extent, have been suggested to produce a vast amount of the sea ice in the region. We investigate the impacts of strong wind events on the Ross Sea Polynyas and its sea ice concentration and possible consequences on sea ice production. We utilise Bootstrap sea ice concentration (SIC) measurements derived from satellite based, Special Sensor Microwave Imager (SSM/I) brightness temperatures. We compared these with surface winds and temperatures from automatic weather stations (AWS) of the University of Wisconsin-Madison Antarctic Meteorology Program. Our analysis focusses on the austral winter period defined as 1st April to 1st November in this study. Daily data were used to classified into characteristic regimes based on the percentiles of wind speed. For each regime, a composite of SIC anomaly was formed for the Ross Sea region. We found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea Polynya (RSP). Conversely we found negative SIC anomalies in this area during persistent strong winds. By analysing sea ice motion vectors derived from SSM/I and SSMIS brightness temperatures, we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events. These anomalies persist for several days after the strong wind event. Strong, negative correlations are found between SIC and AWS wind speed within the RSP indicating that strong winds cause significant advection of sea ice in the region. We were able to recreate these correlations using co-located ERA-Interim wind speeds. However when only days of a certain percentile based wind speed classification were used, the cross correlation functions produced by ERA-Interim wind speeds differed significantly from those produced using AWS wind speeds. The rapid decrease in SIC during a strong wind event is followed by a more gradual recovery in SIC. This increase occurs on a more gradual time scale than the average persistence of a strong wind event and the resulting sea ice motion anomalies, highlighting the production of new sea ice through thermodynamic processes. In the vicinity of Ross Island, ERA-Interim underestimates wind speeds by a factor of 1.7, which results in a significant misrepresentation of the impact of winds on polynya processes.

scholarly journals Numerical Simulation of Near-Surface Wind during a Severe Wind Event in a Complex Terrain by Multisource Data Assimilation and Dynamic Downscaling

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
De Zhang ◽  
Luyuan Chen ◽  
Feimin Zhang ◽  
Juan Tan ◽  
Chenghai Wang
Keyword(s):  
Wind Speed ◽  
Data Assimilation ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Dynamic Downscaling ◽  
Near Surface ◽  
Wind Event ◽  
Weak Wind

Accurate forecast and simulation of near-surface wind is a great challenge for numerical weather prediction models due to the significant transient and intermittent nature of near-surface wind. Based on the analyses of the impact of assimilating in situ and Advanced Tiros Operational Vertical Sounder (ATOVS) satellite radiance data on the simulation of near-surface wind during a severe wind event, using the new generation mesoscale Weather Research and Forecasting (WRF) model and its three-dimensional variational (3DVAR) data assimilation system, the dynamic downscaling of near-surface wind is further investigated by coupling the microscale California Meteorological (CALMET) model with the WRF and its 3DVAR system. Results indicate that assimilating in situ and ATOVS radiance observations strengthens the airflow across the Alataw valley and triggers the downward transport of momentum from the upper atmosphere in the downstream area of the valley in the initial conditions, thus improving near-surface wind simulations. Further investigations indicate that the CALMET model provides more refined microtopographic structures than the WRF model in the vicinity of the wind towers. Although using the CALMET model achieves the best simulation of near-surface wind through dynamic downscaling of the output from the WRF and its 3DVAR assimilation, the simulation improvements of near-surface wind speed are mainly within 1 m s−1. Specifically, the mean improvement proportions of near-surface wind speed are 64.8% for the whole simulation period, 58.7% for the severe wind period, 68.3% for the severe wind decay period, and 75.4% for the weak wind period. The observed near-surface wind directions in the weak wind conditions are better simulated in the coupled model with CALMET downscaling than in the WRF and its 3DVAR system. It is concluded that the simulation improvements of CALMET downscaling are distinct when near-surface winds are weak, and the downscaling effects are mainly manifested in the simulation of near-surface wind directions.

scholarly journals Estimation of Strong Wind Distribution on the Korean Peninsula for Various Recurrence Periods: Significance of Nontyphoon Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jae-Hee Hahm ◽  
Ha-Yoon Jeong ◽  
Kyung-Hwan Kwak
Keyword(s):  
Wind Speed ◽  
Korean Peninsula ◽  
Model Simulation ◽  
Action Plan ◽  
Wrf Model ◽  
Coastal Region ◽  
Gumbel Distribution ◽  
Strong Wind ◽  
Coastal Regions ◽  
Strong Winds

Long-term automated synoptic observing system (ASOS) data collected from 101 stations over a period of 50 years (1967–2016) were analyzed to investigate the distribution of strong winds on the Korean peninsula by utilizing a statistical method. The Gumbel distribution was used to estimate the wind speed for recurrence periods of 1, 10, 50, 75, and 100 years. For all recurrence periods, the coastal regions experienced higher wind speeds, which exceeded the strong wind advisory level, than the inland and metropolitan regions. The strong winds were predominantly induced by summertime typhoons, especially in the south and west coastal regions. In addition, nontyphoon factors, such as a topographical factor with atmospheric instability in a mountainous coastal region, can cause localized severe weather in the form of strong wind. By performing the weather research and forecasting (WRF) model simulation, an abrupt increase in wind speed up to 20 m·s−1 was reproduced under the condition of onshore prevailing winds heading toward a mountain ridge in a coastal region. Estimation of strong wind spatial distribution can help the region-to-region establishment of an action plan to prepare for damage caused by strong winds.

scholarly journals The Quinault Blowdown: A Microscale Wind Event Driven by a Mountain-Wave Rotor

2019 ◽  
Vol 100 (6) ◽  
pp. 977-986
Author(s):  
Clifford F. Mass ◽  
Robert Conrick ◽  
Nicholas Weber ◽  
Joseph P. Zagrodnik
Keyword(s):  
High Resolution ◽  
Wrf Model ◽  
High Amplitude ◽  
Strong Wind ◽  
Mountain Wave ◽  
The North ◽  
Wave Rotors ◽  
Wind Event ◽  
Strong Shear ◽  
Strong Winds

AbstractOn 27 January 2018, a highly localized, strong wind event occurred along the north shore of Lake Quinault, Washington. The resulting loss of large old-growth trees in a roughly 0.5-km2 region led to blocked roads and power outages. Nearby surface stations did not record anomalous winds, and no tree damage was reported in the surrounding region. Based on public accounts and a nearby seismometer, it appears that the strong winds lasted less than 10 min. Surface and aerial damage surveys showed that the trees fell from a different direction (northerly) than the synoptic or mesoscale f low (southwesterly to southeasterly). Based on high-resolution Weather Research and Forecasting (WRF) Model simulations, it appears that the damaging northerly winds were the result of a strong atmospheric rotor produced by a high-amplitude mountain wave. A simulation with 148-m grid spacing produced a rotor at the same time and location as the treefalls. Synoptic analysis and the high-resolution simulation showed that moderately strong southeasterly flow and a stable layer associated with the approaching occluded front interacted with a ∼750-m-high upstream mountain ridge to produce the mountain wave and associated rotor circulation. The combination of an inversion and strong shear at and above the upstream ridge were outliers in a climatology of soundings from the nearby Quillayute rawinsonde site, suggesting that such intense mountain-wave rotors are unusual in this valley.

Roads of Arabia: New finds of Aqaba amphorae in the Red Sea from a newly discovered wreck site at Jeddah/Eliza shoals

2020 ◽  
Author(s):  
Rupert Brandmeier
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Saudi Arabian ◽  
Maritime Archaeology ◽  
Western Coast ◽  
Research Activities ◽  
Red Sea Coast ◽  
Insight Into ◽  
Sea Coast

This paper concerns a probable shipwreck cargo of Aqaba amphorae, which was discovered during the second season of the survey project along the Saudi Arabian coast, initiated by nautical archaeologists of Philipps-University Marburg and conducted in cooperation with members of the Saudi Commission for Tourism and Heritage in autumn 2013. Seafaring and sea trade was, according to the few ancient sources and modern research activities, a hazardous endeavor in antiquity. Transport containers like the Aqaba Amphorae played a major role in sea trade, a significant number of which have been detected on various sites along the Red Sea coast and its hinterland. The chronological classification as well as the application is far from complete, and recent archaeometrical investigations help to clarify the logistical aspects of manufacturing and distribution of Aqaba amphorae. Finding a number of remains of Aqaba amphorae at a supposed shipwreck site close to Jeddah delivers new insight into the maritime routes and activities along the western coast of Saudi Arabia. The documentary material currently available is the baseline for further research in the field of maritime archaeology as it pertains to trade in the Red Sea.

A Nabatean port on the Red Sea: note on the pottery finds from al-Qusayr (al-Wajh, Saudi Arabia)

2020 ◽  
Author(s):  
Caroline Durand
Keyword(s):  
Saudi Arabia ◽  
19Th Century ◽  
Red Sea ◽  
Point Of View ◽  
The Other ◽  
Trade Routes ◽  
Other Hand ◽  
Roman Egypt ◽  
Pottery Sherds ◽  
First Time

Al-Qusayr is located 40 km south of modern al-Wajh, roughly 7 km from the eastern Red Sea shore. This site is known since the mid-19th century, when the explorer R. Burton described it for the first time, in particular the remains of a monumental building so-called al-Qasr. In March 2016, a new survey of the site was undertaken by the al-‘Ula–al-Wajh Survey Project. This survey focused not only on al-Qasr but also on the surrounding site corresponding to the ancient settlement. A surface collection of pottery sherds revealed a striking combination of Mediterranean and Egyptian imports on one hand, and of Nabataean productions on the other hand. This material is particularly homogeneous on the chronological point of view, suggesting a rather limited occupation period for the site. Attesting contacts between Mediterranean merchants, Roman Egypt and the Nabataean kingdom, these new data allow a complete reassessment of the importance of this locality in the Red Sea trade routes during antiquity.

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