scholarly journals Diurnal Characteristics of Trapped Mountain Waves over the Foothills of Western Nepal Himalaya

2015 ◽  
Vol 20 (1) ◽  
pp. 102-106
Author(s):  
Ram P. Regmi

Late wintertime diurnal variation and spatial distribution of mountain wave excitations over the Mt. Devchuli range and its surrounding areas have been numerically simulated with the application of Weather Research and Forecasting (WRF) Modeling System. The study reveals that the region holds low-level trapped mountain waves almost all the time. The waves are confined below the stratified layer at about 3km above the mean sea level. Wave excitation over the region is highly active during the afternoon time whereas it remains at minimum level during the late morning time. These waves pose significant risk for low-level aviation and parachuting activities.Journal of Institute of Science and Technology, 2015, 20(1): 102-106

2017 ◽  
Vol 56 (2) ◽  
pp. 371-390 ◽  
Author(s):  
Ram P. Regmi ◽  
Toshihiro Kitada ◽  
Jimy Dudhia ◽  
Sangeeta Maharjan

AbstractNepal has been the location of a series of fatal aircraft accidents, raising serious concerns about civil aviation security and the safety of passengers. However, significant studies on weather patterns associated with the airports and air routes of the Himalayan complex terrain and their implications for aviation activities are yet to be carried out. The present study numerically reconstructs the prevailing weather conditions and puts forward some possible causes behind the most recent fatal aircraft accident in the foothills of the western Nepal Himalaya at 0730 UTC (1315 LST) 16 February 2014. The weather patterns have been numerically simulated at 1-km2 horizontal grid resolution using the Weather Research and Forecasting (WRF) modeling system. The reconstructed weather situation shows the existence of a low-level cloud ceiling, supercooled cloud water and hail, trapped mountain waves, supercritical descent of a strong tail wind, and the development of turbulence at the altitude of the flight path followed by the aircraft. The aircraft might have gone through a series of weather hazards including visibility obstruction, moderate turbulence, abnormal loss in altitude, and icing. It is concluded that the weather situation over the region was adverse enough to affect small aircraft and therefore that it might have played an important role leading to the fatal accident. The development of hazardous weather over the region may be attributed to a previously unanticipated large-scale easterly gravity current over the middle hills of the Nepal Himalaya. The gravity current originated from the central high Himalayan mountainous region located northeast of the Kathmandu valley and traveled more than 200 km, reaching the foothills of the western Nepal Himalaya.


2008 ◽  
Vol 81 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Gautam K. Sahu ◽  
David Paar ◽  
Simon D.W. Frost ◽  
Melissa M. Smith ◽  
Scott Weaver ◽  
...  

2007 ◽  
Vol 64 (3) ◽  
pp. 711-737 ◽  
Author(s):  
Matthew F. Garvert ◽  
Bradley Smull ◽  
Cliff Mass

Abstract This study combines high-resolution mesoscale model simulations and comprehensive airborne Doppler radar observations to identify kinematic structures influencing the production and mesoscale distribution of precipitation and microphysical processes during a period of heavy prefrontal orographic rainfall over the Cascade Mountains of Oregon on 13–14 December 2001 during the second phase of the Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) field program. Airborne-based radar detection of precipitation from well upstream of the Cascades to the lee allows a depiction of terrain-induced wave motions in unprecedented detail. Two distinct scales of mesoscale wave–like air motions are identified: 1) a vertically propagating mountain wave anchored to the Cascade crest associated with strong midlevel zonal (i.e., cross barrier) flow, and 2) smaller-scale (<20-km horizontal wavelength) undulations over the windward foothills triggered by interaction of the low-level along-barrier flow with multiple ridge–valley corrugations oriented perpendicular to the Cascade crest. These undulations modulate cloud liquid water (CLW) and snow mixing ratios in the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), with modeled structures comparing favorably to radar-documented zones of enhanced reflectivity and CLW measured by the NOAA P3 aircraft. Errors in the model representation of a low-level shear layer and the vertically propagating mountain waves are analyzed through a variety of sensitivity tests, which indicated that the mountain wave’s amplitude and placement are extremely sensitive to the planetary boundary layer (PBL) parameterization being employed. The effects of 1) using unsmoothed versus smoothed terrain and 2) the removal of upstream coastal terrain on the flow and precipitation over the Cascades are evaluated through a series of sensitivity experiments. Inclusion of unsmoothed terrain resulted in net surface precipitation increases of ∼4%–14% over the windward slopes relative to the smoothed-terrain simulation. Small-scale waves (<20-km horizontal wavelength) over the windward slopes significantly impact the horizontal pattern of precipitation and hence quantitative precipitation forecast (QPF) accuracy.


2017 ◽  
Vol 4 (1) ◽  
pp. 54
Author(s):  
Ram P. Regmi ◽  
Sangeeta Maharjan

<p class="Default">Wind power potential prevailing over the world’s deepest river gorge, the Kali Gandaki River Valley, located in the western trans-Himalaya region of Nepal, has been assessed and mapped at 1 km × 1 km horizontal grid resolution with the application of Weather Research and Forecasting (WRF) modeling system. The wind power potential maps cover 70 km × 70 km area, which encloses the very first and failed wind power project in the country and the Jomsom Airport at the center. The simulated wind characteristics compare well with the available observed wind characteristic. The wind power potential appears to vary from good to outstanding over 200 km<sup>2</sup> area along the axis of Kali Gandaki River Valley. However, a detail long-term observation, numerical simulation as well as engineering examinations are desired to address abnormal valley wind characteristics for sustainable power production over the area.</p><p class="Default"><strong>Journal of Nepal Physical Society </strong></p><p><em>Volume 4, Issue 1, February 2017, Page : 54-59</em></p>


2021 ◽  
Vol 2 (1) ◽  
pp. 78-87
Author(s):  
Tamás Palicz ◽  
Balázs Bencsik ◽  
Miklós Szócska

Összefoglaló. A COVID–19 pandémia az információbiztonság területén új kihívásokat jelentett. A távolról végzett munka különböző formái jelentős mértékben növelték az online tér biztonsági kockázatát. Nőtt a hálózatok nagysága, az adatforgalom, és azon felhasználók száma, akiknek nem volt érdemi tapasztalatuk az online térben. A járvány ideje alatt a kibertérből érkező támadások szektoronként és időszakonként eltérő intenzitásúak voltak, a támadások típusa a phishingtől a malwareken keresztül az információs zavarkeltésig széles spektrumban változott. Számos jelenségnek nemzetbiztonsági vonatkozásai is voltak. Összefoglaló cikkünkben a fenti jelenségek nemzetközi és hazai tapasztalatait összegezzük, különös figyelmet szentelve az egészségügyi rendszernek, illetve a vakcinafejlesztés kibertérből érkező fenyegetéseinek. Summary. During the COVID-19 pandemic, new challenges emerged in the field of information security and cyber security. Home office, home schooling and distance learning, or even telemedicine hit some organizations unprepared. Security risks in online space have increased significantly: the number of network endpoints and the number of computers, laptops and mobile devices have increased with network data traffic as well as the number of users who had no significant experience in online space. They appeared as a significant risk factor. This has been exacerbated, especially in healthcare, by the extremely high workload, which has made systems highly vulnerable. During the epidemic, attacks from cyberspace varied in intensity from sector to sector and period to period. Statistics from international and national organizations have shown that from the end of the first quarter of 2020, the number of cyber security incidents jumped sharply and then remained high even after a small decline. The types of attacks had an extremely wide range: from phishing through malware to misinformation, almost all types of attacks occurred. Many phenomena also had national security implications. Ransomware virus attacks on health have affected almost all health systems and reached high levels by the end of 2020 in particular. It was during the first period that, in an emergency case, there is thought to be an association between a ransomware virus attack and the death of a patient who was not admitted because of the attack. In addition to distance measures and the associated increase in cyber threats, the emerging threats related to vaccination, which is central to the fight against the epidemic, should also be highlighted. This period has shed light on how many vulnerabilities there are, from vaccine development through drug trials to delivery to vaccines and the organization of vaccines, that cybercriminals are able to attack. In order to prevent and combat these threats and attacks, and to respond appropriately, complex, multidisciplinary collaborations are needed in which security science has a privileged place. In our review article, we summarize the international and national experiences of the above phenomena, paying special attention to the health care system and the threats coming from cyberspace in vaccine development.


2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Javier Díaz-Fernández ◽  
Lara Quitián-Hernández ◽  
Pedro Bolgiani ◽  
Daniel Santos-Muñoz ◽  
Ángel García Gago ◽  
...  

Turbulence and aircraft icing associated with mountain waves are weather phenomena potentially affecting aviation safety. In this paper, these weather phenomena are analysed in the vicinity of the Adolfo Suárez Madrid-Barajas Airport (Spain). Mountain waves are formed in this area due to the proximity of the Guadarrama mountain range. Twenty different weather research and forecasting (WRF) model configurations are evaluated in an initial analysis. This shows the incompetence of some experiments to capture the phenomenon. The two experiments showing the best results are used to simulate thirteen episodes with observed mountain waves. Simulated pseudosatellite images are validated using satellite observations, and an analysis is performed through several skill scores applied to brightness temperature. Few differences are found among the different skill scores. Nevertheless, the Thompson microphysics scheme combined with the Yonsei university PBL scheme shows the best results. The simulations produced by this scheme are used to evaluate the characteristic variables of the mountain wave episodes at windward and leeward and over the mountain. The results show that north-northwest wind directions, moderate wind velocities, and neutral or slightly stable conditions are the main features for the episodes evaluated. In addition, a case study is analysed to evidence the WRF ability to properly detect turbulence and icing associated with mountain waves, even when there is no visual evidence available.


2006 ◽  
Vol 33 (5) ◽  
pp. 427 ◽  
Author(s):  
Brendan D. Cowled ◽  
Eddie Gifford ◽  
Michelle Smith ◽  
Linton Staples ◽  
Steven J. Lapidge

Conservative population declines of 73% were recorded in three independent feral pig populations in Welford National Park, Queensland, when PIGOUT® baits containing 72 mg of sodium fluoroacetate were used in a baiting program following prefeeding. Declines were measured using a prebaiting population census with remote cameras, followed by carcass recovery. The knockdown of susceptible feral pigs may have been higher than this, since any carcasses not recovered reduced the recorded efficacy. In addition, feral pigs know to have left the baiting area after trapping and telemetry-tagging, and subsequently not exposed to toxic baits, were included in the analysis. The use of remote cameras and carcass recovery appears to be a relatively accurate means of recording localised declines in feral pig populations. This method is applicable only when carcass recovery is possible, such as in open areas in the semi-arid rangelands. A decline of 86% of radio-tagged feral pigs attending bait stations was also recorded. Camera observations revealed no non-target consumption of baits. Measurement of sodium fluoroacetate–contaminated tissues from feral pigs showed that residues were too low to present a significant risk to recorded scavenging animals in the area. Some feral pigs vomited before death, with vomitus containing sodium fluoroacetate poison at high concentrations. No vomitus was consumed by non-target species. Almost all feral pigs were killed relatively rapidly after ingestion of sodium fluoroacetate and the signs observed in a small number of poisoned feral pigs did not indicate a significant welfare concern.


2021 ◽  
Author(s):  
Andreas Dörnbrack

&lt;table&gt;&lt;tbody&gt;&lt;tr&gt;&lt;td&gt; &lt;p&gt;&lt;span&gt;Planetary waves disturbed the hitherto stable Arctic stratospheric polar vortex mid of&lt;br&gt;January 2016 in such a way that unique tropospheric and stratospheric flow conditions&lt;br&gt;for vertically and horizontally propagating mountain waves developed. Co-existing&lt;br&gt;strong low-level westerly winds across almost all European mountain ranges plus the&lt;br&gt;almost zonally-aligned polar front jet created these favorable conditions for deeply&lt;br&gt;propagating gravity waves. Furthermore, the northward displacement of the polar night&lt;br&gt;jet resulted in a wide-spread coverage of stratospheric mountain waves trailling across&lt;br&gt;northern Europe. This paper describes the particular meteorological setting by&lt;br&gt;analyzing the tropospheric and stratospheric flows based on the ERA5 data. The&lt;br&gt;potential of the flow for exciting internal gravity waves from non-orographic sources is&lt;br&gt;evaluated across all altitudes by considering various instability indices as &amp;#948; , Ro, Ro &amp;#950; , Ro&lt;sub&gt;&amp;#8869;&lt;/sub&gt; ,&lt;br&gt;and &amp;#916; NBE&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;span&gt;The analyzed gravity waves are described and characterized in terms of&lt;br&gt;commonly used parameters. The main finding of this case study is the exceptionally&lt;br&gt;vast extension of the mountain waves trailing to high latitudes originating from the flow&lt;br&gt;across the mountainous sources that are located at about 45 N. As a useful addition to&lt;br&gt;the case study, tracks for potential research flights are proposed that sample the&lt;br&gt;waves by a vertically pointing airborne remote-sensing instrument. Benefits and&lt;br&gt;drawbacks of the different approaches to observe the meridional focussing of the&lt;br&gt;mountain waves into the polar night jet are discussed.&lt;/span&gt;&lt;/p&gt; &lt;/td&gt; &lt;/tr&gt;&lt;/tbody&gt;&lt;/table&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;


2022 ◽  
pp. 17-33
Author(s):  
Ahmet Çetinkaya ◽  
Ali Murat Kırık

As the COVID-19 disease rapidly transmitted through interpersonal contact, it required people to avoid physical contact. Almost all countries in the world have suspended the education of children and youth, a highly active network, and switched to online education to reduce the spread of the virus. Distance education, unlike the traditional education system, has a structure that does not require students to be on a campus or be in the same environment with instructors. As the global epidemic broke out, the distance education system was reviewed, and a new education order started to be established. Students, parents, and teachers found themselves in a situation they were not used to before. In this study, the advantages and disadvantages of distance education are analyzed, hybrid and hybrid-flexible (hyflex) models are examined, the educational changes during the pandemic period as well as the anticipations of the post-pandemic period are reviewed, and lastly, future educational solutions are proposed.


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