Description of Wind Field Dynamic Patterns in a Valley and Their Relation to Mesoscale and Synoptic-Scale Meteorological Situations

1995 ◽  
Vol 34 (1) ◽  
pp. 49-67 ◽  
Author(s):  
R. Guardans ◽  
I. Palomino
Keyword(s):  
Wind Field ◽  
Transition Probabilities ◽  
Meteorological Data ◽  
Atmospheric Dispersion ◽  
Synoptic Situation ◽  
Large Set ◽  
Valley Wind ◽  
Complete Collection ◽  
Emergency Plans ◽  
Synoptic Conditions

Abstract A large set of hourly meteorological data from seven towers deployed in Montesina Valley (Cordoba, Spain) is studied in relation to the prevailing synoptic situation. The complete collection of daily synoptic maps for 1985-90 has been classified in seven basic weather patterns. First-order transition probabilities and weatherpattern persistences have been calculated for each of the patterns. The behavior of the local valley wind field is described as a function of the synoptic patterns. The work reported here, based on observations of the characteristic time and space patterns of flow in the valley under different synoptic conditions, has made it possible to obtain a set of empirical rules and regression functions to produce forecasts of the local wind field as a function of the synoptic situation and the hour of the day to be used in the emergency plans. The result of this work is currently being implemented in an atmospheric dispersion module of an expert system that will be used as a tool to predict the evolution of accidental and routine hazardous emissions to the atmosphere in complex terrain such as valleys and coastal areas.

Simulation of the wind fields over complex terrain with coupling of CFD and WRF

2021 ◽  
pp. 1-12
Author(s):  
Xiaoyu Luo ◽  
Yiwen Cao
Keyword(s):  
Wind Speed ◽  
Wind Field ◽  
Complex Terrain ◽  
Civil Engineering ◽  
Meteorological Data ◽  
Mass Conservation ◽  
Coupling Method ◽  
Wind Fields ◽  
Civil Structures ◽  
Civil Engineers

In the field of civil engineering, the meteorological data available usually do not have the detailed information of the wind near a certain site. However, the detailed information of the wind field during typhoon is important for the wind-resistant design of civil structures. Furthermore, the resolution of the meteorological data available by the civil engineers is too coarse to be applicable. Therefore it is meaningful to obtain the detailed information of the wind fields based on the meteorological data provided by the meteorological department. Therefore, in the present study, a one-way coupling method between WRF and CFD is adopted and a method to keep the mass conservation during the simulation in CFD is proposed. It is found that using the proposed one-way coupling method, the predicted wind speed is closer to the measurement. And the curvature of the wind streamline during typhoon is successfully reproduced.

Influence of the diagnostic wind field model on the results of calculation of the microscale atmospheric dispersion in moderately complex terrain

2013 ◽  
Vol 79 ◽  
pp. 29-35 ◽  
Author(s):  
Ivan V. Kovalets ◽  
Vladimir Y. Korolevych ◽  
Alexander V. Khalchenkov ◽  
Ievgen A. Ievdin ◽  
Mark J. Zheleznyak ◽  
...  
Keyword(s):  
Wind Field ◽  
Complex Terrain ◽  
Field Model ◽  
Atmospheric Dispersion ◽  
Wind Field Model

Evaluation of the performance of different short-range atmospheric dispersion models for the monitoring of CH4 emissions from industrial facilities

2021 ◽  
Author(s):  
Bonaventure Fontanier ◽  
Pramod Kumar ◽  
Grégoire Broquet ◽  
Christopher Caldow ◽  
Olivier Laurent ◽  
...  
Keyword(s):  
High Frequency ◽  
Meteorological Data ◽  
Atmospheric Dispersion ◽  
Local Scale ◽  
Lagrangian Model ◽  
Dispersion Models ◽  
Industrial Facilities ◽  
Gaussian Plume ◽  
Gaussian Puff ◽  
Gaussian Puff Model

<p>Methane (CH<sub>4</sub>) is a powerful greenhouse gas which plays a major role in climate change. The accurate monitoring of emissions from industrial facilities is needed to ensure efficient emission mitigation strategies. Local-scale atmospheric inversions are increasingly being used to provide estimates of the rates and/or locations of CH<sub>4</sub> sources from industrial sites. They rely on local-scale atmospheric dispersion models, CH<sub>4</sub> measurements and inversion approaches. Gaussian plume models have often been used for local-scale atmospheric dispersion modelling and inversions of emissions, because of their simplicity and good performance when used in a flat terrain and relatively constant mean wind conditions. However, even in such conditions, failure to account for wind and mole fraction variability can limit the ability to exploit the full potential of these measurements at high frequency.</p><p>We study whether the accuracy of inversions can be increased by the use of more complex dispersion models. Our assessments are based on the analysis of 25 to 75-min CH<sub>4 </sub>controlled releases during a one-week campaign in October 2019 at the TOTAL’s TADI operative platform in Lacq, France (in a flat area). During this campaign, for each controlled release, we conducted near-surface in situ measurements of CH<sub>4</sub> mole fraction from both a mobile vehicle and a circle of fixed points around the emission area. Our inversions based on a Gaussian model and either the mobile or fixed-point measurements both provided estimates of the release rates with 20-30% precision.  </p><p>Here we focus on comparisons between modeling and inversion results when using this Gaussian plume model, a Lagrangian model “GRAL” and a Gaussian puff model. The parameters for the three models are based on high-frequency meteorological values from a single stationary 3D sonic anemometer. GRAL should have relatively good skills under low-wind speed conditions. The Gaussian puff is a light implementation of time-dependent modeling and can be driven by high-frequency meteorological data. The performance of these dispersion models is evaluated with various metrics from the observation field that are relevant for the inversion. These analyses lead to the exploration of new types of definitions of the observational constraint for the inversions with the Gaussian puff model, when using the timeseries from fixed measurement points. The definitions explore a range of metrics in the time domain as well as in the frequency domain.</p><p>Eventually, the Lagrangian model does not outperform the Gaussian plume model in these experiments, its application being notably limited by the short scales of the transport characteristics. On the other hand, the Gaussian puff model provides promising results for the inversion, in particular, in terms of comparison between the simulated and observed timeseries for fixed stations. Its performance when driven by a spatially uniform wind field is an incentive to explore the use of meteorological data from several sonic stations to parameterize its configuration. The fixed-point measurements are shown to allow for more robust inversions of the source location than the mobile measurements, with an average source localization error of the order of 10 m.</p>

Meteorological study for Gangotri Glacier and its comparison with other high altitude meteorological stations in central Himalayan region

2007 ◽  
Vol 38 (1) ◽  
pp. 59-77 ◽  
Author(s):  
Pratap Singh ◽  
Umesh K. Haritashya ◽  
Naresh Kumar
Keyword(s):  
High Altitude ◽  
Meteorological Data ◽  
Weather Conditions ◽  
Meteorological Station ◽  
Himalayan Region ◽  
Valley Wind ◽  
Maximum Rainfall ◽  
Garhwal Himalayas ◽  
Wind Speeds ◽  
Gangotri Glacier

In spite of the vital role of high altitude climatology in melting of snow and glaciers, retreat or advancement of glaciers, flash floods, erosion and sediment transport, etc., weather conditions are not much studied for the high altitude regions of Himalayas. In this study, a comprehensive meteorological analysis has been made for the Gangotri Meteorological Station (Bhagirathi Valley, Garhwal Himalayas) using data observed for four consecutive melt seasons (2000–2003) covering a period from May to October for each year. The collected meteorological data includes rainfall, temperature, wind speed and direction, relative humidity, sunshine hours and evaporation. The results and their distribution over the different melt seasons were compared with available meteorological records for Dokriani Meteorological Station (Dingad Valley, Garhwal Himalayas) and Pyramid Meteorological Station (Khumbu Valley, Nepal Himalayas). The magnitude and distribution of temperature were found to be similar for different Himalayan regions, while rainfall varied from region to region. The influence of the monsoon was meagre on the rainfall in these areas. July was recorded to be the warmest month for all the regions and, in general, August had the maximum rainfall. For all the stations, daytime up-valley wind speeds were 3 to 4 times stronger than the nighttime down-valley wind speeds. It was found that the Gangotri Glacier area experienced relatively low humidity and high evaporation rates as compared to other parts of the Himalayas. Such analysis reveals the broad meteorological characteristics of the high altitude areas of the Central Himalayan region.

scholarly journals Bora-induced currents corresponding to different synoptic conditions above the Adriatic

2005 ◽  
Vol 23 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
G. Beg Paklar ◽  
A. Bajić ◽  
V. Dadić ◽  
B. Grbec ◽  
M. Orlić
Keyword(s):  
Numerical Model ◽  
Wind Field ◽  
High Speed ◽  
Western Mediterranean ◽  
First Episode ◽  
Surface Currents ◽  
Po River ◽  
Northern Adriatic ◽  
Synoptic Conditions ◽  
Bora Wind

Abstract. The Bora wind field is characterised by strong vorticity and divergence. Several numerical experiments, in which an oceanographic model was forced with northeasterly winds having climatological alongshore variability, were performed in order to study the influence of spatial variability in the bora wind field on the surface currents in the northern Adriatic. Numerical model results showed that during bora episodes with lower speeds and fast offshore decay surface currents along transect Rovinj - Po River are predominantly in the downwind direction. On the other hand, during bora episodes with strong intensity and slow offshore decay, a cyclonic gyre due to the pronounced bora alongshore variability is formed in the northernmost part of the Adriatic Sea and the studied transect is influenced by the counter currents. Moreover, bora having a high speed and a short offshore range produces the same effect in the eastern part of the Rovinj - Po River transect as low-speed bora characterised by slow offshore decay. Eulerian current measurements performed in the northern Adriatic during bora episodes characterised by different synoptic conditions supported the numerical model findings. Surface currents during the bora episode of 8-11 February 1984 were directed downwind, whereas during the episode of 12-19 February 1984 they were directed upwind. The first episode was characterised by a deep bora layer with cyclonic activity over the western Mediterranean and Genoa Bay, whereas the second one was accompanied by temperature inversion and a southwesterly tropospheric wind above a shallow bora layer. According to the hydraulic theory developed by Smith (1985), an observed descent of isentropes during the second bora episode led to the stronger acceleration in the bora layer and its larger offshore extent. Different offshore bora decays during studied events were confirmed by a comparison of the wind data originating from the meteorological stations positioned on the opposite Adriatic coasts.

General solidarity theorems for semi-Markov processes

1972 ◽  
Vol 9 (04) ◽  
pp. 789-802
Author(s):  
Choong K. Cheong ◽  
Jozef L. Teugels
Keyword(s):  
Markov Process ◽  
Markov Processes ◽  
Transition Probabilities ◽  
Large Set ◽  
Semi Markov Process ◽  
Regularly Varying ◽  
Specific Pair ◽  
Semi Markov Processes

Let {Zt, t ≧ 0} be an irreducible regular semi-Markov process with transition probabilities Pij (t). Let f(t) be non-negative and non-decreasing to infinity, and let λ ≧ 0. This paper identifies a large set of functions f(t) with the solidarity property that convergence of the integral ≧ eλtf(t)Pij (t) dt for a specific pair of states i and j implies convergence of the integral for all pairs of states. Similar results are derived for the Markov renewal functions Mij (t). Among others it is shown that f(t) can be taken regularly varying.

scholarly journals Thermally Driven Flows at an Asymmetric Valley Exit: Observations and Model Studies at the Lech Valley Exit

2009 ◽  
Vol 137 (10) ◽  
pp. 3437-3455 ◽  
Author(s):  
Thomas Spengler ◽  
Jan H. Schween ◽  
Markus Ablinger ◽  
Günther Zängl ◽  
Joseph Egger
Keyword(s):  
Shear Zone ◽  
Weather Conditions ◽  
Western Slope ◽  
Eastern Slope ◽  
Valley Wind ◽  
Model Studies ◽  
Synoptic Conditions ◽  
Thermally Driven ◽  
The Alps ◽  
Alpine Foreland

Abstract The summertime thermal circulation in the region of an asymmetric valley exit is investigated by means of observations and high-resolution model simulations. The northeastward-oriented Alpine Lech Valley opening into the Bavarian Alpine foreland has an eastern slope exceeding the western slope by about 15 km. Northerly winds along the eastern slope are frequently observed, reaching substantial strength during fair weather conditions. A field experiment has been conducted to explore this phenomenon and to pinpoint the connection of the northeasterly flow to the Lech Valley wind circulation. Numerical simulations have also been carried out to support the interpretation of the observations. It is found that the northerlies owe their existence to the dominantly easterly flow along the foothills of the Alps, which is partly induced by the Alpine heat low but may be strengthened by favorable synoptic conditions. Examples for both situations will be discussed. The diurnal flow in the Lech Valley has little obvious impact on these northeasterlies. On days with moderate synoptic easterly flow, a wake is present on the lee of the eastern slope of the exit region, accompanied by a shear zone along the edge of the wake. This shear zone is forced southward during the daytime because of thermally initiated pressure gradients between the Alpine foreland and the Alps, leading to sudden wind changes in the exit area at the time of its passage.

An Improved Algorithm for Potential Accident Consequence Assessment at NPPs Based on PAVAN

2017 ◽  
Author(s):  
Chen Qian ◽  
Zhai Liang ◽  
Yin Yuhao ◽  
Tao Yunliang
Keyword(s):  
Nuclear Power ◽  
Meteorological Data ◽  
Atmospheric Dispersion ◽  
Probability Level ◽  
Q Value ◽  
Envelope Curve ◽  
Consequence Assessment ◽  
Joint Frequency ◽  
Accident Consequence ◽  
Improved Algorithm

PAVAN is an atmospheric dispersion program for evaluating design basis accidental releases of radioactive materials from nuclear power plant. It was developed by Pacific Northwest Laboratory on the basic of the atmospheric dispersion models described in RG 1.145 by NRC (U.S. Nuclear Regulatory Commission). Using the joint frequency of wind direction, wind speed and atmospheric stability, the atmospheric relative concentration values for the exclusion area boundary and outer LPZ boundary of nuclear power plant are calculated and given by the program. Once the program was introduced, it has been widely used in the radioactive accident consequence assessment, especially in the FSAR (Final Safety Analysis Report) and Report of EIA (Environmental Impact Assessment) of NPPs in China. The theory basis and general method of PAVAN is introduced in this paper. And specialty of the X/Q points based on joint frequency data is discussed. The envelope algorithm of PAVAN is also introduced and discussed. The paper presents an improved algorithm based on PAVAN which uses the hourly meteorological data as input instead of joint frequency data. In this algorithm, the size of X/Q points is related to the quantity of the hourly meteorological data. When the quantity is large enough, e.g. 17520 sets of hourly meteorological data in two years, the envelope curve for X/Q points fit more exactly than PAVAN. Using the observed meteorological data, the improved algorithm is compared with PAVAN. The result proves that the former is more accurate. In general, the improved algorithm is relatively conservative. In some situation, the conservativeness is not certain. The factors which result in the uncertainty are deeply discussed. Further optimized are performed by the algorithm. The number of points to seek in envelope curve fitting is set to be dynamic and be a quarter of total number of X/Q points to be fitted. The result shows that increasing the number of points to seek in the iteration process of envelope curve fitting will lead to more conservative X/Q values. Additionally, the optimized algorithm provides X/Q value of 50% probability level for overall site. The value is not relatively conservative. From the standpoint of statistical probability, it is more realistic and is acceptable for potential accident consequence assessment. Especially, when X/Q value of 95% probability level for overall site is too conservative to accept, the value of 50% probability level can be used to replace the conservative value.

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