Sensitivity analysis to physical parameterizations schemes applied for wind forecasting

2020 ◽  
Author(s):  
Andrés Merino ◽  
Guillermo Mérida ◽  
Pablo Melcón ◽  
Laura López ◽  
José Luis Marcos ◽  
...  
Keyword(s):  
Surface Wind ◽  
Correlation Coefficients ◽  
Horizontal Resolution ◽  
Good Prediction ◽  
Excellent Correlation ◽  
Atmospheric Physics ◽  
Ensemble Techniques ◽  
Aerospace Technology ◽  
Low Levels ◽  
Different Levels

<p>The airborne research center called CIAR is placed in the airfield of Rozas (Lugo, Spain). It is a center for experimentation and development of new Unmanned Aerial Vehicles. Since you need to have a good planning of the flights of the prototypes, it is necessary to have a good prediction of the wind at different levels of height.</p><p>To obtain a reliable database for wind at different vertical levels, three types of instruments have been used: anemometers installed at 10 meters high to determine surface wind, a sodar for levels below 150 meters and a wind radar for those between 200 and 3000 m high above the CIAR level.</p><p>Concerning the mesoscale modelling: we have used the WRF with 48 sigma levels and horizontal resolution of up to 3 x 3 km. Therefore, we have applied multiphysics ensemble techniques. Five combinations of microphysics schemes (AEROSOL THOMPSON, MORRISON 2 MOMENTS, THOMPSON, GODDARD and WRF 2 MOMENTS), three of PBL (MYNN3, YSU and MYJ), and two of Surface (NOAA and RUC) have been selected.</p><p>Once the wind data databases were obtained, by means of the different instrumentation indicated above, it has been compared with each of the 20 WRF scenarios. To visualize the results, Taylor diagrams have been used for the different heights.</p><p>In summary, some conclusions have been found:</p><ol><li>It’s necessary distinguish between low levels and those of slightly higher heights. On the surface, the scenarios with the PBL parameterizations called YSU and MYNN3 show better results.</li> <li>It seems that the microphysics schemes settings have a less importance in wind forecast, which is consistent with the physical interpretation.</li> <li>Above 200 meter, the 20 scenarios behave more satisfactorily with excellent correlation coefficients and low standard deviations</li> </ol><p><strong>Acknowledgment</strong></p><p>Data support came from the Atmospheric Physics Group, IMA, University of León, Spain, and the National Institute of Aerospace Technology (INTA). This research was carried out in the framework of the SAFEFLIGHT project, financed by MINECO (CGL2016‐78702) and LE240P18 project (Junta de Castilla y León). We also thank R. Weigand for computer support to the research group.</p>

scholarly journals The Effectiveness of Ensemble-Neural Network Techniques to Predict Peak Uplift Resistance of Buried Pipes in Reinforced Sand

2021 ◽  
Vol 11 (3) ◽  
pp. 908
Author(s):  
Jie Zeng ◽  
Panagiotis G. Asteris ◽  
Anna P. Mamou ◽  
Ahmed Salih Mohammed ◽  
Emmanuil A. Golias ◽  
...  
Keyword(s):  
Neural Network ◽  
Numerical Models ◽  
Correlation Coefficients ◽  
Network Models ◽  
Small Scale ◽  
Offshore Platforms ◽  
Neural Network Models ◽  
Buried Pipes ◽  
Ensemble Techniques ◽  
Uplift Resistance

Buried pipes are extensively used for oil transportation from offshore platforms. Under unfavorable loading combinations, the pipe’s uplift resistance may be exceeded, which may result in excessive deformations and significant disruptions. This paper presents findings from a series of small-scale tests performed on pipes buried in geogrid-reinforced sands, with the measured peak uplift resistance being used to calibrate advanced numerical models employing neural networks. Multilayer perceptron (MLP) and Radial Basis Function (RBF) primary structure types have been used to train two neural network models, which were then further developed using bagging and boosting ensemble techniques. Correlation coefficients in excess of 0.954 between the measured and predicted peak uplift resistance have been achieved. The results show that the design of pipelines can be significantly improved using the proposed novel, reliable and robust soft computing models.

scholarly journals IAP-AACM v1.0： Global to regional evaluation of the atmospheric chemistry model in CAS-ESM

2018 ◽  
Author(s):  
Ying Wei ◽  
Xueshun Chen ◽  
Huansheng Chen ◽  
Jie Li ◽  
Zifa Wang ◽  
...  
Keyword(s):  
East Asia ◽  
Spatial Variation ◽  
Atmospheric Chemistry ◽  
Comprehensive Evaluation ◽  
Correlation Coefficients ◽  
Full Description ◽  
Atmospheric Physics ◽  
Temporal And Spatial Variability ◽  
Fine Mode ◽  
Aerosol Effects

Abstract. In this study, a full description and comprehensive evaluation of a global-regional nested model, the Aerosol and Atmospheric Chemistry Model of the Institute of Atmospheric Physics (IAP-AACM), is presented for the first time. Not only the global budgets and distribution, but also a comparison of nested simulation over China against multi-datasets are investigated, benefiting from the access of air quality monitoring data in China since 2013 and the Model Inter-Comparison Study for Asia project. The model results and analysis can greatly help reduce uncertainties and understand model diversity in assessing global and regional aerosol effects, especially over East Asia and areas affected by East Asia. The 1-year simulation for 2014 shows that the IAP-AACM is within the range of other models, and well reproduces both spatial distribution and seasonal variation of trace gases and aerosols over major continents and oceans (mostly within the factor of two). The model nicely captures spatial variation for carbon monoxide except an underestimation over the ocean that also shown in other models, which suggests the need for more accurate emission rate of ocean source. For aerosols, the simulation of fine-mode particulate matter (PM2.5) matches observation well and it has a better simulating ability on primary aerosols than secondary aerosols. This calls for more investigation on aerosol chemistry. Furthermore, IAP-AACM shows the superiority of global model, compared with regional model, on performing regional transportation for the nested simulation over East Asia. For the city evaluation over China, the model reproduces variation of sulfur dioxide (SO2), nitrogen dioxide (NO2) and PM2.5 accurately in most cities, with correlation coefficients above 0.5. Compared to the global simulation, the nested simulation exhibits an improved ability to capture the high temporal and spatial variability over China. In particular, the correlation coefficients for PM2.5, SO2 and NO2 are raised by ~ 0.25, ~ 0.15 and ~ 0.2 respectively in the nested grid. The summary provides constructive information for the application of chemical transport models. In future, we recommend the model's ability to capture high spatial variation of PM2.5 is yet to be improved.

scholarly journals Standing crops of dominant combretum species at three browsing levels in the Kruger National Park

Koedoe ◽  
1978 ◽  
Vol 21 (1) ◽  
Author(s):  
B.R. Dayton
Keyword(s):  
National Park ◽  
Correlation Coefficients ◽  
Kruger National Park ◽  
Total Biomass ◽  
Regression Equations ◽  
Stem Height ◽  
Basal Diameter ◽  
Independent Variable ◽  
Combretum Apiculatum ◽  
Different Levels

In red bushwillow veld near the Sand River in the Kruger National Park, Republic of South Africa, a determination was made of the standing crops of Combretum apiculatum and C. zeyheri at browsing levels delineated by the maximum feeding heights of impala (1,5 m), kudu (2,5 m) and giraffe (5,5 m). Using harvested sample trees, logarithmic or linear regression equations were generated which related basal diameter or stem height to biomass or percentage of total biomass at the different levels. Biomass was divided into two components: current shoots and wood plus bark. Regression forms and variables which produced the highest correlation coefficients changed with changes in species or browsing level, however, most equations were logarithmic with basal diameter as the independent variable.

scholarly journals Graphics algorithm for deriving atmospheric boundary layer heights from CALIPSO data

2018 ◽  
Vol 11 (9) ◽  
pp. 5075-5085 ◽  
Author(s):  
Boming Liu ◽  
Yingying Ma ◽  
Jiqiao Liu ◽  
Wei Gong ◽  
Wei Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Weather Forecasting ◽  
Correlation Coefficients ◽  
Horizontal Resolution ◽  
Backscatter Coefficient ◽  
Distribution Method ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Ground Based Lidar

Abstract. The atmospheric boundary layer is an important atmospheric feature that affects environmental health and weather forecasting. In this study, we proposed a graphics algorithm for the derivation of atmospheric boundary layer height (BLH) from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data. Owing to the differences in scattering intensity between molecular and aerosol particles, the total attenuated backscatter coefficient 532 and attenuated backscatter coefficient 1064 were used simultaneously for BLH detection. The proposed algorithm transformed the gradient solution into graphics distribution solution to overcome the effects of large noise and improve the horizontal resolution. This method was then tested with real signals under different horizontal smoothing numbers (1, 3, 15 and 30). Finally, the results of BLH obtained by CALIPSO data were compared with the results retrieved by the ground-based lidar measurements. Under the horizontal smoothing number of 15, 12 and 9, the correlation coefficients between the BLH derived by the proposed algorithm and ground-based lidar were both 0.72. Under the horizontal smoothing number of 6, 3 and 1, the correlation coefficients between the BLH derived by graphics distribution method (GDM) algorithm and ground-based lidar were 0.47, 0.14 and 0.12, respectively. When the horizontal smoothing number was large (15, 12 and 9), the CALIPSO BLH derived by the proposed method demonstrated a good correlation with ground-based lidar. The algorithm provided a reliable result when the horizontal smoothing number was greater than 9. This finding indicated that the proposed algorithm can be applied to the CALIPSO satellite data with 3 and 5 km horizontal resolution.

scholarly journals Density functional studies of the dipole polarizabilities of the linear polyacenes benzene through nonacene

2005 ◽  
Vol 3 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Alan Hinchliffe ◽  
Beatrice Nikolaidi ◽  
Humberto Soscún Machado
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Correlation Coefficients ◽  
Statistical Correlation ◽  
Tensor Component ◽  
Dipole Polarizability ◽  
Functional Studies ◽  
Absolute Agreement ◽  
Different Levels ◽  
Dipole Polarizabilities

AbstractWe report Ab Initio studies of the electric dipole polarizability of the linear polyacene series benzene through nonacene. A number of Ab Initio studies were done at different levels of theory for benzene, with all remaining Ab Initio calculations being at the B3LYP/6-311G(2d, 1p)//B3LYP/6-311+G(2d, 1p) level of theory. We find that the NN tensor component shows a constant increment of 20 atomic units per ring. AM1 and QSAR-quality empirical calculations show poor absolute agreement with the Ab Initio results but given excellent statistical correlation coefficients with the Ab Initio values. This implies that the results of such cheaper calculations can be suitably scaled for predictive purposes.

scholarly journals Global trends in visibility: implications for dust sources

2007 ◽  
Vol 7 (12) ◽  
pp. 3309-3339 ◽  
Author(s):  
N. M. Mahowald ◽  
J. A. Ballantine ◽  
J. Feddema ◽  
N. Ramankutty
Keyword(s):  
Land Use ◽  
Human Impacts ◽  
Dominant Role ◽  
Surface Wind ◽  
Correlation Coefficients ◽  
Severity Index ◽  
Drought Severity ◽  
Climate Indices ◽  
Desert Dust ◽  
Dust Sources

Abstract. There is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. We did this by looking at time series of visibility derived variables and their correlations with precipitation, drought, winds, land use and grazing. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 357 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility-derived variables and AERONET optical depths indicate a moderate correlation (0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility-derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the Palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not correlated with visibility-derived variables in this analysis. There are few stations where visibility measures are correlated with cultivation or grazing estimates on a temporal basis, although this may be a function of the very coarse temporal resolution of the land use datasets. On the other hand, spatial analysis of the visibility data suggests that natural topographic lows are not correlated with VIS5 or EXT, but land use is correlated at a moderate level. This analysis is consistent with land use being important in some regions, but meteorology driving interannual variability during 1974–2003.

scholarly journals Variation in Human Disturbance Differentially Affects Predation Risk Assessment in Western Gulls

The Condor ◽  
2005 ◽  
Vol 107 (1) ◽  
pp. 178-181 ◽  
Author(s):  
Nicolaas V. Webb ◽  
Daniel T. Blumstein
Keyword(s):  
Human Disturbance ◽  
Anthropogenic Impacts ◽  
Important Goal ◽  
Larus Occidentalis ◽  
Predation Risk Assessment ◽  
Santa Monica ◽  
Low Levels ◽  
A Site ◽  
Different Levels ◽  
Flight Initiation

Abstract Many studies have demonstrated that birds behave differently in areas with different levels of human disturbance. Studies frequently characterize sites as having an overall level of human disturbance, and compare how birds respond at sites with high and low levels of disturbance. Doing so assumes that disturbance has a fairly constant effect on animals throughout a site. We measured the distance at which individual Western Gulls (Larus occidentalis) moved away from an approaching observer along a stretch of beach on both sides of the Santa Monica Pier, a heavily visited tourist attraction in southern California. We found that these flight initiation distances decreased in areas where more people visited the beach, and specifically in a small area near the pier. We found that flight initiation distance changed very rapidly within a short distance from the pier. Our results indicate that anthropogenic features may leave a “behavioral footprint.” Identifying the scale of such behavioral footprints should be an important goal of studies that seek to reduce anthropogenic impacts on birds. La Variación del Disturbio Humano Afecta Diferencialmente la Percepción del Riesgo de Depredación en Gaviotas Larus occidentalis Resumen. Muchos estudios han demostrado que las aves se comportan de modo diferente en áreas con distintos niveles de disturbio humano. Los estudios frecuentemente caracterizan sitios con base en su nivel general de disturbio y comparan las respuestas de las aves entre lugares con niveles altos y bajos de disturbio. Al hacer esto, se supone que el disturbio tiene un efecto aproximadamente constante sobre los animales a través de un sitio dado. En este estudio medimos la distancia a la cual gaviotas de la especie Larus occidentalis se desplazaron alejándose de un observador a lo largo de un tramo de playa en ambos lados del embarcadero de Santa Monica, una atracción turística muy visitada ubicada en el sur de California. Encontramos que las distancias al observador a las que las aves iniciaron el vuelo disminuyeron en áreas donde más personas visitaron la playa, y específicamente en un área cercana al embarcadero. Las distancias a las que las gaviotas iniciaron el vuelo cambiaron muy rá pidamente en una distancia muy corta desde el puerto, hasta alcanzar una distancia constante. Nuestros resultados indican que las estructuras antropogénicas podrian dejar una “huella comportamental”. Identificar la escala de dichas huellas debería ser un objetivo importante de estudios que tengan como fin reducir el impacto antrópico sobre las aves.

scholarly journals Productive and Economic Viability of Raising Beef Cattle in the Savanna of the Brazilian State of Goiás

2018 ◽  
Vol 56 (3) ◽  
pp. 395-410 ◽  
Author(s):  
Elis Regina de Oliveira ◽  
Victor Rezende Moreira Couto
Keyword(s):  
Beef Cattle ◽  
Economic Viability ◽  
Economic Sustainability ◽  
Grazing System ◽  
Technical Specifications ◽  
Beef Cattle Production ◽  
Low Levels ◽  
Start Ups ◽  
Different Levels ◽  
Dry And Rainy Seasons

Abstract: The present study evaluates the economic viability of four different models of beef cattle production in the rio Vermelho hydrographic basin. The study focuses on the traditional extensive ranching system, which was compared to three intensive systems, one based on low levels of concentrated supplementation, a second with low levels of concentrated supplementation and confinement for fattening and an intensive grazing system, with supplementation during the dry and rainy seasons. The investments were estimated for the different levels of technical specifications of each system. The net present values and internal return rate were used for the assessment of the economic viability of the project, considering the minimum rate of attractiveness, equivalent to the inflation-adjusted savings interest rate (6.17%). The continuity of the sector was evaluated based on the gross and net margins, and profitability rates, where the system is already installed. All four systems had gross and net margins and profitability consistent with their economic sustainability over both the short and long terms. However, only two systems (reduced consumption of concentrated supplements and the intensive grazing system) were economically viable as start-ups.

Does strategic planning help firms translate slack resources into better performance?

2018 ◽  
Vol 26 (4) ◽  
pp. 395-407 ◽  
Author(s):  
Jinyu Guo ◽  
Bo Zhou ◽  
Haili Zhang ◽  
Chunjia Hu ◽  
Michael Song
Keyword(s):  
Firm Performance ◽  
Strategic Planning ◽  
External Environment ◽  
Organizational Slack ◽  
Low Levels ◽  
Using Data ◽  
The Impact ◽  
Performance Research ◽  
Practical Implications ◽  
Different Levels

AbstractIs organizational slack good or bad for firm performance? Research addressing this question has obtained mixed results. Such studies have focused mainly on the impact of environmental conditions on the slack–performance relationship. In this study, instead of focusing on the uncontrollable external environment, we consider actions determined by firms internally, in particular strategic planning. Using data from 183 US firms, we explore the connection between organizational slack and firm performance with different levels of strategic planning. The results suggest that at low levels of strategic planning the slack–performance relationship is linear, while at high levels of strategic planning this relationship is inverse U shaped. We discuss the theoretical and practical implications of these findings.

Evaluation of populations of Dactylis glomerata L. native to Mediterranean environments

2012 ◽  
Vol 63 (12) ◽  
pp. 1124 ◽  
Author(s):  
V. Copani ◽  
G. Testa ◽  
A. Lombardo ◽  
S. L. Cosentino
Keyword(s):  
Genetic Diversity ◽  
Biomass Yield ◽  
Agronomic Traits ◽  
Dactylis Glomerata ◽  
Leaf Length ◽  
Mediterranean Environment ◽  
Summer Dormancy ◽  
Low Levels ◽  
Dactylis Glomerata L ◽  
Different Levels

Several morphological and agronomic traits and the genetic diversity of nine Dactylis glomerata L. populations collected throughout Sicily (semi-arid Mediterranean environment) were evaluated for two successive years. Significant differences were recorded for morphological traits (plant height, leaf length, leaf width). In relation to the measurement of summer dormancy, the results suggest the expression of different levels of dormancy (completely dormant, semi-dormant, and non-dormant). For biomass yield, some Sicilian populations (SD63 and SD56) characterised by low levels of summer dormancy show production levels similar to the summer-active control varieties (Medly and Porto). However, SD46, with a much higher level of dormancy, gave biomass yield higher than the summer-dormant control variety (Kasbah). The genetic diversity evaluated by fAFLP analysis confirms the observed morphological and agronomic variability.

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