scholarly journals Micrometeorological fog experiments in Budapest and in Sió Valley near Lake Balaton (2018-2021) 

2021 ◽  
Author(s):  
Tamás Weidinger ◽  
András Zénó Gyöngyösi ◽  
Gandhi Arun ◽  
Ágoston Tordai ◽  
Tamás Krámer ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Field Experiments ◽  
Numerical Models ◽  
Sonic Anemometer ◽  
Gradient Methods ◽  
Radiation Budget ◽  
Cold Pool ◽  
Lake Balaton ◽  
Winter Half ◽  
Field Campaigns

<p>Characteristic phenomena in the Pannonian basin during the winter half year are the mist (500-1000 hours/year), the fog (150-300 hours/year) and the cold air pool with high air pollution concentrations. Formation, development and dissipation of fog events are complex processes that are impacted by short- and longwave radiation, condensation and evaporation, turbulent exchange, furthermore fog chemistry. The research presented here aims at exploring the interaction of these processes using field observations. To this end, complex field campaigns were conducted in Budapest (WMO code: 12843) and in the Sió Valley, 6 km away from Siófok (12935) during 1 to 3-month periods in the last three winter half years.</p><p>Besides air chemistry and standard meteorological variables, the leaf wetness, surface and soil temperature, soil moisture, soil heat flux (Huskeflux), radiation budget components (CNR1) and turbulent fluxes based on eddy covariance (CSAT3, EC150) and gradient methods were measured above the grassland. Time resolutions of measurements for slow sensors were 10 sec or rather 1 minute and for eddy covariance system 10 Hz. The mist and fog periods were detected using a cloud camera (in Sió Valley) and by synoptic observations in Budapest and Siófok.</p><p>Additional measurements in Budapest were i) the wind speed (<em>U</em>), air temperature (<em>T</em>) and relative humidity (<em>RH</em>) profiles together with Gill sonic anemometer at the top of a 30 m high tower, ii) LUFT CHM 15k ceilometer. SODAR and aviation meteorological measurements were also available from the<em> </em>Budapest Ferenc Liszt International Airport<em> (</em>LHBP<em>) </em>at 8 km distance.<em> </em>Other<em> </em>field experiments were done in the wet leeward Sió Valley in 2018-19 and 2019-20. Vaisala WXT530 sensor, LUFT CHM 15k ceilometer, tethered balloon measurements with GRAW radiosondes and METEK SODAR measurements were also provided as additional information behind the energy budget measurements.</p><p>Our results confirmed that according to the expectations, we have recorded more foggy situations in the Sió Valley than in Budapest (12843) and Siófok (12935). Radiation and advection type fog events were formed in most cases. The measured <em>RH</em> was above 95 and gradually increased during the onset period of fog. RH was around 100%, fluctuations could be measured less accurately.  Dissipation of the fog is usually characterized by wind intensification and rise in the incoming solar radiation. The data of two field campaigns will be analyzed i) a cold pool situation in Sió Valley in January 2020 and ii) the foggy season 2020-21 in Budapest. The developed complex (micrometeorological, furthermore air and liquid chemistry) database gives opportunity to validate numerical model results (WRF, CHIMERE and detailed box model) and to improve parameterizations of the numerical models.</p>

scholarly journals Turbulence fluxes and variances measured with a sonic anemometer mounted on a tethered balloon

2016 ◽  
Vol 9 (9) ◽  
pp. 4375-4386 ◽  
Author(s):  
Guylaine Canut ◽  
Fleur Couvreux ◽  
Marie Lothon ◽  
Dominique Legain ◽  
Bruno Piguet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
Field Experiments ◽  
Sonic Anemometer ◽  
Motion Sensor ◽  
Tethered Balloon ◽  
Inertial Motion ◽  
Convective Boundary ◽  
Momentum Fluxes ◽  
Field Campaigns

Abstract. This study presents the first deployment in field campaigns of a balloon-borne turbulence probe, developed with a sonic anemometer and an inertial motion sensor suspended below a tethered balloon. This system measures temperature and horizontal and vertical wind at high frequency and allows the estimation of heat and momentum fluxes as well as turbulent kinetic energy in the lower part of the boundary layer. The system was validated during three field experiments with different convective boundary-layer conditions, based on turbulent measurements from instrumented towers and aircraft.

Mapping the Mid-Atlantic Cold Pool evolution and variability with ocean gliders and numerical models

2012 Oceans ◽  
2012 ◽  
Author(s):  
W. Brown ◽  
W. Boicourt ◽  
C. Flagg ◽  
A. Gangopadhyay ◽  
O. Schofield ◽  
...  
Keyword(s):  
Numerical Models ◽  
Cold Pool

scholarly journals Radiation hydrodynamics simulations of the evolution of the diffuse ionized gas in disc galaxies

2019 ◽  
Vol 488 (2) ◽  
pp. 1977-1986 ◽  
Author(s):  
Bert Vandenbroucke ◽  
Kenneth Wood
Keyword(s):  
Pressure Support ◽  
Numerical Models ◽  
Fine Tuning ◽  
Radiation Budget ◽  
Radiation Hydrodynamics ◽  
Galactic Disc ◽  
Ionized Gas ◽  
Diffuse Ionized Gas ◽  
Gas Layer ◽  
Disc Galaxies

ABSTRACT There is strong evidence that the diffuse ionized gas (DIG) in disc galaxies is photoionized by radiation from UV luminous O and B stars in the galactic disc, both from observations and detailed numerical models. However, it is still not clear what mechanism is responsible for providing the necessary pressure support for a diffuse gas layer at kpc-scale above the disc. In this work, we investigate if the pressure increase caused by photoionization can provide this support. We run self-consistent radiation hydrodynamics (RHD) models of a gaseous disc in an external potential. We find that photoionization feedback can drive low levels of turbulence in the dense galactic disc, and that it provides pressure support for an extended diffuse gas layer. Our results show that there is a natural fine-tuning between the total ionizing radiation budget of the sources in the galaxy and the amount of gas in the different ionization phases of the interstellar medium, and provide the first fully consistent RHD model of the DIG.

Field and numerical investigation of the effect of under-sleeper pads on the dynamic behavior of railway bridges

2018 ◽  
Vol 232 (8) ◽  
pp. 2126-2137 ◽  
Author(s):  
Jaber Mottahed ◽  
Jabbar A Zakeri ◽  
Saeed Mohammadzadeh
Keyword(s):  
Numerical Investigation ◽  
Dynamic Behavior ◽  
Field Experiments ◽  
Bridge Deck ◽  
Numerical Models ◽  
Bridge Decks ◽  
Span Length ◽  
Railway Bridge ◽  
Railway Bridges ◽  
Northern District

There is a growing need to minimise vibrations of railway structures, especially the railway bridges, due to the increasing speed of trains. Various methods are used to reduce the effects of vibration on bridges. One of the methods is using under-sleeper pads. In this study, a real railway bridge – located in the northern district of Iran – with two spans and a free span length of 7 m was selected for the investigation of the effect of under-sleeper pads on the reduction of vibrations imposed on railway bridges. Field experiments – including the installation of an accelerometer to measure the accelerations beneath bridge decks, on the rail web, and next to the sleeper, and also the installation of Linear variable differential transformers (LVDTs) to measure the displacements of midspan point of bridge decks – were conducted. The effect of under-sleeper pads on the reduction of vibration accelerations, displacements, and moments of bridge midspan was investigated by developing numerical models of the bridge and validating its results through experimental outputs. The modeling predicts that the reduction of acceleration imposed on the deck in the first and second spans was different; the reduction effects in the first span were higher, where there was 58% reduction after using under-sleeper pads beneath the sleepers. There was a 15% decrease in the displacement of the bridge deck when under-sleeper pads are used. Similar results were obtained for the midspan moment of the bridge which reduced by 16%.

Modelling creep deformation in floating ice

2003 ◽  
Vol 30 (1) ◽  
pp. 28-41 ◽  
Author(s):  
K van Steenis ◽  
F E Hicks ◽  
T M Hrudey ◽  
S Beltaos
Keyword(s):  
Large Scale ◽  
Field Experiments ◽  
Numerical Models ◽  
Ice Sheet ◽  
Transversely Isotropic ◽  
Element Model ◽  
Ice Cover ◽  
Load Test ◽  
Drilling Rig

The ability to predict the response of an ice sheet to long-term loading is important in many situations. In northern regions, ice sheets have been used as construction platforms, drilling rig platforms, airfields, parking lots, and festival platforms. Numerical models can be used to predict the deflection of an ice sheet over time and, together with a failure criterion based on allowable deflection, can facilitate the safe use of an ice cover under long-term loading situations. In this study, a two-dimensional axisymmetric finite element model was developed to model the behaviour of a homogeneous, transversely isotropic, infinite ice cover under long-term loading. The model was validated using 33 sets of long-term load test data from large-scale field experiments performed on lake, bay, and reservoir ice and was shown to be capable of reliably predicting deflections under a variety of loading scenarios.Key words: bearing capacity of ice, long-term loading, ice platforms.

scholarly journals Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

2014 ◽  
Vol 7 (9) ◽  
pp. 2787-2805 ◽  
Author(s):  
L. K. Meredith ◽  
R. Commane ◽  
J. W. Munger ◽  
A. Dunn ◽  
J. Tang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Canopy ◽  
Trace Gases ◽  
Gradient Methods ◽  
Net Ecosystem Exchange ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Flux Gradient ◽  
Harvard Forest ◽  
Flux Measurements

Abstract. Our understanding of biosphere–atmosphere exchange has been considerably enhanced by eddy covariance measurements. However, there remain many trace gases, such as molecular hydrogen (H2), that lack suitable analytical methods to measure their fluxes by eddy covariance. In such cases, flux-gradient methods can be used to calculate ecosystem-scale fluxes from vertical concentration gradients. The budget of atmospheric H2 is poorly constrained by the limited available observations, and thus the ability to quantify and characterize the sources and sinks of H2 by flux-gradient methods in various ecosystems is important. We developed an approach to make nonintrusive, automated measurements of ecosystem-scale H2 fluxes both above and below the forest canopy at the Harvard Forest in Petersham, Massachusetts, for over a year. We used three flux-gradient methods to calculate the fluxes: two similarity methods that do not rely on a micrometeorological determination of the eddy diffusivity, K, based on (1) trace gases or (2) sensible heat, and one flux-gradient method that (3) parameterizes K. We quantitatively assessed the flux-gradient methods using CO2 and H2O by comparison to their simultaneous independent flux measurements via eddy covariance and soil chambers. All three flux-gradient methods performed well in certain locations, seasons, and times of day, and the best methods were trace gas similarity for above the canopy and K parameterization below it. Sensible heat similarity required several independent measurements, and the results were more variable, in part because those data were only available in the winter, when heat fluxes and temperature gradients were small and difficult to measure. Biases were often observed between flux-gradient methods and the independent flux measurements, and there was at least a 26% difference in nocturnal eddy-derived net ecosystem exchange (NEE) and chamber measurements. H2 fluxes calculated in a summer period agreed within their uncertainty and pointed to soil uptake as the main driver of H2 exchange at Harvard Forest, with H2 deposition velocities ranging from 0.04 to 0.10 cm s−1.

Seasonal variability of evapotranspiration in the central Andes of Peru using eddy covariance techniques and empirical methods

2020 ◽  
Author(s):  
Stephany Magaly Callañaupa Gutierrez ◽  
Hans Segura Cajachagua ◽  
Miguel Saavedra ◽  
Jose Flores ◽  
Joan Cuxart ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Sonic Anemometer ◽  
Strong Relationship ◽  
Mean Value ◽  
Dry Season ◽  
P Value ◽  
Wet Season ◽  
Peruvian Andes ◽  
Energy Limitation ◽  
Relationship Of

<p>In this study, the real evapotranspiration (ET) obtained using the eddy covariance (EC) technique from field crops located in the central Peruvian Andes (Huancayo Observatory, 12.04° S, 75.32°, 3350 msnm) is analyzed. Data from a sonic anemometer and a krypton hygrometer are used to estimate daily and monthly ET variability and to explore relationships with meteorological and surface variables. The results show that the mean value of daily evapotranspiration is estimated to be 3.45 mm/day during the wet season (January to March) while in the dry season (June to August) the value is 0.95 mm/day. In addition, linear regressions were used in order to evaluate the relationship of meteorological variables with evapotranspiration. As a result, solar radiation is the meteorological variable that has a strong relationship with evapotranspiration during the wet season (r2=0.76, p-value <0.005) and soil moisture during the dry season (r2=0.77, p-value <0.005). These results indicate a clear water-energy limitation depending on the season. Besides, the empirical evapotranspiration equations of FAO Penman-Monteith, Priestley-Taylor and Hargreaves were validated. Where the Priestley-Taylor equation is the empirical equation that best fits the observed data of evapotranspiration by EC (r2=0.70, p-value< 0.005).</p>

scholarly journals Performance Evaluation of an Integrated Open-Path Eddy Covariance System in a Cold Desert Environment

2016 ◽  
Vol 33 (11) ◽  
pp. 2385-2399 ◽  
Author(s):  
Wei Wang ◽  
Jiaping Xu ◽  
Yunqiu Gao ◽  
Ivan Bogoev ◽  
Jian Cui ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Eddy Covariance ◽  
Sonic Anemometer ◽  
Sensible Heat Flux ◽  
Winter Season ◽  
Populus Euphratica ◽  
Tarim River ◽  
Tarim River Basin ◽  
Gas Analyzer ◽  
Open Path

AbstractPerformance evaluation of an integrated eddy covariance (EC) instrument called the IRGASON, with a separated EC for reference, was conducted in a desert riparian Populus euphratica stand in the lower Tarim River basin in northwestern China. The separated EC consisted of an open-path gas analyzer and a sonic anemometer separated by 20 cm. The IRGASON integrates an open-path gas analyzer and a sonic anemometer into the same sensing volume, thus eliminating sensor separation in comparison to the traditional open-path EC setup. Integrating the infrared gas analyzer’s sensing head into the sensing volume of the sonic anemometer had negligible effects on wind speed and friction velocity observations of the IRGASON. Physiologically unreasonable daytime CO2 uptake was observed by both systems during the cold winter season (mean air temperature of −6.7°C), when the trees were dormant without any photosynthetic activities. The mean midday CO2 flux was −1.65 and −1.61 μmol m−2 s−1 for the IRGASON and the separated EC setup, respectively. No evidence was found for sensor self-heating as the cause of the apparent uptake CO2 flux. Instead, the uptake CO2 flux appeared to be an artifact of the spectroscopic effect of the IRGASON’s gas analyzer. After adjusting for this spectroscopic effect using a relationship with the sensible heat flux, the wintertime IRGASON CO2 flux became physiologically reasonable (mean value of −0.04 μmol m−2 s−1).

scholarly journals Synoptic-Scale Flow and Valley Cold Pool Evolution in the Western United States

2009 ◽  
Vol 24 (6) ◽  
pp. 1625-1643 ◽  
Author(s):  
Heather Dawn Reeves ◽  
David J. Stensrud
Keyword(s):  
United States ◽  
Large Scale ◽  
Numerical Models ◽  
Western United States ◽  
Cold Pool ◽  
Synoptic Scale ◽  
Temperature Changes ◽  
Cold Pools ◽  
Upper Level ◽  
Forecast Problem

Abstract Valley cold pools (VCPs), which are trapped, cold layers of air at the bottoms of basins or valleys, pose a significant problem for forecasters because they can lead to several forms of difficult-to-forecast and hazardous weather such as fog, freezing rain, or poor air quality. Numerical models have historically failed to routinely provide accurate guidance on the formation and demise of VCPs, making the forecast problem more challenging. In some case studies of persistent wintertime VCPs, there is a connection between the movement of upper-level waves and the timing of VCP formation and decay. Herein, a 3-yr climatology of persistent wintertime VCPs for five valleys and basins in the western United States is performed to see how often VCP formation and decay coincides with synoptic-scale (∼200–2000 km) wave motions. Valley cold pools are found to form most frequently as an upper-level ridge approaches the western United States and in response to strong midlevel warming. The VCPs usually last as long as the ridge is over the area and usually only end when a trough, and its associated midlevel cooling, move over the western United States. In fact, VCP strength appears to be almost entirely dictated by midlevel temperature changes, which suggests large-scale forcing is dominant for this type of VCP most of the time.

Ship Observations of the Tropical Pacific Ocean along the Coast of South America

2009 ◽  
Vol 22 (2) ◽  
pp. 458-464 ◽  
Author(s):  
S. P. de Szoeke ◽  
C. W. Fairall ◽  
Sergio Pezoa
Keyword(s):  
Field Experiments ◽  
Coastal Region ◽  
Warm Pool ◽  
Water Masses ◽  
Cold Pool ◽  
Radiative Fluxes ◽  
Pool Water ◽  
The North ◽  
Cloud Properties ◽  
Stratocumulus Clouds

Abstract In October 2007 the NOAA ship Ronald H. Brown sailed southward within 300 km of the coast of Ecuador and Peru, sampling surface meteorology, air–sea turbulent and radiative fluxes, cloud properties, and upper-air soundings from the equator to 20°S. Two distinct water masses characterize the coastal region: cold-pool water below 19°C in the Southern Hemisphere, and warm-pool water above 20°C to the north, with a transition between the water masses at 2.5°S. Net turbulent and radiative fluxes warm the cool water south of 2.5°S by 100 W m−2 but do not warm the equatorial water significantly. Winds blow parallel to the shore, about 5 m s−1 over the cold pool and 7 m s−1 over the equator. Stratocumulus clouds are remarkably solid over the coastal cold pool, with only brief periods of partial clearing, mostly in the afternoon. Lower aerosol concentrations and thicker clouds observed farther from the coast on 22–23 October are coincident with a pocket of open cells seen to the west and southwest of the ship. Observations from this cruise and other NOAA Stratus cruises (2001 and 2003–07) are suitable for comparison with model simulations and provide context for future field experiments. These datasets are publicly available.

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