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.

scholarly journals Turbulence measurements with a tethered balloon

2016 ◽  
Author(s):  
G. Canut ◽  
F. Couvreux ◽  
M. Lothon ◽  
D. Legain ◽  
B. Piguet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Convective Boundary Layer ◽  
Motion Sensor ◽  
Tethered Balloon ◽  
Inertial Motion ◽  
Convective Boundary ◽  
Momentum Fluxes ◽  
Field Campaigns

Abstract. This study presents the first deployment of a turbulence probe below a tethered balloon in field campaigns. This system allows to measure turbulent temperature fluxes, momentum fluxes as well as turbulent kinetic energy in the lower part of the boundary layer. It is composed of a sonic thermoanemometer and inertial motion sensor. It has been validated during three campaigns with different convective boundary layer conditions using turbulent measurements from atmospheric towers and aircraft.

scholarly journals A Method for Estimating the Turbulent Kinetic Energy Dissipation Rate from a Vertically Pointing Doppler Lidar, and Independent Evaluation from Balloon-Borne In Situ Measurements

2010 ◽  
Vol 27 (10) ◽  
pp. 1652-1664 ◽  
Author(s):  
Ewan J. O’Connor ◽  
Anthony J. Illingworth ◽  
Ian M. Brooks ◽  
Christopher D. Westbrook ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Sonic Anemometer ◽  
Horizontal Wind ◽  
Inertial Subrange ◽  
Doppler Velocity ◽  
Doppler Lidar ◽  
Convective Boundary ◽  
Dissipation Rates

Abstract A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ε can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.

scholarly journals Conceptual study on nucleation burst evolution in the convective boundary layer – Part IV: Comparison with previous observations

2005 ◽  
Vol 5 (6) ◽  
pp. 11557-11581
Author(s):  
O. Hellmuth
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Field Experiments ◽  
High Order ◽  
Convective Boundary ◽  
Vertical Fluxes ◽  
Physico Chemical ◽  
Modelling Studies ◽  
Conceptual Study

Abstract. In part I to III of the present paper a revised columnar high-order modelling approach to model gas-aerosol interactions in the convective boundary layer (CBL) was proposed, and simulation results of two nucleation scenarios (binary vs. ternary) on new particle formation (NPF) in the anthropogenically influenced CBL were presented. It was demonstrated that both scenarios strongly differ with respect to the amplitude and phase of the NPF burst detectable in the Prandtl layer, as well as with respect to the time-height evolution of turbulent vertical fluxes and double correlation terms of physico-chemical and aerosoldynamical variables. In the present part, an attempt is made to re-evaluate previous observations of NPF bursts in the CBL in view of the scenario simulations discussed in part III. Special attention is payed to the role of CBL turbulence in NPF burst evolution. At first, a compilation of empirical findings and hypothesis on NPF in the CBL derived from a number of field experiments, is performed. Secondly, it is demonstrated, that the binary scenario simulated in part III corresponds well to a number of NPF burst events observed in Hyytiälä (Finland) and Melpitz (Eastern Germany). Here, one of the key hypothesis on the role of turbulence in NPF is confirmed. Other NPF events, such as those observed at Hohenpeissenberg, a mountain site (Southern Germany), can not yet be conclusively explained. To note, that the results of previous box modelling studies to explain NPF events at Hohenpeissenberg are not unambiguous. Nonetheless, based on only two simulated scenarios it is demonstrated, that a columnar high-order model is a helpful tool to elucidate the genesis of NPF bursts frequently observed in the CBL. A comprehensive verification/validation study using observed high-order moments as well as further scenario simulations remain to be performed.

scholarly journals Using Commercial Aircraft Meteorological Data to Assess the Heat Budget of the Convective Boundary Layer Over the Santiago Valley in Central Chile

2022 ◽  
Author(s):  
Ricardo C. Muñoz ◽  
C. David Whiteman ◽  
René D. Garreaud ◽  
José A. Rutllant ◽  
Jacqueline Hidalgo
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Heat Budget ◽  
Meteorological Data ◽  
Sonic Anemometer ◽  
Sensible Heat Flux ◽  
Lower Troposphere ◽  
Commercial Aircraft ◽  
Convective Boundary ◽  
Central Chile

AbstractThe World Meteorological Organization Aircraft Meteorological Data Relay (AMDAR) programme refers to meteorological data gathered by commercial aircraft and made available to weather services. It has become a major source of upper-air observations whose assimilation into global models has greatly improved their performance. Near busy airports, AMDAR data generate semi-continuous vertical profiles of temperature and winds, which have been utilized to produce climatologies of atmospheric-boundary-layer (ABL) heights and general characterizations of specific cases. We analyze 2017–2019 AMDAR data for Santiago airport, located in the centre of a $$40\times 100$$ 40 × 100  km$$^2$$ 2 subtropical semi-arid valley in central Chile, at the foothills of the Andes. Profiles derived from AMDAR data are characterized and validated against occasional radiosondes launched in the valley and compared with routine operational radiosondes and with reanalysis data. The cold-season climatology of AMDAR temperatures reveals a deep nocturnal inversion reaching up to 700 m above ground level (a.g.l.) and daytime warming extending up to 1000 m a.g.l. Convective-boundary-layer (CBL) heights are estimated based on AMDAR profiles and the daytime heat budget of the CBL is assessed. The CBL warming variability is well explained by the surface sensible heat flux estimated with sonic anemometer measurements at one site, provided advection of the cool coastal ABL existing to the west is included. However, the CBL warming accounts for just half of the mean daytime warming of the lower troposphere, suggesting that rather intense climatological diurnal subsidence affects the dynamics of the daytime valley ABL. Possible sources of this subsidence are discussed.

scholarly journals Air and Surface Temperature Coupling in the Convective Atmospheric Boundary Layer

2011 ◽  
Vol 68 (12) ◽  
pp. 2945-2954 ◽  
Author(s):  
Anirban Garai ◽  
Jan Kleissl
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Coherent Structures ◽  
High Frequency ◽  
Spatial Scales ◽  
Temporal Correlation ◽  
Convective Boundary ◽  
Velocity Information ◽  
Thermal Signature ◽  
Practical Implications

Abstract In a convective boundary layer, coherent structures were detected through their thermal signature on an artificial turf surface using high-frequency thermal infrared (TIR) imagery and surface layer turbulence measurements. The coherent structures cause surface temperature variations over tens of seconds and spatial scales of tens to a few hundred meters. Evidence of processes similar to those in a renewal event was observed. Spatial and temporal correlation analysis revealed the geometric and velocity information of the structures at the ground footprint of air temperature measurements. The velocity of the coherent structures was consistent with the wind speed at 6.5 m AGL. Practical implications of turbulence-driven surface temperature variability for thermal remote sensing are also discussed.

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>

Observations of Sweep-Ejection Dynamics for Heat and Momentum Fluxes during Wildland Fires in Forested and Grassland Environments

2020 ◽  
Author(s):  
Warren E. Heilman ◽  
Tirtha Banerjee ◽  
Craig B. Clements ◽  
Kenneth L. Clark ◽  
Shiyuan Zhong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
Three Dimensional ◽  
Prescribed Fires ◽  
Turbulent Heat ◽  
Turbulent Transfer ◽  
Wildland Fires ◽  
Momentum Fluxes ◽  
Turbulence Data ◽  
The Mean

AbstractThe vertical turbulent transfer of heat and momentum in the lower atmospheric boundary layer is accomplished through intermittent sweep, ejection, outward interaction, and inward interaction events associated with turbulent updrafts and downdrafts. These events, collectively referred to as sweep-ejection dynamics, have been studied extensively in forested and non-forested environments and reported in the literature. However, little is known about the sweep-ejection dynamics that occur in response to turbulence regimes induced by wildland fires in forested and non-forested environments. This study attempts to fill some of that knowledge gap through analyses of turbulence data previously collected during three wildland (prescribed) fires that occurred in grassland and forested environments in Texas and New Jersey. Tower-based high-frequency (10 or 20 Hz) three-dimensional wind velocity and temperature measurements are used to examine frequencies of occurrence of sweep, ejection, outward interaction, and inward interaction events and their actual contributions to the mean vertical turbulent fluxes of heat and momentum before, during, and after the passage of fire fronts. The observational results suggest that wildland fires in these environments can substantially change the sweep-ejection dynamics for turbulent heat and momentum fluxes that typically occur when no fires are present, especially the relative contributions of sweeps compared to ejections in determining overall heat and momentum fluxes.

scholarly journals VALIDAÇÃO DO MODELO LES PALM POR MEIO DE DADOS DE RADIOSONDAGENS E DE AERONAVE COLETADOS DURANTE O EXPERIMENTO GOAMAZON

2016 ◽  
Vol 38 ◽  
pp. 34
Author(s):  
Thomas Kaufmann ◽  
Gilberto Fisch
Keyword(s):  
Boundary Layer ◽  
Observational Data ◽  
Convective Boundary Layer ◽  
Amazon Rainforest ◽  
Layer Depth ◽  
Convective Boundary ◽  
Late Afternoon ◽  
Dry Seasons ◽  
Field Campaigns ◽  
Wet And Dry Seasons

In the present study, the evolution of the convective boundary layer over heterogeneous surface simulated by PALM LES is validated with radiosounding and airborne data from GoAmazon field campaigns, held in Amazon Rainforest during the 2014 wet and dry seasons. It is shown that, in general case, the growth of the convective boundary layer simulated by PALM compares well with observational data. However, during the morning time, the convective boundary layer depth is underestimated, whereas it showed acceptable response to the decreasing of the surface forcings along the late afternoon.

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