Observational analysis of thermally-driven topographic flows and their turbulence-waves interaction

2020 ◽  
Author(s):  
Carlos Yagüe ◽  
Carlos Román-Cascón ◽  
Marie Lothon ◽  
Fabienne Lohou ◽  
Jon Ander Arrillaga ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Gravity Waves ◽  
Sonic Anemometer ◽  
Extended Period ◽  
Chem Phys ◽  
Small Scale ◽  
Mixing Ratios ◽  
Synoptic Conditions ◽  
Thermally Driven

<p>Thermally-driven flows (TDFs) are mesoscale circulations driven by horizontal thermal contrasts in scales ranging from 1 and 100-200 km. The presence of mountains can generate a kind of these TDFs called thermally-driven topographic flows, with a typical daily cycle which is observed when weak synoptic conditions are present. These flows impact the turbulence features in the Atmospheric Boundary Layer (ABL), as well as different scalars (temperature, CO<sub>2</sub>, water vapor, pollutants, etc.). Moreover, these circulations, which can be of different scales (from small-scale shallow drainage flows to for example the larger Mountain – Plain flows) can generate gravity waves (GWs) along the transition to the stable boundary layer (SBL) and during the night. In this work, 88 days belonging to an extended period of the BLLAST field campaign<sup>[1]</sup> have been analysed. The corresponding nocturnal TDFs have been detected through a systematic and objective algorithm which considers both synoptic and local meteorological conditions. The main objectives of the study are: to characterize the TDFs at CRA (which is placed on a plateau near the Pyrenees in France); to evaluate the performance of the objective algorithm<sup>[2]</sup> in obtaining the events of interest; to establish different categories of TDFs and search for driving mechanisms (local, synoptic,..); and finally to explore the connections between TDFs and the generation of Gravity Waves (GWs), often observed in the nocturnal SBL<sup>[3]</sup>. Their interaction with turbulence is also analysed using different multiscale techniques, such as wavelets applied to pressure measurements obtained from high accurate microbarometers, and MultiResolution Flux Decomposition –MRFD- applied to sonic anemometer data. The contribution of different scales to turbulent parameters will be deeply evaluated and related to the arrival of TDFs and to the presence of GWs.</p><p> </p><p>[1] Lothon, M., Lohou, F. et al (2014): The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence. <em>Atmos. Chem. Phys.</em>, <strong>14,</strong> 10931-10960.</p><p> [2] Román-Cascón, C., Yagüe, C., Arrillaga, J.A., Lothon, M., Pardyjak, E,R., Lohou, F., Inclán, R.M., Sastre, M., Maqueda, G., Derrien, S., Meyerfeld, Y., Hang, C., Campargue-Rodríguez, P. & Turki, I. (2019): Comparing mountain breezes and their impacts on CO2 mixing ratios at three contrasting areas. <em>Atmos. Res.</em>, <strong>221,</strong> 111-126.</p><p>[3] Sun, J., Nappo, C.J., Mahrt, L., Belusic, D., Grisogono, B., Stauffer, D.R., Pulido, M., Staquet, C., Jiang, Q., Pouquet, A., Yagüe, C. Galperin, B., Smith, R.B., Finnigan, J.J., Mayor, S.D., Svensson, G., Grachev, A.A. & Neff., W.D.: (2015): Review of wave-turbulence interactions in the stable atmospheric boundary layer, <em>Rev. Geophys.</em>, <strong>53,</strong> 956–993.</p>

Study of Thermal Activity in The Mixing Layer During First Generated Single Cloud by Using Combined Observation From Boundary Layer Radar, Doppler Lidar and Time Lapse Camera 

2021 ◽  
Author(s):  
Ginaldi Ari Nugroho ◽  
Kosei Yamaguchi ◽  
Eiichi Nakakita ◽  
Masayuki K. Yamamoto ◽  
Seiji Kawamura ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Atmospheric Boundary Layer ◽  
Vertical Velocity ◽  
Time Lapse ◽  
Small Scale ◽  
Thermal Activity ◽  
Doppler Lidar ◽  
Cumulus Cloud ◽  
Scale Perturbation

<p>Detailed observation of small scale perturbation in the atmospheric boundary layer during the first generated cumulus cloud are conducted. Our target is to study this small scale perturbation, especially related to the thermal activity at the first generated cumulus cloud. The observation is performed during the daytime on August 17, 2018, and September 03, 2018. Location is focused in the urban area of Kobe, Japan. High-resolution instruments such as Boundary Layer Radar, Doppler Lidar, and Time Lapse camera are used in this observation. Boundary Layer Radar, and Doppler Lidar are used for clear air observation. Meanwhile Time Lapse Camera are used for cloud existence observation. The atmospheric boundary layer structure is analyzed based on vertical velocity profile, variance, skewness, and estimated atmospheric boundary layer height. Wavelet are used to observe more of the period of the thermal activity. Furthermore, time correlation between vertical velocity time series from height 0.3 to 2 km and image pixel of generated cloud time series are also discussed in this study.</p>

The Effect of Internal Gravity Waves on Fluctuations in Meteorological Parameters of the Atmospheric Boundary Layer

2018 ◽  
Vol 54 (2) ◽  
pp. 173-181 ◽  
Author(s):  
D. V. Zaitseva ◽  
M. A. Kallistratova ◽  
V. S. Lyulyukin ◽  
R. D. Kouznetsov ◽  
D. D. Kuznetsov
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Gravity Waves ◽  
Meteorological Parameters ◽  
Internal Gravity Waves

scholarly journals Unmanned Aerial Systems for Investigating the Polar Atmospheric Boundary Layer—Technical Challenges and Examples of Applications

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 416 ◽  
Author(s):  
Astrid Lampert ◽  
Barbara Altstädter ◽  
Konrad Bärfuss ◽  
Lutz Bretschneider ◽  
Jesper Sandgaard ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Low Temperatures ◽  
Open Water ◽  
Future Research ◽  
Small Scale ◽  
Unmanned Aerial Systems ◽  
Research Activities ◽  
Aerial Systems ◽  
The Impact

Unmanned aerial systems (UAS) fill a gap in high-resolution observations of meteorological parameters on small scales in the atmospheric boundary layer (ABL). Especially in the remote polar areas, there is a strong need for such detailed observations with different research foci. In this study, three systems are presented which have been adapted to the particular needs for operating in harsh polar environments: The fixed-wing aircraft M 2 AV with a mass of 6 kg, the quadrocopter ALICE with a mass of 19 kg, and the fixed-wing aircraft ALADINA with a mass of almost 25 kg. For all three systems, their particular modifications for polar operations are documented, in particular the insulation and heating requirements for low temperatures. Each system has completed meteorological observations under challenging conditions, including take-off and landing on the ice surface, low temperatures (down to −28 ∘ C), icing, and, for the quadrocopter, under the impact of the rotor downwash. The influence on the measured parameters is addressed here in the form of numerical simulations and spectral data analysis. Furthermore, results from several case studies are discussed: With the M 2 AV, low-level flights above leads in Antarctic sea ice were performed to study the impact of areas of open water within ice surfaces on the ABL, and a comparison with simulations was performed. ALICE was used to study the small-scale structure and short-term variability of the ABL during a cruise of RV Polarstern to the 79 ∘ N glacier in Greenland. With ALADINA, aerosol measurements of different size classes were performed in Ny-Ålesund, Svalbard, in highly complex terrain. In particular, very small, freshly formed particles are difficult to monitor and require the active control of temperature inside the instruments. The main aim of the article is to demonstrate the potential of UAS for ABL studies in polar environments, and to provide practical advice for future research activities with similar systems.

scholarly journals Modulation of Small-Scale Turbulence by Ducted Gravity Waves in the Nocturnal Boundary Layer

2008 ◽  
Vol 65 (4) ◽  
pp. 1414-1427 ◽  
Author(s):  
Y. P. Meillier ◽  
R. G. Frehlich ◽  
R. M. Jones ◽  
B. B. Balsley
Keyword(s):  
Boundary Layer ◽  
Gravity Waves ◽  
Richardson Number ◽  
Potential Temperature ◽  
Nocturnal Boundary Layer ◽  
Small Scale ◽  
Temperature Structure ◽  
Turbulence Measurements ◽  
Gradient Richardson Number ◽  
Scale Turbulence

Abstract Constant altitude measurements of temperature and velocity in the residual layer of the nocturnal boundary layer, collected by the Cooperative Institute for Research in Environmental Sciences (CIRES) Tethered Lifting System (TLS), exhibit fluctuations identified by previous work (Fritts et al.) as the signature of ducted gravity waves. The concurrent high-resolution TLS turbulence measurements (temperature structure constant C2T and turbulent kinetic energy dissipation rate ɛ) reveal the presence of patches of enhanced turbulence activity that are roughly synchronized with the troughs of the temperature and velocity fluctuations. To investigate the potentially dominant role ducted gravity waves might play on the modulation of atmospheric stability and therefore, on turbulence, time series of the wave-modulated gradient Richardson number (Ri) and of the vertical gradient of potential temperature ∂θ/∂z(t) are computed numerically and compared to the TLS small-scale turbulence measurements. The results of this study agree with the predictions of previous theoretical studies (i.e., wave-generated fluctuations of temperature and velocity modulate the gradient Richardson number), resulting in periodic enhancements of turbulence at Ri minima. The patches of turbulence observed in the TLS dataset are subsequently identified as convective instabilities generated locally within the unstable phase of the wave.

Microphysics of the air-sea coupling at high winds and its role in the dynamics and thermodynamics of severe sea storms

2020 ◽  
Author(s):  
Yuliya Troitskaya ◽  
Alexander Kandaurov ◽  
Daniil Sergeev ◽  
Olga Ermakova ◽  
Dmitrii Kozlov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Water Surface ◽  
Synergetic Effect ◽  
Ocean Surface ◽  
Small Scale ◽  
Momentum Exchange ◽  
Momentum Fluxes ◽  
The Impact ◽  
High Winds

<p>Showing the record strengths and growth-rates, a number of recent hurricanes have highlighted needs for improving forecasts of tropical cyclone intensities most sensitive to models of the air-sea coupling. Especially challenging is the nature and effect of the very small-scale phenomena, the sea-spray and foam, supposed to strongly affecting the momentum- and heat- air-sea fluxes at strong winds. This talk will focus on our progress in understanding and describing these "micro-scale" processes, their physical properties, the spray and foam mediated air-sea fluxes and the impact on the development of marine storms.</p><p>The starting points for this study were two laboratory experiments. The first one was designed for investigation of the spray generation mechanisms at high winds. We found out 3 dominant spray generating mechanisms: stretching liquid ligaments, bursting bubbles, splashing of the falling droplets and "bag-breakup". We investigated the efficiency spray-production mechanisms and developed the empirical statistics of the numbers of the spray generating events of each type. Basing on the "white-cap method" we found out the dependence of the spray-generating events on the wind fetch. The main attention was paid to the "bag-breakup" mechanism. Here we studied in detail the statistics of spray produced from one "bag-breakup" event. Basing on these developments, we estimated heat and momentum fluxes from the spray-generating events of different types and found out the dominant role of the "bag-breakup" mechanism.</p><p>To estimate the direct heat and momentum fluxes from the ocean surface to the atmosphere, we studied in the special experiment the foam impact on the short-wave part of the surface waves and the heat momentum exchange in the atmospheric boundary layer at high winds. Based on these results, we suggest a simple model for the aerodynamic and temperature roughness and the eddy viscosity in the turbulent boundary layer over a fractionally foam-covered water surface.</p><p>The synergetic effect of foam at the water surface and spray in the marine atmospheric boundary layer on ocean surface resistance at high winds is estimated so as to be able to explain the observed peculiarities of the air-sea fluxes at stormy conditions. Calculations within the nonhydrostatic axisymmetric model show, that the "microphysics" of the air-sea coupling significantly accelerate development of the ocean storm.</p><p>This work was supported by RFBR grant 19-05-00249 and RSF grant 19-17-00209.</p>

scholarly journals Small-Scale Variability in the Coastal Atmospheric Boundary Layer

1998 ◽  
Vol 88 (1) ◽  
pp. 23-46 ◽  
Author(s):  
Branko Grisogono ◽  
Linda Ström ◽  
Michael Tjernström
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Small Scale

scholarly journals Nitrogen oxides in the boundary layer and free troposphere at the Mt. Bachelor Observatory

2010 ◽  
Vol 10 (13) ◽  
pp. 6043-6062 ◽  
Author(s):  
D. R. Reidmiller ◽  
D. A. Jaffe ◽  
E. V. Fischer ◽  
B. Finley
Keyword(s):  
Boundary Layer ◽  
North America ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Transport Pathways ◽  
North American Continent ◽  
Mixing Ratios ◽  
The North ◽  
Synoptic Conditions ◽  
The Difference

Abstract. Nitrogen oxide (NOx=NO+NO2) observations were made at the Mt. Bachelor Observatory in central Oregon, USA (MBO; 2.73 km above sea level) during one autumn and three springtime (15 April–20 May) periods. This is the first study to discuss interannual variability in NOx for this region. NOx concentrations (mean±1σ) for spring 2007, 2008 and 2009 were 119±65, 117±65, and 91±54 pptv, respectively. The difference in mean mixing ratios between 2007 and 2008 is not statistically significant, whereas the difference between these years and 2009 is significant (p<0.01). We attribute the decline in NOx from 2007–2008 to 2009 to changes in free tropospheric synoptic conditions over the Northeast Pacific and trans-Pacific transport pathways during spring 2009. In 2009, there were: (1) higher geopotential heights over the Gulf of Alaska, (2) warmer temperatures over the Aleutian Islands/Gulf of Alaska and (3) much weaker winds throughout the North Pacific. During the autumn 2008 campaign, NOx concentrations (mean±1σ) were 175±548 pptv. The highly non-normal distribution of data (skewness coefficient of 19.1 vs. 2.5, 2.8 and 2.4 in spring 2007, 2008 and 2009, respectively) resulted from periods of very high NOx levels. Using MODIS Rapid Response (Aqua and Terra) results, we show that during autumn our site can be heavily influenced by wildfires in western North America. This is in contrast to springtime, when the smaller positive (i.e., right) tail of the NOx distribution is driven largely by Asian long-range transport (ALRT) events. We developed a novel means of segregating boundary layer (BL)-influenced vs. free tropospheric (FT) air. During spring 2008 we collected "chairlift soundings" of temperature, relative humidity and pressure in an effort to better understand the diurnal pattern of a BL influence at our summit station. Results from this experiment revealed that, on average, a BL influence begins around 10:00 PDT (UTC – 07:00 h) in spring. Using this information to isolate FT air, we characterize probable pollution sources and synoptic conditions for the top 20 FT NOx events over three spring campaigns. Half (n=10) of these 20 events were determined to be "Imported" events characterized by anomalously: (1) high geopotential heights off the west coast of North America, (2) warm temperatures stretching from the Aleutian Islands to Baja California, and (3) strong southwesterly winds in the Asian outflow region. Five events exhibited an influence from the North American continent. These events are characterized by very strong cyclonic behavior off the northwestern USA coast.

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