scholarly journals Comparisons between Mean and Turbulent Parameters of Aircraft-Based and Ship-Based Measurements in the Marine Atmospheric Boundary Layer

Atmosphere ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1088
Author(s):  
Min-Seong Kim ◽  
Byung Hyuk Kwon ◽  
Tae-Young Goo
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Atmospheric Boundary Layer ◽  
Radiation Flux ◽  
Sensible Heat Flux ◽  
Surface Flux ◽  
Marine Atmospheric Boundary Layer ◽  
The Mean ◽  
Good Agreement

The Structure des Echanges Mer-Atmosphère, Propriétés Océaniques/ Recherche Expérimentale (SEMAPHORE) experiment was conducted over the oceanic Azores current located in the Azores Basin. The evolution of the marine atmospheric boundary layer (MABL) was studied based on the evaluation of mean and turbulent data using in situ measurements by a ship and two aircrafts. The sea surface temperature (SST) field was characterized by a gradient of approximately 1 °C/100 km. The SST measured by aircraft decreased at a ratio of 0.25 °C/100 m of altitude due to the divergence of the infrared radiation flux from the surface. With the exception of temperature, the mean parameters measured by the two aircrafts were in good agreement with each other. The sensible heat flux was more dispersed than the latent heat flux according to the comparisons between aircraft and aircraft, and aircraft and ship. This study demonstrates the feasibility of using two aircraft to describe the MABL and surface flux with confidence.

scholarly journals Observation of sensible and latent heat flux profiles with lidar

2020 ◽  
Vol 13 (6) ◽  
pp. 3221-3233 ◽  
Author(s):  
Andreas Behrendt ◽  
Volker Wulfmeyer ◽  
Christoph Senff ◽  
Shravan Kumar Muppa ◽  
Florian Späth ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Ground Level ◽  
Sensible Heat ◽  
Flux Divergence ◽  
Convective Boundary ◽  
The Mean

Abstract. We present the first measurement of the sensible heat flux (H) profile in the convective boundary layer (CBL) derived from the covariance of collocated vertical-pointing temperature rotational Raman lidar and Doppler wind lidar measurements. The uncertainties of the H measurements due to instrumental noise and limited sampling are also derived and discussed. Simultaneous measurements of the latent heat flux profile (L) and other turbulent variables were obtained with the combination of water-vapor differential absorption lidar (WVDIAL) and Doppler lidar. The case study uses a measurement example from the HOPE (HD(CP)2 Observational Prototype Experiment) campaign, which took place in western Germany in 2013 and presents a cloud-free well-developed quasi-stationary CBL. The mean boundary layer height zi was at 1230 m above ground level. The results show – as expected – positive values of H in the middle of the CBL. A maximum of (182±32) W m−2, with the second number for the noise uncertainty, is found at 0.5 zi. At about 0.7 zi, H changes sign to negative values above. The entrainment flux was (-62±27) W m−2. The mean sensible heat flux divergence in the observed part of the CBL above 0.3 zi was −0.28 W m−3, which corresponds to a warming of 0.83 K h−1. The L profile shows a slight positive mean flux divergence of 0.12 W m−3 and an entrainment flux of (214±36) W m−2. The combination of H and L profiles in combination with variance and other turbulent parameters is very valuable for the evaluation of large-eddy simulation (LES) results and the further improvement and validation of turbulence parameterization schemes.

scholarly journals Observed Variations of the Atmospheric Boundary Layer and Stratocumulus over a Warm Eddy in the Kuroshio Extension

2019 ◽  
Vol 147 (5) ◽  
pp. 1581-1591 ◽  
Author(s):  
Qian Wang ◽  
Su-Ping Zhang ◽  
Shang-Ping Xie ◽  
Joel R. Norris ◽  
Jian-Xiang Sun ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Atmospheric Boundary Layer ◽  
Kuroshio Extension ◽  
Atmospheric Model ◽  
Low Pressure ◽  
Marine Atmospheric Boundary Layer ◽  
Warm Eddy ◽  
Lifting Condensation Level ◽  
The Kuroshio

Abstract A research vessel sailing across a warm eddy in the Kuroshio Extension on 13 April 2016 captured an abrupt development of stratocumulus under synoptic high pressure. Shipboard observations and results from regional atmospheric model simulations indicate that increased surface heat flux over the ocean eddy lowered surface pressure and thereby accelerated southeasterly winds. The southeasterly winds transported moisture toward the low pressure and enhanced the air–sea interface heat flux, which in turn deepened the low pressure and promoted low-level convergence and rising motion over the warm eddy. The lifting condensation level lowered and the top of the marine atmospheric boundary layer (MABL) rose, thereby aiding the development of the stratocumulus. Further experiments showed that 6°C sea surface temperature anomalies associated with the 400-km-diameter warm eddy accounted for 80% of the total ascending motion and 95% of total cloud water mixing ratio in the marine atmospheric boundary layer during the development of stratocumulus. The synthesis of in situ soundings and modeling contributes to understanding of the mechanism by which the MABL and marine stratocumulus respond to ocean eddies.

scholarly journals Wind Regimes And Heat Exchange On Glacier De Saint-Sorlin

1975 ◽  
Vol 14 (70) ◽  
pp. 91-105 ◽  
Author(s):  
S. Martin
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Radiation Flux ◽  
Sensible Heat Flux ◽  
Radiation Balance ◽  
Katabatic Flow ◽  
Wind Regimes ◽  
Wind Profiles ◽  
Glacier Wind ◽  
Good Agreement

During the summers of 1969 and 1970, we recorded in the ablation zone of the Glacier de St-Sorlin (Massif des Grandes Rousses, France) temperature, air moisture, and wind profiles, as well as the radiation balance and the daily ablation. Numerous profiles characterize a katabatic flow following the line of greatest slope, and there appears to be a correlation between the speed of the “glacier wind” and the corresponding temperature gradients. Computed according to Prandtl’s theory of turbulent transfers, the flux of sensible and latent heat added to the radiation flux leads to theoretical values for the daily melting in good agreement with the measured values. The relative importance of the radiation balance on the melting of the snow is 57%; that of the sensible heat flux is 43%; the latent heat flux is very weak and negative.

scholarly journals Estimation of Sensible Heat Flux and Atmospheric Boundary Layer Height Using an Unmanned Aerial Vehicle

Atmosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 363 ◽  
Author(s):  
Min-Seong Kim ◽  
Byung Hyuk Kwon
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Unmanned Aerial Vehicle ◽  
Sensible Heat Flux ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Aerial Vehicle ◽  
Transfer Method

In this work, sensible heat flux estimated using a bulk transfer method was validated with a three-dimensional ultrasonic anemometer or surface layer scintillometer at various sites. Results indicate that it remains challenging to obtain temperature and wind speed at an appropriate reference height. To overcome this, alternative observations using an unmanned aerial vehicle (UAV) were considered. UAV-based wind speed and sensible heat flux were indirectly estimated and atmospheric boundary layer (ABL) height was then derived using the sensible heat flux data. UAV-observed air temperature was measured by attaching a temperature sensor 40 cm above the rotary-wing of the UAV, and UAV-based wind speed was estimated using attitude data (pitch, roll, and yaw angles) recorded using the UAV’s inertial measurement unit. UAV-based wind speed was close to the automatic weather system-observed wind speed, within an error range of approximately 10%. UAV-based sensible heat flux estimated from the bulk transfer method corresponded with sensible heat flux determined using the eddy correlation method, within an error of approximately 20%. A linear relationship was observed between the normalized UAV-based sensible heat flux and radiosonde-based normalized ABL height.

scholarly journals Wind Regimes And Heat Exchange On Glacier De Saint-Sorlin

1975 ◽  
Vol 14 (70) ◽  
pp. 91-105 ◽  
Author(s):  
S. Martin
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Radiation Flux ◽  
Sensible Heat Flux ◽  
Radiation Balance ◽  
Katabatic Flow ◽  
Wind Regimes ◽  
Wind Profiles ◽  
Glacier Wind ◽  
Good Agreement

During the summers of 1969 and 1970, we recorded in the ablation zone of the Glacier de St-Sorlin (Massif des Grandes Rousses, France) temperature, air moisture, and wind profiles, as well as the radiation balance and the daily ablation. Numerous profiles characterize a katabatic flow following the line of greatest slope, and there appears to be a correlation between the speed of the “glacier wind” and the corresponding temperature gradients. Computed according to Prandtl’s theory of turbulent transfers, the flux of sensible and latent heat added to the radiation flux leads to theoretical values for the daily melting in good agreement with the measured values. The relative importance of the radiation balance on the melting of the snow is 57%; that of the sensible heat flux is 43%; the latent heat flux is very weak and negative.

scholarly journals Atmospheric Flow Development and Associated Changes in Turbulent Sensible Heat Flux over a Patchy Mountain Snow Cover

2015 ◽  
Vol 16 (3) ◽  
pp. 1315-1340 ◽  
Author(s):  
Rebecca Mott ◽  
Megan Daniels ◽  
Michael Lehning
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Energy Balance ◽  
Snow Cover ◽  
Sensible Heat Flux ◽  
Ambient Air ◽  
Small Scale ◽  
Sensible Heat ◽  
Katabatic Winds ◽  
The Mean

Abstract In this study, the small-scale boundary layer dynamics and the energy balance over a fractional snow cover are numerically investigated. The atmospheric boundary layer flows over a patchy snow cover were calculated with an atmospheric model (Advanced Regional Prediction System) on a very high spatial resolution of 5 m. The numerical results revealed that the development of local flow patterns and the relative importance of boundary layer processes depend on the snow patch size distribution and the synoptic wind forcing. Energy balance calculations for quiescent wind situations demonstrated that well-developed katabatic winds exerted a major control on the energy balance over the patchy snow cover, leading to a maximum in the mean downward sensible heat flux over snow for high snow-cover fractions. This implies that if katabatic winds develop, total melt of snow patches may decrease for low snow-cover fractions despite an increasing ambient air temperature, which would not be predicted by most hydrological models. In contrast, stronger synoptic winds increased the effect of heat advection on the catchment’s melt behavior by enhancing the mean sensible heat flux over snow for lower snow-cover fractions. A sensitivity analysis to grid resolution suggested that the grid size is a critical factor for modeling the energy balance of a patchy snow cover. The comparison of simulation results from coarse (50 m) and fine (5 m) horizontal resolutions revealed a difference in the spatially averaged turbulent heat flux over snow of 40%–70% for synoptic cases and 95% for quiescent cases.

scholarly journals Characteristics of the summer atmospheric boundary layer height over the Tibetan Plateau and influential factors

2020 ◽  
Author(s):  
Junhui Che ◽  
Ping Zhao
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Tibetan Plateau ◽  
Solar Radiation ◽  
Atmospheric Boundary Layer ◽  
Sensible Heat Flux ◽  
Influential Factors ◽  
The Tibetan Plateau ◽  
Height Distribution ◽  
Sensible Heat

Abstract. Based on intensive sounding, surface sensible heat flux, solar radiation, and soil moisture observational datasets from the Third Tibetan Plateau Atmospheric Scientific Experiment and the routine meteorological operational sounding and total cloudiness datasets in the Tibetan Plateau (TP) for the period 2013–2015, we investigate the features of summer atmospheric boundary layer (ABL) over the TP and its major influential factors. It is found that the convective boundary layer (CBL) and the neutral boundary layer (NBL) show remarkable diurnal variations over the TP, while the stable boundary layer (SBL) diurnal variation is weak. In the early morning, the ABL height distribution is narrow, with a small west-east difference. The SBL accounts for 85 % of the TP ABL. At noon, there is a wide distribution in the ABL height up to 4000 m. The CBL accounts for 77 % of the TP ABL, with more than 50 % of the CBL height above 1900 m. The ABL height exhibits a large west-east difference, with a mean height above 2000 m in the western TP and around 1500 m in the eastern TP. In the late afternoon, the CBL and SBL dominate the western and eastern TP, respectively, resulting in a larger west-east difference of 1054.2 m between the western and eastern TP. The high ABL height in a cold environment over the western TP (relative to the plain areas) is similar to that in some extreme hot and arid areas such as Dunhuang and Taklimakan Deserts. For the western (eastern) TP, there is low (high) total cloud coverage, with large (small) solar radiation at the surface and dry (wet) soil. These features result in high (low) sensible heat flux and thus promotes (inhibits) the local ABL development.

scholarly journals The Effects of Mesoscale Surface Heterogeneity on the Fair-Weather Convective Atmospheric Boundary Layer

2008 ◽  
Vol 65 (10) ◽  
pp. 3197-3213 ◽  
Author(s):  
Song-Lak Kang ◽  
Kenneth J. Davis
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Atmospheric Boundary Layer ◽  
Sensible Heat Flux ◽  
Surface Heterogeneity ◽  
High Amplitude ◽  
Steady Flows ◽  
Heterogeneous Surfaces ◽  
Lower Amplitude ◽  
The Impact

Large-eddy simulation (LES) is used to examine the impact of heterogeneity in the surface energy balance on the mesoscale and microscale structure of the convective atmospheric boundary layer (ABL). A long (16 or 32 km) and narrow (5 km) domain of the convective ABL is forced with an imposed surface heat flux consisting of a constant background flux of 0.20 K m s−1 (250 W m−2) added to a sinusoidal perturbation of 16 or 32 km and whose amplitude varies from 0.02 to 0.20 K m s−1 (25–250 W m−2). The output is analyzed using a spatial filter, spectral analyses, and a wave-cutoff filter to show how the mesoscale and microscale components of the ABL respond to surface heterogeneity. The ABL response is divided by amplitude of heterogeneity into oscillatory and nonoscillatory mesoscale flows, with amplitudes of 0.08 K m s−1 (100 W m−2) and greater being oscillatory. Although mean ABL structure is disturbed relative to the homogeneous case for all heterogeneous cases, the microscale structure of the ABL in the quasi-steady flows retains characteristics of mixed-layer similarity. The vertical sensible heat flux is dominated in all cases by the microscale flux, with an interscale term becoming significant for high-amplitude cases and the mesoscale flux remaining small in all cases. Prior observations of ABLs over heterogeneous surfaces are consistent with the lower-amplitude cases. These results contradict past studies that suggest that heterogeneous surfaces lead to large mesoscale fluxes. The interscale flux and oscillatory microscale structures raise questions about the ability of mesoscale models to properly simulate the ABL in high-amplitude heterogeneity.

scholarly journals Observation of sensible and latent heat flux profiles with lidar

2019 ◽  
Author(s):  
Andreas Behrendt ◽  
Volker Wulfmeyer ◽  
Christoph Senff ◽  
Shravan Kumar Muppa ◽  
Florian Späth ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Ground Level ◽  
Sensible Heat ◽  
Flux Divergence ◽  
Convective Boundary ◽  
The Mean

Abstract. We present the first measurement of the sensible heat flux (H) profile in the convective boundary layer (CBL) derived from the covariance of collocated vertical-pointing temperature rotational Raman lidar and Doppler wind lidar measurements. The uncertainties of the H measurements due to instrumental noise and limited sampling are also derived and discussed. Simultaneous measurements of the latent heat flux profile (L) and other turbulent variables were obtained with the combination of water-vapor DIAL and Doppler lidar. The measurement example is from the HOPE campaign, which took place in western Germany in 2013 and presents a cloud-free well-developed quasi-stationary CBL. The mean boundary layer height z_i was at 1230 m above ground level. The results show – as expected – positive values of H in the middle of the CBL. A maximum of (182 ± 32) W/m2, with the second number for the noise uncertainty, is found at 0.5 z_i. At about 0.7 z_i, H changes sign to negative values above. The entrainment flux was (−62 ± 27) W/m2. The mean sensible heat flux divergence in the observed part of the CBL above 0.3 z_i was −0.28 W/m3, which corresponds to a warming of 0.83 K/h. The L profile shows a slight positive mean flux divergence of 0.12 W/m3 and an entrainment flux of (214 ± 36) W/m2. The combination of H and L profiles in combination with variance and other turbulent parameters is very valuable for the evaluation of large-eddy simulation (LES) results and the further improvement and validation of turbulence parameterization schemes.

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