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 Development of an Unmanned Aerial Vehicle for the Measurement of Turbulence in the Atmospheric Boundary Layer

Atmosphere ◽  
2017 ◽  
Vol 8 (10) ◽  
pp. 195 ◽  
Author(s):  
Brandon Witte ◽  
Robert Singler ◽  
Sean Bailey
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Unmanned Aerial Vehicle ◽  
Sensor Data ◽  
Velocity Sensor ◽  
Aerial Vehicle ◽  
Probe Velocity ◽  
Convective State ◽  
Using Data

This paper describes the components and usage of an unmanned aerial vehicle developed for measuring turbulence in the atmospheric boundary layer. A method of computing the time-dependent wind speed from a moving velocity sensor data is provided. The physical system built to implement this method using a five-hole probe velocity sensor is described along with the approach used to combine data from the different on-board sensors to allow for extraction of the wind speed as a function of time and position. The approach is demonstrated using data from three flights of two unmanned aerial vehicles (UAVs) measuring the lower atmospheric boundary layer during transition from a stable to convective state. Several quantities are presented and show the potential for extracting a range of atmospheric boundary layer statistics.

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 Environmental Conditions Associated with Horizontal Convective Rolls, Cellular Convection, and No Organized Circulations

2021 ◽  
Author(s):  
Sean R. Santellanes ◽  
George S. Young ◽  
David J. Stensrud ◽  
Matthew R. Kumjian ◽  
Ying Pan
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Discriminant Analysis ◽  
Wind Speed ◽  
Environmental Conditions ◽  
Environmental Variables ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Linear Discriminant ◽  
Convective Rolls

AbstractTypical environmental conditions associated with horizontal convective rolls (HCRs) and cellular convection have been known for over 50 years. Yet our ability to predict whether HCRs, cellular convection, or no discernable organized (null) circulation will occur within a well-mixed convective boundary layer based upon easily observed environmental variables has been limited. Herein, a large data base of 50 cases each of HCR, cellular convection, and null events is created that includes observations of mean boundary layer wind and wind shear, boundary layer depth, and surface observations of wind, temperature, relative humidity, and estimates of surface sensible heat flux. Results from a multi-class linear discriminant analysis applied to these data indicate that environmental conditions can be useful in predicting whether HCRs, cellular convection, or no circulation occurs, with the analysis identifying the correct circulation type on 72% of the case days. This result is slightly better than using a mean CBL wind speed of 6 m s-1 to discriminate between HCRs and cells. However, the mean CBL wind speed has no ability to further separate out cases with no CBL circulation. The key environmental variables suggested by the discriminant analysis are mean sensible heat flux, friction velocity, and the Obukhov length.

scholarly journals Lidar Measurement of Boundary Layer Evolution to Determine Sensible Heat Fluxes

2005 ◽  
Vol 6 (6) ◽  
pp. 840-853 ◽  
Author(s):  
W. E. Eichinger ◽  
H. E. Holder ◽  
R. Knight ◽  
J. Nichols ◽  
D. I. Cooper ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Potential Temperature ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
High Time Resolution ◽  
Lidar Measurement ◽  
Sensible Heat ◽  
Creek Watershed

Abstract The Soil Moisture–Atmosphere Coupling Experiment (SMACEX) was conducted in the Walnut Creek watershed near Ames, Iowa, over the period from 15 June to 11 July 2002. A main focus of SMACEX is the investigation of the interactions between the atmospheric boundary layer, surface moisture, and canopy. A vertically staring elastic lidar was used to provide a high-time-resolution continuous record of the boundary layer height at the edge between a soybean and cornfield. The height and thickness of the entrainment zone are used to estimate the surface sensible heat flux using the Batchvarova–Gryning boundary layer model. Flux estimates made over 6 days are compared to conventional eddy correlation measurements. The calculated values of the sensible heat flux were found to be well correlated (R2 = 0.79, with a slope of 0.95) when compared to eddy correlation measurements in the area. The standard error of the flux estimates was 21.4 W m−2 (31% rms difference between this method and surface measurements), which is somewhat higher than a predicted uncertainty of 16%. The major sources of error were from the estimates of the vertical potential temperature gradient and an assumption that the entrainment parameter A was equal to the ratio of the entrainment flux and the surface heat flux.

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

2021 ◽  
Vol 21 (7) ◽  
pp. 5253-5268
Author(s):  
Junhui Che ◽  
Ping Zhao
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Tibetan Plateau ◽  
Solar Radiation ◽  
Atmospheric Boundary Layer ◽  
Diurnal Variation ◽  
Sensible Heat Flux ◽  
Influential Factors ◽  
The Tibetan Plateau ◽  
Sensible Heat

Abstract. The important roles of the Tibetan Plateau (TP) atmospheric boundary layer (ABL) in climate, weather, and air quality have long been recognized, but little is known about the TP ABL climatological features and their west–east discrepancies due to the scarce data in the western TP. Based on observational datasets of intensive sounding, surface sensible heat flux, solar radiation, and soil moisture from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III) and the routine meteorological-operational-sounding and ground-based cloud cover datasets in the Tibetan Plateau for the period 2013–2015, we investigate the west–east differences in summer ABL features over the TP and the associated influential factors for the first time. It is found that the heights of both the convective boundary layer (CBL) and the neutral boundary layer (NBL) exhibit a diurnal variation and a west–east difference in the TP, while these features are not remarkable for the stable boundary layer (SBL). Moreover, the ABL shows significant discrepancies in the amplitude of the diurnal variation and the persistent time of the development between the eastern and western TP. In the early morning (08:00 BJT, Beijing time), the ABL height distribution is narrow, with a mean height below 450 m a.g.l. (above ground level) and a small west–east difference. The SBL observed at this moment accounts for 85 % of the total TP ABL. There is a wide distribution in the ABL height up to 4000 m a.g.l. and a large west–east difference for the total ABL height at noon (14:00 BJT), with a mean height above 2000 m a.g.l. in the western TP and around 1500 m a.g.l. in the eastern TP. The CBL accounts for 77 % of the total TP ABL at this moment, with more than 50 % of the CBL above 1900 m a.g.l. In the late afternoon (20:00 BJT), the CBL and SBL dominate the western and eastern TP, respectively, which results 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. In general, 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 lead to high (low) sensible heat flux and thus promote (inhibit) the local ABL development. This study provides new insights for west–east structures of the summer ABL height, occurrence frequency, and diurnal amplitude over the TP region and the associated reasons.

scholarly journals The impact of broadleaved woodland on water resources in lowland UK: II. Evaporation estimates from sensible heat flux measurements over beech woodland and grass on chalk sites in Hampshire

2005 ◽  
Vol 9 (6) ◽  
pp. 607-613 ◽  
Author(s):  
J. Roberts ◽  
P. Rosier ◽  
D. M. Smith
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Excellent Agreement ◽  
Sensible Heat Flux ◽  
Late Summer ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Flux Measurements ◽  
Shallow Soils ◽  
The Impact

Abstract. The impact on recharge to the Chalk aquifer of substitution of broadleaved woodland for pasture is a matter of concern in the UK. Hence, measurements of energy balance components were made above beech woodland and above pasture, both growing on shallow soils over chalk in Hampshire. Latent heat flux (evaporation) was calculated as the residual from these measurements of energy balances in which sensible heat flux was measured with an eddy correlation instrument that determined fast response vertical wind speeds and associated temperature changes. Assessment of wind turbulence statistics confirmed that the eddy correlation device performed satisfactorily in both wet and dry conditions. There was excellent agreement between forest transpiration measurements made by eddy correlation and stand level tree transpiration measured with sap flow devices. Over the period of the measurements, from March 1999 to late summer 2000, changes in soil water content were small and grassland evaporation and transpiration estimated from energy balance-eddy flux measurements were in excellent agreement with Penman estimates of potential evaporation. Over the 18-month measurement period, the cumulative difference between broadleaved woodland and grassland was small but evaporation from the grassland was 3% higher than that from the woodland. In the springs of 1999 and 2000, evaporation from the grassland was greater than that from the woodland. However, following leaf emergence in the woodland, the difference in cumulative evaporation diminished until the following spring.

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.

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