Doppler lidar measurements of boundary layer winds and sensible heat flux

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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Review of: The open ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

10.5194/acp-2015-891-rc1 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Sensible Heat Flux ◽

Open Ocean ◽

Sensible Heat ◽

Arctic Boundary Layer ◽

Early Fall

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Potential and Limitations in Estimating Sensible-Heat-Flux Profiles from Consecutive Temperature Profiles Using Remotely-Piloted Aircraft Systems

Boundary-Layer Meteorology ◽

10.1007/s10546-019-00478-9 ◽

2019 ◽

Vol 174 (1) ◽

pp. 145-177 ◽

Cited By ~ 1

Author(s):

Line Båserud ◽

Joachim Reuder ◽

Marius O. Jonassen ◽

Timothy A. Bonin ◽

Phillip B. Chilson ◽

...

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Mesoscale Model ◽

Potential Temperature ◽

Sensible Heat Flux ◽

Time Of Day ◽

Sensible Heat ◽

Tethered Balloon ◽

Flux Divergence ◽

Remotely Piloted Aircraft

Abstract Profiles of the sensible heat flux are key to understanding atmospheric-boundary-layer (ABL) structure and development. Based on temperature profiling by a remotely-piloted aircraft system (RPAS), the Small Unmanned Meteorological Observer (SUMO) platform, during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign, 108 heat-flux profiles are estimated using a simplified version of the prognostic equation for potential temperature $$\theta $$θ that relates the tendency in $$\theta $$θ to the flux divergence over the time span between two consecutive flights. We validate for the first time RPAS-based heat-flux profiles against a network of 12 ground-based eddy-covariance stations (2–60 m above ground), in addition to a comparison with fluxes from a manned aircraft and a tethered balloon, enabling the detailed investigation of the potential and limitations related to this technique for obtaining fluxes from RPAS platforms. We find that appropriate treatment of horizontal advection is crucial for obtaining realistic flux values, and present correction methods specific to the state of the ABL. Advection from a mesoscale model is also tested as another correction method. The SUMO heat-flux estimates with appropriate corrections compare well with the reference measurements, with differences in the performance depending on the time of day, since the evening period shows the best results (94$$\%$$% within the spread of ground stations), and the afternoon period shows the poorest results (63$$\%$$% within the spread). The diurnal cycle of the heat flux is captured by the SUMO platform for several days, with the flux values from the manned aircraft and tethered balloon coinciding well with those from the SUMO platform.

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How Does Soil Moisture Influence the Early Stages of the South American Monsoon?

Journal of Climate ◽

10.1175/2007jcli1846.1 ◽

2008 ◽

Vol 21 (2) ◽

pp. 195-213 ◽

Cited By ~ 40

Author(s):

Estela A. Collini ◽

Ernesto H. Berbery ◽

Vicente R. Barros ◽

Matthew E. Pyle

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Soil Moisture ◽

Latent Heat ◽

Sensible Heat Flux ◽

South American ◽

Sensible Heat ◽

The South ◽

Early Stages ◽

Initial Soil

Abstract This article discusses the feedbacks between soil moisture and precipitation during the early stages of the South American monsoon. The system achieves maximum precipitation over the southern Amazon basin and the Brazilian highlands during the austral summer. Monsoon changes are associated with the large-scale dynamics, but during its early stages, when the surface is not sufficiently wet, soil moisture anomalies may also modulate the development of precipitation. To investigate this, sensitivity experiments to initial soil moisture conditions were performed using month-long simulations with the regional mesoscale Eta model. Examination of the control simulations shows that they reproduce all major features and magnitudes of the South American circulation and precipitation patterns, particularly those of the monsoon. The surface sensible and latent heat fluxes, as well as precipitation, have a diurnal cycle whose phase is consistent with previous observational studies. The convective inhibition is smallest at the time of the precipitation maximum, but the convective available potential energy exhibits an unrealistic morning maximum that may result from an early boundary layer mixing. The sensitivity experiments show that precipitation is more responsive to reductions of soil moisture than to increases, suggesting that although the soil is not too wet, it is sufficiently humid to easily reach levels where soil moisture anomalies stop being effective in altering the evapotranspiration and other surface and boundary layer variables. Two mechanisms by which soil moisture has a positive feedback with precipitation are discussed. First, the reduction of initial soil moisture leads to a smaller latent heat flux and a larger sensible heat flux, and both contribute to a larger Bowen ratio. The smaller evapotranspiration and increased sensible heat flux lead to a drier and warmer boundary layer, which in turn reduces the atmospheric instability. Second, the deeper (and drier) boundary layer is related to a stronger and higher South American low-level jet (SALLJ). However, because of the lesser moisture content, the SALLJ carries less moisture to the monsoon region, as evidenced by the reduced moisture fluxes and their convergence. The two mechanisms—reduced convective instability and reduced moisture flux convergence—act concurrently to diminish the core monsoon precipitation.

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Spatial variations of sensible heat flux over an urban area measured using Doppler lidar

Meteorological Applications ◽

10.1002/met.79 ◽

2008 ◽

Vol 15 (3) ◽

pp. 367-380 ◽

Cited By ~ 11

Author(s):

J. C. Davis ◽

C. G. Collier ◽

F. Davies ◽

K. E. Bozier

Keyword(s):

Heat Flux ◽

Urban Area ◽

Sensible Heat Flux ◽

Spatial Variations ◽

Doppler Lidar ◽

Sensible Heat

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Long-term Trend of Planetary Boundary Layer Height in Climate Models and Observations over East Asia

10.5194/egusphere-egu2020-18191 ◽

2020 ◽

Author(s):

Man Yue ◽

Minghuai Wang

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

East Asia ◽

Planetary Boundary Layer ◽

Climate Models ◽

Sensible Heat Flux ◽

Sensible Heat ◽

Term Trend ◽

Long Term Trend

<p>Abstract: Planetary boundary layer (PBL) plays an important role in climate and air quality simulations. Large uncertainties remain in understanding the long-term trend of PBL height (PBLH). In this study, radiosonde data and ERA-Interim reanalysis data are applied to reveal the critical climate factors and mechanisms dominating the long-term trend of PBLH over East Asia. Our results show that, observed long-term shift in PBLH trend is found to be consistent with changes in sensible heat flux (SHFLX), net downward surface shortwave flux (SWFLX) and low cloud cover (LCC). Increases in soil moisture and LCC in recent years can modulate the energy partition through the SHFLX and modifying the surface radiation budget, and further lead to the long-term shift trend of PBLH. Long-term trend of PBLH over East Asia is further examined in climate models (including NCAR CESM2) and data from the Coupled Model Inter-comparison Project Phase 6 (CMIP6) experiments. The global climate models are not able to reproduce the long-term trend of PBLH over East Asia. CESM2 is shown to not catch the long-term variability of sensible heat flux and surface shortwave flux. Further analysis is performed to examine how the trend of mean PBLH and extreme low PBLH may be different.</p>

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Doppler lidar observations of sensible heat flux and intercomparisons with a ground-based energy balance station and WRF model output

Meteorologische Zeitschrift ◽

10.1127/0941-2948/2009/0367 ◽

2009 ◽

Vol 18 (2) ◽

pp. 155-162 ◽

Cited By ~ 4

Author(s):

Jenny Davis ◽

Christopher G. Clare Collier ◽

Fay Davies ◽

Guy N. Pearson ◽

Ralph Burton ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Sensible Heat Flux ◽

Wrf Model ◽

Model Output ◽

Doppler Lidar ◽

Sensible Heat ◽

Lidar Observations

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Boundary-layer turbulent processes and mesoscale variability represented by Numerical Weather Prediction models during the BLLAST campaign

10.5194/acp-2015-1042 ◽

2016 ◽

Cited By ~ 2

Author(s):

Fleur Couvreux ◽

Eric Bazile ◽

Guylaine Canut ◽

Yann Seity ◽

Marie Lothon ◽

...

Keyword(s):

Boundary Layer ◽

Heat Flux ◽

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Sensible Heat Flux ◽

Grid Size ◽

Global Model ◽

Sensible Heat ◽

Mesoscale Variability ◽

Order Of Magnitude

Abstract. This study evaluates the ability of three operational models, AROME, ARPEGE and ECMWF, to predict the boundary-layer turbulent processes and mesoscale variability observed during the Boundary Layer Late-Afternoon and Sunset Turbulence (BLLAST) field campaign. AROME is a 2.5 km limited area non-hydrostatic model operated over France, ARPEGE a global model with a 10 km grid-size over France and ECMWF a global model with a 16 km grid-size. We analyze the representation of the vertical profiles of temperature and humidity and the time evolution of near surface atmospheric variables as well as the radiative and turbulent fluxes for a total of 12 24h-long Intensive Observing Periods. Special attention is paid to the evolution of the turbulent kinetic energy that was sampled by a combination of independent instruments. For the first time, this variable, which is a central variable in the turbulence scheme used in AROME and ARPEGE, is evaluated with observations. In general, the 24h-forecasts succeed in reproducing the variability from one day to the other in term of cloud cover, temperature, boundary-layer depth. However, they exhibit some systematic biases, in particular a cold bias within the daytime boundary layer for all models. An overestimation of the sensible heat flux is noted for two points in ARPEGE, partly related to an inaccurate simplification of surface characteristics and over-predominance of forests. AROME shows a moist bias within the daytime boundary layer, consistently with overestimated latent heat fluxes. ECMWF presents a dry bias at 2 m above surface and also overestimates the sensible heat flux. The high-resolution model AROME better resolves the vertical structures, in particular the strong daytime inversion and the evening thin stable boundary layer. This model is also capable to capture the peculiar observed features, such as the orographically-driven subsidence and a well-defined maximum in water vapor mixing ratio in the upper part of the residual layer that arises during the evening due to mesoscale advection. The mesoscale variability is analyzed and the order of magnitude is also well reproduced in AROME. AROME provides a good simulation of the diurnal variability of the turbulent kinetic energy while ARPEGE shows a right order of magnitude.

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