Vertical profiles of the structure characteristic of air temperature in the atmospheric boundary layer from sodar measurements

AbstractA detailed analysis of the evaporating ocean spray effect on the vertical latent and sensible heat fluxes in a marine atmospheric boundary layer (MABL) for different droplet sizes, vertical distributions of air temperature, humidity, and turbulent intensity is presented. For our analysis we have employed a two-temperature nonequilibrium MABL model developed in our previous work. The obtained analytical and numerical solutions show that the latent and total heat fluxes are significantly enhanced by large droplets because these droplets produce steep vertical gradients of moisture and air temperature in a MABL. Small droplets, however, do not noticeably change the total heat flux but rather redistribute the energy between its sensible and latent components. It has been shown that evaporating spray affects the turbulent kinetic energy (thus the intensity of the vertical turbulent transport) mostly mechanically by altering the vertical distribution of the mass density of the air–spray mixture rather than thermodynamically by changing vertical profiles of the air temperature and moisture. Furthermore, we have found that the vertical profiles of heat fluxes are approximately self-similar for a wide range of defining parameters, that is, can be approximately scaled to a reference heat profile for a wide range of vertical distributions of the temperature, humidity, and turbulence intensity. The obtained analytical expressions for the vertical heat fluxes affected by the spray presence enable their quick and efficient calculations. This will allow for the future construction of a computationally efficient spray and accurate parameterization to be used in global weather prediction models.

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Retrieval of structure functions of air temperature and refractive index from large eddy simulations of the atmospheric boundary layer

10.1117/12.2023990 ◽

2013 ◽

Author(s):

Chris Wilson ◽

Alexander M. van Eijk ◽

Evgeni Fedorovich

Keyword(s):

Boundary Layer ◽

Refractive Index ◽

Atmospheric Boundary Layer ◽

Air Temperature ◽

Structure Functions ◽

Large Eddy Simulations ◽

Large Eddy

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The vertical variability of black carbon observed in the atmospheric boundary layer during DACCIWA

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-7911-2020 ◽

2020 ◽

Vol 20 (13) ◽

pp. 7911-7928 ◽

Cited By ~ 2

Author(s):

Barbara Altstädter ◽

Konrad Deetz ◽

Bernhard Vogel ◽

Karmen Babić ◽

Cheikh Dione ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Black Carbon ◽

West African Monsoon ◽

Ground Level ◽

Cloud Base ◽

Small Scale ◽

Vertical Profiles ◽

Scale Modelling ◽

Reactive Trace Gases

Abstract. This study underlines the important role of the transported black carbon (BC) mass concentration in the West African monsoon (WAM) area. BC was measured with a micro-aethalometer integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol). As part of the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project, 53 measurement flights were carried out at Savè, Benin, on 2–16 July 2016. A high variability of BC (1.79 to 2.42±0.31 µg m−3) was calculated along 155 vertical profiles that were performed below cloud base in the atmospheric boundary layer (ABL). In contrast to initial expectations of primary emissions, the vertical distribution of BC was mainly influenced by the stratification of the ABL during the WAM season. The article focuses on an event (14 and 15 July 2016) which showed distinct layers of BC in the lowermost 900 m above ground level (a.g.l.). Low concentrations of NOx and CO were sampled at the Savè supersite near the aircraft measurements and suggested a marginal impact of local sources during the case study. The lack of primary BC emissions was verified by a comparison of the measured BC with the model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) that was applied for the field campaign period. The modelled vertical profiles of BC led to the assumption that the measured BC was already altered, as the size was mainly dominated by the accumulation mode. Further, calculated vertical transects of wind speed and BC presume that the observed BC layer was transported from the south with maritime inflow but was mixed vertically after the onset of a nocturnal low-level jet at the measurement site. This report contributes to the scope of DACCIWA by linking airborne BC data with ground observations and a model, and it illustrates the importance of a more profound understanding of the interaction between BC and the ABL in the WAM region.

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Distributed wind measurements with multiple quadrotor unmanned aerial vehicles in the atmospheric boundary layer

Atmospheric Measurement Techniques ◽

10.5194/amt-14-3795-2021 ◽

2021 ◽

Vol 14 (5) ◽

pp. 3795-3814

Author(s):

Tamino Wetz ◽

Norman Wildmann ◽

Frank Beyrich

Keyword(s):

Boundary Layer ◽

Spatial Distribution ◽

Wind Speed ◽

Atmospheric Boundary Layer ◽

Unmanned Aerial Vehicles ◽

Horizontal Wind ◽

Vertical Profiles ◽

Aerial Vehicles ◽

Wind Measurements ◽

Quadrotor Unmanned Aerial Vehicles

Abstract. In this study, a fleet of quadrotor unmanned aerial vehicles (UAVs) is presented as a system to measure the spatial distribution of atmospheric boundary layer flow. The big advantage of this approach is that multiple and flexible measurement points in space can be sampled synchronously. The algorithm to obtain horizontal wind speed and direction is designed for hovering flight phases and is based on the principle of aerodynamic drag and the related quadrotor dynamics. During the FESST@MOL campaign at the boundary layer field site (Grenzschichtmessfeld, GM) Falkenberg of the Lindenberg Meteorological Observatory – Richard Assmann Observatory (MOL-RAO), 76 calibration and validation flights were performed. The 99 m tower equipped with cup and sonic anemometers at the site is used as the reference for the calibration of the wind measurements. The validation with an independent dataset against the tower anemometers reveals that an average accuracy of σrms<0.3 m s−1 for the wind speed and σrms,ψ<8∘ for the wind direction was achieved. Furthermore, we compare the spatial distribution of wind measurements with the fleet of quadrotors to the tower vertical profiles and Doppler wind lidar scans. We show that the observed shear in the vertical profiles matches well with the tower and the fluctuations on short timescales agree between the systems. Flow structures that appear in the time series of a line-of-sight measurement and a two-dimensional vertical scan of the lidar can be observed with the fleet of quadrotors and are even sampled with a higher resolution than the deployed lidar can provide.

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Distributed wind measurements with multiple quadrotor UAVs in the atmospheric boundary layer

10.5194/egusphere-egu21-10239 ◽

2021 ◽

Author(s):

Tamino Wetz ◽

Norman Wildmann ◽

Frank Beyrich

Keyword(s):

Boundary Layer ◽

Spatial Distribution ◽

Wind Speed ◽

Atmospheric Boundary Layer ◽

Horizontal Wind ◽

Vertical Profiles ◽

Sonic Anemometers ◽

Meteorological Observatory ◽

Wind Measurements ◽

Quadrotor Uavs

A swarm of quadrotor UAVs is presented as a system to measure the spatial distribution of atmospheric boundary layer flow. The big advantage of this approach is, that multiple and flexible measurement points in space can be sampled synchronously. The algorithm to obtain horizontal wind speed and direction is designed for hovering flight phases and is based on the principle of aerodynamic drag and the related quadrotor dynamics using only on-board sensors.During the FESST@MOL campaign at the Boundary Layer Field Site (Grenzschichtmessfeld, GM) Falkenberg of the Lindenberg Meteorological Observatory - Richard-A&#223;mann-Observatory (MOL-RAO), 76 calibration and validation flights were performed. The 99 m tower equipped with cup and sonic anemometers at the site is used as the reference for the calibration of the wind measurements. The validation with an independent dataset against the tower anemometers reveals that an average accuracy of &#963;rms < 0.3 m s-1 for the wind speed and &#963;rms,&#936;< 8&#176; for the wind direction was achieved.Furthermore, we compare the spatial distribution of wind measurements with the swarm to the tower vertical profiles and Doppler wind lidar scans. We show that the observed shear in the vertical profiles matches well with the tower and the fluctuations on short time scales agree between the systems. Flow structures that appear in the time series of a line-of-sight measurement and a two-dimensional vertical scan of the lidar can be observed with the swarm and are even sampled with a higher resolution than the deployed lidar can provide.In addition to the intercomparison of the mean wind velocity measurements, turbulence data of the UAV-swarm measurements are analyzed and a comparison to sonic anemometer measurements is provided.

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Evaluating the response of the diurnal range of surface and air temperature to evaporative conditions across vegetation types in ERA5 and FLUXNET data

10.5194/egusphere-egu21-2603 ◽

2021 ◽

Author(s):

Annu Panwar ◽

Axel Kleidon

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Air Temperature ◽

Extreme Events ◽

Heat Storage ◽

Vegetation Type ◽

Diurnal Variations ◽

Vegetation Types ◽

Evaporative Fraction ◽

Simple Boundary

The diurnal variations of surface and air temperature are related but their different responses to evaporative conditions can inform us about land-atmosphere interactions, extreme events, and their response to global change. Here, we evaluate the sensitivity of the diurnal ranges of surface (DTsR) and air (DTaR) temperature to evaporative fraction, across short vegetation, savanna, and forests at 106 Fluxnet observational sites and in the ERA5 global reanalysis. We show that the sensitivity of DTsR to evaporative fraction depends on vegetation type, whereas for DTaR it does not. Using FLUXNET data we found that on days with low evaporative fraction, DTsR is enhanced by up to 20 &#176;C (30 &#176;C in ERA5) in short vegetation, whereas only by 8 &#176;C (10 &#176;C in ERA5) in forests. Particularly, in short vegetation, ERA5 shows stronger responses, which is attributable to a negative bias on days with the high evaporative fraction. ERA5 also tends to have lower shortwave and longwave radiation input when compared to FLUXNET data. Contrary to DTsR, DTaR responds rather similarly to evaporative fraction irrespective of vegetation type (8 &#176;C in FLUXNET, 10 &#176;C in ERA5). To explain this, we show that the DTaR response to the evaporative fraction is compensated for differences in atmospheric boundary layer height by up to 2000 m, which is similar across vegetation types. We demonstrate this with a simple boundary layer heat storage calculation, indicating that DTaR is primarily shaped by changes in boundary layer heat storage whereas DTsR mainly responds to solar radiation, evaporation, and vegetation. &#160;Our study reveals some systematic biases in ERA5 that need to be considered when using its temperature products for understanding land-atmosphere interactions or extreme events. To conclude, this study demonstrates the importance of vegetation and the dynamics of the atmospheric boundary layer in regulating diurnal variations in surface and air temperature under different evaporative conditions.

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Continuous Daily Observation of the Marine Atmospheric Boundary Layer over the Kuroshio by a Helicopter Shuttle Service

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-14-00067.1 ◽

2015 ◽

Vol 32 (1) ◽

pp. 3-21 ◽

Cited By ~ 3

Author(s):

Youichi Tanimoto ◽

Kou Shimoyama ◽

Shoichi Mori

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Dynamic Pressure ◽

Japan Meteorological Agency ◽

Observation System ◽

Vertical Profiles ◽

Marine Atmospheric Boundary Layer ◽

Near Surface ◽

Ocean Front ◽

Observation Method

AbstractThis paper describes a new initiative in which in situ observations of the marine atmospheric boundary layer (MABL) are made by a helicopter shuttle connecting six islands south of Tokyo. This observation method aims to make frequent measurements of temperature and moisture in the MABL across an ocean front, where direct measurements of the MABL have been limited. An onboard observation system to meet flight regulations was developed. Observed temperature and moisture as a function of pressure at 1-s intervals provided vertical profiles up to the 900-hPa level above each of the islands, from 24 December 2010 to 6 April 2011, with the exception of an accidental power down in mid-February 2011. The observed values are validated by intercomparison with surface measurements from weather stations, atmospheric soundings, and mesoscale weather analysis provided by the Japan Meteorological Agency. Temperature and moisture values obtained using the system described here at the surface are significantly correlated with those from the weather station. The meridional changes revealed by the observed vertical profiles depict rich MABL structures, such as a cold-air intrusion and a strong near-surface inversion, that are not captured by the mesoscale weather analysis. However, this discrepancy is probably due to insufficient treatment in the mesoscale numerical model rather than observational errors. Additional intercomparisons indicate no influence from either artificial mixing by the helicopter rotor or by dynamic pressure caused by the fast-moving helicopter when obtaining the vertical profiles. Following these validations, the continuation of the initiative will allow for examining the influence of the ocean front on the overlying MABL on a synoptic time scale.

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