Ground-based lidar observations of vertical aersosol and water vapor profiles within the boundary layer over heterogeneous terrain

2021 ◽  
Author(s):  
Johannes Speidel ◽  
Hannes Vogelmann ◽  
Matthias Perfahl ◽  
Matthias Mauder ◽  
Luise Wanner
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Energy Balance ◽  
Transport Processes ◽  
Precipitation Forecast ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Heterogeneous Terrain ◽  
Ground Based Lidar ◽  
Aerosol Backscatter

<p>Connecting the earth's surface with the free troposphere, the planetary boundary layer (PBL) comprises complex dynamics of turbulent behavior. This especially applies for areas with heterogeneous terrain. Relevant near-ground processes such as released energy fluxes and the emission of aerosols and trace gases directly interact with the atmosphere. Therefore, the PBL's physical state is determined both by the near-ground processes as well as entrainment of air parcels from higher layers. The mainly turbulence-driven transport of particles and properties throughout the PBL constrain a comprehensive understanding of the PBL's behavior. Hence, the energy balance closure problem as well as errors in precipitation forecast in long-term numerical weather predictions, amongst others, remain unresolved challenges. Here, ground-based lidar profiling is a well suitable method for observing the PBL, as data sampling allows for high temporal and vertical resolutions (Here: Sampling rate of 100\,Hz and 7.5\,m). During the CHEESEHEAD campaign, carried out in summer 2019, our newly developed ATMONSYS lidar performed measurements over complex terrain in northern Wisconsin. There, our lidar system was embedded in a dense network of multiple in-situ and remote sensing instruments. The central aim of this campaign was to further contribute to solve the energy balance closure problem. With the ATMONSYS lidar, vertical columns of aerosol backscatter coefficients, water vapor and temperature have been recorded. The presented work shows what the data is suitable for in terms of resolution and temporal extent in the first place. As a second point, focus is given on structure and variability of aerosol backscatter coefficient distributions and water vapor concentrations as well as their implications on the prevailing state of the PBL. Based on the presented findings, we discuss the potential and suitability of this experimental data for deriving transport processes within the PBL.</p>

On the way to realistic large eddy simulations – A comparison of virtual measurements with CHEESEHEAD19 field measurements

2021 ◽  
Author(s):  
Luise Wanner ◽  
Sreenath Paleri ◽  
Johannes Speidel ◽  
Ankur Desai ◽  
Matthias Sühring ◽  
...  
Keyword(s):  
Energy Balance ◽  
Eddy Covariance ◽  
Field Measurements ◽  
Transport Processes ◽  
Large Eddy Simulations ◽  
Surface Model ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Large Eddy ◽  
Eddy Covariance Measurements

<p>Large-eddy simulations are useful tools to study transport processes by mesoscale structures in the atmospheric boundary layer, since in contrast to single-tower eddy covariance measurements, they provide not only temporally but also spatially highly resolved information. Therefore, they are well suited to study the energy balance closure problem, for which the mesoscale transport of latent and sensible heat, triggered by heterogeneous ecosystems, is suspected to be a major cause. However, this requires simulations that are as realistic as possible and thus allow a comparison of real measurements in the field and virtual measurements in the simulation.<br>During the Chequamegon Heterogeneous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors (CHEESEHEAD) experiment in the summer of 2019, a heterogeneous 10x10 square km domain was intensively sampled across scales. This data offers a unique possibility to set up large-eddy simulations with realistic surface heterogeneity. We use PALM to simulate two days and an area of 40 by 40 square kilometers incorporating the CHEESEHEAD site. The large scale atmospheric forcings to inform the boundary conditions are determined from the NCEP HRRR product. As the lower boundary condition, we use a soil and land-surface model coupled with a plant-canopy model, which we adapt to the CHEESEHEAD area based on ground-based and airborne measurements of plant physiological data.<br>In this study, we investigate how well the simulations match with real measurements by comparing simulated profiles and virtual tower measurements with field measurements from radiosonde ascents, lidar measurements of three-dimensional wind and water vapor, eddy-covariance measurements from the 400 meter tower in the center of the study domain, as well as from typical eddy-covariance stations distributed through the study area. This way, we investigate how realistic the simulations actually are and to what extent the knowledge gained from them concerning the energy balance closure problem can be transferred to field measurements.</p>

scholarly journals Some aspects of the energy balance closure problem

2006 ◽  
Vol 6 (12) ◽  
pp. 4395-4402 ◽  
Author(s):  
T. Foken ◽  
F. Wimmer ◽  
M. Mauder ◽  
C. Thomas ◽  
C. Liebethal
Keyword(s):  
Surface Layer ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Low Frequency ◽  
Turbulent Fluxes ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Considerable Influence ◽  
Turbulence Spectrum ◽  
Eddy Covariance Method

Abstract. After briefly discussing several reasons for the energy balance closure problem in the surface layer, the paper focuses on the influence of the low frequency part of the turbulence spectrum on the residual. Changes in the turbulent fluxes in this part of the turbulence spectrum were found to have a significant influence on the changes of the residual. Using the ogive method, it was found that the eddy-covariance method underestimates turbulent fluxes in the case of ogives converging for measuring times longer than the typical averaging interval of 30 min. Additionally, the eddy-covariance method underestimates turbulent fluxes for maximal ogive functions within the averaging interval, both mainly due to advection and non-steady state conditions. This has a considerable influence on the use of the eddy-covariance method.

scholarly journals A Diagnostic Approach towards the Causes of Energy Balance Closure Problem

2016 ◽  
Vol 06 (02) ◽  
pp. 101-114 ◽  
Author(s):  
Ali Varmaghani ◽  
William E. Eichinger ◽  
John H. Prueger
Keyword(s):  
Energy Balance ◽  
Diagnostic Approach ◽  
Closure Problem ◽  
Energy Balance Closure

The Uncertainty of Penman-Monteith Method and the Energy Balance Closure Problem

2018 ◽  
Author(s):  
Xingming Hao ◽  
Shuhua Zhang ◽  
Weihong Li ◽  
Weili Duan ◽  
Gonghuan Fang ◽  
...  
Keyword(s):  
Energy Balance ◽  
Closure Problem ◽  
Energy Balance Closure

scholarly journals Energy Exchange and Evapotranspiration over the Ejina Oasis Riparian Forest Ecosystem with Different Land-Cover Types

Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3424
Author(s):  
Weizhen Wang ◽  
Feinan Xu ◽  
Jiemin Wang
Keyword(s):  
Water Vapor ◽  
Energy Balance ◽  
Forest Ecosystem ◽  
Riparian Forest ◽  
Growing Season ◽  
Energy Balance Closure ◽  
Tamarix Chinensis ◽  
Barren Land ◽  
Ejina Oasis ◽  
Flux Data

Investigating the energy and water vapor exchange in oasis riparian forest ecosystems is of significant importance to improve scientific understanding of land surface processes in extreme arid regions. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER) provided many observations of water vapor and heat fluxes from riparian forest ecosystem by using a network of eddy-covariance (EC) systems installed over representative surfaces in the Ejina Oasis, which is located in the downstream areas of the Heihe River Basin, northwestern China. Based on EC flux measurements and meteorological data performed at five stations and covering representative surface types of Populus euphratica tree with associated Tamarix chinensis shrub, Tamarix chinensis shrubland, cantaloupe cropland, and barren-land, this study explored the spatio-temporal patterns of heat and water vapor fluxes over the Ejina Oasis riparian forest ecosystem with five different surface types over the course of a growing season in 2014. Energy balance closure of the flux data was evaluated; footprint analysis for each EC site was also performed. Results showed that energy balance closure for the flux data was reasonably good, with average energy balance ratio (EBR) of 1.03. The seasonal variations in net radiation (Rn), latent (LE), and sensible heat flux (H) over the five contrasting surfaces were similar, and a reverse seasonal change was observed in energy partitioning into LE and H. Remarkable differences in Rn, LE, and H between the five surfaces were explored preliminarily, associated closely with the soil properties and foliage phenology. Over the growing season (May–October) in 2014, the total ET ranged 622–731 mm for mixed forest of P. euphratica trees with associated T. chinensis shrubs with average daily ET of 3.6–4.2 mm; ET from T. chinensis shrubland was about 541 mm, with average daily ET of 3.6 mm. ET for barren-land was 195 mm. The total ET in irrigated cantaloupe cropland with plastic mulch was 431 mm for its four-month growing period with a total average of 3.8 mm d−1. Determination of ET over riparian forest ecosystem helps to improve reasonable use of limited water resource in the Ejina Oasis.

scholarly journals Surface-Energy-Balance Closure over Land: A Review

2020 ◽  
Vol 177 (2-3) ◽  
pp. 395-426 ◽  
Author(s):  
Matthias Mauder ◽  
Thomas Foken ◽  
Joan Cuxart
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Transport Processes ◽  
Heat Fluxes ◽  
Future Research ◽  
Turbulent Heat ◽  
Energy Balance Closure ◽  
Airborne Measurements ◽  
Open Questions

Abstract Quantitative knowledge of the surface energy balance is essential for the prediction of weather and climate. However, a multitude of studies from around the world indicate that the turbulent heat fluxes are generally underestimated using eddy-covariance measurements, and hence, the energy balance is not closed. This energy-balance-closure problem, which has been heavily covered in the literature for more than 25 years, is the topic of the present review, in which we provide an overview of the potential reason for the lack of closure. We demonstrate the effects of the diurnal cycle on the energy balance closure, and address questions with regard to the partitioning of the energy balance residual between the sensible and the latent fluxes, and whether the magnitude of the flux underestimation can be predicted based on other variables typically measured at micrometeorological stations. Remaining open questions are discussed and potential avenues for future research on this topic are laid out. Integrated studies, combining multi-tower experiments and scale-crossing, spatially-resolving lidar and airborne measurements with high-resolution large-eddy simulations, are considered to be of critical importance for enhancing our understanding of the underlying transport processes in the atmospheric boundary layer.

scholarly journals Some aspects of the energy balance closure problem

2006 ◽  
Vol 6 (2) ◽  
pp. 3381-3402 ◽  
Author(s):  
T. Foken ◽  
F. Wimmer ◽  
M. Mauder ◽  
C. Thomas ◽  
C. Liebethal
Keyword(s):  
Surface Layer ◽  
Energy Balance ◽  
Eddy Covariance ◽  
Low Frequency ◽  
Turbulent Fluxes ◽  
Closure Problem ◽  
Energy Balance Closure ◽  
Considerable Influence ◽  
Turbulence Spectrum ◽  
Eddy Covariance Method

Abstract. After briefly discussing several reasons for the energy balance closure problem in the surface layer, the paper focuses on the influence of the low frequency part of the turbulence spectrum on the residual. Changes in the turbulent fluxes in this part of the turbulence spectrum were found to have a significant influence on the changes of the residual. Using the ogive method, it was found that the eddy-covariance method underestimates turbulent fluxes in the case of ogives converging for measuring times longer than the typical averaging interval of 30 min. Additionally, the eddy-covariance method underestimates turbulent fluxes for maximal ogive functions within the averaging interval, both mainly due to advection and non-steady state conditions. This has a considerable influence on the use of the eddy-covariance method.

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