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Vertical profile of concentration and flow of aerosol particles over arable land
Zapletal, Miloš ; Hovorka, J. ; Hladík, J. ; Juráň, Stanislav
At present, the immission load of the territory and population by solid / liquid or mixed particles with the size of 1 nm - 100 μm suspended in the atmosphere, or PM, is one of the biggest problems not only in the Czech Republic but practically throughout Europe. High PM concentrations are associated with a large number of health problems. These include respiratory disorders and an increased risk of lung and skin cancer (WHO, 2006). In the Czech Republic, long-term exposure to PM is an important factor responsible for reducing the quality of life of the population. Among the most serious effects in terms of overall health burden is a significant reduction in life expectancy (WHO, 2006). Transport and industrial activities are generally considered to be the main source of PM10 particles. Existing information on the chemical composition, size distribution, secondary particle fraction and deposition flux of particles on different types of surfaces is still incomplete. Aerosol concentration measurements have been performed in many cities at street level or for personal exposure assessment (Kaur et al., 2005, Longley et al., 2004). Eddy covariance measurements of particulate emission flux over large urban agglomerations were performed (Dorsey et al., 2002, Järvi et al., 2009, Martin et al., 2009, Deventer et al., 2013). Direct measurement of the emission flux of the eddy particles by the covariation method provided information on the upward air flow and vertical particle exchange over some urban agglomerations (eg Manchester, London, Helsinki). A description of the measurement of the eddy particle flow by the covariance method from an aircraft is given in Buzorius et al. (2006). Less information exists on the emission flux of particles above different types of sources at different heights, eg above arable land, opencast coal mine or local fireplaces.
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Measured and modelled fluxes of tropospheric ozone in mountainous Norway spruce forest
Juráň, Stanislav ; Zapletal, Miloš ; Večeřa, Zbyněk ; Cudlín, Pavel ; Urban, Otmar
Tropospheric ozone fluxes (O3) were measured in Norway spruce forest at Bily Kriz, Czech Republic by eddy covariance technique. Within-canopy concentration gradient was measured by APOA-370 analysers (Horiba, Japan) in 7m, 25m and 30m above ground. Fluxes of O3 were modelled from the concentration gradient by applying Inverse Lagrangian Transport Model (Raupach, 1989). Next, O3 fluxes were modelled on the basis of resistent analogy. Ozone flux measured by eddy covariance technique amounted up to 1.19 nmol m-2 s-1 on daily average and the lowest -0.75 nmol m-2 s-1. Studied forest stand was net sink for ozone in 7.14 mmol m-2 per day (=0.343 g m-2 per day). The highest ozone emission peaked during noon hours, suggesting closure of stomata due to low air temperature and ozone production due to sufficient radiation. Both models proved to be imprecise when compared to measured data in autumn-winter transition period.
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Automated eddy covariance data quality control for long-term measurements
Šigut, L. ; Mauder, M. ; Sedlák, Pavel ; Pavelka, M. ; Špunda, V.
Estimation of matter and energy exchange using the eddy covariance method is often organized into regional or global networks. To achieve comparability among sites, it is important to standardize and specify the methodology used. Currently, quality control (QC) is one of the most time-demanding steps in data processing within the Czech Carbon Observation System. Although manual QC (MQC) enables consideration of more complex test applications, it is often difficult to document. The aim of this study was to establish an automated QC (AQC) scheme based on available literature and post-processing software and test its effectivity and reliability on sites comprising an agroecosystem and a mature European beech forest. AQC successfully flagged low-quality CO2 fluxes and provided estimates of net ecosystem productivity similar to estimates based on MQC. The tests’ efficiency was particularly high for the agroecosystem, where AQC removed 13% less data than did MQC. We conclude that the adopted AQC displays satisfactory performance, especially for sites with low canopy heights.
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Automated eddy covariance data quality control for long-term measurements
Šigut, Ladislav ; Mauder, M. ; Sedlák, Pavel ; Pavelka, Marian ; Špunda, Vladimír
Estimation of matter and energy exchange using the eddy covariance method is often organized into regional or global networks. To achieve comparability among sites, it is important to standardize and specify the methodology used. Currently, quality control (QC) is one of the most time-demanding steps in data processing within the Czech Carbon Observation System. Although manual QC (MQC) enables consideration of more complex test applications, it is often difficult to document. The aim of this study was to establish an automated QC (AQC) scheme based on available literature and post-processing software and test its effectivity and reliability on sites comprising an agroecosystem and a mature European beech forest. AQC successfully flagged low-quality CO2 fluxes and provided estimates of net ecosystem productivity similar to estimates based on MQC. The tests’ efficiency was particularly high for the agroecosystem, where AQC removed 13% less data than did MQC. We conclude that the adopted AQC displays satisfactory performance, especially for sites with low canopy heights.
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Flux footprints in different ecosystems
Macálková, Lenka ; Havránková, Kateřina ; Pavelka, Marian
Flux footprint is an upwind area where the atmospheric flux measured by an instrument is generated. Footprint size depends on measurement height, surface roughness, and atmospheric thermal stability. Our study focused on the flux footprints of four CzechGlobe ecosystem stations in a wetlands area, an agroecosystem, and young and mature spruce forests. Our aims were to prove that the sites were suitable for eddy covariance measurement and compare flux footprints under various atmospheric thermal conditions: stable, neutral, and unstable. Two computational models were used: the Kormann–Meixner (2001) and Kljun (2004)models. The outputs were processed graphically in site maps.
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Comparison of eddy covariance and bowen ratio energy balance method. Energy balance cloruse versus bowen ratio similarity assumption
Fischer, Milan ; Trnka, Miroslav ; Pozníková, Gabriela ; Sedlák, Pavel ; Orság, Matěj ; Kučera, J. ; Žalud, Z.
The Bowen ratio and the Monin-Obukhov similarity principles are based on the assumption that the eddy diff usivities for temperature and humidity are equal to each other under all atmospheric stratifi cations within turbulent surface boundary layer. However, several authors reported that this equality was violated under advective inversion or during the non-stationary conditions due to clouds passing by and sudden change of wind speed and direction. Th e inequality of the eddy diff usivity can lead to errors in the energy partitioning estimates by gradient techniques like the Bowen ratio energy balance (BREB) and the aerodynamical method, or methods based on residual energy balance such as the Penman-Monteith or Priestley-Taylor models. Th is study investigates two seasons of simultaneous measurement by eddy covariance (EC) and BREB above a high density poplar plantation at the Domanínek locality. Th e direct measurement of eddy diff usivities by EC is reinvestigating the validity of the long term measurement (since 2008) by BREB. Results showed unequal exchange coeffi cients with their mean 0.31 to 0.35 m2 s-1 for 2011 and 2012, respectively, favouring the transport of latent heat. Th is might be explained by the diff erent footprints of the BREB and EC methods, an undeveloped internal boundary layer or instrumental errors.
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Improvement of CO2 eddy fluxes modelling in topographically complex terrain
Šigut, Ladislav
Annual sums of net ecosystem exchange (NEE) estimated by eddy covariance method (EC) are often used for comparisons among sites. But application of EC in topographically complex terrain restrains application of standard methods for their estimation. Analysis of friction air velocity response of night-time CO2 fluxes and estimation of mean daily ecosystem respiration from daytime NEE showed that night-time data and fluxes measured early after sunrise or late before sunset are not sufficiently reliable for computation of accurate annual sums of NEE. Therefore presented method takes into account auxiliary soil chamber measurements and applies correction factor in ecosystem respiration model calibrated to biomass inventory results. Also automated algorithm for computation of light response curve parameters in constrained range was established. This method produced accurate annual sums of NEE that were only 7.2% ± 5.2 higher than values determined by biomass inventory method.
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Atmospheric factors influencing net ecosystem production of Norway spruce forest in Beskydy Mountains
Taufarová, Klára ; Havránková, Kateřina ; Czerný, Radek ; Janouš, Dalibor
Daily net ecosystem production values of Norway spruce forest at Experimental Ecological Research Site Bílý Kříž in Beskydy Mountains were estimated using eddy covariance technique. Norway spruce forest uptakes CO2 from the atmosphere during production season. During production seasons 2005-2007 mean daily net ecosystem production was 22 kg C ha-1, and mean production season duration was 240 days. During production seasons there occurred days with respiration higher than assimilation, thus the forest was source of the atmospheric carbon. There were 45, 68 and 39 days in production seasons 2005, 2006 and 2007, respectively, when the forest was carbon source. It was caused by 1) significant decrease of air temperature and low intensity of PAR at the beginning and end of production seasons; 2) low radiation in overcast days and 3) long dry period with high intensity of direct radiation and high air temperature during production seasons.
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