Włodzimierz Pawlak

Selected Spectral Characteristics of Turbulence over an Urbanized Area in the Centre of Łódź, Poland

We present the turbulence spectra and cospectra derived from more than five years of eddy-covariance measurements at two urban sites in Łódź, central Poland. The fast response wind velocity components were obtained using sonic anemometers placed on narrow masts at 37 and 42 m above ground level. The analysis follows Kaimal et al. (Q J R Meteorol Soc 98:563–589, 1972) who established the spectral and cospectral properties of turbulent flow in atmospheric surface layer on the basis of the Kansas experiment. Our results illustrate many features similar to those of Kaimal et al., but some differences are also observed. The velocity (co)spectra from Łódź show a clear inertial subrange with

Long-term Turbulent Sensible-Heat-Flux Measurements with a Large-Aperture Scintillometer in the Centre of Łódź, Central Poland

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Carbon dioxide flux in the centre of Łódź, Poland—analysis of a 2‐year eddy covariance measurement data set

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Methane and carbon dioxide fluxes of a temperate mire in Central Europe

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Seasonal and diurnal variation of outdoor radon (222Rn) concentrations in urban and rural area with reference to meteorological conditions

-4/3 slope for cospectra. We found that an appropriate stability function for the non-dimensional dissipation of turbulent kinetic energy calculated from spectra in the inertial subrange differs from that of Kaimal et al., and it can be satisfactorily estimated with the assumption of local equilibrium using standard functions for the non-dimensional shear production. A similar function for the cospectrum corresponds well to Kaimal et al. for unstable and weakly stable conditions. The (co)spectra normalized by their spectral values in the inertial subrange are in general similar to those of Kaimal et al., but they peak at lower frequencies in strongly stable conditions. Moreover, our results do not confirm the existence of a clear “excluded region” at low frequencies for the transition from stable to unstable conditions, for longitudinal and lateral wind components. The empirical models of Kaimal et al. with adjusted parameters fit well to the vertical velocity spectrum and the vertical momentum flux cospectrum. The same type of function should be used for longitudinal and lateral wind spectra because of their sharper peak than occurs for the Kansas data. Finally, it should be stressed that the above relationships are well-defined for averaged values. The results for individual 1-h periods are very scattered and can be significantly different from the generalized functions.

Sea water surface energy balance in the Arctic fjord (Hornsund, SW Spitsbergen) in May–November 2014

Abstract The primary aim of this paper was to present the results of turbulent sensible heat flux (QH) measurements with Scintillometer Scintec BLS900 (LAS). The theoretical background of scintillation method has been presented as well as two different ways of sensible heat flux computation from LAS. The measurements presented here were conducted from April to December 2011. Diurnal and partially annual variability of QH has been analyzed, moreover the mean diurnal course of QH in considered months has been prepared. In order to choose the optimal method of QH computation from LAS the results obtained with three different Monin-Obuchov similarity theory functions as well as free convection assumption has been compared. In first case it has been proved that sensible heat flux differs significantly depending on chosen universal function. In turn in case of free convection assumptions it has been revealed that it is valid only for very unstable conditions. Therefore it does not apply to long-time heat flux measurement in case of Łódź. Nevertheless, this study has shown that scintillation method is valuable and reasonable source of path-averaged QH estimates in considered city. Abstrakt Głównym celem pracy była prezentacja wyników pomiarów turbulencyjnego strumienia ciepła jawnego (QH) w Łodzi za pomocą scyntylometru Scintec BLS900. Przedstawione zostały założenia teoretyczne metody scyntylacyjnej, jak również metody wyznaczania strumienia ciepła jawnego za pomocą scyntylometru. Pomiary obejmowały okres od kwietnia do grudnia 2011 roku. Przeanalizowano dobową oraz częściowo roczną zmienność QH, wyznaczając przy tym średnie dobowe jego przebiegi dla poszczególnych miesięcy. W celu wyznaczenia optymalnej metody estymacji QH z pomiarów scyntylometrycznych porównano wyniki uzyskane przy wykorzystaniu trzech różnych funkcji uniwersalnych teorii podobieństwa Monina- Obuchova, jak również przybliżenia dla swobodnej konwekcji. W pierwszym przypadku wykazano, iż strumieni ciepła jawnego w znacznym stopniu różni się, w zależności od zastosowanej funkcji uniwersalnej. Z kolei założenie swobodnej konwekcji w Łodzi sprawdza się jedynie w przypadku silnie chwiejnej warstwy granicznej. Ponadto wykazano, iż w przypadku Łodzi metoda scyntylacyjna stanowi wiarygodną alternatywę wyznaczania strumieni turbulencyjnych.