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

We present the turbulence spectra and cospectra derived frommore than five years of eddy-covariance measurements at two urban sites inŁód´z, 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 Łód´z show a clear inertial subrange with −2/3 slope for spectra and −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.Funding for this research was provided by the Polish Ministry of Science and Higher Education (State Committee for Scientific Research) under grant no. N306 276935 for the years 2008–2012 and grant no. N306 519638 for the years 2010–2013

Atlas parametrów meteorologicznych na stacji pomiarowej w Kopytkowie (Biebrzański Park Narodowy) w roku 2013

Praca wykonana w ramach projektu “Bilans absorpcji i emisji gazów cieplarnianych (metanu, dwutlenku węgla i pary wodnej) na obszarach bagiennych (studium Biebrzańskiego Parku Narodowego)”sfinansowanego ze środków Narodowego Centrum Nauki przyznanych na podstawie decyzji numer DECR2011/01/B/ST10/07550

Singularities of the urban climate of Łódź, Central Poland

Published in: Natural environment of Poland and its protection in Łódź University Geographical Research, edited by E. Kobojek and T.MarszałThe results presented in the work show the selected features of local climate modification caused by urbanisation in Łódź, Central Poland. The city structure is similar to many other mid-European towns, but the influences of urbanisation on local climate are not affected here by other factors. Thus, the outcomes of presented investigations can be generalised for many cities of the region. The findings about the urban heat island are similar to those of other cities and they confirm the general rules about the UHI phenomenon, its spatial distribution and temporal variations (see Arnfield 2003 for a comprehensive review). Similarly, the influence of the city on incoming shortwave radiation in Łódź simply quantify well established relations. More unique are the studies on the albedo and the influence of surface geometry on the absorption of radiation. The influence of the town on humidity is more disputable. On the average, our data confirm the findings on the urban-rural contrasts of these elements, but they also show that unlike the UHI evolution, the diurnal course of humidity differences can take different form even in favourable weather conditions. The measurements of turbulent fluxes of sensible and latent heat, carbon dioxide and methane are unique in Poland and one of the few in Europe; thus they just provide new data and extend our understanding of poorly known processes. At the present stage, it is hard to evaluate if these result are case-specific or more general. The comparison with other cities is problematic because of a small number of similar works – there are several concerning urban energy balance, very few on carbon dioxide flux, and almost none about the flux of methane

Simulation of the mean urban heat island using 2D surface parameters: empirical modeling, verification and extension.

The spatial distribution of the annual mean urban heat island (UHI) intensity was simulated applying empirical models based on datasets from urban areas of Szeged and Debrecen, using simple and easily determinable urban surface cover variables. These two cities are situated on the Alf¨old (Great Hungarian Plain) and have similar topographic and climatic conditions. Temperature field measurements were carried out, Landsat satellite images were evaluated, and then one- and multiple variable models were constructed using linear regression techniques. The selected multiple-parameter models were verified using independent datasets from three urban settlements. In order to obtain some impression of the mean UHI patterns in other cities with no temperature measurements available, the better model was extended to urban areas of four other cities situated in geographical environments similar to Szeged and Debrecen. The main shortcoming of typical empirical models, namely that they are often restricted to a specific location, is overcome by the obtained model since it is not entirely site but more region specific, and valid in a large and densely populated area with several settlements

Importance of initial state and atmospheric conditions for urban land surface models' performance

Urban land surface models (LSM) are commonly evaluated for short periods (a few weeks to months) because of limited observational data. This makes it difficult to distinguish the impact of initial conditions on model performance or to consider the response of a model to a range of possible atmospheric conditions. Drawing on results from the first urban LSM comparison, these two issues are considered. Assessment shows that the initial soil moisture has a substantial impact on the performance. Models initialised with soils that are too dry are not able to adjust their surface sensible and latent heat fluxes to realistic values until there is sufficient rainfall. Models initialised with too wet soils are not able to restrict their evaporation appropriately for periods in excess of a year. This has implications for short term evaluation studies and implies the need for soil moisture measurements to improve data assimilation and model initialisation. In contrast, initial conditions influencing the thermal storage have a much shorter adjustment timescale compared to soil moisture. Most models partition too much of the radiative energy at the surface into the sensible heat flux at the probable expense of the net storage heat flux

Developing a research strategy to better understand, observe, and simulate urban atmospheric processes at kilometer to subkilometer scales

A Met Office/Natural Environment Research Council Joint Weather and Climate Research Programme workshop brought together 50 key international scientists from the UK and international community to formulate the key requirements for an Urban Meteorological Research strategy. The workshop was jointly organised by University of Reading and the Met Office

Daily and annual cycle of urban heat island occurrence in Łódź

During the period of 1992-1996 the meteorological station belonging to Department of Meteorology and Climatology, University of Łódź worked in the city centre of Łódź. The station was equiped with standard instruments and attended as a normal climatological station. The difference between air temperature in a city centre (Tu) and on the outskirts of Łódź on the local airport Łódź-Lublinek (Tr) was used to define the intensity of urban heat island. Its significant diurnal and annual periodicity have been observed. The biggest positive differences have always been noticed during the summer nights when the weather conditions are most suitable to the creation and duration of heat surplus in city. During winter, UHI is a scarcity and its intensity is much less significant in average (it is caused by rise of wind's speed during this season). The relations between intensity of um in Łódź, wind speed and cloudiness have also been analyzed.W latach 1992-1996 działała w centrum Łodzi Miejska Stacja Meteorologiczna Zakładu Meteorologii i Klimatologii UL, wyposażona w standardowe przyrządy i obsługiwana w reżimie pracy stacji klimatologicznej. Dla określenia intensywności miejskiej wyspy ciepła wykorzystano różnicę temperatury powietrza pomiędzy stacją śródmiejską a stacją zamiejską - w tym przypadku lotniskową stacją synoptyczną Lódź-Lublinek (fu-Tr). Występowanie miejskiej wyspy ciepła cechuje się wyraźną cyklicznością dobową i roczną. Największe dodatnie różnice notowano zawsze w terminie nocnym w okresie lata - najczęściej występują wówczas warunki do tworzenia się i trwania przez całą noe nadwyżki ciepła w mieście. W zimie mwc zaznacza się rzadziej, a jej intensywność nie jest z reguły duża, co wynika ze wzmoźonej prędkości wiatru o tej porze roku. Określono związek natężenia miejskiej wyspy ciepła w Łodzi z wielkościPraca została wykonana przy finansowym wsparciu Komitetu Badań Naukowych - grant nr 6P04E 036 08

Hydrochemical zoning of valley peatlands as a result of water supply conditions: examples from Poland

The chemical composition of water from two peatlands was investigated. Both peatlands, which are nature reserves, are located in central Poland in the Widawka and Rawka River valleys. The study concerned groundwaters, peat waters from different depths, and waters from draining ditches. The research permitted determination of the hydrochemical zoning of the peatlands resulting from the complex character of the water supply. The hydrochemical interpretation of surface waters outflowing alongside the ditches, in terms of their similarity to particular zones, provides an insight into the water-feeding structure of the peatlands. In the evaluation, hydrochemical indicators were applied, which have been used in hydrogeological studies. They are based on equivalent concentrations of the major ions: sodium, calcium, chlorides, and sulphates, selected from other hydrochemical elements by means of principal component analysis (PCA), conducted individually for each peatland. The analyses showed a high contribution of unconfined and confined groundwaters to the water supply, with clearly distinguishable zones, in terms of their transit through the structures of the peatlands

Ekstremalne warunki opadowe w Łodzi w okresie 1931-1995

W opracowaniu analizowano szereg dobowych sum opadu z Łodzi z okresu 1931-1995. Przedstawiono roczny bieg częstości występowania dni bez opadu i z opadem w poszczególnych przedziałach wartości. Stwierdzono, że pojawienie się opadu zależy w większym stopniu od charakteru cyrkulacji niż od kierunku napływu mas. Badano długoletnią zmienność częstości dni bez opadu, dni z sumą opadu powyżej 10 mm i największej dobowej sumy opadu w roku. Pokazano, że najwyższe dobowe sumy opadu pojawiają się w dniach o cyrkulacji EoRecord of daily precipitation totals from Łódź from the period 1931-1995 has been analysed. The annual courses of frequencies of days without precipitation and with precipitation in particular ranges were presented. It was shown that occurrence of precipitation is stronger related to the character of circulation than to direction of air mass advection. Long-term variability of frequencies of days without precipitation, days with totals exceeding 10 mm/day and long-term variability of the highest daily total during the year were analysed. It was shown that the highest daily totals occur in day with circulation of type Eo

Intensywność miejskiej wyspy ciepła w Łodzi w okresie zimowym oraz jej prosty model

W opracowaniu przedstawiono dobowy bieg intensywności miejskiej wyspy ciepła w Łodzi w okresie zimowym. Bazę doświadczalną stanowią wyniki pomiarów temperatury powietrza na dwóch posterunkach, miejskim i zamiejskim, z okresu od 26 grudnia 1996 do 4 lutego 1997. Do analizy wybrano 17 nocy z dobrze rozwiniętą miejską wyspą ciepła. W ciągu nocy róźnice między temperaturą w centrum Łodzi a terenami zamiejskimi wzrastają początkowo bardzo gwałtownie, następnie łagodnie osiągają maksimum tuź przed wschodem słońca. Podobieństwo przebiegów temperatury na obu stacjach umoźliwiło skonstruowanie prostego modelu czasowego rozwoju intensywności miejskiej wyspy ciepła bazującego na zmianach temperatury na obszarach zamiejskich.W latach 1992-1996 działała w centrum Łodzi Miejska Stacja Meteorologiczna Zakładu Meteorologii i Klimatologii UL, wyposażona w standardowe przyrządy i obsługiwana w reżimie pracy stacji klimatologicznej. Dla określenia intensywności miejskiej wyspy ciepła wykorzystano różnicę temperatury powietrza pomiędzy stacją śródmiejską a stacją zamiejską - w tym przypadku lotniskową stacją synoptyczną Lódź-Lublinek (fu-Tr). Występowanie miejskiej wyspy ciepła cechuje się wyraźną cyklicznością dobową i roczną. Największe dodatnie różnice notowano zawsze w terminie nocnym w okresie lata - najczęściej występują wówczas warunki do tworzenia się i trwania przez całą noe nadwyżki ciepła w mieście. W zimie mwc zaznacza się rzadziej, a jej intensywność nie jest z reguły duża, co wynika ze wzmoźonej prędkości wiatru o tej porze roku. Określono związek natężenia miejskiej wyspy ciepła w Łodzi z wielkością zachmurzenia ogólnego i prędkością wiatru w poszczególnych terminach obserwacyjnych.During the period of 1992-1996 the meteorological station belonging to Department of Meteorology and Climatology, University of Łódź worked in the city centre of Łódź. The station was equiped with standard instruments and attended as a normal climatological station. The difference between air temperature in a city centre (Tu) and on the outskirts of Łódź on the local airport Łódź-Lublinek (Tr) was used to define the intensity of urban heat island. Its significant diurnal and annual periodicity have been observed. The biggest positive differences have always been noticed during the summer nights when the weather conditions are most suitable to the creation and duration of heat surplus in city. During winter, UHI is a scarcity and its intensity is much less significant in average (it is caused by rise of wind's speed during this season). The relations between intensity of um in Łódź, wind speed and cloudiness have also been analyzed