Ilija Arsenić

Sensitivity of soil surface temperature in a force‐restore equation to heat fluxes and deep soil temperature

The ‘force-restore’ approach is commonly used in order to calculate the surface temperature in atmospheric models. A critical point in this method is how to calculate the deep soil temperature which appears in the restore term of the ‘force-restore’ equation. If the prognostic equation for calculating the deep soil temperature is used, some errors in surface temperature calculation and consequently in partitioning the surface energy and land surface water can be introduced. Usually, these errors should appear as a result of incorrect parameterization of surface energy terms in the prognostic equation based on ‘force-restore’ approach. In this paper, the sensitivity of the ‘force-restore’ model for surface temperature to the: (a) changes of soil heat flux; (b) variations of deep soil temperature and (c) changes in soil water evaporation is examined. In addition, the impact of the deep soil temperature variations on partitioning the surface energy and land surface water is discussed. Finally, a new procedure for calculating the deep soil temperature based, on climatological data of soil temperature and its exponential attenuation in the deep soil layers is suggested. All numerical experiments with the LAPS land surface scheme were performed using two data sets, obtained from the micrometeorological measurements over a bare soil at Rimski Sancevi (Yugoslavia), RS, and Caumont (France), HAPEX. Copyright

Wind profile within the forest canopy and in the transition layer above it

Abstract The forest as an underlying surface has to be considered in atmospheric models of different scales. Experimental evidence shows that there can be a significant variation of the wind profile within the forest and in the so-called transition layer above it. Experimentally observed wind speed is often found below as indicated by the wind speed profile obtained by: (a) the logarithmic relationship in the transition layer and (b) K theory within the forest. This situation can seriously disturb the real physical picture concerning the transfer of momentum, heat and water vapour from the surface into the atmosphere. In order to minimise the foregoing problems, we have suggested an empirical expression for the wind profile in the transition layer above the forest as well as the expressions for the wind profile and turbulent momentum transfer coefficient within the forest canopy layer. Additionally, for the proposed wind profiles, the expressions for the displacement height, roughness length and parameters are determined as functions of the forest structural characteristics using continuity conditions and a simple mass conservation hypothesis. The validity of the proposed expressions was checked using the micrometeorological measurements from the experimental sites in the Thetford Scots pine forest in Norfolk, United Kingdom and in the Ponderosa pine forest at the Shasta Experimental Forest, California, USA.

NEOPLANTA : A short description of the first serbian UV index model

Abstract A numerical model called “NEOPLANTA” for estimating solar UV irradiance and UV index under cloud-free conditions is being developed and tested at the University of Novi Sad in Serbia. In this paper, the model features, calculation procedure, and input parameters are described. Effects of the absorption of UV radiation by O3, SO2, and NO2 and absorption and scattering by aerosol as well as the air molecules in the atmosphere are included. The performance of the model has been tested with respect to its capability of UV index, which is a weighted integral between 280 and 400 nm of the solar irradiance reaching the ground. For this test 10-day data measured during the spring and summer in 2003, 2004, and 2005 are used. Data are recorded by the Yankee UVB-1 biometer located at the Novi Sad university campus (45.33°N, 19.85°E; 84 m MSL). Error analyses indicate that the modeled values agree well with the observations.

A Roughness Sublayer Wind Profile Above A Non-Uniform Surface

In atmospheric models for different scales the underlying surface consists of patches of bare soil and plant communities with different morphological parameters. Experimental evidence indicates that there is a significant departure of the wind profile above a vegetative surface from that predicted by the logarithmic relationship, which gives values that are greater than those observed. This situation can seriously disturb the physical picture concerning the transfers of momentum, heat and water vapour from the surface into the atmosphere.The intention of this paper is to generalise the calculation of exchange of momentum between the atmosphere and a non-homogenous vegetative surface, and to derive a general equation for the wind speed profile in a roughness sublayer under neutral conditions. Furthermore, these results are extended to non-neutral cases. The suggested expression for the wind profile is compared with some earlier approaches and the observations obtained above a broad range of plant communities.

Novel measures based on the Kolmogorov complexity for use in complex system behavior studies and time series analysis

Abstract We propose novel metrics based on the Kolmogorov complexity for use in complex system behavior studies and time series analysis. We consider the origins of the Kolmogorov complexity and discuss its physical meaning. To get better insights into the nature of complex systems and time series analysis we introduce three novel measures based on the Kolmogorov complexity: (i) the Kolmogorov complexity spectrum, (ii) the Kolmogorov complexity spectrum highest value and (iii) the overall Kolmogorov complexity. The characteristics of these measures have been tested using a generalized logistic equation. Finally, the proposed measures have been applied to different time series originating from: a model output (the biochemical substance exchange in a multi-cell system), four different geophysical phenomena (dynamics of: river flow, long term precipitation, indoor 222Rn concentration and UV radiation dose) and the economy (stock price dynamics). The results obtained offer deeper insights into the complexity of system dynamics and time series analysis with the proposed complexity measures.

A study on the effects of subgrid-scale representation of land use on the boundary layer evolution using a 1-D model

Abstract A soil–vegetation–atmosphere transfer scheme based on a one-dimensional boundary layer model has been developed to study the sensitivity of boundary layer growth on the surface temperature fields and land-use types. Full interaction between the surface and atmosphere is achieved by representing the surface and turbulent mixing processes by using a Land Air Parameterization Scheme (LAPS) and the Blackadars local closure PBL scheme. Sensitivity tests are performed by simulating planetary boundary layer structures over different underlying surfaces, soil textures and soil moisture contents using the meteorological data for July 17, 1999 in Philadelphia, PA. Also, a simpler surface parameterization used in the MM5 model results in a significantly higher surface temperature as well as the PBL depth over the urban area than those obtained by the LAPS parameterization in which a new method, including a combination of aggregated fluxes and parameters in calculating the surface temperature, is applied.

Climate Predictions: The Chaos and Complexity in Climate Models

Some issues which are relevant for the recent state in climate modeling have been considered. A detailed overview of literature related to this subject is given. The concept in modeling of climate, as a complex system, seen through Godels Theorem and Rosens definition of complexity and predictability is discussed. It is pointed out to occurrence of chaos in computing the environmental interface temperature from the energy balance equation given in a difference form. A coupled system of equations, often used in climate models is analyzed. It is shown that the Lyapunov exponent mostly has positive values allowing presence of chaos in this systems. The horizontal energy exchange between environmental interfaces, which is described by the dynamics of driven coupled oscillators, is analyzed. Their behavior and synchronization, when a perturbation is introduced in the system, as a function of the coupling parameters, the logistic parameter and the parameter of exchange, was studied calculating the Lyapunov exponent under simulations with the closed contour of N=100 environmental interfaces. Finally, we have explored possible differences in complexities of two global and two regional climate models using their output time series by applying the algorithm for calculating the Kolmogorov complexity.

A numerical study of synchronization in the process of biochemical substance exchange in a diffusively coupled ring of cells

In this paper we numerically investigate a model of a diffusively coupled ring of cells. To model the dynamics of individual cells we propose a map with cell affinity, which is a generalization of the logistic map. First, the basic features of a one-cell system are studied in terms of the Lyapunov exponent, Kolmogorov complexity and Sample Entropy. Second, the notion of observational heterarchy, which is a perpetual negotiation process between different levels of the description of a phenomenon, is reviewed. After these preliminaries, we study how the active coupling induced by the consideration of the observational heterarchy modifies the synchronization property of the model with N=100 cells. It is shown numerically that the active coupling enhances synchronization of biochemical substance exchange in several different conditions of cell affinity.

Simulation of air temperature inside the canopy by the LAPS surface scheme

Abstract A land–air parameterization scheme (LAPS) describes water vapour, heat and momentum transfer between the land surface and the atmosphere. The scheme is designed as a software package, which can be run as part of an atmospheric, hydrological or ecological model, or as a stand-alone model that operates with seven prognostic variables and 16 morphological and physiological input parameters. Such large number of parameters provides reliable simulation of diurnal courses of meteorological elements inside the crop. In this paper, for simulating the diurnal course of air temperature inside a sunflower field, the LAPS scheme has been used. The results obtained are compared with the results of micrometeorological measurements of a sunflower experimental field of the Oil Crops Department at Rimski Sancevi (Yugoslavia) using data sets from 18 July to 24 July, 1998. The LAPS scheme was compared with two other surface schemes using canopy air temperature data derived from measured air temperature above a maize field at an experimental site in De Sinderhoeve (The Netherlands) for 18 August, 8 September, and 4 October 1988.

Kolmogorov Complexity Based Information Measures Applied to the Analysis of Different River Flow Regimes

We have used the Kolmogorov complexities and the Kolmogorov complexity spectrum to quantify the randomness degree in river flow time series of seven rivers with different regimes in Bosnia and Herzegovina, representing their different type of courses, for the period 1965–1986. In particular, we have examined: (i) the Neretva, Bosnia and the Drina (mountain and lowland parts), (ii) the Miljacka and the Una (mountain part) and the Vrbas and the Ukrina (lowland part) and then calculated the Kolmogorov complexity (KC) based on the Lempel–Ziv Algorithm (LZA) (lower—KCL and upper—KCU), Kolmogorov complexity spectrum highest value (KCM) and overall Kolmogorov complexity (KCO) values for each time series. The results indicate that the KCL, KCU, KCM and KCO values in seven rivers show some similarities regardless of the amplitude differences in their monthly flow rates. The KCL, KCU and KCM complexities as information measures do not “see” a difference between time series which have different amplitude variations but similar random components. However, it seems that the KCO information measures better takes into account both the amplitude and the place of the components in a time series.