Harry PavlopoulosAthens University of Economics and Business | AUEB · Department of Statistics
Harry Pavlopoulos
PhD 1991-Mathematics University of Maryland at College Park (UMCP), Maryland, USA
About
20
Publications
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Introduction
My current research aims to develop a stochastic framework for spatial down-scaling of time series of spatial or spatio-temporal aggregates of random fields, using dynamic multiplicative cascades driven by time-and-scale dependent stochastic generators based on the spectral multi-scaling (SMS) postulate. My publications in "Advances in Water Resources" (2011, 2014) outline such a framework, rendering SMS statistically diagnosed in time series of spatio-temporal accumulations of rain rate fields.
Additional affiliations
October 2005 - April 2006
May 2006 - June 2006
November 1993 - January 1995
Education
August 1985 - December 1991
August 1985 - December 1988
October 1981 - July 1985
Publications
Publications (20)
This paper is concerned with a novel version of the INAR(1) model, a non-linear auto-regressive Markov chain on ℕ, with innovations following a finite mixture distribution of Poisson laws. For , the stationary marginal probability distribution of the chain is overdispersed relative to a Poisson, thus making INAR(1) suitable for modeling time series...
Spectral multi-scaling postulates a power-law type of scaling of spectral distribution functions of stationary processes of spatial averages, over nested and geometrically similar sub-regions of the spatial parameter space of a given spatio-temporal random field. Presently a new framework is formulated for down-scaling processes of spatial averages...
Real data experiments show that, for large areas, the area average rain rate and the fraction of the area covered by rain rate above a fixed threshold are highly correlated. For the right choice of the threshold level the correlation can easily exceed 95% and may even reach 99%. This remarkable fact observed in nature is the basis for the so-called...
Considering log‐LFSN sequences Yn=eδ·Xn+εn∈ℤ, driven by non‐Gaussian one‐sided linear fractional stable noise (LFSN) Xnn∈ℤ with constant skewness intensity β0∈−1,1, for any δ∈ℝ−0 and ε∈ℝ, we show that the auto‐covariance function (ACVF) γYhh∈ℤ exists if and only if Xnn∈ℤ is persistent, with stability index α∈(1, 2), Hurst exponent H∈1/α1 and extrem...
Real data obtained from experiments performed at several regions on the globe show that rain rate, averaged over a large area, is approximately lognormally distributed. A theoretical justification for this fact is provided under some conditions. Rain rate is modeled as a temporally homogeneous diffusion process on the nonnegative semiaxis with appr...
In water-controlled environments, soil-water is the main actor in the hydrological cycle, just as the vegetation is the main actor in the dynamics of the ecosystems. The exchanges of water between soil and vegetation are driven by climate forcings like evaporative demand and rainfall. Evaporation is strongly related to air temperature, which exhibi...
Durations of rain events and drought events over a given region provide important information about the water resources of
the region. Of particular interest is the shape of upper tails of the probability distributions of such durations. Recent
research suggests that the underlying probability distributions of such durations have heavy tails of hyp...
In drylands the soil water availability is a key factor ruling the architecture of the ecosystem. The soil water reflects the exchanges of water among soil, vegetation, and atmosphere. Here, a dryland ecosystem is investigated through the analysis of the local interactions between soil water and vegetation forced by rainfall having seasonal and sto...
A minimal model of soil water–vegetation interaction in dryland ecosystems is developed as a vehicle to show how stochastic differential equations can be applied to this problem. In contrast to previous works, which assume a constant rainfall, the system is forced using stochastic rainfall, and the stationary probability distributions of the soil w...
Most of the recent work on rainfall data analyses and modeling has focused on either spatial or temporal variability. In this paper the structure of rainfall intermittence in space and time is investigated. Using a series of TOGA-COARE radar scans converted to maps of pixel rain rate over a tropical oceanic region of size 240 × 240 km2, regionally...
Most of the recent work on rainfall data analyses and modelling has focused on either spatial or temporal variability. In this paper the structure of rainfall intermittence in space and time is investigated. Using a series of TOGA-COARE radar scans converted to maps of pixel rain rate over a tropical oceanic region of size 240× 240 km2, regionally...
This article is concerned with the notion of duration of wet and dry epochs in stochastic processes of spatially averaged (instantaneous) rain rate over a given region. Gamma, Lognormal, and Inverse Gaussian parametric families of probability distributions have been considered as candidate models for the distribution of such durations. Goodness of...
Abstract-The estimation of hourly and daily solar radiation values on inclined surfaces starts
with the determination of the corresponding hourly values on the horizontal plane. To serve
the latter purpose the Meteorological Radiation Model was developed. The goal of the
model is to estimate solar radiation at places where there are not availabl...
Recent research has shown that, conditionally on rain, probability moments of instantaneous spatial averages of rain rate, over differently scaled subregions of a rain field, possess an interesting scaling property called wide sense multiscaling, with respect to magnifying spatial scales. This empirical fact, along with some theoretical considerati...
The estimation of hourly and daily solar radiation values on inclined surfaces starts with the determination of the corresponding hourly values on the horizontal plane. To serve the latter purpose the Meteorological Radiation Model was developed. The goal of the model is to estimate solar radiation at places where there are not available measuremen...
Moisture contained in an Eulerian atmospheric column is modelled as a stochastic process obtained from gluing together two diffusion processes along the branches of a certain graph. The glued diffusions are solutions of two stochastic differential equations, each one governing the budget of moisture content during dry and wet epochs of the column,...
A systematic approach is suggested for modeling the probability distribution of rain rate. Rain rate, conditional on rain and averaged over a region, is modeled as a temporally homogeneous diffusion process with appropiate boundary conditions. The approach requires a drift coefficient-conditional average instantaneous rate of change of rain intensi...
