Probability Model of Rainfall Extremes Under a Changing Climate

openGli aumenti previsti delle future precipitazioni estreme a causa del cambiamento climatico antropogenico evidenziano la necessità di proiezioni robuste. Tuttavia, i principali drivers di questo aumento e il suo preciso tasso di incremento rimangono incerti. Numerosi studi hanno cercato relazioni empiriche per identificare come i percentili delle distribuzioni delle precipitazioni variano con la temperatura, ma gli esatti cambiamenti nella distribuzione della probabilità degli eventi estremi in condizioni di riscaldamento climatico rimangono poco compresi. Per colmare questa lacuna, questa tesi propone di riformulare la Distribuzione Metastatistica dei Valori Estremi (MEVD), che tiene conto dell'intera distribuzione degli eventi "ordinari" sottostanti, per incorporare esplicitamente la loro dipendenza dalla temperatura. Sfruttando lunghe serie storiche di precipitazione e temperatura, sono studiate la loro relazione probabilistica e l'influenza della termodinamica e della circolazione atmosferica a grande scala sulla loro relazione. I risultati indicano che il cambiamento nelle precipitazione giornaliere estreme non può essere attribuito esclusivamente alla termodinamica ma anche gli effetti dinamici devono essere considerati. Al contrario, alla scala oraria, emergono evidenze che i cambiamenti nelle precipitazioni estreme, prevalentemente guidati dalla termodinamica, si manifestano come una relazione esponenziale tra i parametri della distribuzione degli eventi "ordinari" e la temperatura, portando all'intensificazione e all'aumento della frequenza di eventi di precipitazioni orarie estreme in condizioni di riscaldamento.Expected increases in future extreme precipitation due to anthropogenic climate change highlight the need for robust projections. However, the main drivers of this increase and its precise rate remain uncertain. Numerous studies have sought empirical relationships to identify how precipitation percentiles scale with temperature, but the exact changes in the probability distribution of extremes under a warming climate remain poorly understood. To address this gap, this thesis proposes to reformulate the Metastatistical Extreme Value Distribution (MEVD), which accounts for the full distribution of underlying "ordinary" events, to explicitly incorporate their temperature dependence. Leveraging long historical records of precipitation and temperature, their probabilistic relationship and the influence of thermodynamics and large-scale circulation on their relationship are investigated. The results indicate that the change in daily precipitation extremes cannot be solely attributed to thermodynamics; rather, the dynamical effects must also be considered. Conversely, at the hourly scale, evidence emerges that changes in precipitation extremes, predominantly driven by thermodynamics, manifest as an exponential relationship between the parameters of the distribution of the “ordinary” events and temperature, leading to the intensification and the increase in the frequency of hourly precipitation extremes under warming conditions

Modeling Infection with Multi-agent Dynamics

Developing the ability to comprehensively study infections in small populations enables us to improve epidemic models and better advise individuals about potential risks to their health. We currently have a limited understanding of how infections spread within a small population because it has been difficult to closely track an infection within a complete community. The paper presents data closely tracking the spread of an infection centered on a student dormitory, collected by leveraging the residents' use of cellular phones. The data are based on daily symptom surveys taken over a period of four months and proximity tracking through cellular phones. We demonstrate that using a Bayesian, discrete-time multi-agent model of infection to model real-world symptom reports and proximity tracking records gives us important insights about infec-tions in small populations

How large should whales be?

The evolution and distribution of species body sizes for terrestrial mammals is well-explained by a macroevolutionary tradeoff between short-term selective advantages and long-term extinction risks from increased species body size, unfolding above the 2g minimum size induced by thermoregulation in air. Here, we consider whether this same tradeoff, formalized as a constrained convection-reaction-diffusion system, can also explain the sizes of fully aquatic mammals, which have not previously been considered. By replacing the terrestrial minimum with a pelagic one, at roughly 7000g, the terrestrial mammal tradeoff model accurately predicts, with no tunable parameters, the observed body masses of all extant cetacean species, including the 175,000,000g Blue Whale. This strong agreement between theory and data suggests that a universal macroevolutionary tradeoff governs body size evolution for all mammals, regardless of their habitat. The dramatic sizes of cetaceans can thus be attributed mainly to the increased convective heat loss is water, which shifts the species size distribution upward and pushes its right tail into ranges inaccessible to terrestrial mammals. Under this macroevolutionary tradeoff, the largest expected species occurs where the rate at which smaller-bodied species move up into large-bodied niches approximately equals the rate at which extinction removes them.Comment: 7 pages, 3 figures, 2 data table

Procjena koncentracije Cu u tlu i vrijednost pozadinskog praga u Crvenici iz Dalmacije

The aims of this study were (i) to assess the soil Cu concentration in the mineral A horizon and cambic Bw horizon, (ii) to determine the background threshold value (BTV), and (iii) to quantify the differences between the horizons in terra rossa soil from Dalmatia. A total of 128 samples from 64 soil profiles located on terrains used for non-agricultural purposes were analysed for aqua regia soluble Cu concentration. The soils were classified according to the Croatian Soil Classification System and World Reference Base for Soil Resources as terra rossa soil and Chromic and Rhodic Cambisols. The median value of Cu concentration in A horizon (CuA) and cambic Bw horizon (CuB) were 34.9 and 36.1 mg/kg, respectively, and ranged between 16.2 and 69.5 mg/kg in the CuA and from 17.0 to 73.0 mg/kg in the CuB horizon. The estimated BTV for CuA varied between 43.6 and 58.4 mg/kg depending on the calculation method applied. The median ratio CuA/CuB of 0.96 was close to identical. The Wilcoxon matched pairs signed rank test and the Hodges-Lehmann estimator showed that the median difference in Cu concentration between the CuA and CuB was very small (-1.78 mg/ kg). Mentioned statistical evidence on the small differences in Cu concentration between the horizons suggests that Cu concentrations measured in the Bw horizon can be considered a “local background” for the samples collected in A horizon and its utilization in screening terra rossa soil contamination can be suggested.Ciljevi ovog istraživanja bili su (i) odrediti koncentraciju bakra u mineralnom A i kambičnom Bw horizontu, (ii) odrediti pozadinsku vrijednost praga (PVP) te, (iii) kvantificirati razlike između horizonata u Crvenici iz Dalmacije. Ukupno 128 uzoraka iz 64 profila tla lociranih na terenima koji se koriste u nepoljoprivredne svrhe, analizirano je na koncentraciju topljivog Cu u zlatotopki. Tla su klasificirana prema Hrvatskom sustavu klasifikacije tala i Svjetskoj referentnoj bazi za resurse tla kao Crvenica, odnosno Chromic i Rhodic Cambisol. Vrijednosti medijane za koncentraciju Cu u A horizontu (CuA) i kambičnom Bw horizontu (CuB) bile su 34,9, odnosno 36,1 mg/kg, a kretale su se između 16,2 i 69,5 mg/kg u CuA i od 17,0 do 73,0 mg/kg u CuB horizontu. Utvrđeni PVP za CuA varirao je između 43,6 i 58,4 mg/kg, ovisno o primjenjenoj metodi određivanja. Medijana omjera CuA/CuB od 0,96 bila je blizu identičnom. Wilcoxonov test usklađenih parova i Hodges-Lehmann metoda su pokazali da je razlika medijana Cu koncentracija između CuA i CuB bila vrlo mala (-1,78 mg/ kg). Navedeni statistički dokazi o malim razlikama u koncentraciji Cu između horizonata sugeriraju da se koncentracije Cu izmjerene u kambičnom horizontu mogu smatrati "lokalnom pozadinom" za uzorke prikupljene u A horizontu i može se predložiti njihova upotreba u probiranju onečišćenja Crvenica

Chemical Tagging of Solar Neighborhood Kinematic Streams

Elemental abundance measurements for lanthanum, europium, and iron are presented for 504 stars in the solar neighborhood. The bulk of the data are planet search spectra taken with HIRES on the Keck I telescope at R=50,000, but a subset of 45 kinematically selected stars were observed on the Harlan J. Smith Telescope at McDonald Observatory at R=60,000 and S/N=100 at the 3988 angstrom lanthanum line and S/N=250 around 5240 angstrom near the iron lines. Statistical analyses of stellar kinematics in the solar neighborhood reveal much kinematic substructure in the disk, though it is not readily apparent whether this substructure is extragalactic or dynamical in origin. Much of the substructure can be quickly identified as well known moving groups of stars such as the Hercules, Sirius, and Hyades stellar streams. Additionally, the subset of kinematically selected stars observed at McDonald Observatory are members of a stellar stream putatively identified by Amina Helmi as part of a merger remnant. Taking advantage of a large data set and a homogeneous spectral analysis, a Kolmogorov-Smirnov hypothesis test is applied to investigate the possibility that these kinematic structures are chemically distinct from the Galactic Disk. In all cases, the kinematic streams have chemistries roughly consistent with the Galactic disk trends, although the statistical analyses suggest some subtle variations. The accretion hypothesis is not completely ruled out for Helmi's stream, but the chemical variations are interpreted primarily in terms of dynamical effects