Modification of the degree-day formula for diurnal meltwater generation and refreezing

Theoretical and Applied Climatology - The standard degree-day, temperature-index approach to calculating snowmelt generation and refreezing (the SDD method) is convenient and popularly used but...     

High-frequency acoustic backscattering characteristics for acoustic detection of the red tide species Akashiwo sanguinea and Alexandrium affine

Harmful algal blooms (HABs), caused by the overgrowth of certain phytoplankton species, have negative effects on marine environments and coastal fisheries. In addition to cell-counting methods using phytoplankton nets, a hydroacoustic technique based on acoustic backscattering has been proposed for the detection of phytoplankton blooms. However, little is known of the acoustic properties of HAB species. In this study, as essential data to support this technique, we measured the acoustic properties of two HAB species, Akashiwo sanguinea and Alexandrium affine, which occur in the South Sea off the coast of Korea. Due to the small size of the target, we used ultrasound for the measurements. Experiments were conducted under laboratory and field conditions. In the laboratory experiment, the acoustic signal received from each species was directly proportional to the cell abundance. We derived a relationship between the cell abundance and acoustic signal received for each species. The measured signals were compared to predictions of a fluid sphere scattering model. When A. sanguinea blooms appeared at an abundance greater than 3 500 cells/mL, the acoustic signals varied with cell abundance, showing a good correlation. These results confirm that acoustic measurements can be used to detect HAB species.     

Numerical modeling of thunderstorm

Summary A brief review of numerical models of thunderstorms is presented. The attempts of modeling these clouds have to deal with an extremely broad range of microphysical and dynamic processes. Basic concepts of thunderstorm modeling, 1-D, 2-D and 3-D models are considered. Particular attention is given to the basic equations and to the capability of these models to predict characteristics of the tunderstorms. A brief treatment is also given of hail growth in thunderstorm models.

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Zusammenfassung Im folgenden wird eine knappe Übersicht numerischer Gewittermodelle präsentiert. Bei der Modellierung von Gewitterwolken muß ein ausgesprochen weiter Bereich von mikrophysikalischen und dynamischen Prozessen beachtet werden. Grundkonzepte der Gewittermodellierung, 1-D-, 2-D- und 3-D-Modelle werden hierzu herangezogen. Besondere Aufmerksamkeit gilt dabei den Ausgangsgleichungen sowie den potentiellen Möglichkeiten dieser Modelle, Charakteristika der Gewitter vorherzusagen. Weiters wird auch das Hagelwachstum in Gewittermodellen kurz behandelt.

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With 8 Figures     

An inadvertent transport of the seeding material as a result of cloud modification

Successful seeding of clouds in weather modification experiments essentially depends on the seeding time and dynamics, amount of seeding material and location of the initial seeding area. In the present study, we focus on the influence of the initial seeding zone location on the transport of seeding agent material into the target cloud. In addition, the inadvertent transport of seeding material is analysed. During weather modification activities, a lot of seeding material can be transferred far from the seeding zone in a downwind direction. The primary motivation for this research was to prove this statement. We use a three-dimensional, mesoscale cloud-resolving model to achieve our goal. We performed sensitivity tests with respect to the distance between the mass centres of the initial seeding area and the cloud. Different seeding scenarios are analysed. Our principal findings are as follows: (1) For distances between the mass centres of the initial seeding area and the cloud below 2.5 km, all seeding agent material would be activated after a short time. For distances above 10 km, most of the seeding agent would remain inactivated, because horizontal transport of the seeding agent becomes more important than transport induced by the main updraft. For these scenarios, the seeding agent is injected in the cold peripheral part of the cloud. (2) Sensitivity tests show that the inactivated seeding agent would remain close to the seeding area if the seeding is performed below cloud base. This effect occurs even for large distances between the seeding area and the target cloud (>20 km) due to low-level convergence. Thus, this seeding method suppresses the inert seeding material from being transferred far from the seeding zone. (3) The complete seeding material stays inactivated if the seeding is performed between the ?8 and ?12°C isotherms in front of the increased reflectivity zone. As a consequence, it would be transferred far from its initial area. The cloud would not be able to capture the seeding agent even during its greatest lateral extent.     

Adapting project management method and ANFIS strategy for variables selection and analyzing wind turbine wake effect

We present a project management methodology designed for the selection of wind turbines wake effect most influential parameters, who need to run wind farm project for large energy conversion. Very frequently, the managers of these projects are not project management professionals, so they need guidance to have autonomy, using minimal time and documentation resources. Therefore, agile method is adapted to assist the project management. Wind energy poses challenges such as the reduction in the wind speed due to the wake effect by other turbines. If a turbine is within the area of turbulence caused by another turbine, or the area behind another turbine, the wind speed suffers a reduction and, therefore, there is a decrease in the production of electricity. In order to increase the efficiency of a wind farm, analyzing the parameters, which have influence on the wake effect, is one of the focal research areas. To maximize the power produced in a wind farm, it is important to determine and analyze the most influential factors on the wake effects or wake wind speeds since the effect has most influence on the produced power. This procedure is typically called variable selection, and it corresponds to finding a subset of the full set of recorded variables that exhibits good predictive abilities. In this study, architecture for modeling complex systems in function approximation and regression was used, based on using adaptive neuro-fuzzy inference system (ANFIS). Variable searching using the ANFIS network was performed to determine how the five parameters affect the wake wind speed. Our article answers the call for renewing the theoretical bases of wind farm project management in order to overcome the problems that stem from the application of methods based on decision-rationality norms, which bracket the complexity of action and interactions in projects.     

Chaotic Behavior of Soil Radon Gas and Applications

The soil ²²²Rn concentration non-linear patterns are investigated by the application of various chaos methodologies based on 70 272 measurement data from the East Anatolian Fault Zone, which is one of the world’s most active faults. Among these methodologies are Lyapunov exponent, surrogate data, rescaled range (R/S) analysis, Fourier spectrum, phase space reconstruction, mutual information, false nearest neighbors, and correlation dimension. The results indicate that the nonlinear dynamical approach is convenient for characterization and prediction of the ²²²Rn concentration dynamics, which are in turn usually used as an earthquake precursor. Behaviour of ²²²Rn gas is important in earthquake prediction researches.     

Seasonal and interannual variations in pigments in the Adriatic Sea

Spatial and temporal variability of pigments was studied from the CZCS satellite data and fromin situ chlorophyll and transparency for the period 1979-1985. The three Adriatic sites, Northern, Middle, and Southern Adriatic are differently influenced by meteorological, hydrological and oceanographic parameters. The differences between seasonalin situ chlorophyll and remotely sensed pigment concentrations (from CZCS satellite data) from the Adriatic are large in winter. Through the correlation analysis, pigments were compared to meteo-oceanographic and hydrological parameters from different Adriatic sites. The PCA (principal component analysis) was applied to the pigment data series and significant components were compared. Different correlations are obtained for warm and cold periods of the year pointing to seasonal differences in the underlying mechanism of pigment variability. The first PC is influenced mainly by temperature. In the warm period more parameters seem to influence the pigment field, than in the cold period. The pigments in the Adriatic are in good correlation to a number of hydrologic and meteo-oceanographic factors.     

Surfactant production by marine phytoplankton

Electrochemical methods based on adsorption of organic molecules at the mercury electrode-solution interface were used to investigate surfactant production by marine phytoplankton. Six species of marine phytoplankton, representing the classes of Bacillariophyceae, Haeptophyceae, Chlorophyceae and Cryptophyceae, were studied in batch cultures.Our experimental results showed that surfactants were produced in culture media by healthy exponential growing cells. The measured response was found to depend on the particular species and the age of the culture.Total surfactant content in culture media generally increased with cell density, while surfactants per cell showed an inverse relation to cell density. However, we found that in Cryptomonas culture medium, during the exponential growth, excretion of the insoluble surfactant material per cell was independent of cell concentration.In addition to culture experiments, surfactant activity at several northern Adriatic stations was measured during various stages of phytoplankton bloom. It was concluded that a significant part of surfactant activity in a seawater column is due to phytoplankton production.     

Chronology and sources of lunar impact bombardment

The Moon has suffered intense impact bombardment ending at 3.9 Gyr ago, and this bombardment probably affected all of the inner Solar System. Basin magnetization signatures and lunar crater size-distributions indicate that the last episode of bombardment at about 3.85 Gyr ago was less extensive than previously thought. We explore the contribution of the primordial Mars-crosser population to early lunar bombardment. We find that Mars-crosser population initially decays with a 80-Myr half-life, with the long tail of survivors clustering on temporarily non-Mars-crossing orbits between 1.8 and 2 AU. These survivors decay with half-life of about 600 Myr and are progenitors of the extant Hungaria asteroid group in the same region. We estimate the primordial Mars-crosser population contained about 0.01–0.02 Earth masses. Such initial population is consistent with no lunar basins forming after 3.8 Gya and the amount of mass in the Hungaria group. As they survive longer and in greater numbers than other primordial populations, Mars-crossers are the best candidate for forming the majority of lunar craters and basins, including most of the Nectarian system. However, this remnant population cannot produce Imbrium and Orientale basins, which formed too late and are too large to be part of a smooth bombardment. We propose that the Imbrian basins and craters formed in a discrete event, consistent with the basin magnetization signatures and crater size-distributions. This late “impactor shower” would be triggered by a collisional disruption of a Vesta-sized body from this primordial Mars-crossing population (Wetherill, G.W. [1975]. Proc. Lunar Sci. Conf. 6, 1539–1561) that was still comparable to the present-day asteroid belt a 3.9 Gya. This tidal disruption lead to a short-lived spike in bombardment by non-chondritic impactors with a non-asteroidal size–frequency distribution, in agreement with available evidence. This body (“Wetherill’s object”) also uniquely matches the constraints for the parent body of mesosiderite meteorites. We propose that the present-day sources of mesosiderites are multi-km-sized asteroids residing in the Hungaria group, that have been implanted there soon after the original disruption of their parent 3.9 Gyr ago.