Comparison of GPS TEC with modelled values from IRI 2016 and IRI-PLAS over Istanbul,Turkey

The Total Electron Content (TEC) prediction performances of the empirical IRI model and IRI-PLAS model were investigated by comparing the GPS-based TEC values provided by the IONOLAB group. TEC values were obtained on equinox (March 21 and September 23) and solstice (June 21, and December 21) days in low (2009), medium (2012) and high (2015) solar activity periods at Istanbul, Turkey. The prediction performances of the models were statistically analyzed based on the differences between the GPS-TEC and the empirical models, considering the maximum and minimum deviations, the correlation analysis and the root mean square error (RMSE). As a result of the investigation, it is seen that the empirical models have similar predictive performances when the plasmaspheric effects are neglected, and the IRI-PLAS estimations are generally a little closer to the observed GPS-TEC values than all options of IRI-2016 model. Also, it can be said that “IRI2001”, one of the IRI-2016’s “topside” options, can make better predictions than other options and “IG” solar proxy option of IRI-PLAS model is a more appropriate option than the others in TEC calculations over Istanbul, Turkey.     

Late Quaternary evolution of the Çanakkale Strait region (Dardanelles, NW Turkey): implications of a major erosional event for the postglacial Mediterranean-Marmara Sea connection

Seismic and bathymetric data from the Çanakkale Strait and its extensions onto the shelves of the Marmara and Aegean seas indicate that the strait was formed mainly by an erosional event. Four seismic units are observed on seismic profiles. The lower two of these (units 4 and 3) constitute the basement of a regionally widespread erosional unconformity (ravinement), which developed during marine isotope stage 2 (MIS 2). The two upper units (units 2 and 1), which overlie the ravinement surface, form a higher-order sequence. Sequence stratigraphic analysis indicates that units 2 and 1 deposited as lowstand and highstand systems tracts respectively, since the end of MIS 2. The transgressive systems tract is represented by a major erosional event which occurred throughout the Çanakkale sill area when the Mediterranean-Marmara Sea connection and, hence, the Çanakkale Strait was formed. The existence of the erosive ?arköy Canyon along the shelf edge of the southern Marmara Sea demonstrates that the flow direction causing the erosion was from south to north, thus proving that it was produced by Mediterranean water flowing over the sill into the Marmara Sea basin.     

Semi-empirical prediction method for monthly precipitation prediction based on environmental factors and comparison with stochastic and machine learning models

ABSTRACT

Precipitation prediction is central in hydrology and water resources planning and management. This paper introduces a semi-empirical predictive model to predict monthly precipitation and compares its predictive skill with those of machine learning (ML) methods. The stochastic method presented herein estimates monthly precipitation with one-step-ahead prediction properties. The ML predictive skill of the algorithms is evaluated by predicting monthly precipitation relying on the statistical association between precipitation and environmental and topographic factors. The semi-empirical predictive model features non-negative matrix factorization (NMF) for investigating the influence of multiple predictor variables on precipitation. The semi-empirical predictive model’s parameters are optimized with the hybrid genetic algorithm (GA) and Levenberg-Marquardt algorithm (LM), or GALMA, yielding a validated model with high predictive skill. The methodologies are illustrated with data from Hubei Province, China, which comprise 27 meteorological station datasets from 1988–2017. The empirical results provide valuable insights for developing semi-empirical rainfall prediction models.     

Orthopyroxene as a geospeedometer: Thermal history of Kapoeta,Old Homestead 001, and Hughes 002 howardites

Abstract— Single crystals of orthopyroxene from small fragments of the Kapoeta, Old Homestead 001, and Hughes 002 howardites were studied by x‐ray diffraction and microprobe analyses. The Fe‐Mg equilibrium distribution coefficients k_D of the crystals were used to calculate the closure temperatures (T_c) using the calibration by Stimpfl et al. (1999). The compositions, the presence of exsolved augite lamellae, and the T_c values (from 365 to 385 °C) obtained for Kapoeta orthopyroxene s suggest that our fragment comes from a diogenitic cumulate clast. The more Fe‐rich composition, the absence of exsolved lamellae, and the higher T_c values (from 583 to 605 °C) measured in the Old Homestead 001 orthopyroxenes suggest that this fragment comes from a cumulitic clast affected by fast cooling at high temperature. For the Hughes 002 orthopyroxenes, close in composition to Old Homestead 001, the different T_c values (339, 358, and 607 °C) recorded by the various crystals and the presence of augite lamellae in the crystals with the lowest T_c support the hypothesis that this howardite sample is an unheated breccia containing a mixture of cumulitic orthopyroxenes with different thermal histories.     

The non‐trivial problem of meteorite pairing

Abstract— Pairing is the procedure of identifying fragments of a single meteorite fall (that were separated during atmospheric passage or during terrestrial history) by establishing the similarity of two or more meteorite fragments. We argue that pairing is governed by two principles, that only a single mismatch of properties is required to refute a proposed pairing, and that virtually all pairings bear some degree of uncertainty. Using data distributions for modern falls, we take a probability approach to estimate degrees of certainty associated with proposed pairings, emphasizing the importance of unusual features. For new pairing criteria or new analytical additions to old criteria, the degree of variation within individual meteorites must be delineated and the degree of variation within meteorite classes must be quantified. Criteria for pairing can be divided into (1) parent body history indicators, (2) meteoroid space history indicators, and (3) terrestrial history indicators. Included in these categories are 11 specific criteria, including petrographic textures, mineralogy and mineral composition, terrestrial age estimates, cosmic‐ray exposure ages, and natural thermoluminescence (TL) levels. Not all criteria are applicable to all meteorite types. About 2275 pairings suggested in the literature have been subjected to this analysis. Many literature pairings, especially those involving common meteorite types, bear large uncertainties due to lack of data.     

Histological alterations observed in Idotea balthica basteri audouin 1827 (Crustacea,Isopoda) exposed to the chronic effect of non-ionic detergents

Following extended exposure to eight non-ionic compounds, the crustacean isopod Idotea balthica basteri was studied by light microscopy and histoautoradiography. Cellular modifications were found in the nervous system, the gill pleopods, the digestive system, the gonads and the moulting gland. It is suggested that these modifications may eventually cause a variation in function and may even lead to the extinction of the species.     

Resorption process in Astypalaea Linea extensive region (Europa)

Whereas numerous extensive features, where new crust is created, are now well recognized on Europa's surface, those relevant to crust disappearance remain difficult to find. This work presents a reconstruction of the surface prior to Astypalaea Linea's emplacement (one of the features where new crustal material appears). We demonstrate that a scattered disappearance of crust takes place in an extensive region close to Astypalaea Linea. Physical processes invoked for disappearance are discussed: pressure melting may be responsible for the mobilization of surface material and its collapse down through the icy crust.     

The role of the NNW structural trend in the recent geodynamic evolution of north-eastern sicily and its volcanic implications in the etnean area

The seismic and eruptive events occurring in Eastern Sicily between 1978 and 1981 are analyzed with reference to the existence neoctectonic structures beginning with the Gulf of Patti earthquake (1978, Lower Tyrrhenian Basin). From this analysis, the geodynamic consistency of the movements developing along the NNW and NE trends becomes apparent. In particular, the relation between these two trends enables the authors to verify their previously elaborated deformation model for the Etnean area and to emphasize its coherence with the regional geodynamic context. Finally, the close connection is shown between the Etnean area and the NNW-SSE wrench zone breaking the Southern Calabro-Peloritan Arc.     

Microtremors and volcanic explosions at Stromboli (Aeolian Islands)

Seismic observations were carried out at Stromboli from October 16^th to 24^th, 1972. One three-component seismic station was set up at Semaforo Nuovo, about 2 km on the E of the crater plain. Seismic observations showed the occurrence of microtremors, with variable amplitude but constant frequency content, and different types of explosion earthquakes. Spectral and vibration orbit analyses of microtremors and quakes were made in order to infer their nature and the depth of origin. Changes in microtremor amplitudes corresponding to different phases of volcanic activity indicate that their study may be useful in forecasting strongly explosive volcanic phases at Stromboli.