Artificial Beach as a Structure for Protecting a Seacoast from Storm Surge Impact (Based on the Example of the Eastern Gulf of Finland)

Oceanology - A model of an artificial beach is proposed for protecting a seacoast subjected to erosion under significant storm surge impact. The beach profile properties are based on the Dean...     

Consideration of time-correlated errors in a Kalman filter applicable to GNSS

An algorithm for considering time-correlated errors in a Kalman filter is presented. The algorithm differs from previous implementations in that it does not suffer from numerical problems; does not contain inherent time latency or require reinterpretation of Kalman filter parameters, and gives full consideration to additive white noise that is often still present but ignored in previous implementations. Simulation results indicate that the application of the new algorithm yields more realistic and therefore useful state and covariance information than the standard implementation. Results from a field test of the algorithm applied to the problem of kinematic differential GPS demonstrate that the algorithm provides slightly pessimistic covariance estimates whereas the standard Kalman filter provides optimistic covariance estimates.     

Budget of sediments and forecast of long-term coastal changes

A method for predicting the coast evolution based on the calculated estimates of the components of the sediment budget is discussed. The approaches outlined in a series of previous publications of the author [9, 10, 11] are further developed. The prerequisites and concepts used as the basis of the suggested method for forecasting are characterized. The sediment budget parameters under typical conditions are presented. The contributions of natural processes and the anthropogenic impact are compared. Different approaches for calculating the principal sediment budget components, including the cross-shore flux through the lower boundary of the coastal zone, the eolian flux of sand material through the upper limit of the coastal zone, and the alongshore sediment flux gradients, are considered. The examples of forecasting the development of coasts in the Baltic and Kara seas and the Sea of Okhotsk are given for the period from 100 to 500 years. The results obtained show that, in the case of a balanced budget of the sediments, the future behavior of the coast would be mainly governed by the variations in the sea level. This factor is capable of determining the changes in the coastline, whose recession and advancing would depend on the rate of the sea level rise. Under specific conditions, an enhanced sea level rise can trigger destructive processes (for example, the erosion of a coastal bar or the thermal abrasion of a cliff). In the case of a strong imbalance in the sediment budget, sea-level changes play a subordinate role.     

Variations in the concentration of mesospheric ozone during the total solar eclipse of March 29, 2006, from microwave radiometric data

We present the results of microwave observations of the ozone content variability in the upper stratosphere and lower mesosphere during a total solar eclipse of March 29, 2006 at the Kislovodsk high-altitude scientific station. An increase in the concentration of mesospheric ozone was recorded during the eclipse. At a height of 60 km, the ozone concentration increased by 40%, which is close to the value of diurnal ozone variations.     

Low reproductive success for copepods during a bloom of the non‐aldehyde‐producing diatom Cerataulina pelagica in the North Adriatic Sea

Egg production rates and/or hatching success in the copepods Acartia clausi, Calanus helgolandicus and Temora longicornis were negatively affected by a late spring (May–June 2003) phytoplankton bloom in the North Adriatic Sea, dominated mainly by the large diatom Cerataulina pelagica. Highest total concentrations of 3.3·10⁴ cells·ml^?1 were located in the vicinity of the Po River, which also corresponded to the area where the highest numbers of phaeophorbides were measured (0.779, 0.528 and 0.419 μg·l^?1, respectively, compared to an average of the remaining stations of 0.183 ± 0.049 SD), suggesting some grazing on the bloom. Phytoplankton biomass in terms of carbon was dominated by diatoms, representing on average 42% of total phytoplankton carbon and more than 80% at several stations. Cerataulina pelagica, Cyclotella spp., Chaetoceros spp. and small unidentified centric diatoms dominated the diatom community numerically but C. pelagica was by far the dominant diatom in terms of carbon due to its large cell size. This species represented more than 60% of the diatom biomass at nine of the 14 stations sampled, and was absent only at one station, which was the most offshore station sampled during the cruise. Although polyunsaturated aldehydes (PUAs) were not detected, other oxylipins which are hydroxy and keto derivatives of eicosapentaenoic and docosahexaenoic acids that affect copepod reproduction were found in these samples. Hence, we can attribute the negative impact of diatoms not only to PUAs, as previously believed, but also to these compounds. This is the first direct evidence of the presence of oxylipins other than PUAs in marine blooms dominated by diatoms.     

On Increasing the Accuracy of Star Trackers to Subsecond Levels

Modern star trackers are based on photodetector arrays such as CCD or CMOS arrays. The accuracy of commercially available devices is ~1–3 arcseconds. However, the development of the space industry calls for higher orientation accuracies, which are needed in laser space communications, monitoring of near-Earth space and space debris, high-precision global mapping, and remote sensing of the Earth. The problems associated with enhancing the accuracy of modern star trackers are discussed.     

Determination of Non-gravitational Effects in the Motion of Near-Sun Objects 321P, 322P, 323P,and 342P

At the beginning of this century, the SOHO space observatory discovered near-Sun comets with perihelion distances q ≈ 0.05 AU, which remained observable over several close encounters with the Sun. This became one of the surprises in studying the small bodies of the Solar System. Currently, there are objects that have already been observed in four (342P) and five (321P, 322P, and 323P) apparitions. In the present work, the estimates of nongravitational effects are obtained for these objects based on the pair-wise linkage of the apparitions. The calculations show that the observations of these objects are poorly represented if solely the gravitational forces are considered. The magnitude of nongravitational effects in the semimajor axis noticeably changes with time. The motion of all comets is significantly affected by the components of nongravitational forces that are perpendicular to the orbital plane.     

On the Trajectories of Asteroid Encounters with the Earth for 2015 RN35 and Apophis

A great number of probable encounters of asteroid 2015 RN35 with the Earth have been found; many of them were unknown earlier. The main characteristics and properties of the corresponding trajectories have been obtained. Probable impacts of the asteroid Apophis with the Earth are also discussed. The results suggest that the multitudes of potential impacts of hazardous asteroids with the Earth can be and must be analyzed in more detail. Such an analysis is required to plan and implement the measures on preventing the asteroid impact hazard.