Differential Rotation of Stable Recurrent Sunspot Groups

Stable recurrent sunspot groups from the Greenwich data set which were identified in at least two subsequent solar rotations were traced. The solar rotation was determined by the period method from the time difference of the two central meridian passages of each of the 327 identified groups. Sidereal rotation periods were calculated from the synodic ones by a seasonal-dependent procedure taking into account the details of the Earth's motion around the Sun. Growing recurrent sunspot groups rotate on the average faster than decaying recurrent sunspot groups, while sunspot groups of all types taken together rotate faster than both growing and decaying recurrent sunspot groups. A north–south rotational asymmetry and a cycle-dependence of rotational velocity of recurrent sunspot groups were analyzed. Positive rotation velocity deviations are larger, but less numerous than the negative ones. Signatures of torsional oscillations were not found analyzing the rotation velocity residual of recurrent sunspot groups as a function of the distance from the average latitude of activity.     

Dimension of the Earth's General Ellipsoid

The problem of specifying the Earth's mean (general)ellipsoid is discussed. This problem has been greatly simplified in the era of satellite altimetry, especially thanks to the adopted geoidal geopotential value, W₀ = (62 636 856.0 ± 0.5) m² s^-2.Consequently, the semimajor axis a of the Earth's mean ellipsoid can be easily derived. However, an a priori condition must be posed first. Two such a priori conditions have been examined, namely an ellipsoid with the corresponding geopotential that fits best W₀ in the least squares sense and an ellipsoid that has the global geopotential average equal to W₀. It has been demonstrated that both a priori conditions yield ellipsoids of the same dimension, with a–values that are practically identical to the value corresponding to the Pizzetti theory of the level ellipsoid: a = (6 378 136.68 ± 0.06) m.     

The paleolimnological analysis of sediments from high mountain lake Nižné Terianske pleso in the High Tatras (Slovakia)

Sedimentological climate proxies and a 200-year long climate record, reconstructed using a data-set of European-wide meteorological data, have been compared at the high mountain lake Niné Terianske pleso in the High Tatras, Slovakia. Diatoms, chrysophyte stomatocysts, chironomids, plant pigments and spheroidal carbonaceous particles (SCPs) were analysed as well as sediment lithostratigraphic parameters. Using a radiometric approach the sediment core was dated and a depth of 4.6 cm was found to correspond to 1852 AD. The sediment accumulation rate (0.0034 g·cm^–2·yr^–1) was one of the lowest identified in the European mountain lake project, MOLAR. Despite this slow accumulation rate a remarkably coherent lithological and stratigraphic record has been recovered. The sediments of this remote mountain site, largely free from the effects of direct human impact, have been found to display a wealth of variability over the last 200 years.The record of spheroidal carbonaceous particles, indicators of anthropogenic pollution deposition, begins around 4.5–5.0 cm in depth (1833–1857). Temporal patterns are typical of European lake sites with the concentration peaking in the late 1970's. The SCP/²¹⁰Pb inventory ratio for the site is also in good agreement with the European latitudinal pattern. A strong influence of sample age on the chrysophyte assemblage composition in the upper-most 4–6 cm indicates that the main changes in the cysts have been related to long term environmental changes, probably pH. Analysis of chironomid remains revealed a stable profundal community. Chironomids as a whole showed no correlations to temperature fluctuations in the last 200 years. Relatively abundant remains of Diamesa sp. head capsules and other taxa closely associated with stream conditions in the older layers contrast with the absence of Diamesa sp. in the recent sediments. This change is considered to be evidence for the existence of a stronger, more stable inlet supplied from permanent granular snow fields in the lake basin. The most important changes in diatom assemblages were observed at 3cm. Many species of the genus Achnanthes spp. together with Navicula schmassmannii and Orthoseira roeseana made up the greatest part of the diatom community above 3 cm, being absent or rare lower in the record. A positive correlation between diatoms and mean summer temperature was found.     

Lake Jezero v Ledvici (NW Solvenia) – changes in sediment records over the last two centuries

Lake Jezero v Ledvici (NW Slovenia) is a 14 m deep mountain lake at an elevation of 1860 m, situated on limestone bedrock. It is an oligotrophic, alkaline and hard-water lake with a transparency of about 14 m and has suffered several times over recent centuries from strong earthquakes. In 1996 five sediment cores, between 35 and 45 cm long, were collected from the deepest part of the lake and analysed to reconstruct environmental changes over the last few centuries. The data indicate changes induced by pollution and climate change during the last two centuries similar to those in other European mountain and remote lakes. However, at this site earthquakes have also affected the lake and partly obscure the interpretation of the sediment record. From 1780 to 1890, sediment records show low abundance of diatoms and relatively high abundance of Cladocera. After 1890, the number of diatoms started to increase coinciding with a strong earthquake. From the beginning of the 20th century, concentrations of spheroidal carbonaceous particles (SCP), diatom valves and head capsules of chironomids gradually increased whilst in Cladocera the main difference observed was a change in the proportion of benthic taxa. After 1960, in parallel with a rise in air temperature, a further increase in accumulation rate of diatoms started, but there was a decrease in Cladocera.     

Peak Horizontal-to-Vertical Acceleration Ratio and Local Amplification of Strong Ground Motion

Residuals of the peak horizontal acceleration for site-independent attenuation relations are shown to have weak positive correlation with the average observed peak horizontal/vertical acceleration ratio (q) at the recording site. This ratio systematically increases as the hardness of the soil decreases. Taking the average observed q at the recording station into account reduces the scatter of data slightly in fitting the assumed peak acceleration attenuation law. If the soil classification of the data is available, soil dependence is found to be weaker if the data are corrected for the effect of q prior to regression. This correction reduced the mean value of q = 1.85 for the Dinarides area to q = 1.52, which, on the average, is characteristic of rock sites.     

Trends in extreme summer temperatures at Belgrade

Summary Trends in extreme temperatures have been investigated for the Belgrade temperature record (1975–2003) to assess how an increase in the mean summer temperatures is related to changes in the extreme maximum and minimum temperatures. The rising mean summer temperatures at Belgrade are associated with a substantial increase in the occurrence of extreme maximum temperatures. Two statistical models for climate change (changing mean with constant standard deviation, and changing mean and standard deviation) indicated that the changing mean was dominant, because the observed trend in standard deviation was small.