Search results for "Planetary Science"
showing 10 items of 4367 documents
Infrasonic Early Warning System for Explosive Eruptions
2018
Machine‐Learning Based Reconstructions of Past Regional Sea Level Variability From Proxy Data
2021
Anomalous Behavior of Zirconium and Hafnium in Volcanic Fumarolic Fluids
2022
The Zirconium and Hafnium concentrations in worldwide fumaroles fed by magmatic fluids reveal that the Zr/Hf ratio is inversely related to the temperature of emission. Lower Zr/Hf ratio values below the chondritic signature are found in fluids having the highest temperature while super-chondritic Zr/Hf ratio values are found in lower temperatures. Sub-chondritic values of the Zr/Hf ratio may be related to larger volatility of Hf-chloride gas species with respect to Zr-Cl gas species, while super-chondritic ratios may correspond to fluid-rock processes resulting from cooling of uprising magmatic fluids. We propose that subchondritic Zr/Hf ratio values in fumaroles associated with high temper…
Late Holocene Asian summer monsoon variability reflected byδ18O in tree-rings from Tibetan junipers
2011
[1] Recent warming in High Asia might have a strong impact on Asian summer monsoon variability with consequences for the hydrological cycle. Based on correlations between climate data, the tree-ring δ18O of high-elevation junipers is an indicator of August precipitation. Thus, our 800-year long annually resolved oxygen isotope series reflects long-term variations in summer monsoon activity on the southern Tibetan plateau. Summer precipitation was reduced during 13th–15th centuries and since the 19th century, whereas the Little Ice Age period (15th–19th century) was rather moist. The late 20th century was among the driest periods during the past 800 years, showing a tendency to slightly wett…
Chemical abundances determined from meteor spectra: I. Ratios of the main chemical elements
2003
Relative chemical abundances of 13 meteoroids were determined by averaging the composition of the radiating gas along the fireball path that originated during their penetration into the Earth's atmosphere. Mg, Fe, Ni, Cr, Mn, and Co abundances, relative to Si, are similar to those reported for CI and CM carbonaceous chondrites and interplanetary dust particles. In contrast, relative abundances of Ca and Ti in meteor spectra indicate that these elements suffer incomplete evaporation processes. The chemical composition of all meteoroids studied in this work differs from that of 1P/Halley dust.
Sharpness of the extratropical tropopause in baroclinic life cycle experiments
2007
[1] The sharpness of the extratropical tropopause is investigated using baroclinic life cycle experiments. In these simulations, slow synoptic scale dynamics leads to a net tropopause sharpening. The mechanism involves vertical convergence of the ageostrophic wind. The results support earlier suggestions from idealized theoretical studies.
Whole-Ocean Changes in Silica and Ge/Si Ratios During the Last Deglacial Deduced From Long-Lived Giant Glass Sponges
2017
A major Holocene ENSO anomaly during the Medieval period
2004
[1] Here, we present a high resolution marine El Nino flood record from Peru. A period of extreme drought without strong flooding occurred from A.D. 800–1250. Anomalous precipitation patterns characterized the entire Indo-Pacific ENSO domain, with dry events in the northern Arabian Sea and the mid-latitudes of both Americas, coinciding with wet periods in the Atlantic Cariaco Basin. The occurrence of contemporaneous moisture anomalies in other archives in the ENSO region highlights the role of El Nino strength in global climate evolution during the late Medieval period when temperature reconstructions show a rather heterogeneous pattern.
Structure function as a tool in AE and Dst time series analysis
1995
A new method to analyse the structure function (SF) has been constructed and used in the analysis of the AE time series for the years 1978-85 and Dst time series for 1957-84. It is shown that this SF analysis makes a clear distinction between affine and periodicity dominated time series, and it displays the essential periodicities of the series in a range relevant to its characteristic time scale. The AE time series is found to be affine such that the scaling exponent changes at a time scale of 113 (±9) minutes. On the other hand, in the SF function analysis, the Dst data are dominated by the 24-hour and 27-day periods. The 27-day period is modulated by the annual variation.