At the dawn of geodesy

The first land surveyors were rope stretchers and rope knotters, remembered in ancient documents and tomb paintings and also in some terminology. The L-shaped carpenter’s square, one of the earliest and most versatile basic tools, represents the observed direction of the plumb line versus the water level and appears as the shadow-casting gnomon and also as the geometrical gnomon in magically-restricted enlargements of altars. The related “Pythagorean” theorem was known in antiquity centuries before Pythagoras, with algebraic proofs in Babylonia and China. The spherical shape of the earth, deduced from the observation of circumpolar stars, was part of a complete equatorial astronomical system in ancient China. But although shadow measurements were generally used to establish north-south distances, only the Greeks derived from them the size of the earth. The striking difference between the abstract, geometric approach of Greece and the concrete, algebraic approach of Babylonia and China represents not a difference in talents but a difference in culture-bound interests.     

Active regions and the large scale flow in the solar photosphere

Summary Statistics on sunspot leaders and followers in active regions are derived from the 50 years of Greenwich records 1905–1954. The results are combined with the probable structure of large scale solar eddies as synthesized from various relevant pieces of information. It is found that active regions tend to be located in anticyclonic ridges of the large disturbances. The statistical leader and follower populations are further subdivided, each into new and old spot classifications. The new leaders, especially, show motions different from those of other spots, suggesting the presence of a life cycle for the large disturbances. It is found that the divergence and vorticity are positive and anticyclonic, respectively, for the new active regions, the former quantity being numerically larger than the latter in this case. Various possible implications of the material are discussed.     

Buchbesprechungen

Ohne Zusammenfassung     

Dynamics of the Indian monsoon and ENSO relationships in the SINTEX global coupled model

This paper uses recent gridded climatological data and a coupled general circulation model (GCM) simulation in order to assess the relationships between the interannual variability of the Indian summer monsoon (ISM) and the El Niño-Southern Oscillation (ENSO). The focus is on the dynamics of the ISM-ENSO relationships and the ability of the state-of-the-art coupled GCM to reproduce the complex lead-lag relationships between the ISM and the ENSO. The coupled GCM is successful in reproducing the ISM circulation and rainfall climatology in the Indian areas even though the entire ISM circulation is weaker relative to that observed. In both observations and in the simulation, the ISM rainfall anomalies are significantly associated with fluctuations of the Hadley circulation and the 200 hPa zonal wind anomalies over the Indian Ocean. A quasi-biennial time scale is found to structure the ISM dynamical and rainfall indices in both cases. Moreover, ISM indices have a similar interannual variability in the simulation and observations. The coupled model is less successful in simulating the annual cycle in the tropical Pacific. A major model bias is the eastward displacement of the western North Pacific inter-tropical convergence zone (ITCZ), near the dateline, during northern summer. This introduces a strong semiannual component in Pacific Walker circulation indices and central equatorial Pacific sea surface temperatures. Another weakness of the coupled model is a less-than-adequate simulation of the Southern Oscillation due to an erroneous eastward extension of the Southern Pacific convergence zone (SPCZ) year round. Despite these problems, the coupled model captures some aspects of the interannual variability in the tropical Pacific. ENSO events are phase-locked with the annual cycle as observed, but are of reduced amplitude relative to the observations. Wavelet analysis of the model Niño34 time series shows enhanced power in the 2–4 year band, as compared to the 2–8 year range for observations during the 1950–2000 period. The ISM circulation is weakened during ENSO years in both the simulation and the observations. However, the model fails to reproduce the lead-lag relationship between the ISM and Niño34 sea surface temperatures (SSTs). Furthermore, lag correlations show that the delayed response of the wind stress over the central Pacific to ISM variability is insignificant in the simulation. These features are mainly due to the unrealistic interannual variability simulated by the model in the western North Pacific. The amplitude and even the sign of the simulated surface and upper level wind anomalies in these areas are not consistent with observed patterns during weak/strong ISM years. The ISM and western North Pacific ITCZ fluctuate independently in the observations, while they are negatively and significantly correlated in the simulation. This isolates the Pacific Walker circulation from the ISM forcing. These systematic errors may also contribute to the reduced amplitude of ENSO variability in the coupled simulation. Most of the unrealistic features in simulating the Indo-Pacific interannual variability may be traced back to systematic errors in the base state of the coupled model.     

Modeling the impacts of climate change on China''s agriculture

1 Introduction Since recognition of the potential climate change [IPPC, 1990], efforts have been made to estimate the economic impacts of projected changes in climate on important sectors, such as agriculture, forestry and ecosystem, coastal zones and fisheries, water resource, and energy development. Although several sectors have been studied, none have received more attention than agriculture. Countrywide economic analysis has been completed for the United States[1-4], India[5] and Brazil…     

Elasticity of CaTiO3, SrTiO3 and BaTiO3 perovskites up to 3.0 Gpa: the effect of crystallographic structure

Elasticity of CaTiO₃, SrTiO₃ and BaTiO₃ perovskites has been experimentally investigated as a function of pressure up to 3.0 GPa in a liquid-medium piston cylinder apparatus using a high precision ultrasonic interferometric technique. Specimens used are hot-pressed fine-grained (3–10 μm) polycrystalline aggregates with low porosity (<1.5%). Compressional and shear wave velocities and their pressure derivatives have been measured. The results are compared with previous studies on other perovskites and the role of structural transitions is examined. We find that the role of Ti-O₆ polyhedral tilting (such as observed in CaTiO₃) is small in the sense that a single well-defined general trend exists in perovskites with a wide range of tilting angles, although there is suggestion that cubic perovskites have slightly higher bulk modulus than orthorhombic perovskites. In contrast, cation-anion displacement that changes crystal symmetry from cubic to tetragonal in BaTiO₃ has very large effects on elasticity. This distortion significantly reduces the bulk modulus (but not much the shear modulus) and results in an unusually large pressure derivative of bulk modulus (dK/dP～10). A large change in elasticity in BaTiO₃ associated with the structural transition (without a significant volume change) is a clear example of the breakdown of the Birch's law between densities and elastic wave velocities.     

Precipitation of electrons after geomagnetic substorms

Summary Precipitating electrons E_e>10 keV and E_e>30 keV and protons E_p=150 to 300 keV are analyzed using data obtained from the low-altitude polar-orbiting satellite Interkozmos-17 after the magnetic storm of December 2, 1977. On December 3, an isolated substrom occurred, and strong electron precipitation was observed in the midnigt sector, while the sequence of substorms of December 5 expanded its longitudinal extent from 22 MLT through the morning to 12 MLT. The different character of the precipitation, in the two cases mentioned, is discussed in relation to the changes of conditions for the generation of cyclotron instability as well as to the effect of particle injection. Proton precipitation occurred only in the night sector, most probably just inside the plasmapause.

---

¶rt; aau nau m E_e>10 u E_e>30 u nm E_p=150–300 n uu n uuma nmua n um m-17 n aum u 2. ¶rt;a 1977. 3. 12. nua uuaa u u nau m aumua m mo u. a n¶rt;amm 5. 12. nua auu ¶rt;m umaa, m m nau, a u m 22 MLT mu m ¶rt; 12 MLT. a aam nau nu¶rt; ¶rt; a ¶rt;am aa uu u ¶rt; uu um mumu u ¶rt;mu uuu amu. nau nm n¶rt;u m m u m a naana mu naa.

     

Prognose von Acidität,Eisen- und Sulfatkonzentration im Grundwasser von Bergbaugebieten

The hydrochemical fundamentals of the origination of high concentrations of iron and sulphate at an acid reaction of ground waters of exhausted open-cast coal mines are explained, and a technique based on representative sampling and oxidative treatment of aqueous suspensions with atmospheric oxygen for predicting the average load over years and decades on the basis of the analytical values has been developed and tested in the Central German area. Experimentally obtained relationships (weatherable pyrite/reaction rate, pH-variation/buffering capacity of soil, total iron content/pH-value) are stated.