Possible solar influence on atmospheric electric field

A physical hypothesis for the electrical coupling of the troposphere, ionosphere and magnetosphere has been proposed. It is shown that the vertical mass exchange takes place in the troposphere, ionosphere and magnetosphere by the gravity wave feedback mechanism through a chain of eddy systems. The vertical mass exchange gives rise to a vertical aerosol current which is responsible for the generation and mainte-nance of atmospheric electric field and also the variations in the H-component of the geomagnetic field. Any per-turbation in the troposphere would be transmitted to ionosphere and vice versa. A global perturbation in ionosphere, as the one caused by solar variability, is transmitted to troposphere influencing weather systems/geomagnetic/atmospheric electrification processes.The theory relating to the above physical mechanism is discussed. Also, results of analysis of at-mospheric electrical field data for Colaba, Bombay (8°53’ 56”N, 72° 48’ 54”E, 9.8 m ASL) and solar activity indices (Ap index, DST index and MSB crossing dates) for the 31 year period from 1936-1966 which provide statistical evidence for solar influence on atmospheric electrification processes are presented.     

Stratigraphic architecture of the Plio-Pleistocene infill of the Corinth Rift: Implications for its structural evolution

An integrated study of the stratigraphy, structure, sedimentology, and geomorphology of the Akrata–Derveni region (southern coast of the Gulf of Corinth, Greece) forms the basis for a tectono-stratigraphic model for the evolution of the Plio-Pleistocene central Corinth Rift.

The syn-rift sediments exposed on the uplifted southern coast of the Gulf of Corinth comprise three stratigraphic groups. Maximum total thickness of the syn-rift sediments can reach 2800 m in the middle of the studied area. The Lower Group is made of fluvio-lacustrine deposits. The Middle Group corresponds to thick alluvial fan conglomerates and their equivalent Gilbert-type fan deltas that built toward the north. The Upper Group is composed of uplifted terrace deposits, slope breccias and small Gilbert-type deltas. These groups have been subdivided into informal formations and depositional systems. Restoration of the stratigraphic architecture along a N–S transect provides a linked structural and depositional model for this part of the rift. Reconstruction of the latest phases of uplift is based on a study of geomorphological features.

Evolutionary phases include, (1) an overall increase in accommodation space during deposition of the Lower and Middle Groups followed by (2) a drastic decrease in accommodation space during deposition of the Upper Group. Sedimentary signals indicate that most of the major normal faults were active during deposition of the Lower Group. The depocentre was located in the middle part of the study area and paleocurrents were predominantly toward the ENE. The main depositional system shifted south at the onset of deposition of the Middle Group, recording a widening and deepening of the rift. This major event also corresponds to a change in paleocurrent direction to a clear northward polarity. The southernmost border fault, the Killini Fault, was sealed during deposition of the Middle Group. A northward migration of fault activity was associated with northward progradation of giant Gilbert-type fan deltas that record water depths up to 500 m. Finally, the fan delta system was abandoned as progressive tilting to the south and uplift of the margin induced a reversal of the drainage system with the development of an endorheic depression. Sediment supply to the basin thus decreased and a forced regression took place during deposition of the Upper Group recording a northward shift of more than 5 km and a 600 m relative sea-level drop. As no major eustatic sea-level falls of such amplitude are documented during the Pleistocene, the uplift is linked to regional tectonics. Uplift and fault reactivation gave the present day configuration of the southern coast of the Gulf.     

Radar rainfall estimation for flash flood forecasting in small urban watersheds

Radar rainfall estimation for flash flood forecasting in small, urban catchments is examined through analyses of radar, rain gage and discharge observations from the 14.3 km² Dead Run drainage basin in Baltimore County, Maryland. The flash flood forecasting problem pushes the envelope of rainfall estimation to time and space scales that are commensurate with the scales at which the fundamental governing laws of land surface processes are derived. Analyses of radar rainfall estimates are based on volume scan WSR-88D reflectivity observations for 36 storms during the period 2003–2005. Gage-radar analyses show large spatial variability of storm total rainfall over the 14.3 km² basin for flash flood producing storms. The ability to capture the detailed spatial variation of rainfall for flash flood producing storms by WSR-88D rainfall estimates varies markedly from event to event. As spatial scale decreases from the 14.3 km² scale of the Dead Run watershed to 1 km² (and the characteristic time scale of flash flood producing rainfall decreases from 1 h to 15 min) the predictability of flash flood response from WSR-88D rainfall estimates decreases sharply. Storm to storm variability of multiplicative bias in storm total rainfall estimates is a dominant element of the error structure of radar rainfall estimates, and it varies systematically over the warm season and with flood magnitude. Analyses of the 7 July 2004 and 28 June 2005 storms illustrate microphysical and dynamical controls on radar estimation error for extreme flash flood producing storms.     

Depositional wedge tops: interaction between low basal friction external orogenic wedges and flexural foreland basins

Growth structures develop mainly across depositional wedge tops where the top of the distal orogenic wedge lies below local base level within the flexural foreland basin. Documented examples indicate that optimum conditions for the development of a depositional wedge top occur when the dip of the upper surface of the outer orogenic wedge (α) is low (0–1°), regardless of the taper angle (α+β), where β is the inclination of the base of the wedge. Low α angles are associated with the presence of low friction décollements, usually salt. Therefore, depositional wedge tops develop most commonly on low basal friction wedges. In natural examples such as the northern Apennines, the South Central Pyrenees and the Zagros, it is shown that whereas α is consistently low, β can vary considerably (1–9°), being principally controlled by flexure of the lower plate. In addition, the distribution of deformation in the wedge is complex. The applicability of the critical wedge model to low basal friction external orogenic zones is examined. Neither taper angles, nor the complex distribution of internal deformation nor the often associated forward slip of the whole wedge, can be satisfactorily explained by the established critical wedge model. As weak detachments such as salt cannot support any significant topography, it follows that low basal friction wedges cannot attain a critical state and, therefore, the critical wedge model cannot be satisfactorily applied to these external orogenic systems. This model, however, explains well the behaviour of external orogenic wedges with high basal friction. In the analysis of orogenic wedges, separate analysis of the angles α and β proves more useful than the critical taper angle α+β.     

Sources of osmium to the modern oceans: new evidence from the Pt-Os system

High precision Os isotope analysis of young marine manganese nodules indicate that whereas the composition of modern seawater is radiogenic with respect to ¹⁸⁷Os/¹⁸⁸Os, it has ¹⁸⁶Os/¹⁸⁸Os that is within uncertainty of the chondritic value. Marine Mn nodule compositions thus indicate that the average continental source of Os to modern seawater had long-term high Re/Os compared to Pt/Os. Analyses of loess and freshwater Mn nodules support existing evidence that average upper continental crust (UCC) has resolvably suprachondritic ¹⁸⁶Os/¹⁸⁸Os, as well as radiogenic ¹⁸⁷Os/¹⁸⁸Os. Modeling the composition of seawater as a two-component mixture of oceanic/cosmic Os with chondritic Os compositions and continentally-derived Os demonstrates that, insofar as estimates for the composition of average UCC are accurate, congruently weathered average UCC cannot be the sole continental source of Os to seawater. Our analysis of four Cambrian black shales confirm that organic-rich sediments can have ¹⁸⁷Os/¹⁸⁸Os ratios that are much higher than average UCC, but ¹⁸⁶Os/¹⁸⁸Os compositions that are generally between those of chondrites and average-UCC. Preferential weathering of black shales can result in dissolved Os discharged to the ocean basins that has a much lower ¹⁸⁶Os/¹⁸⁸Os than does average upper crust. Modeling the available data demonstrates that augmentation of estimated average UCC compositions with less than 0.1% additional black shale and 1.4% additional ultramafic rock can produce a continental end-member Os isotopic composition that satisfies the requirements imposed by the marine Mn nodule data. The interplay of these two sources provides a mechanism by which the ¹⁸⁷Os/¹⁸⁸Os of seawater can change as sources and weathering conditions change, yet seawater ¹⁸⁶Os/¹⁸⁸Os varies only minimally.     

Paper 2. agricultural impacts of and responses to climate change in the Missouri-Iowa-Nebraska-Kansas (MINK) region

The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and Kansas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region under technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevail in 2030. The EPIC model of Williamset al. (1984), modified to allow consideration of the yield enhancing effects of CO₂ enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 representative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO₂ enrichment (from 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same percent under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actually increased. Farm level adjustments using low-cost currently available technologies, combined with CO₂ enrichment, eliminated about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustments, plus new technologies developed in response to the analog climate, when combined with CO₂ enrichment, converted the negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since this impact would be small after on-farm adjustments and CO₂ enrichment, animal production in MINK would be little affected by the analog climate.