摘要:

It is 8 yr since important measurements of lightning in single‐cell thunderstorms were made during the Thunderstorm Research International Project (TRIP), yet no theoretical interpretation of the lightning generation mechanism from the data has been made. This tardiness in interpreting the data is undoubtedly related to the existing confusion in lightning generation theories.According toChalmers[1967], there are two classes of thunderstorm charge separation theories: those that rely on gravitation and those that do not involve gravitation. In the gravitational class, Chalmers again distinguished two types of processes: those in which ions are naturally generated (e.g., by cosmic rays, etc.) and are then attached to particles in the cloud and those in which some process (e.g., collision, coagulation, etc.) generates positive and negatively charged particles from neutrals in the cloud. Some of these two process types, cited in Chalmers' work, are given in Table 1, together with some of the scientists who originally proposed these processe

ISSN:0002-8606    

DOI:10.1029/EO067i020p00473

年代:1986

数据来源: WILEY

摘要:

The Executive Committee of the AGU Hydrology Section met in regular session at 4:00 P.M. on Monday, December 9, 1985, in Room 318 of the Civic Auditorium in San Francisco, Calif., during the AGU Fall Meeting. Twenty‐two members of the section were present, with section president R. Allan Freeze presidin

ISSN:0002-8606    

DOI:10.1029/EO067i020p00474-01

年代:1986

数据来源: WILEY

摘要:

Zero‐order basins are unchanneled topographic depressions that concentrate surface and subsurface flow and often fail, forming debris flows or other mass movement events. The term “zero‐order basins” is awkward, and many hydrologists find themselves using other terms (such as swales, hollows, subhollows, coves, bowls, amphitheaters, etc.) to describe these features. Whichever name you prefer, W. Megahan and R. Ziemer of the U.S. Department of Agriculture (USDA) Forest Service (Megahan at Boise, Idaho, and Ziemer at Arcata, Calif.) organized an excellent session for the AGU Erosion and Sedimentation Committee. Current interest in this topic was made evident by the number of people attending the session, which was held on December 11, 1985, in San Francisco, Calif., as part of the AGU Fall Meeting. The session began with a number of talks about the hydrologic characteristics of specifi

ISSN:0002-8606    

DOI:10.1029/EO067i020p00475-01

年代:1986

数据来源: WILEY

摘要:

The AGU Erosion and Sedimentation Committee sponsored a daylong session on sediment transport in channels with mixtures of sediment sizes on December 13, 1985, at the AGU Fall Meeting in San Francisco, Calif. The morning session contained an interesting set of related theoretical and empirical research on particle motion. Ned Andrews (U.S. Geological Survey (USGS), Denver, Colo.) began the session by presenting empirical evidence for critical shear stresses required to move bed particles in simple natural channels. He presented work that he has been working on for the past several years (along with Gary Parker of St. Anthony Falls Hydraulic Laboratory, Minneapolis, Minn., and other colleagues) that suggests that coarse and fine bed particles have essentially equal mobility because of the hiding of fine particles by larger particles. Pat Wiberg and Jim Smith (both of University of Washington, Seattle) presented a theoretical analysis of the movement of different‐sized particles that supported the work presented by Andrew

ISSN:0002-8606    

DOI:10.1029/EO067i020p00476-01

年代:1986

数据来源: WILEY

摘要:

A session on land subsidence caused by withdrawal of groundwater was held December 10, 1985, in San Francisco, Calif., at the AGU Fall Meeting. The symposium was organized by William E. Strange (National Geodetic Survey, Rockville, Md.) and Thomas L. Holzer (U.S. Geological Survey (USGS), Menlo Park, Calif.) and was cosponsored by the AGU Geodesy and Hydrology sections. Nine papers were presented on topics that ranged from evaluations of the suitability of the new satellite‐based Global Positioning System (GPS) to theoretical analyses of land subsidence.T. N. Narasimhan (Lawrence Berkeley Laboratories, Berkeley, Calif.) introduced the general subject of subsidence with a review of relevant physical processes. Compaction, although conceptually simple, involves several complexities, including plastic deformation and translation of deep‐seated deformation through the overburden. Sashi Mathur (Tarleton State University, Stephenville, Tex.), in a paper coauthored with M. Yavuz Corapcioglu (City College of New York, New York), analyzed deformation in the unsaturated zone above a falling water table. Their theoretical formulation was able to reproduce results from laboratory studies of sand colu

ISSN:0002-8606    

DOI:10.1029/EO067i020p00477

年代:1986

数据来源: WILEY

摘要:

During its 30th historically recorded and fourth predicted apparition, Comet Halley (the most famous of comets) was visited by five spacecraft from three space agencies, carrying a total complement of 44 scientific instruments.Since Comet Halley has a retrograde motion around the sun in an orbit that is inclined at 162° to the ecliptic plane, all the encounters were fast flybys around the time that the comet crossed the ecliptic plane on March 10, 1986 (descending node)

ISSN:0002-8606    

DOI:10.1029/EO067i020p00478

年代:1986

数据来源: WILEY

摘要:

The Office of Management and Budget (OMB) has proposed a major change in the way administrative overhead costs are charged to federal research grants. In the February 12Federal Register, OMB proposed that charges for the administrative portion of overhead costs be limited to 26% of the direct cost of the research, dropping to a 20% limit next year. The revisions would be made in a document called OMB Circular A‐21, which specifies the way in which universities must account for federal research grant money. The proposed change is seen by many university administrators as adding insult to the injury to research funding that they say is caused by Gramm‐Rudman‐Hollings, the new law that calls for the federal budget deficit to shrink to zero by 1991 (Eos, January 28, 1986, p

ISSN:0002-8606    

DOI:10.1029/EO067i020p00481-01

年代:1986

数据来源: WILEY

摘要:

Streamflows decreased sharply in much of the United States east of the Mississippi River during April, with 19 streams in the region at record‐low flows, according to the U.S. Geological Survey (USGS). A USGS monthly check on water resources conditions nationwide also showed that the West and Midwest had above‐average streamflows and that the level of the Great Salt Lake in Utah continued to rise closer to the lake's historic high mark, set more than a century

ISSN:0002-8606    

DOI:10.1029/EO067i020p00482

年代:1986

数据来源: WILEY