Numerical investigation of the Earth's rotation during a complete precession cycle

A theory for the long-term rotational motion of the quasi-rigid Earth was constructed by numerical integration. The theory spans 72,000 years centered about 1968 A.D., and provides accurate rotational and positional data for the Earth in the recent past and the near future. The physical model is termed dynamically consistent because developments for the active forces and torques are truncated based solely on their magnitudes regardless of their origin. The model includes all appropriate forces and torques due to the geopotential and tidal effects as well as lunisolar and planetary contributions. The elastic and inelastic deformations due to tidal action were too small to affect the mass properties of the Earth at the truncation level of the model. However, long-term dissipative effects of the tidal forces and torques were not negligible. These considerations gave the model its quasi-rigid characterization. The numerical output provided both rotational and orbital-element data. The data were fitted throughout the 72,000-year range using Chebyshev polynomial series

A Ground-Based Search for Thermal Emission from the Exoplanet TrES-1

Eclipsing planetary systems give us an important window on extrasolar planet atmospheres. By measuring the depth of the secondary eclipse, when the planet moves behind the star, we can estimate the strength of the thermal emission from the day side of the planet. Attaining a ground-based detection of one of these eclipses has proven to be a significant challenge, as time-dependent variations in instrument throughput and atmospheric seeing and absorption overwhelm the small signal of the eclipse at infrared wavelengths. We gathered a series of simultaneous L grism spectra of the transiting planet system TrES-1 and a nearby comparison star of comparable brightness, allowing us to correct for these effects in principle. Combining the data from two eclipses, we demonstrate a detection sensitivity of 0.15% in the eclipse depth relative to the stellar flux. This approaches the sensitivity required to detect the planetary emission, which theoretical models predict should lie between 0.05-0.1% of the stellar flux in our 2.9-4.3 micron bandpass. We explore the factors that ultimately limit the precision of this technique, and discuss potential avenues for future improvements.Comment: 10 pages, 1 table, four figures, accepted for publication in PAS

The Impact of the National Counter-Cyclical Income Support Program for Dairy Producers on Representative Dairy Farms

This report contains the results of an analysis of the National Counter-Cyclical Income Support Program for Dairy Producers on the Agricultural and Food Policy Center’s (AFPC) representative dairy farms. The impact of the proposal on the representative farms is evaluated in terms of the change in average annual cash receipts and the change in the average annual net cash farm income. The role and potential importance of payment limits on these farms are discussed. All milk prices by state and program benefits under the payment limit binding and nonbinding scenarios were developed by FAPRI and were applied to the representative dairies. For more information on those results see the FAPRI analysis of this program.Agribusiness, Agricultural and Food Policy, Livestock Production/Industries,

A Brief Summary of U.S. Farm Program Provisions

This brief publication began as a need for a short summary of farm programs and farm bills for two agricultural economics courses focusing on agricultural policy -- ag. economics 429, and ag. economics 614. It became clear that many students taking these courses had less and less background in agriculture and less (even cursory) knowledge of policies than those of the recent past. After this list was developed a number of other professional agricultural economists found copies and began to use it, hence its publication in a more structured form. The list of Farm Program Provisions is not all-inclusive. It certainly does not contain all the laws and provisions that have affected agriculture over the years. However, it is an easy reference to farm bills and provisions since 1933. We intend to update this list as time goes on to continue its usefulness to professionals and students alike.Agricultural and Food Policy,

The Impacts of Wildlife Conservation Policies on Rural Household Welfare in Zambia

KEY POLICY POINTS • Tourism is increasingly important in Zambia as a vehicle for economic growth, and has been identified as a key sector for poverty reduction due to its potential to generate off-farm income and employment in rural areas. Growth in arrivals and receipts in Zambia has outpaced average growth rates for developing countries. • Tourism in Zambia relies mostly on the stock of natural resources, including the protected area system which includes national parks and game management areas (GMAs). Co-management agreements between Zambia Wildlife Authority (ZAWA) and rural communities present opportunities and threats for households living in GMAs. • Households living in GMAs have lower average income than households in other rural areas. Yet we find that, for prime GMAs (those well stocked with wildlife), the GMA designation leads to higher incomes than households would otherwise be expected to achieve, based on their own characteristics and those of the areas in which they reside. • We further find that the benefits of living in a prime GMA accrue mostly to the wealthier segments of the population. • Though overall effects on households are positive, losses from crop damage by wildlife are a threat to this success: we find that such losses are statistically significant, large enough to be meaningful to households, and greatest in prime GMAswildlife conservation, rural households, zambia, Community/Rural/Urban Development, Environmental Economics and Policy, Food Security and Poverty, International Development, q57,

The Impact of Land Fragmentation on Beef Cattle Inventory

Many groups have discussed with alarm the impact of agricultural land conversion to non-agricultural uses. This research indicates little evidence that beef cow inventory has been negatively affected by land fragmentation. Average acres per transaction, total transactions, or a fragmentation index did not have an important effect on cattle inventory.Land Economics/Use, Livestock Production/Industries,

Financial Impacts of Regional Differences in Dairies

The sensitivity of net cash farm income to changes in selected production variables, output prices, and input costs varies significantly across representative U.S. dairies. Different regions of the country were impacted differently by changes to production and prices.Agricultural Finance, Q12, Q14,

The evolution and demise of North Brazil Current rings

Author Posting. © American Meteorological Society, 2006. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 36 (2006): 1241-1264, doi:10.1175/JPO2907.1.Subsurface float and surface drifter observations illustrate the structure, evolution, and eventual demise of 10 North Brazil Current (NBC) rings as they approached and collided with the Lesser Antilles in the western tropical Atlantic Ocean. Upon encountering the shoaling topography east of the Lesser Antilles, most of the rings were deflected abruptly northward and several were observed to completely engulf the island of Barbados. The near-surface and subthermocline layers of two rings were observed to cleave or separate upon encountering shoaling bathymetry between Tobago and Barbados, with the resulting portions each retaining an independent and coherent ringlike vortical circulation. Surface drifters and shallow (250 m) subsurface floats that looped within NBC rings were more likely to enter the Caribbean through the passages of the Lesser Antilles than were deeper (500 or 900 m) floats, indicating that the regional bathymetry preferentially inhibits transport of intermediate-depth ring components. No evidence was found for the wholesale passage of rings through the island chain.Funding was provided by National Science Foundation Grants OCE 97-29765 and OCE 01-36477

Regional and Structural Impacts of Alternative Dairy Policy Options

Milk and dairy product prices have fallen to their lowest levels in 3 years following the record highs of 2004 and 2005. The large government stockpiles of non-fat dry milk are gone, but threaten to build again as non-fat dry milk and cheese prices decline nearer the support price level. A new farm bill is scheduled to be written in 2007. The Milk Income Loss Contract (MILC) program included in the last farm bill was only authorized through September 2005. Subsequent legislation reinstated the MILC program through August 2007. WTO negotiations are on-going and could influence U.S. farm programs 1/. Dairy’s role in the U.S. amber box limit of $19.1 billion may necessitate some possible trade-offs with other commodities. Dairy counts about$4.2 billion toward the annual amber box limit, but actual spending only averages about $1 billion (Outlaw, et al). The pressure of low prices, WTO negotiations, MILC continuation, and a new farm bill has created the potential for a number of options and alternatives for dairy policy. This paper examines the regional and structural impacts of 3 dairy policy options: MILC continuation, a target price/deficiency payment program, and an increase in the support price. All three options are designed to spend$400 million in amber box payments per year. The analysis uses representative dairy farms in major milk producing regions of the country developed by the AFPC for policy analysis.Agribusiness, Agricultural and Food Policy, Livestock Production/Industries,

Analysis of H.R. 2646 on Land Tenure Arrangements on U.S. Representative and Texas FARM Assistance Farms

This report analyzes whether H.R. 2646 may provide economic incentives for landlords to end current land tenure arrangements with tenants and take over management (and government payments) associated with their land. This work is a followup to Briefing Paper 01-9, Representative Farm Analysis of the H.R. 2646 Farm Bill Proposal that analyzes the impacts of H.R. 2646 on the representative crop farms maintained by the Agricultural and Food Policy Center (AFPC).Agribusiness, Agricultural and Food Policy, Land Economics/Use,