Characterizing the synoptic expression of the Angola low

The Angola low is a key feature of the southern Africa wet season atmosphere that influences precipitation across the continent. This paper uses ERA-Interim to show that the synoptic expression of the Angola low is a combination of dry heat lows and moist tropical low pressure systems. The Angola heat low and Angola tropical low composites are contrasted against similar lows observed in other continental tropical regions and found to be broadly comparable. The implications that the distinction between dry and moist events has for the interannual relationship among the Angola low, precipitation, and ENSO are examined. The tropical lows exhibit unusual semistationary behavior by lingering in the Angola region rather than traveling offshore. This behavior is proposed to be caused by an integrated sea breeze–anabatic wind that enhances (inhibits) cyclonic vorticity stretching and convection inland (near the coast). The combined effect of the heat lows and the anchored tropical lows creates the Angola low in the climatological average. By elucidating the mechanisms of the Angola low, this research improves the foundation of process-based evaluation of southern Africa present and future climate in CMIP and AMIP models

Learning to automatically detect features for mobile robots using second-order Hidden Markov Models

In this paper, we propose a new method based on Hidden Markov Models to interpret temporal sequences of sensor data from mobile robots to automatically detect features. Hidden Markov Models have been used for a long time in pattern recognition, especially in speech recognition. Their main advantages over other methods (such as neural networks) are their ability to model noisy temporal signals of variable length. We show in this paper that this approach is well suited for interpretation of temporal sequences of mobile-robot sensor data. We present two distinct experiments and results: the first one in an indoor environment where a mobile robot learns to detect features like open doors or T-intersections, the second one in an outdoor environment where a different mobile robot has to identify situations like climbing a hill or crossing a rock.Comment: 200

Practices Used by Dairy Farmers to Reduce Seasonal Production Variability

The objective of this analysis was to identify the production practices used by farmers to change seasonal production. Production practices included milk production per cow, proportion of cows milking, number of first lactation animals entering the herd, number of cows leaving the herd, number of days to first breeding, and calves born. Farms that participated in a seasonal pricing plan during 1993, 1994, and 1995 decreased production practice seasonality in response to price premiums, which caused a decrease in production seasonality compared to nonparticipating farms. Participating farms showed a preference for adjusting entering first lactation animals and number of calves born, but did make adjustments in other practices as well.Livestock Production/Industries,

THE PRODUCTION THEORY APPROACH TO IMPORT DEMAND ANALYSIS: A COMPARISON OF THE ROTTERDAM MODEL AND THE DIFFERENTIAL PRODUCTION APPROACH

Results indicate that, when comparing the unconditional derived-demand elasticities to the unconditional consumer demand elasticities, significant differences emerge due to the differences in the first-stage estimation procedure between the differential production approach and the Rotterdam model. In comparing the consumer demand price/corss-price elasticities to the derived-demand price/cross-price elasticities, it is clear that use of the Rotterdam model when a production approach should be used can lead to overestimation, underestimation, and incorrect signs in deriving unconditional price effects.dairy, demand, imports, international, production, Rotterdam, trade, Demand and Price Analysis, D12, D24, F10, F14, Q17,

THE PRODUCTION THEORY APPROACH TO IMPORT DEMAND ANALYSIS: A COMPARISON OF THE ROTTERDAM MODEL AND THE DIFFERENTIAL PRODUCTION APPROACH

The primary objective of this paper is to present the differential approach to the theory of the firm and to present the methodology of how it can be applied to import demand analysis. Furthermore, this paper compares and contrasts the use of the differential production approach with the Rotterdam model.Demand and Price Analysis,

THE DERIVED DEMAND FOR IMPORTED CHEESE INTO JAPAN BY COUNTRY

This paper was presented at the INTERNATIONAL TRADE IN LIVESTOCK PRODUCTS SYMPOSIUM in Auckland, New Zealand, January 18-19, 2001. The Symposium was sponsored by: the International Agricultural Trade Research Consortium, the Venture Trust, Massey University, New Zealand, and the Centre for Applied Economics and Policy Studies, Massey University. Dietary changes, especially in developing countries, are driving a massive increase in demand for livestock products. The objective of this symposium was to examine the consequences of this phenomenon, which some have even called a "revolution." How are dietary patterns changing, and can increased demands for livestock products be satisfied from domestic resources? If so, at what cost? What will be the flow-on impacts, for example, in terms of increased demands for feedgrains and the pressures for change within marketing systems? A supply-side response has been the continued development of large-scale, urban-based industrial livestock production systems that in many cases give rise to environmental concerns. If additional imports seem required, where will they originate and what about food security in the importing regions? How might market access conditions be re-negotiated to make increased imports achievable? Other important issues discussed involved food safety, animal health and welfare and the adoption of biotechnology, and their interactions with the negotiation of reforms to domestic and trade policies. Individual papers from this conference are available on AgEcon Search. If you would like to see the complete agenda and set of papers from this conference, please visit the IATRC Symposium web page at: http://www1.umn.edu/iatrc.intro.htmDemand and Price Analysis, International Relations/Trade,

THE DERIVED DEMAND FOR IMPORTED CHEESE INTO JAPAN: A TWO-STAGE DIFFERENTIAL PRODUCTION APPROACH

The goal of this paper is to provide the U.S. dairy industry with elasticities of Japan's derived demand for imported cheese differentiated by source country of production. These estimates are then used to assess the relative competitiveness of cheese imported from the U.S. to cheese imported from other source countries.Demand and Price Analysis, Research and Development/Tech Change/Emerging Technologies,

THE DERIVED DEMAND FOR IMPORTED CHEESE IN HONG KONG DIFFERENTIATED BY SOURCE COUNTRY OF PRODUCTION

The major goal of this paper is to provide the U.S. dairy industry with empirical estimates of the sensitivity (elasticities) of Hong Kong's derived demand for imported cheese differentiated by source country of production with respect to price changes and total import changes.Demand and Price Analysis,

Drylines in Southern Africa: Rediscovering the Congo Air Boundary

Projected rainfall decline in southern Africa is likely to be highly sensitive to subtleties in the local atmospheric circulation. In an effort to understand the regional circulation complexities, a novel algorithm is developed to identify the Congo air boundary (CAB) in ERA-5, a high-resolution reanalysis dataset. The CAB, a forgotten feature of the circulation, is defined in the austral spring and early summer, using surface humidity gradients and near-surface wind convergence lines, and it is found to be an indicator of the location of the southern edge of the African rain belt. A related convergence-line and dryline feature, described in this paper as the Kalahari discontinuity (KD), is also identified. It is established that either a dryline CAB or KD is present in southern Africa for over 95% of days between August and December, with arc lengths typically exceeding 10°. The seasonal and diurnal cycles of the CAB and the KD are presented, and their prevalence in station observational data is confirmed. The interannual variability of the CAB latitude and detection frequency is found to explain at least 55% of interannual spring rainfall variability in southern Africa between 15° to 25°S. Links are established with the Angola and Kalahari heat lows and tropical temperate trough events