Improving the altimetric rain record from Jason-1 & Jason-2

Dual-frequency rain-flagging has long been a standard part of altimetric data analysis, both for quality control of the data and for the study of rain itself, because altimeters can provide a finer spatial sampling of rain than can passive microwave instruments. However, there have been many varied implementations, using different records of the surface backscatter and different thresholds. This paper compares four different measures available for the recently-launched Jason-2. The evaluation compares these measures against clearly desired properties, finding that in most cases the adjusted backscatter and that from the ice retracker perform much better than that recommended in the users' handbook. The adjusted backscatter measure also provides a much better link to observations from Jason-1, opening up a much longer period for consistent rain investigations, and enabling greatly improved analysis of the short-scale variability of precipitation. Initial analysis shows that although the spatial and temporal gradients of backscatter increase at very low winds, the spatial gradients in rain attenuation are concentrated where rainfall is greatest, whilst the temporal changes have a simple broad latitudinal pattern

Learning from Strike

This paper reports on an experimental study of the influence of asymmetric information and information spillovers on bargaining outcomes. It develops and tests Kuhn and Gu (1999) s model of learning in sequential wage negotiations, by means of two Ultimatum Bargaining Games with uncertainty on the proposer s side. Evidence shows that Dunlop s assertion of inflationary wage claims does not hold systematically and strike incidence is lowered by information spillovers, since claims are revised according to the previous bargaining outcomes. However, in the presence of fairness concerns, the ability to observe outcomes but not the bargaining process does not entail a reduction in information asymmetry sufficient to guarantee Pareto improving bargaining outcomes. Ce papier présente une étude expérimentale sur l'influence des asymétries d'information et de la diffusion de l'information entre firmes sur l'issue des négociations. Nous proposons un prolongement ainsi qu'un test du modèle de Kuhn et Gu (1999) concernant l'apprentissage dans des négociations séquentielles. Nous utilisons pour cela deux jeux d'ultimatum avec incertitude du coté du proposant. Les résultats expérimentaux montrent que l'hypothèse de Dunlop d'un biais inflationniste systématique des revendications salariales n'est jamais vérifiée et que conformément aux prédictions de Kuhn et Gu, la probabilité d'apparition d'une grève diminue en présence de diffusion de l'information. En effet, une révision des demandes en fonction du résultat des négociations passées est observée dans les données expérimentales. Pourtant, observer seulement le résultat des négociations passées et non le processus de négociation ne suffit à garantir une augmentation Pareto optimale des gains des joueurs. Les préoccupations d'équité entravent les effets bénéfiques de la diffusion de l'information entre firmes.Asymmetric Information, Experiments, Learning, Strikes, Ultimatum Bargaining Games, Asymétrie d'information, Expérimantations, Apprentissage, Grève, Jeux d'ultimatum

Learning from Strikes

This paper reports on an experimental study of the influence of asymmetric information and information spillovers on bargaining outcomes. It develops and tests Kuhn and Gu's model (1999) of learning in sequential wage negotiations, by means of two Ultimatum Bargaining Games with uncertainty on the proposer's side. Evidence shows that Dunlop's assertion of inflationary wage demands does not systematically hold and strike incidence is lowered by information spillovers, since demands are revised according to previous bargaining outcomes. However, in the presence of fairness concerns, the ability to observe outcomes but not the bargaining process does not entail a sufficient reduction in information asymmetry to a point of guaranteeing Pareto-improved bargaining outcomes.asymmetric information; experimental economics; learning; strikes; ultimatum bargaining games

CONVERSION OF A LAMB PRODUCTION SYSTEM TO ORGANIC FARMING: HOW TO MANAGE, FOR WHICH RESULTS?

Two sheep flocks were managed organically (for two years from conversion onwards) under different lambing strategies (1 lambing/year vs. 3 lambings every two years). The second system was tested as there was a producer’s interest in high productivity that is a guarantee of good economic results in conventional. Reproduction, feeding, lamb production, carcass quality, health (particularly internal parasitism), economic return of the flock, grass production, and pasture biodiversity were evaluated. The lambs were bred under low therapeutic input. The economical advantage of increasing lambing frequency was not demonstrated, whereas this strategy complexified management and resulted in higher internal parasitic infection of the lambs, and finally showed a lower stability. There were difficulties in establishing a very high feed self-sufficiency in both systems, especially the more intensive system (4 points lower), due to harsh climatic conditions; following this five-year experiment, we are changing our strategy to provide nitrogen in the systems

CONVERSION OF A LAMB PRODUCTION SYSTEM TO ORGANIC FARMING: HOW TO MANAGE, FOR WHAT RESULTS?

Two sheep flocks were managed organically for two years from conversion under different lambing strategies (1 lambing/year vs. 3 lambings every two years). The second system was tested because pf a producer’s interest in high productivity, which is a guarantee of good economic results in conventional production.. Reproduction, feeding, lamb production, carcass quality, health (particularly internal parasitism), economic return of the flock, grass production, and pasture biodiversity were evaluated. The lambs were bred with low therapeutic inputs. No economic advantage of increasing lambing frequency was demonstrated, whereas this strategy complicated management and resulted in higher internal parasitic infection of the lambs, and finally showed lower stability. There were difficulties in establishing a very high feed self-sufficiency in both systems, especially the more intensive system (4 points lower), due to harsh climatic conditions. Following this five-year experiment, we are changing our strategy to provide nitrogen in the systems

Sea state and rain: a second take on dual-frequency altimetry

TOPEX and Jason were the first two dual-frequency altimeters in space, with both operating at Ku- and C-band. Each thus gives two measurements of the normalized backscatter, sigma0, (from which wind speed is calculated) and two estimates of wave height. Departures from a well-defined relationship between the Ku- and C-band sigma0 values give an indication of rain.This paper investigates differences between the two instruments using data from Jason's verification phase. Jason's Ku-band estimates of wave height are ~1.8% less than TOPEX's, whereas its sigma0 values are higher. When these effects have been removed the root mean square (r.m.s.) mismatch between TOPEX and Jason's Ku-band observations is close to that for TOPEX's observations at its two frequencies, and the changes in sigma0 with varying wave height conditions are the same for the two altimeters. Rain flagging and quantitative estimates of rain rate are both based on the atmospheric attenuation derived from the sigma0 measurements at the two frequencies. The attenuation estimates of TOPEX and Jason agree very well, and a threshold of -0.5 dB is effective at removing the majority of spurious data records from the Jason GDRs. In the high sigma0 regime, anomalous data can be cause by processes other than rain. Consequently, for these low wind conditions, neither can reliable rain detection be based on altimetry alone, nor can a generic rain flag be expected to remove all suspect data

Performances techniques et économiques de 2 troupeaux ovins expérimentaux conduits en Agriculture Biologique (AB).

Deux troupeaux ovins allaitants en AB ont été comparés en ferme expérimentale, menés selon 2 conduites de la reproduction : 3 agnelages en 2 ans (système accéléré) ou une mise bas par an (système herbager). Leurs performances techniques et économiques ont été analysées et comparées à celles d’élevages privés. En système accéléré, la productivité numérique est légèrement supérieure (6 % : 161 vs 152 en moyenne sur 3 ans) mais, même lorsque l’écart est élevé (en 2002 : 193 vs 152), la marge par brebis est peu supérieure (90€ vs 86) du fait de coûts de production élevés. En effet, les concentrés utilisés atteignent 178 kg/brebis (+58 %) avec un prix 60 % plus élevé qu’en conventionnel. Par ailleurs, les résultats de ce système sont irréguliers. Le système herbager, moins intensif pour l’animal, est l’illustration d’un compromis entre niveau des performances zootechniques élevé et maîtrise des charges d’alimentation avec maximisation de l’utilisation des ressources fourragères

Controlling reproduction in organic sheep breeding: the influence of breeding factors on the effectiveness of the ram effect

The ram effect, which is a natural method for the control of reproduction in sheep, is an alternative to hormone treatments that are banned on organic farms. The ram effect induces a combination of ovulation and oestrus in ewes that is acyclic and conducive to artificial insemination. The proportion of acyclic females with induced ovulation and their subsequent fertility at the first oestrus is variable. The control of some breeding factors that have been studied here may help to reduce this variability. The proportion of ewes induced to ovulate by rams increased as the season advanced (54% in April vs. 84% at the end of May, p<0.05) and with a longer time period between drying-off and mating: from 29% to 84% (p<0.001) for 22 and 86 days elapsed, respectively. The fertility of these ewes at the first oestrus was also higher at the end of May than in April (86% vs. 39%, p<0.01) and increased with the amount of time elapsed since drying-off (55% and 81% for 22 and 86 days, respectively; p=0.09). The time that the first oestrus occurs is later for lean ewes because they have a higher proportion of short cycles (67%) than fat ewes (41%, p<0.05)