Evaluating seasonal risk and the potential for windspeed reductions to reduce chill index at six locations using GrassGro

2012 ◽  
Vol 52 (10) ◽  
pp. 921 ◽  
Author(s):  
J. C. Broster ◽  
S. M. Robertson ◽  
R. L. Dehaan ◽  
B. J. King ◽  
M. A. Friend

The death of newborn lambs is a major factor influencing the reproductive efficiency of sheep enterprises. Adverse weather conditions (wind, precipitation and low temperature), either alone or in combination (chill index), can increase the level of newborn lamb mortality to over 50% of births for short periods through increased heat loss. The provision of shelter to reduce wind speed and therefore chill index (heat loss) has been shown to reduce lamb mortality; however, the reduction in mortality has been variable. This study used the decision support tool GrassGro to determine the likelihood of adverse weather conditions occurring at six locations across south-eastern Australia which varied widely in climate. Data were extracted for 24 consecutive weekly periods between May and October over 39 years (1968–2006) to evaluate daily precipitation, temperature, radiation, wind speed and chill index. The minimum, maximum and median values were calculated for all climatic factors for every week and year combination. The effectiveness of reducing wind speed to reduce the occurrence of a high chill index was also evaluated. The severity of these weather events varied between locations with the median weekly chill index rarely exceeding 1000 kJ/m2.h at Temora, but at both Hamilton and Orange this occurred in over two-thirds of the weeks examined. Reducing wind speed by 50% reduced the number of weeks with a median chill index exceeding 1000 kJ/m2.h in twice as many weeks at Hamilton and Yass compared with Orange. These results show that the potential for shelter to reduce chill index will vary according to the location and time of year. In locations where another climatic factor, such as low temperature or rainfall, has a greater influence on the chill index, shelter which only reduces wind speed, will be less effective than at locations where wind speed is the driver of chill index.

Rangifer ◽  
1996 ◽  
Vol 16 (4) ◽  
pp. 45 ◽  
Author(s):  
Kenneth R. Whitten

Researchers have described general patterns of population regulation that fit most caribou (Rangifer tarandus) herds. Nevertheless, specific factors operating on particular populations vary greatly, and efforts to categorize herds according to the general patterns often lead to confusion. It is difficult for biologists to attempt to describe population dynamics in terms of density relationships for wide-ranging arctic caribou such as the Porcupine Herd. In these herds density varies as a function of dispersal and erratic movement patterns and is not simply the number of caribou divided by a fixed range area. Density is also a poor surrogate for resource availability per individual caribou because climatic factors affect forage and/or access to forage independendy of caribou numbers. Thus classic signs of nutritional stress such as delayed puberty, reduced productivity, and winter starvation can occur when a population is small as well as large and do not necessarily denote food competition brought on by high density, per se. Nutritional stress and exacerbated predation due to adverse weather conditions occasionally cause the Porcupine Herd to decline, and limiting factors such as poor nutrition, predation, harvest, accidents, and disease act in combination to keep herd growth rates low during periods of good weather. Adverse weather setbacks occur frequently, and the herd remains within a fairly restricted range of densities over long time periods. There is no true density dependent regulation and no equilibrium in this system.


1972 ◽  
Vol 104 (1) ◽  
pp. 81-88 ◽  
Author(s):  
H. V. Danks ◽  
J. R. Byers

AbstractTerrestrial arthropods collected from Bathurst Island in 1969 are listed: 78 species (4 spiders, 13 mites, and 61 insects, 30 of which are chironomids) have now been collected in this area of the high arctic. Notes on the overwintering of some of the commoner insect species are given. Although the collecting season was a poor one in 1969 because of adverse weather conditions, the list probably represents half or more of the island’s arthropod fauna. The nature of the list indicates that this fauna is impoverished compared to some other areas of the Queen Elizabeth Islands. This impoverishment may be largely explained by climatic factors.


2021 ◽  
Vol 93 (1) ◽  
pp. 103-122
Author(s):  
Katarzyna Lindner-Cendrowska

This study was designed to explore the impact of meteorological factors (air temperature, relative and absolute humidity, wind, cloudiness and precipitation) on influenza morbidity in four selected big cities in Poland – Cracow, Poznań, Warsaw and Wrocław. Atmospheric data obtained from four meteorological stations spread over six years (2013‑2018) were compared to influenza-like illnesses (ILI) reports, obtained from the Voivodship Units of the State Sanitary Inspection for the same locations and period. Data were analysed using Spearman correlation and negative binomial regressions to capture the nonlinear relationship between exposure to environmental conditions and influenza morbidity. Our study found a strong negative association of absolute air humidity with influenza infections (RR = 0.738) and positive relationship with minimal temperature (RR = 1.148). The effect of wind speed, cloudiness and precipitation on ILI was less evident. Proposed model is valid for all age groups in Polish cities, but suits the best to elderly citizens (65+). The model is also appropriate for different seasons, however only absolute humidity, minimal temperature and wind speed are considered significant variables all year round. Furthermore, we observed 6 to 9-days delay between particular adverse weather conditions and ILI morbidity increase, as 1-week lag model proved to have the highest predictive power (AIC = 8644.97). Although meteorological variables have statistically significant contribution to explain influenza morbidity, there are also other non-climatic factors, that can possibly influence the seasonality and complexity of influenza epidemiology in Polish cities.


2021 ◽  
Vol 2 (1) ◽  
pp. 46-62
Author(s):  
Santiago Iglesias-Baniela ◽  
Juan Vinagre-Ríos ◽  
José M. Pérez-Canosa

It is a well-known fact that the 1989 Exxon Valdez disaster caused the escort towing of laden tankers in many coastal areas of the world to become compulsory. In order to implement a new type of escort towing, specially designed to be employed in very adverse weather conditions, considerable changes in the hull form of escort tugs had to be made to improve their stability and performance. Since traditional winch and ropes technologies were only effective in calm waters, tugs had to be fitted with new devices. These improvements allowed the remodeled tugs to counterbalance the strong forces generated by the maneuvers in open waters. The aim of this paper is to perform a comprehensive literature review of the new high-performance automatic dynamic winches. Furthermore, a thorough analysis of the best available technologies regarding towline, essential to properly exploit the new winches, will be carried out. Through this review, the way in which the escort towing industry has faced this technological challenge is shown.


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