Spatial and temporal variability of the Temperature and Humidity Index (THI) in dairy production zones of Uruguay

Abstract

The temperature and humidity index (THI) is the most widely index utilized for associating heat stress and milk production. The objective of this study was to assess meteorological information of Uruguay that allows its inclusion in further studies related to productive data. Analysis of climatic homogeneity (quality of meteorological data), minimum representative period of temperature and air humidity data (temporal representativeness) and area represented by a meteorological network (spatial representativeness) were performed. Air temperature and humidity data from thirteen meteorological stations (MS) for the summer months (December to March) were utilized. Two periods of analyses: 1983 to 2006 for monthly data, and 2001 to 2006 for daily data, were considered. Spatial variability was studied for three representative locations within three dairy production zones: San José, Florida and Paysandú. THI series resulted statistically homogeneous except for the MS of Melilla (not included). Determination coefficient (R₂ ) from simple linear regression models were developed to compare between locations and estimating THI temporal and spatial variability: THI_{Location Aij} = a + b x THI_{Location Bij}. Six consecutive years of THI information represented more than 75 % of the 24 years THI variability (R₂ Adj.>0,75). Representative areas of the three locations were determined by mapping R₂ Aj lines of 85% of THI variability. These results indicate that can be used THI calculated from available meteorological information to link with milk production data.