Spatial and temporal variability of daily weather variables in sub-humid and semi-arid areas of the united states high plains

Abstract

Ensuring continuous, quality data from weather station networks requires a knowledge of spatial and temporal variability. This knowledge is essential to identifying suspect data and providing estimates for bad data and for data gaps. This study was conducted to quantify and contrast the spatial and temporal variability for daily weather variables for two climatic areas, eastern (sub-humid) and western (semi-arid), in the High Plains of the US. For a period of 7 years (1989–1995) complete data were available from 38 automated weather stations, 19 stations in each area. The daily meteorological variables studied were: maximum and minimum air temperature, relative humidity, solar radiation, wind speed and precipitation and potential evapotranspiration (ETp). The coefficient of variation ( r 2) and standard error of estimate (SEE) were calculated by regression of daily measurements between like weather variables for various station pairings within the two climatic areas. A temporal analysis was conducted with a subset of the data and it was determined that 7 years of record are required to stabilize the variation between stations. In the spatial analysis, a central station was paired with each of the other stations in the area. The SEE and r 2 were plotted against separation distance from the central station. Best fit lines were determined for the variograms ( r 2) and errograms (SEE). Analyses were repeated for each month. Generally, the r 2 decreased while the SEE increased with distance of separation between sites. As separation distance between sites increased: SEE for maximum and minimum temperature were greater in the semi-arid than in the sub-humid area, especially during the winter season; while SEE for wind run were lesser in the semi-arid than in the sub-humid area. SEE for relative humidity were greater in the semi-arid than in the sub-humid area. There was no difference in SEE for solar radiation between the two areas. At short separation distances, there was minimal difference in SEE for ETp between the west and east; however at greater separation distances, SEE for ETp were greater in the semi-arid area. A significant seasonal cycle was found in the SEE data for maximum and minimum temperature, solar radiation, and ETp. Results indicate that the accuracy of estimated data and associated confidence limits will vary with the time of the year.