Temporal variability in spatial correlation of daily rainfall

Composite correlation fields based on a 5‐year record of daily rainfall at 67 stations throughout Tunisia were used to investigate spatial and temporal properties of rainfall fields. The composite correlation fields had in general banded or elliptical patterns and with the elongations generally along the coastline or the topographical ridges. The banded patterns occurred usually during the rainy season, and the elliptical patterns occurred toward the summer or early autumn. The ratio of width to length of the elongated correlation fields varied in general between 0.1 and 0.4. The composite correlation fields defined as the area within the 0.7 correlation isoline were usually less than about 8.000 km2. The mean monthly rainfall was moderately correlated with the size of the composite correlation fields. The major orientation of the coastline seems to be a more important factor for the rainfall generation than are local irregularities in the coastal orientation and local topographical differences.