Persistence of anomalous moisture conditions in the interior plains of North America

Mean growing season (April‐September) climatic conditions in the Interior Plains of North America, as measured by the Bhalme and Mooley drought index, were subjected to the length of runs (Gold), chi‐squared and autocorrelation tests of dependence. Only a maximum of about 3 per cent of the total variation in the seasonal drought in any year is explained by the previous year. Based on the results from the three tests, it can be concluded that the mean seasonal moisture conditions during the growing season in the region can be considered to be an independent time process. In other words, the series of the seasonal drought index, statistically speaking, cannot be distinguished in its sequential pattern of occurrence from a random series.