On the Development of Coveriates for the Evaluation of Operational Seeding Projects in Areas without Physiographic Influences


  • Gary L. Achtemeier Illinois State Water Survey


Ani mportanta specto of the Operationa Seeding Evaluation Techniques (OSET) project is to investigate the usefulness of environmental cova~iates for reducing the large natural convective rainfall variability in the evaluation. Covariates derived from surface metee~ological observations have been compared with precipitation within a 1000 km area of the fine scale METROMEX precipitation network operated in the St. Louis area in 1971-1975. The area around St. Louis is typical of most of the grain producing areas of the eastern half of the United States and of many parts of the world with similar climate. There are no unique physiographical/mechanical (forced upslope flow) or physiographical/dynamical (mountain induced ciruclations, sea and lake breezes) forcing that cause convective precipitation locally. Further, precipitation falls within diverse weather systems. Not unexpectedly, the correlations were low~ usually less than 0.3. However, a combination of from 6 to I0 variables can explain anywhere from 40% to 50% of the rainfall variance when covariates calculated at sites outside theraingage network are included, in the regression.




Scientific Papers