Evapoclimatonomy III: The Reconciliation of Monthly Runoff and Evaporation in the Climatic Balance of Evaporable Water on Land Areas

Abstract

The present study is the third in a sequel by Lettau and Baradas. The Evapoclimatonomy I model has been discussed and applied by various authors including Hare, Hay, Kutzbach, Pinker, and Corio. In the present study the semiempirical method of ?watershed calibrations? proposed in Evapocilmatonomy II is replaced by a less subjective diagnostic scheme. Water storage on land areas is defined in terms of ?evaporable water.? The climatic mean annual course of balanced monthly evaporation is reconciled with that of monthly runoff, where both are defined as functions of evaporable water. Model application is exemplified by three case studies, one each for a continental, a maritime, and a tropical climate. Two types of modifications are investigated., 1) the monthly balance of evaporable water in response to a simulated summer drought, for a continental or summer-rain climate in comparison with the less severe long-term reactions in a maritime or winter-rain climate; 2) the monthly balance of evaporable water and runoff reduction as caused by rainforest depiction in tropical Panama. Evapoclimatonomy III is compared with two other methods for climatic water budget evaluation: 1) the Thornthwaite-Mather method using data for Wilmington, Delaware; and 2) the Penman method in a ?monthly reconciliation of meteorological and hydrological variables? for Barro Colorado, Panama, by Dietrich et al.