Balanço de energia e evapotranspiração em áreas de pastagem e floresta densa na Amazônia Central.

Abstract

Radiation balance components in forest and pasture areas during dry and wet seasons are analized in the present study. Energy balance patterns in the pasture during both the seasons are investigated. Penman's combination method is used to evaluate potencial évapotranspiration at both the sites. Measured actual évapotranspiration values are compared with those obtained by the Bowen ratio and Penman-Monteith and Thorthwaite-Holzman equations. The data used in the study was obtained from the field experiments of the ANGLO-BRAZILIAN AMAZONIAN CLIMATE OBSERVATION (ABRAÇOS) project. The experiments were conducted at Reserva Ducke forest(2°19'S ;59°57'W) and Fazenda Dimona pastura(2°19'S ; 60° 59'W) during the years 1990 and 1991. Mean values of energy balance components in the pasture during dry and wet seasons showed small differences, while net radiation values differed significantly. During the dry season a slight reduction in global radiation during the period 11:00-13:00 hours was observed in the pasture as compared between to that of the forest. Actual évapotranspiration values derived by PenmanMonteith and Bowen ratio methods agreed well with measured values. The results for the pasture showed good correlation between évapotranspiration and net radiation values.