A substituição da floresta amazônica por pastagem e sua repercussão ao nível da termodinâmica da camada limite atmosférica: projeto RBLE.

Abstract

In this work, the possible implications of the substitution of the Amazonia Forest cover by pasture in Rondonia State were analysed with emphasis on the thermodynamics processes that command the Atmospheric Boundary Layer (ABL). A few important parameters in the development of the ABL were considered. The comparison was based on the results of two experimental campaigns, both in the dry season, of the RBLE project ("Rondonia Boundary Layer Experiment"): RBLE2 (July 1993) and RBLE3 (August 1994). During theses campaigns, vertical profiles of temperature, pressure, moisture and wind (a and V), using radiosonde, tethered balloon and surface monitoring equipments were taken. The two experimental sites are: Forest (LAT. 1Q°()5'S; LONG. 61°55'W; ALT. 120m) and Grassland (LAT. 10°45'S; LONG. 62°22'W; ALT. 220m), with a distance of 100km from each other. Existing automatic stations of the ABRACOS project ("Anglo-Brazilian Amazonian Climate Observation Study") provided important data for establishing the lower boundary conditions: surface radiation and energy balances. The results showed important difference/exchange between ABLs over the two types of vegetation covers. In the deforested area (grassland), at daytime, the ABL was 2.7K warmer and 3-Og.kg"1 drier, and its height was 1000m higher and turbulence stronger. At night-time, the temperature difference remained practically constant (2.2K) and the moisture difference was double compared to the daytime. On the other hand, the Forest ABL was 30% thicker and more unstable, at night-time.