Hydrometeorological effects of historical land-conversion in an ecosystem-atmosphere model of Northern South America

Hydrology and Earth System Sciences

M.Longo¹  A. L. S.Swann¹  P. R.Moorcroft¹  R. L.Bras¹  R. G.Knox¹  N. M.Levine¹  K.Zhang¹ 

DOI  :  10.5194/hess-19-241-2015

学科分类：地球科学(综合)

来源: Copernicus Publications

【 摘 要 】

This work investigates how the integrated land use of northern South Americahas affected the present day regional patterns of hydrology. A model of theterrestrial ecosystems (ecosystem demography model 2: ED2) is combined withan atmospheric model (Brazilian Regional Atmospheric Modeling System:BRAMS). Two realizations of the structure and composition of terrestrialvegetation are used as the sole differences in boundary conditions that drivetwo simulations. One realization captures the present day vegetationcondition that includes deforestation and land conversion, the other is anestimate of the potential structure and composition of the region'svegetation without human influence. Model output is assessed for differencesin resulting hydrometeorology.

The simulations suggest that the history of land conversion in northern SouthAmerica is not associated with a significant precipitation bias in thenorthern part of the continent, but has shown evidence of a negative bias inmean regional evapotranspiration and a positive bias in mean regional runoff.Also, negative anomalies in evaporation rates showed pattern similaritywith areas where deforestation has occurred. In the central eastern Amazonthere was an area where deforestation and abandonment had lead to an overallreduction of above-ground biomass, but this was accompanied by a shift inforest composition towards early successional functional types andgrid-average-patterned increases in annual transpiration.

Anomalies in annual precipitation showed mixed evidence of consistentpatterning. Two focus areas were identified where more consistentprecipitation anomalies formed, one in the Brazilian state of Pará wherea dipole pattern formed, and one in the Bolivian Gran Chaco, where a negativeanomaly was identified. These locations were scrutinized to understand thebasis of their anomalous hydrometeorologic response. In both cases,deforestation led to increased total surface albedo, driving decreases innet radiation, boundary layer moist static energy and ultimately decreasedconvective precipitation. In the case of the Gran Chaco, decreasedprecipitation was also a result of decreased advective moisture transport,indicating that differences in local hydrometeorology may manifest viateleconnections with the greater region.

【 授权许可】

Unknown