Large-Scale Atmosphere-Biosphere Experiment in Amazônia (LBA)
The goal of our NASA-LBA funded work is to investigate how the terrestrial ecosystem and water resources of the Amazon basin are impacted by changing environmental conditions and human activity.
To achieve this goal, we have been developing new comprehensive regional models and datasets to describe the behavior of terrestrial ecosystems and hydrological resources of the Amazon River Basin.
Our dataset development has included a thorough physical representation of the river characteristics (the LBA Macrohydrological Dataset), and a high resolution land use dataset (the LBA Land Cover Dataset). Additionally, we also used our models IBIS and THMB (HYDRA) to simulate the variability of the carbon and water balances of the Amazon basin for the last 60 years.
LBA - THMB (HYDRA) Dataset
The files are generated by THMB (HYDRA), a model that simulates the time-varying flow and storage of water in terrestrial hydrological systems, including rivers, wetlands, lakes, and human-made reservoirs.
THMB (HYDRA) is described in Coe, M.T. (2000). Modeling terrestrial hydrologic systems at the continental scale: Testing the accuracy of an atmospheric GCM. Journal of Climate 13, 686-704 and Coe, M.T., M.H. Costa, A. Botta, and C. Birkett. Long-term simulations of discharge and floods in the Amazon basin (2002). Journal of Geophysical Research 10.1029/2001JD000740, 23 August 2002.
THMB (HYDRA) operates at a 5-minute latitude by longitude grid (~9 km at the equator) with a 1-hour time step and requires as boundary conditions: topography (from digital elevation models), evaporation from water surfaces (estimated from climate data, using a simple Penman energy balance model), surface runoff (supplied by IBIS), base flow (drainage from the soil column, supplied by IBIS), and precipitation (from climate data).
The dataset was created by linked simulations using the IBIS ecosystem model (Kucharik, C.J., J.A. Foley, C. Delire, V.A. Fisher, M.T. Coe, S.T. Gower, J. Lenters, C. Molling, J.M. Norman and N. Ramankutty, 2000. Testing the performance of a dynamic global ecosystem model: Water balance, carbon balance, and vegetation structure. Global Biogeochemical Cycles 14, 795-825) and the HYDRA water transport model.
IBIS was first run on a 0.5 deg by 0.5 deg latitude/longitude grid, extending over the entire Amazon River basin (21S-6N; 45W-80W). for the period 1935-1998 to generate runoff estimates. Then the IBIS results extending from 1939 to 1998 were used in the HYDRA simulations along with the climate data (precipitation and estimated lake surface evaporation) to generate hourly output from HYDRA. This output was then averaged to monthly mean values.
THMB (HYDRA) Output includes 3 tarred/gzipped data files: sflux.v2.nc, height.v2.nc, warea.v2.nc. These files are gridded files at 5-minute latitude by longitude grid (~9 km at the equator) resolution for the entire Amazon/Tocantins River basins (21S-6N; 45W-80W). They represent the mean monthly, simulated river discharge (sflux), water height (height) and inundated area (warea) for the period 1939-1998.
These data files are generated by numerical models. Therefore, their accuracy is dependent on the assumptions applied in these.
The files of this dataset are generated by our terrestrial ecosystem model, IBIS.
This simulation used the CRU05 climate data as input for IBIS for the period January 1921-December 1998 [New et al., J. of Climate 13, 2000]. Because CRU climate records are not reliable prior to 1930, we would advise only using results from years 1935-1995 (allowing for a 5-year characteristic time-scale of the deep soil).
This IBIS dataset includes 25 tarred/gzipped data files. These are gridded files at 0.5 deg latitude by 0.5 deg longitude resolution for the entire Amazon/Tocantins River basin (21S-5.5N; 45.5W-80W). They represent mean yearly and monthly energy, water, and carbon fluxes, and yearly carbon stocks for the period 1921-1998.
The analysis of this dataset results is shown in Botta, A., N. Ramankutty and J.A. Foley (2002). Long-term variations of climate and carbon fluxes over the Amazon Basin. Geophysical Research Letters 29(9), 10,1029/2001 GL013607, 2002.
These data files are generated by numerical models, therefore their accuracy is dependent on the assumptions applied in these.
LBA - Land Cover Dataset
These files are gridded at 5-minute latitude by longitude (~9km at the equator) resolution for the entire Amazon/Tocantins river drainage basins (21S - 6N; 45W - 80W). The files contain the estimated proportions of total agriculture ("totag"), cultivated area ("cul"), natural pasture ("pasnat"), and planted pasture ("paspla") in each grid cell in either the mid-1980s or mid-1990s. Data is provided in the netcdf format (".nc" files) and the ARC/INFO ASCII format (".txt" files). Proportions are expressed as parts per 10,000 so that, for example, a value of "8945" means that 89.45% of the given pixel is estimated by this procedure to be used for agricultural activity.
The data were generated from a fusion of agricultural census data and satellite classifications, and are described in Cardille, J.A., J.A. Foley, and M.H. Costa (2002). Characterizing patterns of agricultural land use in Amazonia by merging satellite classifications and census data. Global Biogeochemical Cycles 16(3), 10.1029/2000GB001386, 20. The fusion technique merges agricultural census data from countries of the basin (including Brazil) with land cover data from the University of Maryland Global Land Cover Facility 1-km classification. This technique was used to derive the mid-1990s total agriculture surface for the region, which was then apportioned according to agriculture census data proportions into cultivated area, natural pasture, and planted pasture.
The mid-1980s maps were created by scaling the mid-1990s snapshots backward in time using the relative increase or decrease in agriculture, as derived from mid-1980s census data and United Nations Food and Agriculture Organization (FAO) data.
These data files are generated by a fusion of two data sources which may contain errors in position and value. In particular, census variables may be susceptible to under- and over-estimation for political and economic reasons. While we do not treat these errors of estimation directly, it appears that the fusion technique smooths extreme/unlikely values in the census data.
LBA - Macrohydrological Dataset
Continental scale hydrologic routing models, also known as macrohydrological routing models, have evolved considerably in the past few years. As the models have become more sophisticated, they have represented a variety of new processes, and expanded their data requirements - either as input data or as validation for the model output. This is a new data set of large-scale hydrological river flow routing parameters for the Amazon and Tocantins basins. Part of this data set was required by the development of the continental scale hydrological routing model HYDRA and its application to the Amazon basin. HYDRA represents phenomena like floods, backwater effects and the seasonal hydrograph much more realistically than the previous generation of macrohydrological routing models. The data set contains data on: (1) river network, at 5 minute (~9 km) resolution; (2) time series of monthly means of river discharge, for 122 fluviometric stations spread throughout the basin; (3) sinuosity of each of the main rivers, measured at 111 river sections in the basin; and (4) depth to the water table and transmissivity of the aquifer, derived from measurements taken at 81 points throughout the basin.
Details of this dataset are included in the readme file, which is part of the download.
For further information about this dataset contact Marcos Costa.