Welcome to LaDWorld!

Introduction

LaDWorld is a series of retrospective simulations of global continental water and energy balances, created by forcing the Land Dynamics (LaD) model (Milly and Shmakin, 2002, abstract, paper) with estimated historical atmospheric conditions. Simulated variables include snow water equivalent, soil water, shallow ground water, soil temperature, evapotranspiration, runoff and streamflow, radiation, and sensible and latent heat fluxes.

The LaD model continues to undergo development. We anticipate improved representations of various processes in the future. As these come online, it is our objective to employ them in the creation of increasingly realistic versions of LaDWorld. Different versions of the model and different estimates of historical atmospheric conditions produce different LadWorlds. Each LaDWorld is named after a river, following an alphabetic order.

One motivation behind the creation of LaDWorld was a series of collaborations with non-hydrologists whose studies of earth-system dynamics both require and yield information on global hydrologic processes. We welcome further such interactions, which seem beneficial for all involved.

LaDWorld-Amazon (Released April 2003)

LaDWorld-Amazon, which is based on the LM2p5 configuration of the LaD model, is similar to a simulation described in detail by Shmakin et al. (2002, abstract, paper). Differences from that earlier simulation are

	extension of the integration period (which starts in January 1979) through June 2002,
	inclusion of interannual variation of atmospheric temperature in the forcing, and
	correction of errors made in prescribing the precipitation inputs in the published simulation.

LaDWorld-Amazon resolves processes on a 1-x-1-degree horizontal grid, with an hourly time step; output is available on a monthly time step.

LaDWorld-Brahmaputra (Released January 2004)

LaDWorld-Brahmaputra differs from LaDWorld-Amazon only in the temporal extent of the simulation, which has been extended forward in time through June 2003. This extension supported analyses of ongoing satellite-based gravity observations from the Gravity Recovery and Climate Experiment (GRACE) and allowed GRACE to benefit from LaD data.

LaDWorld-Congo (Released August 2004)

LaDWorld-Congo, which is based on the LM2p7 configuration of the LaD model, differs from earlier LaDWorlds in several respects:

It extends forward in time through September 2003.

Instead of using "natural" global land cover (vegetation), it uses estimated 1990 land cover.

It contains several crude enhancements of model physics relative to earlier LadWorlds, including the following:

	Soil depth is increased to 6 m, and the freeze-thaw thermal inertia equivalent to 300 kg m^-3 of water is included in the soil. (Earlier versions did not consider soil-water phase change and neglected sensible heat storage below 1.5 m of soil.)
	Snow-free albedo of desert lands is obtained from NASA's Surface Radiation Budget data set, instead of being assigned a globally constant value.
	Groundwater residence times are increased for some northern basins.
	The globally constant critical root density was reduced so as to increase effective rooting depths slightly.

LaDWorld-Congo resolves processes on a 1-x-1-degree horizontal grid, with a half-hourly time step; output is available on a monthly time step.

LaDWorld-Danube (Released September 2004)

LaDWorld-Danube differs from Congo only in the temporal extent of the simulation and in some minor technical details. Specifically, the simulation runs through April 2004, and is was run under GFDL's FMS Runtime Environment. The only practical consquence of the latter is that the file names are slightly different, with date ranges now indicated in the name of the file.

LaDWorld-Euphrates (Released November 2005)

LaDWorld-Euphrates differs from Danube in the temporal extent of the simulation, which runs through May 2005.

LaDWorld-Fraser (Released March 2007)

LaDWorld-Fraser differs from Euphrates in the temporal extent of the simulation, which runs through November 2006. Additionally, the initial condition is one that is better equilibrated with climatic forcing. The improved initial condition removed a minor spinup issue that had affected earlier LaDWorlds. In these imperfectly spun-up experiments, the deep soil temperatures in permafrost regions were still experiencing a cool-down in earlier years of the experiments.

Access to LaDWorld

Access is not automated yet, but easy access can be arranged by contacting us.

Citation

It is recommended that users of LaDWorld data sets cite Milly and Shmakin (2002, abstract, paper) for the model and Shmakin et al. (2002, abstract, paper) for the simulation procedure. It is further recommended that the USGS LaDWorld-Amazon, LaDWorld-Brahmaputra, or LaDWorld-Congo data set be mentioned in the text or the acknowledgments.

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Last modified 2007-04-04
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