Transcript Hydrology in Land Surface Models

Hydrology in
Land Surface Models
Jessie Cherry
International Arctic Research Center
& Institute of Northern Engineering
Many LSMs classify vegetation by biomes
Community Land Model
• LSM for CCSM, CLM at version 3.5 (4.0 has been under
development for 5+ yrs)
• The model formalizes and quantifies concepts of ecological
climatology
• Model components consist of: biogeophysics, hydrologic cycle,
biogeochemistry and dynamic vegetation
• 5 primary sub-grid land cover types (glacier, lake, wetland, urban,
vegetated)
• The vegetated portion of a grid cell is further divided into patches
of plant functional types, each with its own leaf and stem area
index and canopy height
• Each subgrid land cover type and PFT patch is a separate column for
energy and water calculations
• T42 = 2.5 deg x 2.5 deg
CLM Model Methodology
• The model is designed to run in three different
configurations:
• 1. Stand-alone executable code as part of the
Community Climate System Model (CCSM).
• 2. A subroutine call within the Community
Atmosphere Model (CAM) in which CAM/CLM
represent single executable code.
• 3. Stand-alone executable code in which the
model is forced with atmospheric datasets. In this
mode, the model runs on a spatial grid that can
range from one point to global.
Coupling Strategies
Biogeophysics
Hydrology and River Routing
• Includes interception of water by plant foliage
and wood, throughfall and stemflow,
infiltration, runoff, soil water, and snow
• Directly linked to the biogeophysics and also
affect temperature, precipitation, and runoff
• Total runoff (surface and sub-surface drainage)
are routed downstream to oceans using a river
routing model only for the largest river
systems
River Routing
Major Systems
LSM Water Balance
Separate River Transport Model
• A river transport model (RTM) (Branstetter et al.,
in prep) is synchronously coupled to the
Community Land Model (CLM) for hydrological
applications as well as for improved land-oceansea ice-atmosphere coupling in the Community
Climate System Model (CCSM)
• This model was implemented on a 1/2 degree
grid. Code internal to the land model interpolates
the total runoff from the column hydrology (e.g.,
T42, T31 grid) to the river routing 1/2 degree grid
Dynamic Vegetation
Model Component: Dynamic Vegetation
• Ecosystem Carbon Balance: the carbon cycle but also
changes in community composition and vegetation
structure in response to disturbance (e.g., fire, land
use) and climate change
• There are two time-scales for this dynamics: Succession
considers changes in community composition and
vegetation structure over periods up to several
hundred years, typically following disturbance such as
fire or land use. Over longer-periods of times (e.g.,
centuries, millennia) the biogeography of vegetation
changes in response to climate change.
Succession/Change in Biogeography