Cooperative Institute for Research in Environmental Sciences

Investigating the Climate Impacts of Land Cover Change compared to El Nino Sea Surface Temperature Anomalies

In this project we are investigating the climate impacts of surface forcing from land cover change relative to El Nino sea surface temperature anomalies. This investigation is centered around a series of climate modeling experiments with the Community Climate System Model (CCSM). The model parameters and history files for the land cover change and sea surface temperature experiments are available online from our download site: http://brubeck.colorado.edu/sfce/login.php

The experiments were performed by Peter Lawrence at CIRES on the NCAR super computers Blueice and Blackforest. Climate simulations listed here were run with prescribed sea surface temperatures and sea ice distributions. Model simulations were performed using CCSM in configuration "F" at the 128x064 atmosphere and gx1v3 ocean resolutions for the simulation years 1970 - 1999.

1.) The land surface models used were:

CLM 3.0: This is the standard CLM 3.0 land surface model available for download from the NCAR Terrestrial Sciences Section at http://www.cgd.ucar.edu/tss/clm/distribution/clm3.0

CLM SiB: This is a newly developed version of the CLM land model that corrects problems with the evapo-transpiration partition and surface hydrology of the current release CLM 3.0. The new CLM SiB surface hydrology addresses these limitations by simulating global evapo-transpiration partition with increased transpiration (42%), reduced canopy evaporation (24%), and reduced soil evaporation (34%). The details of the new CLM SiB land surface model are found in the JHM paper: Lawrence, P.J., and T.N. Chase, Climate Impacts of making the hydrology of the Community Land Model (CLM 3.0) consistent with the Simple Biosphere Model (SiB), Journal of Hydrometeorology, Accepted with revisions, 2008

2.) The land surface data sets used were:

MODIS: MODIS derived current day land surface parameters as described in the JGR paper: Lawrence, P.J., and T.N. Chase, Representing a MODIS Consistent Land Surface in the Community Land Model (CLM 3.0), Journal of Geophysical Research, 112 (G1), G01023 10.1029/2006JG000168, 2007. This data set has all 15 Plant Functional Types (PFTs) defined for each grid cell unlike the MODISorig and CLM3orig data sets described below which have a maximum of 4 PFTs in each grid cell. This data set also has a new land surface mask making it consistent with the new CLM 3.5 version of this data.

potveg: Potential vegetation parameters that are consistent with the MODIS current day parameters above. The potential vegetation parameters are derived from remnant natural current day MODIS values spatially extrapolated to the potential vegetation distributions of Ramankutty and Foley (1999). The details of the parameter generation as well as the climate impacts of changes between the potential vegetation and current day are described in: Lawrence, P.J., and T.N. Chase, Investigating the Climate Impacts of Global Land Cover Change in the Community Climate System Model (CCSM), International Journal of Climatology, In Review, 2008

asiapv: This is an Asian subset of the global potential vegetation parameters. The Asian subset has potential vegetation represented over the region 65E to 155E and 10S to 40N with current day MODIS parameters in all other regions. The potential vegetation and current day MODIS parameters are the same as described above.

3.) The sea surface temperature data sets used were:

clim: Standard CCSM 3.0 monthly climatology sea surface temperatures and sea ice distributions taken from the period 1949 - 2001 and widely refered to as the Hurrell SST climatology. The original monthly data was compiled from Reynolds SST plus Hadley anomolies with the monthly climatology values calculated by Brian Kauffman (NCAR) for use with DOCN 5.0 and DICE 5.0. This data sets has been maintained and used as the sea surface temperature for DOCN 7.0 with the sea ice extent used prescriptively with CSIM 4.0 in these experiments.

elnino: Monthly climatology El Nino sea surface temperatures for use with DOCN 7.0. The El Nino sea surface temperatures were generated from the standard CCSM 3.0 climatology sst data set above with a mean monthly El Nino sst anomaly added to the climatology value. The average monthly El Nino anomalies were calculated from from the Hadley Center monthly SST data of Rayner et al. (1996) over the period 1870 - 2003. The sea surface temperature anomalies were calculated from all months that had seasonal Nino 1, 2 and 3 regions warmer than 1C over the climatology value for the period. The climatology sea ice distributions described above were used prescriptively with CSIM 4.0.