EMC/NCEP has completed a set of more than 4000 retrospective integrations of the new Climate Forecast System (CFS), which became operational in August 2004. The CFS is a fully coupled atmosphere-ocean-land modeling system. The ocean model is the GFDL MOM3, with 1/3rd degree resolution near the equator, and the atmospheric model is the NCEP GFS at T62L64 resolution. The land model is composed of a 2-layer soil model and canopy treatment as described by Pan and Mahrt (1987), with coupling to the planetary boundary layer scheme described by Hong and Pan (1996). The 4000+ retrospective runs were produced from 15-member ensembles corresponding to initial conditions from all 12 months within the 23-year period 1981-2003. All integrations were for 9-months. The initial ocean states were obtained from the NCEP/GODAS, and Reanalysis-2 data were used to provide initial conditions for the atmosphere and land states. The enormous retrospective data set is ideal for diagnostic and empirical studies. Here we pursue issues regarding the feedback of the land surface in models, compared to the feedback as determined from a global “observed” soil moisture data set (Fan and van den Dool 2004). In a study presented in a companion paper (van den Dool and Saha 2005), we utilized data from 4000+ retrospective integrations of the NCEP Climate Forecast System (CFS) to identify locations over all continents that are “sensitive” for soil moisture feedbacks. When idealized moisture anomalies (a ‘patch’, or approximate Green’s function) are present at those locations, they are more likely than anomalies placed at other locations to result in feedback onto subsequent precipitation and temperature anomalies. Here we present the results of additional model experiments, where we compare multi-member ensemble integrations of the CFS for a selection of these sensitive locations, starting from climatological soil moisture, and from climatological soil moisture everywhere except for the location of the patch in question. For each patch, three 15-member ensembles were produced in order to quantify the significance of the impact, and the non-linearity of the impact as a function of the sign and magnitude of the soil moisture anomaly.

References: Fan, Y., and H. van den Dool (2004), Climate Prediction Center global monthly soil moisture data set at 0.5° resolution for 1948 to present, J. Geophys. Res., 109, D10102, doi:10.1029/2003JD004345.

Hong, S.-Y. and H.-L. Pan, 1996: Nonlocal boundary layer vertical diffusion in a medium-range forecast model. Mon. Wea. Rev., 124, 2322-2339.

Huang, J. and H. M. van den Dool, 1993: Monthly precipitation-temperature relation and temperature prediction over the U.S. J. Climate, 6, 1111-1132.

Pan, H-L. and L. Mahrt, 1987: Interaction between soil hydrology and boundary layer developments. Boundary Layer Meteor., 38, 185-202.

Van den Dool, H. M., Jin Huang and Yun Fan, 2003: Performance and Analysis of the Constructed Analogue Method Applied to US Soil Moisture over 1981-2001. J. Geophys. Res., 108(D16), 8617, doi:10.1029/2002JD003114,2003.