The Greening of the McGill Paleoclimate Model. Part I: Improved Land Surface Scheme With Vegetation Dynamics

The formulation of a new land surface scheme with vegetation dynamics for coupling to the McGill Paleoclimate Model (MPM) is presented. The new land surface component incorporates significant improvements over the old version used in the MPM, which can be summarized as follows: (i) Parameterization of deciduous and evergreen forests by using the model's climatology and the output of the dynamic global vegetation model: VECODE, developed by Brovkin et al.; (ii) Parameterization of leaf budburst and drop by using the model's climatology and plant function type dependent threshold values for these quantities; (iii) Parameterization of the seasonality of leaf area index by using time-dependent growth; (iv) Calculation of land surface albedo by using vegetation-related parameters, snow depth and the model's climatology. The results show considerable improvement of the model's simulation of the present-day climate. In particular, the strong seasonality of terrestrial vegetation and the associated land surface albedo variation are in good agreement with several satellite observational datasets. The first application of this new version of the MPM to Holocene millennial-scale climate variability is described in a companion paper, Part II.