Objectives: To investigate the role of land surface processes and of anomalies in land surface conditions in determining the predictability and variability of monsoon climates.

Work description:

MF: The influence of land-surface processes on the predictability of seasonal and intraseasonal variations will be studied by performing seasonal hindcast experiments with an atmospheric GCM in which the soil water content will be prescribed and initialized from observed datasets for selected past years based on the dataset of GSWP (Global Soil Wetness Project). An extension of the experiment to other years will be made pending on the availability of further soil water dataset from the ERA-40 or phase 2 of GSWP.

ICTP: The results of ensembles of seasonal integrations designed to isolate the effects of anomalous land surface conditions on the Asian Summer Monsoon will be diagnosed in detail using mode analysis (e.g. Empirical Orthogonal Functions (EOF), Singular Value Decomposition (SVD)). Specifically, the relationship between winter snow depth anomalies, anomalies in surface energy fluxes, land surface temperatures and soil moisture in spring, and monsoon circulation/rainfall anomalies in early summer will be established.

ICTP: The sensitivity of convective rainfall over the Amazon and Congo basins during the northern winter to soil moisture anomalies, and to their representation by land surface parametrization schemes, will be investigated. Soil moisture/evaporation anomalies over the tropical continents will be generated by modifying the soil water fluxes and/or evapotranspiration properties in the surface parametrization scheme of the model. Different versions of the model parametrizations schemes may also be used. The design and validation of the experiments will be done in collaboration with ECMWF.

MPG.IMET: The impact of land surface conditions (snow, vegetation) on monsoon interannual and interdecadal variability will be studied by means of long coupled model integration, supported by simulations with atmospheric models forced with boundary values (SST, snow, soil wetness).

UB: Diagnostic studies of observed relationships between rainfall and continental surface conditions will be undertaken through statistical couplings (e.g. Canonical Correlation Analysis (CCA), SVD) and multi-linear objective regressor selections. Numerical experiments including impacts of carefully defined modifications to the continental surface conditions are also planned with an atmospheric GCM with a sophisticated parametrization of land surface processes.

Deliverables:

D1301: Understanding of the relationships between Eurasian snow depth, springtime surface variables and monsoon circulation/rainfall anomalies based on results of numerical simulations.

D1302: Assessment of the sensitivity of the tropical circulation and the associated hydrological cycle to local, regional anomalies in land surface/vegetation conditions.

Milestones:

Year 1: Evaluation of the sensitivity of intraseasonal predictability to soil moisture. Description of the mechanisms of the Eurasian snow/monsoon relationship.

Year 2: Experimentation on the impact of land surface conditions and vegetation properties in the Amazon and Congo basins.

Year 3: Assessment of the influence of local, regional anomalies in land surface/vegetation conditions on monsoon variability on intraseasonal to decadal timescales.