Abstracts for the 6th International GAME Conf.

3-5 December 2004

Kyoto Japan

IMPACT OF ISLSCP-II INITIATIVE GLOBAL SOIL WATER STORGE CAPACITY OF THE ROOTING ZONE DATA ON T80 GCM

M. Ravindranath (1)

IMPACT OF ISLSCP-II INITIATIVE GLOBAL SOIL WATER STORGE CAPACITY OF THE ROOTING ZONE DATA ON T80 GCM ABSTRACT Simulation of Asian Summer Monsoon is still a challenging task even after 4 decades of efforts using numerical weather prediction techniques. Prediction of the strength of the Indian summer monsoon, its spatial behavior and the amount of precipitation is of great importance to Indian economy. Models incorporating complex surface processes including physically based descriptions of soils and vegetation have been developed since mid 1980s. When these models are coupled to general circulation models significant differences are reported due to land surface / atmosphere interactions in time scales ranging from days to several weeks. The influence of different land surface parameters like vegetation cover, snow cover, ice cover, soil moisture and albedo on atmospheric circulatory patterns have been investigated by many authors. Earlier studies experimenting with evapotranspiration at potential rate over dry surfaces in the interiors of large continents found that surface drying had little effect on precipitation rates in Southeast Asia and India. Further, over saturated land surface, changes in precipitation are directly related to changes in low-level moisture convergence associated with anomalous low-level flow. Over dry land surface, although low-level moisture convergence persists, it is unrelated to the modification of the tropical precipitation. The T80/L18 GCM operational at National Centre for Medium Range Weather Forecasting, India incorporates a simple land surface scheme in which soil moisture evolution is simulated fixing the bucket capacity at 150 mm. By hindsight, it is incorrect to fix the bucket capacity through the model grid since the partitioning of sensible and latent heat fluxes may be prone to error. In the present work, it is attempted to use variable bucket capacity over model grid for which the GEWEX ISLSCP-II initiative “Global Soil Water Storage Capacity of the Rooting Zone” data is used. The experiment is conducted for June 2004, the first month of Asian Summer Monsoon. The global data assimilation and forecasting scheme including analysis (spectral statistical interpolation) and forecast (T80/L18 with variable bucket capacity implementation) is run for each day to produce 5-day forecasts. Mean fields of analysis and 5-day forecasts are worked out for operational and experimental results. Initial diagnostics suggested changes in low level circulatory patterns, partitioning of sensible and latent heat fluxes and rainfall. The RMSE and mean errors in temperature have shown significant improvement over Europe and North America. For Asian region the improvement is marginal.

Submittal Information

Name : Date :
    Dr. M. Ravindranath
    26-Jul-04-15:30:16
Organization : Theme :
    National Centre for Medium Range Weather Forecasting
    Theme 1
Address : Presentation :
    A-50, Institutional Area, Phase-II, Sector-62, NIODA-210307, Uttar Pradesh, India
    Poster or oral
Country : Abstract ID :
    INDIA
    T1DMR26Jul04153016
Phone : Fax :
    0120 2403900,1,2,3,4,5,6,7 Ext.271 (office), 011 28531651 (Residence)
    91 120 2400062
E-mail :
    mrn@ncmrwf.gov.in , mrnath@email.com