Global Land Data Assimilation System (GLDAS)
Index name: Global Land Data Assimilation System (GLDAS).
Ease of use: Green.
Origins: Rodell led the work, which involved scientists from NASA and NOAA in the United States.
Characteristics: Uses a system of surface and remotely sensed data along with land surface models and data assimilation techniques to provide data on terrestrial conditions. Output includes soil moisture characteristics, which are a good drought indicator.
Input parameters: Land surface models, surface-based meteorological observations, vegetation classifications and satellite data.
Applications: Useful for determining river and streamflow projections as well as runoff components based on current conditions; ideal for monitoring droughts that have multiple impacts.
Strengths: As it is global in nature and available at a high resolution, it can represent most areas. Useful for monitoring developing drought in areas that are data poor.
Weaknesses: The grid size is not sufficiently fine for island nations. Only areas that lack near-real-time surface observations are represented by the data assimilation process.
Resources: The methodology and inputs are described well in the literature. Output is available online.
Mitchell, K., D. Lohman, P. Houser, E. Wood, J. Schaake, A. Robock, B. Cosgrove, J. Sheffield, Q. Duan, L. Luo, R. Higgins, R. Pinker, J. Tarpley, D. Lettenmaier, C. Marshall, J. Entin, M. Pan, W. Shi, V. Koren, J. Meng, B. Ramsay and A. Bailey, 2004: The multi-institution North American Land Data Assimilation System (NLDAS): utilizing multiple GCIP products and partners in a continental distributed hydrological modelling system. Journal of Geophysical Research, 109:D07S90, doi:10.1029/2003JD003823.
Rodell, M., P. Houser, U. Jambor, J. Gottschalck, K. Mitchell, C.-J. Meng, K. Arsenault, B. Cosogrove, J. Radakovich, M. Bosilovich, J. Entin, J. Walker, D. Lohmann and D. Toll, 2004: The Global Land Data Assimilation System. Bulletin of the American Meteorological Society, 85(3):381–394.
Xia, Y., K. Mitchell, M. Ek, J. Sheffield, B. Cosgrove, E. Wood, L. Luo, C. Alonge, H. Wei, J. Meng, B. Livneh, D. Lettenmaier, V. Koren, Q. Duan, K. Mo, Y. Fan and D. Mocko, 2012: Continental-scale water and energy flux analysis and validation for the North American Land Data Assimilation System project phase 2 (NLDAS-2): 1. Intercomparison and application of model products. Journal of Geophysical Research, 117:D03109, doi:10.1029/2011JD016048.