Flood Forecast based on JASON-2 data
Forecast as on 26 September, 2016
Valid Up to: 4 October, 2016
FloodoutlookofBangladesh
Forecast Summary
The Brahmaputra-Jamuna & Padma rivers may rise while The Ganges river
may remain steady in the next 8 days. Click here to see the dynamic forecast
hydrographs.
Notes:
This satellite-assisted flood forecasting system uses satellite observations of river levels using radar
nadir altimetry. These river levels are then used in ‘forecast’ mode to predict the anticipated water
level at the boundary location of the Bangladesh flood modeling domain. Using upstream
information of river levels that have a few 100 of km of travel time, it is possible to forecast the river
level downstream inside Bangladesh up to 8 days ahead. During 2014, only JASON-2 (an altimeter
operated by NASA and French Space Agency CNES) was used. In 2015, a French-Indian satellite
altimeter called AltiKa (SARAL) was added to the system to progressively build on the skill of the
forecasting system. The location of where JASON-2 and AltiKa altimeters cross rivers upstream of
Bangladesh are shown in the map below. JASON-2 typically has a 10 day repeat while AltiKa has a 35
day repeat (i.e., it takes 35 days for it to come back and sample the same point).
Figure 1. Location of satellite altimeter crossings (known as ‘virtual stations’) over rivers in the South Asian
Rivers of Ganges, Brahmaputra, Meghna and Indus. Upper panel – AltiKa (SARAL); Lower panel – JASON-2. In
this operation by FFWC, locations over Ganges and Brahmaputra were used. Four virtual stations on Ganges
and three virtual stations on Brahmaputra were used from JASON-2 observing system. For AltiKa, more than
10 virtual stations were used for each of the rivers. The combine observational power of JASON-2 and AltiKa is
expected to reduce the sampling gap in monitoring river levels upstream and improve accuracy of flood
forecasting in 2015 compared to 2014.
Interested users may find more information on JASON-2 at http://www.nasa.gov/mision_pages/ostm/main/index.html.
For AltiKa, readers may refer to http://www.aviso.altimetry.fr/en/missions/present-missions/saral/instruments/altika-aka-band-altimeter.html .
Near real-time data on JASON-2 and AltiKa are made available at a publicly accessible ftp site at ftp://avisoftp.cnes.fr/ as
Interim Geophysical Data Records (IGDR). The current flood forecasting operations were made possible through the NASAUSAID program called SERVIR in coordination with International Center for Integrated Mountain Development (ICIMOD),
Institute of Water Modeling (IWM), University of Washington, University of Houston and Ohio State University. Details of how
the flood forecasting approach works is available in a number of peer-reviewed publications that may be accessed from
www.saswe.net/publications-2/hydrology as well as http://www.servirglobal.netFFWC is now able to independently take
advantage of satellite altimeter observations of river levels in near real-time and assimilate them in their flood forecasting
system to extend lead time up to 8 days.