Overview of weather products generated by NCAR as part of Google-Meningitis
The TIGGE Project is the institutional basis of the weather products UCAR is
generating as part of the Google.org-funded meningitis effort. TIGGE, the THORPEX
Interactive Grand Global Ensemble, is a key component of THORPEX: a World
Weather Research Programme to accelerate the improvements in the accuracy of 1day to 2 week high-impact weather forecasts for the benefit of humanity. The TIGGE
archive consists of ensemble forecast data from ten global NWP centers, starting
from October 2006, which has been made available for scientific research. However,
consistent reporting has reduced the number of useful reporting centers to eight, for
a grand total of 209 ensemble members for each weather variable and each forecast
lead-time. Current ensemble weather variable products generated over Africa are
focused on surface-level fields (temperature, dewpoint, windspeed, precipitation,
surface latent and sensible heat flux, and shortwave and longwave radiation),
although weather variables at other pressure-levels could also be made available.
Actual delay times in accessing the forecast products are roughly 12hrs from the
initialization time for most centers.
As now commonly accepted, these products by themselves have known biases; and
as ensemble (probabilistic) products, are also typically under-dispersive (i.e. overconfident in the range of forecast error). As a result, these products typically need to
be calibrated or “post-processed” first before their use in applications. We are
developing a post-processing routine based on quantile regression that operates on
the TIGGE ensemble to produce a new set of ensemble members that have correct
statistical properties while enhancing the information content of the ensemble’s
associated probability distribution function. This new set of gridded ensembles can
then be used directly into disease models. This post-processing procedure is
currently using the NASA MERRA reanalysis and a merged NOAA-NASA-GTSraingauge precipitation products as “truth” in the calibration process. However
other data sources (e.g. other reanalysis products ERA-Interim or NCAR/NCEP
Reanalysis, or local weather station information) could alternatively be used by the
post-processing algorithms. The products we’re generating are gridded products;
however, for a set of pre-determined locations (aka village-level), forecasts could be
point-processed with their results posted to web-site or sent out automatically via
ftp.
We are currently developing a web site that will be a front-end to UCAR’s Unidata
RAMADDA system (RAMADDA: a web-based content repository, publishing
platform and collaboration environment for the Earth Sciences; see
http://www.unidata.ucar.edu/software/ramadda) to make these forecast products
publicly-available that we anticipate should be operational well-before the
beginning of the upcoming meningitis season. We are also in the early planning
stages of enhancing the products’ usefulness to the more casual user by expanding
the web interface to allow users to input their latitude and longitude coordinates,
and receive TIGGE forecasts of their requested weather variable (or meningitis
forecast) of choice at lead-times out to 2 weeks in advance.