Transcript Algorithm Name - ISAC

Hydro-Estimator (HE)
Bob Kuligowski, Clay Davenport,
Rod Scofield, Gilberto Vicente
NOAA/NESDIS/ORA
Theory / Schematic
• Algorithm Inputs (IR, MW, NWP):
– 10.7-µm IR window Tb’s from GOES-9, -10, -12,
Meteosat-5 and -7
– NAM or GFS PW, 1000-700 hPa mean RH, u, v,
convective EL computed from T, q profile
– Satellite inputs are from GVAR feeds; model inputs
come from NCEP
• Algorithm Process (how the inputs are converted
to rainfall estimates)
– Adjust Tb (Tadj) by reducing values where convective
EL temperature>213 K
– Z=-(Tadj-µT)/σT: rain only where Z>0
– Rain rate=f(Tadj, Z, PW)
– Reduce rain rate in low-RH environments
Theory / Schematic
• Strengths and Weaknesses of Underlying Assumptions
– Standard IR assumption that Tb is a proxy for cloud depth /
updraft strength and hence for rain rate; works best for
convective precipitation
– Assumes rainfall only in areas of positive Z (local Tb minima);
effective screening of cirrus by using Z
– Adjusts for environments with low convective EL by adjusting Tb
downward based on convective EL temperature, but still
underestimates warm-cloud rainfall
– Underestimates rainfall early in convective life cycle where
updrafts are strong and clouds are rapidly cooling, but still
relatively warm
• Planned Modifications / Improvements
– Currently undergoing recalibration using 6 weeks of CONUS
data from summer 2003 with bias-adjusted radar as target data;
should be completed by end of summer
– Inclusion of Lagrangian ΔTb to improve performance in early
stages of convection; work planned for this fall
Algorithm Output Information
• Spatial Resolution: 4 km Western Hemisphere, 6 km
elsewhere
• Spatial Coverage: global (60°S – 60°N)
• Update Frequency: same as IR update frequency
– 15 min over CONUS
– Generally 30 min elsewhere, but up to 3 h in parts of Southern
Hemisphere
• Data Latency: ~10 min after data received at ORA
• Source of Real-Time Data:
– (graphic) http://www.orbit.nesdis.noaa.gov/smcd/emb/ff/auto.html
– (digital)
ftp://www.orbit.nesdis.noaa.gov/pub/smcd/emb/f_f/hydroest/worl
d/world/
Algorithm Output Information
• Source of Archive Data:
– limited online archive at real-time ftp site
– offline global archive back to 25 May 2005
– offline CONUS archive back to April 2003
• Capability of Producing Retrospective Data (data
and resources required / available)
– CONUS: tape archive of component files back to
1997
– Northern Hemisphere: can get GOES IR data from
CLASS (back to December 2003) and use archive
Eta adjustment files
– Elsewhere: need 10.7-µm data and AVN/GFS fields
(PW, RH, T, u, v)