ESRL Global Systems Division

SCATCAT (Severe Clear Air Turbulence Colliding with Air Traffic)

Forecast Systems Laboratory, in collaboration with NOAA's Environmental Technology Laboratory, NCAR, and the FAA Aviation Weather Research Program, is conducting research to improve forecasts of clear air turbulence (CAT) and to characterize CAT through observations. Since 1996, experimental forecasts of turbulence in the vicinity of jets and upper-level fronts have been produced at FSL ( Diagnosed from the wind and temperature data of FSL's Rapid Update Cycle model (RUC) and plotted at 1000- ft intervals between 2,000 and 42,000 ft AGL, 3- to 12-h forecasts of turbulence for the 48 states are updated every three hours. These forecasts are also part of the Integrated Turbulence Forecast Algorithm appearing on the Aviation Digital Data Service ( at NOAA/NCEP's Aviation Weather Center in Kansas City.

These products have allowed aviation users access to turbulence forecasts that are more timely and detailed than has been previously available. However, there is room for improvement, as real-time verification statistics indicate (see

Field work will be done in the Pacific Ocean this winter to define meteorological conditions that produce turbulence. The field phase of SCATCAT01 (Severe Clear Air Turbulence Colliding with Air Traffic) will observe turbulence above 20,000 ft. in the vicinity of jets streams, upper fronts, and prefrontal convection by using NOAA's Gulfstream IV aircraft. Of particular interest is the relationship between the internal wind shears and associated gravity waves of fine-scale, stable, laminar structures (seen in the SCATCAT99 data sets) and clear air turbulence. NOAA's Gulfstream IV (G-IV) aircraft will deploy high-spatial-resolution dropsondes (at approximately 40-km intervals) in regions where turbulence is anticipated to occur, and will confirm the presence or absence of turbulence in these regions by in-situ observations of turbulence from the aircraft. The G-IV will operate from Honolulu, Hawaii, from 20 January through 26 February 2001. The dropsonde data and in-situ turbulence measurements will guide NOAA and NCAR scientists in simulating turbulence in numerical prediction models and in making improvements to current CAT diagnostics.

SCATCAT01 will operate in collaboration with several others programs. Similar to interactions during NOAA/NCEP Winter Storms Reconnaissance 1999 (WSR99), SCATCAT and WSR01 will share observations and leverage flights on cases of mutual interest. Flights will also be performed with NASA for calibration of the HIRS instrument.

More information:

Contact information
Name: Cecilia Girz
Tel: 303-497-6830