Nowcasting the 3 May 1999 Oklahoma tornado outbreak using the AERI ground-based interferometer

The Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program has funded the development and installation of five Atmospheric Emitted Radiance Interferometer (AERI) systems around the Southern Great Plains Cloud And Radiation Testbed (SGP CART). The AERI instruments measure atmospheric emitted radiance to within 1% ambient radiance at one wavenumber resolution from 3-20 micrometers at ten minute temporal resolution. This high spectral resolution radiance information is inverted through a form of the infrared radiative transfer equation to produce temperature and water vapor profiles within the planetary boundary layer (PBL; to three kilometers), effectively mapping the thermodynamic state of the lower troposphere. The operational meteorological nowcasting value of the AERI instruments are explored. Taking advantage of the ten minute resolution of the AERI profiles, the 3 May 1999 Oklahoma tornado outbreak is analyzed.

Tropospheric changes related to the rapid (on the order of 1-2 hours) dissipation of a capping temperature inversion within the PBL and increasing PBL moisture lead to the systematic development of severe convection on this day. The AERI systems were able to monitor the trends in bulk atmospheric stability via diagnosed quantities such as surface based parcel equivalent potential temperature, inversion intensity, convective available potential energy, and convective inhibition. The high temporal resolution of temperature and moisture profiling and bulk stability information is unique. Currently special radiosonde launches (non-synoptic) are the only widely used means to determine this stability information.

The array of five AERI instruments within Oklahoma and Kansas (co-located with wind profilers) offers the operational forecaster a unique and important data source for the thermodynamic evolution of the PBL, convective instability and numerical weather prediction model validation.