The Effect of ENSO and Other Sources of Large-Scale Variability on Observed Bright Bands over Manus, Papua New Guinea

Stratiform rain is characterized by a distinctive radar signature called the bright band, a layer of strongly enhanced reflectivity where falling snow is beginning to melt. As part of a study into the possibility of calibrating tropical wind profilers long after they had been removed from the field, we recently found ourselves confronted with the following question: Do the characteristics of observed bright-bands over a particular location vary as a function of ENSO? ENSO is obviously a major signal in the tropical west Pacific, where the profiler used in our proof-of-concept study was deployed, and passed through multiple phases during the two different time periods from which the calibration data came. In order to evaluate the potential impact of using bright-band data during different ENSO phases on our satellite-based calibration, we have examined relationships between various ENSO indicators, freezing levels from the Twentieth Century Reanalysis Project version 2c global reanalysis, and bright-band heights and reflectivities observed by the Manus 915 MHz profiler (July 1992–August 1994) and the TRMM precipitation radar (January 1998–July 2001).