Abstract
Over the last two decades, several scientists have used Garcia's record of highly reflective cloud (HRC) to study the El Niño–Southern Oscillation (ENSO). Recently Waliser and Zhou removed a satellite bias. This note describes a test for the presence of the ENSO signal in the corrected record. The test treats anomaly values of corrected HRC in a grid that covers the equatorial western Pacific Ocean. For each box in the grid, the HRC anomaly was averaged over El Niño events in the record. From the averages, a map of the El Niño HRC anomaly was made. Similarly, a map of the La Niña HRC anomaly was made. Each map shows a strong, east-southeast– west-northwest trending dipole. The El Niño dipole dips toward the west-northwest, implying excess cloud in the east-southeast; the La Niña dipole dips toward the east-southeast, implying excess cloud in the west-northwest. In respect to these dipoles, the pair of HRC anomaly maps closely resembles published ENSO rain anomaly maps. The mapping was repeated for the part of the HRC record that overlaps a record of outgoing longwave radiation (OLR). Composite maps of OLR contain dipoles opposite in sign to the HRC dipoles. Together with the OLR comparison, the test reveals a robust ENSO in the Garcia and Waliser–Zhou records of HRC. The presence of ENSO supports the use of corrected HRC for studies of more subtle interannual signals.
Corresponding author address: Dr. David W. Martin, Space Science and Engineering Center, University of Wisconsin—Madison, 1225 West Dayton Street, Madison, WI 53706. Email: dave.martin@ssec.wisc.edu
