Active Modes of the Pacific Intertropical Convergence Zone (ITCZ)
Abstract
Satellite-observed outgoing longwave radiation (OLR) data from eight 6-month cool seasons were examined to find periods of active convection within the Pacific intertropical convergence zone (ITCZ). Descriptive statistics were used to define and describe the time-mean behavior of the Pacific ITCZ. Two seasons (76-77 and 82-83) showed distinctive El Nino-Southern Oscillation (ENSO) signatures in mean, standard deviation, and frequency distribution of OLR. Four other seasons (74-75, 75-76, 79-80, and 80-81) had 'normal' OLR statistics. The remaining seasons preceded and followed the major 82-83 event and had intermediate seasonal-mean OLR fields. Time series of an index measuring convective intensity in the ITCZ were analyzed to find active convection periods. Time-longitude diagrams of intensity estimates showed how active modes develop, spread, and propagate across the Pacific. Three types of variability of the active modes were identified. The first type had small spatial scales (<4000 km), short temporal scales (10-20 day durations), and occurred mostly in the eastern Pacific. The second type had longer spatial scales (5000-10,000 km), short temporal scales, and was found throughout. The second type also showed evidence of propagation. The third type had large temporal scales (< 30 days), medium spatial scales (2000-6000 km),and was a fixed feature. This third type may be a result of combinations of two or more active periods of the first two types.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1988
- Accession Number
- ADA196406
Entities
People
- Patrick M. Hayes
Organizations
- Air Force Institute of Technology