Observed characteristics of the MJO relative to maximum rainfall

• Published in: Journal of the atmospheric sciences Vol. 64; no. 7; pp. 2332 - 2354
• Main Authors: BENEDICT, James J, RANDALL, David A
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.07.2007
• Subjects: Atmospheric models; Climatology; Clouds; Convection; Convective transport; Cumulus clouds; Cumulus congestus; Datasets; Drying; Earth, ocean, space; Exact sciences and technology; External geophysics; Fields; General circulation models; Geographical locations; Global precipitation; Hydrologic data; Life cycles; Lower troposphere; Madden-Julian oscillation; Maximum rainfall; Mesoscale processes; Meteorology; Moisture; Moisture effects; Physics of the high neutral atmosphere; Precipitation; Rainfall; Rainfall data; Statistical methods; Studies; Tropical rainfall; Tropical Rainfall Measuring Mission (TRMM); Troposphere; Variables; Vertical advection; Climatology; rainfall; Cumulus cloud; atmospheric precipitation; Energy transport; clouds; troposphere; intensity; Mesoscale; instability; warming; TRMM satellite; horizontal component; Madden Julian oscillation; Composite analysis
• DOI: 10.1175/jas3968.1
• ISSN: 0022-4928

This study examines various dynamical and thermodynamical processes that characterize the Madden-Julian oscillation (MJO). Episodes of deep convection related to the MJO based on rainfall data from the Tropical Rainfall Measuring Mission (TRMM) satellite and the Global Precipitation Climatology Project (GPCP) are identified. Although broad convective envelopes are located utilizing spectrally filtered precipitation, analyses of the features within the envelopes are carried out using unfiltered rainfall and 40-yr ECMWF Re-Analysis (ERA-40) fields. The events are composited and categorized based on geographic location and relative intensity. The composited fields illustrate that, prior to the onset of deep convection, shallow cumulus and cumulus congestus clouds are actively involved in vertical convective transport of heat and moisture. Drying, first accomplished immediately following deep convection in the lower troposphere, is associated with an enhanced horizontal (westerly) advective component and may be related to mesoscale processes. Drying related to deep-layer subsidence is delayed until one to two weeks following intense rainfall. The importance of gradual lower-tropospheric heating and moistening and the vertical transport of energy and moisture are shown in a comparison of vigorous and weak MJO events. Additionally, a comparison of the composite fields to proposed wave instability theories suggests that certain theories are effective in explaining specific phases of the disturbance, but no single theory can yet explain all aspects of the MJO. The discharge-recharge and frictional moisture convergence mechanisms are most relevant for explaining many of the observed features of MJO evolution. [PUBLICATION ABSTRACT]