Spatiotemporal Variation of Diurnal Cycle under the Different MJO Phases
Abstract
During a two-month special observing period (October - November 2011) of the MJO field campaign, which composed of several projects of CINDY2011, DYNAMO, AMIE, and LASP, two MJO events were captured by the intensive (3-hourly) sounding array deployed over the central Indian Ocean. While the upward moistening was confirmed before the onset of these events, both cases were identified as an MJO event after the cloud systems reached over the central Indian Ocean from the Inter-tropical Convergence Zone in the Southern Hemisphere. While this feature suggests the lateral transport of moist air, dry intrusion into the equatorial region in the lower/mid-troposphere was also observed. The relationship among these features are not well understood. In the previous studies related to the recharge process under the suppressed condition with dry air aloft, diurnal cycle was a key to moisten the dry atmosphere above. Thus, as a first step to understand their relationship as well as a role for the initiation process of the MJO convection over the equatorial region, vertical features obtained by the radiosonde sounding at the southern array were examined with focus of diurnal cycle as a basic variation by referring the MJO phase defined by Wheeler and Hendon's method. Basically, stable layers near 0 C (~550 hPa) and trade inversion (800~750 hPa) became dominant over the equatorial sites after the MJO convective center moved east (Phases 4-7). During the pre-onset and onset period (Phases 2-3), lower troposphere (~970 hPa) became more unstable in nighttime (18-04 LT) and moist air region extended to upward from early morning (03-06 LT, ~700 hPa) to mid-troposphere in daytime (12-18 LT, 500~300 hPa). Stable layers near the trade inversion and 0 C rather appear accompanied with convections (i.e. convection might produce or contribute those stable layers).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A31F0163Y
- Keywords:
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- 3371 ATMOSPHERIC PROCESSES Tropical convection;
- 3373 ATMOSPHERIC PROCESSES Tropical dynamics;
- 3374 ATMOSPHERIC PROCESSES Tropical meteorology