Diagnostic Boundary Layer Moistening Process for Three MJO Events During DYNAMO IOP
Abstract
We analyze data observation during DYNAMO field experiment from October 1 to December 31 2011. Three MJO events were observed and analyzed. The data includes ECMWF Interim and TRMM (2A23, 3B42) to focus on the diagnostic process of boundary layer moistening and shallow convection. We examine the dynamics of low level moistening of the sounding array through scale-separation and moisture budget in Indian Ocean. Variables are separated into four different time scales which are over 60 days (low frequency), 20 to 60 days (MJO scale), below 20 days (synoptic scales) and the unresolved dynamics (eddy activity). The result reveals that dominant balance comes from synoptic scale and unresolved dynamics. During phase 5 to 8 of MJO that occurred in October and November, eddy activities contribute to moistening but synoptic-scale subsidence causes drying in the boundary layer, somewhat different from Hsu et al (2012) who emphasized that mean state moisture and wave activity contribute dominantly to boundary layer moisture convergence. From TRMM 2A23, low- and mid-level cloud increases during the suppressed phase, suggesting that developing shallow convection plays an important role in the low-level moistening prior to the deep convective phase of MJO. This is consistent with previous findings over western Pacific that cloud top height increases from suppressed phase (phase3 and 4) to convective phase (phase 5). This is also line with studies emphasizing hierarchy cloud structure embedded in MJOs multi-scale waves.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A31F0152T
- Keywords:
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- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE Cloud/radiation interaction