The mesoscale convection life cycle: building block or prototype for larger-scale tropical waves? Brian U. of Miami Stefan Tulich, Jialin NOAA ESRL/PSD (formerly CDC) Paquita U. of Miami paper in press at Dynamics of Atmospheres and Oceans contact

Resemblances a)MCS: Zipser 1969 b)MCS: Zipser et al c)2-day: Takayabu et al d)Kelvin: Straub & Kiladis 2004 e)MJO: Lin and Johnson 1996

Outline Multiscale resemblance illustrated from obs –Samples and regression composites –Smallest scale (building block): mesoscale (10’s km, h’s) –but with convective cell substructure –On up to intraseasonal Null hyp: LS structure inherited from MCS ‘block’ –rejected Instead: zones of (cu, cg, cb, ns) cloud type enhancements Why and how? –How to interpret humidity, divergence: proxies or causes of ‘convection’?

TOGA-COARE data sources at various scales Sounding array data: CSU gridsVAD: ship radar (48km radius)

Doppler radar VAD results: 48km radius lag-p regressions of divergence vs. Z-R rainrate mean of 7 field programs (~10 4 h data) (pattern similar in each of the 7) Mass flux (-  Mapes and Lin 2005 MWR Multi-hour time scale: artifact of spatial scale? s -1 per mm/h Only slight mass-balance adjustment needed

Point data (5’ vertically pointing cloud radar coverage vs. gauge rain, EPIC 2001): irreducible multi-hour time scales? cu dynamics (multi- cellular) anvil micro- physics… …including stratiform rain

Evolution (tilt) similar across timescales with fixed spatial scale (OSA divergence) 30d total LP +BP +HP =

dawn visible pix at those 4 times b) d) a) c)

Building block null hypothesis: that multiscale tilt is reproducible by superposition of fixed-structure (VAD derived) divergence building blocks hmmm… No.

Rather, the MCS life cycle appears to be a prototype for larger-scale waves. Zipser et al zones of different cloud types

LS zone favors cu…… or cb… or ns anvils How is multiscale structure resemblance achieved?

What variables modulate cloud types in these LS zones? Hypothesis: T, q (via parcel buoyancy): emphasis on leading edge Rain autocorrelation

Entraining plume buoyancy, and its parts Pure parcel effect Moistness of entrained air “Explains” “convection”? capping effect

Wrapup Multiscale resemblance illustrated from obs –Smallest scale (building block): mesoscale with convective substructure –COARE sounding array: ~2 day, ~2 week, ~40d periods Slow evolution is not just a convective cloud life cycle, aliased upscale: rather, there are zones of cloud type (cu, cg, cb, ns) enhancements –On both MCS and larger scales Why and how? –Leading edge: perhaps governed via plume buoyancy? Circularity: is q proxy or cause? “moisture-convection feedback” –Trailing edge: more subtle? - Shear? Wave ascent? –Careful! Filtering can introduce spurious congestus stage - stratiform stage antisymmetry! Or is it a “vertical mode?”

Extra slides

OSA specific humidity 6d 24d 40d 6 hourly data daily means 4d means

COARE divergence: OSA, IFA, VAD OSA IFA VAD conv div 48h rain

Smallest scale: mesoscale (hours) even in “point” data Gauge rain Composites wrt +1 stdev excursions Regressions vs. gauge rain 5 minute data