Estimating convection's moisture sensitivity: An observation-model synthesis using AMIE-DYNAMO field data

Brian Mapes, Arunchandra S. Chandra, Zhiming Kuang, Siwon Song, Paquita Zuidema

Research output: Contribution to journalArticle

Abstract

We seek to use ARM MJO Investigation Experiment (AMIE)-DYNAMO field campaign observations to significantly constrain height-resolved estimates of the parameterization-relevant, causal sensitivity of convective heating Q to water vapor q. In field data, Q profiles are detected via Doppler radar wind divergence D while balloon soundings give q. Univariate regressions of D on q summarize the information from a 10-layer time-pressure series from Gan Island (0°, 90°E) as a 10 × 10 matrix.Despite the right shape and units, this is not the desired causal quantity because observations reflect confounding effects of additional q-correlated casual mechanisms. We seek to use this matrix to adjudicate among candidate estimates of the desired causal quantity: Kuang's matrix M of the linear responses of a cyclic convectionpermitting model (CCPM) at equilibrium. Transforming M to more observation-comparable forms by accounting for observed autocorrelations, the comparisons are still poor, because (we hypothesize) largerscale vertical velocity, forbidden by CCPM methodology, is another confounding cause that must be permitted to covary with q. By embedding Mandmodified candidates in an idealized GCM, and treating its outputs as virtual field campaign data, we find that observations favor a factor of 2 (rather than 0 or 1) to small-domain M's free-tropospheric causal q sensitivity of about 25% rain-rate increment over 3 subsequent hours per +1 gkg-1 q impulse in a 100-hPa layer. Doubling this sensitivity lies partway toward Kuang's Mfor a long domain that organizes convection into squall lines, a weak but sign-consistent hint of a detectable parameterization-relevant (causal) role for convective organization in nature. Caveats and implications for field campaign proposers are discussed.

Original languageEnglish (US)
Pages (from-to)1505-1520
Number of pages16
JournalJournal of the Atmospheric Sciences
Volume76
Issue number6
DOIs
StatePublished - Jun 1 2019

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Keywords

  • Convective-scale processes
  • Diabatic heating
  • Parameterization
  • Regression analysis
  • Tropical variability
  • Tropics

ASJC Scopus subject areas

  • Atmospheric Science

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