Free-Tropospheric Moisture Convergence and Tropical Convective Regimes HIROHIKO MASUNAGA Nagoya University Tropical convective regimes Tropical convective regimes: Climatology Johnson et al., J. Clim., 1999 Climate Symposium 2014, Darmstadt Oct. 14, 2014 Tropical convective regimes Tropical convective regimes: Climatology “If only I realized that my vacation destination is among the rainiest places on earth…” Climate Symposium 2014, Darmstadt Oct. 14, 2014 Tropical convective regimes Tropical convective regimes: Variability A quiescent phase prevails even in the deep Tropics. Aimeliik, Palau, June 2013 Climate Symposium 2014, Darmstadt Oct. 14, 2014 Tropical convective regimes Tropical convective regimes: Variability A quiescent phase prevails even in the deep Tropics. COARE Dynamic Quiescent Serra et al., JGR, 1997 What factors separate the quiescent and dynamic phases in the tropics? Climate Symposium 2014, Darmstadt Oct. 14, 2014 Working Hypothesis Hypothetical dynamic and quiescent phases Climate Symposium 2014, Darmstadt Oct. 14, 2014 Satellite observations of T/q and convection Climate Symposium 2014, Darmstadt Oct. 14, 2014 Satellite observation: strategy Climate Symposium 2014, Darmstadt Oct. 14, 2014 Separation into two convective regimes quiescent phase dynamic phase Climate Symposium 2014, Darmstadt Oct. 14, 2014 Composite time series and moisture budget qv anomaly: Isolated cumulus regime qv anomaly: Organzied system regime Climate Symposium 2014, Darmstadt Oct. 14, 2014 Budget analysis: implementation Diagnosis under the moisture budget constraint - FT moisture convergence and vertical moisture transport at CB are derived using the moisture budget equations. CloudSat CLDCLASS σ FT: qC FT = ∂ t qFT − qCSC − E + Ps SC: qM CB = −∂ t qSC + qCSC + E + PCB − Ps AMSR-E Precip QuikSCAT u10 Time seires of qv SC reevaporation Bulk eq. w Ts and u10 † qCFT: Free tropospheric (FT) moisture convergence † qCSC: Sub-cloud layer (SC) moisture convergence † qMCB: Vertical moisture transport at cloud base (CB) † PCB, Ps : Precipitation at CB and at surface Climate Symposium 2014, Darmstadt Oct. 14, 2014 Temporal evolution in moisture budget Organized convection regime (left) Precipitation is fed largely by FT moisture convergence. Isolated cumulus regime (right) FT moisture is weakly diverging throughout. Climate Symposium 2014, Darmstadt Oct. 14, 2014 Moisture updraft and FTPE Derivation of moisture updraft and downdraft Breakdown of vertical moisture transport at CB and mass continuity at CB ↑ ↓ * a qM CB = qCB M + q M − CB CB + CB ↑ ↓ M CB = M CB + M CB together yield moisture updraft and downdraft ↑ M CB 2 unknowns with 2 equations a * qM CB − qCB M qM q − ↓ CB CB CB − M CB + , M CB = = * * a a − qCB − − qCB + qCB q − CB + Free tropospheric precipitation efficiency (FTPE) FTPE ≡ PCB ↑ q *CB− M CB Climate Symposium 2014, Darmstadt Oct. 14, 2014 Isolated Cumuli Clouds vary in population with little sign of deepening CB Moisture updraft, M↑CB [mm/h] M↑CB and FT Precipitation Efficiency (FTPE) Organized Systems Intensifying convection ↓ Stratiform rain ( ↑ FTPE ≡ PCB q *CB− M CB ) Climate Symposium 2014, Darmstadt Oct. 14, 2014 Isolated Cumuli ( ↑ FTPE ≡ PCB q *CB− M CB ) Moisture Convergence [mm/h] Moisture Convergence [mm/h] Self-sustaining growth vs. stable maintenance CB Moisture updraft, M↑CB [mm/h] Climate Symposium 2014, Darmstadt Oct. 14, 2014 Summary and discussion Organized system regime: Dynamic phase Isolated cumulus regime: Quiescent phase FT moisture convergence and precipitation efficiency in tandem enhance drastically toward peak convection. FT moisture stays diverging. Clouds vary in population but do not deepen. Diagnostics of the underlying mechanism Dynamics responsible for FT convergence or divergence Vertical mode decomposition (Masunaga and L’Ecuyer, 2014). Moisture/MSE convergence and gross moist stability (GMS) (Neelin and Held, 1987; Raymond et al., 2009, etc.). Climate Symposium 2014, Darmstadt Oct. 14, 2014 Vertical mode decomposition of qCFT Organized system regime (left) 1st barolinic mode predominates during peak convection. Isolated cumulus regime (right) Shallow mode is dominant throughout the evolution. Climate Symposium 2014, Darmstadt Oct. 14, 2014 MSE convergence and radiative cooling Organized system regime (left) qCWT >>0 and hCWT~0: zero GMS (marginally unstable?) Isolated cumulus regime (right) Weak qCWT and hCWT+QR<0: positive GMS (stable) † qCWT: Whole tropospheric moisture convergence † hCWT: WT MSE convergence Climate Symposium 2014, Darmstadt Oct. 14, 2014 Schematic summary Climate Symposium 2014, Darmstadt Oct. 14, 2014 Schematic summary QR<0 1st baroclinic mode Shallow mode Climate Symposium 2014, Darmstadt Oct. 14, 2014 Backup slides Climate Symposium 2014, Darmstadt Oct. 14, 2014 Evolution of CB moisture updraft/downdraft Climate Symposium 2014, Darmstadt Oct. 14, 2014 Outstanding questions Possible links to shallow meridional circulations Prominent in the tropical east Pacific (Zhang et al., 2003). Secondary but present also in other regions (Trenberth et al., 2000; Zhang et al., 2008). Zhang et al., 2003 Climate Symposium 2014, Darmstadt Oct. 14, 2014 Satellite observation: strategy - AMSR-E precipitation is from CSU GPROF2010 product and SST is from RSS. - Radiative heating rate is from the CloudSat 2B FLXRH product. - QuikSCAT u10 is from the SeaWinds Level3 daily gridded product (JPL PO.DAAC). Climate Symposium 2014, Darmstadt Oct. 14, 2014 Budget analysis: framework A two-layer model constructed with satellite data T(p) & q(p) Ps from AMSR-E us (or MCB) from QuikSCAT † CB: Cloud base † FT: Free troposphere † SC: Sub-cloud layer Climate Symposium 2014, Darmstadt Oct. 14, 2014 Analysis design Target region and period Global tropical oceans (15ºS-15ºN) 7 years from Dec. 1, 2002-Nov. 30, 2009 except for CloudSat with the beginning date of Jul. 1, 2006. Satellite instruments Satellite Instruments Local time of obs. Parameters to be derived TRMM PR Variable Convection Aqua AIRS/AMSU 1:30 am/pm T(p) and q(p) Aqua AMSR-E 1.30 am/pm CWV and P CloudSat CPR 1:30 am/pm σc(z) QuikSCAT SeaWinds 6:00 am/pm u10 Climate Symposium 2014, Darmstadt Oct. 14, 2014 Error statistics [mm/h] Ps [mm/h] < .qv>SC Background level 0.20 Std. Error (relative %) [kW/m2] < .sv>SC 0.23 0.16 -0.097 0.76 2.7×10-5 2.9×10-4 (0.12 %) 9.9×10-5 (0.062 %) 2.1×10-4 (0.22 %) 1.0×10-4 (0.013 %) 3.1×10-3 -3.5×10-2 2.5×10-3 -3.5×10-2 1.1×10-2 (0.014 %) (1.6 %) (15 %) Δ Bias (relative %) [mm/h] <QR> (1.6 %) (36 %) Climate Symposium 2014, Darmstadt Δ E [kW/m2] (1.4 %) Oct. 14, 2014 Sub-cloud layer reevpoartion rate SC reevaporation under the heat budget constraint L(PCB − P )s = −∂ t s SC + sC SC + QSC + S − sM CB ′ ≥ sCB M CB (eddy heat flux is sM CB = sCB M CB + s′M CB - “Maximum” SC reevaporation assumed positive.) ( ) PCB − Ps = − ∂ t s SC + sC SC + QSC + S − sCB M CB / L Climate Symposium 2014, Darmstadt Oct. 14, 2014 Composite CloudSat cumulus cloud cover (σc) p-t diagram of σc at R=0 Isolated Cumuli ↑ Isolated Cumulus Regime (TRMM Precip Cover < 25 %) ↓ Organized System Regime (TRMM Precip Cover > 50 %) Organized systems Climate Symposium 2014, Darmstadt Oct. 14, 2014 Regional dependence Climate Symposium 2014, Darmstadt Oct. 14, 2014 Estimation of large-scale vertical motion − q∇ ⋅ v − s∇ ⋅ v Lower-troposphere weighted convergence Upper-troposphere weighted convergence Climate Symposium 2014, Darmstadt Oct. 14, 2014 Vertical mode decomposition ω ( p, t ) = Ω bc1 (t ) f bc1 ( p) + Ω bc 2 (t ) f bc 2 ( p) + Ω shl (t ) f shl ( p) + ωbg 0 ( p) 3 observational constraints → 3 mode coefficients 1. q ∂ω ∂p = − q ∇ ⋅ v i) Ω bc1 : 1st baroclinic mode 2. s ∂ω ∂p = − s ∇ ⋅ v ii) Ω bc 2 : 2nd baroclinic mode 3. ω ( pCB ) = (∇ ⋅ u10 )∆pCB iii) Ω shl : shallow mode Climate Symposium 2014, Darmstadt Oct. 14, 2014 Derivation of background incl. shallow mode FT moisture convergence constraint ∂ q ωbg ∂p FT for background mean FT FT DSE convergence constraint s = − q∇ ⋅ v Background mean consists of first and last 12 h combined. ∂ ωbg ∂p = − s∇ ⋅ v FT for background mean FT Boundary condition at cloud base ωbg ( pCB ) = ω ( pCB ) for background mean Find the solution closest to ωrad minimize ∑ (ωbg − ωrad ) 2 p ωbg = ω shl + ωbg 0 f shl ( p ) ≡ ω shl ( p ) / ω shl ( pCB ) Climate Symposium 2014, Darmstadt Oct. 14, 2014 Time series of vertical mode coefficients CloudSat PRECIP-COLUMN Climate Symposium 2014, Darmstadt Oct. 14, 2014 Mode decomposition of GMS background-shallow total 1st baroclinic 2nd baroclinic Climate Symposium 2014, Darmstadt Oct. 14, 2014 ω mode vertical h advection h and q convergence − ω ∂h ≈0 ∂p − ω ∂h >0 ∂p − ω ∂h <0 ∂p − ω ∂h <0 ∂p − ω ∂q >> 0 ∂p − ω ∂q >0 ∂p − ω ∂q <0 ∂p − ω ∂q ≥0 ∂p GMS ~ 0 GMS < 0 GMS > 0 Climate Symposium 2014, Darmstadt Oct. 14, 2014 ω mode vertical h advection GMS > 0 GMS ~ 0 GMS < 0 Climate Symposium 2014, Darmstadt Oct. 14, 2014
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