TROPICAL REGIONALTROPICAL REGIONALPRECIPITATION ANOMALIES:PRECIPITATION ANOMALIES:Global warming and El Global warming and El NiNiñoo casescasesJ. David J. David NeelinNeelin**, , HuiHui SuSu** and and ChiaChia ChouChou****

*Dept. of Atmospheric Sciences & Inst. of Geophysics and Planetary Physics, U.C.L.A.,

**Inst. of Earth Sciences, Academia Sinica, Taiwan

• Tropical regional precipitation anomalies associated with changes in deep convection zones: including drought regions in global warming case; mechanisms?; any similarities in El Niño case?

• Intermediate complexity climate model QTCM (Quasi-equilibrium Tropical Circulation Model)www.atmos.ucla.edu/~csi

Observed anomalies during JulyObserved anomalies during July--Nov 1997Nov 1997

Precipitation(mm/day)

TroposphericTemperature

QTCM anomalies forced by Pacific positive SST QTCM anomalies forced by Pacific positive SST anomalies Julyanomalies July--Nov 1997Nov 1997

Precipitation(mm/day)

TroposphericTemperature

QTCM JulyQTCM July--Nov 1997: Anomaly budget contributionsNov 1997: Anomaly budget contributions11

Moisture convergence

Mq∇·v(by divergent flow)

Moist staticenergy

divergence*

M∇·v

* Gross moist stability M=Ms–Mq is an effective stability that includespartial cancellation of adiabatic cooling by diabatic heating

QTCM JulyQTCM July--Nov 1997: Anomaly budget contributionsNov 1997: Anomaly budget contributions22

Radiative cooling anom. (top of

atmosphere) due to temp. anom.

Mean wind advection of

moisture anomalyv·∇q'

ENSO ENSO teleconnectionsteleconnections to regional to regional precipprecip. anomalies. anomalies

ENSO ENSO teleconnectionsteleconnections to regional to regional precipprecip. anomalies. anomalies

• a small zoo of mechanisms with moist convective and cloud radiative feedbacks

QTCM experiments suppressing various mechanismsQTCM experiments suppressing various mechanismsPrecipitation Anomalies

Control

Anomaly ( )' term suppressed in region:

(v · ∇q)'

T' contribution toCAPE

GCM GCM PrecipPrecip. . AnomAnom. Dec. Dec--FebFeb

Global warming case precipitation anom.

Greenhouse gas scenarios for

2070-2090rel. to 1961-1990 clim

QTCM doubled COQTCM doubled CO22 experimentsexperimentsQfluxQflux mixedmixed--layer oceanlayer ocean

Dec - Feb Precip change

Dec - Feb QTCM Precip

climatology

QTCM doubled COQTCM doubled CO22 experimentsexperimentsMoisture budget contributionsMoisture budget contributions11

Mq' ∇·v

Anomalous moisture convergence due to

moisture anom. q'

(v·∇q)'

Anomalous moisture advection

QTCM doubled COQTCM doubled CO22 experimentsexperimentsMoisture budget contributionsMoisture budget contributions22

Mq ∇·v'

Anomalous moisture convergence due to

anomalous divergence (feedback)

The “uppedThe “upped--ante” mechanismante” mechanism11

Margin of convective zone with v inward

from dry region

The “uppedThe “upped--ante” mechanismante” mechanism22

Margin of convective zone with v inward

from dry region

Anomalous Gross Moist Stability (MAnomalous Gross Moist Stability (M'') mechanism) mechanism

• Moist static energy transport by divergent flow ≈ M∇·v• M =Ms-Mq

• M∇·v' + M'∇·v = F'net - (v·∇q)' + …

• P' ≈ ∇·v(-M')

• Mechanism increases convergence & precip. in strong convergence zones: “rich-get-richer”

may partially compensate if cloud top risesincreases with increasing moisture, tends to reduce M

increases to compensatereduced

MMq

QTCM 2xCOQTCM 2xCO22 ExptExpt. suppressing change in . suppressing change in moisture advectionmoisture advection

(testing the upped-ante mechanism)

Experiment2xCO2 Precip. change

(mm/day)

Control2xCO2 Precip. change

QTCM 2xCOQTCM 2xCO22 ExptExpt. suppressing change in gross . suppressing change in gross moist stability, Mmoist stability, M

(testing the M' mechanism)

Experiment2xCO2 Precip. change

(mm/day)

Control2xCO2 Precip. change

SummarySummary• analysis of tropical regional precipitation anomalies in ENSO

teleconnection case ⇒ a handful of contributing mechanisms• 2XCO2 case, mixed-layer ocean case ⇒ set of mechanisms with

some cross-over to ENSO case• the "upped-ante mechanism":

contributes substantial negative precipitation anomalyregions in both casesdrought occurs at margins of convection zones with

climatological wind inflow from dry zone into convection zone• the "anomalous gross moist stability (M') mechanism":

contributes positive precipitation changes in strong precipitation regions in global warming case (rich-get-richer)but theory for M' is very poor

• caveat Tropical mean precipitation anomaly mechanisms appear to differ between ENSO and global warming cases

SummarySummary• analysis of tropical regional precipitation anomalies in ENSO

teleconnection case ⇒ a handful of contributing mechanisms• 2XCO2 case, mixed-layer ocean case ⇒ set of mechanisms with

some cross-over to ENSO case• the "upped-ante mechanism":

contributes substantial negative precipitation anomalyregions in both casesdrought occurs at margins of convection zones with

climatological wind inflow from dry zone into convection zone• the "anomalous gross moist stability (M') mechanism":

contributes positive precipitation changes in strong precipitation regions in global warming case (rich-get-richer)but theory for M' is very poor

• caveat Tropical mean precipitation anomaly mechanisms appear to differ between ENSO and global warming cases

MOIST DYNAMICAL FEEDBACKS INMOIST DYNAMICAL FEEDBACKS INTROPICAL CLIMATE SENSITIVITY:TROPICAL CLIMATE SENSITIVITY:

ENSO vs. Global warmingENSO vs. Global warmingJ. David J. David NeelinNeelin**, , HuiHui SuSu** and and ChiaChia ChouChou****

*Dept. of Atmospheric Sciences & Inst. of Geophysics and Planetary Physics, U.C.L.A.,

**Inst. of Earth Sciences, Academia Sinica, Taiwan

• Tropical regional precipitation changes associated with shifts of or anomalies within deep convection zones: mechanisms for ENSO case; any similarities in global change case?

• Intermediate complexity climate model QTCM (Quasi-equilibrium Tropical Circulation Model)www.atmos.ucla.edu/~csi

TROPICAL PRECIPITATION ANOMALIES:TROPICAL PRECIPITATION ANOMALIES:ENSO TELECONNECTIONS VS.ENSO TELECONNECTIONS VS.

GLOBAL WARMINGGLOBAL WARMINGJ. David J. David NeelinNeelin**, , HuiHui SuSu** and and ChiaChia ChouChou****

*Dept. of Atmospheric Sciences & Inst. of Geophysics and Planetary Physics, U.C.L.A.,

**Inst. of Earth Sciences, Academia Sinica, Taiwan

• Tropical regional precipitation changes associated with shifts of or anomalies within deep convection zones: any similarity of mechanisms for ENSO and global change cases?

• Intermediate complexity climate model QTCM (Quasi-equilibrium Tropical Circulation Model)

www.atmos.ucla.edu/~csi