detection of equatorial waves in data. olr power spectrum, 1979–2001 (symmetric) from wheeler and...

Detection of Equatorial Waves in Data

OLR power spectrum, 1979–2001 (Symmetric)

fromWheeler and Kiladis, 1999

Space-Time Spectrum of JJA Symmetric OLR, 15S-15N

Wheeler and Kiladis, 1999

Kelvin

MJO

“TD” band

Eq. Rossby

Space-Time Spectrum of JJA Antisymmetric OLR, 15S-15N


Inertio-Gravity

MJO

“TD” band

Space-Time Spectrum of JJA Antisymmetric OLR, 15S-15N


2002 CLAUS Brightness Temperature 5ºS-5º N

Vertical Structure of Equatorial Waves

C W C W

Direction of Motion

Temperature Structure of a Dry Kelvin Wave

Temperature at Majuro (7N, 171E) Regressed against Kelvin-filtered OLR

(scaled -40 W m2) for 1979-1999

OLR (top, Wm-2)Temperature (contours, .1 °C),

red positive

from Straub and Kiladis 2002


(scaled -40 W m2) for 1979-1999


red positive


Wave Motion

is the equivalent depth

where

€

m ≡2π

Lz=N 2

gh−

1

4H 2

⎛

⎝ ⎜

⎞

⎠ ⎟

1/2

€

h

€

m

€

Lz

€

H

is the vertical wavenumber

is the vertical wavelength

is the scale height

Linear Theory Predicts:

Using Representative Numbers for the Tropical Stratosphere:

for h=200 m, c=45 m/s, Lz=12.0 km

“Peak Projection Response”

for h=30 m, c=15 m/s, Lz=4.0 km


for h=200 m, c=45 m/s, Lz=12.0 km

“Peak Projection Response”Convectively coupled Kelvin

for h=30 m, c=15 m/s, Lz=4.0 kmfor c=5 m/s, Lz=1.2 km


for h=200 m, c=45 m/s, Lz=12.0 km

“Peak Projection Response”Convectively coupled Kelvin

MJO

Zonal Wind at Majuro (7N, 171E) Regressed against Kelvin-filtered OLR

(scaled -40 W m2) for 1979-1999

OLR (top, Wm-2)Zonal Wind (contours, .25 m s-

1), red positive



(scaled -40 W m2) for 1979-1999


red positive


Wave Motion

Specific Humidity at Majuro (7N, 171E) Regressed against Kelvin-filtered OLR

(scaled -40 W m2) for 1979-1999

from Straub and Kiladis 2002OLR (top, Wm-2)

Specific Humidity (contours, 1 X 10-1 g kg-1), red positive

Wave Motion

Haertel and Kiladis 2004

TOGA COARE Temperature (2S, 155E) Regressed against Westward Inertio Gravity-filtered OLR (scaled -40 W m2)

Temperature (contours, .1 °C), red positive

Wave Motion


TOGA COARE Specific Humidity (2S, 155E) Regressed against Westward

Inertio Gravity-filtered OLR (scaled -40 W m2)

Specific Humidity (contours, 1 X 10-1 g kg-1), red +

Wave Motion

OLR and 850 hPa Flow Regressed against MJO-filtered OLR (scaled -40 W m2) at eq, 155E,

1979-1993

Day 0Streamfunction (contours 4 X 105

m2 s-1)Wind (vectors, largest around 2 m

s-1)OLR (shading starts at +/- 6 W s-

2), negative blue

from Kiladis et al. 2005


1979-1993

Day-16Streamfunction (contours 4 X 105



2), negative blue


1979-1993




2), negative blue


1979-1993

Day 0Streamfunction (contours 4 X 105



2), negative blue


1979-1993

Day+4Streamfunction (contours 4 X 105



2), negative blue


1979-1993




2), negative blue

Zonal Wind at Honiara (10S, 160E) Regressed against MJO-filtered OLR (scaled -40 W m2) for

1979-1999

OLR (top, Wm-2)U Wind (contours, .5 m s-1),

red positive

OLR

Pressure(hPa)


Wave Motion

Temperature at Honiara (10S, 160.0E) Regressed against MJO-filtered OLR (scaled -40 W m2) for

1979-1999


red positive

OLR

Pressure(hPa)


Wave Motion

Specific Humidity at Truk (7.5N, 152.5E) Regressed against MJO-filtered OLR (scaled -40 W

m2) for 1979-1999

OLR (top, Wm-2)Specific Humidity (contours, 1 X 10-1 g

kg-1), red positive

OLR

Pressure(hPa)


Wave Motion

from Mapes et al. 2006

Lag-height regressions of OSA specific humidity vs. moisture budget-derived rainrate. The data are progressively regridded to coarser time intervals ((a) 6 h, (b) 1 day, and (c) 4 days), and a light high-pass filter is used for each panel (cutoff period six times the lag window width). (d) The original unfiltered 6 h data are used, with a very wide lag window. Contour unit is 0.1 g/kg per mm/h.

Conclusion 2: A portion of tropical convective activity is organized by equatorially trapped waves of Matsuno’s shallow water theory

Conclusion 1: Large scale atmospheric waves modulate waves and convection (along with the diurnal cycle) on smaller scales

Conclusion 2: A portion of tropical convective activity is organized by equatorially trapped waves of Matsuno’s shallow water theoryConclusion 3: Equatorial waves have a warm lower troposphere ahead of the wave, with cooling behind. The mid-troposphere is warm within the convective region




Conclusion 4: Low level moisture is high ahead of the waves (high CAPE) and is lofted rapidly into the mid-troposphere as deep convection develops, with drying occurring at low levels first while it is still moist aloft behind the waves


TOGA COARE Diabatic Heating Q1 (2S, 155E) Regressed against Westward

Inertio Gravity-filtered OLR (scaled -40 W m2)

Diabatic Heating (contours, °K/day), red +

Wave MotionWave Motion

Radar Derived Divergence and Omega Regressed against Rain Rate

from Mapes et al. 2006

Regression composite of the MCS life cycle in divergence and vertical motion. Plotted are averages of regressionsections from seven tropical radar deployments (see Mapes and Lin, 2005 for details). (a) VAD divergence regressed against rainrate for a circular area of 96 km diameter, contour unit 10−6 s−1 per mm/h. (b) The corresponding mass flux (pressure units, but with positive sign indicating upward motion), contour unit 10 h Pa/day per mm/h.

Q1 Regressed against MJO-filtered OLR over the IFA during COARE


Morphology of a Tropical Mesoscale Convective Complex in the eastern Atlantic during GATE

(from Zipser et al. 1981)Storm Motion

Observed Kelvin wave morphology (from Straub and Kiladis 2003)

Wave Motion

Two day (WIG) wave cloud morphology (from Takayabu et al. 1996)

Wave Motion

from Benedict and Randall, 2007

MJO Propagation

from Kiladis et al., 2009

Generalized Evolution of a Convectively Coupled Equatorial Wave



Conclusion 4: Low level moisture is high ahead of the waves (high CAPE) and is lofted rapidly into the mid-troposphere as deep convection develops, with drying occurring at low levels first while it is still moist aloft behind the waves



Conclusion 4: Low level moisture is high ahead of the waves (high CAPE) and is lofted rapidly into the mid-troposphere as deep convection develops, with drying occurring at low levels first while it is still moist aloft behind the waves Conclusion 5: Equatorial wave cloud morphology is consistent with a progression from shallow to deep convection, followed by stratiform rain during the passage of the wave

Summary and QuestionSummary and Question

All waves examined have broadly self-similar vertical structures in terms of their dynamical fields (temperature, wind, pressure, diabatic heating, cloud morphology)

This is consistent with a progression of shallow to deep convection, followed by stratiform precipitation from the mesoscale on up to the MJO

Suggests a fundamental interaction between wave dynamics and convection across a wide range of scales


This is consistent with a progression of shallow to deep convection, followed by stratiform precipitation from the mesoscale on up to the MJO



This is consistent with a progression of shallow to congestus and then deep convection, followed by stratiform precipitation from the mesoscale on up to the MJO


Is a systematic cascade of energy from the mesoscale on up to the planetary scale crucial for the maintenance of equatorial waves?


This is consistent with a progression of shallow to congestus and then deep convection, followed by stratiform precipitation from the mesoscale on up to the MJO


Is a systematic cascade of energy from the mesoscale on up to the planetary scale crucial for the maintenance of equatorial waves?

Summary and QuestionSummary and Question

Convection in General Circulation Models

Question: How well do GCMs do in characterizing intraseasonal tropical convective variability?

Jialin Lin et al. (2006) applied identical space-time spectral techniques to observed and modeled tropical precipitation

Models used are the 14 coupled ocean-atmosphere GCMs used for intercomparison in the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC)

Rainfall Power Spectra, IPCC AR4 Intercomparison 15S-15N, (Symmetric)

from Lin et al., 2006

Observations

Rainfall Power Spectra, IPCC AR4 Intercomparison 15S-15N, (Symmetric)


Rainfall Spectra/Backgr, IPCC AR4 Intercomparison 15S-15N, (Symmetric)


Observations


Rainfall Spectra/Backgr, IPCC AR4 Intercomparison 15S-15N, (Symmetric)

Rainfall Spectra/Backgr., IPCC AR4 Intercomparison 15S-15N, (Antisymm.)


Observations

Rainfall Spectra/Backgr., IPCC AR4 Intercomparison 15S-15N, (Antisymm.)


Rainfall Spectra at 5S-5N, 85E from IPCC AR4 Intercomparison

Models with good KW variability

CCSR, Japan

GISS-AOM, USA

GISS-EH, USA

GISS-ER, USA

Observed KWs: Upper troposphere

• Divergence collocated with/to the west of lowest OLR

• Zonal winds near equator• Rotational circulations off of equator

OLR (shading); ECMWF 200-hPa u, v (vectors), streamfunction (contours)

Model KWs: Upper troposphere

MIUB

MPI

MRI

Precipitation (shading); 200-hPa u, v (vectors); streamfunction (contours)


(scaled -40 W m2) for 1979-1999


red positive


Wave Motion

Model KWs: Vertical structure, T

MIUB MPI

MRI

Specific Humidity at Majuro (7N, 171E) Regressed against Kelvin-filtered OLR

(scaled -40 W m2) for 1979-1999

from Straub and Kiladis 2002OLR (top, Wm-2)

Specific Humidity (contours, 1 X 10-1 g kg-1), red positive

Wave Motion

Model KWs: Vertical structure, q

MIUB MPI

MRI

Outstanding Issues

General Circulation Models do a relatively poor job in correctly simulating variability in tropical convection (but not necessarily its mean state)

Is this due to the misrepresentation of convection itself, or its coupling to the large scale (or both)?

Is convection even parameterizable in models?

Improvements in the representation of tropical convection will lead to improvements in medium-range weather forecasts in mid-latitudes (and perhaps to ENSO) What is the impact of poor tropical variability in GCMs on climate change scenarios?

detection of equatorial waves in data. olr power spectrum, 1979–2001 (symmetric) from wheeler and...

Documents

kelvin slide

rossby slide

data slide

kelvin mjo slide

red wave motion slide

dry kelvin wave slide

red positive wave motion

kelvinfiltered olr