The Madden-Julian Oscillation - PowerPoint Presentation

Slide1

The Madden-Julian Oscillation

SO 442

–

Tropical Meteorology

Space and time-scales of dynamical atmospheric processes. SOURCE: UCAR

Climate

: PDO

Years

: ENSO

Seasons:

Monsoons

Months/Weeks:

MJO

Atmospheric Scales of Motion

MJO- an intraseasonal event

Prior to 1971, it was thought that virtually all variability in the weather conditions within a given season in the Tropics was random.

There were indications of

interseasonal

(

eg

, June vs. December) and

interannual

(

eg

, 2006 vs 2007)

variations

, such as ENSO

But studies of tropical rainfall and pressure changes tended not to focus on oscillations on other time periods

What is the MJO?

Large-scale disturbance of deep convection and winds that controls up to half of the variance of tropical convection in some regionsNow known to be a major propagator of weather systems

The Madden-Julian Oscillation (MJO)

Important features:Discovered in the 1960s by Dr. Roland Madden and Dr. Paul Julian of NCARConvectively coupled disturbance that propagates eastward across the Tropics 5-10 m s-1 propagation speed in the Indian and west Pacific, where MJO convective variability is strongly coupled to the large-scale flow.Simple baroclinic wind structure, with 850 hPa and 200 hPa wind perturbations 180o out of phaseCharacteristic timescales of 30-90 days.

Madden and Julian 1972

Univ of Munich Physics Dept

Climate of the extratropics & oceans

Newman, M., M. Alexander, T. R. Ault, K. M. Cobb, C.

Deser, E. Di Lorenzo, and e. al. (2016), The Pacific decadal oscillation, revisited, J. Clim., in press.

ENSO teleconnections (red), ocean waves (blue), atmospheric extratropical variability (orange), and the reemergence of temperature anomaly from below the mixed layer (green). With the exception of the reemergence and of the coastal waves, most of these processes impact the PDO by influencing changes in the Aleutian Low, which is the main driver of the PDO (grey). (CLIVAR, 2016).

MJO

Modified from:

The MJO - A Description

A 30-60 day oscillation in the coupled Tropical ocean-atmosphere systemAn eastward progression of enhanced and suppressed convectionLow level and upper level wind patterns show distinct anomaliesStrong year to year variability in MJO that is related to ENSO cycle

climate.gov

MJO is a very large scale oscillation (approximately 15,000 km east-west distance)

Centered on the equatorFeatures: one region of upward motion (favoring convection) and one region of downward motion (favoring drier conditions)

Note: in this graphic, the MJO is

not

one thunderstorm that covers an entire ocean. Such a thing doesn’t exist! Rather, in the region represented by the cloud, MJO favors the development of more thunderstorms than normal

MJO Structure in Outgoing Longwave Radiation (OLR): Indian Ocean and Western Pacific, Phases 1-8

convective anomaly subsidence anomaly

convective

component

subsidencecomponent

1

2

3

4

5

8

7

6

MJO couplet (one region of upward motion and one region of downward motion) moves eastward along the equator

Why does it move along the equator, and not off the equator?

MJO really is an “

equatorally

trapped” Kelvin wave

Coriolis force acts to trap the MJO wave along the equator

Over a 3-5 week period, the MJO convective couplet can transit the tropical eastern hemisphere

Univ of Washington Atmos Sci dept

NOAA Pacific Northwest Laboratory (PNL)

US

Dept

of Energy

More views of the MJO convective couplet – not just thunderstorms but also specific humidity and wind anomalies, too!

The passage of the MJO across the tropical oceans also shows up in SST anomalies

Background: MJO and Global Circulation

MJO impacts global atmospheric weather patterns on intraseasonal timescales via upper tropospheric teleconnections (Hoskins and Karoly, 1981; Sardeshmukh and Hoskins, 1988).

Figure

.

a)

300

mb height field response in to a heat source (shaded region simulating MJO convection) in a

barotropic

global model (Hoskins and

Karoly

JAS

, 1981).

b)

Theoretical equivalent barotropic

streamfunction

at 300 mb resulting from heat source (red oval) similar to the MJO (adapted from

Sardeshmukh

and Hoskins 1988).

MJO Cluster Structure

Jon Gottschalck, NOAA Climate Prediction Center

MJO Forecasting

Jon Gottschalck, NOAA Climate Prediction Center

MJO Forecasting

NOAA Climate Prediction Center

MJO teleconnections: linking the tropics to the high latitudes

One of the major elements of research in the Oceanography Department over the past 10 years has been to discover

subseasonal

variability of the atmosphere, ocean, and cryosphere

The Madden-Julian Oscillation is one of the most significant drivers of those teleconnections!

How does the MJO connect to the high latitudes?

Latent

heat

released

by

MJO

convection

excited

eastward

- and

poleward-propagating

Rossby

waves

Those

Rossby

waves

are

associated

with

high

and

low

pressure

,

which

controls

the

weather

(

wind

, temperatura,

precipitation

, and

cloud

)

patterns

all

around

the

world

!

MJO teleconnections

MJO convection over the Maritime Continent (MJO phases 4 & 5) drives a strong polar Jet stream and blocking high over the Gulf of AlaskaAs the MJO shifts east (phases 6-8), the Pacific Jet stream extends east, tooThat jet stream then advects copious amounts of water vapor and precipitation into the US west coastThe low can sometimes set up over the central Rocky Mountains and lead to severe weather (tornadoes and hail)