The Infinite Forecast

Ants Leetmaa and Gabriel VecchiGeophysical Fluid Dynamics Laboratory

NOAA/OARPrinceton, NJ 08542

The next logical step after the NWP (24 hrs) forecasting project is to pass to longer range forecasts, and more generally speaking, to determination of the ordinary general circulation of the terrestrial atmosphere …..may be viewed as a forecast over an infinite period of time

J. von Neumann

July 29, 1955

Weather • Current state of atmosphere• Deterministic, out to days in advance Seasonal Climate• Tropical ocean and land state• Probabilistic, next seasons of deviations from climatological* seasonal

meansDecadal to Centennial Projections• Changes in solar forcing, volcanoes, natural oscillations• Anthropogenic greenhouse gas – radiative forcing scenarios • Probabilistic, scenarios of future climatologies**Climatology – a statement of “normal”- typically averages over 30 years of

means, extremes, etc.Linkages exist between centennial – seasonal – weather regimes

Sources of Predictability

1st simulation of H2O, cloud-rad, ice-albedo feedbacks

1st 3-D sim of chem-transport-rad features of Antarctic ozone hole

GFDL Science and Computer Advances Volcanic aerosols and feedbacks on AO

Coupled ocean/atmos 100 yr run: 1st IPCC model

1st estimates of effects of 2xCO2

Coupled ENSO forecasts

Start detection & attribution; multiple GHG forcings; natural variability and forcings important; ensembles IPCC

2007

Climate Scenarios Being Run for 2007 IPCC

What can we learn from these about the slow and fast modes of climate variations?

Preliminary Results from IPCC 2007 Runs

Changes to general circulation• Hadley and Walker cells• Season mean

Impacts of change on climate variability – El Nino Southern Oscillation (ENSO)

Changes to Hadley and Walker Circulations

2x

1860

1860 Mean

4x minus 1860

% change

Slow down of tropical/subtropical circulations associated with redistributions of tropical rainfall

( 500 mb vertical velocity field)

2X

Changes in Mean Annual Cycle: DJF

Surface temperature

rainfall

Z200U200

Note the development of a zonally and hemispherically symmetric component to the circulation anomalies – with strong impacts in midlatitudes

Surface temperature

rainfall

Z200U200

The poleward expansion of the subtropical highs is most pronounced in fall and summer. 1860 relative to 1990 shows equatorward movement of highs.

Changes in Mean Annual Cycle: SON

Changes to Tropical Variability with Planetary Warming

reversed 1860 spinup 1990 CO2 CO2 increasing 1%/yr

NIN

O3

SST

Pow

er S

pect

rum

1

4

0.5

2

8

Increasing CO2

Period (yr)

135yr

NINO3 SST Spectrum

Period(years) 1860

1990

greenhouseobs

Changes to Spatial Structure and Amplitude of ENSO(As evidenced in 500 mb vertical velocity field)

2X

4X

Changes in Amplitude of ENSO Teleconnections: DJF

Summary – Physical ClimateA richness of tropical forced responses are important on a variety of time scales

Hadley and Walker cells slow down with global warming• Tropical convection becomes more zonally symmetric• Convective – radiative equilibrium might play role in slowing

Seasonal circulation patterns become more zonally symmetric• Subtropical highs expand northward (or southward)– especially summer/fall –

depending on warming (or cooling) of tropics• Midlatitudes experience greater drying tendencies with warming

ENSO temporal structure doesn’t change significantly• Suggestion of stronger and longer duration events with warming – predictability

possibly is greater• Increased chances of more “100 year” events• Teleconnection patterns are more robust with warming• Decadal variability of ENSO can confound warming signal and is important in

decadal midlatitude climate fluctuations (droughts, etc.)

atmosphere

Hyro-land

ocean

Sea ice

Land carbon

Ocean-carbon NPZ

Atmospheric chemistry

weather

Seasonal climate

Link to coastal ecosystem models

Earth System - prototype in 2005

NOAA – nowNatural disaster reduction

Improved seasonal & drought

Coastal runoff

NOAA – NextNatural disaster reduction

Water resources – weather and climate

Decadal fcsts

Sea Level

Arctic ice/climate

CO2 uptakes

Prototype coastal & ocean ecosystems

Local &Global air quality & dust

NOAA–after-NextNatural disaster reduction

Water quantity and quality

Marine ecosystem regime shifts

Ocean health

Energy & insurance management

Terrestrial ecoystem yields (crops)

Coastal blooms and hypoxia

Global chemistry & Climate and Health

NOAA’s Future Environmental Forecasts

Weather and Climate models built on community based software standards