Climate Modeling at GFDL: The Scientific Challenges V. Ramaswamy NOAA/ Geophysical Fluid Dynamics Laboratory November 12, 2008
Jan 02, 2016
Climate Modeling at GFDL:The Scientific Challenges
V. Ramaswamy
NOAA/ Geophysical Fluid Dynamics LaboratoryNovember 12, 2008
Be a world leader for the production of timely and reliable knowledge and assessments on natural climate variability and anthropogenic changes and in the development of the required earth system models.
Work cooperatively in NOAA to advance its expert assessments of changes in national and global climate through research, improved models, and products.
GFDL MissionDirectly supports the DOCAnd NOAA Strategic Goals
One of 2 Climate Modeling Centers called for in the US Climate Change Science Program [CCSP]
AM2,-----------
LM2, SIS,OM3
(MOM4)
AM3, LM3, SIS,OM3 (MOM4, GOLD)
2001-2004 2005 2006 2007
CM2.0 CM2.1
2008
AR4, WMO/UNEP
GFDL’s Recent Major Climate Model Developments
CCSPs, NARCCAP
B-grid FV core
FV, CS cores
Hi-resAM2
CM 2.4ESM 2.1w/ OM3{M,G}
CM3
Figure SPM.2
Figure SPM.4
Figure SPM.5
Figure SPM.6
Figure SPM.7
Anthro. RF > 0 (v. high conf.)
20th Cent. continental warminglikely due to human activity
Projected global warming
Projected patternof rainfall
changes in 21st Cent. Projected warming patternin early and late 21st Cent.
NOAA/ GFDLmodel simulations
contributed toIPCC AR4
AR4 conclusions
Global decreases in sulfate aerosolwarmer U.S. summers in 2100
CCSP 1.1
CCSP 3.2
(sfc - tropos): Models vs. Obs.
CCSP 2.4
CCSP 3.3
NOAA/ GFDL
contributionto
CCSPreports
OUTLINE
• Understanding present climate; quantifying the causal factors and attribution of past climate change; and projections of future climate changes.
• Challenges and progress in modeling the Atmosphere, Ocean, Coupled Atmosphere-Ocean, and Biosphere to address the key issues.
The World Has Warmed
Globally averaged, the planet is about 0.75°C warmer than it was in 1860, based upon dozens of high-quality long records using thermometers worldwide, including land and ocean.
Eleven of the last 12 years are among 12 warmest since 1850 in the global average.
Globally averaged, the planet is ~0.75°C warmer than it was in 1860, based upon dozens of high-quality long records, including land and ocean.
Eleven of the last 12 years are among 12 warmest since 1850 in the global average.
IPCC AR4
Nat = Natural ForcingAnth = Anthropogenic ForcingAllForc = (Nat + Anth) ForcingsCRU = Observations
GFDL Climate Model CM2.1
1950 2000
IPCC AR4 simulation
Sulfate AODoverestimated
(Europe)
AOD overestimated
(East coast)
Biomassemissions
underestimated(S Africa)
Biomassemissions
underestimated(S America)
AOD GFDL CM2.1 (1996-2000)
Aerosol Optical Depths from GFDL Coupled Model 2.1 (CM2.1), AVHRR, and MODIS
How might future changes in aerosols affect climate?
HISTORICAL and FUTURE SCENARIOS
CO2 concentrations
pp
mv
Emissions of Short-lived Gases and Aerosols (A1B)
1880 1920 1960 2000 2040 2080
NOx (Tg N yr-1)
SO2 (Tg SO2 yr-1)
BC (Tg C yr-1)25201510 5 0
250
200
150
100
50
605040302010
Horowitz, JGR, 2006
Large uncertainty in future emissiontrajectories for short-lived species
Pollution controls
A1B
IPCC, 2001
Up to 40% of U.S. warming in summer (2090s-2000s) from short-lived species
From changing well-mixed greenhouse gases +short-lived species
From changing only short-lived species
Warming from increases in BC + decreases in sulfate;depends critically on highly uncertain future emission trajectories
Results from GFDL Climate Model [Levy et al., 2008]
Change in Summer Temperature 2090s-2000s (°C)
New Science Questions for Next-Generation Model
• What are the roles of aerosol-cloud interactions in climate and climate change?
• How will land and ocean carbon cycles interact with climate change?
• To what extent is decadal prediction possible?
• What are the dominant chemistry-climate feedbacks?
Atmospheric Model Developments to Address the New Questions
• Interactive chemistry to link emissions to aerosol composition
• Aerosol activation requires super-saturation at cloud scale => Sub-grid PDFs of vertical velocity for convective and stratiform clouds
• Sufficiently realistic tropical land precipitation for land carbon model
• Stratospheric model for chemistry and links to troposphere, including those on multi-year scales relevant to decadal prediction
Model – satellite difference spectrum
Unit: W m-2OLR Window band
Total sky Clear sky Total sky Clear sky
CERES 241.73 275.87 66.94 83.28
GCM 240.63 263.43 73.99 87.56
GCM-CERES
-1.10 -12.44 7.05 4.28
OverestimationUnderestimation
H2O vib-rotWindow
[Huang et al. 2007 GRL]
Total-sky MODEL-AIRS radiance difference
Water vapor band radiance error budget
i
ii
i
iai
a
ss
OHOH
R
TT
R
TT
RR
22
Clean/Maritime
Polluted/Continental
Aerosol Indirect Effects (1st and 2nd)
Ramanathan et al. (2001)
Aerosol vs. Dynamics
T = 288 Kp = 850 hPaAerosol mass = { 0.5, 0.5, 0.5 } x 10-12 kg
CCN activation is a non-linear function of vertical velocity
from Ming et al. (2006,
JAS)
updraft: activation
downdraft: evaporation
~ 12.9 km
Large Eddy Simulation shows small-scale activation.
simulation by Chris Golaz