Influence of Clouds and Aerosols on the
Earth’s Radiation Budget Using Clouds
and the Earth’s Radiant Energy System
(CERES) Measurements
Norman G. Loeb
Hampton University/NASA Langley Research Center
Bruce A. Wielicki
NASA Langley Research Center, Hampton, VA
December 5, 2003
Global Radiation Budget
-10
Indirect Aerosol
Forcing
Land Albedo
Direct Anthropogenic
Aerosol Forcing
-20
Cloud Optical
Depth
Earth
Cooling
Particle Size
(Low Clouds)
Cloud
Height
High Cloud
Amount
Earth
Warming
10
Carbon
Dioxide
Stratospheric
Ozone
Radiative
0
Effect
(W/m2)
Low Cloud
Amount
Climate Sensitivity
Radiative Effect at the Top of the Atmosphere
For a 50% Increase in Climate Parameter
20
Clear-sky and Cloud Sensitivity From 19 GCMs
Climate models are inconsistent in predicting the
effects of clouds on climate.
5.6
All Sky
Clear Sky
1.2
4.8
1.0
4.0
0.8
3.2
0.6
2.4
0.4
1.6
0.2
1 2
3 4 5
6 7
8 9 10 11 12 13 14 15 16 17 18 19
Temperature (K)
Sensitivity Parameter
1.4
0.8
Model Number
(Cess et al., 1990)
CERES Objectives
(1) For climate change analysis, provide a continuation of the
ERBE record of radiative fluxes at the top of the atmosphere
(TOA), analyzed using the same algorithms that produced the
ERBE data.
(2) Double the accuracy of estimates of radiative fluxes at TOA
and the Earth's surface.
(3) Provide cloud property estimates that are consistent with the
radiative fluxes from surface to TOA.
(4) Provide the first long-term global estimates of the radiative
fluxes within the Earth's atmosphere.
CERES Instrument
• 5 instruments on 3 satellites (TRMM, Terra,
Aqua) for diurnal and angular sampling.
• Narrow field-of-view scanning radiometer with
nadir footprint size of 10 km (TRMM); 20 km
(Terra & Aqua).
• Measures radiances in 0.3-5 µm, 0.3-200 µm
and 8-12 µm.
• Capable of scanning in several azimuth plane scan modes:
fixed (FAP) or crosstrack, rotating azimuth plane (RAP),
programmable (PAP).
• Coincident Cloud and Aerosol Properties from
MODIS/VIRS
2.5
2.0
Terra/Flight Model 1
Lifetime Radiometric Stability
Determined with the Internal Calibration Module
Normalized to Ground
Calibration Data
1.5
Absolute
Calibration:
0.5% LW
1% SW
1% Window
1.0
0.5
0.0
-0.5
Feb-00 Aug-00 Feb-01 Aug-01 Feb-02 Aug-02 Feb-03
DATE
Stability Goal:
better than
0.5% per
5 years
While changes accounted for in CERES processing, ideal
situation is change < 0.1% per mission.
An overlapping Earth radiation climate record:
22 years from Nimbus 7 to Terra.
Jan/Feb 98 El Nino TOA LW Flux Anomalies
(relative to ERBE 1985-1989 average)
CERES ERBE-Like LW Flux Observations
NOAA GFDL Standard Climate Model
NOAA GFDL Experimental Prediction Model
uses CERES data only
Aerosol
3-hourly 1-degree grid
CERES is a Sensor Web: up to
11 instruments on 7 spacecraft
all integrated to obtain climate
accuracy in top to bottom fluxes
CERES Single Scanner Footprint (SSF) Product
- Coincident CERES radiances and imager-based cloud and aerosol
properties.
- Use VIRS (TRMM) or MODIS (Terra, Aqua) to determine following
parameters in up to 2 cloud layers over every CERES FOV:
Macrophysical: Fractional coverage, Height, Radiating Temperature, Pressure
Microphysical : Phase, Optical Depth, Particle Size, Water Path
Clear Area
: Albedo, Skin Temperature, Aerosol optical depth, Emissivity
Layer 2
VIRS/MODIS
Imager
Pixel
Layer 1
Clear
CERES Footprint
CERES Footprint
Instantaneous TOA Flux Error by Cloud Property
Estimated Instantaneous TOA Flux Error
Region
So
Terra ADMs
TRMM ADMs
(W m-2)
W m-2
(%)
W m-2
(%)
Tropics 1150
Midlat
870
Polar
540
Clear
5.2
(2.2)
4.2
(3.0)
12.8
(4.3)
All-sky
14.3
(5.1)
13.5
(3.9)
17.3
(5.9)
Clear
7.7
(3.5)
7.3
(5.6)
37.0
(11.7)
All-sky
14.3
(5.8)
13.7
(4.1)
29.2
(9.8)
Cloud Radiative Forcing By Cloud Type
Cloud Forcing by Cloud Type
Single-Layer Low
-
Effective Cloud
Top Pressure
(mb)
> 680
Single-Layer Mid-Level
-
680 - 440
Single-Layer High
-
< 440
-Lower layer liquid
water
-Upper layer ice
-
Cloud Type
Multilayer Cloud
Phase
Net CRF Contribution by Cloud Type
Low
DECEMBER, 2001
High
Mid-Level
Multilayer
(W m-2)
Cloud Forcing By Effective Cloud Top Pressure and Optical Depth (Dec 2001)
Cloud Forcing By Effective Cloud Top Pressure and Optical Depth (June 2001)
Summary
- CERES provides a unique dataset for studying the influence of
clouds and aerosols on the Earth’s radiation budget:
i) Measurement stability to better than 0.5% for monitoring
radiative flux changes.
ii) Combined radiative fluxes, cloud and aerosol properties for
climate model validation and process studies.
iii) Improved TOA flux accuracy by a factor of 2-5 over previous
radiation budget datasets => Can now quantify how
different cloud types influence the Earth’s radiation budget.
- New Global Radiation Budget (surface and TOA) for 3 years of
Terra data released to the climate community by April 2004.
Future:
• Combine CERES+MISR to study radiative effect of clouds at
different spatial scales.
• Merge measurements from CERES & MODIS (Aqua) with
CALIPSO, CloudSat, PARASOL. Improved radiative forcing
estimates, especially for thin and multilayer clouds, aerosols.
• Climate model use of global datasets, comparisons between
models and observations.