Earth’s Radiation Budget: From Early Discoveries (Part 1) to Current Science Results and

Questions (Part 2)

by

Professor Thomas H. Vonder Haar

Colorado State University

AT 737 FA ‘12

October 29, 2012

Composite from NASA MODIS instrument

This system is operating at a level of 2.5 X 1015

joules/sec.

Or 2.5 Petawatts!

( ??)

10

EARTH’S Radiation “Budget”• Among important geophysical features we find “the

Radiant Energy Exchange among the Earth, the Sun and Space”

• It is called Earth’s Radiation Budget, where:– Incoming Energy = Outgoing Energy– π Re

2Hs (1.0-Ae) = 4 π Re2ЄeσTe

4 with• Hs = direct solar irradiance reaching Earth (w/m2)• Ae = planetary albedo (%)• Te = Earth’s effective radiating temperature (K)• Є e = Earth’s thermal emissivity (~1.0)• σ = Stefan-Boltzman Constant = 5.67x10-8(w/m2∙k2)• Re = Earth’s radius (km)

Note: Wer = AeπR2eHs = solar energy reflected and

scattered by Earth to Space

Studies of Earth’s Radiation Budget• Dines (1915)• Simpson, G.C. (1929), Mem. Roy. Soc.• Baur and Philips (1935), Gerlands Beitr. Geophys.• Lettau, H. (1954), Arkiv. Meteor., Geophys. und Bioklima• London, J. et al. (1957), Report, NYU--------------------------------------------------------Age of Artificial Earth Satellites 1957

-Vonder Haar, T. and V. Suomi (1969), Science-Vonder Haar, T. and V. Suomi (1971), J. Atmos. Sci.

More-Raschke, E., T.H. Vonder Haar, W.R Bandeen and M. Pasternak (1973), J. Atmos. Sci.--

Radiation Budget at the top of the Earth’s Atmosphere

The Amount and Space/Time Distribution of Earth Radiation Budget “Surplus” and “Deficit” at the Top-of-the-Atmosphere is the FUNDAMENTAL DRIVER of Earth’s Weather and Climate … and Earth’s Biosphere.

TIROS with the Suomi ERB sensors

“We found that Earth was a Warmer and Darker Planet than previously believed - - especially

in the Tropical Regions. We found that 40% More Energy

must be transported poleward by the Atmosphere and Ocean

Circulations!” (Vonder Haar and Suomi, 1969, 1971)

Much more energy gain in the tropics

Could these early results be true?

If so, there were far-reaching implications to better understand and model Atmospheric and Ocean Circulations; Air-Sea Interactions; and both the Earth’s Energy and Water Cycles!

The Nimbus 2 & 3 MRIR experiments and the Nimbus 6 & 7 ERB were designed to check, verify, and expand the results from the 1960’s.

So, Nimbus – 3 supports earlier satellite results!

warmer

darker

Global Physical Climatology, D.L. Hartmann, 1994, Academic Press

Vonder Haar, T.H., 1987: “Terrestrial Atmospheric Heat Balance”, McGraw-Hill Encyclopedia of Science and Technology. McGraw-Hill Book Company, 6, 413-414.

New knowledge of ERB at TOA helped understand estimates of other components of Earth’s energy balance.

ENSO

ENSO?

Nimbus provided first detailed studies of ERB VARIABILITY

(Randel and Vonder Haar, 1990)

Recent MeasurementsRecent Measurements

(Courtesy: Gary Rottman, CU)

Earth Radiation Budget Satellite (1984-Present)

-for more validation of early results

-for new variability and “cloud forcing” studies

ERBE fits Nimbus and thus the early ERB results from the 1960’s have been confirmed and greatly expanded during the 1970’s and 1980’s

Having measured – and twice replicated – the fundamental global Earth Radiation Budget provides an important point of closure for understanding Earth’s Climate System.

3 Current Science Questions about Earth’s Radiation Budget

• Can we detect any long-term trend of Radiation Budget at the “top-of-the-atmosphere” (TOA) in any or all of the 3 components?

• What are the mean values and variations of Radiative Energy throughout the vertical extent of the atmosphere – and at the surface?

• What is the impact of interannual variations of ERB at TOA on the large-scale circulation of the atmosphere and oceans?

From Wielicki et al, 2002: Evidence for large decadal variability in the Tropical mean radiative budget. Science, Vol. 295, p. 841- 844.

Note: The ERBE NS (designed at CSU) and the EBS Satellite (Ball Aerospace) provided ~ 20 years of ERB measurements!

Monthly variations of Global Net Radiative Gain and Loss by Earth. Note Interannual Variations

> + 3watt/m2 (or > +1 Petawatts)

Nimbus-7, Vonder Haar, 1989.

Kiehl and Trenberth, BAMS, 1997

??

(from detailed modeling)

The A-Train of research satellites

Does ERB at TOA affect – or indicate – variations of the internal circulations and oscillations of the atmosphere and oceans?

Do strong El Nino’s cool the Earth?G. Garrett Campbell and T.H. Vonder Haar

CIRA, CSUThe two strong El Nino events in the last 25 years have produced a pulse of long wave radiation which caused a decrease in “top-of-atmosphere” net radiation thus cooling the tropics. These unusual radiation budget observations from NIMBUS 7 and ERBS are a result of changes in

tropical clouds. The events also produce statistically significant “trends” in radiation or cloud amount, but the “trends” arise primarily from the single atmosphere-ocean, ENSO event in 1998,

not from a drift in the Earth’s climate.

Figure 1a Longwave flux: ERBS WFOV, CERES TRMM, Nimbus 7 ERB

20N to 0 anomalies from the seasonal cycle (W/m2).

Figure 1b Cloudiness ISCCP AVHRR corrected, HIRS, Nimbus 7 THIR: 20N to 0 anomalies from the seasonal cycle (%).

W/m2/year

Trend Uncertainty

Region Comment

ERBS LW 0.19 0.05 20oN – 0oN

ERBS LW 0.12 0.04 20oN – 0oN

Exclude 1997/12-1998/5

ERBS LW 0.20 0.04 20oN – 20oS

ERBS LW 0.18 0.03 20oN – 20oS

Exclude 1997/12-1998/5

ERBS+N7

-0.04 0.03 20oN – 20oS

Merged 1979 - 2000

%/year

ISCCP AV C

0.04 0.03 20oN – 0oN

ISCCP AV C

0.07 0.03 20oN – 0oN

Exclude 1997/12-1998/5

ISCCP AV C

0.04 0.02 20oN – 20oS

ISCCP AV C

0.04 0.02 20oN – 20oS

Exclude 1997/12-1998/5

Table 1: Trend from 1/1985 to 12/1999 of LWF or cloud amount for tropical regions.

Zonal KE

Eddy KE

Zonal APE

Eddy APE

Dissipation

Dissipation

Solar Energy

IR Energy

GAPE

Zonal KE

Eddy KE

Zonal APE

Eddy APE

Dissipation

Dissipation

Solar Energy

IR Energy

GAPE

Depiction of role of CloudSat-derived diabatic radiative heating processes (red) within overall energetics of the atmosphere, showing processes of conversion and dissipation.

The generation of mean available potential energy (PM) is given by:

dmQQPG M )])([]([)( Vertical cross-section of cloud-induced heating (units 0.1oC / day, negative areas shaded) averaged over the latitudinal belt from 30oN to 10oS; summer, 1988 (from Sohn, 1999).

The generation of eddy available potential energy is given by:

dmQPG E *]*[)(

Generation of Available Potential Energy (GAPE) in the Atmosphere

GAPE = f (T,Q)

Weather = f (GAPE KE)

Interannual variations in poleward atmospheric energy transports are seen from observations and models

(Whitmeyer and Vonder Haar, J. of Climate, 1994)

Variations in Earth’s Radiation Budget at Regional and Zonal Scales (due to variation of cloud, aerosol or surface features) may:

a) affect the “fast” (atmospheric) portions of the Earth’s Circulation Systems via Generation of Available Potential Energy (GAPE)

b) affect the “slow” (oceanic) portions of the circulation by adding to the “external” forcing of such features as the Atlantic Multi-Decadal Oscillation via Ocean Energy Content changes.

Having measured – and twice replicated – the fundamental global Earth Radiation Budget provides an important point of closure for understanding Earth’s Climate System.

Does ERB at TOA affect – or indicate – variations of the internal circulations and oscillations of the atmosphere and oceans?

Preliminary results favor further observations and analyses.

Summary

Hypothesis:

The Fundamental Atmospheric/Oceanic “Heat Engine” Does Not Operate at a Constant Rate of Energy/Time.

If True, what are the consequences?

Composite from NASA MODIS instrument

This system is operating at a level of 2.5 X 1015

joules/sec.

Or 2.5 Petawatts!

( ??)

10

Back-up slides

Schematic of the THC in Atlantic

1860 1900 1940 1980 2020

Adapted from Goldenberg et al. (2001)

by Klotzbach, CSU

A multidecadal (50-70 year timescale) pattern of North Atlantic ocean-atmosphere variability whose existence has been argued for based on statistical analyses of observational and proxy climate data, and coupled Atmospheric-Ocean General Circulation Model (AOGCM) simulations.

Atlantic Multidecadal Oscillation

Why does the AMO change sign?

• Primarily driven by North Atlantic Oscillation (NAO) feedbacks?

• Primarily driven by changes in freshwater fluxes in the tropical Atlantic?

• Primarily driven by changes in ocean dynamic height topography in the North Atlantic?

Explorer 7 loop