SW o SOLAR LW o OLR

SW response

T response

ScaRaB = SW and LW broadband radiometer measuring the whole spectral ranges of the solar reflected radiation (SW), and of the longwave (LW) emission from the surface and atmosphere.

OLR History • First measurements of OLR as early as 1959

from Explorer-7 • Experiments - ERB, ERBE, ScaRaB, CERES,

GERB • First routine measurements of  OLR from

operational satellites began in 1974 – NOAA scanning radiometer ( SR)- window channel

( 10-12 microns) – Linear algorithm between window radiances and total

OLR – based on radiative calculations with model atmospheres

– Evolved a few years later to a non linear algorithm which is still in use today - adjusted for different spectral interval

• SR data 1974-1978, AVHRR 1979-onward  

CHANNEL Description Spectral Interval Filter

1 Visible (VIS) 0,55 — 0,65 µm Interferential

2 Solar or SW 0,2 — 4 µm Silice Filter

3 Total (T) 0,2 — 100 µm No filter

4 Infrared window (IRW) 10,5 — 12,5 µm Interferential

GERB

SCARAB

STRUMENTI

• ERB

• ERBE

• CERES (TRMM, AQUA, TERRA)

• GERB (MET8, MET9)

• SCARAB (RESURS, ADEOS, MEGHA-TROPIQUE)

• Calibrazione (intercalibrazione)

• Sampling diurno

• Calcolo del flusso a partire della radianza (identificazione della scena)

Radiance-to-flux conversionRadiance TOA flux estimate

ddsincos),,(L)(F O

2

0

2/

0

O

),,(L O )(F O

O

SAT

Angular Dependence Model (ADM)

ddsincos),,(L

),,(L),,(R

O

2

0

2/

0

OJOJ

),,(R

),,(L),,(F

OJ

OO

Flux

with

),,(R OJ where is the ADM for the ‘j’ scene

Clear-Sky Ocean CERES ADMPolar plots for the SW clear-sky ADMs at the 0°-25° SZA bin. Radii represent the VZAs and polar angles represent the AZMs. Sun is located at the 180° AZM.

Low wind (0-3 m/s)

High wind (9-12 m/s)

OLR I (zt;,)ddd

0

10

20

I (zt ;,)

B (0)T (zt ,0;,) B ( z )

T (zt , z ;,)

z d z

0

zt

N i() I (zt ,) f i( )d

i

cos()

Equator Crossing Times for NOAA Polar Orbiters

OLR: Outgoing

LW Radiation

Multi-spectral HIRS OLR Algorithm

ai=regression coefficients=local zenith angle

Ellingson et al. (1989)

OLRa0() ai()N ii

()

OLR I (zt;,)ddd

0

10

20

I (zt ;,)

B (0)T (zt ,0;,) B ( z )

T (zt , z ;,)

z d z

0

zt

N i() I (zt ,) f i( )d

i

cos()

HIS OLR Regression Model

• Channels and spectral intervals – stepwise regression based on 1600 Phillips soundings and radiation transfer model

HIRS Channel Wavelength (μm) Atmos Sensitivity

H7 13.1-13.6 Near Sfc temp

H10 7.8 – 8.5 Lower trop water vapor

H12 6.6-6.9 Upper trop water vapor

H3 14.3-14.7 Air temp- at 100mb

OLR

+ Long ‘consistent’ time series

+ 4 times/day

- Assumptions on remaining part of the LW spectrum

- No equivalent product for SW

Clear-sky OLR Anomaly (Jan 1998)

AVHRR OLR lacks sensitivity to water vapor variation, especially the upper tropo. humidity (UTH).

SW LW

Fo cosθSfc obsSat obs

LID

AR

CLO

UD

RA

DA

R

PR

EC

. R

AD

AR

SU

RF

. R

AD

AR

lidar

Cloud radar

Precipitation radar

ALTIMETER

scatterometer

Monitoraggio icebergs

SARDipole eddies in Sarichef Strait, which separates Hall and St. Matthew islands, Bering Sea, Alaska, were captured by the ERS-1 satellite in February 1992. The individual eddies have diameters of 5 to 9 km with tails of 12 to 19 km. The eddies were tidally generated, and the tidal amplitude was high at the time of the imaging. The eddies were observed only when frazil and grease ice acted as tracers.