SW o SOLAR
LW o OLR
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.
SW response
T response
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
SCARAB
GERB
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
STRUMENTI
•
•
•
•
•
ERB
ERBE
CERES (TRMM, AQUA, TERRA)
GERB (MET8, MET9)
SCARAB (RESURS, ADEOS, MEGHATROPIQUE)
• Calibrazione (intercalibrazione)
• Sampling diurno
• Calcolo del flusso a partire della radianza
(identificazione della scena)
Radiance-to-flux conversion
Radiance
TOA flux estimate
F(O )
L(O , , )
2  / 2
F(O) 
  L( 
O
, , ) cos  sin dd
SAT
0 0
O


Angular Dependence Model
(ADM)
Flux
L(O , , )
F(O , , ) 
R J (O , , )
with
R J (O , , ) 
2  / 2
L J (O , , )
  L( 
O
, , ) cos  sin dd
0 0
where
R J (O , , )
is the ADM for the ‘j’ scene
Clear-Sky Ocean CERES ADM
Low wind (0-3 m/s)
High wind (9-12 m/s)
Polar 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.



I (zt ;, )   B (0)T (zt ,0; ,  ) 
2
1
0
0
0
  
OLR 
N i ( ) 




i

zt
0
T (zt , z;, )
B (z)
dz
z

I (zt; ,  )ddd
I (zt , ) f i ( )d
  cos()
Equator Crossing Times for
NOAA Polar Orbiters
OLR:
Outgoing
LW
Radiation
Multi-spectral HIRS OLR Algorithm
Ellingson et al. (1989)
OLR  a0 ( )   ai ( ) N i ( )
i
ai=regression coefficients
=local zenith angle
T (zt , z;, )
I (zt ;, )   B (0)T (zt ,0; ,  )   B (z)
dz
0
z

2
1 
OLR     I (zt; ,  )ddd


0
N i ( ) 
0


zt

0

i
I (zt , ) f i ( )d
  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 cosθ
Sfc obs
Sat obs
SURF. RADAR
PREC. RADAR
CLOUD RADAR
LIDAR
lidar
Cloud radar
Precipitation
radar
ALTIMETER
scatterometer
Monitoraggio icebergs
SAR
Dipole 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.