summary of spectral signatures labs in bertinoro 23 aug – 2 sep 2004 paul menzel noaa/nesdis/ora
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Summary of Spectral Signatures Labs in Bertinoro 23 Aug – 2 Sep 2004 Paul Menzel NOAA/NESDIS/ORA. Solar (visible) and Earth emitted (infrared) energy. Incoming solar radiation (mostly visible) drives the earth-atmosphere (which emits infrared). - PowerPoint PPT PresentationTRANSCRIPT
SummarySummaryof Spectral Signaturesof Spectral Signatures
Labs in Bertinoro Labs in Bertinoro 23 Aug – 2 Sep 200423 Aug – 2 Sep 2004
Paul MenzelPaul MenzelNOAA/NESDIS/ORANOAA/NESDIS/ORA
Incoming solar radiation (mostly visible) drives the earth-atmosphere (which emits infrared).
Over the annual cycle, the incoming solar energy that makes it to the earth surface (about 50 %) is balanced by the outgoing thermal infrared energy emitted through the atmosphere.
The atmosphere transmits, absorbs (by H2O, O2, O3, dust) reflects (by clouds), and scatters (by aerosols) incoming visible; the earth surface absorbs and reflects the transmitted visible. Atmospheric H2O, CO2, and O3 selectively transmit or absorb the outgoing infrared radiation. The outgoing microwave is primarily affected by H2O and O2.
Solar (visible) and Earth emitted (infrared) energy
Solar SpectrumSolar Spectrum
VIIRS, MODIS, FY-1C, AVHRR
H2O
H2OH2O
H2O
O2
CO2
CO2
H2O
O2H2O
O2
MODIS IR Spectral Bands
MODIS
GOES Sounder Spectral Bands: 14.7 to 3.7 um and vis
II II I |I I ATMS Spectral Regions
MODIS
00.5
11.5
22.5
33.5
44.5
5
8.5
8.7
8.91
9.13
9.36 9.6
9.86
10.1
10.4
10.7 11
11.4
11.7
12.1
12.5 13
13.4
13.9
wavelength
Refle
ctio
n [%
]
Ice reflectance
High ice cld
Midlevel cldLow water cld
Midlevel cld
0.0
0.2
0.3
0.5
0.6
0.8
0.0 0.2 0.4 0.6 0.8 1.0
Ref
lect
ion
Func
tion
(2.1
42 µ
m)
Reflection Function (0.664 µm)
0 = 26°, = 40°, = 42°
32 µm
16 µm
8 µm
4 µm
2 µm
3224161284
2
c
re =
486
80
Variation with Particle Size (r eff )(IWP= 10 g m -2 ; 10.8-10 km)
Wavenumber (cm -1 )
Clo
ud F
orci
ng (K
)
0
10
20
30
40
50
60
70
700 800 900 1000 1100 1200 1300
4.5 micron
22.5 micron
Kaolinite montmorillonite
Kaolinite montmorillonite
Optical properties of cloud particles: imaginary part of refraction index
SW & LW channel differences are used for cloud identification{4 m - 11m}, {4.13 m - 12.6m}, and {4.53 m - 13.4m}
Imaginary part of refraction index
wavelength [microns]
0
0.1
0.2
0.3
0.4
0.5
0.6
1 3 5 7 9 11 13 15
Ice
Water
BT11-BT12 > 0 for ice BT11-BT12 < 0 for volcanic ash
Frank Honey 1980s
SO2 calculations from F. Prata
"Non-detection" of fog over snow surfaces with VIS channels:thick clouds and snow have the same reflectance
Fog Detection over Snow SurfacesFog Detection over Snow Surfaces
Emissivity as a function of wavelength and surface type
• Emissivity more variable near 3.9 m
• Sandy areas appear 5-10 K cooler at IR3.9 than at IR10.8 (at night, dry atmosphere)
• Different appearance of land surfaces during daytime, depending on surface typeIR3.9 IR10.8
Dry sand: 0.8 0.95
800 900 1000 1100 1200 13000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Wavenumber (cm-1)
n I
IceDust
Imaginary Index of Refraction of Ice and Dust• Both ice and silicate absorption small in 1200 cm-1 window• In the 800-1000 cm-1 atmospheric window:
Silicate index increasesIce index decreaseswith wavenumber
Volz, F.E. : Infrared optical constant of ammonium sulphate, Sahara Dust, volcanic pumice and flash, Appl Opt 12 564-658 (1973)
Dust and Cirrus SignalsDust and Cirrus Signals
wavenumber
Dust IR spectra – green clr sky vs dust particles of different size
Dust IR spectra – green clr sky vs dust layers at different heights
Fog and Low Stratus
Comparison of snow reflectance in VIS and NIR 1.6 channels
• Ch08 is in the centre of the O3 absorption band around 9
EnergyspectrumSource:EUMETSAT
Ch08
Figure 3c
Signals from lower parts of troposphere;But:Secondary maximum from higher than 100 hPa
WeightingfunctionsSource:EUMETSAT
AIRS radiance changes (in deg K) to atm & sfc changes 43
Aircraft S-HISLSE
Wavenumber (cm-1)
0.85
1.0
Bare Soil
Pure Vegetation
S-HIS OBS
12 m 9 m
Inferring surface properties with S-HIS high spectral resolution data - Note the large change, especially for bare soil, in surface emissivity between 960 and 1060 cm-1. The HES minimum mission would not cover both regions.
44