Investigations with
High Spectral Resolution IR Data
Lectures in Brienza
21 Sep 2011
Paul Menzel
UW/CIMSS/AOS
1
Investigations with
High Spectral Resolution Data
from AIRS
Paul Menzel
NOAA/NESDIS
in collaboration with
Tim Schmit, Jun Li, Youri Plokhenko,
Dave Tobin, Hank Revercomb
and colleagues at CIMSS
2
Earth emitted spectra overlaid on Planck function envelopes
O3
CO2
H20
CO2
4
ds line
broadening with pressure helps to explain weighting functions
ABC

MODIS
High
A
Mid
B

ABC
Low
C

5
Fourier Transform Spectrocopy
Infrared Atmospheric Sounding
A
b
s
o
r
p
t
i
o
n
H
e
i
g
h
t
Wavenumber
Energy Contribution
6
Fourier Transform Spectroscopy
Infrared Atmospheric Sounding
For a given water vapor spectral channel
Wet Atm.
H
E
I
G
H
T
Wet
Moderate
Moderate
Dry Atm.
Dry
0
Tau
100%
=dTau/Ht
7
Fourier Transform Spectroscopy
Infrared Atmospheric Sounding
Absorption
Wavelength Converts to Altitude
n3 n2 n1
Wavelength
Energy
8
Contribution
Vibrational Bands
CO2
O3
H2O
CO2
CO2 Lines
10
H2O Lines
11
Energy State Transitions
12
Rotational Lines
CO2
O3
H2O
CO2
Earth emitted spectrum in CO2 sensitive 705 to 760 cm-1
CO2
Lines
14
Associating relative weighting functions with the CO2 rotational bands
A
B
C
Hi
Mid
C
A
B
Low
Wavenumber
Weighting Function
15
Associating relative weighting functions with the CO2 rotational bands
A
B
C
Hi
Mid
Low
Wavenumber
Weighting Function
16
Broad Band
window
window
CO2
O3
Sampling of vibrational bands
Integration over rotational bands
H2O
17
… in Brightness
Temperature
18
High Spectral Resolution
Sampling over rotational bands
19
100
100
GOES
(18)
1000
Advanced Sounder
(3074)
1000
Moisture Weighting Functions
High spectral resolution advanced sounder will have more
and sharper weighting functions compared to current GOES
sounder. Retrievals will have better vertical resolution.
20
UW/CIMSS
These water vapor weighting functions reflect the radiance sensitivity of the specific channels
to a water vapor % change at a specific level (equivalent to dR/dlnq scaled by dlnp).
Moisture
Weighting
Functions
UW/CIMSS
21
The advanced sounder has more and sharper weighting functions
temperature weighting functions sorted by pressure of their peak (blue =
0)
AIRS
On
Aqua
Instrument
• Hyperspectral radiometer with
resolution of 0.5 – 2 cm-1
• Extremely well calibrated pre-launch
•
Spectral range: 650 – 2700 cm-1
• Associated microwave instruments (AMSU, HSB)
SPHERE
FOCAL PLANE
TELESCOPE
COLLIMATOR
SCAN MIRROR
FOLD MIRROR
Design
• Grating Spectrometer passively cooled to 160K, stabilized to 30 mK
PV and PC HdCdTe focal plane cooled to 60K
Focal plane has ~5000 detectors
•
, 2378 channels. PV
detectors (all below 13 microns) are doubly redundant. Two channels per
resolution element (n/Dn = 1200)
• 310 K Blackbody and space view provides radiometric calibration
• Paralyene coating on calibration mirror and upwelling radiation provides
spectral calibration
NEDT (per resolution element) ranges from
0.05K to 0.5K
•
Grating
Dispersion
RELAY
EXIT SLIT
FOCAL PLANE
GRATING

AFOCAL
RELAY

ENTRANCE
SLIT
SCHMIDT MIRROR
HgCdTe FOCAL PLANE
Spectral filters at each entrance slit and over each FPA
array isolate color band (grating order) of interest
22
GRATING ORDER SELECTION
via Bandpass Filters
•
with redundant active pulse tube cryogenic coolers
AIRS 2378
IASI 8461
HIRS 19
CrIS 1400
23
AIRS movie
AIRS Clear Sky Temperature Jacobians for US Standard
atmosphere, 680 cm-1 < v < 900 cm-1, Bad_Flag = 0
 Sort channels by pressure of Jacobian peaks
24
P (mbar)
AIRS nighttime granules over CONUS, 6 Sept 2002
Tb (K)
25
Mouse click or page down to start movie
P (mbar)
Tb (K)
26
P (mbar)
Tb (K)
27
P (mbar)
Tb (K)
28
P (mbar)
Tb (K)
29
P (mbar)
Tb (K)
30
P (mbar)
Tb (K)
31
P (mbar)
Tb (K)
32
P (mbar)
Tb (K)
33
P (mbar)
Tb (K)
34
P (mbar)
Tb (K)
35
P (mbar)
Tb (K)
36
P (mbar)
Tb (K)
37
P (mbar)
Tb (K)
38
P (mbar)
Tb (K)
39
P (mbar)
Tb (K)
40
P (mbar)
Tb (K)
41
P (mbar)
Tb (K)
42
P (mbar)
Tb (K)
43
P (mbar)
Tb (K)
44
P (mbar)
Tb (K)
45
P (mbar)
Tb (K)
46
P (mbar)
Tb (K)
47
P (mbar)
Tb (K)
48
P (mbar)
Tb (K)
49
P (mbar)
Tb (K)
50
AIRS data and Level 2 Products are processed at the
GSFC DAAC and available to the public!
The NASA GSFC Data Active Archive Center at
http://daac.gsfc.nasa.gov/
offers a menu driven
selection of archived calibrated navigated radiances as well as
derived products such as temperature and moisture soundings
and total column concentrations of water vapor and ozone.
51
52
53
54
Sounding with the CO2 bands
55
On-line off-line at 735 cm-1
56
In the IRW - A is off H2O line and B is on H2O line
A
A
B
C
Low
B
B
Sfc
IRW spectrum
A
Weighting Function
57
Microchannels in window region of spectrum
enable boundary layer moisture investigations
GOES-12 Sounder Bands
Smoothes over absorption lines of interest
58
• On-line vs off-line differences hold
key information about lower troposphere
59
Sieglaff, 2007
On-line off-line hyperspectral windows ΔBT
Sounder split
window ΔBT
60
61
62
Brightness Temperature (K)
Resolving absorption features in atmospheric windows
enables detection of temperature inversions
Texas
Spikes down Cooling with height
(No inversion)
Spikes up Heating with height
(low-level inversion)
Ontario
GOES
GOES
Wavenumber (cm-1)
Detection of inversions is critical for severe weather
forecasting. Combined with improved low-level moisture
depiction, key ingredients for night-time severe storm
development can be monitored.
63
IASI detection
of temperature
inversion
(black spectrum)
vs
clear ocean
(red spectrum)
64
Ability to detect inversions
disappears with
broadband observations
(> 3 cm-1)
65
On-line/off-line “signal”
Longwave window region
66
“AIRS or IASI-like”
Longwave window region
67
Longwave window region
68
Longwave window region
69
Longwave window region
70
Longwave window region
71
“Current GOES-like”
Longwave window region
72
Twisted Ribbon formed by CO2 spectrum:
Tropopause inversion causes On-line & off-line patterns to cross
15 m CO2 Spectrum
Blue between-line Tb
warmer for tropospheric channels,
colder for stratospheric channels
Signature not available at low resolution
strat
tropopause
trop
73
AIRS
obs in
H2O
band
77
AIRS over Europe on 6 Sep 02
79
Spatial distribution of 944.1 [1/cm] measurements [K]
80
Spatial distribution of 944.1 [1/cm] measurements [K]
81
Spatial distribution of 2555 [1/cm] measurements [K]
82
AIRS 2378
Transmittance
within H20
absorption
band
85
Atmospheric transmittance in H2O sensitive region of spectrum


86
Spatial distribution of Ch 1552 at 1385.02 [1/cm] measurements [K]
87
Spatial distribution of Ch 1553 at 1385.57 [1/cm] measurements [K]
88
Spatial distribution of Ch 1554 at 1386.11 [1/cm] measurements [K]
89
Spatial distribution of Ch 1555 at 1386.66 [1/cm] measurements [K]
90
Spatial distribution of Ch 1556 at 1387.21 [1/cm] measurements [K]
91
Atmospheric transmittance in
H2O sensitive region of spectrum

Studying spectral sensitivity
with AIRS Data

AIRS BT[1386.11] – BT[1386.66]
Spectral change of 0.5 cm-1
causes BT changes > 10 C
92
AIRS 2378
Transmittance
within CO2
absorption
band
93
Atmospheric transmittance in
CO2 sensitive region of spectrum

Studying spectral sensitivity
with AIRS Data

AIRS BT[747.8] – BT[747.4]
Spectral change of 0.4 cm-1
causes BT changes > 8 C
99
Radiosonde Validation
Andros Is. Bahamas, Sept 12, 1998
Raob
NAST
3km
Distance (75 km)
100
Hyperspectral IR Sounder nears Raob-like Depiction of Atmosphere
with an Order of Magnitude Increase in Spatial and Temporal Resolution
16
Temperature
16
Moisture
14
14
Number of independent Pieces of
Information
Number of independent Pieces of
Information
Information
Content
for Moist Atmospheres
Information Information
Content
for
Moist
Atmospheres
Content
for
Moist Atmospheres
12
10
8
6
4
2
0
12
Temperature
Moisture
future
12
10
18
8
current
6
4
2
0
12
18N
18
50N
18N
2000
Channelsof channels
Number
Hyperspectral IR Sounder
- land and coastal waters
- nearly instantaneous obs
- 10 km separation
- every hour
50N
RAOB
2000
RAOB
Channels
RAOB
- over land only
- 1 hour ascent
- 300 km separation
- 12 Z and 00Z only
Doubles critical low-level moisture information (wrt current sounder)
102
Spectral Signatures
seen with AIRS & IASI
Lectures in Delhi
2 February 2011
Paul Menzel
UW/CIMSS/AOS
103
AIRS Spectra from around the Globe
20-July-2002 Ascending LW_Window
104
AIRS data from 28 Aug 2005
Clear Sky Spectra
105
AIRS data from 28 Aug 2005
Clear Sky vs Opaque High Cloud Spectra
106
Zoom in
on spectra from cloudy fov
to see warming with height
above tropopause
in O3 absorption band
Zoom toolbar
107
High cloud at 250 hPa
108
Offline-Online in LW CO2
110
Offline-Online in H2O
112
Offline-Online in LW IRW showing low level moisture
Red changes less
113
Moisture Profiles (left) confirm west Black Sea (black) is more moist
114
AIRS radiance changes (in deg K) to atm & sfc changes
115
118
Inferring surface properties with AIRS high spectral resolution data
Barren region detection if T1086 < T981
T(981 cm-1)-T(1086 cm-1)
Barren vs Water/Vegetated
T(1086 cm-1)
AIRS data from 14 June 2002
119
from Tobin et al.
2500
1000
715 cm-1
120
Mt Etna eruption
28 October 2002
ISS photo
28 October 2002
MODIS Aqua
122
123
UW
CIMSS
Mt Etna Ash cloud at 500 hPa
126
Ash cloud and clear sky spectra
127
1
0.98
AVHRR channels 1
1
1
0.9
0.9
0.9
0.8
0.8
0.8
0.7
0.7
0.7
0.6
0.6
0.6
0.5
0.5
0.5
0.4
0.4
0.4
0.3
0.3
0.3
transmission
(total)
0.2
0.2
0.2
transmission
(scattering)
0.1
0.1
0.1
4
5
Ice
transmission (absorption)
0
0
0
8
979
10
11
12
13
14
9
10
11 7 12 8 13 79
18
transmission (total)
wavelength
(m) (m)
Wavelength
0.9
Mt Etna volcanic plume
SO2 (left) from 1284-1345
Ash (right) from 832-900
0.94
0.92
0.9
0.88
0.86
7
3
transmission
transmission
0.96
AVHRR channels
transmission (total)
transmission (scattering)
transmission (absorption)
4
5
Ash
14 10
8
11
9
10
12
11
13
wavelengthWavelength
( m)
(m)
12
14
transmission (scattering)
transmission (absorption)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
T10.8 - T12.0 > 0 water & ice
T10.8 - T12.0 < 0 volcanic ash
7
8
9
10
11
ET-ODRRGOS, Oxford, UK, 1-5
2002
12
13
14
128
Dust and Cirrus Signals
Imaginary Index of Refraction of Ice and Dust
• Both ice and silicate
Ice
Dust
0.8
absorption small in 1200 cm-1
window
• In the 800-1000 cm-1
atmospheric window:
0.7
0.6
Silicate index increases
0.5
nI
Ice index decreases
0.4
with wavenumber
0.3
0.2
0.1
0
800
900
1000
1100
Wavenumber
(cm-1)
wavenumber
1200
1300
Volz, F.E. : Infrared optical constant of
ammonium sulphate, Sahara Dust,
volcanic pumice and flash, Appl Opt 12
564-658 (1973)
132
IASI detection of dust
IASI detection of cirrus
red spectrum is from nearby clear fov
Dust and Cirrus Signals
Imaginary Index of Refraction of Ice and Dust
• Both ice and silicate
Ice
Dust
0.8
absorption small in 1200 cm-1
window
• In the 800-1000 cm-1
atmospheric window:
0.7
0.6
Silicate index increases
0.5
nI
Ice index decreases
0.4
with wavenumber
0.3
0.2
0.1
0
800
900
1000
1100
Wavenumber
(cm-1)
wavenumber
1200
1300
Volz, F.E. : Infrared optical constant of
ammonium sulphate, Sahara Dust,
volcanic pumice and flash, Appl Opt 12
564-658 (1973)
133
Hyperspectral Dust Observations
Desert
Red Sea
134
Hyperspectral Dust/Aerosol Modeling
Negative Slope 880 to 920 cm-1– The Dust Signature
Green – Clear Spectrum
820
Effect of Dust Particle Sizes
920
650
Effect of Dust Layer Location
1000
Negative slope
kCARTA+DISORT, spectral resolution = 0.0025 cm-1
Sokolik, Univ Colo,1352002
136
Investigating the Eye of a Tropical Cyclone with AIRS
140
Isabel Eye Sounding from AIRS
Eye - Environment
Temperature
100
200
Eye Sounding
Environment
Sounding
Pressure (hPa)
300
400
500
600
700
800
900
1000
0
2
4
6
8
10
12
14
16
18
Temperature Anomaly (C)
Integrate Hydrostatic Equation Downward from 100 hPa to Surface
Environment Sounding: Ps = 1012 hPa
Eye Sounding:
Ps = 936 hPa
141
Aircraft Recon:
Ps = 933 hPa
DeMaria, CIRA, 2004
Brightness Temperature Spectra reveal changes in atmosphere
from eye to boundary of Tropical Cyclone
Brightness temperature spectra
~999 1/cm radiances
AIRS observations of tropical storm Isadore
on 22 Sept 2002 @ ~19:12-19:18 UTC
142
Example Spectra
143
Day or night?
144
Day, night, desert, or ice/snow?
145
Day or night?
146
Land or ocean?
147
Desert, ocean, or cloudy?
148
Day, night, desert, or ocean?
149
Ocean, cloudy, snow/ice, or desert?
150
Day, night, desert, or cloudy?
151
Cloudy, desert, or ocean?
152
Land, desert, ice/snow, or ocean?
153
Day, night, desert, or cloudy?
154
Day, night, ocean, or cloudy?
155