# Presentation: 669720

## Airborne Spectral and Angular Measurements of Surface and Aerosol Optical Properties 

- Charles K. Gatebe
- GEST/UMBC

**Notes:**
Charles Gatebe (CAR scientist)
 Ralph Kahn (guest scientist)
 Tom Wilson (software engineer)
 Peter Hobbs (mission scientist)
 Brian Magi (graduate student -UW)
 Andrea - graduate student (from Brazil)
 Jim Ellers - AATS NASA Ames
 Gerry - Second Pilot
 Bob Eatwell - Mechanical Engineer
 Ken Mcmillan - Lead Pilot
 Don Spangeon - Instrument Technician
  Art Ragno - Meteorologist
  Grant Gray - Electrician/Electronics

## Personnel

- Michael King

- Thomas  Arnold

- Charles Gatebe

- Engineers
- Peter Shu
- Hollis Jones

**Notes:**
Draw your awareness to spectral and directional surface reflectance measurements

## OTHERS

- Oleg Dubovik
- Alexander Sinyuk
- Gala Wind
- Steve Platnick
- Si-Chee Tsay
- Eric Vermote
- Alex Lyapustin
- Peter Hobbs
- Paul Hubanks

- etc

## CLOUD ABSORPTION RADIOMETER

- Goddard Space Flight Center
- developed in 1982-1983
- University of Washington
- integrated & flown in 1984 (B-23)
- principal data from 1987-97 (C-131A)
- flights after 1998-2001 (CV-580)
- Sensor Characteristics
- 14 spectral bands ranging from 0.34 to 2.29 μm
- scan ±95° from horizon on right-hand side of aircraft
- field of view 17.5 mrad (1°)
- scan rate 1.67 Hz (100 rpm)
- data system 9 channels @ 16 bit
- 395 pixels in scan line
- 4% reflectance calibration accuracy

- CAR

## The beginning:

- Douglas B-23 Aircraft Jan -May 1984 [1970-1984]
- Served as proof of concept

**Notes:**
1970-1984 CARG first plane - was a World War-II-vintage Douglas B-23 previously owned by Howard Hughes. Its first mission was to gather measurements in Pacific Northwest storms, studies that provided the first details on the organization of precipitation in the cyclones that occur outside the tropics. The B-23 is now displayed in the McChord Air Museum at McChord Airforce Base near Tacoma.

## 2nd Generation:

- UW C-131A
-  Between 1984-1997
- Most field experiments with CAR were done on this platform

**Notes:**
Experiment: KOFSE 1991; LEADEX 1992; SCAR-A 1993; ARMCAS 1995; SCAR-B 1995 TARFOX 1996
Kuwait oil fire smoke, Saudi Arabian desert and Persian Gulf water
Kuwait Oil Fire Smoke Experiment (KOFSE), May 1991
Snow-covered sea ice and tundra
Lead Experiment (LEADEX), April 1992
Great Dismal Swamp
Sulfate, Clouds, and Radiation-Atlantic (SCAR-A), July 1993
Cerrado, dense forest, and smoke layer
Smoke, Clouds, and Radiation-Brazil (SCAR-B), August-September 1995
Melt-season sea ice and snow-free tundra
Arctic Radiation Measurements in Column Atmosphere-surface System (ARMCAS), June 1995
First ISCCP Radiation Experiment-Arctic Cloud Experiment (FIRE-ACE), May-June 1998
Atlantic Ocean
Tropospheric Aerosol Radiative Forcing Experiment (TARFOX), July 1996
Arctic stratus clouds
FIRE-ACE, May-June 1998

## 3rd Generation:

- CV-580:  1998-2001
- Three field experiments on this platform

**Notes:**
Retrofitted in the late 1990s, Husky One was one of the world’s best-equipped planes for measuring trace gases, aerosols, clouds and precipitation. The 40-year old aircraft, kept in a hangar at Paine Field in Everett, was acquired as surplus property from the federal government. 
FIRE-ACE:1998; SAFARI-2000; CLAMS-2001
First ISCCP Radiation Experiment-Arctic Cloud Experiment (FIRE-ACE), May-June 1998 ; ISCCP - International Satellite Cloud Climatology Project
_x0013_SAFARI-2000: Southern African Regional Science Research Initiative 2000
CLAMS -Chesapeake Lighthouse and Aircraft Measurements for Satellite

## Currently --;)

- S.A. Aerocommander

- Jetstream-31

## DATA

- Available in several forms: quicklook images, flight track maps, flight logs, coincident satellite images, and HDF data distribution information
- _[http://www.car.gsfc.nasa/data.html](http://www.car.gsfc.nasa/data.html)_
- DAAC (e.g. NASA LaRC Atmospheric Sciences Data Center, ORNL DAAC)
- Contact King/Gatebe/Arnold

## Imaging Modes

- Horizontal

- Vertical

- BRDF Patterns

## Global Sites of CAR Measurements

- SAFARI’00

- SCAR-A’93

- TARFOX’96

- CLAMS’01

- SCAR-B’95

- LEADEX’92

- ARMCAS’95

- KOFSE’91

**Notes:**
FIRE-ACE:1998; SAFARI-2000; CLAMS-2001
First ISCCP Radiation Experiment-Arctic Cloud Experiment (FIRE-ACE), May-June 1998 ; ISCCP - International Satellite Cloud Climatology Project
_x0013_SAFARI-2000: Southern African Regional Science Research Initiative 2000
CLAMS -Chesapeake Lighthouse and Aircraft Measurements for Satellite
Kuwait oil fire smoke, Saudi Arabian desert and Persian Gulf water
Kuwait Oil Fire Smoke Experiment (KOFSE), May 1991
Snow-covered sea ice and tundra
Lead Experiment (LEADEX), April 1992
Great Dismal Swamp
Sulfate, Clouds, and Radiation-Atlantic (SCAR-A), July 1993
Cerrado, dense forest, and smoke layer
Smoke, Clouds, and Radiation-Brazil (SCAR-B), August-September 1995
Melt-season sea ice and snow-free tundra
Arctic Radiation Measurements in Column Atmosphere-surface System (ARMCAS), June 1995
First ISCCP Radiation Experiment-Arctic Cloud Experiment (FIRE-ACE), May-June 1998
Atlantic Ocean
Tropospheric Aerosol Radiative Forcing Experiment (TARFOX), July 1996
Arctic stratus clouds
FIRE-ACE, May-June 1998

## SAFARI-2000 Sites

## Marine Stratus

- 12:45 UTC

## MODIS Image:13 Sept. 2000

- 20°S

- 30°S

- 10°S

- 10°E

- 20°E

- 30°E

## Quicklook Image

- 90°

- 180°

- Scan

- Angle

- 12:42

- 12:45

- 12:49

- Clouds (off Namibian Coast): 9/13/2000

- Time (UTC)

## Cloud BRDF at 340 nm

- 270°

- 0.5

- 0.6

- 0.7

- 0.8

- 0.9

- 1.0

- 180°

- 0°

- 90°

- 0°

- 30°

- 60°

- 80°

- Reflection Function

## Cloud BRDF at 472 nm

- 0.5

- 0.6

- 0.7

- 0.8

- 0.9

- 1.0

- 270°

- 180°

- 0°

- 90°

- 0°

- 30°

- 60°

- 80°

- Reflection Function

## Cloud BRDF at 1036 nm

- 0.5

- 0.6

- 0.7

- 0.8

- 0.9

- 1.0

- 30°

- 60°

- 80°

- 0°

- 180°

- 90°

- 0°

- 270°

- Reflection Function

## Reflectance in the Principal Plane

- Scan Angle (°)

- Cloud Reflectance

- Glory

- Cloud bow

- Cloud bow

## MODIS Image:16 Sept. 2000

- 20°S

- 30°S

- 10°S

- 10°E

- 20°E

- 30°E

## Etosha Pan (Landsat 9/11/1999)

## Quicklook Image

- 90°

- 180°

- Scan

- Angle

- Salt Pan (Etosha, Namibia): 9/16/2000

- 09:07

- 09:10

- 09:12

- 09:14

- 09:17

- Time (UTC)

## Etosha Pan BRDF at 870 nm

- 0.0

- 0.3

- 0.6

- 0.9

- 30°

- 60°

- 80°

- 0°

- 180°

- 90°

- 270°

- 0°

- Reflection Function

## Etosha Pan BRDF at 472 nm

- 0.0

- 0.3

- 0.6

- 0.9

- 30°

- 60°

- 80°

- 0°

- 270°

- 180°

- 90°

- 0°

- Reflection Function

## Etosha Pan: P.Plane Reflectance

- Scan Angle (°)

- Pan Reflectance

## Savanna

- Skukuza, South Africa

- Picture by Jeff Privette NASA/GSFC

## MODIS Image:08/29/2000

- 20°S

- 30°S

- 10°S

- 10°E

- 20°E

- 30°E

## Quicklook Image

- 90°

- 180°

- Scan

- Angle

- 13:48

- 13:50

- 13:54

- Vegetation (Skukuza, South Africa): 8/29/2000

- Time (UTC)

- 13:52

- 13:56

## BRDF at 870 nm; Skukuza 

- 0.0

- 0.3

- 0.6

- 0.9

- 270°

- 180°

- 0°

- 90°

- 0°

- 30°

- 60°

- 80°

- BRDF at 870 nm; Skukuza

- Reflection Function

## P.Plane Reflectance; Skukuza

- Scan Angle (°)

- Reflectance

## OCEAN

- Glint19:42 UTC; 8/2/01

- Chesapeake Lighthouse, 20 kmoff Virginia coast

- 15:36 UTC; 7/14/01

## Quicklook Image

- 90°

- 180°

- Scan

- Angle

- Ocean (Chesapeake Lighthouse): 8/02/2001

- 20:05

- 20:07

- 20:09

- 20:11

- 20:13

- Time (UTC)

## Ocean BRDF at 472 nm

- Sunglint

- Aircraft
- Shadow

- 0.000

- 0.006

- 0.013

- 0.019

- 0.025

- 0.250

- 0.500

- 0.750

- 1.000

- Chesapeake LH; August 02, 2001

- Reflection Function

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.0

- 0.2

- 0.4

- 0.6

- 0.8

- Scan Angle (°)

- Reflectance

## Cox-Munk Validation (472 nm)

- Low- Glint

- Scan Angle (°)

- Scan Angle (°)

- High- Glint

- Relative difference

- Absolute difference

- Reflection Function

## Water-leaving Radiance: 472 nm

- 472 nm

- 0.000

- 0.006

- 0.013

- 0.019

- 0.025

- >100 km east of Wallops Island; July 23, 2001

- Reflection Function

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- Scan Angle (°)

- 0.000

- 0.010

- 0.020

- 0.030

- 0.040

- Reflectance

## Reflectance in  the P. Plane

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- 0.000

- 0.010

- 0.020

- 0.030

- 0.040

- Reflectance

- Scan Angle (°)

## Reflectance in  the P. Plane

- 0.000

- 0.010

- 0.020

- 0.030

- 0.040

- -80

- -60

- -40

- -20

- 0

- 20

- 40

- 60

- 80

- Reflectance

- Scan Angle (°)

## Ocean Albedo (total)

**Solar Zenith Angle (°)**

**Albedo**

**A(0.472 μm)=0.046±0.004**

**A(0.682 μm)=0.029±0.003**

**A(0.870 μm)=0.026±0.002**

## Albedo (water-leaving)

**Solar Zenith Angle (°)**

**Albedo**

**A(0.472 μm)=0.016±0.005 (0.014±0.002)**

**A(0.682 μm)=0.004±0.002**

**A(0.870 μm)=0.002±0.001**

## Aerosol-Surface Retrieval

- Take sky and surface brdf measurements
- There are 32,400 values of sky radiance measurements and an equal number for the surface reflectance at each channel
- Inversion code takes a maximum of 5000 data points
- Idea is to retrieve simultaneously surface and atmospheric properties from combined data

- Sky

- Surface

- 472 nm

## Data Reduction (CAR)

- (2) Check symmetry about

- average the values, but exclude those with scattering angle < 5°
- for inversion

- (3) If (difference (   ) /average) <25%

- corresponding pts

- Principal Plane

- (1) Average different circles

- 1

- 2

- 3

## Next:

| CAR
(μm; sky&sfc) | AATS
(μm; AOD) | AERONET
(μm; AOD) | AERONET
(μm; Sky) |
| --- | --- | --- | --- |
| 0.340 | 0.340 |  |  |
| 0.380 | 0.380 |  |  |
| 0.472 | 0.472 | 0.441 | 0.441 |
| 0.682 | 0.682 | 0.676 | 0.676 |
| 0.870 | 0.870 | 0.869 | 0.869 |
| 1.036 | 1.036 | 1.019 | 1.019 |
| 1.219 | 1.219 |  |  |
| 1.273 | 1.273 |  |  |

- Combine data (CAR,AERONET and AATS)   into a single matrix

## Sky Measurements Matrix

- 180

- 90

- 0

- 0

- 30

- 60

- 90

- Almucantar Measurements

- Principal PlaneMeasurements

- AOD Measurements

## Retrieval Scheme

***observations***

***fitting of observations by***
***forward model***

***forward model of ***
***the observations***:

***- For each aerosol layer : ***
***particle sizes, ref. index, etc.***
***- Parameters of surface***

## Inversion Procedure

-  ******AERONET, AATS-14)****	****± 0.01;0.02**
** ****I(********)** ******AERONET********± 5%**
- **I(********)** ******CAR********± 4%**

_**Inversion strategy:**_**        statistically optimized fitting**
- (Dubovik and King, 2000)

- measurements

***a priori***

***Lagrange**** parameter*

***consistency***
***indicator***

- weighting

## Specification of the Forward Model

**- Single scattering:** **aerosol particles - homogeneous spheres**

**Particle Size Distribution:**
**0.05 ********m ≤ r(22 bins) ≤ 15 ********m**

**Complex Refractive Index at **
****** ****= 0.34 - 1.27 ********m**

** ****Multiple scattering:**  **Nakajima-Nakajima DisOrds with RPV (Rahman et al., 1993)**

**- Atmospheric Model: 2 aerosol layers**

## Particle Size Distribution

- Good agreement with AERONET

- Particle Radius

- dv/dlnR,[μm^3/μm^2]

## Almucantar vs Principal Plane

- Good agreement

- Above Aircraft

- Below Aircraft

- Total Column

- Particle Radius

- Particle Radius

- Particle Radius

- dv/dlnR,[μm^3/μm^2]

- dv/dlnR,[μm^3/μm^2]

- dv/dlnR,[μm^3/μm^2]

## Other Retrieved Products

- Single Scattering Albedo

- Index of Refraction (Real)

- Imaginary Part

- BRF

- Scan Angle (°)

- Wvl (μm)

- Nb. Alm=almucantar; PP=principal plane

## Concluding Remarks

- Sensitivity studies
- Sensitivity of Particle size distribution to measurements uncertainty
- Single scattering albedo
- BRF
- Atmospheric correction to be performed on BRDF measurements using the new scheme

- Particle Size Distri.

- BRDF : 870 nm

- 0.0

- 0.6

- 0.4

- 0.2

- Mongu, Zambia

- 270

- 270

- 0

- 90

- 0

- 30

- 60

- Radius

- dv/dlnR,[μm^3/μm^2]

- Reflection Function

## Concluding Remarks

- More work on
- Sunglint

- Do Parameterization
-  of Case II water

- 0.000

- 0.006

- 0.013

- 0.019

- 0.025

- 0.250

- 0.500

- 0.750

- 1.000

- Chesapeake LH; August 02, 2001

- BRDF at 472 nm

- Reflection Function

## Future Measurements

- Since we have a capability to retrieve aerosol above and below aircraft, new measurements need to be made at different levels to allow understanding of the coupling between vertical distribution of aerosol and surface BRDF over different surfaces

- Concluding Remarks:

## Happy Holidays! 

- Happy Holidays!

- That’s all, dear friends!