# Presentation: 506905

## Remote Sensing of Tropospheric Aerosols from Space: Past, Present, and Future

***Michael D. King,******1****** Yoram J. Kaufman,******1****** Didier Tanré******2****** and Teruyuki Nakajima******3***
**1****NASA Goddard Space Flight Center, Greenbelt, MD  USA**
**2****Université des Sciences des Techniques de Lille, Villeneuve d’Ascq, France**
** ****3****Center for Climate System Research, University of Tokyo, Japan**
***Outline***
**Physical principles behind the remote sensing of aerosol parameters**
**International satellite sensors enabling remote sensing of tropospheric aerosols**
**AVHRR, TOMS, ATSR-2, OCTS, POLDER, SeaWiFS, MISR, MODIS, AATSR, MERIS, GLI, and OMI**
**Instrument characteristics**
**Spacecraft, spatial resolution, swath width, sensor characteristics, and unique characteristics**
**Aerosol retrieval from existing satellite systems**
**Future capabilities**
**Opportunities for the future**

## Reflection Function as a Function of Aerosol Optical Thickness

**R****(********a****, ********0****; μ, μ****0****, ********) = **
**The greatest sensitivity of reflected solar radiation to aerosol optical thickness occurs when**
**the surface reflectance is small**
**the single scattering albedo is large (small absorption)**
**larger slant angles (μ < 1)**

******I****(0, –μ, ****)**

**μ****0****F****0**

***Reflection Function as a Function of Aerosol Optical Thickness***

## MISR Provides New Angle on Haze

**In this MISR view spanning from Lake Ontario to Georgia, the increasingly oblique view angles reveal a pall of haze over the Appalachian Mountains**

## Eight MODIS bands are utilized to derive aerosol properties
0.47, 0.55, 0.65, 0.86, 1.24, 1.64, 2.13, and 3.75 μm
Ocean
reflectance contrast between cloud-free atmosphere and ocean reflectance (dark)
aerosol optical thickness (0.47-2.13 μm)
size distribution characteristics (ratio between the assumed two log-normal modes, and the mean size of each mode)
Land
dense dark vegetation and semi-arid regions determined where aerosol is most transparent (2.13 and 3.75 μm)
contrast between Earth-atmosphere reflectance and that for dense dark vegetation surface (0.47 and 0.66 μm)
enhanced reflectance and reduced contrast over bright surfaces (post-launch)
aerosol optical thickness (0.47 and 0.66 μm)

**0.47, 0.55, 0.65, 0.86, 1.24, 1.64, 2.13, and 3.75 μm**
**Ocean**
**reflectance contrast between cloud-free atmosphere and ocean reflectance (dark)**
**aerosol optical thickness (0.47-2.13 μm)**
**size distribution characteristics (ratio between the assumed two log-normal modes, and the mean size of each mode)**
**Land**
**dense dark vegetation and semi-arid regions determined where aerosol is most transparent (2.13 and 3.75 μm)**
**contrast between Earth-atmosphere reflectance and that for dense dark vegetation surface (0.47 and 0.66 μm)**
**enhanced reflectance and reduced contrast over bright surfaces (post-launch)**
**aerosol optical thickness (0.47 and 0.66 μm)**

***Aerosol Properties***

## Aerosol Effects on Reflected Solar Radiation over Land

**Biomass burning**
**Cuiabá, Brazil (August 25, 1995)**

**20 km**

**10  km**

******0**** = 36°**

**R****	****= 0.66 μm**
**G****	****= 0.55 μm**
**B****	****= 0.47 μm**

**R****	****= 1.65 μm**
**G****	****= 1.2 μm**
**B****	****= 2.1 μm**

***Aerosol Effects on Reflected Solar Radiation over Land***

## Surface Reflectance at Near-Infrared Wavelengths

**The aerosol effect on reflected solar radiation is small at 2.2 μm and large at 0.49 μm**
**MODIS operational algorithm over land assumes**

***Kaufman et al. (1997)***

**A****g****(0.47 μm) ****	****= 0.5****A****g****(0.66 μm)**
**	****= 0.25****A****g****(2.1 μm)**

***Surface Reflectance at Near-Infrared Wavelengths***

## Dynamic Aerosol Models

**Aerosol-free troposphere plus stratospheric aerosol (0.3 μm < *****r***** < 0.8 μm)**
**Maritime salt particles in the mid-Atlantic region (0.8 μm < *****r***** < 2.5 μm)**
**Coarse particles (*****r***** > 2.5 μm)**

***Remer et al. (1996)***

***Dynamic Aerosol Models***

## Techniques for Remote Sensing of Tropospheric Aerosol from Space

## Techniques for Remote Sensing of Tropospheric Aerosol from Space

***Techniques for Remote Sensing of Tropospheric Aerosol from Space***

## Aerosol Properties

***Aerosol Properties***

**Transmission**

**0.4**

**0.5**

**0.6**

**0.7**

**0.8**

**0.9**

**1.0**

**0.3**

**MODIS**

**MERIS**

**GLI**

**MISR**

**SeaWiFS**

**POLDER**

**OCTS**

**ATSR-2/AATSR**

**TOMS**

**AVHRR**

**Hyperspectral**

**0.0**

**0.2**

**0.4**

**0.6**

**0.8**

**1.0**

**Polarization**
**Polarization-Ocean**
**Polarization-Land-Ocean**
**Not Used for Aerosols**

**Land**
**Ocean**
**Land-Ocean**
**Cloud Mask**

**OMI**

## Aerosol Properties

**15.0**

**Transmission**

**Wavelength (μm)**

**MODIS**

**GLI**

**OCTS**

**ATSR-2/AATSR**

**AVHRR**

**1.5**

**2.0**

**3.0**

**4.0**

**6.0**

**10.0**

**20.0**

**1.0**

**0.0**

**0.2**

**0.4**

**0.6**

**0.8**

**1.0**

**Not Used for Aerosols**

**Land**
**Ocean**
**Land-Ocean**
**Cloud Mask**

**Near-infrared and thermal infrared**

***Aerosol Properties***

## Instruments, Spacecraft, and Principal Characteristics

***Instruments, Spacecraft, and Principal Characteristics***

## Instruments, Spacecraft, and Principal Characteristics

## Tropospheric Aerosol Data Record

***Tropospheric Aerosol Data Record***

**AVHRR****	****NOAA-7, 9, 11, 14, L, Metop-1**
**TOMS****	****Nimbus-7, Meteor, EP, ADEOS, QuikTOMS**
**ATSR-2****	****ERS-2**
**OCTS****	****ADEOS**
**POLDER****	****ADEOS ADEOS II**
**SeaWiFS****	****OrbView-2**
**MISR****	****Terra**
**MODIS****	****Terra**
**	****Aqua**

_**Instrument**_**	**_**Spacecraft**_

**1981**

**1982**

**1983**

**1984**

**1985**

**1986**

**1987**

**1988**

**1989**

**1990**

**1991**

**1992**

**1993**

**1994**

**1995**

**1996**

**1997**

**1998**

**1999**

**2000**

**2001**

**2002**

**2003**

**2004**

**USA**

**Europe**

**Japan**

## Tropospheric Aerosol Data Record

**AATSR****	****Envisat-1**
**MERIS****	****Envisat-1**
**GLI****	****ADEOS II**
**OMI****	****Aura**

_**Instrument**_**	**_**Spacecraft**_

**1981**

**1982**

**1983**

**1984**

**1985**

**1986**

**1987**

**1988**

**1989**

**1990**

**1991**

**1992**

**1993**

**1994**

**1995**

**1996**

**1997**

**1998**

**1999**

**2000**

**2001**

**2002**

**2003**

**2004**

**USA**

**Europe**

**Japan**

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**No Data**

**0.0**

**0.1**

**0.2**

**0.3**

**0.4**

**0.5**

**Aerosol Optical Thickness (0.63 μm)**

**AVHRR**
**April 1997**

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**No Data**

**0.0**

**0.2**

**0.4**

**0.6**

**0.8**

**1.0**

**Aerosol Optical Thickness (0.38 μm)**

**TOMS**
**April 1997**

**0.1**

**0.3**

**0.5**

**0.7**

**0.9**

## Radiance and Polarization Measurements from POLDER

**Western Europe **
**March 10, 1997**

**R  = 0.865 μm**
**G  = 0.670 μm**
**B  = 0.443 μm**

**Radiance**

**Polarization**

***Radiance and Polarization Measurements from POLDER***

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**No Data**

**0.0**

**0.1**

**0.2**

**0.3**

**0.4**

**0.5**

**Aerosol Optical Thickness (0.865 μm)**

**POLDER**
**April 1997**

## Ångström Exponent

***Ångström Exponent***

**No Data**

**0.0**

**Angstrom Exponent**

**0.1**

**0.2**

**0.3**

**0.4**

**0.5**

**0.6**

**0.7**

**0.8**

**0.9**

**1.0**

**No Retrieval**

**POLDER**
**April 1997**

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**No Data**

**0.0**

**0.1**

**0.2**

**0.3**

**0.4**

**0.5**

**Aerosol Optical Thickness (0.500 μm)**

**OCTS**
**April 1997**

## Ångström Exponent

***Ångström Exponent***

**OCTS**
**April 1997**

**No Data**

**0.0**

**Angstrom Exponent**

**0.1**

**0.2**

**0.3**

**0.4**

**0.5**

**0.6**

**0.7**

**0.8**

**0.9**

**1.0**

**No Retrieval**

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**MODIS**
**April 19, 2000**

## Aerosol Optical Thickness

***Aerosol Optical Thickness***

**0**

**20**

**40**

**60**

**80**

**100**

**Fraction of Aerosol Retrievals for 150 days**

## Global Distribution of AERONET Stations—August 2000

**Automatic recording and transmitting Sun/Sky Photometers**
**Data Base: Aerosol optical thickness, size distribution, phase function & precipitable water**
**Collaborative:****	****NASA – instruments/sites and centralized calibration & database**
**	****	****Non-NASA – instruments/sites**

## Slide 26

**Notes:**
Figure 6.	Composite image (left) of smoke, burn scars, and unburned vegetation in Mato Grosso on August 23, 1995.  The RGB assignment is red (2.19 μm), green (0.87 μm) and blue (0.65 μm), and is based on the individual channels shown in Fig. 5.  The middle panel is the resultant cloud and shadow mask, and the final panel the heavy aerosol and fire mask.  Most of the scene is classified as heavy aerosol, as expected.  The background image on which the cloud and aerosol mask are overlaid is the MAS reflectance image at 0.65 μm.

## TARFOX

**TARFOX**
**Atlantic Ocean (July 1996)**

**Sunphotometer optical thickness**

****** ****= 0.55 μm**

**0.0**

**0.3**

**0.0**

**0.2**

**0.1**

**0.4**

**0.5**

**0.6**

**0.3**

**0.0**

**0.2**

**0.1**

**0.4**

**0.5**

**0.6**

**Retrieved optical thickness**

**Notes:**
Figure 6.	Composite image (left) of smoke, burn scars, and unburned vegetation in Mato Grosso on August 23, 1995.  The RGB assignment is red (2.19 μm), green (0.87 μm) and blue (0.65 μm), and is based on the individual channels shown in Fig. 5.  The middle panel is the resultant cloud and shadow mask, and the final panel the heavy aerosol and fire mask.  Most of the scene is classified as heavy aerosol, as expected.  The background image on which the cloud and aerosol mask are overlaid is the MAS reflectance image at 0.65 μm.

## SCAR-B

**SCAR-B**
**Brazil (August-September 1995)**

**Sunphotometer optical thickness**

****** ****= 0.66 μm**

**0.0**

**1.5**

**0.0**

**1.0**

**0.5**

**2.0**

**2.5**

**1.5**

**1.0**

**0.5**

**2.0**

**2.5**

**Retrieved optical thickness**

**Forest**

**Cerrado**

**Notes:**
Figure 6.	Composite image (left) of smoke, burn scars, and unburned vegetation in Mato Grosso on August 23, 1995.  The RGB assignment is red (2.19 μm), green (0.87 μm) and blue (0.65 μm), and is based on the individual channels shown in Fig. 5.  The middle panel is the resultant cloud and shadow mask, and the final panel the heavy aerosol and fire mask.  Most of the scene is classified as heavy aerosol, as expected.  The background image on which the cloud and aerosol mask are overlaid is the MAS reflectance image at 0.65 μm.

## Tropospheric aerosols have been ‘rediscovered’ as a major influence on the radiation balance of the Earth, with a potentially large mitigating influence on greenhouse forcing
In the past we have been largely forced to use uncalibrated sensors or wide field-of-view ultraviolet spectrometers not specifically designed for the remote sensing of tropospheric aerosol properties
Since 1996, with the launch of OCTS and POLDER on ADEOS, we have entered a new era of quantitative remote sensing of tropospheric aerosol from space
With the launch of EOS, Envisat-1, and ADEOS II, we will have an unprecedented array of spaceborne sensors with unique characteristics that will enable quantitative aerosol observations on a global scale
Enhanced onboard calibration
Use of deep space and lunar maneuvers for calibration and sensor degradation analysis
Vigorous vicarious calibration using ground-based and airborne sensors
Narrow spectral bands that avoid molecular absorption bands
Multispectral and multiangle observations
Polarization

**In the past we have been largely forced to use uncalibrated sensors or wide field-of-view ultraviolet spectrometers not specifically designed for the remote sensing of tropospheric aerosol properties**
**Since 1996, with the launch of OCTS and POLDER on ADEOS, we have entered a new era of quantitative remote sensing of tropospheric aerosol from space**
**With the launch of EOS, Envisat-1, and ADEOS II, we will have an unprecedented array of spaceborne sensors with unique characteristics that will enable quantitative aerosol observations on a global scale**
**Enhanced onboard calibration**
**Use of deep space and lunar maneuvers for calibration and sensor degradation analysis**
**Vigorous vicarious calibration using ground-based and airborne sensors**
**Narrow spectral bands that avoid molecular absorption bands**
**Multispectral and multiangle observations**
**Polarization**

***Summary and Conclusions***

## These spaceborne sensors, when coupled with the AERONET network of sun/sky radiometers for the validation of satellite data, derivation of aerosol models, and statistical characterization of aerosol in remote pristine environments, should enable a much improved analysis of aerosol forcing of the Earth-atmosphere-ocean system
The next advance from space is monostatic lidar that will make it possible to characterize the vertical distribution of tropospheric aerosols and clouds that, when coupled with multispectral and multiangular radiometry, will advance the state of our knowledge of how aerosols interact with the Earth and its atmosphere
GLAS (December 2001)
PICASSO-CENA (February 2003)

**The next advance from space is monostatic lidar that will make it possible to characterize the vertical distribution of tropospheric aerosols and clouds that, when coupled with multispectral and multiangular radiometry, will advance the state of our knowledge of how aerosols interact with the Earth and its atmosphere**
**GLAS (December 2001)**
**PICASSO-CENA (February 2003)**

***Summary and Conclusions***