# Presentation: 638604

## to Sun Photometry of Desert Dust and Marine AerosolsPhil Russell, John Livingston, Oleg Dubovik, Stephanie Ramirez, Jian Wang, Jens Redemann, Beat Schmid, Michael Box and Brent Holben

**Honoring Prof. John Reagan,**** Tucson, AZ, 5-6 April 2005**

**Diffuse Light Corrections**** **

**to ****Sun Photometry of ****Desert Dust and Marine Aerosols****Phil Russell, John Livingston, ****Oleg Dubovik, Stephanie Ramirez, Jian Wang, Jens Redemann, ****Beat Schmid, Michael Box and Brent Holben**

## First, a few words about John Reagan and how he's helped our program. 

_**Our Program...**_

_**Like most research programs, ...**_

**ours stands on the shoulders of giants who came before**

## Of these giants, the single most influential has been John Reagan

**Some examples...**

## Slide 6

## Our water vapor retrieval methods:

_**Our water vapor retrieval methods:**_

**■ ****Schmid et al., *****J. Geophys. Res.,***** 1996.**

**■ ****Schmid et al. *****Appl. Opt.,***** 2001.**

## Our water vapor retrieval methods:

_**Our water vapor retrieval methods:**_

**■ ****Schmid et al., *****J. Geophys. Res.,***** 1996.**

**■ ****Schmid et al. *****Appl. Opt.,***** 2001.**

_**Are based on:**_

**■ ****Reagan et al., *****Proc. IGARSS '87 Symp.,***** 1987.**

**■ ****Reagan et al., *****IEEE Trans. Geosci. Rem. Sens.,***** 1992.**

## Designs for our existing instruments:

**AATS-6**

**AATS-14**

## Designs for our existing instruments

**and advanced concepts:**

**AATS****-6**

**ER-2 Sun Spectrometer**

**AATS****-14**

## influenced by the "Reagan sunphotometer" and by his specialized consulting, e.g.: 

**Designs for our existing instruments**

**influenced by the "Reagan sunphotometer" and by his specialized consulting, e.g.:**** **

**and advanced concepts:**

**AATS****-6**

**have been**

**ER-2 Sun Spectrometer**

**AATS****-14**

## Our measurements of the Pinatubo volcanic stratospheric aerosol...

**■ ****Russell et al., *****J. Geophys. Res.,***** 1993.**

**■ ****Russell et al., *****Geophys. Res. Lett.,***** 1993.**

## include corrections for diffuse light effects derived by Prof. Reagan and colleagues: 

**include corrections for diffuse light effects derived by Prof. Reagan and colleagues:**

**■ ****Russell et al., *****J. Geophys. Res.,***** 1993.**

**■ ****Russell et al., *****Geophys. Res. Lett.,***** 1993.**

**■ ****Reagan et al., Amer. Geophys. Union Chapman Conf. Climate, Volc., Global Change, Hilo, Hawaii, *****Conf. Abstracts*****, 1992.**

## The work I'll describe today extends that diffuse light correction work to sunphotometry of desert dust and marine aerosols

## The Problem:

_**The Problem:**_

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

## The Problem:

_**The Problem**_**:**

**The effect increases with particle size.**

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

## The Problem:

_**The Problem**_**:**

**The effect increases with particle size.**

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

_**Desert dust**_** and **_**marine aerosol**_** meas. especially susceptible.**

##  ACE-2, 1997

** ****ACE-2, 1997**

** ****PRiDE, 2000**

** ****ACE-Asia, 2001**

##  ACE-2, 1997

** ****ACE-2, 1997**

** ****PRiDE, 2000**

** ****ACE-Asia, 2001**

**Also, AATS-6 & AATS-14 have **_**larger FOVs**_** than most other sunphotometers ****(3.7° vs ~1.2°)**

**We needed to do a quantitative assessment of diffuse light effects for these aerosols and our FOVs**

## Bottom Line:

**The corrections turn out to be not a big deal**

## Bottom Line:

**The corrections are not a big deal**

**However, demonstrating this ****and automating the corrections was a big deal**

## Why?

**Let’s look at some previous results for **_**clouds**_** and **_**aerosols**_

## Why?

**Let’s look at some previous results for **_**clouds**_** and **_**aerosols**_

**First, define:********** = true optical depth***********'***** = apparent optical depth***C ***=***********'*****, the **_**correction factor**_

## Previous Results

| 
Method | FOV Half-angle , deg | 
Wave- length, m | 
Reff ,
m
 | 

C=' | 

Ref. |
| --- | --- | --- | --- | --- | --- |
| Clouds |  |  |  |  |  |
|   MC+af* | 1.2 | 0.55 | [cirrostratus] | 2.0 | Shiobara & Asano, 1994 |
|   MC+af* | 1,1.2,2.5 |  | 6-177 | 1.2-2.5 | Kinne et al., 1997 |

_**Previous Results**_

- *MC+af = Monte Carlo and analytical fit_** **_

## Previous Results

| 
Method | FOV Half-angle , deg | 
Wave- length, m | 
Reff ,
m
 | 

C=' | 

Ref. |
| --- | --- | --- | --- | --- | --- |
| Clouds |  |  |  |  |  |
|   MC+af* | 1,1.2,2.5 |  | 6-177 | 1.2-2.5 | Kinne et al., 1997 |
| Aerosols |  |  |  |  |  |
|   MC+af* | 1,1.2,2.5 |  | 0.2, 0.5 | ≤1.02 | Kinne et al., 1997 |
|   Reagan et
     al., 1992 | ≤2.2 | ≥0.38 | 0.9 | ≤1.05 | Russell et al., 1993 |
|   Analytical | ≤8 | 0.55 | 0.02-7.5 | 1.0-2.0 | Box & Deepak, 1979
 |

_**Previous Results**_

- *MC+af = Monte Carlo and analytical fit_** **_

## Volume Distributions for Typical Desert Dust and Marine Aerosols—AERONET & In Situ 

## Volume Distributions for Typical Desert Dust and Marine Aerosols—AERONET & In Situ 

**The coarse modes fall in a gap between most previous cloud and aerosol studies **

## Previous Results

| 
Method | FOV Half-angle , deg | 
Wave- length, m | 
Reff ,
m
 | 

C=' | 

Ref. |
| --- | --- | --- | --- | --- | --- |
| Clouds |  |  |  |  |  |
|   MC+af* | 1,1.2,2.5 |  | 6-177 | 1.2-2.5 | Kinne et al., 1997 |
| Aerosols |  |  |  |  |  |
|   MC+af* | 1,1.2,2.5 |  | 0.2, 0.5 | <1.02 | Kinne et al., 1997 |
|   Reagan et
     al., 1992 | <2.2 | >=0.38 | 0.9 | <=1.05 | Russell et al., 1993 |
|   Analytical | <8 | 0.55 | 0.02-7.5 | 1.0-2.0 | Box & Deepak, 1979
 |

_**Previous Results**_

- *MC+af = Monte Carlo and analytical fit_** **_

## Method of Calculation

_**Shiobara & Asano, 1994**_**:****Analytical expression obtained as a fit to their Monte Carlo results**

**where**

**Covers all orders of scattering, ****for ********slant**** = 0 to 6.**

-  Ξ Half-angle of sunphotometer FOV

## Analytical expression obtained as a fit to Monte Carlo results

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

**Analytical expression obtained as a fit to Monte Carlo results**

**Direct-beam transmission, T****dir ****= e****-********slant**

**Transmission**

**********slant**

## Analytical expression obtained as a fit to Monte Carlo results

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

**Analytical expression obtained as a fit to Monte Carlo results**

**Direct-beam transmission, T****dir ****= e****-********slant**

**Diffuse transmission, ****orders 1, 2 , & ≥3**

**Transmission**

**********slant**

## Analytical expression obtained as a fit to Monte Carlo results

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

**Analytical expression obtained as a fit to Monte Carlo results**

**Direct-beam transmission, T****dir ****= e****-********slant**

**Diffuse transmission, ****orders 1, 2 , & ≥3**

**Total transmission, ****T****dir+dif ****= e****-0.52********slant**

**Transmission**

**********slant**

## Analytical expression obtained as a fit to Monte Carlo results

**Shiobara & Asano, *****J. Appl. Meteor.,***** 1994**

**Analytical expression obtained as a fit to Monte Carlo results**

**Direct-beam transmission, T****dir ****= e****-********slant**

**Diffuse transmission, ****orders 1, 2 , & ≥3**

**Total transmission, ****T****dir+dif ****= e****-0.52********slant**

**Transmission**

**********slant**

## Example Results for a Dusty Day in ACE-Asia 

**C for********°)**** **

## Features of the Calculations

** ****Use a **_**wide range**_** of size distributions and compositions for **_**desert dust**_** and **_**marine aerosols**_**, from AERONET & in situ measurements.****▪ Account for effects of **_**non-sphericity**_**.****▪ Account for realistic mixtures of scattering by **_**gaseous atmosphere**_** and extinction by aerosols****.**

## Reff is a good predictor of correction factor 

**Results for ********=380 nm, ********=1.85****°****,**** **
**many aerosol**** sizes & compositions **

**R****eff**** is a good predictor of correction factor**** **

***f************Ξ****** C-1***** **

## fΞ C-1 

**Results for ********=380 nm, ********=1.85****°****,**** **
**many aerosol**** sizes & compositions **

***f************Ξ****** C-1***** **

## J31 in INTEX-ITCT – Aerosol Direct & Indirect Radiative Effects 

## J31 in INTEX-ITCT – Aerosol Direct & Indirect Radiative Effects 

## AATS-14: 14-channel Ames Airborne Tracking Sunphotometer 

**AATS-14: ****14-channel Ames Airborne Tracking Sunphotometer**** **

## AATS-6: 6-channel Ames Airborne Tracking Sunphotometer 

_**AATS-6**_**: ****6-channel Ames Airborne Tracking Sunphotometer**** **

_**Another**_** Example of Applying Correction Factors to Vertical Profiles of AOD in ACE-Asia **

## Summary & Conclusions

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

## Summary & Conclusions

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

** ****But, they can be as large as **_**10%**_** of AOD at 354 nm wavelength for Sun photometers with ********=1.85°** **(AATS-6 & AATS-14).**

## Summary & Conclusions

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

** ****But, they can be as large as **_**10%**_** of AOD at 354 nm wavelength for Sun photometers with ********=1.85°** **(AATS-6 & AATS-14).**

** ****For **_**pyrheliometers**_** (********=2.8°), corrections can be as large as **_**16%**_** at 354 nm**

## Summary & Conclusions

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

** ****But, they can be as large as **_**10%**_** of AOD at 354 nm wavelength for Sun photometers with ********=1.85°** **(AATS-6 & AATS-14).**

** ****The corrections are **_**easily automated**_** using parametric equations.**

** ****For **_**pyrheliometers**_** (********=2.8°), corrections can be as large as **_**16%**_** at 354 nm**

##  But, they can be as large as 10% of AOD at 354 nm wavelength for Sun photometers with =1.85° (AATS-6 & AATS-14).

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

** ****But, they can be as large as **_**10%**_** of AOD at 354 nm wavelength for Sun photometers with ********=1.85°** **(AATS-6 & AATS-14).**

** ****The corrections are **_**easily automated**_** using parametric equations.**

** ****We've applied them to our PRiDE & ACE-Asia data sets: ****e.g., http://geo.arc.nasa.gov/sgg/ACE-Asia/data_plots_login_page.html**

** ****For **_**pyrheliometers**_** (********=2.8°), corrections can be as large as **_**16%**_** at 354 nm**

##  Details: Russell et al., J. Geophys. Res., 2004 

**The corrections are negligible **_**(<~1%**_** of AOD) for Sun photometers with narrow FOV (half-angle ********<~1°, e.g., AERONET). (Agrees with Eck et al., 1999.)**

** ****Details: ****Russell et al., *****J. Geophys. Res*****., 2004**

** ****But, they can be as large as **_**10%**_** of AOD at 354 nm wavelength for Sun photometers with ********=1.85°** **(AATS-6 & AATS-14).**

** ****The corrections are **_**easily automated**_** using parametric equations.**

** ****We've applied them to our PRiDE & ACE-Asia data sets: ****e.g., http://geo.arc.nasa.gov/sgg/ACE-Asia/data_plots_login_page.html**

** ****For **_**pyrheliometers**_** (********=2.8°), corrections can be as large as **_**16%**_** at 354 nm**

## Caveats

** **_**Don't try this with clouds**_**. (They have ********=0, but corrections much larger than our parametric equations give.)**

** ****If dust particles have **_**angular, sharp-edge shapes**_ **(i.e., not coated or worn), C-1 can be **_**~50%**_** larger than our parametric equations give** **(Kalashnikova & Sokolik, 2002).**

## End of Presentation

**Remaining slides are backup**

## 14-channel Ames Airborne Tracking 
	Sunphotometer (AATS-14)

**14-channel Ames Airborne Tracking **
**	****Sunphotometer (AATS-14)**

_**Measures**_**: ****Solar direct-beam transmission, T, at 14 wavelengths, ********, 353-2139 nm**
_**Data products**_
**Aerosol optical depth (AOD) at 13 ********, 353-2139 nm**
**Water vapor column content [using T(940 nm)]**
**Aerosol extinction, **
**	****340-2139 nm**
**Water vapor **
**	****density**

**When **
**A/C**
**flies **
**vertical **
**profiles**

- }

## Jetstream-31 (J31) in INTEX-ITCT

**Ames Earth Science Seminar**
**7 Oct 2004**

## J31 Flight 7, 12 July 2004AATS Results

_**J31 Flight 7, 12 July 2004**__**AATS Results**_

## Slide 53

## J31 in INTEX-ITCT – Aerosol Direct & Indirect Radiative Effects