# Presentation: 731096

## MODIS Aerosol Algorithm 

- Validation, Updates and First Look at Aqua

- Lorraine Remer
- Yoram  Kaufman
- Didier Tanré

- Robert Levy
- Rong-Rong Li
- Charles Ichoku
- J. Vanderlei Martins
- Allen Chu
- Shana Mattoo
- Oleg Dubovik
- Zia Ahmad
- Richard Kleidman

## Validation

- Updates Implemented:
- 	- extension over land
- Updates to be Delivered :
- 	- sediment mask
- 	- adjustments to cloud mask
- 	- dust replacement (over glint!)
- 	- new land models
- On the horizon:
- 	- non-spherical dust models
- First looks at Aqua

## GRL special section

- Ichoku et al. (2002)
- Martins et al. (2002)
- Chu et al. (2002)
- Remer et al. (2002)

## N = 102

- 82%
- within error bars

- N=86
- 77%
- within error bars

## 		N	within

- 		N	within
- 			error
- ___________________________
- France_land	332	77%
- US east		282	56%
- NA_west	168	85%
- Med_land	139	60%
- Brazil		102	82%
- US central	100	72%
- SAFARI		89	72%
- East_Europe	58	84%
- Asia		45	64%

- AERONET data from stations operated by the following PI’s:
- B. Holben, C. McLain (SIMBIOS), D. Tanré
- Analysis by R. Levy and L. Remer

## 		N	within

- 		N	within
- 			error
- ___________________________
- Med_ocean	222	59%
- US_Atlantic	86	77%
- Saharan		63	37%

- AERONET data from stations operated by the following PI’s:
- B. Holben, C. McLain (SIMBIOS), D. Tanré
- Analysis by R. Levy and L. Remer

## 

## Land algorithm: “dark targets”

- But how dark is “dark” ?

- Following a suggestion by E. Vermote,
- we increase the 2.1 threshold from 0.25
- to 0.40 at nadir (and even higher at larger
- view angle).  From the extended threshold,
- we derive in the blue and extrapolate to
- the red.
- In this example the new version increases
- the number of retrievals over land from
- 7060 to 17,849.  For the 285 granules
- collected over southern Africa during the
- SAFARI campaign, V3.1.0 increases the
- number of land retrievals by 130%.

## 2001

- 2002

- Eight day means.
- Same dates,
- Different years

- Images cropped from
- MODIS Atmospheres web site
- Created by P. Hubanks

## Sediment Mask

- Li et al., submitted  to IEEE TGARS

## Sediment Mask

- Li et al. submitted to IEEE TGARS

## Sediment Mask

## operational

- new sediment mask

## Updates:  Cloud mask for aerosol retrievals

- spatial variability
- before: 3x3 window advances as a block
- now: 3x3 window advances every pixel
- high AOT  cutoff
- before: fill value for AOT > 5.0
- now: threshold on 0.47, not AOT
- regaining retrievals in dust
- before: lost high dust values
- now: r0.47/r0.66 separates dust from clouds
- dust over glint
- before: no retrievals over glint
- now: r0.47/r0.66 < 0.95 we retrieve heavy dust over glint

- J.V. Martins et al. in preparation

## Retrieving heavy dust over glint

- J.V. Martins et al., in preparation

## In 1493 C.E., Pope 

- In 1493 C.E., Pope
- Alexander VI divided
- the world with an
- arbitrary line.

- In 1995, Yoram Kaufman
- divided the world again,
- with many arbitrary lines.

## Operational

- aerosol
- models
- (1995 knowledge)

- o = 0.90

- o = 0.96

## Ichoku et  al. (in revision):  

- Ichoku et  al. (in revision):
- SAFARI 2000 special issue

## New Aerosol Models based on 2002 information

- AERONET and Dubovik et al. (2002)

- Analysis by L.Remer and D.A. Chu

## Retrieving non-spherical dust aerosol

- M. Meier and J. Reid

- 		N	within
- 			error
- ___________________________
- US_Atlantic	86	77%
- Med_ocean	222	59%
- Saharan		63	37%

## MODIS: June 25, 2002

- Terra: 16:10 UTC

- Aqua: 17:45 UTC

- Prepared by
- R. Levy

## MODIS

- Terra & Aqua
- AOT over land

- Terra & Aqua
- AOT over ocean

- By C. Ichoku (July 2002)

## Summary (page 1)

- The primary aerosol products are valid within pre-launch error
- estimations.
- First operational retrieval of aerosol over land.  First ever.
- Improvement of aerosol over ocean retrieval from AVHRR.
- 	(AVHRR=0.04    MODIS =0.02)

## Summary (page 2)

- Yes. We are making updates.
- Some of these changes are to ‘fix’ small issues: sediments
- Some of these changes are to ‘re-call’ retrievals: dust in glint,
- 	extension over land.
- _Fine mode/Coarse mode is a significant step forward_.
- Non-spherical phase functions will be a major innovation, but
- 	not ready for collection 4.
- Qualitatively, Aqua looks good.