# Presentation: 531980

## Combined use of OMI, MODIS and CALIPSOobservations for characterization of aerosol absorption

- Omar Torres, Zhong Chen
- Hampton University, Hampton, Va
- Changwoo Ahn
- SSAI Inc, Lanham, MD
- S.K. Satheesh, L. Remer, P.K.Bhartia
- Goddard Space Flight Center, Greenbelt, MD

**EOS AURA Science Team Meeting**
**27-30 October 2008, Columbia, Maryland**

## Aerosol-sensing instruments in the A-train

**OMI, PARASOL, Calipso, MODIS,AIRS are currently  operational**

**NPP**

**NPP-VIIRS and Glory-APS will join the A-train **

**Aerosol-sensing instruments in the A-train**

## Aerosol-Sensing Capabilities of A-train 

| Sensor | Optical
Depth | Particle
Size | Real Ref.
Index | SSA | Particle
Shape | Aerosol Layer Height. |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| MODIS (VIIRS) | ✓ | ✓ |  | ✓ |  |  |  |
| PARASOL | ✓ | ✓ |  |  | ✓ |  |  |
| OMI | ✓ |  |  | ✓ |  |  |  |
| CALIPSO | ✓ |  |  |  | ✓ | ✓(VD,NT) |  |
| AIRS |  |  |  |  |  | ✓(NT) |  |
| Glory-APS | ✓ | ✓ | ✓ | ✓ | ✓ |  |  |

**Aerosol-Sensing Capabilities of A-train **
**Instrumentation**

- Caveats:
- -Not all sensors have daily global coverage
- -Land-ocean differences in retrieval accuracy
- -Differences in wavelength

- ✓ Validated
- ✓ Unverified
- ✓ Planned

## OMI Near UV Retrieval Procedure 

- The relationship between the observed radiances at 354 and 388 nm in the presence of absorbing aerosols is mainly driven by three aerosol parameters:
- Total Aerosol Load (AOD)
- Single Scattering Albedo (SSA)
- Aerosol Layer Height
- Since the Algorithm only uses two pieces of information, it is necessary to assume the value of one of the aerosol parameters to retrieve the other two.
- Standard Near-UV algorithm makes an assumption on the aerosol layer height.

## OMI Near-UV Retrieval Products 

| 0.0 | AOD0.0 | SSA0.0 |
| --- | --- | --- |
| 1.5 | AOD1.5 | SSA1.5 |
| 3.0 | AOD3.0 | SSA3.0 |
| 6.0 | AOD6.0 | SSA6.0 |
| 10.0 | AOD10.0 | SSA10.0 |

- 2. Most likely AOD and SSA values are chosen based on a choice of aerosol layer height from climatological  considerations
- Both the height dependent set of retrievals as well as the recommended solution are reported in the Level-2 Product.

- 1. Set of AOD/SSA for 5 different assumptions on aerosol layer height:

## OMI Retrieved Dust Properties (March 9-2007)

**OMI Retrieved Dust Properties (March 9-2007)**

## Evaluation of extinction AOD using AERONET observations                         

## DJF

- MAM

- JJA

- SON

**Seasonal Averages of Aerosol Absorption (OMI 2006)**

**Single Scattering Albedo**

**Absorption Optical Depth**

##            Combined OMI-MODIS retrieval

- Use MODIS retrieved AOD as input to the OMI retrieval
- and return  the aerosol height and single scattering albedo

| z1 | AOD1 | o1 |
| --- | --- | --- |
| z2 | AOD2 | o2 |
| z3 | AOD3 | o3 |
| z4 | AOD4 | o4 |
| z5 | AOD5 | o5 |

## First, can MODIS AOD retrieval

-   (466 to 2130 nm) be extrapolated
-    to the UV wavelength of 388 nm?

- MODIS extrap 380 nm AOD

- AERONET measured 380 nm AOD

- Ascension Island

- AERONET - MODIS AOD 380

- Linear extrap

- AOD470 -AOD870

- Simple linear extrapolation (log-log)
- is good, but not adequate.
- Deviations from linear can be
- explained by the difference in
- AOD at 440 and 870 nm

**Satheesh et al. (JGR, accepted)**

## Linear extrapolation

- With curvature correction

## Areas of study

- Satheesh et al. (to be submitted)

## Atlantic Ocean

**Atlantic Ocean**

**Arabian Sea**

- AOD380
- OMIstd - OMIMOD

- Months in 2006

- Months in 2006

- 0.15

- 0.3

- All data

- o380
- OMIstd - OMIMOD

- -0.1

- Height (km)
- OMIstd - OMIMOD

- -0.03

- 2

- -3.5

## Validating height retrieval

- In Arabian Sea

## Summary of Results

**Monthly mean values of AOD, ********o**** and layer height for the months of Jan 06 and Mar 06 for the 3 regions**

**Summary of Results**

## OMI – Calipso Synergy,  March 9, 2007

**OMI – Calipso Synergy,  March 9, 2007**

-  0

- 5

- Height (km)

*MODIS RGB*

**OMI**

**OMI, Calipso orbital coverage**

## AI 

- AI

- AOD_std

**AOD_cor**

**OMI –Calipso ,Synergy, March 9, 2007 (2)**

## Detection of Aerosols above clouds: 

**Detection of Aerosols above clouds: **
**A unique near-UV capability**

## Summary

- The unprecedented observational simultaneity of the A-train presents
- new opportunities for more accurate measurements of aerosol properties:
- optical depth,  particle size and information on shape, single scattering
- albedo and aerosol layer height.
- Preliminary results on the combined use of MODIS-OMI and Calipso-OMI
- retrievals illustrate the great potential of A-train retrieval capabilty of
- the A-train.
**             ****Current and Future Work**
-    Combined OMI-MODIS application will be extended over land. Calipso
-    will be used for validation.
-   An improved near-UV algorithm capable of retrieving aerosol absorption
-   in the presence of clouds  is currently being developed.