# Presentation: 153647

## Comparison of airborne sunphotometer and satellite sensor retrievals of aerosol optical depth during MILAGRO/INTEX-B

- J. Redemann(1,3), J. Livingston(2,3),** **P. Russell(3), R. Johnson(3),
- Q. Zhang(1),  L. Remer(4), R. Kahn(5), O. Torres(6), B. Veihelmann(7),
- P. Veefkind(7), A. Smirnov(6), B. Holben(4)
- (1) Bay Area Environmental Research Institute (BAERI), Sonoma, CA, USA
- (2) SRI International, Menlo Park, CA, USA
- (3) NASA Ames Research Center, Moffett Field, CA, USA
- (4) NASA Goddard Space Flight Center, Greenbelt, MD, USA
- (5) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- (6) University of Maryland, Baltimore County (UMBC)/NASA Goddard, Greenbelt, MD, USA
- (7) Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
- http://geo.arc.nasa.gov/sgg/INTEX-B/index.html
- email: _[jredemann@mail.arc.nasa.gov](mailto:jredemann@mail.arc.nasa.gov)_

## Jetstream 31 in MILAGRO/INTEX-B: Instrument Locations

**Jetstream 31 in MILAGRO/INTEX-B: Instrument Locations**

| RSP | Total & linearly polarized reflectance | 412-2250 nm, 9  |
| --- | --- | --- |
| SSFR | Upwelling & downwelling spectral hemispheric irradiance | 300-2200 nm, many 
~8-12 nm resolution |
| CAR | Spectral & angular distribution of scattered light from clouds, aerosols, land and water surfaces; imagery of clouds & surface | 340-2130 nm |

## NASA Ames Airborne Tracking Sunphotometer: AATS-14

- 1.	Measures direct solar beam transmission:
- 	 353.5    380.0     449.0      499.4     525.0
-      605.7    675.1     778.4      864.5     939.7
-     1019.1   1241.3   1557.8    2139.0 nm
- Yields:
- 	aerosol optical depth + aerosol extinction when A/C flies profiles
- 	columnar water vapor (ozone) + water vapor (ozone) concentration when A/C flies profiles
- Size:
- 	Telescope dome 8" OD  (hemisphere) atop 5" H pedestal.  (Total H:  9" above A/C skin), Inside A/C: 12" D x 18" H cylinder.
- Weight:
- 	131.6 lbs

## J31 flight tracks: 13 flights out of Veracruz, Mexico

**J31 flight tracks: 13 flights out of Veracruz, Mexico**

**9 flights over water**

**4 flights over land**

- Mexico

- Gulf of Mexico

## J31 flight patterns:Coordinated satellite, in-situ and radiative missions 

**J31 flight patterns:****Coordinated satellite, in-situ and radiative missions**

- OMI/Aura

- POLDER/Parasol

- MODIS/Aqua

- MISR, MODIS/Terra

**DC-8**

**C-130**

**B200**

**J-31**

## Outline

- Jetstream 31 (J31) instrument payload and flight overview
- Airborne, satellite, and ground-based AOD comparisons
**AATS-14 (Ames Airborne Tracking Sunphotometer) & MODIS AOD spectra over water (Gulf of Mexico) for all coincidences during MILAGRO**
- AATS-14, OMI (UV and MW retrievals), & MODIS over water (2 cases)
- 	  -10 March (Aqua, Aura)
- 	  -17 March (Aqua, Aura)
- AATS-14, OMI, & AERONET over Mexico City (1 case)
- 	  -19 March (Aura)
- AATS-14, MODIS, & MISR over water (1 case)
- 	  -10 March (Terra)
- Summary/Conclusions

## J-31 Research Flight 06, 10 March 2006

- Note: MODIS RGB images, with MODIS AOD maps overlaid for every J-31 flight available at: _[http://geo.arc.nasa.gov/sgg/INTEX-B/](http://geo.arc.nasa.gov/sgg/INTEX-B/)_            Acknowledgements appreciated.

**J31 flight track**

## Slide 8

## AOD Comparisons, MODIS vs AATS

**92% of points **
**fall within **
**band**

**MODIS uncertainty band**

**100% of points **
**fall within **
**band**

**Satellite (MODIS) AOD**

**Sunphotometer (AATS-14) AOD**

- _Agreement at MODIS SWIR wavelengths is better than expected_, because the number of points falling within the uncertainty band exceeds 66%, which is the expected fraction if the MODIS uncertainty (±0.03 ±0.05AOD) is ±1.

**AOD Comparisons, MODIS vs AATS**
- Gulf of Mexico, INTEX-B/MILAGRO, 2006

**37 cells**

**18 cells**

**MODIS-Terra (March 5, 10, 12)**

**MODIS-Aqua (March 10, 17)**

**MODIS wavelengths**

## Outline

- Jetstream 31 (J31) instrument payload and flight overview
- Airborne, satellite, and ground-based AOD comparisons
- AATS-14 (Ames Airborne Tracking Sunphotometer) & MODIS AOD spectra over water (Gulf of Mexico) for all coincidences during MILAGRO
**AATS-14, OMI (UV and MW retrievals), & MODIS over water (2 cases)**
**	****  ****-10 March (Aqua, Aura)**
**	****  ****-17 March (Aqua, Aura)**
- AATS-14, OMI, & AERONET over Mexico City (1 case)
- 	  -19 March (Aura)
- AATS-14, MODIS, & MISR over water (1 case)
- 	  -10 March (Terra)
- Summary/Conclusions

## The A-Train is a set of satellites that fly in sequence

**The A-Train is a set of satellites that fly in sequence**

**Many J31 flights included legs or profiles under the A-Train or other satellites**

## AOD Comparisons, OMI - MODIS - AATS

- INTEX-B/MILAGRO, 2006

- MODIS

## AOD Comparisons, OMI - MODIS - AATS

- INTEX-B/MILAGRO, 10 March 2006

- J31 low altitude transect 19:40-20:01 UT

## 10 March 2006 (over water)

- 10 March 2006 *(over water)*

*Case 1*

**J31/AATS measurements**

- AOD extrema along transect

## 10 March 2006 (over water)

- 10 March 2006 *(over water)*

*Case 1*

- OMI MW & UV AOD retrievals significantly exceed MODIS and AATS values.

- (Prelim)

## 17 March 2006 (over water)

- 17 March 2006 *(over water)*

- Aqua overpass: 20.07 UT

*Case** 2*

- Aura overpass: 20.32 UT

- Large OMI AODs may be due to cloud contamination.

- (Prelim)

## Outline

- Jetstream 31 (J31) instrument payload and flight overview
- Airborne, satellite, and ground-based AOD comparisons
- AATS-14 (Ames Airborne Tracking Sunphotometer) & MODIS AOD spectra over water (Gulf of Mexico) for all coincidences during MILAGRO
- AATS-14, OMI (UV and MW retrievals), & MODIS over water (2 cases)
- 	  -10 March (Aqua, Aura)
- 	  -17 March (Aqua, Aura)
**AATS-14, OMI, & AERONET over Mexico City (1 case)**
**	****  ****-19 March (Aura)**
- AATS-14, MODIS, & MISR over water (1 case)
- 	  -10 March (Terra)
- Summary/Conclusions

## Slide 18

## Slide 19

## Larger OMI MW AOD retrievals over land likely due to incorrect surface albedo assumption.

- highest quality

- AATS AOD:   high variability, flat  depend.

- (Prelim)

## Overestimate of sunphotometer AODs by OMI UV algorithm may also be due to incorrect assumption of surface reflectivity.

- (Prelim)

## Outline

- Jetstream 31 (J31) instrument payload and flight overview
- Airborne, satellite, and ground-based AOD comparisons
- AATS-14 (Ames Airborne Tracking Sunphotometer) & MODIS AOD spectra over water (Gulf of Mexico) for all coincidences during MILAGRO
- AATS-14, OMI (UV and MW retrievals), & MODIS over water (2 cases)
- 	  -10 March (Aqua, Aura)
- 	  -17 March (Aqua, Aura)
- AATS-14, OMI, & AERONET over Mexico City (1 case)
- 	  -19 March (Aura)
**AATS-14, MODIS, & MISR over water (1 case)**
**	****  ****-10 March (Terra)**
- Summary/Conclusions

## J31 flight track

**J31 flight track**

## Slide 24

## Slide 25

## AOD Comparisons, MISR - MODIS - AATS

- Gulf of Mexico, INTEX-B/MILAGRO, 10 March 2006

## Summary/Conclusions

- AATS-14 MILAGRO/INTEX-B data set is **very mature** and the latest version is **archived**; future changes will likely affect only singular data points at high altitude; would require fine-combing by hand.
**Validation of MODIS (-Terra & -Aqua) AOD well underway**: **major finding** is **exceptionally good agreement** with AATS and **appreciable AOD at SWIR**.
- For AATS/OMI coincidences, archived OMI near-UV AODs and preliminary **OMI** MW **AODs exceed AATS AODs**, but these cases need to be examined in more detail.  Differences may be due to _**cloud contamination**_** over water** or to the _**surface albedo**_** assumed by the OMI retrieval algorithms over land**.  *Analysis of coincident measurements by other J31 sensors (SSFR, RSP, and CAR) should provide additional information on surface spectral albedo and BRDF. ***Still to be investigated: effect of **_**MILAGRO- measured wavelength-dependent SSA in UV**_**.**
**AATS, MODIS, and MISR** over-water AOD spectra have been compared for a Terra overpass: **near-IR AODs agree** within uncertainties **in all 3 MISR grid cells**; in the **visible**, MISR AODs agree with AATS and MODIS values in **2 of 3** co-located MISR cells.
**Collaboration between AATS and other J-31 sensors is in its initial phase**.

## End of Presentation

**Remaining Slides are Backup**

## Outline

- Jetstream 31 (J31) instrument payload and flight overview
- Airborne, satellite, and ground-based AOD comparisons
- AATS-14 (Ames Airborne Tracking Sunphotometer) & MODIS AOD spectra over water (Gulf of Mexico) for all coincidences during MILAGRO
- AATS-14, OMI (UV and MW retrievals), & MODIS over water (2 cases)
- 	  -10 March (Aqua, Aura)
- 	  -17 March (Aqua, Aura)
- AATS-14, OMI, & AERONET over Mexico City (1 case)
- 	  -19 March (Aura)
- AATS-14, MODIS, & MISR over water (1 case)
- 	  -10 March (Terra)
- Summary/Conclusions