# Presentation: 363806

## Characterization of Aerosols using Airborne Lidar, MODIS, and GOCART Data during the TRACE-P (2001) Mission

- Rich Ferrare1, Ed Browell1, Syed Ismail1, Yoram Kaufman2,
- Mian Chin2, Vince Brackett3, Carolyn Butler3,
- Marian Clayton3, Marta Fenn3, Jean Francois Léon4

- 1NASA Langley Research Center, Hampton, VA, USA
- 2NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 3SAIC/NASA Langley Research Center, Hampton, VA, USA
- 4Laboratoire d’Optique Atmospherique, Lille, France

- MODIS Science Team Meeting, March 2005

## Outline

- Motivation
- Objectives
- Airborne Lidar Measurements
- Lidar + MODIS retrievals
- GOCART model evaluation
- Summary and Future

## Motivation

- Key aerosol parameters required for assessing anthropogenic impacts on radiative forcing
- Vertical distribution
- radiative forcing
- surface temperature and climate responses
- Aerosol size distribution
- fine mode - biomass burning, pollution
- coarse mode - desert dust, sea salt
- Methodology
- Models
- Global coverage
- Large uncertainties in vertical distribution
- MODIS
- Estimates of fine, coarse mode over ocean
- Column average – no profile information
- Lidar
- High resolution vertical profiles
- Typically provide little quantitative information on size or composition

## Objectives

-  Use combination of airborne lidar and MODIS to provide information regarding the vertical distribution of fine vs. coarse aerosol modes
-  Retrieve aerosol extinction and optical thickness profiles from lidar data
-  Identify aerosol types vs. altitude
-  Evaluate ability of GOCART model to simulate aerosol extinction profiles and simulate contributions to fine and coarse modes

## NASA Langley UV DIAL Airborne Lidar

**NASA Langley UV DIAL Airborne Lidar**

- • **Ozone Differential Absorption Lidar (DIAL) Profiles**
**(****on****=289 nm & ********off**** =300 nm)**
- • **Aerosol & Cloud Scattering Ratio Profiles (300, 576, & 1064 nm)**
- • **Simultaneous Nadir and Zenith Ozone & Aerosol Profiling**
- • **Nadir Aerosol Depolarization Profiles (576 nm)**
-  **Deployed on NASA DC-8 for TRACE-P (2001), INTEX NA (2004)**

**Browell et al., J. Geophys. Res, 108(D20), 8805, 2003.**** **

## UV DIAL Measurements

** ****TRACE-P Flight 14 March 23-24, 2001**
** ****Extensive parameters (300, 576, 1064 nm)**
** ****aerosol scattering ratio**
** ****backscatter**
** ****extinction**
** ****Aerosol intensive parameters**
** ****backscatter wavelength dependence**
** ****depolarization**

## Retrieval of Aerosol Extinction Profiles

**Retrieval of Aerosol Extinction Profiles**

-  Backscatter lidar equation (2 unknowns)

-  Solution approaches
-  Assume a priori aerosol types and Sp values and use lidar measurements of intensive parameters to determine aerosol types
-  Use external information to constrain solution (e.g. MODIS AOT)

**“****Lidar Ratio” =**

## Retrieval of Aerosol Extinction Profiles

**Retrieval of Aerosol Extinction Profiles**

-  Aerosol types determined from AERONET climatology used for CALIPSO retrievals (Omar et al., 2003)

-  Use backscatter and extinction “color ratios” to infer aerosol type and corresponding lidar ratio (Sasano and Browell, 1989; Reagan et al., 2004)

**“****Lidar Ratio”**

## Retrieval of Aerosol Extinction Profiles

**Retrieval of Aerosol Extinction Profiles**

-  TRACE-P Flight 14 March 23-24, 2001
-  Good agreement between techniques for this test case

## Retrieval of Aerosol Extinction Profiles

**Retrieval of Aerosol Extinction Profiles**

-  TRACE-P Flight 14 March 23-24, 2001
-  Good agreement between techniques for this test case

## Retrieval of Aerosol Extinction Profiles

**Retrieval of Aerosol Extinction Profiles**

-  TRACE-P Flight 14 March 23-24, 2001
-  Inversion provides some indication of aerosol types
-  Planned modifications - examine layer averages to reduce sensitivity to noise in lidar profiles
-  Use in conjunction with GOCART results

## MODIS+lidar Aerosol Retrieval

-  Retrieval algorithm
-  (Kaufman et al., IEEE, 2003; GRL, 2003; Léon et al., JGR, 2003)
-  Aerosol size distribution – bimodal lognormal
-  MODIS aerosol models – 20 combinations of 4 fine, 5 coarse particles
-  Size of each mode is assumed to be altitude independent
-  Relative weight of each mode is determined as a function of altitude from lidar backscatter color ratio
-  Retrievals are constrained to fit MODIS measurements
-  Spectral reflectance
-  Column AOT and reff
-  Modifications
-  UV wavelength (300 nm) – more information on fine particle size
-  Depolarization – adjust the backscatter phase function for nonsphericity

## March 24, 2001 MODIS+GOCART

- Terra MODIS

**AOT (555 nm)**

**Effective radius**

**March 24, 2001 MODIS+GOCART**

- UV DIAL

## MODIS+lidar Aerosol Retrieval Example

-  TRACE-P Flight 14 March 23-24, 2001
-  Good agreement between techniques for this test case
-  Results show qualitative agreement with in situ measurements
-  Plan to evaluate additional cases from TRACE-P, INTEX NA

## March 24, 2001 MODIS+GOCART

- Terra MODIS

**AOT (555 nm)**

**Effective radius**

- GOCART

**Total AOT (500 nm)**

**Sulfate AOT (500 nm)**

**Dust AOT (500 nm)**

**Organic Carbon AOT (500 nm)**

**March 24, 2001 MODIS+GOCART**

## Comparison with GOCART

**Comparison with GOCART**

-  TRACE-P Flight 14 March 23-24, 2001
-  Attenuated aerosol scattering ratio

- GOCART

- UV DIAL

## GOCART March 24, 2001

**GOCART March 24, 2001**

**Total**

**Sulfate**

**Dust**

**Organic**
**Carbon**

## Comparison with GOCART

-  TRACE-P Flight 14 March 23-24, 2001

**Comparison with GOCART**

## Summary

-  Currently developing and evaluating algorithms to:
-  Retrieve profiles of aerosol extinction, optical thickness from airborne lidar and MODIS data
-  Infer profiles of aerosol type
-  Begun evaluating GOCART results using lidar, MODIS, in situ data
-  Initial comparisons show qualitative agreement
-  Future
-  Refine and implement algorithms for retrieving aerosol profiles from lidar data – with and without MODIS data
-  Evaluate algorithms using data from other TRACE-P, INTEX NA flights
-  Infer aerosol types as a function of altitude using lidar, MODIS, GOCART
-  Derive vertical distributions of fine, coarse mode particles for TRACE-P and INTEX NA