# Presentation: 722861

## Aerosol Mission Development

**Aerosol Mission Development**

**Mark Schoeberl**
**NASA/GSFC**

**Acknowledgement: Yoram Kaufman**

## Presentation Outline

**Aerosols - some background**
**Importance of aerosol measurements.**
**What we know and what we still need to know.**
**What an aerosol mission would look like.**

## What are Aerosols?

**Particle Diameter (μ)**

**0.001**

**0.01**

**0.1**

**1**

**10**

**100**

**Fine particles**

**Coarse particles**

**2**

**Rain**
**Washout**

**Sedimentation**

**Coagulation,**
**Water uptake**

**CN**

**Dust**
**Sea Spray**
**Volcanic Ash**

**Cloud Particles**

**Hot and Cool Vapors Condense**
**Chemical Reactions**
**Smoke, Pollution**

**Cloud Processing**

**Surface Area**

**Accumulation mode**

**10 μ settles at 1 cm/s**
**1μ settles at 0.01 cm/s**

***Molecules***

## Aerosol Scattering of Visible Light

**Aerosol Scattering of Visible Light**

**<0.05 μ Rayleigh scattering**
**0.05 -100 μ Mie scattering**
**>100μ geometric optics**

**1/******

**1/********4**

## Why do we care about aerosols?

**Aerosol radiative effects provide the largest uncertainty in the climate system.**
**Aerosols have a direct and negative impact on human health. **
**     ****(1-4% of deaths per year around the world are related to air pollution)**
**Aerosols appear to affect the hydrological cycle producing less rain where they occur and perhaps more rain in surrounding regions. This has a big impact on fresh water supplies.**

## Slide 6

## Aerosol, their sources and effects on climate

- Properties     Net effect               Aerosol type       Main Source_        _
- Reflect	         Cool the earth        Desert dust,       deserts
- Sunlight       reduce evaporation sulfate smog     industry
- Absorb	          Heat the atmosphere     Black carbon        biomass burning
- sunlight            increase stability	           	      	         dirty engines
- 	          reduce cloudiness or
- 	          increase precipitation
- Cloud             brighter clouds       sulfate smog         industry
- Condensation    less precipitation       smoke    		 fires
- Nuclei

## 2.6±0.3 W/m2

_**Past Climate**__:_ The presence of aerosol forcing can explain global warming of 0.6°C rather than 1.0°C in the last 150 yrs.
- Aerosol forcing is _30%-150%_ of greenhouse gases.
- Black carbon forcing is >1/2 of CO2 forcing

**Cooling****  ****Warming**

**2.6±0.3 W/m****2**

**1.8±1 W/m****2**

- Hansen & Sato, 2001

## Black Carbon Forcing

- In the last 1-3 years BC was recognized as a large though highly uncertain element of climate forcing.
- Control of BC could be an inexpensive route to mitigate global warming in the next 20-50 years without decreasing economical activity.
- Current climate models which incorporate BC are based on poor *in situ* measurements and have not been validated by global data.

**1989**

** ****2100**

**All aerosols contain black carbon**

**No aerosols contain black carbon**

**Predicted change in the radiative forcing due to black carbon**

**Hansen et al. [2000]**

## Aerosols also reduce precipitation

**Aerosols also reduce precipitation**
**Red**
** ****Large droplets.**** **
**Yellow-green**
** ****Smaller droplets due to pollution**
**(Rosenfeld personal comm.) **

## How do we measure aerosols?

**In situ measurements**
**Impactors**
**In situ probes attached to aircraft**
**Lidars**
**Ground based measurement**
**Sun photometers**
**Lidars (MPL net)**
**Space**
**Multi wavelength measurements (MODIS)**
**Multi angle measurements (MISR)**
**Polarization (POLDER)**
**Lidar (LITE, IceSat, Calipso)**

**Cimel  Sunphotometer CE 318-1 **

## MODIS aerosol over ocean

**large dust particles reflect in the whole spectrum**
**Smoke or pollution aerosol reflect mainly in the visible**

**visible**

**Mid IR**

**visible**

**Mid IR**

## Why Satellites?

**	****- *****short life time (a few days) vs. decades for greenhouse gases***
***	******- variations in source chemical properties***
***	******- regional impacts***

- Need to measure the global, daily distribution of aerosols, their properties & radiative effects

**Why Satellites?**

- EarthObservatory.nasa.gov

**MODIS, April,15, 2001**

**GOCART, April,15, 2001**

**MODIS, April,15±5, 2001**

## How can we measure aerosol absorption?Smoke and Dust show up in the UV

**Because small particles scatter at shorter wavelengths, they interfere with Rayleigh scatter and their absorption is very evident.  This allows smoke to be detectable in the UV.  For iron aerosols there is a strong UV absorption band so it is “visible” as well. This method is less sensitive below 2 km.**

**SeaWIFS**

**TOMS**

**Smoke**

**(false color)**

## How else can we measure Aerosol absorption?

- Below 2 km use the spectral measurements over the sun glint to derive the aerosol absorption optical thickness.

**Aerosol effect on sun-glint reflectance is weakly dependent on aerosol effective radius and refractive index but strongly dependent on the absorption and scattering optical thickness**

**Varying effective radius and refractive index**

**Varying Absorption Optical Thickness**

## Characterizing aerosols from space: What do we need to measure?

***Want to know***
** ****Size distribution**
** ****Composition**
** ****Optical thickness**
** ****Absorption**
** ****Aerosol height**

***Measure***
** ****Scattering at different wavelengths, multiple angles**
** ****Polarization, water vapor**
** ****Radiance**
** ****Glint brightness/ UV backscatter**
** ****Lidar backscatter/ O****2**** A band**

## Tropospheric Aerosol Measurements from Space

**NPOES AVHRR measurement of aerosols over the ocean**
**Nimbus 7 TOMS measurement of absorbing and non-absorbing aerosols**

**1980-90’s**

**Terra MODIS/MISR instruments yields global  fine and coarse aerosol over land and water**
**ADEOS POLDER provides first polarization measurements of aerosols from space**
** ****TOMS & AVHRR  record continues**

**Late 1990’s**

**CALIPSO provides aerosol height information - flies behind Aqua MODIS**
**Cloudsat gives cloud droplet information**
**Aqua MODIS continues Terra MODIS measurements**
** ****Aura OMI - continues the TOMS type aerosol measurements **
**PARASOL/ ADEOS II makes measurements of polarization using POLDER**

**2002-2010**

** ****AeroSat**
**Combined  multi-wavelength, polarization/ multi-angle/ hight resolution imagery with lidar mission and glint measurements of black carbon absorption**
** ****NPOESS Continued TOMS type aerosols using OMPS**
**NPOESS Continued MODIS type measurements using VIRRS**
**NPOESS polarization measurements with APS**

**2010-2014**

**What we Measured.**

**What we will measure.**

- O C O

## The Aqua/Aura Afternoon Constellation

**The Aqua/Aura Afternoon Constellation**

**The “A Train”**

**MODIS- Aerosols**
**CERES - Rad. budget**

**Aqua**

**1:30 PM**

**Cloudsat**

**PARASOL**

**CALPSO- Aerosol and cloud heights**
**Cloudsat - cloud droplets**
**PARASOL - aerosol and cloud polarization**

**CALIPSO**

**OCO**

**1:15 PM**

- 1:30 PM

**OCO - CO****2**** column**
**Oxy. A Band**

## What’s missing from the “A-Train”

**The A Train will go far to improve our understanding of aerosols.**
**The A Train will not be able to get absorbing aerosols.**
**Will see on and off the glint using POLDER, but..**
**POLDER will not be able to figure out the glint brightness variation due to changing sea surface state. **
**POLDER measurements of polarization are not as sensitive as APS measurements. **

**Spain and North Africa viewed by POLDER on ADEOS II**

**Visible**

**Polarized**

## Development of an Aerosol Mission

**Why develop an aerosol mission?**
**The “A-Train” cannot provide the needed measurements - especially black carbon**
**Aerosol forcing is changing rapidly (growing) - A-Train measurements will terminate around 2007-8**
**NPOESS measurements will be difficult to interpret without additional focused spaceborne measurements. **

## AeroSat Measurement Requirements (1)

**1) Science Question: What is the global distribution and composition of aerosols, especially black carbon?  How is it changing?**
**Measurement Requirements:**
**Aerosols**
- Distribution of the aerosol optical thickness of the fine and coarse mode
-  Effective radius of the aerosol fine mode, coarse mode
- Real refractive index of the fine mode
- Spectral absorption optical thickness derived over the sun-glint and sea shore
- Vertical profile of the fine and coarse aerosol (New with A Train)

## AeroSat Measurement Requirements (2)

**2) Science Question: How do aerosols affect weather and climate?**
**Measurement Requirements:**
**Aerosol Measurements from (1)**
**Earth Radiation Budget Measurements**
**Cloud Measurements**
- Cloud reflectance/albedo (±0.02)
- Effective droplet radius (±1 μm)
- Altitude distribution (±300m)
**Water vapor Measurements**
- Total precipitable water vapor
**3) What is the linkage to biomass burning?**
**CO measurements**

**AeroSat Baseline**

## AeroSat Measurement Strategy

**AeroSat payload will combine MODIS multi-wavelengths, MISR2 multi-angle, two EOSP (APS) polarimeters to provide a comprehensive evaluation of aerosol type and concentration       **
** ****Absorbing aerosol measurements (black carbon) can made using glint and off glint measurements.**
**A  CERES type instrument - radiation budget measurements.  **
**4 channel wide swath cloud camera - cross track EOSP cloud clearing and MODIS like aerosol retrievals over land and ocean.**
**Infrared measurements of cloud height and temperature - estimate the effect of aerosols on precipitation and cloud formation.**
**Aerosol heights**
**using O****2**** A-band spectrometer (wide FOV)**
** ****using aerosol/cloud lidar (narrow FOV)**
**AeroSat will fly in a sun-synchronous near-noon orbit to take advantage of the glint seen in the MISR2 cameras.**
**CO measurements from a MOPITT-like instrument**

## Proposed AeroSat Measurement Suite

**CORE measurements **
**1. Spectral imaging polarimeters**
**Two EOSP type instruments - along track and cross track scanning polarimeters with spectral range of UV to 2.1 micron and spatial resolution of preferable ~5-10 km. **
**2. Multi-angle spectral radiometer**
**MISR type instrument - along track multi angle with  spectral range of UV to 1.6 micron and spatial resolution of preferable 500m.  Nine camera angles to capture the sun-glint and off glint images.**
**3. Cloud camera system**
**High resolution cameras with resolution of 200m in the center of the swath with channels  at 0.47, 0.66, 1.65 and 2.1 μm**
**4. Cloud IR Measurement Instrument**
**Cloud measurements at 3.75, 8.5, 9.5 and 10.5 μm (COVIR type instrument)**
- 5**. Earth Radiation Budget Measurement**
**Measurement of aerosol and cloud changes in ERB (CERES instrument spare)**
**6. O****2**** A- band spectrometer for aerosol height**
- Wide swath aerosol and cloud height detection by O2 absorption
**ENHANCED ****measurement **
**7. Cloud and aerosol lidar system**
- Two wavelength polarized cloud lidar for aerosols and cloud height detection and particle type (CALIPSO/GLAS class), 300m vertical resolution
**8. CO Measurements from MOPITT 2**

## AeroSat Observing Geometry

- (Only 7 MISR camera views shown)

- Side view

**EOSP, B-Band Spect., Cloud Cameras, COVIR**
**crosstrack swaths**

**MISR2 swaths**

**MISR2 views**

**Sun Glint**

**EOSP, B-Band Spect., Cloud Cameras, COVIR**
** ****cross track**

**EOSP along track**

**Nadir**
**Lidar**

**EOSP along track swath**

- 3D  view

**CERES, MOPITT and Lidar**

**Crosstrack **
**CERES, MOPITT**

## AeroSat Data Analysis:

- 1. Aerosol scattering properties
- The spectral polarimetric measurements off the glint are used to derive the aerosol scattering optical thickness of the fine and coarse modes, effective radius of each mode and the real part of the refractive index

**Analysis of MODIS data of dust and pollution from East Asia in March 20, 2000. MODIS measures the optical thickness of the fine (green) and coarse (red aerosols (rightmost figure)**

**Aerosol Index from POLDER (ADEOS I)**

**AeroSat would make more accurate measurements of aerosol scattering properties**

## AeroSat Data Analysis:              3. Aerosol height

**AeroSat Data**** Analysis:              **3. Aerosol height
- Lidar backscattering attenuated coefficient in 2 wavelengths + MODIS/MISR/EOSP type spectral measurements will resolve the vertical distribution of fine and coarse aerosols.

**Analysis of Saharan dust over the Atlantic ocean**

**Flight Track**

## Summary of AeroSat Instruments and Possible Sources

**Core Payload**
**Polarimeters **
**2xEOSP (NASA-GISS or IPO - APS Instrument)**
**MISR-2 with modified wavelengths (NASA/JPL)**
**ERB instrument (CERES copy - already built)**
**4 Channel Cloud Camera (Industry - interest from Ham.-Suns.)**
**Cloud IR instrument (COVIR - IIP)**
**Oxygen A-Band Spectrometer (Industry A-Band - Spectrometers built by Ball for aircraft, proposed for CALIPSO and Cloudsat)**
**Enhanced Payload**
**Aerosol/Cloud Lidar (CALIPSO/GLAS design)**
**MOPITT-2 (Canada)**
**Total - 9 instruments**

## IMDC Study of AeroSat

**IMDC Study of AeroSat**

**Considered Baseline mission (Core+Enhanced) and descope mission (Baseline minus LIDAR)**
**Because of the power needs and size of lidar this was a suitable descope option**
**Used reduced GLAS instrument as baseline lidar**
**Looked at mission feasibility and costs assuming *****near noon orbit***
** **

- Bus

- ALI
- 5o tilt

- CERES

- MISR2

- EOSP-1
- Along track

- EOPSP-2
- Cross-track
- 40o tilt

- CLAer-CAM
- 40o tilt

- BBS
- 40o tilt

- COVIR

**Baseline Mission**

## Mission Characteristics

**Baseline Mission**
**705 km orbit, Sun-synchronous - near noon**
** ****3 year lifetime - 4 year goal**
**Controlled re-entry**
**Launch vehicle: Delta***
**Spacecraft yaws around every other day to maximize coverage**
**Modified catalogue spacecraft bus could be used (RSDO).**
**Mission cost ~ $370M including launch vehicle and contingency**
*** Payload is small enough - could be shared**

**Descope Mission (no lidar) ****Assumes that A-Band spectrometer can provide height information - increased science risk.**
**Uncontrolled re-entry **
** ****Launch vehicle: Taurus 2010XL**
**Mission cost ~ $310M including launch vehicle and contingency**

## Summary of AeroSat

**Goal - To provide improved global measurements of aerosol properties and information on the role of aerosols in climate. **
_**With the flight of AeroSat and continued Aeronet, aircraft , etc. measurements, along with models, we will significantly reduce the uncertainty in climate forcing  associated with black carbon absorption and aerosol scattering.**_
**AeroSat would be a 2010 follow on mission to “A Train” measurements of global aerosols**
**AeroSat would continue the global Terra/Aqua/CALIPSO/POLDER aerosol measurements in one mission**
**AeroSat would add improved aerosol polarization measurements providing risk reduction for NPOESS APS algorithm**
**AeroSat would be able to infer absorbing aerosol properties (black carbon) using the sun glint - **_**this would be a new measurement***_

## Rethinking Aerosat

**Mission could be better focused - probably too expensive**
**Need to develop a clear science requirements matrix**
**Some instruments are not at a high enough TRL (e.g. COVIR)**
***Current Thoughts***
**Why not use POLDER rather than 2xEOSP (APS)?**
**POLDER takes a “picture” of the ground**
**Duplicates MISR multi-angle (can see on glint/off glint)**
**Has polarization capability**
**Lacks 2.1 μ band and UV bands - could be added**
**Multi-angle radiation would duplicate CERES**
**Why not use VIIRS instead of cloud cameras and COVIR?**
**VIIRS is a “fixed priced IPO instrument”**
**Cloud screening capability (500m)**
**More wavelengths - similar to MODIS**
**Adds IR wavelengths for clouds**

## Revised Payload

**Aerosat Original Payload**
**2xEOSP**
**MISR**
**CERES**
**COVIR**
**Cloud Cameras**
**Lidar**
**A/B Band Spectrometer**
**MOPITT 2**

**Aerosat Revised Payload**
**POLDER B**
**APS**
**VIIRS**
**Lidar**
**MOPITT 2**

**Contributed by foreign partners **