AerosolCloud Ocean Biology Mission ACOB

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Aerosol-Cloud Ocean Biology Mission (ACOB)

• M. Schoeberl NASA/GSFC
• C. McClain NASA/GSFC
• Contributions from D. Diner, L. Remer, J. V.
  Martins, P. Hildebrand, J. Welton, B. Blair, M.
  McGill, G. Jackson, M. Mischenko, D. Starr, P.
  Colarco, and a bunch of other people.

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What is ACOB?

• ACOB is a multi-user mission with two science
  goals
• Quantifying Aerosol-cloud interaction
• Determining Ocean Carbon Cycling and other
  biological processes
• Why two goals?
• Next generation ocean color measurements require
  precise estimation of the aerosol contribution to
  the backscatter radiation
• Precise aerosol measurements are of interest to
  the aerosol cloud community
• There are common science problems between the two
  communities
• Aeolian fertilization of the ocean
• Aerosol formation by DMS

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ACOB will addresses the aerosol science drivers
for the next decade
Climate forcing and hydrological cycle
Understanding the global significance and
physical processes underlying aerosol-cloud
interactions to reduce major climate uncertainty
(2 W m-2 globally) associated with aerosol
indirect effects Human health and biological
activity Associating changes in boundary layer
air quality with aerosol sources and particle
types, and quantifying aerosol impacts on human
and ecosystem health
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Previous groundwork toward development of
community consensus on a future aerosol mission
strategy
Progressive Aerosol Retrieval and Assimilation
Global Observing Network (PARAGON)
initiative Objective To outline an integrated
system for determining aerosol climate and
environmental impacts
NASA-wide aerosol strategy workshop,
Williamsburg, VA, 18-19 August 2005 Objective To
identify NASAs specific contributions to PARAGON
NCAR Workshop on Air Quality Remote Sensing from
Space, Boulder, CO, 21-23 February
2006 Objective To examine what observational
characteristics are required for the successful
use of satellite remote sensing to measure
environmentally significant pollutant trace gases
and aerosols.
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Aerosol measurement recommendations

• Recommendation for advanced satellite imagers and
  lidars to reduce indeterminacies in current
  aerosol microphysical property retrievals and
  adoption of a systems approach to the development
  of new satellite missions (PARAGON publications)
• Emphasis upon aerosol-cloud interactions in
  relationship to climate change and the hydrologic
  cycle, and the relative impacts of anthropogenic
  and natural aerosols on climate and air quality
  (Williamsburg and GSFC workshop)
• Understanding of the composition and size
  characteristics of atmospheric aerosols by means
  of multi-angle, spectropolarimetric, and
  stereoscopic-imaging techniques in conjunction
  with active (high spectral resolution lidar)
  measurements. (NCAR workshop)
• More recently, GSFC Workshop Nov 2006, emphasized
  the role of aerosols in precipitation

Critical advances are needed in the areas of
aerosol and cloud vertical profiling, horizontal
and vertical spatial resolution, global coverage,
identification of precipitation processes,
revisit time, and fusion of measurements to
reduce uncertainties and indeterminacies
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Evolution of aerosol/cloud research

• The current decade will demonstrate improvements
  in our ability to observe aerosols and their
  affects from space
• Terra Aqua Significant improvements in
  quantifying direct radiative impacts statistical
  inferences regarding aerosol effects on cloud
  properties major improvements in determining
  near-surface air quality over land (MODIS, MISR)
• A-Train - Aqua, Aura, CALIPSO, CloudSat, Glory
• OMI Best yet measurements of aerosols over
  bright surfaces 20 km resolution
• CALIPSO Measurements of aerosol backscatter
  very close to clouds - no swath
• Glory Major advances in aerosol
  characterization but with sparse coverage and
  resolution too coarse for observing cloud
  boundaries or intra-urban pollution - no swath
• CloudSat Impact of aerosols on cloud formation
  not aligned with CALIPSO - no swath
• What is missing from already-manifested missions
  in the 2015 time frame?
• NPOESS No vertical profiling information no
  multi-angle or polarimetric imaging for reducing
  aerosol uncertainties to climate-quality
  requirements
• EarthCARE Single-wavelength lidar limits aerosol
  microphysical characterization single-frequency
  W band radar has limited sensitivity to
  precipitation lacks comprehensive passive
  aerosol measurement
• No future missions have clear linkage to the
  hydrological cycle - especially impact on
  precipitation

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ACOB is the NAS ACE Mission

• Science Objectives The science goal of ACE is
  to reduce the uncertainty in climate forcing
  through two distinct processes described above.
  The first goal is to better constrain
  aerosol-cloud interaction. This goal is achieved
  by simultaneous measurement of aerosol and cloud
  properties by radar, lidar, polarimeter, and a
  multi-wavelength imager.
• Mission and Payload LEO, sun-synchronous
  early-afternoon orbit. The orbit altitude of
  500-650 km. The notional mission consists of
  four instruments
• A multi-beam cross-track dual wavelength lidar
  for measurement of cloud and aerosol heights and
  layer thickness
• A cross-track scanning cloud radar with channels
  at 94 GHz and possibly 34 GHz for cloud droplet
  size, glaciation height, and cloud height
• A highly accurate multiangle - multiwavelength
  polarimeter to measure cloud and aerosol
  properties (This instrument, would have a
  cross-track and along-track swath with 1 km
  pixel size.)
• A multi-band cross-track visible/UV spectrometer
  with 1 km pixel size, including Aqua MODIS, NPP
  VIIRS, and Aura OMI aerosol retrieval bands and
  additional bands for ocean color and dissolved
  organic matter.

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ACOB Measurement Strategy
Particle Ranges
In order to understand the interaction between
pollution, clouds and precipitation we need
measurements that are sensitive to the particle
distribution, cloud height and particle
composition. Following the measurement suite
pioneered by the A-Train, a combination of active
and remote multi-wavelength sensors is needed.
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Candidate Sensor System
Passive sensors
Multiangle imaging spectropolarimeter (UV-SWIR)
Global column-averaged aerosol amount, size
distribution, absorption, particle shape,
refractive index some height sensitivity
High frequency µ- wave radiometer (800 GHz - W
band) Cloud ice water content
Low frequency µ- wave radiometer (W - Ku band)
Cloud precipitation
Optical spectrometer (ORCA) Measurements of
biomass growth rates, organic and non-organic
suspended matter assessments, aerosol absorption
and size sensitivity
Active sensors
Next generation aerosol lidar Vertical profiles
of aerosol abundances and microphysical
properties with across-swath capability and/or
direct extinction-backscatter separability
Particle Ranges
Cloud profiling radar Vertical profiles of
droplet effective radius and vertical profile of
water phase, cloud base and top height,
precipitation rates
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ACOB Candidate Payload
It is unlikely we can fly both of these HQ has
asked GSFC and LaRC leads to discuss hybrid option
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Multi-beam Lidar
Uses wider swath cross-track observations to
improve aerosol and cloud parameterization in
mesoscale and global transport models by
providing multi-grid vertical profile data.
Provides increased swath coverage for formation
flight missions relying on combined lidar and
imager observations (e.g. ocean color).
Nadir vs. Cross-track Lidar Example
Forest fires in Quebec generate thick smoke
plumes transported to NE United States
Cross-track lidar example 500 km Sun Synch
Orbit 7 Fixed Lidar beams 0, 5, 10, 15
angles
Nadir-only lidar does not provide enough spatial
coverage for most aerosol plumes
Improved spatial coverage through complicated
aerosol plumes
MODIS AOD
MODIS AOD
Wider swath profiling over difficult ocean color
regions
nadir
Cross-track spacing on the order of aerosol plume
scales model grid sizes
Coherent aerosol time and space scales Average
5 hrs, 100 km Plumes 1 hrs, 30
km
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Polarimeters

• Three concepts
• MSPI JPL
• POLDER-A EOSP
• PACS

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APS and POLDER-A Combination

• The POLDER-A is a multi-channel multi-angle
  imaging photopolarimeter which will provide
• detailed and accurate aerosol and cloud
  retrievals with a 2-day global coverage
• Channels 443, 490, 670, 865 1370, 1650, 2130 nm
• The APS is a high-precision multi-channel
  multi-angle photopolarimeter which will provide
• continuation of the Glory APS climate record
• in-flight calibration of POLDER-A polarimetry
  and photometry
• improved and updated look-up tables for the
  POLDER-A retrievals.
• Channels 412, 443, 555, 672, 865, 910, 1378,
  1610, 2250 nm
• The idea behind the combination is that APS would
  make measurements along the track and those would
  be extended across the track by POLDER-A

APS
Polder A
APS angular scanning
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MSPI - Advanced MISR Instrument

• Multiple cameras with extended spectral range,
  polarimetry, and wider swath
• Synergistic use of multiple techniques reduces
  retrieval indeterminacies
• multiangle particle size, shape, retrievals over
  bright regions (deserts, cities)
• multispectral particle size (visible and SWIR),
  absorption and height (near-UV)
• nominal bands 380, 412, 446, 558, 650, 865,
  1375, 1610, 2130 nm
• polarimetric size-resolved refractive index and
  size distribution width
• nominal bands 650, 1610 nm

0.5 polarimetric uncertainty is a challenging
requirement for a wide field-of-view imager
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PACS - Passive Aerosol Cloud Suite
Cloud Scanner
Cloud-Aerosol Polarimeter
UV-VIS
NIR

• Thermal Imager
• ls 8550, 11030,12020nm
• X-track Swath 90dg (single imager)
• 2 Angles Nadir and Fwd 15dg apart
• Spatial resolution 1.2km at nadir

Rainbow Angles
Multi-Angle Views along track

• Specs for coarse resolution component
• ls (360?), 380, 410, 440, 550, 660, 870, 910,
  1230, 1380, 1550, 1640, 2100nm
• Polarization selected channels X all channels
• Along track MultiAngle views 9-20 angles all
  wavelengths 150 angles rainbow l (660nm)
• Wide Swath along and cross track

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PACS - Passive Aerosol Cloud Suite
Cloud-Aerosol Polarimeter
Cloud Scanner
UV-VIS
NIR
Pointing System
Detailed/High Resolution Cloud Microphysics

• VIS-NIR 660, 870, 940, 1230, 1380, 1550,1640,
  2100
• TIR 8550, 11030,12020nm
• Nadir Resolution VIS110m, TIR340m (less for
  larger array)
• Pointing Capability /- 60dg
• X-track FOV options 20dg
• Must be small size/mass for pointing

Specs for high resolution component
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OCEAN Color Radiometer (ORCA)
MODIS/OMI

• Type Passive radiometer
• Fore-optic Rotating telescope
• Aft-optic Grating and filter-based spectrometer
• Cross-track swath 60
• Approx. dimension 1 m3
• Measurement range 3171375 nm
• Measurement specifics 2 nm bandwidth ozone
  channel centered at 317 nm 45 nm spectral
  resolution 345 nm 800 nm (w/ 700 800 nm
  included for terrestrial applications) four 30
  to 50 nm wide bands between 865 1375 nm CCD
  arrays in 3 focal planes
• Ground resolution at nadir 1.1 km
• SNR requirements (based on 20 nm integrated
  bandwidths for 345 to 800 nm 30-50 nm bands
  _at_845-1400 nm gt1000 for 345 400 nm gt1500 for
  400 720 nm gt750 for 720 900 nm gt 400 for
  1000 1400 nm
• Global coverage 2 days

MODIS
OMI
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High Frequency µ-wave Radiometer

• Submillimeter/Millimeter (SM4) Radiometer
• Conical Scanning Imager with 1600 km swath
• 10-km spatial resolution gt 0.36? pencil beam
• 6 Receivers gt 12 Channels
• Vertical Dual Polarization at 643 GHz
• 183V, 325V, 448V, 643 VH, and 874V GHz
• Three-point calibration (hot, cold, space cold)
• Heritage MLS, CoSSIR, HERSHEL, MIRO

Earth
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Cloud Radar

• Products
• Cloud top height
• Microphysical profile information
• Particle phase/Glaciation height
• IWC and CWC
• Precipitation detection
• What we would like
• Swath as well as dual frequencies (W and Ka)
• Even a narrow swath will be hard due to narrow
  back scattering phase function
• Lower frequencies mean larger antenna
• More sensitivity to precipitation
• Sensitivity to low clouds (aerosols probably
  have more effect on them)
• (-30dBz)
• It is unlikely that the cloud radar can point
  more than 10º off nadir

New Strategy as with GPM and TRMM use a low
frequency radiometer to increase the
precipitation measurement swath
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Low Frequency µ-wave Radiometer (GMI)

• GMI Key Products
• Rain rates from 0.3 to 110 mm/hr
• Increased sensitivity to light rain over land
  and falling snow

CM1 would be a GPM daughter satellite

• GMI Key Parameters
• Mass (with margin)150 kg
• Power125 W
• Data Rate30 kbps
• Antenna Diameter1.2 m
• Channel Set
• 10.65 GHz, H V Pol
• 18.7 GHz, H V Pol
• 23.8 GHz, V Pol
• 36.5 GHz, H V Pol
• 89.0 GHz, H V Pol
• 166 GHz, H V Pol,
• 1833 GHz, V (or H) Pol
• 1838 GHz, V (or H)
• (166 and 183 GHz to have same resolution as 89
  GHz)

Same as HF radiometer
Ball Aerospace and Technology Corporation (BATC)
is developing GMI
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ACOB Two Spacecraft Observing Geometry
Orbit 650 km SS
ORCA
Multi-angle multi-wavelength polarimeter
Radiometers HF (Orange) LF (Purple)
Cloud Radar
Multi-beam Lidar
ORCA (120º)
Polarimeter Radiometers (90º)
Lidar (30º)
90º
Radar (20º)
20º
30º
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Next Steps

• Community driven STM and white paper
• IMDC studies of payload
• Cost estimates
• cheaper than the space station
• more near term than the human settlement of Mars
• HQ buy in

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Synergies between aerosol and ocean
ecosystem/biomass measurements
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ACOB and Climate

• ACOB will link the whole spectrum of particles
  from aerosols-clouds-precipitation to untangle
  the climate/aerosol impacts
• ACOB will provide simultaneous measurements of
  these key parameters within the same footprint.
• ACOB will quantify the ocean carbon cycling and
  the biological pump component