CALIPSO Ocean Products: ProgressAdvisors: Mike Behrenfeld and Chuck McClain

Ball Aerospace: Carl WeimerCNES: Jacques Pelon

NASA LaRC: Yongxiang Hu, Sharon Rodier, Chip Trepte, Bill Hunt

NASA NRC Postdoc Program: Pengwang Zhai and Damien JossetStevens Institute of Tech: Knut Stamnes

ODU: Richard Zimmerman and Victoria HillSAIC: Jim Koziana

Bigelow: William BalchHSRL and RSP instruments: Chris Hostetler and Brian Cairns

Supported by NASA HQ ocean biogeochemistry program and radiation science programPaula and Hal: Thanks!

Outline• CALIPSO lidar measurements: introduction

• Sub-surface particulate backscatter from cross-polarization profiling: progress

Highlight: a self-calibration method is developed for CALIPSO ocean subsurface lidar backscatter product (good for future trend analysis)

• Air-sea gas exchange velocity from lidar measurements of ocean surface mean square slope

• Other studies that supports ocean color program1. aerosol optical depth estimates without microphysics assumption 2. identification of smoke aerosols3. modeling and sensitivity studies with polarimeter measurements

CALIPSO and A-Train

CALIPSO: Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation

CALIPSO is 75 seconds behind Aqua, with MODIS, CERES, AMSR, …, onboard

CALIPSO PayloadThree Near Nadir Viewing Instruments

CALIOPCloud-Aerosol Lidar with Orthogonal Polarization

2 wavelength polarization sensitive lidar:

1064 nm, 532 nm (parallel and perpendicular)

Wide Field Camera (WFC)

High-resolution image (125m resolution)

Vertical profiles of atmosphere

Lidar Imaging Infrared Radiometer (IIR)

High-resolution image (swath product)

IIR

WFC

CALIOPLaser Transmitter

CALIPSO Payload

CALIOPReceiver Telescope

1 meter

Altitude Region

0.3 degree

Ocean Study Using Lidar in Space

• 532nm Cross-Polarization: Particulate Backscatter • 1064nm: Air-sea gas transfer velocity; wind

speed

• 532nm Co-polarization: aerosol correction

CALIPSO cross polarization channel ocean subsurface integrated backscatter (Lc)

Lc = (total lidar backscatter in water) / ( atmospheric two way transmittance)

total lidar backscatter in water = sum [lidar backscatter] (unit: 1/sr)

Atmospheric two way transmittance = exp (- 2* atmospheric optical depth)

Progress in lidar subsurface backscatter Study

• Self-calibration (solving daytime calibration issue): the new ocean subsurface CALIPSO backscatter is self-calibrated Lc = subsurface particulate backscatter / atmospheric twoway transmittance = theoretical Cox-Munk Reflectance (from CloudSat or AMSR-E) * [calib * uncalib subsurface signal] / [calib * uncalib ocean surface signal]

• Solving issues related to instrumentation new crosstalk correction (co-polarization vs cross polarization); cross-pol low-gain

change from Feb 2007; …

• Monte Carlo simulation of multiple scattering and its impact on the signal: significant contribution from multiple scatter; more going studies; needs help on characterizing particulate scattering phase matrix

CALIPSO sub-surface backscatter: 2007 and 2008

CALIPSO sub-surface backscatter: Night vs Day

No big problem with daytime:Self calibration worked!

CALIPSO sub-surface backscatter: MarAprMay vs SepOctNov

CALIPSO sub-surface backscatter: DecJanFeb vs JunJulAug

7m/s vs 11 m/s thresholds: impact of bubbles

V<7 m/s

V<11 m/s

7m/s vs 11 m/s thresholds: impact of bubbles

V<7 m/s

V<11 m/s

Link between Bbp and lidar cross-polarization

particulate backscatter Lc

Lc= (1+m)Bbp/(2beam)*[1-exp(-2beam H/(1+m))] *f(particle shape) *exp(-2beam H0/(1+m))

beam: beam attenuationm: multiple scatter contribution

Integrated lidar subsurface backscatter [Sum(Lc)] is proportional to (1+m)Bbp/beam

When (1+m)*(beam attenuation ) of a size bin is >>1, 1-exp(-2beam H/(1+m))]=1

Backscatter of individual vertical bin, Lc, of the profile is proportional to Bbp

when H is small and 1-exp(-2beam H/(1+m))= 2beam H/(1+m)Effective depth and backscatter profile product (under development): extra information help separate Bbp and beam

Validating Aerosol Correction using Ocean Surface Co-polarization Component

(HSRL: Sept. 04, 2007; from Chris Hostetler, John Hair, and others of the NASA LaRC HSRL group. Thanks!)

Comparison with MODIS(January 2007)

532nm optical depth from CALIPSO/AMSR 1064nm optical depth from CALIPSO/AMSR

550nm optical depth from MODIS

Identifying Absorbing Aerosols

Using Lidar Ratio (e.g. smoke: around 70) from Ocean Surface Backscatter

Effective Lidar Ratio = Beam Attenuation / Backscatter = [1-exp(-2)]/(2)]

Application of lidar measurements: gas transfer velocity

Ocean and the missing carbon sink

From Woods Hole Reserch Center Website

Atmospheric increase (3.2 PgC/yr) =Emissions from fossil fuels (6.3) + Net emissions from changes in land use (2.2)

- Oceanic uptake (2.4) - Missing carbon sink (2.9)

Combined with errors in partial pressure, the uncertainty of a factor of two in air-sea gas transfer velocity can lead to unacceptable error in global ocean flux of CO2 (Wallace, 1995)

CO2 Uptake = Air-sea Gas transfer velocity k x (660/Sc)n x solubility x (Pco2)

Application of lidar measurements: gas transfer velocity

Relation between carbon uptake and gas transfer velocitty

Air-sea gas transfer – wind speed relation : A source of uncertainty in Ocean Carbon Uptake

R.A. Feely, C.L. Sabine, T. Takahashi, and R. Wanninkhof, 2001: Uptake and Storage of Carbon Dioxide in the Ocean: The Global CO2 Survey, Oceanography, 14/4, 18-32.

CALIPSO mean square slope <S2> improves gas transfer velocity(Jahne et al 1984; Hara et al 1995; Bock et al 1999; Frew et al 2004, …)

wave slope variance correlates with gas transfer velocity better than wind speed and wind stress

Frew et al, 2004, JGR

0015.0

S1

2

660

k

Mean square slope <tan2> is directly measured by CALIPSO: ocean surface backscatter

Ocean Surface Backscatter = C* [ sec4/<tan2> exp(- 0.5 tan2/ < tan2> ]

C / <tan2> At 532nm and 1064nm, Fresnel reflection is valid for all surface waves

04/19/23

Carbon Uptake Comparison: F(Wind) (AMSR) vs F(<S2>) (CALIPSO)

Combined Active/passive:Modeling and Sensitivity Studies for ACE

1. Fast and accurate coupled ocean-atmospheric model for polarized radiative transfer

2. Sensitivity studies: how can polarization help

3. Objectives: using polarization measurements to help improve lidar data analysis

Model Description• A vector radiative transfer model has been

developed for a coupled atmosphere ocean system.• It is based on successive order of scattering method.• It converges fast for optically thin or absorptive

media.• Various state of art techniques have been employed

to enhance performance.• A reference can be found at:

Peng-Wang Zhai, Yongxiang Hu, Charles R. Trepte, and Patricia L. Lucker, "A vector radiative transfer model for coupled atmosphere and ocean systems based on successive order of scattering method," Opt. Express 17, 2057-2079 (2009) http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-4-2057

Sensitivity of Radiance and Degree of Polarization to Layer Depth

P PP

I1, P1: plankton layer at 10 m below surface

I2, P2: 50 m below surface

Unit of I1 and I2:

Wm-2m-1

Radiance and Degree of Polarization Sensitivity to Size

P PP1

Case 1:

effective size 1 m

Case 3:

effective size 30 m

Unit of I1 and I2:

Wm-2m-1

Summary and Discussion• Highlight: a self-calibration method is developed for

CALIPSO ocean subsurface lidar backscatter product (good for trend analysis)

• CALIPSO sub-surface integrated lidar backscatter (cross-polarization) is ready to release; depolarization ratio and vertical profiling of backscatter are still work in progress

• Preliminary study is done on the air-sea gas transfer velocity product

• ACE proof of concept: modeling and sensitivity studies of combined lidar/polarimeter for ocean color

HSRL lidar and RSP polarimeter flights over routes where

in situ measurements are available

Purpose: Learning from the success of ocean color vacarious calibration, we want to examine the potential of using several well defined targets (e.g. ocean surface) as the “moby” equivalent for lidar/radar and polarimeter

How: A few aircraft measurement flights supported by CALIPSO over various targets, in situ measurements of optical properties, and polarized radiative transfer modeling to assess how well we can understand those targets

Preliminary plan: flights this summer/fall near NASA Stennis and/or Langley (exact time and location to be decided: need your suggestions and collaborations on in situ measurements )

My email: yongxiang.hu-1@nasa.gov Phone: 757 864 9824