Lab12.

Introduction to CALIPSO products

CALIPSO: http://www-calipso.larc.nasa.gov/

CALIPSO Data User's Guide:

http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/

Browse Image Tutorial:

http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/browse/index.php

Data Availability

http://www-calipso.larc.nasa.gov/tools/data_avail/

What is a CALIPSO?

• CALIPSO: Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

• Three co-aligned instruments:

– 3-channel lidar (CALIOP) : 532 nm (ll, ᅩ), 1064 nm

– Imaging IR radiometer (IIR)

– Wide-field camera (WFC)

• Launch: April 28, 2006

• A-train constellation

– Orbit: 705 km, in formation with Aqua, CloudSat, Parasol, and Aura

– TERRA crosses the equator at approximately 10:30 a.m., local time (about 3 hours before Aqua)

Approx equatorial crossing times

AIRS/AMSU-A/HSB

AMSR-R

CERES

MODIS

CPR CALIOP

IIR

WFC

POLDER HIRDLS

MLS

OMI

TES

CALIPSO and A-Train

CALIPSO payload:

• polarization-sensitive, two-wavelength lidar (CALIOP)

• three-channel (8.65, 10.6 and 12.05 microns) Infrared Imaging Radiometer (IIR)

• visible channel Wide Field Camera (WFC)

Polarization-sensitive, two-wavelength lidar (CALIOP)

Etalon

532

Polarization

Beam Splitter

|| +

1064

532

Interference Filter

Laser

Backscatter

from

Clouds/

Aerosols

Detectors and

Electronics

Depolarizer

(Calibrate)

Transmitter

• Two-wavelength (532 nm and 1064 nm)

polarization-sensitive lidar

• Has three receiver channels: one measuring the

1064-nm backscattered intensity, and two channels

measuring orthogonally polarized components

(parallel and perpendicular to the polarization plane

of the transmitted beam) of the 532-nm

backscattered signal.

• Footprint at the Earth's surface (from a 705-km

orbit) of about 90 meters and vertical resolution of

30 meters (actual nominal resolution ~15 m vertical

and 333 m horizontal)

CALIPSO lidar spatial and temporal coverage

• 532 nm total attenuated backscatter, km-1 sr-1

(Level 1B data)

1 day coverage area, Cover whole area: 16 days

Footprint (70m) spacing: 333 m (1 km~3 points)

70 m

333 m

Cover whole area: 16 days

Ground Track on Day 1

CALIPSO data:

• CALIPSO data product description:

http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/data_summaries/

• CALIPSO data products are available from the Langley DAAC (http://eosweb.larc.nasa.gov/).

Data products are grouped into the following categories:

• LIDAR level 1, level 2, and level 3 products

• IIR level 1 and level 2 products

• WFC level 1 products

Total Attenuated Backscatter at the 532 nm (Level 1, 1B profile) is one of the primary lidar Level 1 data products. It is the

product of the 532 nm volume backscatter coefficient and the two-way optical transmission at 532 nm from the lidar to the sample

volume. The attenuated backscatter profiles are derived from the calibrated (divided by calibration constant), range-corrected, laser

energy normalized, baseline subtracted lidar return signal.

“Total” means the combined signal from molecular, aerosol and/or cloud backscattering.

The 532 nm attenuated backscatter coefficients are reported for each laser pulse as an array of 583 elements that have been

registered to a constant altitude grid defined by the Lidar Data Altitude field.

Note that to reduce the downlink data volume, an on-board averaging scheme is applied using different horizontal and vertical

resolutions for different altitude regimes, as shown in the following table.

Level 2 products

(http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/data_summaries/layer/index.php)

CALIPSO Cloud and Aerosol Layer Products have two tightly coupled data types: column properties and layer properties

Column properties describe the temporal and spatial location of the vertical column (or, for averaged data, curtain) of atmosphere being

sampled. Column properties include satellite position data and viewing geometry, information about the surface type and lighting

conditions, and the number of features (e.g., cloud and/or aerosol layers) identified within the column. For each set of column

properties, there is an associated set of layer properties.

Layer properties specify the spatial and optical characteristics of each feature found, and include quantities such as layer base and top

altitudes, integrated attenuated backscatter, layer-integrated volume depolarization ratio, and optical depth.

Clouds and aerosol products are reported separately.

The layer products are generated at three different spatial resolutions.

• The 1/3 km layer products report cloud detection information obtained at the highest spatial resolution of the lidar: 1/3 km

horizontally and 30-m vertically. Due to constraints on CALIPSO's downlink bandwidth, this full resolution data is only available from

~8.3 km above mean sea level, down to -0.5 km below sea level.

• The 1 km layer products report cloud detection information obtained at a horizontal resolution of 1 km, over a vertical range extending

from ~20.2 km above mean sea level, down to -0.5 km below sea level.

• The 5 km layer products report (separately) cloud and aerosol detection information on a 5 km horizontal grid. At present there is no

separate stratospheric data product. Stratospheric features are recorded in the 5 km aerosol product.

CALIOP Browse Image Tutorial

http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/browse/index.php

LIDAR BROWSE IMAGES

http://www-calipso.larc.nasa.gov/products/lidar/browse_images/production/

LIDAR BROWSE IMAGES [V3-01]

http://www-calipso.larc.nasa.gov/products/lidar/browse_images/show_calendar.php

Lidar equation (Lecture 14)

where C is the lidar constant (includes Pt, receiver cross-section

and other instrument factors);

kb/4p (in units of km-1sr-1) is called the backscattering factor or

lidar backscattering coefficient or backscattering coefficient;

ke is the volume extinction coefficient; and

tp is the lidar pulse duration (h=ctp)

))(2exp(42

)(2

rdrkkh

R

CRP e

R

o

br

p

Attenuated backscatter

(CALIPSO product)

Illustration of the adaptive threshold technique (profile measured by LITE)

http://www-calipso.larc.nasa.gov/resources/pdfs/SPIE_5575-4.pdf

CALIOP retrievals: concepts of “feature” and feature boundaries

The term “feature” describes any extended and contiguous region of enhanced backscatter signal that rises significantly above the expected molecular (Rayleigh)

value (that is, clouds, aerosol layers, and surface returns).

A feature finding algorithm is required to separate the genuine features from noise (see CALIOP SYBIL algorithm)

Example of analysis of space lidar data:

(a) scene measured by LITE;

(b) single-shot profile showing thin cirrus and aerosol layers;

(c) as in b, but averaged to a 20-km horizontal resolution;

(d) single-shot profile showing strong cirrus overlying stratus;

(e) single-shot profile showing thin stratus overlying PBL aerosols.

http://www-calipso.larc.nasa.gov/resources/pdfs/SPIE_5575-4.pdf

Desert dust Biomass

smoke

Cirrus

56.71 32.16

47.85 28.57

39.92 25.78

31.94 23.46

23.93 21.42

15.90 19.55

7.81 17.77

-0.23 16.05

-8.28 14.23

-16.31 12.56

-24.33 10.69

-32.32 8.64

-40.27 6.30

Alt

itu

de,

km

A

ltit

ud

e, k

m

Alt

itu

de,

km

Fire locations in southern

Africa from MODIS, 6/10/06

CALIPSO Data – All Three Lidar Channels

Ratios of Channels give estimate of particle size, particle shape, and differentiate water/ice clouds

EXAMPLE: Integration of CALIPSO and MODIS

Hurricane Bill nears Cuba in 2009

EXAMPLE: Integration of CALIPSO and CloudSat