Summary of GEO-CAPE Aerosol Working Group Progress

Members: Mian Chin, Pubu Ciren, Hiren Jethva, Joanna Joiner, Shobha Kondragunta, Alexei Lyapustin, Shana

Mattoo, Lorraine Remer, Omar Torres, Alexander Vassilkov, Jun Wang

GEO-CAPE Aerosol Working Group tasks, FY13Task Personnel

High priority tasks:

H1. Availability of aerosol retrieval at TEMPO pixel resolution with 1-km cloud masks

Lorraine Remer, Shana Mattoo

H2. Aerosol retrieval availability and product quality at TEMPO vs. GEO-CAPE pixel resolution with the cloud mask at the same pixel resolution

Omar Torres, Hiren Jethva, Shana Mattoo

H3. Feasibility of TEMPO-GOES-R synergistic retrieval: (a) expanded spectral range from UV (TEMPO) and IR (GOES-R), (b) with high resolution cloud mask (1-km GOES-R) for TEMPO, and (c) feasibility of two-angle retrieval

(1) NESDIS group: Shobha Kondragunta, Pubu Ciren

(2) GSFC group: Alexei Lyapustin

(3) UNL group: Jun wangH4. Feasibility of retrieving aerosol layer height with O2-B and O2-

bandsAlexander Vasilkov, Joanna Joiner

Medium priority tasks:

M1. Cloud contamination statistics for a variety of possible sensor resolutions, including TEMPO and GEO-CAPE

Lorraine Remer, Shana Mattoo

M2. Using 7-month GLI data to explore the GEO-CAPE capability: (a) build a database of surface reflectance at 380 nm, (b) retrieve SSA and aerosol height, and (c) identify aerosol types

Alexei Lyapustin, Omar Torres

High priority tasks• Can TEMPO achieve GEO-CAPE objectives by itself or by

TEMPO/GOES-R synergy?– Aerosol retrieval availability:

TEMPO will have 30-40% less retrieval availability then GEO-CAPE, unless the cloud screen criteria is much relaxed, which may increase AOD retrieval error

– Aerosol product quality: not clear, still under investigation

– Using GOES-R 2.1 μm channel to help TEMPO retrieve AOD at visible wavelength: Yes under certain conditions

• How much can be gained from 2-angle retrieval (GOES-R and TEMPO or GEO-CAPE)?– Combination of UV and Vis-IR provide more information for aerosol retrieval

• Can O2-B (688 nm) or O2- (628 nm) band be used to retrieval aerosol height?– Yes with O2-B, when AOD is above 0.2, SSA and surface reflectance are

known

GEO-CAPE vs. TEMPOGEO-CAPE TEMPO

Instrument resolution Better than 2x2 km, with 1x1 km cloud camera (2 spectral bands)

4.5x2 km

Aerosol product resolution 8x8 km (64-pixel) 9x8 km (8-pixel)

Temporal resolution 1 hour 1 hour

AOD precision 0.05 0.05

AAOD precision 0.02 0.03

Spectral range UV-Vis (+ NIR, CO channel) UV-Vis

AOCH Yes No

H1. TEMPO aerosol retrieval availability - Using MODIS cloud mask at 0.5 km

(Lorraine Remer, Shana Mattoo)

Regional statistics, 1x1 km (GEO-CAPE) and 4x2 km (TEMPO):

TEMPO would have about 55% of the retrievals that MODIS provides now

TEMPO will have 2/3 retrieval availability of GEO-CAPE (1x1 km)

H1’. Diurnal variation of “cloud-free” fraction with different pixel size

Cloud-free fraction can be significantly reduced at TEMPO pixel resolution especially in mid-day

Virginia (VA) Wyoming (WY) New Mexico (NM) Mexico (MX)

8-km

4-km

2-km

1-km

Diurnal variation of CLOUD-FREE fraction from 1-day data of August 12, 2010

Terra Aqua

4x2 km

H2. Aerosol retrieval availability and product quality at TEMPO and GEO-CAPE resolution (own cloud mask)

(Omar Torres, Hiren Jethva)

Using the same variability criteria, TEMPO would have only half coverage of GEO-CAPE on average with the most severe loss in the SW largely because of the variation of surface reflectance. The availability greatly increases with the relaxed criteria

Fraction clear sky1x1 km (GEO-CAPE)

Fraction clear sky4x2 km (TEMPO)

σ < 0.0025Fraction clear sky4x2 km (TEMPO)

σ < 0.005Fraction clear sky4x2 km (TEMPO)

σ < 0.01

σ < 0.0025

a b c

H2. Results – AOD relative quality

σ=0.0025 σ=0.005 σ=0.01

Comparisons between 8x8 km AOD product from “GEO-CAPE” 1x1 km (x-axis) retrieval and “TEMPO” 4x2 km (y-axis) retrieval with different cloud mask criteria for April 10, 2012:

From the preliminary results, it does not seem that the quality of AOD from more relaxed cloud mask (thus higher probability of cloud contamination) is worse than that from more strict cloud mask. More quantitative evaluation is in progress.

a b c

AOD 470 nm, 1x1 km AOD 470 nm, 1x1 kmAOD 470 nm, 1x1 km

AOD

470

nm

, 4x2

km

H3. TEMPO/GOES-R Synergy – (Shobha Kondragunta, Pubu Ciren) (a) Surface reflectance at 2.13 μm and cloud mask

GOES-R GOES-R remapped to TEMPO TEMPO

13 14 15 16 17 18 19 20 21 22 23 1 20

20

40

60

80

100

Pe

rce

nta

ge

of

da

rk p

ixe

ls

(%)

UTC TIME

TEMPO GOES-R (TEMPO) GOES-R

GOES-R (west) and TEMPO do not overlap over eastern part of US and Atlantic Ocean.

Synergic use of GOES-R is possible by providing surface reflectance at 2.13 μm for TEMPO aerosol retrieval over portion of eastern, middle and western part of U.S.

Observations in the early morning and later afternoon need to be avoided. Only hours close to noon time are favorable (for lambertian surface)

July 15, 2012, UTC=19:00

H3. TEMPO/GOES-R Synergy – NESDIS group: (b) GOES-R cloud mask for TEMPO

• MODIS 1Km cloud mask (MOD35) was mapped into GOES-R (West) first then remapped GOES-R to TEMPO Grid between latitude band (35°N to 45°N)

• Fraction of cloudy (confident and probably cloudy) pixels calculatedGOES-R remapped to TEMPO TEMPO

Cloud mask information from GOES-R observations seems to be sufficient for TEMPO

July 15, 2012

H3. TEMPO/GOES-R Synergy (Alexei Lyapustin)

Summer, July 11 Winter, December 2

120°W

105°W

75°W

120°W

105°W

75°W

SNR=10 SNR=30 SNR=10 SNR=30

Over dark surfaces, the 2.1m BRDF from GOES-R (East) model can be used for TEMPO aerosol retrieval regardless of TEMPO’s parking longitude

Over central-eastern USA, the AOT RMSE based on GOES-R BRDF is expected to be < 0.05 (at 0.47 m). Over western USA the error is larger

H3. TEMPO/GOES-R Synergy (Jun Wang)Angular Analysis of Vis/NIR sfc. Ratio and implication for

retrieving AOD

GOES-R470, 640, 860 nm

TEMPO/GEO-CAPE340, 380, 470, 640 nm

GOES-R + TEMPO/GEO-CAPE

75 60 45 30 15 0 15 30 45 60 75VZA (°)

75 60 45 30 15 0 15 30 45 60 75VZA (°)

75 60 45 30 15 0 15 30 45 60 75VZA (°)

azimuth6090

Azimuth

120

30

150

Azimuth6090

Azimuth

120

30

150

azimuth6090

Azimuth

120

30

150

0.80 0.85 0 0.95 1.0Degree of Freedom for retrieving AOD

Assuming that surface BRDF can be characterized with uncertainty of 20%, we found that strong synergy between two GOES-R and TEMPO/GEO-CAPE during the time when one of the sensor is viewing the Earth surface at the direction close to the Sun’s illumination angle.

TEMPO/GEO-CAPE UV wavelengths improves DOFs in AOD retrieval.

SZA = 40°

H4. Aerosol height from O2-B and O2-(Alexander Vasilkov, Joanna Joiner)

• Radiative transfer simulations – LIDORT code: line-by-line O2

absorption,), TOA radiance with Gaussian response, FWHM=0.5, 1.0

– Aerosol: 1-km thick layer at different plume top height of 1-10 km, AOD=0.2, 0.5, 1.0, SSA=0.8, 0.9, 1.0

– Surface albedo: A=0.05, 0.1

Simulated TOA spectral reflectivity

B-band

✔

SSA=1

If SSA is known, the aerosol plume height and optical depth can be derived from measurements of the band depth and continuum reflectivity at 686 nm

Conclusions• Spatially, TEMPO alone (4x2 km) will have lower retrieval

availability then GEO-CAPE (1x1 km) by 33% in the morning (10:30 am)

• Temporally, TEMPO will have reduced AOD retrieval availability in partial cloudy scene

• AOD quality from TEMPO and GEO-CAPE is still under evaluation• Synergy between TEMPO and GOES-R is very helpful in terms of

utilizing the extended spectral range for (1) retrieving AOD at visible wavelength and (2) increasing the degree of freedom for AOD and fine mode AOD retrievals

• O2-B band has promising sensitivity for aerosol height retrieval for both GEO-CAPE and TEMPO

Bottom line: GEO-CAPE measurement requirements, as defined in STM and studied by the AeroWG, are not 100% met by TEMPO alone.

However…

• GEO-CAPE objectives can be mostly met by the synergy among TEMPO and GOES-R– GOES-R: high pixel res, cloud mask, DT retrieval,

good for DT and ocean– TEMPO: bright surface, SSA– Combo: more aerosol retrieval

• Cloud screening: 1-km, 2-channel radiometer will much enhance the AOD retrieval from TEMPO. It could be studied.