Aerosol retrieval using modis data & rt code
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Transcript of Aerosol retrieval using modis data & rt code
PRESENT BY : MUHAMMAD FARIDZUL ADLI BIN ZAKARIA
PRESENT BY : MUHAMMAD FARIDZUL ADLI BIN ZAKARIA
Ahmad Mubin Wahab1 and Md. Latifur Rahman Sarker1, 2,*
1 Department of Geoinformation, Universiti Teknologi Malaysia,
Malaysia2 Department of Geography and Environmental Studies,
University of Rajshahi, Bangladesh.
*Corresponding author: [email protected]
1.0 β INTRODUCTION
PM 2.5
PM 10
Atmospheric aerosol is a
suspension of liquid and
solid particles, with radii
varying from a few nm to
larger than 100 Β΅m, in air.
Anthropogenic
Natural
Sources
WHAT IS
AEROSOL?
Sizes
Heart disease and stroke80%
Chronic obstructive pulmonary disease
14%
Lung cancer6%
0%
PREMATURE DEATH
1 - Human health Problems
asthma
hay fever
pulmonary inflammation
respiratory symptoms
Cardiovasculardiseases1 β PM enters to
respiratory system 2/3 β PM 10
trapped in
respiratory system
4 β PM 2.5 penetrates
deep into lungs
AEROSOL EFFECTS
2 - Visibility Degradation
Due to the extinction of light
when the light passing through
the atmosphere.
3 - Climate Change
Direct Effects
Indirect Effects
AEROSOL EFFECTS
Ground-based measurements Airborne-based measurements
Aerosol Robotic
Network
(AERONET)
Microstops II
Sunphotometer
Shipboard
measurement
Balloon Aircraft
Remote Sensing Satellite
Wide coverage Temporal resolution
Good spatial
information
Requires high spatial and temporal
resolution of data because of the short
life span of aerosol (7 to 10 days).
AEROSOL
MEASUREMENT
SATELLITE AEROSOL RETRIEVAL MECHANISM
Rayleigh reflectance
(ππππ²) + Aerosol
reflectance
Surface Reflectance (πππππ)
Top of Atmosphere
Reflectance (ππππ)
ππππ = ππππ« + ππππ² + πππππ
The key factor of the aerosol retrieval is to estimate surface reflectance
that attempts to differentiate the aerosol signal from surface.
ππππ« = ππππ β ππππ² β πππππ
PROBLEM & SIGNIFICANT
MODIS Local Scale Aerosol
Low spatial resolution (10 km)
Lots of missing pixels
No real-time data available
High Resolution (500 m)
Real-time data available
Good spatial distribution
Based on the local
aerosol model
To compare the potential of two different
AOT algorithms,
To determine which technique can provide
effective aerosol retrieval estimation.
STUDY AREA
One of the most densely populated area.
7 million people living in 1104 km2 of land areas.
Availability of Long-term
Ground data measurement
(AERONET station).
Several studies have already
been conducted.
One of the most polluted
urban areas in the world.
Availability of Long-term
Ground data measurement
(AERONET station).
Several studies have already
been conducted.
One of the most polluted
urban areas in the world.
Why Hong Kong?
DATA USED
MOD02HKM MOD03 MOD09GA
Aerosol Robotic
Network
(AERONET)
β’ MOD02HKM - swath data with calibrated radiance at 500m.
β’ MOD03 - Geolocation data (geodetic coordinates, ground elevation, solar zenith angle, solar azimuth angle, satellite zenith angle and satellite azimuth angle).
β’ MOD09GA - Land surface reflectance product at 500m.
β’ MOD05 - Total Water Vapour content.
β’ MOD07 - Total Ozone Content.
β’ MOD021KM β Channel 26 (cirrus reflectance).
β’ Additionally, MODIS aerosol level 2 collection 005 (MOD04 L2 C005) was used to compare with our result.
β’ AERONET Level 1.5 data was used for the validation.
2.0 β METHODOLOGY
OVERALL METHODOLOGY
AEROSOL REFLECTANCE (π¬πππ«)
TOA
REFLECTANCE
RAYLEIGH
REFLECTANCE
SURFACE
REFLECTANCE
TOTAL
TRANSMISSION OF
WATER VAPOUR
TOTAL
TRANSMISSION OF
OZONE GAS
π¬πππ« π,π½π,π½π,π =
ππππ π,π½π,π½π,π
π»π π΄,πΌπΆπ π»πΆπ π΄,πΌπΆπ
β ππππ² π,π½π,π½π,π βπ»πππ π½π,π½π ππ¬ π,π½π,π½π,π π»π―ππΆ
π π΄,πΌπ―ππΆπ β ππ¬ π,π½π,π½π,π ππ―ππ
π»π―ππΆπ π΄,
πΌπ―ππΆπ
TOTAL
TRANSMISSION OF
OTHER GAS
TOTAL
ATMOSPHERIC
TRANSMISSION
HEMISPHERIC
REFLECTANCE
TOA REFLECTANCE
π =π
(π+π.πππππ¨π¬(π«πΆπππ
πππ)
satellite receives TOA spectral radiance πΏπππ΄ π was normalized to the
solar illumination condition for each wavelength to generate TOAspectral reflectance using the equation as follows:
Band Wavelength (Β΅m) ESUN (Wm-2 ΞΌm-1)
1 0.646 1596
2 0.855 974.7
3 0.466 2017
4 0.553 1850
5 1.243 463.1
6 1.632 232.9
7 2.119 92.67π is earth-sun distance can
be calculated as following:
π is earth-sun distance can
be calculated as following:
ππ»πΆπ¨ π =π π³π»πΆπ¨ π π
π
π¬ππππ β ππππ½π
Source : MODIS Science Team
DOY β Julian daysDOY β Julian days
π½π is solar zenith angle,π½π is solar zenith angle,
π¬π is extraterrestrial solar
irradiance,
π¬π is extraterrestrial solar
irradiance,
where, π³π»πΆπ¨ π is TOA
spectral radiance obtained
from MOD02HKM data.
where, π³π»πΆπ¨ π is TOA
spectral radiance obtained
from MOD02HKM data.
π·πΉππ π =ππΉππ π . ππΉππ
π(ππππ½π. ππππ½π)
RAYLEIGH REFLECTANCE (π·πΉππ)
where, πππ ππ is cosine solar zenith
angle, and πππ ππ£ is cosine sensor
zenith angle.
where, πππ ππ is cosine solar zenith
angle, and πππ ππ£ is cosine sensor
zenith angle. ππππ² π = π. πβ π+ππ+ π π . ππ±π© β π π. π
Constant 0.2 β 0.5 Β΅m > 0.5 Β΅m
a 3.01577 x 10-28 4.01061 x 10-28
b 3.55212 3.99668
c 1.35579 1.10298 x 10-3
d 0.11563 2.71393 x 10-2
)πΈ = πΉ (π β πΉΖ is scattering
phase angle
Ζ is scattering
phase angle
Ζ = πππβπ(βππππ½πππππ½π + ππππ½πππππ½ππ
Wavelength (Β΅m) π π
0.466 0.02899 0.01471
0.553 0.02842 0.01442
0.646 0.02786 0.01413
Source : Butcholtz, 1995
Source : Butcholtz, 1995
πΉ is depolarization factorπΉ is depolarization factor
π is elevationπ is elevation π, π, π, πππ π ππ π ππ¦ππππβπ πππ‘π‘πππππ πππππππππππ‘π, π, π, πππ π ππ π ππ¦ππππβπ πππ‘π‘πππππ πππππππππππ‘
ππΉππ π is Rayleigh optical depthππΉππ π is Rayleigh optical depth
ππΉππ =π
π π + ππΈ[ π + ππΈ + π β πΈ πππ πΖ
ππΉππ is Rayleigh phase functionππΉππ is Rayleigh phase function
Total Atmospheric Transmission (π»πππ)
π»πππ(π½π,π½π) = π»πππ(π½π). π»πππ π½ππ»πππ(π½) = π»πΉππ(π) . π»πππ(π)
π»πΉππ(π) = πππ(βπ·πΉππ . ππΉππ . (π/ππππ½)) π»πππ(π) = πππ(βπ·πππ. ππππ . (π/ππππ½))
π·πΉππ =
π=π
π
πππΉππ. (π/ππππ½)β(πβπ) π·π¨ππ =
π=π
π
πππππ. (π/ππππ½)β(πβπ)
Coefficient Rayleigh Aerosol
ππ -0.44408 0.01176
ππ 4.49481 1.01682
ππ -9.71368 -2.32949
ππ 9.49795 2.11831
ππ -3.42016 -0.71737
Total Rayleigh Transmission (π»πΉππ(π) ) Total Aerosol Transmission (π»πππ(π) )
Source : Hoyningen-Huene et al., 2007
SURFACE REFLECTANCE (ππ )
An improvement of DDV techniques (more robust)
Empirical relationship (nonlinear relationship) between
visible channel and SWIR channel.
Calibrated by refining atmospheric correction algorithm
(6SV code).
An improvement of DDV techniques (more robust)
Empirical relationship (nonlinear relationship) between
visible channel and SWIR channel.
Calibrated by refining atmospheric correction algorithm
(6SV code).
πππππππ
https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mod09ga
πΌπΆπ β the total ozone content (obtained from the MOD07 level 2).
π΄β air mass factor (π΄ =1/ππππ½).
ππΆπ β weighting coefficient of ozone gases (derived from 6SV code).
π»πΆπ(π΄,πΌπΆπ) = πβπ΄π
πΆππΌπΆπ
πΌπ―ππΆ β total water vapour content (obtained from MOD05 level 2) .
π΄βair mass factor (π΄ =1/ππππ½). .
ππ―ππΆπ , ππ―ππΆ
π , and ππ―ππΆπ β weighting coefficients of water vapour (derived from 6SV code)
Total transmission of other gases (πͺπΆπ πππ π΅ππΆ)
β’ Only for the wavelength at 2.119 Β΅m.
β’ Obtained directly from 6SV code using the standard atmosphere model.
Wavelength (Β΅m) Gas Absorption Effect
0.466 O3
0.553 O3
0.646 O3 and π»2π
2.119 π»2π, CO2 and NπO
Total Gaseous Transmission
Total transmission of ozone gas (ππ3)
Total gaseous transmission of water vapour (ππ»2π)
π»π―ππΆ π΄,πΌπ―ππΆ = πππ[ππ―ππΆπ π΄πΌπ―ππΆ + ππ―ππΆ
π π³ππ(π΄πΌπ―ππΆ) + ππ―ππΆπ π΄πΌπ―ππΆπ³ππ(π΄πΌπ―ππΆ)]
Hemispheric reflectance
ππππ¦ is atmospheric optical depth (ππππ² + ππππ«).
ππ’ is polynomial coefficients of hemispheric reflectance.
ππππ¦ is atmospheric optical depth (ππππ² + ππππ«).
ππ’ is polynomial coefficients of hemispheric reflectance.
ππ―ππ =
π=π
π
ππ . πππππ Coefficient
Hemispheric
Reflectance
ππ 0.33185
ππ -0.19653
ππ 0.08935
ππ -0.01675
Source : Hoyningen-Huene et al., 2007
Integral of the bidirectional reflectance distribution function
(BRDF) over all viewing directions.
Crucial for surface function correction due to multiple scattering
effect.
Has a high influence on the bright surfaces, while less over low
surface reflectance.
Integral of the bidirectional reflectance distribution function
(BRDF) over all viewing directions.
Crucial for surface function correction due to multiple scattering
effect.
Has a high influence on the bright surfaces, while less over low
surface reflectance.
LOCAL AEROSOL MODEL CHARACTERIZATION
Identify number of cluster (k)Identify number of cluster (k)
VRC methodVRC method Wardβs methodWardβs method
Clustering Analysis
K-means clustering analysis
Local Aerosol Model
K-means
clustering
ANOVA Tables
Sum of F-test
values (ππ πΆπ)
ππ = π½πΉπͺπ+π β π½πΉπͺπ β π½πΉπͺπ β π½πΉπͺπβπ
Number of cluster (k)
(smallest value of ππ)
Hierarchical
cluster analysis
Agglomerative
procedures
Wardβs method
Elbow rule
Number of cluster (k)-based on the number of
step has biggest jump.
AOT RETRIEVE USING SBDART CODE
MODIS Aerosol Reflectance
(0.466 Β΅m, 0.553 Β΅m, and 0.646 Β΅m)
Local Aerosol Model parameters
SBDART code
Variables No. Parameters
Wavelength 30.466 Β΅m, 0.553 Β΅m,
and 0.646 Β΅m
AOT at
0.55 Β΅m9
0.0, 0.2, 0.4, 0.8,
1.4, 1.8, 2.2, 3.0,
and 5.0
SZA 9 0ΒΊ ~ 80 ΒΊ, Ξ = 10 ΒΊ
VZA 17 0ΒΊ ~ 80 ΒΊ, Ξ = 5 ΒΊ
PHI 18 0ΒΊ ~ 170 ΒΊ, Ξ = 10 ΒΊ
Aerosol
Model4
SSA, Qext, and g at
0.439 Β΅m, 0.676 Β΅m,
0.869 Β΅m, and 1.02
Β΅m.
TOA Reflectance as a function of AOT
Aerosol Reflectance as a function of AOT
Interpolation (Optimal spectral
shape-fitting technique)
No
AOT (0.466 Β΅m, 0.553 Β΅m, and 0.646 Β΅m)
AOT at 0.55 Β΅m
Yes
π₯2 =1
π
π=1
πππ΄πππ Ξ»π β ππ΄ππ
π Ξ»πππ΄πππ Ξ»π
2
π₯2 =1
π
π=1
πππ΄πππ Ξ»π β ππ΄ππ
π Ξ»πππ΄πππ Ξ»π
2
ΟAer(Ξ») = ΟTOA Ξ» β ΟRay Ξ»
AOT RETRIEVE USING DIRECT RETRIEVAL
MODIS Aerosol Reflectance
(0.466 Β΅m, 0.553 Β΅m, and 0.646 Β΅m)
Local Aerosol Model parameters
MIEV Code
Aerosol Phase Function as a
function of Scattering Angle
Interpolation(linear) with
MODIS scattering angle
AOT at 0.55 Β΅m (model 1)
AOT at 0.55 Β΅m (model 2)
AOT at 0.55 Β΅m (model 3)
AOT at 0.55 Β΅m (model 4)
Legendre coefficient π π =
π=π
β
ππ + π . ππ. π·π π
π β cosine scattering angle.
ππ β n-th Legendre coefficient.
π·π β n-th order of Legendre polynomial.
AOT retrieval
ππππ π =4ππ ππ£ππππ π
πππ ΞΈ
Ref. ind. real and imaginary, and effective
radius at 0.439 Β΅m, 0.676 Β΅m, 0.869 Β΅m, and
1.02 Β΅m
3.0 β RESULT &
DISCUSSION
VALIDATION OF MODIS AOT 500 M USING AOT FROM
AERONET STATION
R = 0.48RMSE = 1.47
R = 0.48RMSE = 1.47
R = 0.86RMSE = 0.56
R = 0.86RMSE = 0.56
R = 0.89RMSE = 0.09
R = 0.89RMSE = 0.09
SBDARTSBDART
Direct Model -1Direct Model -1 Direct Model -2Direct Model -2
R = 0.74RMSE = 0.99
R = 0.74RMSE = 0.99
Direct Model -3Direct Model -3
R = 0.77RMSE = 0.81
R = 0.77RMSE = 0.81
Direct Model -4Direct Model -4
Low accuracy against AERONET
AOT.
The accuracy varies with local
aerosol models.
It is because an improper account to
molecular effects in RT calculation
(Kokhanovsky & de Leeuw, 2009).
Low accuracy against AERONET
AOT.
The accuracy varies with local
aerosol models.
It is because an improper account to
molecular effects in RT calculation
(Kokhanovsky & de Leeuw, 2009).
High accuracy against AERONET
AOT.
Provide AOT with better
performance and less error.
It is because of RT code has the
ability to solve the complexity of RT
equations with rigorous computation
in order to minimize substantial error
(Kokhanovsky and de Leeuw, 2009).
High accuracy against AERONET
AOT.
Provide AOT with better
performance and less error.
It is because of RT code has the
ability to solve the complexity of RT
equations with rigorous computation
in order to minimize substantial error
(Kokhanovsky and de Leeuw, 2009).
DISCUSSION
SBDART code Direct retrieval
MODIS AOT 500 M VS MODIS AOT PRODUCT
MODIS AOT 500 M VS AERONET AOTMODIS AOT PRODUCT VS AERONET AOT
R = 0.94RMSE = 0.09
R = 0.94RMSE = 0.09
R = 0.90RMSE = 0.11
R = 0.90RMSE = 0.11
AOT Spatial Distribution
Comparison of spatial distribution of MODIS AOT 500 m and MODIS AOT product
MODIS AOT 500 m
Good spatial information
and high spatial resolution
(500 m).
No missing pixels aredetected.
Poor spatial information and
lower spatial resolution (10
km).
lot of missing pixel especially
in urban and industrial areas.
Due to bright pixels was
discarded in the retrieval
algorithm.
MODIS AOT product (10 km)
4.0 β CONCLUSION
CONCLUSION
MODIS AOT generated from SBDART code (RT code)
agrees very well with the AOT from AERONET
measurement.
It showed better accuracy and small error compared to
MODIS AOT generated from direct approach.
Considering the reasonable accuracy, high spatial
resolution and good spatial distribution, it can be
concluded AOT is possible to be estimated from MODIS
500m using RT code.
MODIS AOT generated from SBDART code (RT code)
agrees very well with the AOT from AERONET
measurement.
It showed better accuracy and small error compared to
MODIS AOT generated from direct approach.
Considering the reasonable accuracy, high spatial
resolution and good spatial distribution, it can be
concluded AOT is possible to be estimated from MODIS
500m using RT code.