Approaches to intercalibration/QA/QC and other network
aspects of AD-Net and SKYNET systems
Tomoaki Nishizawa*1,Y. Jin*1, Akiko Higurashi*1, Rei Kudo*2, Hitoshi Irie*3, KazuakiYasunaga*4, Masaki Katsumata*5, Keiya Yumimoto*6, ShokenIshii*7, Hajime Okamoto*6, Kaori Sato*6, Takashi Y. Nakajima*8*1National Institute for Environmental Studies (NIES), Japan, *2Meteorological Research Institute (MRI), Japan,*3Chiba University, Japan, *4University of Toyama, Japan, *5Japan Agency for Marine-Earth Science and Technology(JAMSTEC), Japan, *6Kyushu University, Japan, *7Tokyo Metropolitan University, Japan,*8Tokai University, Japan,

Contents of this presentation◎ Outline of calibration/QA/QC regarding the instruments of the
AD-Net and SKYNET that contributes to this EarthCARE validation◎ Summary and Comments on this theme
ESA UNCLASSIFIED – For ESA Official Use Only

2nd ESA EarthCARE Validation Workshop
25-28 May 2021 (online)Observation products used for validationObs. site

Lat
LonInstrument

Parameter

Tsukuba(Rural)*stopping36.05N
140.12E

MRHSRL𝝰, 𝝱, 𝝳, S: 355 (Night)
𝝰, 𝝱, 𝝳, S: 532 (Day & Night)
Attenuated backscatter: 355/532/1064 (Day & Night)

Hedo(Maritime)

26.87N128.25E

MRL𝝰, 𝝱, 𝝳, S: 355/532 (Night)
Attenuated backscatter: 355/532/1064 (Day & Night)

Sky
radiometer

AOT: 340, 380, 400, 500, 675, 870, and 1020 (Day)
Angstrom exponent (Day)𝝰, 𝝱, 𝝳, S: 355/532 (Night)
Attenuated backscatter: 355/532/1064 (Day & Night)

Toyama(Rural)

36.7N
137.1E

MRL

Fukuoka(RuralUrban)

33.52N
130.48E

MRL=>MRHSRL(2021~)

𝝰, 𝝱, 𝝳, S: 355 (Night)
𝝰, 𝝱, 𝝳, S: 532 (Day & Night) *2021~
Attenuated backscatter: (Day & Night)

Skyradiometer

AOT: 340, 380, 400, 500, 675, 870, and 1020 (Day)
Angstrom exponent (Day)

Koganei(Urban)

35.7N
139.48E

355 HSRL(2019~)

𝝰, 𝝱, 𝝳, S: 355 (Day & Night)
Attenuated backscatter: 355 (Day & Night)

Palau(Maritime)

7.34N
134.5E

MRL(2019~)

𝝰, 𝝱, 𝝳, S: 355/532 (Night)
Attenuated backscatter: 355/532/1064 (Day & Night)

RV Mirai(ocean)

Ocean

MRL

𝝰, 𝝱, 𝝳, S: 355/532 (Night)
Attenuated backscatter: 355/532/1064 (Day & Night)

AD-Net
NIES,Tsukuba, Japan

PMT(532nm)

KoganeiToyama Univ.,Toyama, JapanIo

dinilefter

APD(1064nm)

MRLMRHSRL(Fukuoka, Toyama, Hedo)(Tsukuba)*Cooperative stations without realtime data sharing✓2β(532,1064)+1δ(532) Mie lidar✓1α(532)+2β(532,1064)+1δ(532) Raman✓2α(355,532)+3β(355,532,1064)+2δ(355,532)
Raman (MRL)✓2α+3β+2δ Raman-HSRL (MRHSRL)✓ 1α(355)+1β(355)+1δ(355) HSRL

355nm HSRL
(Koganei)MRL data processing and calibrationCalibration

Optical Prop. retrieval
Attenuated backscatter βatn (7ch)

Measurements (7ch)
ΔT＝15min ΔZ＝6m (Elastic channel）
ΔT＝15min ΔZ＝7.5m (Raman channel）

ΔT＝15min ΔZ＝30m (Elastic, Raman）

Cloud layer detection(Use βatn at 1064nm)

Integration
ΔT＝15min ΔZ＝30m (Elastic, Raman）

Calibration
1064nmCalibrate signal using signal
scattered by cloud＊use 1064nm signal to detectcloud layer [Shimizu etal. 2004]
Geometrical form factor
Evaluate using measured Raman
signals and theoretically computed
Raman signals. [Xie etal 2008]

532/355nm
Calibrate elastic and Raman
signals using signals measured
under clean condition and signals
for aerosol free layer (around 6km).
Depolarization (off-line)
Calibrate using linear polarizer
sheet directed at a ±45°
(Freudenthalter etal. 2016)

Attenuated backscatter (7ch)
ΔT＝15min ΔZ＝30m (Elasctic, Raman)

Retrieval of Aerosol & Cloud
optical properties

Particle optical properties (POP)Moving average
ΔT＝±30min, ΔZ＝±60m✓Extinction（355,532)✓Backscatter (355,532,1064)✓Depolarization（355,532)[Nishizawa et al., JQSRT, 2017]

355nm HSRL
Specification of HSRL using a scanning interferometer
Laser

Injection-seeded, Q-switching Nd:YAG laser (Continuum Surelite I-10)

Wavelength

355 nmPulse energy

100 mJ

Beam div.

0.1 mrad (after x5 beam expander)

Repetition rate

10 Hz

ReceiverTakahashi µ-210 (Dia. = 21cm), Smaller telescope (Dia. = 5cm)

Field-of-view

0.5 mrad (21cm telescope), 1 mrad (5cm telescope)Interferometer

Michelson interferometer, FSR = 2.4 GHz Scanning speed: 1 Hz

Detector

Photomultiplier (Licel PM-HV-R9880)

Acquisition

160MSPS ADC (AVALDATA ADO-1616-STD)[Jin et al., OE, 2020]

355nm HSRL data processing and calibration
Measurements (Δt = 0.1s, Δz = 7.5m)
Pco, Pcr
PHSR
Mie / Rayleigh separation
Mie/Ray separation
Averaging (Δt = 5min, Δz = 30m)

ü Using scan data, profile data areseparated into Mie and Rayleighcomponents (here, data forcalibration such as aerosol-free data
is not required). [Jin et al. 2020]

αp, βp, δp, βatt
Depolarization (off-line)
Cloud layer detection

Moving average(Δt = ±5min, Δz = ±30m)

Particle optical properties (POP)αp, βp, δp

ü Calibrate co-pol/cross-pol using alinear polarizer sheet directed at a±45° (Freudenthaler et al. 2016)
Geometric form factor
ü Calculate the factor using rangecorrected signals and computed
attenuated backscatter profiles

SKYNET
Observation
sites

Skyradiometer

http://www.prede.com/

AOT, SSA measured by skyradiometer
Fukuoka, Japan (20 Mar. 2016) 380

SSAAOT500
870

380 500 870

Local time [JST]Skyradiometer (by Prede co, Japan)✓Sun-scanning sunphotometer✓Measured wavelengths:
315, 340, 380, 400, 500, 675,870, 940, 1020, 1627, 2200nm✓Data recorded every 10~15min✓Derived parameters:
AOT, Angstrom exponent, SSA,Size distribution, Refractive index

Skyradiometer data processing and calibration
Automated processing

OfflineLevel 1

Solar Disk Scan (SDS)

F, E(Θ) (3° ≤ Θ ≤ 30°), ΔΩ
R
τ
Improved Langley (IL)F, τ

Mok & Irie et al. (2018)
Irie et al. (2018)
Nakajima et al. (2020)

F0*daily F0 is estimated using datataken within several months.

-Direct irradianceF = F0exp(-mτ)-Diffuse irradianceE(Θ) ~ FmΔΩ[ωτP(Θ)]

F & E(Θ) (Θ ≤ 1°)
Uchiyama et al. (2018)*Disc scan measurement mode isscheduled once a week.

-Relative sky radianceR(Θ) = E(Θ) / FmΔΩ~ ωτP(Θ)

LangleyF, τF0Level 2Cloud screening

F, E(Θ) (Θ ≤ 160°), F0, ΔΩ

Khatri et al. (2009) (w/o global irradiance)
Smirnov et al (2000) (direct irradiance)
Estelles et al (2012) (direct irradiance)
Song et al (2014) (direct irradiance)τext, ω, m, V(r)ΔΩ*mountain
area

Final data

Mountain calibration activity◎Period: Oct. 27-Nov. 5, 2016
◎Place: Mauna Loa (MLO), Hawai’i, USA◎Purpose:
Direct calibration of the Chiba-U’s mastersky radiometer by the Langley method for
all channels, including cloud channels.

Summary and CommentsAD-Net
ü Calibration using operational data is performed regularly, however, calibration
measurement of depolarization is performed annually.
ü We strives to keep data quality through regular maintenance about a year
(replacement of consumables, alignment adjustment, polarization calibration, etc)
ü The status of the instrument is constantly monitored via the data sent over the network.
ü Data screening of products extracted by Raman lidar and HSRL observation is underconsideration.
SKYNETü Calibration using operational data is performed regularly.
ü We strives to keep data quality through regular maintenance (generally, about a year)(replacement of consumables, alignment adjustment, etc)
ü The status of the instrument is constantly monitored via the data sent over the network.
ü Intercalibration using “a master instrument” calibrated by the Langley method in
mountain observation has been conducted occasionally.
ü A data center (International SKYNET data center) is being constructed to aggregate all
skynet data, centrally analyze it, generate and publish standard products [Nakajima etal. 2020] (this standard products will be used for the EarthCARE validation). Data
screening of products is under consideration.

Simple relationship between solar disk and SVA

1.00°
0.53°

1.00°
0.53°

1.00°
0.53°

1.00°
0.53°

solar disk

scat. angle = 0.00°

scat. angle = 0.235°

scat. angle = 0.50°∆Ω = 2𝜋 1 − cos 𝜃 = 0.239 msr∆Ω: solid view angle
𝜃: half angle of circular cone (=1.00°/2)

scat. angle = 0.765°

Example of solar disk scan
Linear scale

Log scale

Scattering angle

Far lamp method: Experiments for Solid View Angle

Idea of Improved Langley method
𝐥𝐧 𝑭 = 𝐥𝐧 𝑭𝐓𝐎𝐀 − 𝒎𝝉
𝑭𝟎𝐥𝐧 𝑭 = 𝐥𝐧 2 − 𝒎𝝉𝒓𝑭∗𝟎 = 𝑭𝒓2 exp(𝒎𝝉)𝐥𝐧 𝑭𝒓2 = 𝐥𝐧 𝑭𝟎 − 𝒎𝝉𝐥𝐧 𝑭𝒓2 = 𝐥𝐧 𝑭𝟎 − 𝒎(𝝉𝐧𝐨𝐧6𝐚𝐞𝐫𝐨𝐬𝐨𝐥 + 𝝉𝐚𝐞𝐫𝐨𝐬𝐨𝐥 )𝐥𝐧 𝑭𝒓2 = 𝐥𝐧 𝑭𝟎 − 𝒎 𝝉𝐧𝐨𝐧6𝐚𝐞𝐫𝐨𝐬𝐨𝐥 − 𝒎𝝉𝐚𝐞𝐫𝐨𝐬𝐨𝐥
𝝉𝒔2
𝐥𝐧 𝑭𝒓 = 𝐥𝐧 𝑭𝟎 − 𝒎𝝉𝐧𝐨𝐧6𝐚𝐞𝐫𝐨𝐬𝐨𝐥 − 𝒎𝝎𝟏2𝐥𝐧 𝑭𝒓 + 𝒎𝝉𝐧𝐨𝐧6𝐚𝐞𝐫𝐨𝐬𝐨𝐥 = 𝐥𝐧 𝑭𝟎 − 𝒎𝝉𝒔𝝎yxExample of results: Improved Langley method

Evaluation of F0 derived by IL method
MRI (transfer)

MLO

3%

Normal Langley

Improved Langley (IL)