ceilometer for the aerosol profiling: opportunities and limits

ACCENT Symposium Sept. 17-20,Urbino (Italy)

CEILOMETER FOR THE AEROSOL PROFILING:

OPPORTUNITIES AND LIMITS

Fabio Madonna, Ioannis Binietoglou, D’Amico Giuseppe, Gelsomina Pappalardo

Consiglio Nazionale delle Ricerche, Istituto di Metodologie per l’Analisi Ambientale (CNR-IMAA)

[email protected]


Lidar TechniquesRaman and HSRL: α+β with no assumption on the

lidar ratio S (only angstrom coefficient assumed with very low errors)

Advanced lidar technique (multi-wavelength)

Elastic: β using Klett or Fernald methods, assumption of S, constant throughout the profile.

Basic lidar technique: backscatter lidars and ceilometers (using ancillary measurements)

Advanced lidars


0

2

4

6

8

10

0.000 0.002 0.004 0.006

PEARL - Potenza, Italy, (40.60°N, 15.73°E), 20 April 2010, 21:00 - 23:05 UTC

355 532 1064

Back. Coeff.

(sr-1km-1)

Alti

tud

e a

.s.l.

(km

)

0.00 0.05 0.10 0.15 0.20Ext. Coeff.

(km-1)

0 60 120Lidar Ratio

(sr)

-2 0 2 4

b532

+b1064

b532

+b355

a355

+a532

Angströmexponent

0.0 0.2 0.4

Particle LinearDepolarization ratio

From multi-wavelenght Raman lidars it is possible to calculate secondary optical data:

Color ratios β(1064 nm)/β(532 nm)β(532 nm)/β(355 nm)α(532 nm)/α(355 nm)Lidar ratios (355, 532 nm)Ångström exponentsα-relatedΒ-related

Chacterization of whole uncertainty budget.

0

2

4

6

8

10

0.000 0.002 0.004 0.006

PEARL - Potenza, Italy, (40.60°N, 15.73°E), 20 April 2010, 21:00 - 23:05 UTC

355 532 1064

Back. Coeff.

(sr-1km-1)

Alti

tud

e a

.s.l.

(km

)

0.00 0.05 0.10 0.15 0.20Ext. Coeff.

(km-1)

0 60 120Lidar Ratio

(sr)

-2 0 2 4

b532

+b1064

b532

+b355

a355

+a532

Angströmexponent

0.0 0.2 0.4

Particle LinearDepolarization ratio


Moreover we can: ► Check whether these data make sense in the present scenario.

► Re-evaluate your data, if you find “strange“ results!!!

► In one word, “quality assurance”.

From multi-wavelenght Raman lidars it is possible to calculate secondary optical data:

Color ratios β(1064 nm)/β(532 nm)β(532 nm)/β(355 nm)α(532 nm)/α(355 nm)Lidar ratios (355, 532 nm)Ångström exponentsα-relatedΒ-related

Chacterization of whole uncertainty budget.

Advanced lidars

Werner

Ceilometers for aerosol profiling: potential world ceilometer network

ACCENT Symposium Sept. 17-20,Urbino (Italy)Courtesy of W. Thomas

Courtesy of W. ThomasACCENT Symposium Sept. 17-20,Urbino (Italy)

Ceilometers for aerosol profiling: potential world ceilometer network

Werner


… focus on Europe

From two independent measurements¥ Identification of scattering type (aerosol particles, cloud droplets, ice crystals, some aerosol type information)‡ A ceilometer is a single-wavelength, low-power lidar, with lower S/N ratio§ if calibrated[1] Estimate only# m > 2[2] Most Raman lidar systems operate

during night-time. 24h Raman lidar

systems exist and their operability has

been proved, however few systems

nowadays operate Raman channels also

during daytime; HSRL is independent of

daytime.

d= only daytime, n= only night time

Official Request for Provision of a Table of Capabilities and Accuracies of Detection Methods based on ICAO-IVATF/2 WP05

Ground-based Lidartechniques

Geo. propert

ies

a a S AOD å å type¥ Microphys. prop.

ceilometer‡ §

Ceilo+sun photo.

(d) (d)

Ceilo+sun photo.+ depol

(d)1 (d) (limited)

Backscatter lidar 1-λ

Backscatter lidar 1-λ + sun photo.

(d)1 (d)

Backscatter lidar 1-λ + sun photo.+ depol

(d)1 (d) (d) (limited)

Backscatter lidar m-λ♯

Backscatter lidar m-λ♯ + sun photo.

(d)1 (d) (d)1 (d) 1

Backscatter lidar m-λ♯ + sun photo.+ depol

(d)1 (d) (d)1 (d) 1

Ceilometer profiling… which products can be retrieved using a ceilometer…


Aerosol detection


Comparison of the arrival time of the first ash cloud over Europe on 16 and 17 April 2010 from ceilometer observations from the DWD ceilonet (circles) and from MCCM simulation (shading).The arrival times refer to 3 km height. The colours indicate thearrival times (6 h intervals, scale to the right). Black circles indicate sites without measurements, white circles that no ash cloud could be detected at this site.

Emeis et al.: The 16/17 April 2010 Eyjafjallajökull volcanic ash layer dispersion

Backscattering coefficientThis is the only product that can be inferred from ceilometer data. Several algorithms have been proposed and classified as:

→ FORWARD approaches: use a backscattering reference to calculate the calibration constant

PROS: ancillary co-located Raman lidar measurements only for short periods

CONS: only cloud free, periodic re-calibration, long time a veraging (~ 2 h)→ BACKWARD approaches: use ancillary estimation of lidar ratio or aerosol optical thickness (AOD)

PROS: use of ancillary measurements from sun photometer nephelometer (automatic and low-cost devices)

CONS: need for ancillary measurements of AOD (daytime), mainly in clear skies, long time averaging (> 2-3 h)


… potential discrepancies on various products not “easy” to be retrieved using a ceilometer

though using several assumptions…• Backscattering: > 10 - 20 % (Wiegner et al., 2012), but

need to checked over large datasets (calibration error highly relevant!)

• Extinction: > Backscattering discrepancy + lidar ratio assumption (even larger than 50 %)

• Effective radius: < 50 % using 4 backscattering profiles with σβ<10% (Veselovsky et al., 2008)

• Mass concentration: > Extinction discrepancy



Aerosol layeringPEARL 1064 nm ramge corrected

signalCHM15k 1064 nm ramge corrected

signal

He

igh

t (m

a.g

.l.)

7.5

6.0

4.5

3.0

1.5

0.0

u.a. u.a.

AOD532nm = 0.12

20 21 22 UTC 20 21 22 UTC

CT25k not sensitive to aerosol layers in the FT


Sensitivity: layer detection

Sensitivity: layer detection% of layers observed by MUSA lidar in 2010 at CIAO

Observatory (Potenza) but also detected by the ceilometer

- Above 5 km no sensitivity

- Nighttime < 5km, Day < 3km


0.0000000 0.0000002 0.0000004 0.0000006 0.0000008 0.00000100

50

100

150

200

250

Fre

qu

en

cy o

f occ

urr

en

ce

Attenuated backscattering (a.u.)

CHM15k 1064 nm MUSA 1064 nm

2000 < z < 4500 m

Attenuated backscattering


Frequency of occurrence of attenuated backscattering values for simultaneous observations performed by MUSA lidar and CHM15k ceilometer in 2010 at CIAO Observatory (Potenza)

► Only night time only observations.► Same vertical and time resolutions.► Differences below 2.0 km due to overlap and detection issues► Better agreement above 2.0 km

0.0000000 0.0000002 0.0000004 0.0000006 0.0000008 0.00000100

10

20

30

40


0 < z < 2000 m

Fre

qu

en

cy o

f occ

urr

en

ce


0.0000000 0.0000002 0.0000004 0.0000006 0.0000008 0.00000100

50

100

150

200

250

300


0 < z < 4500 m

Fre

qu

en

cy o

f occ

urr

en

ce


20002500

30003500

40004500

1E-6

1E-5

1E-4

1E-3

0.0000000

0.0000002

0.00000040.0000006

0.00000080.0000010

Atte

nuat

ed

back

scat

terin

g (a

.u.)

Ext

inct

ion

co

effi

cie

nt (

m-1

)

Height (m a.g.l.)

Beta vs Alfa vs Height


MUSA lidar observation, 2010, CIAO

355 nm extinction coefficient from MUSA

20002500

30003500

40004500

1E-6

1E-5

1E-4

1E-3

0.0000000

0.0000002

0.00000040.0000006

0.00000080.0000010

Atte

nuat

ed

back

scat

terin

g (a

.u.)

Ext

inct

ion

co

effi

cie

nt (

m-1

)

Height (m a.g.l.)


Beta vs Alfa vs HeightCHM15k ceilometer observation, 2010, CIAO


20002500

30003500

40004500

1E-6

1E-5

1E-4

1E-3

0.0000000

0.0000002

0.00000040.0000006

0.00000080.0000010

Atte

nuat

ed

back

scat

terin

g (a

.u.)

Ext

inct

ion

co

effi

cie

nt (

m-1

)

Height (m a.g.l.)


Beta vs Alfa vs HeightCHM15k ceilometer observation, 2010, CIAO

Lower values with increasing height and extinction (low SNR)



SummaryCeilometers show a good potential for aerosol profiling but they are limited:•Aerosol detection:

► promising in synergy with lidars and/or transport/chemical models.

•Aerosol optical and microphysical properties: ► backscattering coefficient only

•Aerosol layering in the lower tropopshere: ► feasible but sensitivity limited in the free troposphere

•Ceilometers as an aerosol observation technology ► improvements are needed for both the receiver and

detection parts

Ceilometers in network around an anchor station



ThanksAcknowledgements The financial support of European Commission grants RICA-025991 EARLINET-ASOS and 262254 ACTRIS, and the financial support of the national project “Programma Operativo Nazionale (PON) – Regione Basilicata 2000/2006” are gratefully acknowledged. This work has been also partially supported by the EU FP7 project WEZARD (Weather hazards for aeronautics) grant agreement no. 285050.

ceilometer for the aerosol profiling: opportunities and limits

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