Ground based UV/vis observations A) History B) Basic...

Ground based UV/vis observations

A) History

B) Basic viewing directions

B) Spectroscopy

C) Radiative transport modelling

D) Results from different stations

Anfänge der Spektroskopie

Joseph von Fraunhofer (1787-1826)

„Ich fand mit dem Fernrohre fast unzählig viele starke und schwache vertikale Linien, die aber dunkler sind als der übrige Teil des Farbbildes; einige scheinen fast schwarz zu sein “

• erste große achromatische Objektive für Fernrohre• erste Verwendung von Beugungsgittern, erste absolute Wellenlängenbestimmung• Bestimmung der Position von 234 der über 500 von ihm gefundenen Linien im Sonnenspektrum; seine Benennung wird heute noch Verwendet

Von Joseph von Fraunhofer selbst koloriertes Sonnenspektrum, um 1814

Gustav Robert Kirchhoff

1824 - 1887

in Heidelberg:

1854 - 1874

Robert Wilhelm Bunsen

1811 - 1899

in Heidelberg:

1852 - 1899

1859, in Berichten der Preußischen Akademie der Wissenschaften: Über die Fraunhoferschen Linien:

Kochsalzdampf absorbiert auch dieselben von ihm emittierten Linien; diese sind mit den Fraunhoferlinien in der heißen Sonnenatmosphäre identisch.

Ozon Wirkungsquerschnitt

1880, Hartley:

UV Ozonabsorption

1882, Chappuis:

vis Ozonabsorption

1890, Huggins

Liniengruppe Spektrum des Sirius (langwellige UV Absorption des Ozon)

200 400 600 800Wavelength [nm]

1E-23

1E-22

1E-21

1E-20

1E-19

1E-18

1E-17

[cm

]

Hartley Hug

gins

Chappuis

310 330 3501E-22

1E-21

1E-20

1E-19

1925: Dobson-Spekrophotometer zur Messung der Ozonschichtdicke

300 310 320 330 340 350Wellenlänge [nm]

0E+0

1E-19

2E-19

3E-19O

3-Ab

sorp

tions

quer

schn

itt [c

m]

AB

CD

Dobson-Photospektrometer

Das Intensitätsverhältnis verschiedener Wellenlängenpaare hängt von der Ozongesamtsäule ab

1 Dobson Unit (DU) entspricht einer Säule von 10 µm unter Normalbedingungen

Typische Ozonschichtdicke:

350 DU (3.5 mm unter N.B.)

⎭⎬⎫

⎩⎨⎧

⋅⎟⎠

⎞⎜⎝

⎛+−⋅= ∫ ∑

l

si

ii dssII0

0 )()()(exp)()( λερλσλλ

Lambert-Beer-Gesetz :

σi: Absorptionswirkungsquerschnitt des i-ten Spurenstoffs

ρi: Konzentration des i-ten Spurenstoffs

εs: Streukoeffizient

=> Kenntnis der Absorptionswirkungsquerschnitte ermöglicht die Bestimmung von Spurenstoffkonzentrationen

Only absorption => direct inversion

IC

I'0

I3

I1

λ3λ2λ1

I0

Inte

nsity

[arb

. Uni

ts]

Wavelength [arb. Units]

σ3

σ1

σ2

λ3λ2λ1

σdiff

Wavelength [arb. Units]

Cro

ss s

ectio

n [a

rb. U

nits

]

Der Differentielle Wirkungsquerschnitt

Lambert-Beer-Gesetz:

I = I0 exp(- σ ρ L)

Problem: I0 meist unbekannt

Lösung: Separierung des Absorptionswirkungsquerschnitts σ in einen breit- und schmalbandingen Anteil:

σ = σb + σdiff

Das Prinzip der Differentiellen Optischen

Absorptions-Spektroskopie(DOAS)

460 480 500 520 540

Wellenlänge [nm]

Inte

nsit

t I(

)

O3-Absorption

NO2-Absorption

Meßspektrum

'differentielle'optische Dichte

250 300 350 400 450 600 650 7000

100200

Detection Limit

200 pptL=1km

1 pptL=16km

2 pptL=12km

20 pptL=12km

500 pptL=5km

5 pptL=5km

100 pptL=5km

200 pptL=5km

1 ppbL=5km

Phenol

Wavelength [nm]

04080

20 pptL=1km

50 pptL=1km

250 pptL=1km

para-Kresol

05

10

Toluol

01020

Benzol

0100200

IO

050 BrO

020 ClO

01

HCHO

0100 NO3

04

HONO

0

2NO2

048

SO2

0

4250 300 350 400 450 600 650

50 pptL=5km

σ'[1

0-19 c

m2 ]

O3

Differentielle Wirkungsquerschnitte verschiedener atmosphärischer Spurengase

Specialities for spectroscopy using extraterrestrial light sources

-Fraunhofer lines dominate the spectrum => a correction spectrum (Fraunhofer reference spectrum) is needed

-Analyses yield the difference between the trace gas absorptions of two observations

-Influence of Raman scattering => Ring effect

300 400 500 600 700 800Wavelength [nm]

0.0

0.5

1.0

1.5

2.0

2.5

Spec

tral I

rradi

ance

[W/m

2 /nm

]

GOME solar spectrum

Planck function for 5800K

Basic viewing geometries: Zenit

SZA

Direktlicht-Beobachtungen

Vom Zenit gestreute Intensität

Direct light:Sun, Moon, Stars-easy geometry-nightime measurements

Zenith scattered sun light:-sensitive to stratospheric trace gases

Spectrograph

Zenith

Sun

Stratosphere

Troposphere

45°

70°

80°85°88°

Scattered sun light in various viewing directions(MAXDOAS):-sensitive to tropospheric trace gases

400 500 600 700

Wavelength [nm]

Inte

nsity

[arb

itr. u

nits

]

spectra measured at different solar zenith angles

A: SZA=90 degrees

B: SZA=65 degrees

A / B:

C: reference spectrum O3

D: reference spectrum O4

Stratospheric DOAS-measurements Two measurements are needed to remove the Fraunhofer lines:

One measurement at low SZA (with weak atmospheric absorptions) and one at high SZA (with strong atmospheric absorptions)

Zenit

SZA



BrO

O3

O4

Residual

Atmospheric spectrum

Divided by Sun Spectrum

60 %

Ring Spectrum

7 %

7 %

0.3 %

0.2 %

1.2 %

2.2 %

Example of a DOAS analysis of scattered sun light (from satellite measurements)

Target species: BrO

440 460 480 500 520 540 560-0.05

-0.03

-0.01

0.01

0.03

365 370 375 380 385 390-0.061

-0.059

-0.057

-0.055

-0.053

365 370 375 380 385 390-0.005

-0.003

-0.001

0.001

Opt

ical

den

sity


-0.004

-0.003

-0.002

-0.001

0.000

0.001

O316.01..1997, SZA: 91.1°

NO218.03.97, SZA: 90.6°

OClO24.02.97, SZA: 91.1°

BrO26.02.97, SZA: 88.8°

O3

NO2

OClO

BrO

Examples of different trace gas analyses

(ground based measurements at Kiruna, northern Sweden)

Examples of the spectral fitting procedure of the different trace gases (data from the Kiruna instrument). Displayed are the absorption cross sections (red curves) scaled to the respective trace gas absorption in the measured spectrum (black curves).

Raman Scattering on Air Molecules (Ring effect)

Transitions for rotational and vibrational Raman scattering on O2 and N2 molecules

Auffüllen von (Fraunhofer-) Linien durch inelastischeStreuung (Ring-Effekt)

Im UV bis zu 10% optische Dichte

395 396 397 398 399Wavelength [nm]

intens

ity [a

rbitrar

y un

its]

earth shine spectrum

dirct sun light spectrum

Fig.Sample Ring spectrum (I(Ring)) calculated for the evaluation of UV spectra taken during ALERT2000. Shown is also the logarithm of the Fraunhofer reference spectrum(Imeas) used for the calculation. The spectrum was taken on April 22, 2000 at 15:41 UT at a local solar zenith angle of 70o and zenith observation geometry [Hönninger 2001].

The DOAS spectroscopy yields the integrated concentration along the light path

τ−⋅= eII 0Lambert-Beer‘s law:

=>

with:

=>

if concentration c is constant along light path:

∫ ⋅⋅==⎟⎠⎞

⎜⎝⎛ dsc

II στ0ln

∫ ⋅= dscSCD

στ

=SCD

scSCD ⋅=

Der 'Air-Mass-Faktor' (AMF)

Zenit

SZA

SCD: entlang des Lichtstrahls integrierte Spurenstoffkonzentration

VCD: entlang der Vertikalen integrierte Spurenstoffkonzentration

Quotient aus schräger und vertikaler Säulendichte:

AMF = SCD / VCD 1 / cos (SZA)


Zenit

SZA


The measured SCD is the difference between both measurements:∆SCD = SCDmess – SCDref

= VCD*AMFmess – VCD*AMFref

=> VCD = ∆SCD / (AMFmess- AMFref)

0 5 10 15 20 25AMF

0

5000

10000

SCD

O3[

DU

]

Fit: Y = 356DU * X - 454DU

O3-Langley-Plot

VCD = (SCDmess + SCDref) / AMF

SCDmess = (VCD * AMF) - SCDref

Slope => VCD

y-intercept => SCDref

Direct light observations

-light source: sun, moon or star

-direct light path, easy interpretation of the measurement

-complex instrumental set-up, tracking system

-night-time chemistry can be investigated

The AMF depends on the altitude of the trace gas profile

Direct light AMF for different (box) profile height

0

10

20

30

40

50

60

80 81 82 83 84 85 86 87 88 89 90

SZA

AM

F

251016263550geometric AMF

profile height(x km - x+1 km)

Stratospheric trace gas layer

Trop. trace gas layer


-2.0E-2

-1.8E-2

-1.6E-2

-1.4E-2


-2.0E-3

0.0E+0

2.0E-3

NO3

NO2

NO2-evaluation, Kiruna, 23.02.1994, LZA: 84.4°

NO NO2

N2O5

HNO3langsameGleichgewichte

schnellesGleichgewicht

Stickoxidgleichgewicht

Photolyse

Diurnal variation of Stratospheric nitrogen compounds

Diurnal cycle of reactive nitrogen compounds. For most observations N2O5 is accumulated during night and photolised during day. Under these conditions the NO2VCD during sunrise is systematically smaller than during sunset [Lambert et al., 2002].

1/25/94 04:48 1/25/94 16:48 1/26/94 04:48 1/26/94 16:48

0

1

2

3

4

VCD

NO

3 [1

013 m

olec

/cm

]

Kiruna, 25./26.Jan 1994

0

1

2

3

4

VCD

NO

2 [1

015

mol

ec/c

m]

VCD NO2 night

VCD NO2 day

Direct moonlight measurements

Zenith scattered sunlight measurements

0 10 20 30

0 4 8 12 16

0 4 8 12 16

SCD

NO

3

0 4 8 12

0 4 8 12AMF

Langley-plots for different profiles

pure tropospheric

50% tropospheric

25% tropospheric

10% tropospheric

pure stratospheric

For a mainly stratospheric profiles the measurements lie best on a straight line

Langley-plot for different absorption bands

O4 moon light observations, Kiruna, 1994

O4 absorption, direct moon measurements, Kiruna, 29.01.1994

-0.1

-0.08

-0.06

-0.04

-0.02

0

340 390 440 490 540 590 640 690

Wavelength [nm]

Opt

ical

dep

th

Spectrum 1: 29.01., 5:46 UT, LZA: 81.8°Spectrum 2: 26.01., 23:40 UT, LZA: 53.1°

2 4 6 8 10 12AMF

0.00

0.01

0.02

0.000

0.005

0.010

0.015

0.00

0.04

0.08

0.12

-0.01

0.00

0.01

0.02

Opt

ical

dep

th0.00

0.06

0.12

0.18

0.00

0.04

0.08

0.12

630 nm, slope: 0.0121269R-squared = 0.997629






Only little moon lightin the UV

Zenith scattered light observations

-simple instrumental set-up

-restricted during daylight

-high sensitivity for stratospheric trace gases

Spectroscopy of zenith scattered light

Vom Zenit gestreute Intensität

Radiative transfer modelling is required

Sensitivity:-is high for low sun (large solar zenith angle, SZA)

(sensitivity for stratosphere is higher than for direct light observations)

-depends on many parameters:-wavelength-concentration profile-aerosol profile-clouds

AMF for satellite observations (very similar to zenith scattered light observations)

20 30 40 50 60 70 80 90SZA [°]

0

4

8

12

AMF

albedo 0.8

albedo 0.0

stratospheric AMF

tropospheric AMF

geometric AMF

3D Monte Carlo RTM „TRACY“

di

ai

detector

Specific properties:

• spherical 3D geometry

• supports arbitrary platform positions and viewing geometries

• full MS by Rayleigh, aerosols, clouds, albedo

• Statistics of photon path can be derived,

e.g. average number of scattering events

vv,i

Instrument

Instrument

Green points indicate scattering points of photons => reception area of the detectorBackward Monte Carlo

modelling

Photon paths for different aerosol phase functions

Strong forward peak

Moderateforward peak

Suniti Sanghavi, IUP Heidelberg

Tim Deutschmann, IUP Heidelberg

Realistic modelling of microscopic cloud properties:

aerosol layer

aerosol layer

AMF calculation from radiative transfer modelling

1) The atmospheric properties for a given measurement (e.g. the SZA, the trace gas profile, etc.) are defined.

2) The intensity is modelled for two cases: with (I) and without (I0) the absorbing species. From the calculated intensities the corresponding optical density for the trace gas SCD is determined:

3) The ratio of this optical density and the absorption cross section for the selected trace gas absorption yields the trace gas SCD:

4) The trace gas profile defined in the first step is integrated to yield the respective VCD. The AMF is determined from the SCD and VCD according to the AMF-equation.

( )( )( )τ λλλSCD

II

= − ln0

( )( )SCD SCD=

τ λσ λ

Jan-01 Jan-02 Jan-03 Jan-04 Jan-05

Kiruna

Paramaribo

Neumayer

Arrival HeigtsMAXDOAS

Overview on the Heidelberg network of ground based DOAS stations. The instrument at Paramaribo (Suriname) was build and installed within the project.

Periods of successful measurements of the different stations. The Paramaribo measurements started in May 2002. In early 2003 the instrument at the Neumayer station was equipped with a MAXDOAS telescope. The light green colour indicates times when the Kiruna measurements were at part of the Kiruna instruments were not in operation

Instrumental set-up of the Kiruna instruments. The three spectrometers are mounted on a high table directly below the plexi-glass dome. The computer and the controlling devices are placed below.

The telescope lenses for the three spectrometers are mounted on a common frame over which a black shielding or a halogen lamp is automatically moved during night. These measurements are important for the calibration of the instrument and the correction of dark current and electronic offset (Bugarski, 2003).

4:48 7:12 9:36 12:00 14:24 16:48Zeit

0

4000

8000

SCD

O3

[DU

]

0

100

200

300

400

VCD

O3

[DU

]

O3-Auswertung

Opt

isch

e D

icht

e [

rel.

Einh

eite

n]

O3-Fitergebnis

Tagesgang, Kiruna, 11.03.1994

SCD O3

VCD O3

Diurnal cycle of reactive nitrogen compounds for two selected regimes. Left: for most observations N2O5 is accumulated during night and photolised during day. Under these conditions the NO2 VCD during sunrise is very similar to that around noon when the satellite overpass occurs. The NO2 VCD during sunset is, however, much larger. Right: during polar summer, only the fast photolysis of NO2 determines the diurnal cycle of NO2. The NO2 VCD during sunrise and sunset is systematically larger than at noon [Lambert et al., 2002].

400 405 410 415 420 425Wellenlänge [nm]

Opt

isch

e D

icht

e[r

el. E

inhe

iten]

NO2-Auswertung

7:12 9:36 12:00 14:24Zeit

0

10

20

30

SCD

NO

2[1

e15

mol

ec/c

m]

1.5

2.0

2.5

3.0

VCD

NO

2[1

e15

mol

ec/c

m]

Tagesgang, Kiruna, 26.02.1994

SCD NO2

VCD NO2

NO2-Fitergebnis

Mean annual cycle (1996 - 2001) of the stratospheric NO2 VCD analysed from GOME observations. Each pixel represents zonal mean values. The contour lines are in units of 1015 molecules/cm2 [Wenig et al., 2004].

0.0E+00

1.0E+15

2.0E+15

3.0E+15

4.0E+15

5.0E+15

6.0E+15

7.0E+15

8.0E+15

Nov. 96 Nov. 97 Nov. 98 Nov. 99 Nov. 00 Nov. 01 Nov. 02 Nov. 03 Nov. 04

Time

NO

2 VC

D [m

olec

/cm

²]

VCDReihe2Reihe3

Average NO2 VCD from SCIAMACHY at noonMAXDOAS NO2 VCD sunrise 90° SZAMAXDOAS NO2 VCD sunset 90° SZA

SCIAMACHY NO2 VCD © Andreas Richter

Time series of NO2 VCDs measured by the Kiruna instrument since December 1996. From 2002 to 2005 also the time series of average SCIAMACHY NO2 VCDs (within 200km, scientific product of the University of Bremen) are shown.

0.0E+00

1.0E+15

2.0E+15

3.0E+15

4.0E+15

5.0E+15

6.0E+15

7.0E+15

8.0E+15

Jan. 05 Feb. 05 Mrz. 05 Apr. 05 Mai. 05 Jun. 05

Time

NO

2 VC

D [m

olec

/cm

²]

VCDminReihe2Reihe3

Minimum NO2 VCD from SCIAMACHY at noonMAXDOAS NO2 VCD sunrise 90° SZAMAXDOAS NO2 VCD sunset 90° SZA


Time series of NO2 VCDs measured by the Kiruna instrument and minimum SCIAMACHY NO2 VCDs (within 200km, scientific product of the University of Bremen) for the first half of 2005. The SCIAMACHY NO2 VCDs are between the Kiruna AM and PM data probably indicating remaining low NO2 contributions from the troposphere.

SpectrographUV

SpectrographVisible

Meteorological Office Building

ElectronicsComputer

Telescope

Quartz glassfiber bundles

Observation platform

Top: Building of the meteorological service of Suriname in Paramaribo. The telescopes of the MAXDOAS instrument are seen at the top (see also Fig. 9). Bottom: The telescope units outside the building are connected to the spectrometers inside via glass fibre bundles.


0.0E+00

5.0E+14

1.0E+15

1.5E+15

2.0E+15

2.5E+15

3.0E+15

3.5E+15

4.0E+15

Apr. 02 Okt. 02 Apr. 03 Okt. 03 Apr. 04 Okt. 04 Apr. 05Time

NO

2 VC

D [m

olec

/cm

²]

VCDminReihe2Reihe3

Min NO2 VCD from SCIAMACHY at noonMAXDOAS NO2 VCD sunrise 90° SZAMAXDOAS NO2 VCD sunset 90° SZA

Time series of NO2 VCDs measured by the Paramaribo instrument and minimum SCIAMACHY NO2 VCDs (within 200km, scientific product of the University of Bremen) for the period 2002 – 2005.

....what has been ignored so far...

Polar Stratospheric Clouds over Kiruna (Sweden), ©Carl-Fredrik Enell.

Dynamical and photochemical development in the stratosphere during polar winter

Abun

danc

e

Time

Surface reactions

Gas phasereactions

ClONO2

HCl

ClO + 2 Cl2O2

Fall Early winter Late winter Spring

End of polar nightphotochemical ozone destruction

DenitrificationDehydration

CFC → Stratosphere → Reservoir compounds → active comp. → OClO(HCl, ClONO2) (Cl, ClO)

Ozone destruction

Transport hv (UV) PSC BrO

-5 .0E +13

0.0E +00

5.0E +13

1.0E +14

1.5E +14

2.0E +14

2.5E +14

3.0E +14

Jan. 00 Jan. 01 Jan. 02 Jan. 03 Jan. 04 Jan. 05

Tim e

OC

lO D

SCD

[mol

ec/c

m²]

R eihe1R eihe2K iruna O C lO D S C D A MK iruna O C lO D S C D P M OClO DSCDs over Kiruna for

different polar winters. High values were detected for the cold winters 1999/2000 and 2004/2005.

Volume of polar stratospheric clouds and Ozone loss for different Antarctic winters (© Markus Rex, see http://www.realclimate.org/). Strong ozone destruction was observed during the winters with high chlorine activation indicated by high OClO DSCDs over Kiruna

01.01

.9901

.02.99

01.03

.9901

.04.99

01.05

.9901

.06.99

01.07

.9901

.08.99

01.09

.9901

.10.99

01.11

.9901

.12.99

01.01

.0001

.02.00

01.03

.0001

.04.00

01.05

.0001

.06.00

01.07

.0001

.08.00

01.09

.0001

.10.00

01.11

.0001

.12.00

01.01

.0101

.02.01

01.03

.0101

.04.01

01.05

.0101

.06.01

01.07

.0101

.08.01

01.09

.0101

.10.01

01.11

.0101

.12.01

01.01

.0201

.02.02

01.03

.0201

.04.02

01.05

.0201

.06.02

80100120140160180200220240260280300320340

DOAS (84°<=SZA<=90°) DOAS (88°<=SZA<=94°) Ozone soundings TOMS

VCD

O3 [

DU

]

Date

01.01

.9901

.02.99

01.03

.9901

.04.99

01.05

.9901

.06.99

01.07

.9901

.08.99

01.09

.9901

.10.99

01.11

.9901

.12.99

01.01

.0001

.02.00

01.03

.0001

.04.00

01.05

.0001

.06.00

01.07

.0001

.08.00

01.09

.0001

.10.00

01.11

.0001

.12.00

01.01

.0101

.02.01

01.03

.0101

.04.01

01.05

.0101

.06.01

01.07

.0101

.08.01

01.09

.0101

.10.01

01.11

.0101

.12.01

01.01

.0201

.02.02

01.03

.0201

.04.02

01.05

.0201

.06.02

0

1

2

3

4

5

6

7

am pmVC

D N

O2 [

1015

mol

ec/c

m2 ]

Date

180

190

200

210

220

230

240

250

Temperature @

50hPa [K]

01.01

.9901

.02.99

01.03

.9901

.04.99

01.05

.9901

.06.99

01.07

.9901

.08.99

01.09

.9901

.10.99

01.11

.9901

.12.99

01.01

.0001

.02.00

01.03

.0001

.04.00

01.05

.0001

.06.00

01.07

.0001

.08.00

01.09

.0001

.10.00

01.11

.0001

.12.00

01.01

.0101

.02.01

01.03

.0101

.04.01

01.05

.0101

.06.01

01.07

.0101

.08.01

01.09

.0101

.10.01

01.11

.0101

.12.01

01.01

.0201

.02.02

01.03

.0201

.04.02

01.05

.0201

.06.02

0

1

2

3

4

5

6

7

8

9

10 am, SZA = 90° pm, SZA = 90° am, SZA = 94° pm, SZA = 94°

SCD

OC

lO [1

014 m

olec

/cm

2 ]

Date

-20

-30

-40

-50

-60

-70

PV @ 475K (PVU

)

DOAS- Messungen auf der Neumayer- Station/Antarktis © Udo Frieß

Long time series allow to investigate trends...

Monthly means NO2 slant column measurements at Lauder (45ºS, 170ºE). The right-hand scale shows approximate values for vertical column NO2 Figure courtesy of P. Johnston.

Effects of clouds I

-clouds change the colour of the sky

Example: influence of polar stratospheric clouds on the measured spectra

Colour index

Clouds make the sky more red88 90 92 94

SZA

0

4

8

12

Col

our i

ndex

January

March

blue

red

IICI =

Mie-Vielfach-Streuung

Spektrograph

Absorptionserhöhung durch BewölkungEffects of clouds II

-clouds enhance the light path inside the cloud

400 450 500 550 600 6500E+0

1E+6

2E+6

inte

nsity

[cou

nts]

1

2

3

Quo

tient

A /

B

400 450 500 550 600 650

0.97

0.98

0.99

1.00

1.01

1.02

Quo

tient

C /

Poly

nom

ial

400 450 500 550 600 650l th [ ]

O4

H2O

cloudy sky (04.02.1994, SZA: 85.4°)

clear sky (22.03.1994, SZA: 85.5°)

A:

B:

C = A / B2

1

7:12 9:36 12:00 14:24Zeit

0

300

600

[DU

]

0.0

0.0

0.1

OD

0.02

0.04

0.06

OD

0E+0

5E-4

1E-3

OD

0.00

1.00

2.00

Inte

nsit

tsqu

otie

nt 6

82nm

/ 38

8 nm

0E+0

1E+4

2E+4

3E+4

Aver

age

[1/s

]38

0-68

0 nm

VCD NO2

SCD H2O

Diff. SCD O4

Trop. O3Absorption

klarer Tag

05.03.1994

klarer Tag

05.03.1994

Colour-Index

Intensität

Thick cloud over Kiruna, 5.3.1994

The strongest absorption enhancement occurs when a very thick cloud waslocated over the measurement site (low intensity)

Multi-Axis Observation Geometry• Scattered light measurements

in different viewing directions (close to the horizon to the zenith)

• Zenith sky measurements are sensitive mainly to the stratospheric column

• Measurements close to the horizon have a long light path through the troposphere and are therefore sensitive for trace gases near the surface

• Multi-Axis DOAS allows to gain information on the vertical distribution of atmospheric trace gases

Spectrograph

Zenith

Sun

Stratosphere

Troposphere

45°

70°

80°85°88°

The path length through the boundary layer is mainly determined by the viewing angle of the telescopes.; from observations made at different viewing angles, the boundary layer trace gas absorption can be retrieved.

Three UV spectra on the CCD

Sophisticated MAX-DOAS setup with four independently moveable telescopes

Mini-MAX-DOAS

The whole spectrometer moves to the different elevation angles

On top of the Instituts für Umweltphysik, University of Heidelberg

Diploma thesis R. Sinreich, 2003

H2O DSCDs for the different elevation angles of the Paramaribo MAXDOAS instrument. The Highest values are found for the lowest elevation angles indicating that the bulk of the H2O column is located very close to the ground.

O4 DSCDs for the different elevation angles of the Paramaribo MAXDOAS instrument. In contrast to H2O, the DSCDs for the telescopes at 2° and 5° are very similar indicating that the O4 profile is not as closely located to the ground as the H2O profile. The scatter of the data indicates the presence of clouds.

NO2 SCDs analysed for the zenith telescope and for two telescopes with 2° elevation of the Suriname instrument for six days. The enhanced NO2 SCDs for the low elevation angles indicate substantial tropospheric NO2 concentrations.

MAX-DOAS observations at Milan, 2003Wagner et al., 2004

0.0E+00

2.0E+16

4.0E+16

6.0E+16

8.0E+16

1.0E+17

4:00 6:24 8:48 11:12 13:36 16:00

Time

SCD

HC

HO

[mol

ec/c

m²]

Reihe1Reihe2Reihe3Reihe4

Elevation:3°6°10°18°

0.0E+00

1.0E+17

2.0E+17

3.0E+17

4.0E+17

4:00 6:24 8:48 11:12 13:36 16:00

Time

NO

2 SC

D [m

olec

/cm

²]

Reihe1Reihe2Reihe3Reihe4

Elevation:3°6°10°18°

HCHO

NO2

10.09.2003

Different NO2 columns aremeasured fordifferent elevationangles

=> NO2 in thetroposphere

MAX-DOAS observations are sensitive to aerosols and clouds

Clear day with aerosols

The atmospheric O2 (and O4-) concentration is almost constant.

Changes in the measured O4 absorptions indicate variations in the atmospheric radiative transport

0

1000

2000

3000

4000

5000

6000

7000

14. Sep. 15. Sep. 16. Sep. 17. Sep.Date

O4 D

SCD

[1040

mol

ec2 /c

m5 ]

1.8

2.8

3.8

4.8

5.8

6.8

7.8Reihe1Reihe2Reihe3Reihe4Reihe5Reihe6

90°18°10°6°3°

Telescope elevation

O4 A

MF (reference added)

O4 DSCDs measured for different elevation angles of the southern telescope during four mostly clear days (September, 14 – 17, 2003) at Milan, Italy [Wagner et al., 2004]. The main effects are the general reduction of the observed O4 absorption and the decreasing difference between the low elevation telescopes (3°, 6°, 10°, 18°). This effects can be related to the increased aerosol load during the selected period. The zenith observations during the morning of September, 15 were affected by sporadic clouds and should not be taken into account for the detailed interpretation of the time series.

Modelled air mass factors for O4 without aerosol impact


Modelled air mass factors for an aerosol box profile: 2 km, Extinction coefficient: 0,05 km-1


Modelled air mass factors for an aerosol box profile: 2 km, Extinction coefficient: 0.25 km-1


Comparison with measurements (Heidelberg, July, 14, 2003)

Dots: measurements


Best agreement for anaerosol box profile:

2 km, Extinction coefficient: 0,05 km-1

The ratio of the NO2 SCDs at 2° and 20° is verysensitive to the profile height

Measured value: 6.03


Profile height [m]

Modelled

ratio of the NO

2 S

CD

at 2° and 20°

Box-AMF 1: Stratosphäre

AMF

5

2

1

1

1

20cn

SCDi = ci * zi * AMFi

c5

c4

c3

c2

c1

SCDges = ΣSCDi

Konzentration

Box-AMF 1: Stratosphäregroßer SZA

kleiner SZA

2

5

2

1

1

1

20

2

1.5

1

1

1

Konzentration Konzentration

Profilinformation aus Messungen bei unterschiedlichem SZA

Profilinformation aus Messungen bei unterschiedlichem SZA

SCD(SZA1) = ci * h * AMFi(SZA1) + cii * h * AMFii(SZA1) + …..

SCD(SZA2) = ci * h * AMFi(SZA2) + cii * h * AMFii(SZA2) + …..

SCDj AMFij ci= *

=> Profil ci aus Matrixinversion

Box-AMF 2: Troposphäre

kleiner Elevations

winkel

großer Elevations

winkel

2

2

2

2

3

4

2

aph

Zenith

Stratosphere

Troposphere

45°

70°

80°85°88°

2

2

3

6

15

Konzentration

Konzentration

Figure 1: Sketch of the instrumental setup. Here 2x5 lines of sight are shown. The scattered sunlight is observed using small telescopes and is lead to two spectrographs via quartz fibres. Here it is analysed and the spectra are saved on a PC.

Figure 2a: Pictures of the DLR-Falcon, including a sketch of the used lines of sights.Figure 2b: Typical image of vis CCD – the different viewing directions are separated from each other by dark lines. The numbers on the left side belong to the different LOS as marked in Figure 2a. Usually the direction -2° was the brightest one and therefore it has only very little space on the chip.

Klaus-Peter Heue, IUP Heidelberg

Time series of the vertical NO2 columns for AMAXDOAS Nadir and Zenith observations. In Nadir a strong enhancement is observed from 8:40 until 8:55. Here stratospheric AMFs were used, to show the slowly varying stratospheric signal and the influence of tropospheric pollution on the zenith viewing telescope.

Klaus-Peter Heue, IUP Heidelberg

Latitude

Longitude

12.512.011.511.010.510.09.59.0

Ostiligia

45.745.645.545.445.345.245.145.044.944.844.7

MI-Bresso

MI-Linate

Como

Pavia

LeccoAlzate

Rho

Saronno

Sannazano

SermidePorto Tolle

Mantova

20

10

0

-10

-20

2003.09.26 Nadir NO2 * 1015

Latitude

Longitude

12.512.011.511.010.510.09.59.0

Ostiligia

45.745.645.545.445.345.245.145.044.944.844.7

MI-Bresso

MI-Linate

Como

Pavia

LeccoAlzate

Rho

Saronno

Sannazano

SermidePorto Tolle

Mantova

20

10

0

-10

-20

2003.09.26 Nadir NO2 * 1015

Pundt et al., 2004

Imaging DOAS: 2-dimensional information

F. Hoffmann, IUP-Heidelberg

NO2-chimney plume,

Power plant ‚Fernheizkraftwerk‘ Heidelberg

F. Hoffmann,

IUP-Heidelberg

The whole route of Polarstern on ANT/XX in the year 2002/2003. The cruise started on 26.10.2002 and ended on 16.2.2003.

0.0E+00

1.0E+15

2.0E+15

3.0E+15

4.0E+15

5.0E+15

6.0E+15

-60 -40 -20 0 20 40 60

NO2 VCD [molec/cm²]

Latit

ude

morning NO2 VCD

afternoon NO2 VCD

Total VCDs of NO2 for the Atlantic traverse during May 2004 as a function of latitude. For all latitudes, PM values are clearly larger than the PM measurements.

1.5E+13

2.0E+13

2.5E+13

3.0E+13

3.5E+13

4.0E+13

4.5E+13

5.0E+13

5.5E+13

-70 -50 -30 -10 10 30 50 70

Latitude

BrO

VC

D [m

olec

/cm

²]

Polarstern BrO VCD AM 2004Polarstern BrO VCD PM 2004

Latitudinal mean VCDs of BrO in May 2005 for SZA between 84 and 86°.Compared to the values at 90° the BrO VCDs are substantially larger because ofthe photochemically reactivity of BrO.

Latitudinal cross section of the SCDs of H2O in the ANT/XX expedition [Halaisia, 2004]. The enhanced values of H2O in equatorial regions is because of the higher temperature of these regions (see Fig. 37).

Temperature distribution of ANT/XX cruise of Polarstern. The characteristic high temperature of the equatorial regions is shown with a maximumat 28 °C and the law temperature of the polar summer at –5 °C, the data is taken from the AWI internet site: www.ewoce.org.

Ground based UV/vis observations A) History B) Basic...

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