Download Spectroscopy in Atmospheric Science: Techniques, Relationships, and Trace Gas Processes and more Study notes Meteorology in PDF only on Docsity! Spectroscopy in Atmospheric Science • Spectroscopy used for many atmospheric science analytical questions – Solar spectroscopy • Direct absorption or scattering in atmosphere (e.g. DOAS) • Remote sensing from space (e.g. UARS, GOME, etc.) – UV-vis-IR absorption spectroscopy • e.g. for ozone, H2O, CO2, CH4, CO, etc. – Fluorescence spectroscopy • High specificity, sensitivity, and resolution lab studies • Increasing amount of field-based instruments for important atmospheric species, such as HOx, etc. • Very specific and sensitive technique(s) ! Absorbing molecule
co co co co co
HsO 2 2 2 2 2
Op | HO | 03 _H20 [O03 Heo | |,
TWHy +t odd t w + 4 +
100 T T T T T T TT T T T T T T
& 804
oO
2 607
Ss
— 407
wm
Cc
S 20+
_
0 T T T T T T T T T T T T T T
0 61 2 3 4 5 6 7 & 9 10 11 12 #139 #14 «+15
Wavelength/(um)
fq HE jel middle far 3
(a) infrared infrared infrared
VB = 667 cm
Vp = 667 om! Vag = 2349 emt
Bending modes Stretching modes
Figure 7.4 Representation of the two stretching modes and the two bending modes of
CO). For the stretching modes we indicated three different positions. The bending modes
correspond to two orthogonal planes, which are physically equivalent and therefore have
the same frequency
1H 376 | 1H 35¢C]
lll HL
2800 HM
P-Branch R-Branch
—
v Acm!)
Absorption
Ws
Figure 7.3 High-resolution vibrational-rotational spectrum of HCl. The lines appear in
pairs because the spectrum reflects the presence of both H*°Cl and H*’Cl in their natural
abundance ratio of 3:1. The AJ =0 branch is absent in these spectra. (Adapted and
reproduced by permission of Oxford University Press from [1], Fig. 18.14)
Figure 7.7 Schematic representation of the sequence of events leading to fluorescence,
triplet formation and phosphorescence. Note that the maximum in the fluorescence
spectrum again will correspond to the transition with the largest Franck—Condon factor
Standard N QO, fluorescence NO-instrument
SAMPLE &— (NO
I MODE)
TEFLON FLOVY
PARTICULATE NO SENSOR
FILTER Yr c MoDpEe
os
FILTER CAPILLARY yo P SOLENOID
! a ELECTRONICS
L
NO-NO
CONVERTER _ PRESSURE REACTION
I (NO, MODE) TRANSDUCER CHAMBER
! ey
DRYAIR ¢ i PMT bocvnnnnsne
&
FLOW CAPILLARY ;
SENSOR OZONATOR OPTICAL
FILTER
I CHAMBER PUMP
Standard Gas Filter Correlation infrared absorption CO-instrument
Modei 48CTL - FLOW DIAGRAM
Electronics
Preamplifier
Pressure
Transducer
IR Detector
sample (+
Sane
Gas Filter Wheel
Bandpass Filter
Infrared
Source
Chopper
Chopper Meteor
Flow
Sensor
Exhaust
Capillary
Purp
Trace Gas exchange processes • with soil only – NO, N2O, CH4, H2 • with soil – CO2, CO – NH3 – COS, H2S, DMS – (ozone) • with ocean – CO2, CO – VOCs – DMS, COS, etc. • with vegetation – CO2 – CO – ozone – VOCs (e.g. isoprene) – NO2, HNO3, etc. – COS, SO2 – alkyl-halides – NH3 – … -3 -2 -1 0 1 2 3 14:32:56 14:33:39 14:34:22 14:35:05 14:35:48 time w ( m s -1 ) Sonic anemometer time series 25 26 27 28 29 30 31 14:34:22 14:34:57 14:35:31 14:36:06 14:36:40 14:37:15 14:37:49 14:38:24 local time T ( d eg C ) -3 -2 -1 0 1 2 3 w ( m s -1 ) -2 -1 0 1 2 3 4 5 -3 -2 -1 0 1 2 3 w' (m s-1) T' ( K )
