PTR-MS – PTR-TOF-MS€¦ · PTR-TOF-MS and PTR-MS for a nominal mass (i.e. compound), but much...
Transcript of PTR-MS – PTR-TOF-MS€¦ · PTR-TOF-MS and PTR-MS for a nominal mass (i.e. compound), but much...
PTR-MS / PTR-TOF-MS VOC fluxes during NOMAADS
NCAR, NOAA, NILU, UIBK
PTR-MS
)(
)(1][
3
OHcps
VOCHcps
tkVOC
Proton transfer reaction
Calculation of the neutral concentration
OHVOCHVOCOH k
23
Target compounds: Isoprene, isoprene oxidation products
PTR-MS
• Slides into 1 bay of C-130 rack
• 2nd bay needed for additional options: i.e. inlet pump, calgas
• HIMIL inlet on C-130 requested
• For EC flux measurements we can only monitor 2-3 compounds (ie. isoprene, MVK+MAC and perhaps Meoh or MT)
Rack during Mirage MIRAGE/INTEX-B
Note: For NOMAADS we will need to request space adjacent to PTRMS for inlet pump and calibration unit
Alternative or complimentary
• Due to a broader chemistry focus of NOMAADS, a PTR-TOF-MS is proposed to be flown in collaboration between NILU, NOAA, UIBK and NCAR instead or along with PTR-MS
• Instrument comes already prepackaged in a NASA P-3 rack
• Inlet requirements will be the same as for PTR-MS
PTR-TOF-MS footprint
POWER: 120V/1000W Weight: 600 lbs
PTR-MS (NCAR) vs PTR-TOF-MS (NILU/NOAA/UIBK/NCAR)
• PTR-TOF-MS advantages: no pre-selection of compounds needed – we can measure the entire mass spectrum at 10 Hz
• LOD: similar btw. PTR-TOF-MS and PTR-MS for a nominal mass (i.e. compound), but much lower for PTR-TOF-MS, when considering that the instrument scans over the entire mass range
• PTR-TOF-MS disadvantage: somewhat lower sensitivity, but probably acceptable for isoprene flux measurements
• PTR-TOF-MS will also have the option of a SRI (selective reagion ionization) capability
EC flux leg flight patterns
• Horizontal gradients (land cover characterization)
• Vertical gradients (flux divergence measurements)
Will need 20 Hz data stream post-flight
2011 CIRPAS Twin Otter NCAR/UC Berkeley/CIRPAS
Horizontal PBL gradients
160.76 160.78 160.8 160.82 160.84 160.86 160.88 160.9 160.92
0
500
1000
1500
2000
2500
doy
Alt
itu
de (
m)
Radar Altimeter (m)
Ground elevation (m)
Altitude (m a.s.l)
Altitude (m a.g.l.)
PBL soundings
Altitude above ground – PBL height
160.75 160.8 160.85 160.90
500
1000
1500
2000
Extrapolated PBL
Forest: fetch about 10 x PBL height
20 nm
1 nm
View from top
PBL
Flight track
Race track
Sounding (up to 4000-7000 ft depending on PBL) at beginning and end of each profile Sounding can be a “sawtooth” on the outbound leg, should be a spiral between consecutive profiles and a “saw tooth” on the inboundleg: climb rate 500 ft/min
Saw tooth sounding on outbound and inbound legs
Spiral
surface
Synoptic Wind
1 track is about 30 minutes Entire profile is about 1.5 hours at
70 m/s
Profiles flown during CABERNET
Flux divergence
0
0.2
0.4
0.6
0.8
1
1.2
1.4
-0.3 -0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3
z/zi
normalized flux
isoprene
wT
qw
Determine OH: 4 x 106 molecules / cm3
Surface flux
Entrainment flux
MEGAN - Model of Emissions of Gases and Aerosols from Nature
OA
K W
OO
DLA
ND
S
Flux processing (FFT and wavelet decomposition)
-6000 -4000 -2000 0 2000 4000 6000-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5x 10
4
0 20 40 60 80 100-10
0
10
[c -
mean
(c)]
/sq
rt(c
) a) VOC
0 20 40 60 80 100
2
4
8
16
32
64
b) Wavelet Cross Spectrum
Pe
rio
d (
s)
0
0.5
1
0 20 40 60 80 100-10
0
10
Distance [km]
Av
. c
ros
sv
ari
an
ce d) Scale-average Time Series
10-3
10-2
10-1
100
101
-1
-0.5
0
0.5
1
1.5
Hz
f
x C
oS
<w' 'T' 'fft
>
<w' 'VOC' 'fft
>
<w' 'T' 'wave
>
<w' 'VOC' 'wave
>
566.4342 56.64342 5.664342 0.5664342 0.05664342
km
10-4
10-3
10-2
10-1
100
101
-1
-0.5
0
0.5
1
1.5
Hz
f x C
oS
<w' 'T' 'fft
>
<w' 'VOC' 'fft
>
<w' 'T' 'wave
>
<w' 'VOC' 'wave
>
Flux divergence
Entrainment Flux
z/h
PBL top
Flux
Surface Flux
Reactive compound
More reactive compound
Flux profile = function of Dahmkoehler number Da Da = mixing timescale / chemical timescale