REMOTE SOURCES
Time series of deuterium content in Zürich (26.6-11.7.2010)
Humidity uptake in boundary layer. Based on hourly 3D
back-trajectory data (Lagranto) using
COSMO7 analysis data and following the moisture source
diagnostics from Sodemann, et al. 2008.
Sources in %/km
2
of final specific humidity. The mean distance of moisture source
is weighted by the
contribution of the uptake humidity to the final humidity at the
observation site in Zürich.
Transpiration vs entrainment
T @ moisture source
(26.6.2010-11.07.2010)
4) What do high frequency measurements of stable water isotopes
tell
us about regional moisture recyling?
- local water vapour recycling
- warm and stable meteorological conditions
- boundary layer dynamics and transpiration flux
- mixing processes
- source attribution difficult
LOCAL SOURCES
Weighted mean distance
of moisture source location
Cumulative humidity uptake
(26.6-11.7.2010)
- large scale transport of water vapour
- remote conditions during evaporation
- air mass mixing and rain out
Characterisation of commercial laser spectroscopic measurement
systems:
The space-time diagram of stable water isotope investigation
techniques
in atmospheric research.
1) Measurement quality of comm-
ercial laser spectroscopic instruments
(Picarro & Los Gatos) ?
2) Calibration strategy ?
3) What are the characteristics of an
ideal sampling set up ?
4) Can point measurements be used as a proxy for moisture
recycling ?
Goal: Investigate variability in high frequency stable water
isotope signals in boundary layer atmospheric vapour and link it
with atmospheric circulation dynamics.
1) precision: sufficient for observing subdaily changes in
isotope concentration due to local energy fluxes
(Δδ
18
O>~3 permil) and signals associated with different
weather systems and air masses (Δδ
18
O>~10 permil).
2) accuracy and calibration frequency: important
non-linearity
in isotope signals dependent on water concentration, carrier
gas plays a significant role.
3) response time: different for the 2 isotopes, sampling
system
has to be chosen such as to minimise the response time
difference (effect on d-excess!).
Varying correlation regimes for high frequency isotope data,
depending on: - source and transport conditions- weather pattern-
dominant humidity controlling process
Precision @ 1 min aggregation:
σallan 0.06 permil for δ
18
O for Picarro
σallan 0.03 permil for δ
18
O for LGR
Response times for different experimental set ups
Final set up 3: 43 s (H
2
O) , 26 s (
2
H
2
16
O), 30 s (
1
H
2
18
O)
(average over 6 switching tests)
1) Stability of isotope concentration measurement
Allan plots of stability of isotope concentration measurements
at different temporal resolutions.
Picarro=instrument based on cavity ring-down spectroscopy from
Picarro. LGR=instrument based on off-
axis integrated cavity output spectroscopy (OA-ICOS).
Water concentration dependency of isotope measurements with
Picarro L1115-i.
In black synthetic dry air as carrier gas
