Winter School on the Influence of Diabatic Processes on Atmospheric Development
Kvalheim, 3-8 March 2019
Stable Water Isotope Meteorology
Harald Sodemann
Geophysical Institute University of Bergen and Bjerknes Centre for Climate
Research, Norway
Moisture sources for Bergen during 2013 (10-3 mm day-1)
Nov Dec Jan Feb Mar Apr
Number of CAO days
0 5 10 15 20 25
b)
a) 30
Bergen Bergen
Reykjavik Reykjavik
Svalbard Svalbard
Abrupt changes - d18O and d-excess
Steffensen et al. (2008)
What kind of events are we talking about?
On which time scales?
How similar/different are these abrupt events?
What is going on at onset and during phasing out?
Continental isotope map interpolated from GNIP stations
Isotope measurements in precipitation
Bowen and Wilkinson, 2002
Typical isotope ratios in natural reservoirs
by definition: Vienna Standard mean ocean water (VSMOV) = 0‰
Mook, 2001
Moisture sources for Bergen during 2013 (10-3 mm 6h-1) (a) (b)
1 2 3
4
5
6
7
8
melting
layer RH
evaporation
below-cloud exchange
precipitation recycling
mixing
ice-phase processes condensation
Stable isotope processes
0‰
-8‰ -9‰
-10‰
Isotope ratios and the δ notation
Isotope ratior R is defined as ratio of rare over abundant isotope
for V-SMOV (Vienna standard mean ocean water, defined by IAEA) i.e. heavy water isotopes are relatively rare
The small abundance leads to definition of a δ-notation, e.g.
2
R = [HD
16O]
[H
216O] = 155.76 ± 0.1 · 10
618
R = [H
218O]
[H
216O] = 2005.20 ± 0.43 · 10
618
O =
18R
sample18
R
V-SMOV1 · 1000
07/05 00:00 03:00 06:00 09:00 12:00 15:00
Air temperature (ºC)
15 20 25
d-excess (permil)
2 4 6 8 Specific humidity (g kg-1 )
4 6 8
δ18 O (permil) -18 -16 -14
Stable isotope composition of water vapour adds information
Representing the hydrological cycle in models
H
216O HD
16O H
217O H
218O
Precipitation(E, u, μ)
Evaporation conditions
Atmospheric transport
Cloud
microphysics
Stable water isotopes provide an observational means to
separate and quantify the conditions during phase transitions
HDO H
218O
H
216O 99.77% 0.20% 0.03%
Stable water isotopes undergo fractionation during phase changes H
218O and HDO have lower vapour pressures and condense
preferentially, leading to depletion in the atmosphere,
and a combined source and transport signal ("transport history")
HDO H
218O
d-excess d-excess = D 8 ·
18O
Sodemann et al., 2008
E
u
μ
P
Site processes
Source conditions Condensation
Atmospheric transport
Equilibrium isotope fractionation
In an infinite amount of time equilibrium is established between two phases
(e.g. liquid-vapor)
We define the equlibrium fractionation factors 𝛼e
e
(HDO) = R
D(liquid)
R
D(vapor) > 1
e
(H
182O) = R
18O(liquid)
R
18O(vapor) > 1
With values close to 1
Positive values indicate that more heavy isotopes are in the liquid
−80 −60 −40 −20 0 20 40 60 80
1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40
α
Temperature (C)
18
O
liq 18O
vape.g. for T=20ºC:
α(HDOice/liquid) α(HDOliquid/vapour) α(H218Oice/liquid)
α(H218Oliquid/vapour)
Orographic isotope fractionation
Rayleigh condensation model provides
bounds for runoff stable isotope
composition in the Andes
−400 −35 −30 −25 −20 −15 −10
500 1000 1500 2000 2500 3000 3500 4000
Data from Smith&Evans (2007) Alpine main crest
Sieben Hengste
12.5C 10.0C 7.5C
Lütscher et al., 2016
Maximum barrier altitude (m)
δ18O in precipitation or runoff
Conceptual depiction of frontal cloud and precipitation patterns
Isotope fractionation at cold and warm fronts
Moisture sources for Bergen during 2013 (10-3 mm day-1)
Nov Dec Jan Feb Mar Apr
Number of CAO days
0 5 10 15 20 25
b)
a) 30
Bergen Bergen
Reykjavik Reykjavik
Svalbard Svalbard
Snapshot sampling of ground water in Western
Norway during Summer 2016, 2017 and 2018 Hypothesis: elevation sets degree of condensation and
thus isotope composition
Finse
-8.0‰ -8.5‰ -9.0‰ -10.0‰ -11.0‰
Stable isotope gradient with topography
Idar Barstad
SNOWPACE project
Linear depletion model shows "isotope shadows"
July 2017
A stable isotope survey in Southern Norway
δD (permil) Deuterium excess (permil)
Isotope gradient of Southern Norway
Extremes of moisture transport to Norway
Ellen Viste, WaCyEx Project Eastern Norway
Western Norway
Moisture source contribution (kg m-2 day-1)
Airborne water vapour isotope measurements The HyMeX-KIT campaign, Corsica, 2012
PhD Aemisegger (2013)
7oE 30’ 8oE 30’ 9oE 30’ 10oE 41oN
30’
42oN
30’
43oN
30’
Pattern 1 Pattern 2 Pattern 3 Pattern 5 Pattern 7 Pattern 9 TES IASI Falcon
0 250 500 750 1000 1250 1500 1750 2000 2250 2500
Sodemann et al, ACPD, 2016
δ D (permil)
-400 -300 -200 -100
Altitude (m a.s.l.)
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
HYMEX Death Valley Pacific Ocean Scotts Bluff
δ D (permil)
-400 -300 -200 -100 HYMEX
15 Jun 1996 17 Jul 1996 12 Oct 1996
d-excess (permil) -20 0 20 40 60
Altitude (m a.s.l.)
0 500 1000 1500 2000 2500 3000 3500 4000 4500
(a) (b) (c) 5000
Comparison to isotope profiles from literature
Ehhalt (1973) He and Smith (1999)
q (g kg-1)
0 2 4 6 8 10 12 14 16
δ D (%)
-350 -300 -250 -200 -150 -100
8 g kg-1; -100 permil 16 g kg-1; -90 permil 15 g kg-1; -80 permil
q (g kg-1)
0 2 4 6 8 10 12 14 16
d-excess (%)
-10 0 10 20 30 40 50 60 70 Volume mixing ratio (ppmv)
0 6500 13000 19500 26100 32800 Volume mixing ratio (ppmv)
0 6500 13000 19500 26100 32800
(a) (b)
Mixing versus Rayleigh fractionation
Kinetic effecs vs non-linearity of the δ-scale
Sodemann et al, ACP, 2017
07:00 07:20 07:40 08:00 08:20 08:40 09:00 09:20
0 1000 2000 3000 4000
A B C D E F G H
290 295 300 305 310
315 0
5 10 15 20 25
02 46 108
0 20 40 60 80 100
0 5 10 15 20
N E S W N
-350 -300 -250 -200-150 -100
A B C D E F G H
-50 -40 -30 -20 -10
07:00 07:20 07:40 08:00 08:20 08:40 09:00 09:20
0
Time (UTC) 20
40 60 Alt(ma.s.l.)θ(K)q(gkg-1 )RH(%)WS(ms-1 )δD(‰)δ18 O(‰)d(‰) (a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
T(˚C)WD(˚)
09 UTC 20 Sep 2012
08 UTC 21 Sep 2012
Vertical profiles of T, q, RH, for 4 flights in sequence
Long-range advection and descend of air with depleted isotope signature
Sodemann et al, ACP, 2017
unsaturated saturated The evaporation process
H
218O and HDO have lower vapour pressures and condense
preferentially, leading to depletion in the atmosphere
Predicting deuterium excess from an empirical relation
Measurements during the Iceland-Greenland-Seas Project
March 2018
Akureyri
R/V Alliance vapour measurements: 20 days, from 27 Feb – 22 Mar Snow & rain 60 samples
CTD: 272 samples Fog: 2 samples
High-resolution snow sampling: 38 samples, 28 Feb – 22 Mar 1 fjord water sample
1 tap water sample
Transect sampling: 80 samples
Twin Otter vapour measurements: x hours, from 27 Feb – 16 Mar 8 flights
calibrations on ground and during flight calibration samples
Husavik vapour measurements, 15 min averages:
δD, δ18O: 60 days, from 28 Feb to 27 Apr
δD has reduced quality from 23 Mar to 18 Apr
Intercomparison aircraft vs. R/V Alliance, flight M297, 2018-03-06
low level at ship
Water vapourPressure height
Oxygen isotopes of water vapour
Ship water vapour:
5400 ppmv
Ship isotopes:
-16 permil MASIN aircraft:
Quicklooks from
uncalibrated raw PostDoc Alexandra Touzeau
IGP measurements onboard R/V Alliance
PhD Yongbiao Weng
IGP Akureyri Snow, Husavik vapour, Moisture source diagnostic