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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

(2)

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?

(3)

Continental isotope map interpolated from GNIP stations

Isotope measurements in precipitation

Bowen and Wilkinson, 2002

(4)

Typical isotope ratios in natural reservoirs


by definition: Vienna Standard mean ocean water (VSMOV) = 0‰

Mook, 2001

(5)

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‰

(6)

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

16

O]

[H

216

O] = 155.76 ± 0.1 · 10

6

18

R = [H

218

O]

[H

216

O] = 2005.20 ± 0.43 · 10

6

18

O =

18

R

sample

18

R

V-SMOV

1 · 1000

(7)

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

(8)

Representing the hydrological cycle in models

H

216

O HD

16

O H

217

O H

218

O

(9)

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

218

O

H

216

O 99.77% 0.20% 0.03%

(10)

Stable water isotopes undergo fractionation during phase changes H

218

O 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

218

O

d-excess d-excess = D 8 ·

18

O

Sodemann et al., 2008

E

u

μ

P

Site processes

Source conditions Condensation

Atmospheric transport

(11)

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

182

O) = 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 18

O

vap

e.g. for T=20ºC:

α(HDOice/liquid) α(HDOliquid/vapour) α(H218Oice/liquid)

α(H218Oliquid/vapour)

(12)

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

(13)

Conceptual depiction of frontal cloud and precipitation patterns

Isotope fractionation at cold and warm fronts

(14)

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

(15)

Snapshot sampling of ground water in Western

Norway during Summer 2016, 2017 and 2018 Hypothesis: elevation sets degree of condensation and

thus isotope composition

(16)

Finse

(17)

-8.0‰ -8.5‰ -9.0‰ -10.0‰ -11.0‰

Stable isotope gradient with topography

(18)

Idar Barstad

SNOWPACE project

Linear depletion model shows "isotope shadows"

July 2017

(19)

A stable isotope survey in Southern Norway

δD (permil) Deuterium excess (permil)

Isotope gradient of 
 Southern Norway

(20)

Extremes of moisture transport to Norway

Ellen Viste, WaCyEx Project Eastern Norway

Western Norway

Moisture source contribution (kg m-2 day-1)

(21)

Airborne water vapour isotope measurements The HyMeX-KIT campaign, Corsica, 2012

PhD Aemisegger (2013)

(22)

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

(23)

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)

(24)

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

(25)

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)

(26)

09 UTC 20 Sep 2012

08 UTC 21 Sep 2012

Vertical profiles of T, q, RH, for 4 flights in sequence

(27)

Long-range advection and descend of air with 
 depleted isotope signature

Sodemann et al, ACP, 2017

(28)

unsaturated saturated The evaporation process

H

218

O and HDO have lower vapour pressures and condense

preferentially, leading to depletion in the atmosphere

(29)

Predicting deuterium excess from an empirical relation

(30)

Measurements during the Iceland-Greenland-Seas Project

March 2018

Akureyri

(31)

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

(32)

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

(33)

IGP measurements onboard R/V Alliance

PhD Yongbiao Weng

(34)

IGP Akureyri Snow, Husavik vapour, Moisture source diagnostic

(35)

- The transport history of water vapour is reflected in its stable isotope composition

- Stable isotopes are a powerful tool in hydrology and atmospheric sciences

- Its succesful use requires the combination of models and high-quality observations

Summary

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