institute for climate and atmospheric science balloons, waves and cirrus in the tropics steven...
TRANSCRIPT
Institute for Climate and Atmospheric Science
Balloons, waves and cirrus in the tropics
Steven Dobbie
Institute for Climate and Atmospheric ScienceUniversity of Leeds
Sardar Al-Jumur
Benjamin Murray, Theodore Wilson, Zhiqiang Cui
Ottmar Möhler, Martin Schnaiter, Robert Wagner, Stefan Benz, Monika Niemand, Harald Saathoff, Volker Ebert, Steven Wagner and
Bernd Kärcher
Neil Gordon
MOGUL Meeting – Feb 28, 2013
Institute for Climate and Atmospheric Science
Balloons, waves and cirrus in the tropics
Institute for Climate and Atmospheric Science
What is interesting about TTL region?
Ice supersaturations frequently exceed 100% Rhi
(Jensen et al, 2005; Peter et al., 2006).
Is something inhibiting the formation of cirrus?
Institute for Climate and Atmospheric Science
What is interesting about thin TTL cirrus?
High in-cloud supersaturations and low ice number concentrations
(Kramer et al., 2009)
Why aren’t high supersaturations in cloud being quenched?
Institute for Climate and Atmospheric Science
“Supersaturation puzzle”
Institute for Climate and Atmospheric Science
Source of supersaturation
- As air rises the air cools and RHice rises
Sink of supersaturation
- As RHice rises vapour deposits on ice crystals present
Institute for Climate and Atmospheric Science
- Homogeneous nucleation results in numerous crystals of small size so RHice is quenched quickly
- Heterogeneous nucleation results in few crystals of larger size and RHice is slower to quench.
- Numbers of traditional IN are too few
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
What is up there?
Froyd et al 2010:
Institute for Climate and Atmospheric Science
Candidates?
-Mineral dust?
- Low numbers
“Even if all mineral dust nucleated they couldn’t explain the ice numbers” (Froyd et al 2010)
Institute for Climate and Atmospheric Science
What if?
What if some of the numerous solution aerosols were nucleating at lower super-saturations—below water saturation?
Institute for Climate and Atmospheric Science
Candidates?
Sulphates crystallise in low relative humidity conditions.
- numbers are high
- solid so could act as an ice nuclei?
Institute for Climate and Atmospheric Science
Candidates?
- Sulphates are too viscous at TTL conditions to crystallise (Bodsworth et al., 2010)
Institute for Climate and Atmospheric Science
Candidates?
-Very low accommodation coefficient (0.0075) and so slow uptake of water vapour? (Magee et al., 2006)
-Recent work by Skrotzki (2012) shows it is > 0.1
Institute for Climate and Atmospheric Science
Candidates?
What else could be solid and act as an IN at low temperatures?
Institute for Climate and Atmospheric Science
Glassy aerosols
”Temperature at which materials change from hard and brittle to soft and pliable”
“The temperature below which an amorphous material is a glassy solid and above which it is a viscous liquid“
Murray et al., 2008 and Zobrist et al., 2008
Previously not thought to be applicable to troposphere but is relevant for TTL.
Thought to potentially inhibit nucleation
Institute for Climate and Atmospheric Science
Brittle glassy aerosol
T / RHi decreasing
Laboratory glassy aerosols
Institute for Climate and Atmospheric Science
Brittle glassy aerosol Liquid solution aerosol
T / RHi increasing
Institute for Climate and Atmospheric Science
AIDA Chamber, Karlsruhe Aqueous citric acid,
Raffinose/M5AS,
Levoglucosan,
HMMA
i) it has similar functionality to oxygenated organic
compounds known to exist in atmospheric aerosols;
ii) its glass forming properties are similar to a range of other atmospherically relevant aqueous organic solutions and aqueous organic-sulphate mixtures; and
iii) Representative of products found in the atmosphere.
Institute for Climate and Atmospheric Science
What did the AIDA results show for glassy behaviour during nucleation?
Institute for Climate and Atmospheric Science
AIDA results:
Above 212K
(non-glassy regime)
Below 212K
(glassy regime)
Institute for Climate and Atmospheric Science
AIDA results:
Above 212K
(non-glassy regime)
Below 212K
(glassy regime)
Institute for Climate and Atmospheric Science
Modelling results
1-D APSC (Karcher, DLR) runs:
185 190 195
16.6
16.8
17.0
17.2
17.4
17.6
17.8
18.0
80 90 100 0 20 40 60 80 100 0 1 2 3 4
Alti
tude
/ km
Temperature / K Pressure / mBar RHi (%)
H2O mixing ratio
/ ppm
Institute for Climate and Atmospheric Science
0 100 200 300100
110
120
130
140
150
160
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0
1
2
3
4
5
6
7
8
9
10
11
0 100 200 300
b) HET
(%)RHi
IWC
Nice
(%)R
Hi
Time / minutes
a) HOM
Nic
e / cm
-3
Nice
IWC
IWC
/ m
g m
-3
(%)RHi
R / m
R
Time / minutes
R
APSC results: Constant uplift
b) Glassy
Institute for Climate and Atmospheric Science
0 100 200 300 400100
110
120
130
140
150
160
0 100 200 300 400
0.01
0.1
1HOM, 0.76 K hr-1
3.8 K hr-1
3.8 K hr-1
2.5 K hr-1
1.26 K hr-1
0.25 K hr-1
0.76 K hr-1
0.50 K hr-1
HOM, 0.76 K hr-1
% R
Hi
Time / minutes
0.25 K hr-1
0.50 K hr-10.76 K hr-1 1.26 K hr-1
2.5 K hr-1
Nic
e /
cm-3
Time / minutes
Me
asu
red
Nic
e
APSC results: Citric acid/constant uplift
Institute for Climate and Atmospheric Science
APSC results: Raffinose/M5AS
Institute for Climate and Atmospheric Science
IN indirect response
Institute for Climate and Atmospheric Science
Glassy indirect effect
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Forced by single waves: het/glassy
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Forced by observed
superposition of waves:
(Jensen and Pfister, 2004)
Institute for Climate and Atmospheric Science
Deposition coefficient sensitivity
Institute for Climate and Atmospheric Science
High altitude balloon observations (Hertzog et al., LMD)
- 2-3 months floating around in the tropics
advected on constant density surfaces
- measuring temperature and pressure
Institute for Climate and Atmospheric Science
High altitude balloon (LMD; Hertzog et al)- 2-3 months floating around in the tropics
advected on constant density surfaces
- measuring temperature and pressure
Institute for Climate and Atmospheric Science
Hertzog et al
Balloon trajectory
Institute for Climate and Atmospheric Science
Temperature variations
Institute for Climate and Atmospheric Science
Het (glassy) model run
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Hom activated
Institute for Climate and Atmospheric Science
Optical depth
Institute for Climate and Atmospheric Science
Cloud lifetime
Hom Glassy
Institute for Climate and Atmospheric Science
Radiative properties
Institute for Climate and Atmospheric Science
Satellite observations
Can we obtain remote sensing at the location of the balloon?
Institute for Climate and Atmospheric Science
Satellite observations
Institute for Climate and Atmospheric Science
MLS – AURA CALIPSO - Lidar
Conclusions
Experiments:
- A range of common organics and organic/sulphate mixtures become glassy and nucleate ice heterogeneously
Modelling:
- Modelling results using glassy aerosols are consistent with observed high in-cloud super-saturations and low ice number concentrations
- Modelling agree for ice number, RHi, optical depth, heating rates, etc.
Institute for Climate and Atmospheric Science
Conclusions
Modelling:
- Consistency for both constant lifting and gravity waves forcings
- Strong potential indirect response with glassy nucleation
- Suppression of ice number
- Shorter lifetime
- Heterogeneous nucleation mechanism is needed to explain observations.
Institute for Climate and Atmospheric Science
Next steps
Remote sensing:
- Frequency of cloud: average the cloud occurrence from Calipso that are detached, at TTL heights, and close to balloon.
- Launch a balloon with humidity, particle counters, etc.
Institute for Climate and Atmospheric Science
Challenges
-Need an instrument to measure glassy particles.
-Understand aerosol spatial variations in the TTL and transport mechanisms.
-Assessing potential anthropogenic influences/indirect effects.
-Looking at warmer temperature glassy particles. Are they playing a role outside the tropics?
Institute for Climate and Atmospheric Science
- Thank you -
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Institute for Climate and Atmospheric Science
Radiative heating rates Optical depth
Institute for Climate and Atmospheric Science
Forced by single waves: hom
Institute for Climate and Atmospheric Science
Radiative heating rates