Transcript Slide 1

Satellite Atmospheric
Science at Kiruna
Space Campus
Mathias Milz
Luleå University of Technology
Department of Space Science
Kiruna
The Satellite Atmospheric Science Group at Kiruna
Space Campus
 Head of the group: Prof. Stefan Buehler
 Currently:
one Ex-jobb student
 four PhD students (1-2 coming this fall)
 three Assistant Professors
one software engineer
 Young group (since fall 2006)
 Close collaboration with IRF,
Chalmers, Met Office (UK),
Observatoire de Paris,
SMHI, etc.
 Focus:
- atmospheric humidity
- cloud ice
- radiative transfer
http://www.sat.ltu.se
Our Research Program
Radiative Transfer
Atmospheric Science
New Satellite Sensors
In Situ Measurements
Stefan Buehler, Mathias Milz, www.sat.ltu.se
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Motivation
 Earth is getting warmer.
 Climate predictions have large
uncertainty.
 (One) main reason: we do not
know enough on clouds and
humidity in the atmosphere.
IPCC 4th assessment report, 2007
Figure 3.1. Annual anomalies of global land-surface air
temperature (°C), 1850 to 2005, relative to the 1961 to 1990 mean
for CRUTEM3 updated from Brohan et al. (2006). The smooth
curves show decadal variations (see Appendix 3.A). The black
curve from CRUTEM3 is compared with those from NCDC
(Smithand Reynolds, 2005; blue), GISS (Hansen et al., 2001; red)
and Lugina et al. (2005; green).
 Best studied by satellite
sensors.
Why this Focus?
Sun
 Humidity and clouds have
strong influence on Earth
radiation balance.
 They create strong feedbacks,
which can amplify or attenuate
anthropogenic forcings, such as
CO2 increase.
 Currently one of the largest
uncertainties in climate
predictions.
Earth
 Requires good data and modeling to achieve progress.
Radiative
Transfer
http://www.sat.ltu.se/arts
ARTS - Atmospheric
Radiative Transfer
Simulator
• Public domain
• In collaboration with
Chalmers
• Microwave to IR
• With scattering
Instrument simulation
Radiation flux simulation
Stefan Buehler, Mathias Milz, www.sat.ltu.se
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Advanced Microwave Sounding Unit (AMSU)
 On NOAA satellites.
 Similar instruments
on Metop and many
other satellites.
 Microwave
temperature and
humidity sensor.
The Metop satellite, image: ESA.
AMSU-B
Oxygen
Upper tropospheric humidity
Water
vapor
Buehler, S. A. and V. O. John (2005),
A Simple Method to Relate Microwave Radiances to Upper Tropospheric Humidity,
J. Geophys. Res., 110, D02110, doi:10.1029/2004JD005111.
Atmospheric Science
Buehler, S. A., M. Kuvatov, V. O. John, M.
Milz, B. J. Soden and J. Notholt (2008),
An Upper Tropospheric Humidity Data
Set From Operational Satellite
Microwave Data,
J. Geophys. Res., 113, D14110,
doi:10.1029/2007JD009314.
 Upper tropospheric humidity (UTH) climatology
from AMSU data
 Data processed from 2000
 SSM-T2 data since 1994 will be processed next
Humidity in the Climate System:
Comparing infrared and microwave
measurements
 Infrared:
• Operational measurements since 1979
• Different instruments with different properties
• Very sensitive to all clouds
 Microwave:
• Operational measurements since 1994
• Different instruments but all using the same spectral line
• Insensitive to thin clouds
 Thorough characterisation of infrared and microwave datasets
is necessary to use the data.
The Role of Cirrus Clouds:
Shortwave
 Cirrus clouds reflect sunlight
and thus increase the
planetary albedo.
 Cooling effect
(AVHRR, Channel 1, 580-680nm, 25.1.2002, 13:30 UTC, Data
Source: Met Office / Dundee Receiving Station)
The Role of Cirrus Clouds:
Longwave
 Cirrus clouds are radiatively
cold and thus reduce the OLR.
 Heating effect
 Attention: grayscale is
normally reversed for IR
images so that clouds look
white.
 Net cooling or heating effect of
cirrus depends on physical
properties
• Thickness
• Opacity
• Particles
• …
(AVHRR, Channel 4, 10.3-11.3μm, 25.1.2002, 13:30 UTC, Data
source: Met Office / Dundee Receiving Station)
Discrepancies in Climate Model Ice Water Path
Measurement
Figures: Salomon Eliasson
New Satellite Sensors
Better measurements of
ice clouds
Figure: Sula Systems
new
ESA Mission Proposal
“CloudIce”
(Buehler et al., CIWSIR Mission Proposal, 2005, figure by Viju O. John)
Stefan Buehler, Mathias Milz, www.sat.ltu.se
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Imaging system for in-situ size and shape measurements
Detector
illumination
CCD
Laser
Courtesy: Thomas Kuhn
Understanding Ice Clouds in the Climate System:
Ice Particle In-Situ Imaging
Satellite /aircraft/balloon/ground-based
(e.g., EarthCARE,
Observations SMILES,
SPIDER, ...)
Climate Models
Annual mean ice water path from different climate
models: Large discrepancies!
Climate change
Role of ice particles in
radiative budget and
hydrological cycle
Instrument setup
(Flash lamp)
Optical fiber
Focusing lens
CCD
A priori assumptions on size, shape,
volume of ice particles
In-situ
Measurements
Ice Particle Measurements
 Size, Shape, Volume,
Concentration
Microscope
objectives
Use measurements for
First
implementation
-of
twoin-situ
microscopeice
imaging probes
triggered by detection system
crystal
stereoof 3D
- allows reconstruction
shape and improves size and
imaging:
Slow ascend of balloon-borne
volume estimate
stereo imager through cloud
 Study cloud processes
(formation, growth,
precipitation, ...)
 Derive parameterizations of
shape/size distributions for
satellite retrievals and
Captures of singleclimate models
microscope imager
Summary
 Atmospheric humidity in its different phases (gas, liquid, solid) is a
key parameter for understanding and predicting the climate system.
 Approached by our group in different ways:
- satellite humidity measurements
- satellite cloud ice measurements
- in situ cloud ice measurements
- development of new satellite and in situ instruments
- radiative transfer
 Questions?