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

Stefan Buehler, Mathias Milz, www.sat.ltu.se 3

Our Research Program

Radiative Transfer

New Satellite Sensors

In Situ Measurements

Atmospheric Science

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.

Best studied by satellite sensors.

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).

Why this Focus?

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.

Sun

Earth

Requires good data and modeling to achieve progress.

Stefan Buehler, Mathias Milz, www.sat.ltu.se 6

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

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

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.

Water vapor

Oxygen Upper tropospheric humidity

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

Figures: Salomon Eliasson

Measurement

Stefan Buehler, Mathias Milz, www.sat.ltu.se 14

New Satellite SensorsBetter measurements of ice clouds

(Buehler et al., CIWSIR Mission Proposal, 2005, figure by Viju O. John)

Figure: Sula Systems

new ESA Mission Proposal “CloudIce”

Imaging system for in-situ size and shape measurements

CCD

Laser

CCD

illumination

Detector

Courtesy: Thomas Kuhn

Slow ascend of balloon-borne stereo imager through cloud

Understanding Ice Clouds in the Climate System:Ice Particle In-Situ Imaging

Climate Models SatelliteObservationsAnnual mean ice water path from different climate

models: Large discrepancies!

A priori assumptions on size, shape, volume of ice particles

Climate changeRole of ice particles in radiative budget andhydrological cycle

Instrument setup In-situMeasurementsCCD

First implementation of in-situ ice crystal stereo imaging:

Microscopeobjectives

(Flash lamp)Optical fiberFocusing lens

Captures of single-microscope imager

Ice Particle Measurements Size, Shape, Volume,

Concentration

Use measurements for Study cloud processes

(formation, growth,

precipitation, ...) Derive parameterizations of

shape/size distributions for

satellite retrievals and

climate models

(e.g., EarthCARE, SMILES, SPIDER, ...)

/aircraft/balloon/ground-based

- two microscope imaging probes triggered by detection system- allows reconstruction of 3D shape and improves size and volume estimate

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?