µ-wave radiometry

Principles

Science

Conclusions

Microwave Radiometry of Water Vapor

N. Kampfer, Th. Flury, A. Haefele, K. Hocke,J. Morland, S. Muller, M. Schneebeli, E. De Wachter

Institute of Applied PhysicsUniversity of Bern

Switzerland

WG1 workshop of COST-WAVACSLindenberg, 21. May 2008

µ-wave radiometry

Principles

Science

Conclusions

Outline

Principles of microwave radiometry

Examples of what can be achieved

Conclusions

µ-wave radiometry

Principles

Science

Conclusions

Microwave radiometry of stratospheric H2OAtmospheric transmission at microwave frequencies

0

0.1

0.2

0.3

0.4

0.5

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0.8

0.9

1

0 50 100 150 200 250 300

Tra

nsm

ittan

ce

Frequency [GHz]

Zenith Microwave Transmittance

H2O O2

O2

H2O

Dry (0 kg/m2)Polar (3.1 kg/m2)

Midlatitude (21.3 kg/m2)Tropical (53.6 kg/m2)

µ-wave radiometry

Principles

Science

Conclusions

Microwave radiometry of stratospheric H2OMicrowave radiometer

Target

Black BodyCalibration

Atte

nuat

or

Noise Diode

Mixer Filter AmplifierAmplifierCouplerAntenna Detector

+/− 0.5 GHzRF = 22.2

H2OAtmosphere

DCIF =0 to 0.5 GHz

Local Oscillator

LO =22 GHz

Frequency

Pow

er

LO

IF = |RF +/− LO|

LSB

US

B

µ-wave radiometry

Principles

Science

Conclusions

Microwave radiometry of stratospheric H2OMeasurement of pressure broadened emission lines

MIAWARA: Middle atmosphericwater vapor radiometer

Measured spectrum of H2Oat 22 GHz

Question: What is the distribution of water vapor in theatmosphere that leads to such a spectrum?

I (ν) = I0e−τ(z0) +

z0∫0

T (z)e−τ(z)ka(p,T ,n(z)) dz

µ-wave radiometry

Principles

Science

Conclusions

Microwave radiometry of stratospheric H2OMeasurement of pressure broadened emission lines

MIAWARA: Middle atmosphericwater vapor radiometer

Measured spectrum of H2Oat 22 GHz

Question: What is the distribution of water vapor in theatmosphere that leads to such a spectrum?

I (ν) = I0e−τ(z0) +

z0∫0

T (z)e−τ(z)ka(p,T ,n(z)) dz

µ-wave radiometry

Principles

Science

Conclusions

Optimal estimation technique

The radiative transfer problem is an ill posed problem→ solution is not unique

... but by combining a priori knowledge, xa, withmeasurement, y, in an optimal way allows to retrieve analtitude profile, x, from the measurements by consideringuncertainties in the measurement, Sy and in the a prioriknowledge, Sa

x = xa + SaKT(KSaK

T + Sy)−1(y −Kxa)

K is the so called kernel function or weighting function

µ-wave radiometry

Principles

Science

Conclusions

Optimal estimation technique

The radiative transfer problem is an ill posed problem→ solution is not unique

... but by combining a priori knowledge, xa, withmeasurement, y, in an optimal way allows to retrieve analtitude profile, x, from the measurements by consideringuncertainties in the measurement, Sy and in the a prioriknowledge, Sa

x = xa + SaKT(KSaK

T + Sy)−1(y −Kxa)

K is the so called kernel function or weighting function

µ-wave radiometry

Principles

Science

Conclusions

Water vapor: a key research topic at IAP

Different techniques used to measure H2O from the groundto the mesopause

µ-wave radiometry

Principles

Science

Conclusions

Distribution of H2O from 20 to 70 km over Bernmeasured by microwave radiometry in the frame of NDACC

Ph.D. thesis Haefele

µ-wave radiometry

Principles

Science

Conclusions

Distribution of tropospheric H2OCombining information of channels→ tropospheric water vapour and→ temperature profiles

Ph.D. thesis Schneebeli

µ-wave radiometry

Principles

Science

Conclusions

Water vapor column density climatology

Morland et al. tbs 2008

µ-wave radiometry

Principles

Science

Conclusions

Examples of present research topicsSudden stratospheric warming

Reaction of O3 and H2O to a sudden stratospheric warmingFlury, Haefele, Hocke and Kampfer in preparation for JGR

µ-wave radiometry

Principles

Science

Conclusions

Examples of present research topicsTides in the atmosphere

Tidal structures of temperature (from SABER satellite) andH2O (from MIAWARA Zimmerwald) in the mesospherePh.D. thesis A.Haefele

µ-wave radiometry

Principles

Science

Conclusions

Conclusions

Microwave radiometry operated from the ground is wellsuited to retrieve:

I water vapour profiles

I integrated water vapour

I integrated liquid water

Continuous measurements possible during most of time

I middle atmospheric profiles from 20 - 70 kmI time resolution approx. 1 hourI averaging kernels approx. 10 -15 kmI validation with satellites within 10%

I tropospheric profiles up to approx. 5 kmI time resolution few minutesI validation with close-by radio sondesI potential for nowcasting of thunderstorms

THANK YOU

µ-wave radiometry

Principles

Science

Conclusions

Conclusions

Microwave radiometry operated from the ground is wellsuited to retrieve:

I water vapour profiles

I integrated water vapour

I integrated liquid water

Continuous measurements possible during most of time

I middle atmospheric profiles from 20 - 70 kmI time resolution approx. 1 hourI averaging kernels approx. 10 -15 kmI validation with satellites within 10%

I tropospheric profiles up to approx. 5 kmI time resolution few minutesI validation with close-by radio sondesI potential for nowcasting of thunderstorms

THANK YOU

µ-wave radiometry

Principles

Science

Conclusions

Conclusions

Microwave radiometry operated from the ground is wellsuited to retrieve:

I water vapour profiles

I integrated water vapour

I integrated liquid water

Continuous measurements possible during most of time

I middle atmospheric profiles from 20 - 70 kmI time resolution approx. 1 hourI averaging kernels approx. 10 -15 kmI validation with satellites within 10%

I tropospheric profiles up to approx. 5 kmI time resolution few minutesI validation with close-by radio sondesI potential for nowcasting of thunderstorms

THANK YOU

µ-wave radiometry

Principles

Science

Conclusions

Conclusions

Microwave radiometry operated from the ground is wellsuited to retrieve:

I water vapour profiles

I integrated water vapour

I integrated liquid water

Continuous measurements possible during most of time

I middle atmospheric profiles from 20 - 70 kmI time resolution approx. 1 hourI averaging kernels approx. 10 -15 kmI validation with satellites within 10%

I tropospheric profiles up to approx. 5 kmI time resolution few minutesI validation with close-by radio sondesI potential for nowcasting of thunderstorms

THANK YOU

µ-wave radiometry

Principles

Science

Conclusions

Microwave radiometry of H2O from aircraftSCOUT-O3 campaign Nov. 2005

Dynamical case study for mesospheric H2O enhancement

thomas.flury@iap.unibe.ch

Water vapor profiles on flight

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Ph.D. thesis Th.Flury