deployments of microwave and millimeter-wave radiometers...

Florence, ItalyMarch 11-14, 2008M icroRad’08

Deployments of Microwave and Millimeter-wave

Radiometers in the Arctic

E. R. Westwater1, D. Cimini,1,2 , V. Mattioli3

A. J. Gasiewski1, M. Klein4, V. Leuski4 , D. Turner5

1 Center for Environmental Technology, Department of Electrical and Computer Engineering,

University of Colorado at Boulder, USA

2 CETEMPS, Physics Department, University of L'Aquila, Italy

3 Dipartimento di Ingegneria Elettronica e dell'Informazione, Università di Perugia, Italy

4 Center for Environmental Technology, Cooperative Institute for Research in Environmental

Sciences, University of Colorado at Boulder, USA

5 University of Wisconsin, Madison, Wisconson, USA

1) Arctic moisture and clouds play a key role in our climate, but are difficult to measure because of small concentrations. Development of RTE models requires accurate measurements of these variables.

2) Conventional instruments (MWR, GPS, radiosondes) show small sensitivity to low Precipitable Water Vapor (PWV) and Liquid Water Path (LWP).

3) Radiometers operating at mm- and submm-wavelengths offer greatly-enhanced sensitivity to PWV and LWP (Racette et al., 2005)

Motivation

4) Improved calibration methods of Radiometers and improved Radiosonde technology from 1999 and 2004 made another NSA/IOP desirable in 2007: Radiative Heating in UnderexploredCampaign (RHUBC)

Atmospheric Opacity for Arctic Conditions

PREVIOUS DEPLOYMENTS OF CSR AND GSR

1. CSR in NSA WVIOP 1999:NOAA/ETL: Circularly Scanning RadiometerNASA/GSFC: Millimeter-wave Imaging Radiometer

2. GSR in NSA WVIOP 2004:NOAA/PSD: Ground-based Scanning RadiometerARM: MWR and MWRP

3. GSR in RHUBC 2007:NOAA-CU CET: Ground-based Scanning RadiometerARM: MWR, MWRP, and GVR

MIR and CSR in NSA WVIOP 1999

First experimental confirmationof the greatly-enhanced sensitivity of mm wave radiometers relative to the MWR.CSR-MIR channel 183.31 ±7

Peak-to-peak Tb variationof 3 K

Peak-to-peak TbVariation of 70 K

CET PI: E.R. WestwaterCo-PIs: A.J. Gasiewski, M. Klein, V. Leuski

D. CiminiPeriods: March-April 2004 (WVIOP2004)

and February-March 2007 (RHUBC)Location: ARM NSA, Barrow, Alaska

The Arctic Winter Radiometric Experiments WVIOP2004 and RHUBC (2007)

Radiometers1) Dual channel Microwave Radiometer (MWR):

23.8; 31.4 GHz

3) 12-channel Microwave Radiometer Profiler (MWRP):22.235; 23.035; 23.835; 26.235; 30.0 GHz51.25; 52.28; 53.85; 54.94; 56.66; 57.29; 58.8 GHz

MWRMWRP

4) 27-channel Ground-based Scanning Radiometer (GSR)50.2; 50.3; 51.76; 52.625; 53.29; 53.845; 54.4; 54.95; 56.215;56.325 GHz89 V; 89 H GHz 183.31±0.55; ±1; ±3.05; ±4.7; ±7; ±12; ±16 GHz 340 V; 340 H GHz 380.197 ± 0.4, ± 1.5; ±4; ±9; ±17 GHz

2) 4-channel GVR 183.31 ±1; ±3; ±7; ±16 GHz

GSR in NSA WVIOP 2004 (Cimini et al., TGRS, 2007)

340 GHz

183±7 GHz

183±16 GHz

89 GHz22.2 GHz

31.4 GHz

Measured Tb response to PWV during clear-sky

GSR in NSA WVIOP 2004 (Cimini et al., TGRS, 2007)

Measured Tb response to LWP during cloudy-skyδ

PROBLEMS WITH RADIOSONDES(Mattioli et al., JAOT, 2007)

GSR in NSA WVIOP 2004

GSR Weighting Functions showing response to Upper-Troposphere Lower Stratosphere Water Vapor

GSR in NSA WVIOP 2004 (Mattioli et al. poster)

Statistical comparisons of GSR vs. RS90 and VIZ Humidity calculations

RADIATIVE HEATING IN UNDEREXPLORED BANDS CAMPAIGN

RHUBC’2007

RADIATIVE HEATING IN UNDEREXPLORED BANDS CAMPAIGN

RHUBC’2007

• RHUBC focused on PWV < 2 mm (usually associated with TS < -30 C)

• Promising conditions for PWV/cirrus cloud provided by Penn State University forecast

• Decision to launch radiosondes used quasi real time GSR data.

PWV FROM GSR AND MWR-LOS

Julian day

PWV FROM GSR AND MWR-LOS

LWP FROM GSR, GVR, AND MWR-AERI

RETRIEVALS OF LIQUID WATER PATH

GSR: OPTIMAL ESTIMATION USING WINDOW CHANNEL TB’S’

GVR: NEURAL NET ON 4 TB’S

MWR: (A) LOS- OPERATIONAL ARM RETRIEVAL(B) MWRRET – Turner et al., TGRS, 2007(C) MIXCRA – MWR + IR, Turner, JGR, 2007

SUMMARY AND CONCLUSIONS

• Achieved unprecedented accuracy in retrievals of PWV under Arctic conditions

• Above threshold of 10-15 g/m2 of LWP,GSR, GVR, and MIXCRA retrievals are promising

• Retrievals of LWP in the 10-15 g/m2 region require more research (340 GHz channels should help GSR)

• Temperature retrievals (next talk by Cimini)

THANK YOU FOR YOUR ATTENTION

D. Cimini, E. R. Westwater, A. J. Gasiewski, M. Klein, V. Leusky, and J. C. Liljegren, „The Ground-based Scanning Radiometer (GSR): a powerful tool for the study of the Arctic Atmosphere”, IEEE Transactions on Geosciences and Remote Sensing, Vol. 45, No. 9, September 2007, pp. 2759-2777..

D. Cimini, E. R. Westwater, A. J. Gasiewski, M. Klein, V. Leuski, J. C .Liljegren, Ground-based millimeter- and submillimiter-wave observations of low vapor and liquid water contents, IEEE Transactions on Geosciences and Remote Sensing, Vol. 45, No. 7, Part II. July 2007, pp.2169-2180.

V. Mattioli, E. R. Westwater, D. Cimini, J. C. Liljegren, B. M. Lesht, S. I. Gutman, and F. J. Schmidlin “Analysis of Radiosonde and ground-based remotely sensed PWV data from the 2004 North Slope of Alaska Arctic Winter Radiometric Experiment” Journal of Atmospheric and Oceanic Technology, Vol. 24, March 2007, 415-431

References

Backup slides

Some Details of Forward Model Comparisons

Radiometer CalibrationInternal Loads (10 ms)External Blackbody Targets (2 min) Tip Calibration (Window Channels)

Calculations from RadiosondesCompute band-averaged Tb

Relative to Monochromatic, band calculations provide corrections up to 2.5 K !

Typical results of Forward Model AnalysisNear 183 .31 GHz for WVIOP2004

183.31 +/- 4.7 GHz 183.31 +/- 7 GHz

GSR in RHUBC OPERATIONS

• RHUBC focused on PWV < 2 mm (usually associated with TS < -30 C)

• Promising conditions for PWV/cirrus cloud provided by Penn State University forecast

• Decision to launch radiosondes used quasi real time GSR data.

GSR retrieval during a Low PWV Period

Retrieval Method to derive PWV and LWP from Four Window and Seven 183.31 Channels of the GSR

• A Priori Linear Statistical Retrieval• Historical data set of Vaisala RS90/RS92 taken at NSA

(Substantial QC was necessary)• RTE model based on Liljegren et al. (2005)• Two sets of PWV retrievals: (A) Using original Tb

calibration; (B) using Tb’s adjusted to Liljegren et al. 2005 model based on WVIOP_2004

• Covariance matrix os experimental errors determined from WVIOP_2004 data

• Ground truth from Vaisala RS92 Radiosondes launched at the Great White

GSRRS92

Julian day

7-channel 183-GHz PWV retrievals for Julian Day 54, 2007

Window channel PWV retrievals for Julian Day 54, 2007

Julian day

RS92 GSR-adj

GSR-orig

Window channel LWP retrievals for Julian Day 54, 2007

Julian day

MWR GSR-orig GSR-adj

PWV retrievals for Julian Day 65, 2007

Julian day

Original and Adjusted GSR 89-183 window PWV retrievals

MWR and GSR 89-183 window PWV retrievals

Conclusions and Further Work

• Quasi Real-time PWV retrievals (without tip cal) were used successfully for radiosonde launch decisions

• GSR linear 7-channel and 89- window PWV Retrievals compared well with Vaisala RS92/LIL05 calculations (0.1 mm rms: 6%)

• Profile Retrievals from GSR using Optimal Estimation

Thank you very much for your attention

• GSR linear 89- window LWP Retrievals are promising, but need independentverification

Work in Progress

D. Cimini, E. R. Westwater, A. J. Gasiewski, M. Klein, V. Leusky, and J. C. Liljegren, „The Ground-based Scanning Radiometer (GSR): a powerful tool for the study of the Arctic Atmosphere”, IEEE Transactions on Geosciences and Remote Sensing, Vol. 45, No. 9, September 2007, pp. 2759-2777..

D. Cimini, E. R. Westwater, A. J. Gasiewski, M. Klein, V. Leuski, J. C .Liljegren, Ground-based millimeter- and submillimiter-wave observations of low vapor and liquid water contents, IEEE Transactions on Geosciences and Remote Sensing, Vol. 45, No. 7, Part II. July 2007, pp.2169-2180.

V. Mattioli, E. R. Westwater, D. Cimini, J. C. Liljegren, B. M. Lesht, S. I. Gutman, and F. J. Schmidlin “Analysis of Radiosonde and ground-based remotely sensed PWV data from the 2004 North Slope of Alaska Arctic Winter Radiometric Experiment” Journal of Atmospheric and Oceanic Technology, Vol. 24, March 2007, 415-431

REFERENCES

Back up Slides

RHUBC: GSR 183.31 +/- 7 GHzmeas. vs. LIL05 calc.

RHUBC Objectives Pi’s: Dave Turner (UW) and Eli Mlawer

• Conduct a clear sky radiative closure exercise in the far-IR, to reduce uncertainties in water vapor continuum and absorption line parameters

• Investigate the radiative properties of cirrus in the far-IR

• Instrument cross-comparison and validation– Far-IR instruments (AERI-ER, FIRST, TAFTS)– 183 GHz microwave radiometers (GSR, GVR,

later MP-183)

Prepared by Dave Turner

RHUBC: GSR 183.31 +/- 4.7 GHzmeas. vs. LIL05 calc.

RHUBC Approach

• Conduct experiment at NSA ACFR in Feb - Mar, when climatology favors clear skies and PWV is the low (~ 2 mm)

• Bring in TAFTS, FIRST, second AERI-ER• Bring in GSR• Have extra radiosondes available for

investigators to launch when conditions are ‘good’

• Daily planning meeting to discuss operations, as we were targeting clear + dry and cirrus + dry conditions

Prepared by Dave Turner

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