IEEE International Geosciences and Remote Sensing Symposium24-29 July 2011 Vancouver, CA

THE ARM PROGRAM NETWORK OFMICROWAVE RADIOMETERS:

INSTRUMENTATION, DATA, ANDRETRIEVALS

M.P. Cadeddu1 and D.D. Turner2

1Argonne National Laboratory, Argonne, IL 60439, USA2NOAA/National Severe Storms Laboratory, Norman, OK 73072, USA

US DOE ARM Program ClimateResearch Facilities

Inside a FacilityGVR MWRP MWR

The number of microwave radiometers wasrecently expanded to cover the frequency range 22

to 183.31 GHz

MWR: 23.8, 31.4 GHz

MWRP: 22 - 59 GHz

MWRHF: 90,150 GHz

GVR: 183.3±1,3,7,14 GHz

GVRP: 170 - 183.3 GHz

MWR

MWRPMWRHF GVR GVRP

Higher frequencies have higher sensitivity toPWV and LWP

0 1 2 3 4 5 6

Brig

htne

ss te

mpe

ratu

re (K

)

PWV (cm)

MWR

200

150

100

50

0

0 1 2 3

183.3±1183.3±3 183.3±7 183.3±14

300

250

200

150

100

50

0

MWRHF

GVRGVRP

tb(c

loud

y) -

tb(c

lear

)

LWP

40

30

20

10

00 20 40 60 80 100

150 9031.423.8

Current RMS Error for the MWR retrievals is ~ 0.5mm for PWV and ~0.25 mm for LWP

Decrease PWV RMSE in the Arctic to less than10% by using the 183 GHz line

Decrease LWP RMSE to ~ 0.10-0.15 mm inall climates by using 90, 150, 170 GHz

…However the higher frequencies presentnew challenges

In the past 4 years 5 TGARS papers were published that usedARM data between 50 and 183 GHz to improve microwavespectroscopy at higher frequencies (1 paper on the 183.3 linewidth [1], 2 papers on the microwave water vapor continuum[2,3], 1 paper on the oxygen line parameters [4], 1 paper onwater dielectric models at [5].)

[1] V. H. Payne, J. S. Delamere, K. E. Cady-Pereira, et al., Air-broadened half-widths of the 22- and 183-GHz water-vapor lines, vol 46, pp 3601-3617, 2008.[2] D. D. Turner, M. P. Cadeddu, U. Lohnert, S. Crewell, A. M. Vogelmann, Modifications to the watervapor continuum in the microwave suggested by ground-based 150-GHz observations, vol. 47, no. 10, pp.3326-3337, 2009.[3] V. H. Payne, E. J. Mlawer K. E. Cady-Pereira J.-L. Moncet, Water Vapor continuum in themicrowave vol 49, vol. 6, pp 2194-2208, 2011.[4] M. P. Cadeddu, V. H. Payne, S. A. Clough, K. Cady-Pereira, and J. C. Liljegren, The effect of theoxygen line-parameter modeling on temperature and humidity retrievals from ground-based microwaveradiometers, vol. 45, no. 7, pp. 2216-2223, 2007.[5] M. P. Cadeddu D. D. Turner , Evaluation of Water Permittivity Models From Ground-BasedObservations of Cold Clouds at Frequencies Between 23 and 170 GHz,DOI:10.1109/TGRS.2011.2121074, 2011.

Radiometers CalibrationAll radiometers that calibrate with tip curves use anautomated calibration algorithm developed within theARM program.

Tip calibration data from 3/11-SGP 30 GHz

Tnd

1. Voltages, calibrationand diagnostic dataare stored in data filesand archived.

2. Cryogenic calibrationrecords are kept in acalibration database

3. All datasets can bereprocessed if needed

The tip calibration algorithm isfully automated with a dynamictracking of the noise diodetemperature and is described inseveral documents.

Days in March 2011

Data Quality Control

Data Quality Office (obvious problems with the data)

Data from the ARM microwave radiometers aresubject to layers of quality control

Data quality flags

Monthly reviews by mentor and monthly qualityreports

Segments of bad data are flagged through DataQuality Reports (DQR)

PWV and LWP Retrievals

PWV and LWP for the MWR at all sites are retrieved with astatistical algorithm seasonally trained with radiosonde data(physical retrievals are available at selected site)

Wide dynamic range: PWV: 0-10 cm Retrieval uncertainty ~0.5 mm PWV LWP: 0-3 mm (3000 g/m2) Retrieval uncertainty 0.25 mm

At the North Slope of Alaska neural network PWVretrievals from the GVR (183 GHz) are available andLWP retrievals are in development

GVR retrievals at the North Slope of AlaskaHigher frequencies (170-183 GHz) are useful in verydry conditions during the Arctic winter (PWV < 5 mm)

New PWV retrievals from theGVR are available

30

20

10

0PW

V e

rror

per

cent

age

%

0 5 10 15 20 25

PWV from radiosondes

LWP retrievals from the GVRand GVRP are in development

0 20 40 60 80 100 0 20 40 60 80 100

15

10

5

0

30

20

10

0

Ret

rieve

d LW

P d

istri

butio

n %

NSA Jan+July 2007

LWP

Temperature and humidity profiles

Statistical retrievals of T and H profiles are available at twoARM sites

Temporal and vertical resolution trade-off Elevated inversions and moisture gradients difficult to resolve

Figure from: J. C. Liljegren, Initial evaluation of profiles of temperature, water vapor, and cloud liquid water from a newmicrowave radiometer, 11th Atmospheric Radiation Measurement (ARM) Program Science Team Meeting, Atlanta, Georgia.,19-23 March 2001.

NSA, PWV~ 0.8 cm

Azores, PWV~1.8 cm

T ( C ) WVd g/m3 RH % -60 -40 -20 - 5 0 1 2 3 0 50 100 200

10

8

6

4

2

0

Hei

ght (

km)

0 50 100 1500 5 10 -50 -30 10 10

Hei

ght (

km)

10

8

6

4

2

0

T ( C ) WVd g/m3 RH %

New generation of 3-channel radiometerswill be deployed in 2011-2012 at all sites

23.8, 30, 89 GHz

Improved stability

Narrower FOV

2 and 3 channelretrievals in development

Gradual replacementof 2-channel MWRs

Data availability

Availability

Algorithm

Retrievals

FrequenciesGHz

Sites

2012-2008-2008-2006-2004-1993-

StatisticalPhysicalPhysicalNeural

NetworkNeural

NetworkStatisticalStatisticalPhysical

PWV*LWP*

PWV*LWP*

PWV*LWP*

PWVA

LWP*

PWVA

LWPA

T&H ProfilesA

PWVA

LWPA

23.8, 30, 8990, 150170-183.3183.3 ±1,3,7,1422-5923.8, 31.4

ALLSGPAMF1NSANSANSA

AMF1ALL

MWR3CMWRHFGVRPGVRMWRPMWR

SummaryThe DOE ARM Climate Research Facility has expanded thenetwork of microwave radiometers to cover frequenciesbetween 22 and 183.3 GHz. All radiometers are consistentlycalibrated and data subject to stringent quality control

The new radiometers were designed to reduce the RMS error ofPWV and LWP retrievals in regions such as the Arctic and inoptically thin clouds

New retrievals involving the use of higher frequencies (90-183GHz) are in development (some are already available) and willsupplement the standard ARM retrievals (23.8 and 31.4 GHz)

Data and retrievals are freely available for download from theARM archives (www.archive.arm.gov)