EXPERIMENT Radiative Heating in UnderExplored Bands Campaign (RHUBC)

Period: February 15 – March 15, 2007

Location: ARM NSA, Barrow, Alaska

GOALS

• Comparison of Microwave and Millimeter

wavelength radiometers in deriving PWV and LWP

• Retrieval of Temperature and Humidity Profiles

Remote Sensing of Water Vapor, Cloud Liquid, and Temperature during RHUBC by Microwave and Millimeter Wave Radiometers

E. R. Westwater1,4, D. Cimini2, V. Mattioli3, M. Klein4, V. Leuski4, A. J. Gasiewski1,4 and D. Turner5

1Department of Electrical and Computer Engineering, University of Colorado at Boulder, USA2CETEMPS, University of L’Aquila, L’Aquila, Italy

3Dipartimento di Ingegneria Elettronica e dell'Informazione, Università di Perugia, Perugia, Italy 4Center for Environmental Technology, University of Colorado, USA

5University of Wisconsin, Madison, Wisconsin, USA MOTIVATION

Retrievals of PWV

Fig.1 List of instruments and experimental set-up deployed during RHUBC.

Fig.2 Real time display during RHUBC of GSR Tb data. Note the menu of available choices of available data.

Fig.4 Scatter plot comparisons between the GSR (blue) and the MWR LOS retreivals of PWV compared with RS92 Radiosondes

MWRMWRPGSR

RETRIEVALS OF LWP

Corresponding author: Ed.Westwater@colorado.edu

Fig.3 Comparison of PWV retrievals from the MWR LOS, the GSR, and RS92 Sondes on Julian day 65, 2007

ARM Science Team Meeting, March 10-14, 2008, Norfolk, VA

RETRIEVALS OF LWP AND T AND Q PROFILES

CONCLUSIONS

•As a continuation of our 1999 and 2004 NSA experiments, we

participated In RHUBC, where the principal focus was on low amounts

of Precipitable Water Vapor (PWV < 2 mm), and a secondary goal of

small amounts of cloud liquid. Several improvements were made in the

GSR, both in number of frequencies, and performance of selected

channels. The GSR was successfully operated from February 20 to

July 1, 2007.

• PWV retrievals of the GSR compared well with RS92 Radiosondes and yield a relative accuracy of about 5%.• Comparisons of LWP from the GSR, as well as MIXCRA and MWRRET are quite encouraging for LWP > 20 g/m2. The use of the 340 GHz channels is promising for the smaller LWP amount. • Also encouraging are the preliminary 1DVAR retrievals of temperature and specific humidity. Further development will focus on cloud liquid and the complete set of 27 GSR channels.

Instrument Frequencies (GHz) Parameters

ARM Microwave Radiometer (MWR)

23.8, 31.4 PWV, LWP

CET Ground-based Scanning Radiometer (GSR)

50.300, 51.760, 52.625, 53.290, 53.845, 54.400, 54.950, 55.520, 56.025, 56.215, 56.325

T(z), LWP

ARM Microwave Radiometer Profiler (MWRP)

22.235, 23.035 ,23.835, 26.235, 30.000, 51.250, 52.280, 53.850, 54.940, 56.660, 57.290, 58.800

PWV, LWP, T(z)

CET GSR 89 (H & V) LWP

CET GSR 183.31 ± ( 0.55, ± 1.0, ± 3.05, ± 4.7, ± 7.0, ± 12.0, ± 16.0)

PWV

CET GSR 340 (H & V) LWP

CET GSR 380.197 ± ( 4.0, ± 9.0, ± 17.0) PWV

ARM GVR 183.31 ± ( 1,3,7, 14) PWV, LWP

CET GSR 10 m Cloud

ARM AERI 520 -3300 cm-1 Cloud

GSR RETRIEVAL METHOD•A Priori Linear Statistical Retrieval using Tb’s as predictors•Historical data set of Vaisala RS90/RS92 taken at NSA (Substantial QC was necessary)•RTE model based on Liljegren et al. (2005)•Tb’s adjusted to Liljegren et al. 2005 model based on WVIOP_2004 data comparisons•Covariance matrix of experimental errors determined from WVIOP_2004 data

MWR LOS RETRIEVAL METHOD•A priori Linear Statistical Retrieval using τ (optical depth) as predictors.• Monthly values of Mean Radiating Temperature•RTE model based on Liljegren et al. (2005)

CLEAR CONDITIONS FROM VCEIL AND IRT

Fig. 5. Left. Scatter Plots of LWP retrievals from the MWR-LOS (red), MWRRET(blue) and the MIXCRA (BLACK) vs. the GSR. Right: MIXCRA VS. GSR. Note the excellent agreement between MIXCRA and the GSR

Fig. 6. Left:GSR vs. MIXCRA. Right: MIXCRA vs. MWRRET. Note the outliers associated with the MIXCRA in both figures . This could be due to either an algorithm or an AERI hatch problem.

LWP LESS THAN 60 g/m2

In Fig. 6, we showed LWP retrieval for

contents < 60 g/m2. However, on Julian

day 73, there was a significant amount of

liquid shown by the MWR, the GSR, and

the AERI. Unfortunately, the MWRRET

data did not pass quality control and are

not available for this day. We show in

Figs. 7 retrieval comparisons for the

higher liquid amounts.

Fig. 7. Left Retrievals of GSR-MIXCRA. Right: LOS-GSR Fig. 8. 1DVAR retrievals profiles of Temperature and Specific Humidity.

We have recently developed One Dimensional Variational (1D-VAR) retrievals of GSR data.This method is fully physical and is based on the Liljegren et al. (2005)RTE model. It initial guess is theNCEP forecast model, and the algorithm iterates until the residuals are less that the estimated GSRnoise levels. These retrievals use zenith GSR data up to 183.31 GHz.