EXPERIMENT Radiative Heating in UnderExplored Bands Campaign (RHUBC)

1. 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, USA 2CETEMPS, 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 • 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 • 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. GSR MWRP MWR Fig.1 List of instruments and experimental set-up deployed during RHUBC. Retrievals of PWV • 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) Fig.2 Real time display during RHUBC of GSR Tb data. Note the menu of available choices of available data. Fig.3 Comparison of PWV retrievals from the MWR LOS, the GSR, and RS92 Sondes on Julian day 65, 2007 Fig.4 Scatter plot comparisons between the GSR (blue) and the MWR LOS retreivals of PWV compared with RS92 Radiosondes RETRIEVALS OF LWP LWP LESS THAN 60 g/m2 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. RETRIEVALS OF LWP AND T AND Q PROFILES 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 the NCEP forecast model, and the algorithm iterates until the residuals are less that the estimated GSR noise levels. These retrievals use zenith GSR data up to 183.31 GHz. 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. CONCLUSIONS • 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. ARM Science Team Meeting, March 10-14, 2008, Norfolk, VA Corresponding author: Ed.Westwater@colorado.edu