Reviewer

Sid Boukabara (NOAA/NESDIS)

Road Map

The review intends to shed light on two aspects concerning cloud and precipitation observations:

• The current and future observations of clouds and precipitations. It should cover all data which can provide information about hydrometeors (e.g. optical thickness, density, particle size, shape, etc), precipitations and cloud 2D/3D distribution (e.g. cloud fraction, cloud top, cloud base, etc). The review will provide an exhaustive list of ground information (e.g. METAR), radar (reflectivities and doppler) and satellite observations (e.g. Geostationary, MODIS, AVHRR, AMSU, AIRS, IASI, CloudSat, Calipso, etc) and give an overview of the scale, information content, precision and benefits of each observation type. The work will leverage on past reviews, especially concerning remote sensing, and it will address instruments and satellite missions planned for the next decade. A specific chapter will be dedicated to higher resolution data (e.g. ARM sites, CloudSat, fileld campaigns, etc) and their potential for validation.

• The choice of observables for the cloud analysis system. The focus of this work is to study how different observations can be successfully "digested" within an operational data assimilation (DA) system. The question of non-linearity will be addressed, particularly for the radiative transfer model (RTM) in satellite data assimilation. The accuracy of the RTM and the range of linearity will be shown for various schemes. The literature comparing the assimilation of raw radiances and retrievals (practical advantages, specification of errors, information content, etc) will be summarized with a special focus on clouds and strategies to leverage experience from retrievals. Methods to account for the scales (both spatial and temporal) of the observations vs. the background errors could be presented and the "super-observations" in radar DA could be used as an example.

Non-exhaustive list of publications and earlier reviews

The Remote Sensing of Clouds and Precipitation from Space: A Review. Graeme Stephens, Christian Kummerow. J. Atmos. Sci., 64, 3742--3765.

A review of atmospheric aerosol measurements. Peter H. McMurry. Atmospheric Environment. Volume 34, Issues 12-14, 2000, pp 1959-1999. doi:10.1016/S1352-2310(99)00455-0

Measuring Cloud Properties from Space: A Review. William Rossow. 1989. Journal of Climate. Volume 2, Issue 3, pp 201-213.

Convective-scale assimilation of radar data: Progress and challenges. 2006. J. Sun. Q. J. R. Meteorol. Soc., 131, 3439-3463.

Comparison of progress in assimilating cloud-affected microwave radiances at NCEP, ECMWF, JMA and the Met Office. Min-Jeong Kim, Steve English, Peter Bauer, Alan Geer, Kozo Okamoto. NWP-SAF Report 2008.

The capability of 4D-var systems to assimilate cloud affected satellite infrared radiances. CHEVALLIER, F.; P. LOPEZ, A. M. TOMPKINS, M. JANISKOVA and E. MOREAU. 2004. Q. J. R. Meteorol. Soc.130: 917-931.

Retrieval of cloud parameters from satellite sounder data: a simulation study. EYRE, J.R. and W.P. MENZEL. 1989. J. Appl. Meteorol.28: 267-275.

Lessons learnt from the operational 1D+4D-Var assimilation of rain- and cloud-affected SSM/I observations at ECMWF. A. Geer, P. Bauer, P. Lopez. 2008. Q. J. R. Meteorol. Soc. 134, 1513-1525.