Comments on “Scatterometer-Based Assessment of 10-m Wind Analyses from the Operational ECMWF and NCEP Numerical Weather Prediction Models”

Abstract

We have noted with interest the series of scatterometer data studies carried out by Chelton, Freilich, and colleagues [see, e.g., Chelton et al. (2004), Freilich and Dunbar (1999), and in particular, Chelton and Freilich (2005, hereafter CF05)]. In CF05, the authors addressed at least three pressing needs. They provided a much-needed quantification of the gross, or bulk, error statistics of scatterometer observations. Equally as significant, they also showed that the use of scatterometer observations improved the accuracy of 10-m wind analyses and predictions in two of the major global numerical weather prediction (NWP) systems, namely those of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP). Finally, CF05 presented a lucid and in-depth description of scatterometer instrument technology, which we suspect will make CF05 required reading for users of scatterometer observations. Before CF05, most of the literature on these three topics was confined to conference proceedings and various technical and other reports. Here, we present work that is complementary to that of CF05. We describe our experience with scatterometer data in both operations and research over a specific part of the globe. Our operational and research goals are very different from the topics covered in CF05. Unlike CF05, we do not focus on the gross statistics of the scatterometer observations, but instead on the capacity of scatterometer data to detect, monitor, and provide more accurate analyses and predictions of individual severe and extreme weather events on a routine basis. We do so largely by describing two case studies, chosen from many that we have investigated, which demonstrate clearly the value of scatterometer observations for weather systems in data-sparse oceanic and coastal areas. We welcome comments from the authors of CF05 on the results we present below. Our domain of interest is not global, but it is still a substantial region, covering the East Indian Ocean, the Southern Ocean, and the southwest Pacific Ocean, including the Tasman Sea. The region also spans a large range of latitudes, extending from the high latitudes, through the subtropics to the Tropics, and has a longitudinal extent from about 65° to 170°E. This region is very active meteorologically; however, it has been relatively neglected until recent years. It contains a number of countries that are routinely and adversely affected by severe weather, and there has long been exceptionally poor oceanic data coverage. The consequences of the data paucity include inaccurate initial analyses and subsequent operational forecast failures of NWP predictions on short-, medium-, and extended-range time scales. These failures usually occur when success is most needed. There have also been almost insurmountable problems in developing reliable climatologies, both atmospheric and oceanographic. In this correspondence, we concentrate only on the intense cyclonic systems that regularly generate severe and extreme weather, as these have the most impact Corresponding author address: Lance M. Leslie, School of Meteorology, University of Oklahoma, 100 E. Boyd Street, Room 1310, Norman, OK 73019-1013. E-mail: lmleslie@ou.edu FEBRUARY 2006 N O T E S A N D C O R R E S P O N D E N C E 737