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Knapp K.R.,National Oceanic and Atmospheric Administration | Kruk M.C.,STG Inc | Levinson D.H.,National Oceanic and Atmospheric Administration | Diamond H.J.,National Oceanic and Atmospheric Administration | Neumann C.J.,National Oceanic and Atmospheric Administration
Bulletin of the American Meteorological Society | Year: 2010

The IBTrACS dataset is the result of a globally coordinated and collaborative project. IBTrACS provides the first publicly available centralized repository of global tropical cyclone best-track data from the RSMCs and other agencies. In combining the disparate datasets, IBTrACS uses objective techniques that necessarily account for the inherent differences between international agencies. Unlike any other global tropical cyclone best-track dataset, IBTrACS provides a measure of the interagency variability, which helps Lo identify uncertainty in the tropical cyclone record. While IBTrACS is not a reanalysis (e.g., Fernandez-Partagas and Diaz 1996; Harper et al. 2008b; Landsea et al. 2004), the derived uncertainty metrics can serve as a stepping stone in identifying those tropical cyclones that are in most need of reanalysis. As IBTrACS data stand, numerous inhomogeneities exist in the intensity record due to interagency differences in available technologies, observations, and procedures over time. For example, inhomogeneities were introduced when various satellite data became available at an agency or when forecasters were trained in different analysis techniques. As discussed in LDK, efforts are underway at NCDC to document the operating procedures at the various RSMC and forecast offices, with an emphasis on changes in processes or capabilities that affect dataset homogeneity. Finally, IBTrACS is expandable to allow for inclusion of other best-track datasets that may become available. This allows input from individuals and/or agencies that have yet to make best-track data available. IBTrACS could become even more useful by including other information on global tropical cyclones. For example, nondeveloping storm tracks could be included for the tropical cyclone forecasting community in a future version. Such data are necessary to compile statistical tropical cyclone intensity prediction models (e.g., DeMaria and Kaplan 1999). Furthermore, some agencies provide non-6-h analyses and other storm parameters (such as radius of maximum winds, storm size, eye diameter, and radius of the outermost closed isobar), which could be incorporated into IBTrACS, making it more useful to surge and wave modelers, emergency managers, and reinsurance groups. (To download the freely available IBTrACS dataset, visit www.ncdc.noaa.gov/oa/ibtracs/.). © 2010 American Meteorological Society. Source

Knapp K.R.,National Oceanic and Atmospheric Administration | Kruk M.C.,STG Inc
Monthly Weather Review | Year: 2010

Numerous agencies around the world perform postseason analysis of tropical cyclone position and intensity, a process described as "best tracking." However, this process is temporally and spatially inhomogeneous because data availability, operational techniques, and knowledge have changed over time and differ among agencies. The net result is that positions and intensities often vary for any given storm for different agencies. In light of these differences, it is imperative to analyze and document the interagency differences in tropical cyclone intensities. To that end, maximum sustained winds from different agencies were compared using data from the International Best Track Archive for Climate Stewardship (IBTrACS) global tropical cyclone dataset. Comparisons were made for a recent 5-yr period to investigate the current differences, where linear systematic differences were evident. Time series of the comparisons also showed temporal changes in the systematic differences, which suggest changes in operational procedures. Initial attempts were made to normalize maximum sustained winds by correcting for known changes in operational procedures. The result was mixed, in that the adjustments removed some but not all of the systematic differences. This suggests that more details on operational procedures are needed and that a complete reanalysis of tropical cyclone intensities should be performed. © 2010 American Meteorological Society. Source

Shi L.,National Oceanic and Atmospheric Administration | Peng G.,STG Inc | Bates J.J.,National Oceanic and Atmospheric Administration
Journal of Atmospheric and Oceanic Technology | Year: 2012

High-latitude ocean surface air temperature and humidity derived from intersatellite-calibrated High- Resolution InfraredRadiation Sounder (HIRS)measurements are examined. Aneural network approach is used to develop retrieval algorithms. HIRS simultaneous nadir overpass observations from high latitudes are used to intercalibrate observations from different satellites. Investigation shows that if HIRS observations were not intercalibrated, then it could lead to intersatellite biases of 1°Cin the air temperature and 1-2 g kg -1 in the specific humidity for high-latitude ocean surface retrievals. Using a full year of measurements from a high-latitude moored buoy site as ground truth, the instantaneous (matched within a half-hour) root-mean-square (RMS) errors of HIRS retrievals are 1.50°C for air temperature and 0.86 g kg -1 for specific humidity. Compared to a large set of operational moored and drifting buoys in both northern and southern oceans greater than 508 latitude, the retrieval instantaneous RMS errors are within 2.6°C for air temperature and 1.4 g kg -1 for specific humidity. Compared to 5 yr of International Maritime Meteorological Archive in situ data, the HIRS specific humidity retrievals show less than 0.5 g kg -1 of differences over the majority of northern high-latitude open oceans. © 2012 American Meteorological Society. Source

Groisman P.Y.,National Oceanic and Atmospheric Administration | Knight R.W.,STG Inc | Karl T.R.,National Oceanic and Atmospheric Administration
Journal of Hydrometeorology | Year: 2012

In examining intense precipitation over the central United States, the authors consider only days with precipitation when the daily total is above 12.7 mm and focus only on these days and multiday events constructed from such consecutive precipitation days. Analyses show that over the central United States, a statistically significant redistribution in the spectra of intense precipitation days/events during the past decades has occurred. Moderately heavy precipitation events (within a 12.7-25.4 mm day -1 range) became less frequent compared to days and events with precipitation totals above 25.4 mm. During the past 31 yr (compared to the 1948-78 period), significant increases occurred in the frequency of "very heavy" (the daily rain events above 76.2 mm) and extreme precipitation events (defined as daily and multiday rain events with totals above 154.9 mm or 6 in.), with up to 40% increases in the frequency of days and multiday extreme rain events. Tropical cyclones associated with extreme precipitation do not significantly contribute to the changes reported in this study. With time, the internal precipitation structure (e.g., mean and maximum hourly precipitation rates within each preselected range of daily or multiday event totals) did not noticeably change. Several possible causes of observed changes in intense precipitation over the central United States are discussed and/or tested. © 2012 American Meteorological Society. Source

Arguez A.,National Oceanic and Atmospheric Administration | Durre I.,National Oceanic and Atmospheric Administration | Applequist S.,National Oceanic and Atmospheric Administration | Vose R.S.,National Oceanic and Atmospheric Administration | And 4 more authors.
Bulletin of the American Meteorological Society | Year: 2012

The authors kindly acknowledge C. Williams and M. Menne for providing the adjusted monthly temperature values used in the computation of all temperature-related normals, and J. Crouch and B. Korzeniewski for providing valuable feedback on an earlier version of this manuscript. We also commend T. Whitehurst and N. Guttman for pioneering work on prior installments of NOAA's Climate Normals. Most importantly, we thank the legion of individuals-many of them volunteers-who perform the diligent and often thankless job of recording weather observations every single day. There could be no climate normals without their dedication. © 2012 American Meteorological Society. Source

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