David H. Levinson

The International Best Track Archive for Climate Stewardship (IBTrACS): unifying tropical cyclone data.

The goal of the International Best Track Archive for Climate Stewardship (IBTrACS) project is to collect the historical tropical cyclone best-track data from all available Regional Specialized Meteorological Centers (RSMCs) and other agencies, combine the disparate datasets into one product, and disseminate in formats used by the tropical cyclone community. Each RSMC forecasts and monitors storms for a specific region and annually archives best-track data, which consist of information on a storms position, intensity, and other related parameters. IBTrACS is a new dataset based on the best-track data from numerous sources. Moreover, rather than preferentially selecting one track and intensity for each storm, the mean position, the original intensities from the agencies, and summary statistics are provided. This article discusses the dataset construction, explores the tropical cyclone climatology from IBTrACS, and concludes with an analysis of uncertainty in the tropical cyclone intensity record.

A Technique for Combining Global Tropical Cyclone Best Track Data

Abstract Best track data generally consist of the positions and intensities during the life cycle of a tropical cyclone. Despite the widespread interest in the distribution, frequency, and intensity of tropical cyclones worldwide, no publicly available central repository of global best track data from international agencies has been in existence. While there are numerous international centers that forecast tropical cyclones and archive best track data for their defined regions, most researchers traditionally use best track data from a very small subset of centers to construct global datasets and climatologies. This practice results in tropical cyclones that are either missed and/or misrepresented. While the process of combining positions and intensities from disparate data sources can be arduous, it is worthwhile and necessary in light of their importance. The nature of historical best track data is that they are prone to issues with intensity (maximum surface wind and minimum central pressure), especiall...

Archive Compiles New Resource for Global Tropical Cyclone Research

The International Best Track Archive for Climate Stewardship (IBTrACS) compiles tropical cyclone best track data from 11 tropical cyclone forecast centers around the globe, producing a unified global best track data set (M. C. Kruk et al., A technique for merging global tropical cyclone best track data, submitted to Journal of Atmospheric and Oceanic Technology, 2008). Best track data (so called because the data generally refer to the best estimate of a storms characteristics) include the position, maximum sustained winds, and minimum central pressure of a tropical cyclone at 6-hour intervals. Despite the significant impact of tropical cyclones on society and natural systems, there had been no central repository maintained for global best track data prior to the development of IBTrACS in 2008. The data set, which builds upon the efforts of the international tropical forecasting community, has become the most comprehensive global best track data set publicly available. IBTrACS was created by the U.S. National Oceanic and Atmospheric Administrations National Climatic Data Center (NOAA NCDC) under the auspices of the World Data Center for Meteorology.

Toward a Homogenous Global Tropical Cyclone Best-Track Dataset

What: Representatives, data managers, and tropical cyclone researchers from agencies and organizations around the globe that provide tropical cyclone best-track data met to discuss and improve the historical record of tropical cyclones. When: 5–7 May 2009 Where: Asheville, North Carolina despite the numerous articles in peer-reviewed literature using global tropical cyclone (TC) best-track datasets, until recently there existed no central repository of these data. Many researchers simply used best-track data from two sources to obtain global coverage: National Oceanic and Atmospheric Administration’s (NOAA) Hurricane Database (HURDAT) for the North Atlantic and eastern North Pacific basins, and the U.S. Navy/Air Force Joint Typhoon Warning Center (JTWC) for all other basins. Aside from the many issues in combining data from just these two sources, doing so excludes data from most of the World Meteorological Organization (WMO) Regional Specialized Meteorological Centres (RSMC) and TC Warning Centres (TCWC), which also officially forecast and monitor TCs. Furthermore, there are similar best-track datasets from other sources. However, the two primary issues that have hindered scientists from using all available global data are 1) easily accessing the best-track data and 2) accurately combining these disparate datasets. The International Best Track Archive for Climate Stewardship (IBTrACS) project was formed under the auspices of the World Data Center for Meteorology– Asheville (WDC–Asheville) to address the best-track data accessibility issue by combining TC best-track data from all agencies into an integrated dataset readily available to the user community. Figure 1 denotes the number of agencies tracking TCs by basin. [Also see page 363 in this issue.] Note that there are numerous sources of TC intensity in the Southern Hemisphere and western North Pacific, which complicates data access and analysis. Therefore, the new IBTrACS dataset (Knapp et al. 2010; Kruk et al. 2010) provides the original TC intensities in a uniform format and catalogs the full range of reported values for pressure, wind speed, and position for each 6-h time step from each agency. The final dataset is available in a variety of formats in use by the TC community, which includes the original unedited data as received from each of the RSMCs. AFFILIATIONS: Levinson, DiamonD, anD Knapp—NOAA/ National Climatic Data Center, Asheville, North Carolina; KruK—STG, Inc., Asheville, North Carolina; Gibney—IMSG, Inc., Asheville, North Carolina CORRESPONDING AUTHOR: David H. Levinson, NOAA/ National Climatic Data Center, 151 Patton Avenue, Asheville, NC 28801 E-mail: david.levinson@noaa.gov The abstract for this article can be found in this issue, following the table of contents.

Evaluation of NEXRAD Radar Precipitation Products for Natural Resource Applications

Abstract Timing and amount of precipitation are principal drivers of most rangeland processes, but the availability of rainfall-gauge data over extensive rangelands, particularly in the western United States, is limited. The National Weather Service (NWS), Department of Defense, and Federal Aviation Administration operate a network of Doppler radar stations that produce hourly rainfall estimates, at approximately 16-km2 resolution, with nominal coverage of 96% of the conterminous United States. Internal utilization of these data by the three agencies is primarily for the detection and modeling of extreme weather events. The usefulness of these data for external hydrologic and natural resource applications is limited by a lack of tools for decoding and georeferencing digital precipitation data products. We modified NWS source code to produce decoding and georeferencing tools and used them to evaluate radar precipitation data for the Boise (CBX) radar relative to gauges in the Snake River Plain of southwestern Idaho for the period January 1998 to May 2004. The relationship between radar and gauge precipitation estimates changed after a revision of radar-processing protocols in 2002 and 2003. Cumulative radar precipitation estimates made prior to November 2002 underestimated gauge readings by 50%–60%. Subsequent radar data overestimated cumulative gauge precipitation by 20%–40%. The radar, however, detected precipitation during significantly fewer hours than were detected by the gauge network both before and after programming changes. Additional modification of NWS precipitation-processing procedures might improve accessibility and utility of these data for rangeland management and natural resource modeling applications. Currently available data can still be very useful for estimating high-intensity events that greatly affect processes such as soil erosion and flooding.

Pacific Storms Climatology Products (PSCP): Understanding Extreme Events

E xtreme events: the f loods that displace us from our homes, the high waves that wash out coastal roads, or the toppling of trees and power poles from a passing storm. For locations around the Pacific Basin, where remote island chains sit perilously close to sea level and where rainfall is the primary source of water, questions arise concerning the return frequency and duration of such events, and whether or not they are getting more extreme. Understanding the long-term variability and change in coastal climate extremes has grown in public awareness given the potentially severe impacts related to sea-level rise coupled with coastal storms. To reduce vulnerability to the economic, social, and environmental risks associated with these phenomena, decision makers in coastal communities need timely access to accurate and contextually relevant information that affords them an opportunity to plan and respond accordingly. To address this need, the Pacific Storms Climatology Products (PSCP) project—or Pacific Storms— was established under the direction of the NOAA National Climatic Data Center (NCDC). Pacific Storms is focused on improving our understanding of patterns and trends in storm frequency and intensity—“storminess”—within the Pacific Basin. Pacific Storms is exploring how the climate-related processes that govern extreme storm events are expressed within and between three thematic areas: strong winds, heavy rains, and high seas. Theme-specif ic data integration and product development teams were formed to conduct analyses and create a broad suite of derived data products, which are publicly available online (www.pacificstormsclimatology.org). These teams included representatives from NCDC, as well as NOAA’s Center for Operational Products and Services (CO-OPS), Coastal Services Center (CSC), and National Weather Service (NWS), and the University of Hawaii, University of Alaska, University of Guam, and Oregon State University. Sources of information include NOAA’s Integrated Surface Hourly (ISH) mean sea-level pressure and wind speed data, the Global Historical Climate Network-Daily (GHCN-D) precipitation dataset, the National Water Level Observing Network (NWLON) tide gauge records, the University of Hawaii Sea Level Center (UHSLC) Joint Archive for Sea Level research quality dataset and Global Sea Level Observing System (GLOSS)/Climate Variability and Predictability (CLIVAR) “fast delivery” sea level dataset, the National Data Buoy Center (NDBC) wave buoy records, the U.S. Army Corps of Engineers’ Coastal Data Information (CDIP) buoy data, and other data sources. The data analysis and product development framework and guidelines outlined below are innovative in a number of ways. First, they focus on extreme events, and integrate data and products across a range of storm-related phenomena. Furthermore, they also paint a comprehensive picture of changes and variation in extreme-event magnitude and frequency for a mix of theme-specific parameters on seasonal, annual, and interannual time frames. The resulting extremes climatology datasets are unique, as are some of the specific products. Finally, success of the project is fundamentally tied to the collaborative efforts of the data integration and product development teams.

A Climatology of Inland Winds from Tropical Cyclones for the Eastern United States

Tropicalcyclonesposeasignificantthreat tolife andpropertyalongcoastalregionsof theUnitedStates.As these systems move inland and dissipate, they can also pose a threat to life and property, through heavy rains, highwinds,andothersevereweathersuchastornadoes.Whilemanystudieshavefocusedontheimpactsfrom tropical cyclones on coastal counties of the United States, this study goes beyond the coast and examines the impacts caused by tropical cyclones on inland locations. Using geographical information system software, historical track data are used in conjunction with the radial maximum extent of the maximum sustained winds at 34-, 50-, and 64-kt (1 kt ’ 0.5 m s 21 ) thresholds for all intensities of tropical cyclones and overlaid on a 30-km equal-area grid that covers the eastern half of the United States. The result is a series of maps with frequency distributions and an estimation of return intervals for inland tropical storm‐ and hurricane-force winds. Knowing where the climatologically favored areas are for tropical cyclones, combined with a climatological expectation of the inland penetration frequency of these storms, can be of tremendous value to forecasters, emergency managers, and the public.

The International Best Track Archive for Climate Stewardship (IBTrACS) Project: Overview of Methods and Indian Ocean Statistics

Despite the widespread interest in data that describes the distribution, frequency, and intensity of tropical cyclones worldwide, until recently no central repository for official data existed. Currently, there are six Regional Specialized Meteorological Center’s (RSMC) and five Tropical Cyclone Warning Centers (TCWC) that forecast and monitor each of the tropical-cyclone-prone basins worldwide. On an annual basis each center analyzes and archives best track (BT) data: information on tropical cyclone positions, intensities, as well as other related parameters. To rectify this situation, the International Best Track Archive for Climate Stewardship (IBTrACS) Project was developed by NOAA’s National Climatic Data Center under the auspices of the World Data Center for Meteorology, Asheville to collect and disseminate the historical tropical cyclone BT data from all available sources, merging the disparate data into one comprehensive dataset for the user community (Kruk et al. 2009). Unlike any other global tropical cyclone best track dataset, IBTrACS utilizes complex merging techniques, which necessarily account for the inherent differences between BT datasets while applying objective quality control procedures to flag potentially erroneous data points. Therefore, one of the primary goals of the IBTrACS project is for the data processing methods to remain open, such that desired user feedback on data quality can be collected more readily and assessed. In addition, data provenance is completely recorded in IBTrACS so that all observations and corrections, either through rigorous quality control or through user feedback, may be tracked and provided to users. This article will summarize the purpose and vision of the project, the methods used to merge the data, and discuss results of computed basin-wide tropical cyclone statistics for both the North and South Indian Ocean basins.

Combining Tropical Cyclone Data Sets Worldwide: International Best Track Archive for Climate Stewardship (IBTrACS) Workshop; Asheville, North Carolina, 5–7 May 2009

At the International Best Track Archive for Climate Stewardship (IBTrACS) workshop in North Carolina, experts from the World Meteorological Organizations (WMO) officially recognized tropical cyclone tracking and forecasting agencies met to discuss ways to accurately combine the disparate tropical cyclone (TC) best track data to better understand their global climatology. Representatives from each participating agency provided an overview of their agencys operating procedures and how those procedures have changed over time. Breakout sessions addressed many issues, including wind-pressure relationships and their use, converting between wind speed averaging periods, and other differences between best track data sets.