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Michael Chenoweth

Abstract

The nonstandard thermometer exposure practices at 118 United States cooperative weather stations in 1883 and at 394 stations in 1903 are documented from one unpublished source and one published source. Changes in the exposure practices that resulted from the introduction of the Cotton Region Shelter (CRS) in the 1880s are described. As of 1883, there were five types of thermometer exposure in use at cooperative stations: (i) screened thermometers in freestanding screens (9.9% of all exposures); (ii) screened thermometers attached to north-facing walls and windows (23.3% of all exposures); (iii) unscreened thermometers attached to walls and window casements (50.0% of all exposures); unscreened thermometers attached to porch columns and separated from the main body of the building (13.9% of all exposures), and (iv) “Glaisher-type” stands and exposures (2.7% of all exposures). By 1903, 77.7% of all stations used free-standing screens, and 14.5% used north wall screens; the remaining stations (7.8%) did not use a screen. Free-standing screens were almost certainly not in use at cooperative stations prior to 1881.

In addition, the following features of nonstandard exposures are documented: thermometer bulb heights above ground, the wall azimuth of thermometers, the construction material of the buildings on which the thermometers were exposed, the placement of thermometers with respect to the type of building material and to windows and walls, as well as the susceptibility to artificial heat bias. Based on the details of thermometer exposure practices in the nineteenth century, the published literature, and early results from new field studies in England, which attempt to reproduce historic nonstandard exposures, a positive average annual temperature bias of 0.2°−0.3°C is estimated for the years preceding the late 1890s; the bias probably falls to near 0°C by 1903.

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Michael Chenoweth
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Michael Chenoweth

Abstract

A comprehensive new compilation of North Atlantic tropical cyclone activity for the years 1851–98 is presented and compared with the second-generation North Atlantic hurricane database (HURDAT2) for the same years. This new analysis is based on the retrieval of 9072 newspaper marine shipping news reports, 1260 original logbook records, 271 Maury abstract logs, 147 U.S. marine meteorological journals, and 34 Met Office (UKMO) logbooks. Records from throughout North America and the Caribbean region were used along with other primary and secondary references holding unique land and marine data. For the first time, North Atlantic daily weather maps for 1864/65, 1873, and 1881–98 were used in historical tropical cyclone research. Results for the years 1851–98 include the omission of 62 of the 361 HURDAT2 storms, and the further reduction resulting from the merging of storms to a total of 288 unique HURDAT2 tropical cyclones. The new compilation gave a total of 497 tropical cyclones in the 48-yr record, or an average of 10.4 storms per year compared to 6.0 per year in HURDAT2 less the author’s omissions. Of this total, 209 storms are completely new. A total of 90 hurricanes made landfall in the United States during this time. Seven new U.S. landfalling hurricanes are present in the new dataset but not in HURDAT2. Eight U.S. landfalling hurricanes in HURDAT2 are now considered to have only tropical storm impact or were actually extratropical at landfall. Across the North Atlantic, the number of category-4 hurricanes based on the Saffir–Simpson hurricane wind scale, compared with HURDAT2, increased from 11 to 25, 6 of which made U.S. landfall at category-4 level.

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Michael Chenoweth

Abstract

A discussion of the history of thermometer exposure in the United States in the nineteenth and early twentieth century documents a wide variety of exposure types. The different exposures have likely contributed to heterogeneities in datasets that have been assumed to be relatively homogeneous.

A field experiment was performed in order to determine the difference in temperature reading as measured in a cotton region shelter (CRS) and an unscreened thermometer in a “north-wall” exposure, which was the most common type of thermometer exposure in the United States during the nineteenth century. Systematic differences in temperature between the two sites throughout the year are likely related to the different responses of each site to the annual cycle of the radiation budget. The average annual temperature (calculated from max +min/2) is about 0.5°C higher in the CRS, and if representative for the United States as a whole means, that nineteenth century temperature records have a cold bias due to differences in thermometer exposure. However, a definite conclusion cannot yet be made due to evidence of significant positive biases in some nineteenth century U.S. temperature records.

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Michael Chenoweth

Weather data extracted from the logbooks of 227 ships of opportunity are used to document the state of the global climate system in the summer of 1816 (“The Year Without a Summer”). Additional land-based data, some never before used, supplement the marine network. The sources of the data are given and briefly discussed.

The main highlights of the global climate system in the 3-year period centered on the summer of 1816 include:

  • a cold-phase Southern Oscillation (SO) (La Niña) event in the Northern Hemisphere (NH) winter of 1815–16, which was preceded and followed by warm-phase SO (El Nino) events in the winters of 1814/15 and 1816/17;
  • strong Asian winter and summer monsoons, which featured anomalous cold in much of south and east Asia in the winter of 1815/16 and near- or above-normal rains in much of India in the summer of 1816;
  • below-normal air temperatures (1°–2°C below 1951–80 normals) in parts of the tropical Atlantic and eastern Pacific (in the Galapagos Islands), which imply below-normal sea surface temperatures in the same areas;
  • a severe drought in northeast Brazil in 1816–17;
  • an active and northward-displaced intertropical zone in most areas from Mexico eastward to Africa;
  • generally colder-than-normal extratropical temperature anomalies in both hemispheres;
  • an area of anomalous warmth (1°–2°C above 1951–80 normals) in the Atlantic between Greenland and the Azores during at least the spring and summer of 1816; and
  • an active Atlantic hurricane season in both 1815 and 1816.

A general circulation model simulation of the spatial patterns of high latitude NH temperature anomalies in the first winter following a major volcanic eruption (Graf et al. 1993) is not fully supported by the results in the North American sector where warming in Greenland was observed in 1816, as the GCM indicates cooling. The area of maximum cooling over North America near 50°N, 90°W in 1816 is north of the GCM results. This second difference may be partly attributed to the effects of the cold-phase SO (La Nina) event superimposed on the volcanic signal. Elsewhere in North America, Asia, and Europe, there is generally good agreement between the observed patterns and the GCM results.

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Michael Chenoweth and Christopher Landsea

On 2 October 1858, estimated sustained hurricane-force winds produced by a tropical cyclone located a short distance offshore were felt in San Diego, California. Unprecedented damage was done in the city and was described as the severest gale ever felt to that date, and it has not been matched or exceeded in severity since. A “southeaster” and high seas from the diminishing tropical cyclone were also felt in the night of 2–3 October at San Pedro (the port serving Los Angeles), California, with shipping interests lightly damaged. The hurricane-force winds at San Diego are the first and only documented instance of winds of this strength from a tropical cyclone in the recorded history of the state. Available evidence suggests that the hurricane tracked just offshore from San Diego, without the eye coming inland, but close enough to produce damaging winds along the entire coast from San Diego to Long Beach, California. The rediscovery of this storm is relevant to climate change issues and the insurance–emergency management communities risk assessment of rare and extreme events in the region.

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Cary J. Mock, Michael Chenoweth, Isabel Altamirano, Matthew D. Rodgers, and Ricardo García-Herrera

Major hurricanes are prominent meteorological hazards of the U.S. Atlantic and Gulf coasts. However, the official modern record of Atlantic basin tropical cyclones starts at 1851, and it does not provide a comprehensive measure of the frequency and magnitude of major hurricanes. Vast amounts of documentary weather data extend back several centuries, but many of these have not yet been fully utilized for hurricane reconstruction. These sources include weather diaries, ship logbooks, ship protests, and newspapers from American, British, and Spanish archives. A coordinated effort, utilizing these historical sources, has reconstructed a major hurricane in August 1812, which is the closest to ever pass by New Orleans, Louisiana, including Hurricane Katrina. The storm became a tropical depression in the Caribbean Sea, passed south of Jamaica as a tropical storm, and then strengthened to hurricane strength in the Gulf of Mexico. It made landfall about 65 km southeast of New Orleans and passed just to the west of the city. Historical storm surge and damage reports indicate it as a major hurricane at landfall. Given that conditions during 1812 include having lower sea level, higher land elevation prior to human-induced subsidence, and more extensive wetlands, a recurrence of such a major hurricane would likely have a greater detrimental societal impact than that of Hurricane Katrina. The 1812 hurricane study provides an example of how historical data can be utilized to reconstruct past hurricanes in a manner that renders them directly comparable with those within our modern record.

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Christopher W. Landsea, Steve Feuer, Andrew Hagen, David A. Glenn, Jamese Sims, Ramon Perez, Michael Chenoweth, and Nicholas Anderson

Abstract

A reanalysis of the Atlantic basin tropical storm and hurricane database (“best track”) for the period from 1921 to 1930 has been completed. This reassessment of the main archive for tropical cyclones of the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico was necessary to correct systematic biases and random errors in the data as well as to search for previously unrecognized systems. The methodology for the reanalysis process for revising the track and intensity of tropical cyclone data has been detailed in a previous paper on the reanalysis. The 1921–30 dataset now includes several new tropical cyclones, excludes one system previously considered a tropical storm, makes generally large alterations in the intensity estimates of most tropical cyclones (both toward stronger and weaker intensities), and typically adjusts existing tracks with minor corrections. Average uncertainty in intensity and track values is estimated for both open-ocean conditions as well as landfalling systems. Highlights are given for changes to the more significant hurricanes to impact the United States, Central America, and the Caribbean for this decade.

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Christopher W. Landsea, David A. Glenn, William Bredemeyer, Michael Chenoweth, Ryan Ellis, John Gamache, Lyle Hufstetler, Cary Mock, Ramon Perez, Ricardo Prieto, Jorge Sánchez-Sesma, Donna Thomas, and Lenworth Woolcock

Abstract

A reanalysis of the Atlantic basin tropical storm and hurricane database (“best track”) for the period of 1911–20 has been completed. This reassessment of the main archive for tropical cyclones of the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico was necessary to correct systematic biases and random errors in the data as well as to search for previously unrecognized systems. A methodology for the reanalysis process for revising the track and intensity of tropical cyclone data is provided in detail. The dataset now includes several new tropical cyclones, excludes one system previously considered a tropical storm, makes generally large alterations in the intensity estimates of most tropical cyclones (both toward stronger and weaker intensities), and typically adjusts existing tracks with minor corrections. Average errors in intensity and track values are estimated for both open ocean conditions as well as for landfalling systems. Finally, highlights are given for changes to the more significant hurricanes to impact the United States, Central America, and the Caribbean for this decade.

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