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Randall S. Cerveny

Charles Darwin, as a trained naturalist and observer, recorded many intriguing meteorological phenomena during the voyage of the H.M.S. Beagle around the world from 1831 to 1836. Unfortunately, the scientific community has, in general, neglected these observations. In particular, Darwin logged interesting notes on lightning suppression and damage, on the aerial transport of dust, and on rainfall and drought periodicities across South America. The latter observations, addressing simultaneous drought occurrence in diverse parts of the world, may be among the first scientific speculations on climate variability and regional teleconnectivity associated with El Nino-Southern Oscillation. Credit for the first scientific observations of the ENSO phenomenon is usually given to researchers in the late nineteenth century.

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Randall S. Cerveny

A chronology of the meteorological events described by Homer in the Odyssey following the Achæans' conquest of Troy (ca. 1200 B.C.) is developed. Application of polar front theory to the voyages of six separate fleets as they sailed from Troy provides a unique test of the factual nature of a portion of the epic. Nothing beyond the limits of accepted meteorological theory occurred during the first 18 days following the departure from Troy. The Odyssey consistently shows a credible set of weather observations. Evidence suggests that the tragedies experienced by the Achaeans in the Odyssey may have been caused by a cyclonic storm crossing the area in the early summer. If the Achæans' initial travels after the conquest of Troy are factual, the chronology developed in this study extends our knowledge of daily weather events to an earlier time than has previously been available and creates a new component in the global history of climate and weather. A description in the Odyssey of a possible microburst event is also presented.

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Randall S. Cerveny and Jay S. Hobgood

The log of the first voyage of Christopher Columbus to the New World provides valuable information on the meteorological conditions of September 1492. Comparison and analysis of the descriptive accounts of weather made by Columbus and his pilots to other available Columbian and modern data leads to two distinct perspectives on the Columbian voyage: an examination of the frequency of “calm” events, and an analysis of the lack of tropical storm activity. The major conclusions of the first portion of the study include: 1) The Columbian pilots' descriptions of “calms” related to travel slower than travel occurring during other portions of the voyage. That rate of travel compares favorably to calm winds and an oceanic current of 0.4 knots, a value close to modern-day values; 2) The frequency of “calm” events experienced by Christopher Columbus in 1492 is significantly higher than the most liberal estimates of calms in the North Atlantic over the last 100 years; and 3) The locations of the Columbian calms are generally in the same region currently experiencing the highest frequency of calms. The main finding of the second portion of the study is that, based on historical hurricane records from 1886 to 1989, the center of a hurricane would have passed within 100 km of Columbus only once in the past 104 years. Inclusion of tropical storms increases this number to four out of 104 years. Therefore, while Columbus may indeed have been fortunate to have avoided severe weather during his voyage, the odds decidedly were in his favor. This Columbian “weather luck” was due to a combination of 1) encountering abnormally strong anticyclonic flow over the eastern North Atlantic, 2) starting late enough in the hurricane season to significantly decrease the probability of experiencing a hurricane, and 3) taking a north and easterly voyage, thereby avoiding the area of maximum hurricane occurrence.

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Randall S. Cerveny and Robert C. Balling Jr.

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No abstract available.

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Stephen J. Lavin and Randall S. Cerveny

Abstract

Gridded matrices of climatic data can be mapped by computer with a variety of symbolization methods, all of which have some shortcomings. A new mapping procedure, dot-density shading, is herein proposed as an alternative mapping form. Dot-density shading produces continuous-appearing dot patterns whose density is proportional to the data. Significant algorithms are those for computing dot numerosity and quasi-random dot placement. A number of application including data error detection and anomaly recognition are discussed.

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Merlin P. Lawson and Randall S. Cerveny

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Our objective is to evaluate the potential for extracting the maximum information contained in antecedent temperature patterns that operationally could be used in formulating winter seasonal forecasts in the United States. In particular, examination of the predictability of winter temperatures given autumn temperatures is made using derived contingency tables, discriminant equations of antecedent principal components, and canonical correlation analysis.

Contingency tables were constructed based on tercile classifications of a seventy-five year dependent record (1895–1969). Testing of an independent data period (1970–78) using these tables produced winter forecasts with no appreciable skill in the aggregate (−0.04). Discriminant analysis deprived linear combinations of the five principal components of the antecedent seasonal (autumn) temperatures to distinguish between specific terciles of the predictand season (winter). Despite encouraging results for the dependent period, forecast skill for the independent test period achieved no significant score (−0.04).

Unfortunately, both of these forms of analysis suffer imposed spatial limitations which restrict the scope of our investigation. Canonical correlation analysis is capable of relating the total spatial variance of fall temperatures to that of the winter temperatures for the entire United States. In this study, the technique was used to isolate seasonal patterns in winter temperature data that are correlated in time with fall temperature patterns for the same region. Summation of the first 20 canonical variate pairs suggests that autumn and winter temperatures over the continental United States are not closely related to one another.

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Robert C. Balling Jr. and Randall S. Cerveny

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No abstract available.

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Robert C. Balling Jr. and Randall S. Cerveny

Abstract

The purpose of this study was to analyze the time and space variations in long-term monthly-averaged daily percent possible solar radiation levels in the United States. Both principal components analysis and harmonic analysis were used to identify the influences of various synoptic-scale climatological phenomena on solar radiation receipt. Generally, an annual cycle was found with maximum percent possible radiation levels occurring in July. In many regions the temporal variance structure deviated from this general annual cycle. The results, which are useful in both theoretical and practical studies, lead to a better understanding of the climatology of solar radiation in the United States.

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Jonny William Malloy and Randall S. Cerveny

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Phoenix, Arizona, observes a high summertime frequency for daily maximum 8-h ozone averages (DMO8) exceeding 70 parts per billion, resulting in nonattainment status by the U.S. Environmental Protection Agency. This study discusses the use of composite atmospheric sounding analysis (constructing average sounding conditions for specific recurring events) to forecast different air quality index daily ozone classifications, including “good,” “moderate,” and collectively categories exceeding the 2015 ozone standard. Composite sounding analysis, using the Phoenix 1200 UTC (0500 LST) rawinsonde data (2006–17), identifies “pollutant dispersion windows” for ozone accumulation or dispersal for Phoenix during the North American monsoon (July and August period). A favorable ozone exceedance atmosphere is associated with a “Four Corners high” synoptic pattern bringing relatively light winds at and below 700 hPa (≤4.5 ms−1) and higher easterly winds above (≤12.3 ms−1). Healthy ozone days (good category) are common when Pacific low pressure troughing over the western United States creates deep and faster westerly flow above the surface reaching speeds of 6.7 (19.5) m s−1 by 700 (200) hPa. Surprisingly, large standard deviations over 10°C for dewpoint temperature at midlevels (500–400 hPa) were determined for all three daily ozone classification ranges used in this study. Additionally, modest temperature deviations and mean differences are noted at significant pressure levels. Consequently, wind speed and direction are better indicators when forecasting ozone accumulation potential. These results are pertinent to air quality meteorologists responsible for disseminating ozone forecasts for heavily urbanized areas of the U.S. Southwest.

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Randall S. Cerveny and Lynn E. Newman

Abstract

Flooding from tropical cyclone (TC) precipitation has lead in recent years to massive death and loss of property. The identification of climatological linkages between rainfall and TC parameters through study of long-term records would be useful in (i) identifying seasonal predictive climatic parameters to TC development, (ii) producing better precipitation estimates for affected areas, and (iii) developing better parameterizations between storm intensity, latent heat release, and rainfall in hurricane models. This study uses a daily satellite-derived oceanic precipitation record from 1979 to 1995 to determine the rainfall associated with the Atlantic and North Pacific basins over that time period (877 TCs). These data, categorized into 2.5° × 2.5° ocean grid cells, were used to create two precipitation databases. The first uses the surrounding nine grid cells marked from the average position of the tropical cyclone on the day of observation, while the second uses only the center grid cell for the day (representative of only the inner-core precipitation). Strong relationships were found to exist between daily rainfall accumulation and a TC’s daily maximum surface wind speeds. The precipitation associated with the inner core is generally representative of the cyclone’s total rainfall. The relationship between the ratio of inner-core rainfall and the total storm rainfall with maximum surface winds demonstrates a U-shaped pattern. The inner-core precipitation accounts for nearly 35% of the total rain of the weakest TCs and also of the strongest hurricanes but less than 25% of the total rainfall for weak hurricanes. Forecasters can used rainfall relationships such as these to aid in heavy rainfall and flooding warnings for affected land areas.

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