|
CHAPTER XXXII
CLIMATOLOGICAL CONDITIONS BEING AN ARTICLE BASED UPON WEATHER BUREAU OBSERVATIONS COVERING A PERIOD FROM 1871 TO 1909 - THE LOCATION OF OFFICE AND INSTRUMENTS - A CLIMATOLOGICAL SUMMARY - UNUSUAL WEATHER PHENOMENA - WARM AND COLD PERIODS - LENGTH OF GROWING SEASONS - UNUSUAL AMOUNTS OF RAINFALL - NOTABLE RIVER STAGES - REMARKABLE FLOOD STAGE. (Pictures included with this chapter are: Hon. J. H. Murphy, Levi Humphrey, Mrs. Clinton and Miss Anna Penrose watching the high water of March 10, 1886. From Scott House balcony.
By J. M. Sherier, Local Forecaster, Weather Bureau. This station was established on May 23, 1871, in the First National Bank building, situated at the southwest corner of Main and Second streets, the instruments being located in the northeast corner room on the third floor of that building. On April 1, 1890, the office was moved to rooms 49 and 50, third floor, of the Masonic Temple, located at the northeast corner of Third and Main streets. The removal to the present location was accomplished November 3, 1896, when rooms 5, 6, and 7 were occupied on the second floor of the Post Office building, at the southwest corner of Third and Perry streets. All instruments now located on the roof, with the single exception of the sunshine recorder which was added to the instrumental equipment only a few years ago, have remained in their present position since they were transferred from the Masonic Temple. However, owing to work preparatory to the erection of an addition to the office building, it became necessary, on January 25, 1910, to abandon room No. 5 and to occupy room No. 9 instead. The barometers were transferred from room No. 6 to room No. 7 on January 31st, but without causing any change in the elevation of those instruments. The thermometers, rain gauge, sunshine recorder, and the wind vane and anemometer are all exposed on the nearly flat roof of the present office building. The following climatological summary is a revision of the data contained on page 649 of Weather Bureau Bulletin Q, Climatology of the United States. Means of maxima and means of minima have been determined from observations for thirty-six years, 1874-1909. All other temperature data and all precipitation data, except snowfall, thirty-eight years, 1872-1909; snowfall, twenty-five years, 1885-1909.
CLIMATOLOGICAL NOTES While the accompanying table shows the absolute range in temperature to have been 133 degrees, or from twenty-seven degrees below to 106 degrees above zero, the normal annual range at Davenport is only about 110 degrees, the minimum temperature of the average winter being about fifteen degrees below zero and the maximum temperature of the usual summer about ninety-five degrees above zero. Previous to the record-breaking period of warm weather during the summer of 1901, the absolute maximum temperature was 100 degrees, recorded on July 26, 1894, and the absolute maximum since 1901 has been ninety-six degrees, registered on July 29 and August 14, 1909. The coldest period of the year in this locality is, on the average, from January 14th to January 23d, inclusive, when the normal temperature is but twenty degrees; the warmest period is from July 13th to July 25th, inclusive, during which time the daily normal is seventy-six degrees. The growing season is nearly six months long, extending from about April 22d, the average date of the last killing frost in spring, to about October 13th, the average date of the first killing frost in autumn. The latest killing frost of spring occurred on May 22d, and the earliest killing frost of autumn, on September 18th. The rainfall averages heaviest during the first few days of June, the normal for June 2d, 4th and 5th being 0.18 inch; the daily precipitation normals are least, and but about 0.03 inch from January 27th to January 31st. Of the annual amount of 32.8 inches, about two-thirds, or 21.5 inches of rain falls during the growing season, included in the months from April to September. Heavy downpours frequently attend the thunderstorms of summer, the precipitation furing a single disturbance of that kind sometimes exceeding the normal amount of rainfall for the entire month. On July 13-14, 1889, 5.18 inches of rain fell in twenty-four hours, and a twenty-four hour fall of 5.06 inches occurred on June 9-10, 1905. When it is remembered that an inch of rain is equal to 226,603 pounds, or to 27,154 gallons, of precipitation on each exposed acre of ground, some idea may be gained of the volume of water precipitated during one of these exceptionally severe storms. The highest velocity of the wind at the local office during the nearly forty years covered by its records was at the rate of seventy-two miles per hour, from the southwest, on September 7, 1872. One or more small houses in the western portion of Davenport were reported to have been blown over at that time and damage of a minor character was occasioned about the city, while the loss to the agricultural interests in this vicinity was considerable. There is no record of a visitation by any tornado, or other wind storm of sufficient violence to cause general and wide-spread loss of life and property. The known range in the Mississippi, at Davenport, has been 20.4 feet, or from 1.0 foot below the zero of the river gauge, on January 5, 1890, to 19.4 feet above zero, on June 27, 1892. The latter remarkable stage was due to the occurrence of exceptionally heavy rains at a time when a flood crest was approaching from Dubuque. The highest gauge reading in this city during the folly referred to was 0.8 foot above the maximum reading at Dubuque, where the passing of the flood crest on June 24th gave a reading of 18.6 feet. At the time of highest water the railroad lines along the river front were flooded to a depth of about two feet and the gas works and nearly all factories in the immediate vicinity of the stream were compelled to suspend operations. The highest stage known in this locality at any season is reported to have occurred in 1868, when an ice gorge caused the river to rise to 20.9 feet. Dangerously high water in this portion of the Mississippi is unusual, however, the last occurrence of the flood stage of fifteen feet having been during April, 1897. CHANGES IN CLIMATE Mr. Sherier has consented to allow the addition of a paper read by him before the Contemporary Club February 25, 1909. It deals with the most useful conversational topic in a manner at once scientific and colloquial. The paper was greatly enjoyed by the club and is now given wider reading: "What has become of our old-fashioned winters? Why do we no longer have the waist-deep snows that covered the ground for months at a time a generation ago, while unbroken periods of zero weather prevailed for several weeks during each cold season?" The representative of the Weather Bureau on duty at a northern station is asked these and similar questions so often that sometimes he is half inclined to wonder whether, after all, his records have deceived him and the climate is really undergoing some change. Along the south Atlantic and Gulf coasts, however, one may hear it just as positively asserted that the winters are becoming more severe; and, as proof of the correctness of this statement, it may be pointed out, for example, that orange trees which are said to have flourished formerly along the streets of Savannah, Ga., have been killed by the low temperatures of the last thirty or forty years and few are now to be found north of the Florida line. It does not seem possible that a gradual lowering of the temperature is taking place in the South and that, at the same time, the northern winters are growing milder. Upon looking over the great amount of data that has been collected by the U. S. Weather Bureau and by foreign meteorologists, the student can find little to sustain this general impression that a permanent change in climate if taking place. Evidently the casual observer is at fault. Those who have made an exhaustive study of climatology now generally agree that, in most cases, the belief in a climatic change is tracable to the tendency of the memory to dwell upon those events that produce the greatest impression at the time of occurrence, to the exclusion of intervening happenings of minor importance. All of the cold winters, hot summers and deep snows of a life time are recalled in porportion to their departures from the averages for the place under consideration, or according to the attention these phenomena attracted when they were observed. In reviewing the weather of a generation, the most notable events merge, as one authority states, in much the same way as do the telegraph poles in a railway perspective. The greater the period of time that is looked back over, the nearer the deep snows and marked cold waves appear to be, just as the poles seem to form a high fence at the point where the rails apparently come together. In an article written for the Sunday Magazine of the Chicago Record-Herald, published on march 25, 1906, R. DeC. Ward, Assistant Professor of Climatology at Harvard University, gives the following illustration of what he terms "the shortness of people's memories in the matter of weather conditions:" "During the winter just ended, which has attracted some attention because of its relatively mild temperatures and small snow-fall, people have been saying generally that the climate has certainly changed to a warmer one, and one of the Boston newspapers recently printed a symposium, to which several meteorological experts contributed signed articles, on the subject: 'Has Anything Happened to Our Old-Fashioned Winter?' the general impression on the part of the public being that something certainly has happened to it. "Only two years ago, in 1903-04, when there were frequent snow storms, when the cold was severe, and when the snow lay on the ground for some weeks, the winter was commonly designated as an 'old-fashioned' one. And at that time another Boston newspaper requested from the writer of the present article a discussion of the question. 'Why Has the Old-fashioned Winter Come Back Again?' People felt then that the climate had changed from a milder to a more severe one. Within three years, therefore, in New England, there have been two wholly divergent views on the part of the general public." Change of residence, either from one section to another, or from the country to the city, may also be responsible for the notion that there has been a change in climate. Marked differences in temperature and rainfall are to be found in places only a comparatively short distance apart, and the person who has paid but little attention to the study of climatololgy is apt to confuse the climate of one locality with that of another. Because early impressions are strongest, this appears to be especially true if the change has been made to a less rigorous climate. Our present mode of living undoubtedly has some influence upon our appreciation of weather conditions. In the modern dwelling, heated by furnace, steam or hot water, temperatures below zero do not produce discomfort, even though they do have a tendency to lengthen coal bills, while it is hard to efface from the memory the shivering and chattering that attended the hasty toilet made under such weather conditions in the frigid bedroom of earlier times. The effect of deforestation is usually mentioned first among the causes that are supposed to produce local changes in climate, and with a better show of reason than in the case of the other influences that are commonly supposed to have this result. The range in temperature is found to be slightly reduced over forests, while the rainfall is generally thought to be somewhat increased. There is much discussion, however, as to the influence of forests upon precipitation and temperature; but, as climatologists themselves do not fully agree upon this subject, it is so slight as to be imperceptible to the ordinary observer. The principal benefit of forests lies in their acting as reservoirs for the storage of water that would otherwise soon find its way into streams and out of the region where it was precipitated, and also in preventing erosion of the soil. Conversely, it is claimed that the breaking up of the soil and the planting of trees and other vegetation produce an increase in the rainfall of a locality, a theory that is nearly always advanced by those who maintain that the precipitation in the western regions of scanty rainfall is gradually becoming greater. In commenting upon an article by Mr. William E. Curtis, in which Mr. Curtis pointed out that the extreme limits of cultivation in Kansas had, between 1860 and 1905, been extended from Emporia, 110 miles west of the Missouri state line, to the eastern border of Colorado, Professor Cleveland Abbe, Editor of the Monthly Weather Review, says in the June, 1905, number of that publication: "It is not the increase of rainfall or the change in climate that has made Kansas habitable any more than it is the diminution of rainfall that has made Syria a desert. In the one case intelligent man has conquered the desert; in the other case ignorant men and oppressive rulers have allowed the desert climate to conquer them. As a rule, even without artificial irrigation, a good crop plant, such as wheat or maize, suitable to desert conditions can be evolved by a proper system of selection; when irrigation comes in to help, the sunny desert becomes a more profitable garden field than the moist climate of the seashore or the tropics. As a rule grain crops require plenty of sunshine, a soil of the right physical properties, and a very careful, systematic application of water. Formerly, the ideal wheat fields were in Egypt, with abundance of sunshine, a fine soil for retaining the water, and a periodic inundation and irrigation, regulated by the river Nile. Almost the same climatic conditions prevail throughout the basins of the Mississippi, Missouri, Saskatchewan, and McKenzie. The fertility of this great region is a matter that depend wholly upon human industry, and not on any change of climate." The popular belief that irrigation has an important effect upon the climate of not only the region where it is generally carried on, but upon that of the central valleys as well, seems to have gained adherents at a rate almost in proportion to the growth of those operations themselves. During the summer of 1901, when the entire middle west suffered from a prolonged period of intense heat, the announcement was made through the press that a well known meteorologist attributed that visitation to the irrigation operations in the semi-arid regions-a notion that was immediately confuted by the entire scientific staff of the Weather Bureau. Hot waves have occurred in previous seasons, but there has been no exceptionally warm summer since the one referred to, notwithstanding the astounding increase in the amount of land that has been put under irrigation since 1901. Many of the other notions concerning the effect of irrigation upon the climate of any extensive area are, without doubt, equally ridiculous. Only water from streams already flowing through those sections is used in irrigation, so that no additional moisture is brought in from the outside, though the available water is distributed in such a way that evaporation is facilitated. Scattered as the irrigation operations are over the Pacific slope and the Ricky mountain region, and including only a small percentage of that enormous stretch of territory, their effect upon climate must be insignificant. It is, nevertheless, apparent to everyone who takes but a passing interest in weather changes that there is a fluctuation in the meteorological elements from year to year, the last twelve months being warmer or colder, wetter or drier than the preceding period of the same length. Rainfall and temperature records, especially, frequently show excesses and deficiencies that recur with such regularity as to suggest wave motion. Paradoxical as it may seem, normal weather conditions are the exception instead of the rule. These frequent somewhat regular changes through several years have been the cause of untiring efforts on the part of many students of meteorology to establish come rule or formula for foretelling roughly the time of occurrence of droughts, floods and seasons of extreme heat or cold. Thus periods of seven years, eleven years, nineteen years, etc., have been computed, but these oscillations cannot be shown to be uniform and persistent. The investigator may find, when his hopes are highest, that the phases of such a wave or cycle disappear, without his being able to understand why the undulatory movement should have become lost in a long period of weather from which all semblance of regularity as to periodicity is missing. In Europe Bruckner has found a period of approximately thirty-five years in both temperature and rainfall, though the variations are slight, the temperature departures amounting to not more than 0.5' to 1.0' from the established mean. In order to establish the invariability of a climate, it is necessary, therefore, to examine meteorological records that have been maintained for a period long enough to cover the irregular and periodic changes. Continuous observations for nearly forty years, made by the Weather Bureau in every section of the United States, are now available to every one interested in climatology, and the matter of proving that a permanent progressive change in climate is not taking place is comparatively simple. A record of temperature and precipitation at Muscatine, Iowa, that should prove of special value to those interested in the climatic conditions of Davenport, Rock Island, and Moline, is to be found in the August, 1890, number of the Monthly Weather Review. The temperature observations, extending from January, 1839, to June, 1890, and the precipitation record, covering the period from January, 1846, to June, 1890, were by J. P. Walton, Rev. J. Ufford, S. Foster, and Prof. T. S. Parvin, Signal Service, voluntary and Smithsonian observers. The warmest of the entire fifty-one years included in the temperature observations was 1839, with a mean of 53', and the coldest were 1856 and 1875, with an average of 44.1' each. The mean temperature was also below 45' in 1847 and 1857, when the averages were 44.6' and 44.9', respectively. Other particularly warm years were 1840, 1846, 1861, and 1878, in all of which the mean was slightly above 50'. It is also found that the first twenty-five years of the fifty-year period from 1839 to 1888, inclusive, were warmer, on the average, than the last twenty-five years, the means being 47.9' and 47.5', respectively. The lowest mean during any winter month was 6.2', for January, 1857, though especially low temperatures also prevailed during 1856, 1875, 1883, and 1888, the mean for that month in all of these years being below 10', while the average for January during the whole period was 20.1'. The mean temperature at Muscatine during the winter months of the first twenty-six years in the period from 1839 to 1890, inclusive, were as follows: January, 21.8; February, 24.9'; December, 24.2'. In the second twenty-six years of the same period the means for these months were: January, 18.3'; February, 24.4'; December, 24.2'. The winter mean for the first half of the period of fifty-two years was 23.6', and for the second half, 22.3', the winters from 1839 to 1864 averaging 1.3' warmer than those from 1865 to 1890. The wettest year at this same station, from 1846 to 1889, inclusive, was 1851, with a total precipitation of 74.50 inches, and the driest was 1854, with but 23.66 inches. The least amount of precipitation in the month of January was 0.30 inch, in 1868. The wettest January was that of 1873, with a total of 8.59 inches, an excess of 6.57 inches over the mean for that month during the entire period of observation. Although the total precipitation during the first half of the period exceeded that of the last half, the means being 40.78 inches and 38.11 inches, respectively, against an average for the forty-four years of 39.27 inches, the difference was due mainly to the exceptionally wet summers of 1849, 1850 and 1851. During 1851, especially, the total rainfall during May, June, July, and August was 49.50 inches, or more than 10 inches greater than the normal for an entire year. The average total precipitation for the three winter months of December, January and February was 6.67 inches during the first twenty-two years and 6.11 during the last twenty-two years. There is nothing to indicate the character of precipitation, whether rain or snow, but the averages for January, when the temperatures are lowest, and the precipitation is most likely to be in the form of snow, were 1.75 inches in the first and 2.17 inches in the second half of the period. Arranging the precipitation for the forty years from 1850 to 1889 in pentads, in order to reduce the irregularities caused by notably wet or dry years, the highest average is found to be 50.31 inches for the five-year period from 1850 to 1854. The second highest average, 42.94 inches, occurred during the pentad 1880-84, and the lowest average for any pentad was 31.87 inches in 1870-74. The Muscatine record has been selected for discussion because of the length of the period covered, the early date at which the observations were begun, and the proximity of that city to Davenport. Unfortunately, temperature and precipitation data for Muscatine have not been published regularly since the middle of the year 1890. During the eighteen-year period beginning with 1872, when the first full year of Signal Service observations was made in Davenport, this city averaged somewhat warmer and drier than Muscatine, the means being as follows: Temperature-Davenport, 49.2'; Muscatine, 47.5'. Rainfall-Davenport, 35-43 inches; Muscatine, 38.52 inches. An excellent article that appeared in the Monthly Weather Review for May, 1904, entitled, "The Invariability of Our Winter Climate," by Mr. Wm. B. Stockman, at that time Chief of the Records Division of the Weather Bureau, Washington, D. C., and which has since been reprinted as a special publication of the Bureau, contains tabulated winter temperature data from ten selected stations for fifty winters, beginning with that of 1854-55. The observations cover only the territory from the Mississippi valley to the Atlantic coast, it being explained that in this section only could records of the necessary length be obtained. Since, for obvious reasons, it is impracticable to use extensive tabular matter in a paper of this kind, only the following paragraph which contains what is thought to be the most pertinent part of Mr. Stockman's conclusions as to a change in climate is quoted: "From a study of the departures given during the last past fifty years it will be seen that the contention that the winters of recent years are less rigorous than those of former years, at least so far as temperature is concerned, is not well founded, for at Cleveland, Ohio, and St. Louis, Missouri, the mean of the first and second twenty-five-year periods was the same as the fifty-year average; at Cincinnati the second period averaged 0.8' lower than the first period, while at the other stations the mean of the second twenty-five-year period was but a few tenths of a degree above the fifty-year average." Data compiled by Angot, showing the average dates of vintage at Dijon, France, from the fourteenth to the nineteenth century, indicate that the vintage season averaged earliest in the seventeenth and latest in the ninteenth century, the dates being October 24.5th and October 30th, respectively the range of the means amounting to only 5.5 days in the six hundred years. The next earliest average was October 25th, in the fourteenth and fifteenth centuries, while those given for the sixteenth and eighteenth centuries are October 28th and October 28.8th. Since the climate of a section is determined mainly by latitude, elevation, the varying topography, and the trend of mountain ranges, distance from large bodies of water, and the direction of prevailing winds, it would appear that average climatic conditions for ordinary periods of time should be nearly as constant as are these controlling factors themselves. |