ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1853 Ft. Snelling climatological record consists of: four daily fixed time readings taken from the station's "detached" thermometer; daily precipitation values; four daily fixed time sky cover observations; four daily fixed time observations of wind "force" and wind direction; four daily barometric readings; and four daily readings from the station's "attached" thermometer (i.e. from an indoor thermometer used to adjust barometric readings for the effects of temperature on the station's mercury barometer) . Temperature, sky cover, wind direction/force and barometric observations were taken at or about local sunrise, at or about 0900 hours, at or about 1500 hours and at or about 2100 hours local solar time. Although extant records give no explicit indication of the time at which 1853 precipitation observations were taken, contextual evidence suggests either a 2100-2100 schedule and/or an early morning (probably "sunrise") schedule (which, in at least in some instances, may have entailed "shifting" of precipitation values from the date on which the observation was actually made to the day immediately preceding).
So far as can be determined, 1853 Ft. Snelling temperature readings were taken from an instrument manufactured by George Tagliabue, New York City and precipitation observations were taken from a DeWitt rain gauge (which was probably mounted on a pole or post on the fort's parade ground). With the notable exception of summer readings taken at 0900 hours, fixed time temperature readings taken by Ft. Snelling observers during 1853 appear to be consistent with "normal" diurnal patterns (indicating that the station thermometer was, for the most part, located/sheltered as necessary to protect it from exposure to direct sunlight.
All 1853 wind force values are expressed in terms of a numeric wind force value selected by fort observers after visually noting the effect of wind on flags, trees, signs and other easily movable objects . The degree of cloudiness was similarly quantified, using a scale of zero (complete overcast) to ten (a totally cloudless sky) . Fort observers did not, however, keep a daily descriptive record of "fair" and "cloudy" days during 1853 (a practice which had been introduced earlier in the 1820-58 record, then dropped, temporarily re-instated in 1851 and dropped again in 1852).
Unlike the 1853 daily sky cover record (which includes a complete set of daily entries), the 1853 force of wind record is often incomplete: several air movement records include wind direction entries UNACCOMPANIED by corresponding numeric wind speed indicators. Extant records give no explanation for these lapses: perhaps the missing entries indicate a force of wind value of more than zero but less than one or, alternatively, that fort personnel, for whatever reason, were unwilling or unable to expend the time and effort required to take consistent wind speed observations.
Like corresponding records from the years immediately preceding, the 1853 Ft. Snelling record appears to significantly understate the number of days with precipitation and/or measurable precipitation. This suggests that -- following the example of their predecessors -- Fort observers did not routinely/consistently measure and/or record small precipitation events, sometimes either ignoring less significant deposits of rain or snow (or. alternatively, using terms such as "inappreciable", "unmeasurable" or "slight" to denote small, but perhaps otherwise measurable, amounts of precipitation). This tendency is particularly evident in records for the winter months of year: St. Paul newspaper accounts -- together with contextual evidence from the 1853 record itself -- suggest, in fact, that Fort observers, for whatever reason, failed to measure or record (or even note) a significant portion of the precipitation which fell during the winter months (and, to a lesser extent, probably the summer months as well).
Although the 1853 Fort Snelling record includes daily liquid/melted precipitation values and a record of the TYPE of precipitation observed, it contains NO QUANTITATIVE snowfall values (whether of fresh snowfall or accumulated snow cover). Therefore, unless otherwise noted, snowfall values contained in the foregoing compilation are ESTIMATES inferred from newspaper accounts of 1853 snowfall events and/or obtained by applying the National Weather Service meltwater-snowfall conversion matrix to the meltwater values recorded by Ft. Snelling observers on 1853 "snow days".
As noted previously, the 1853 Ft. Snelling record includes four daily readings taken from the station's mercury barometer and from the "attached" thermometer (readings which, also as noted above, were probably used to correct air pressure readings for the effects of temperature on the mercury in the station barometer). So far as can be determined, 1853 barometric values are station pressures (i.e. readings which have not been adjusted to compensate for elevation above mean sea level).
Analysis of the 1853 temperature record suggests that many warm season temperature values may have compromised by improper instrument exposure and/or erratic observational schedules. Specifically, fixed time temperature readings taken during the warm months of 1853 suggest an inordinate "compression" of daily readings taken at 0900 and 1500 hours. This suggests, of course, that the station thermometer may have been exposed to the mid-morning rays of the spring and summer sun and/or that observations were sometimes taken at times significantly different than the times indicated in the official record .
The foregoing 1853 climatological record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperature values. The unadjusted record, in turn, includes two monthly mean temperature values: a) the simple average of fixed time readings taken daily at or about sunrise, 0900, 1500 and 2100 hours; and b) the simple average of fixed time readings taken daily at sunrise, 1500 and 2100 ONLY. Because it disregards the often anomalous 0900 hour readings, the second set of unadjusted averages illustrates the extent to which sun contamination may have distorted 1853 temperature records. Adjusted averages are from Charles J. Fisk's 1984 "Reconstruction of Daily 1820-1872 Minneapolis-St. Paul Temperature Observations". These values were obtained by averaging statistically derived estimates of the daily maxima and minima which would have been recorded had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight . The foregoing 1853 record also includes both the monthly and annual extremes (highest daily minimum, etc.) estimated by Fisk and the monthly extremes actually recorded by fort observers. All 1853 temperature distributions (e.g. days 90 F or higher, 32 F or lower, etc.) are based on Fisk's estimates of daily maxima and minima.
All foregoing monthly mean cloudiness and force of wind values are the simple average of the station's four daily numeric sky cover and wind velocity entries. The foregoing prevailing wind values are based on daily entries indicating the direction of the wind at sunrise/0900/1500 and 2100: prevailing/predominate winds are those most frequently observed/recorded during any given month.
The amount of precipitation officially recorded by fort observers during May, August and November 1853 may significantly understate the amount of moisture which actually fell during these months: records for these three months include descriptive entries (e.g. showers) unaccompanied by any quantitative precipitation value. Precipitation recorded during June 1853 may have totaled 7.59 inches, not 7.89 inches as indicated in the foregoing 1853 climatological summary: 19 June precipitation record is unclear.
In addition to the Ft. Snelling record, the 1853 east central Minnesota climatological record includes an essentially complete record of observations taken at St. Paul's City Drug Store by J. W. Bond during December 1853. This record was published in St. Paul Pioneer and includes descriptions of December 1853 weather events and a record of temperature observations taken at sunrise, 0900, 1200, 1500, sunset and 2100 hours local time.
Sunny, very dry January. Snow cover of two feet reported in St. Paul on 13 January. Anomalous "chinook" event on 23 January: temperatures of 37 F, 44 F and 56 F (accompanied by warm northerly winds) recorded at sunrise, 0900 and 1500, respectively on that date. St. Paul newspapers noted [on 20 and 22 January] that the "weather for some three weeks has been uniformly mild and bright...the atmosphere has been dry, perfectly calm and clear...". Very cold, sunny and very dry February: sunrise readings of -24 F, -22 F, -23 F and -24 F on 3, 4, 5, 8 February, respectively. Readings of -16 F and -15 F at 1500 hours on 3, 8 February, respectively. Only three "slight" snowfall events noted during February. Cold, very dry March. Temperatures of -15 F and -6 F recorded at sunrise and 1500 hours, respectively on 14 March. Reading of -2 F at 1500 on 15 March. Four "slight" snowfall events noted during March. "Slight" rain noted on 31 March. Windy, dry April. Force seven winds on 5, 8, 9 April. Prairie fires noted on 7 April. Cool, windy May: force eight winds on 15 May. Slight snow during the morning of 10 May. Snow and frost on 18 May: temperature of 33 F at sunrise on that date. Sunrise reading of 34 F on 19 May. Force seven winds on 18 May. Wet June with "rising" rivers after mid-month. Severe thunderstorm noted on 22 June. Force eight winds on 11 June, force seven winds on 28 June. Hazy, foggy July. Readings of 66 F and 62 F at 1500 on 8, 17 July, respectively. Much fog during August. Force seven winds on 8, 25, 26 August. Severe thunderstorm on 11 August. Severe thunderstorm during the night of 1-2 September. Very warm early September. No frosts reported during September. Very dry October. St. Paul newspapers [27 October] reported that "prairie fires have been quite common for a week or two past...in the evening, they frequently shed light upon the buildings of our city...". Low river levels noted during month. Cold, windy conditions during late October. Sunrise reading of 8 F on 26 October. Afternoon readings of 30 F, 28 F and 29 F on 23, 24, 25 October, respectively. Prairie fires noted on 1 November. Cold early November: sunrise readings of 8 F and 3 F on 3, 6 November, respectively. Afternoon readings below freezing each day, 2-9 November. Newspapers reported "no snow on the ground" on 24 November. Light snowfall early December: Bond reported that snow cover had melted by 27 December. Heavy snow on 29-30 December: "good sleighing" noted on 31 December. J. W. Bond, St. Paul observer, recorded 50 F at 1500 hours on 10 December: corresponding Ft. Snelling reading of 47 F.