在Selga Chronology I(参考文献3.2.1, 下简作3.2.1)及论文Northwest Pacific typhoons documented by the Philippine Jesuits, 1566–1900(doi:10.1029/2006JD007370) 中(其中论文利用了3.2.1中的数据整理为表格), 均提到1804年10月1日俄罗斯船只Nadicjada及Neva在西太某气旋中记录到低至680mmHg(~906.4hpa)的气压,具体位置和时间均不明。为了挖掘更多信息,首先关注记载较详细的3.2.1,其记作(重点以红色/加粗标出):
The typhoon, experienced by the russian corvettes Nadicjada and Neva, near Japan, was classed as strong and horrible by the Admiral Krusenstern. The fury of the winds was undescribable. The barometers fell 70 mm. in 4 hours. The barometric minimum was close to 680 mm. The calm lasted a few minutes. The winds shifted from ESE to NE.
此内有船名、大致位置、人名、气压、风眼、风向转变等信息,但远不够详细。在搜索引擎上搜索船名,除了上述两来源实际上得不到任何有用信息。转而搜索人名,则发现其全名为Adam Johann von Krusenstern(俄语名转写: Iván Fyodorovich Kruzenshtérn, 1770-1846), 是俄罗斯第一位实现环球航行的航海家。1803年,其从圣彼得堡附近出发,穿越大西洋,绕过南美洲南端,而后自SE-NW斜穿太平洋,1804年抵达日本附近,其后转向南,经东南亚、印度洋、好望角,沿非洲西海岸返航,1806年完成环球航行。此后,根据航行经历出版了Journey around the World in the Years 1803, 1804, 1805, and 1806 at the Command of his Imperial Majesty Alexander I in the Ships Nadezhda and Neva一书(上下册)。可以立即推断出,详细信息很可能在此书中有记载。此外,显然3.2.1和论文均将前一船名转写错误,因此无法搜索到得以解释。转而搜索书名,很容易搜到电子书资源(因而此处不提供链接),在此书上册英文翻译版(翻译自德语)228-231页或俄文版277-280页即是关于此次经历的描述。摘抄其中部分有用段落如下:
...at daybreak, the weather appearing clearer ... but the heavy swell from SE, and the constant depression of the barometer, seemed, notwithstanding the sun at noon was sufficiently clear for us to take a tolerable observation in 31° 7' N. and 227° 40' W ... About noon ... the waves ran mountain high from SE; the sun was of a dead pale colour, and was soon concealed behind the clouds which flew with rapidity from the same quarter; and the wind, which increased gradually, rose by one o'clock to such a height ... Nothing could equal the violence of the gale. Much as I had heard of the typhons on the Chinese and Japanese coasts, this exceeded all my expectations ... the state of the atmosphere was particularly evinced by the extraordinary depression of the barometer: the quicksilver falling so suddenly that about five o'clock it had not only quite disappeared from the tube, but the great motion of the barometer, for which we had before calculated at least four, and even sometimes five lines, not even bringing it in sight. As our barometer was divided into twenty-seven inches, six lines, if we deduct from this four lines, the height of the quicksilver could only be twenty-seven inches, two lines; and it might be said, without extravagance, that it was only twenty-seven inches and indeed even less, as it was upwards of three hours before it again made its appearance ... the barometer fell to twenty-five inches French, which was therefore three and a half lines lower than with us, if it be admitted that ours had fallen to twenty-seven inches ... Nothing but a change of wind could remove our danger, and fortunately this took place, and it veered from ESE to WSW ... This critical moment preceded a perfect calm, which fortunately lasted only a few minutes ... the storm began to rage with the same fury as before from its new quarter. About ten o'clock it at length appeared to abate a little, and we again, to our great Joy, saw the quicksilver in the barometer ... about midnight it was observed to abate considerably ... This tempestuous weather was followed by an extremely beautiful day ...
(英文版)
可以看到,1804年10月1日船队在中午测量的位置在31°7'N, 132°20'E, 据地图为九州以东近海。此时已经发现非常明显的台风自东南方而来的征兆。中午过后,随着台风前方雨带过境,天气迅速转差,风力迅速加大。到下午五点左右,气压计水银柱已经低于下限,且发生剧烈震荡,风向自ESE转为WSW,此后风眼过境,感受到了数分钟静风。到晚十点以后,风力逐渐减弱,到半夜以后进一步减弱,第二天天气完全转好。(此处略过气压问题,留待后文进一步讨论)
这一段气压描述中出现了一些不常见描述。其中, lines 表示1/12英尺, 而French inch则是法尺, 维基上称1法尺≈1.0657英尺(不适用于此文,后文详述)。
还需要注意,俄文版(扫描翻译为英语; 部分语句不通不影响)此段表述如下:
... at 5 o'clock ... Barometer our imfl separation is not less than 27.5 inches; so the height of the mercury in the barometer was not more than 27 inches and 2 lines, and you can even conclude that it was not more than 27 inches, and can become even less; for it did not reappear until after almost 3 hours.
At noon the barometer showed 29 inches and 3.5 lines; Therefore, at five o'clock the drop of mercury was 2.5 inches ... the fall of mercury into the barometer was up to 25 y Franz. inches, so 3.5 lines lower than ours, we can accept that the mercury in our pressure gauge dropped to 27 inches.
显然英文版缺失了下划线部分内容未翻译(除此外表述基本一致),而这对我们推断气压非常重要。可以发现,作者虽推断气压不高于27inHg, 但其余部分的描述指向另一个值。中午气压为29又7/24inHg(≈29.292in), -2.5in后为26 19/24in≈26.792in; 后文又说25 fr.in.=(29+3.5/12-2.5-3.5/12)in=26.5in, 显然此处换算比为26.5/25=1.06而非1.0657, 否则数据将不吻合。并且,此数据显然就是从27 1/6in(27in 2line)减去4~5line的平均数4.5得到的,也与前文相合。综上,此次在1804.10.1 17时在31°7'N, 132°20'E略偏西南西处测得气压26.792inHg(≈907.3hpa)。3.2.1中的680mmHg=26.771in/906.6hpa则可能是取mmHg单位上的整十值产生的约数。
余论:日本文献记载
查日本气象史料,第一编 暴风雨 中有以下条目(185页; 已转为简体):
文化元年八月二十九日(一八〇四年一〇月二日): 筑前、因幡、伊豫诸国并北海道 大风雨 洪水
福冈县灾异志 廿八日 大风洪水损毛
松山严谈 御领分当八月二十九日 酉刻起 翌晦日辰刻迄 ...(下略)
北海道史 九月朔日 暴风 福山港船舶多有被害
又日本气象史料 追补一 第一编 暴风雨 中有以下条目(29页):
(日期同上): 九州 中国 四国 东海道诸国 大风雨 洪水
其下附有上文同书同段落的日文翻译,大致意思相近,但上文下划线部分却写作水银柱较中午下降"二吋四分之一"(2.25in)而不是2.5in,可能是看错原文或打错字所致。
史料所涉区域有筑前(现福冈县一部)、因幡(现鸟取县东部)、伊豫(即伊予,现爱媛县)、福山(现北海道松前町)等,且松山也属今爱媛县且为首府。此处怀疑八月二十九日误后一天,因酉时当17-19时,与船舶时间记载相当符合,辰时当7-9时,总时长约12-16小时,也符合台风过境时间。结合所有记录来看,该台风应先NW向移动(生成地及时间暂无法判断),环流大致为中等,9.30靠近日本同时逐渐转NNW, 10.1下午移至九州以东近海并逐渐转北,深夜通过丰后水道进入濑户内海,可能擦过或登陆四国西部,而后转NNE,登陆本州西部,10.2-10.3掠过日本海一侧海岸, 约10.4左右再次登陆北海道并转温。查有关资料对比,其可能是二百余年来日本本土四岛近海强度前三位的台风(以气压排位强于枕崎台风,大概率弱于第一室户台风),且很大概率是十月最强。