Hold a note in your hand (ten pounds or dollars) and rub it. Burn a green/blue candle that you have purified. Imagine swimming in a pool of notes and having everything that money can buy. Then say how much money yo... Read more of WEALTH SPELL at White Magic.ca

Privacy

Home - Storms - Weather Folklore - Barometer Guide

Most Viewed

Localities For Additional Observations
Appendix
Phenomena Of Revolving Storms
Lower Latitudes
Observations
Avoiding The Centres Of Rotating Storms
Phenomena Of Atmospheric Waves
Storms Hurricanes And Typhoons
Seasons For Extra Observations
Times Of Observation

Least Viewed

Times Of Observation
Seasons For Extra Observations
Storms Hurricanes And Typhoons
Phenomena Of Atmospheric Waves
Avoiding The Centres Of Rotating Storms
Observations
Lower Latitudes
Phenomena Of Revolving Storms
Appendix
Localities For Additional Observations

Localities For Additional Observations

In sketching out a system of barometric observation having especial
reference to the acquisition of data from which the _barometric
character_ of certain large areas of the surface of the globe may be
determined--inasmuch as such areas are distinguished from each other, on
the one hand by consisting of extensive spaces of the oceanic surface
unbroken, or scarcely broken, by land; on the other by the proximity of
such oceanic surface to large masses of land, and these masses
presenting two essentially different features, the one consisting of
land particularly characterized as continental, the other as insular,
regard has been accordingly had to such distribution of land and water.

As these instructions have especial reference to observations at sea,
observations on land have not been alluded to; but in order that the
data accumulated may possess that value which is essential for carrying
on the inquiry in reference to atmospheric waves with success, provision
is made to mark out more distinctly the barometric effects of the
junction of large masses of land and water. It is well known that the
oceanic surface, and even the smaller surfaces of inland seas, produce
decided inflexions of the isothermal lines. They exercise an important
influence on temperature. It has also been shown that the neighbourhood
of water has a very considerable influence in increasing the
oscillations of the mercurial column in the barometer, and in the great
systems of European undulations it is well known that these oscillations
increase especially towards the north-west. The converse of this,
however, has not yet been subjected to observation; there has been no
systematic co-operation of observers for the purpose of determining the
barometric affections of large masses of water, such as the central
portion of the basin of the northern Atlantic, the portion of oceanic
surface between the Cape of Good Hope and Cape Horn, the Indian and
Southern oceans, and the vast basin of the Pacific. Nor are we yet
acquainted with the character of the oscillations, whether increasing or
decreasing, as we recede from the central portions of the oceanic
surfaces we have mentioned towards the land which forms their eastern,
western, or northern boundaries. This influence of the junction line of
land and water, so far as it is yet known, has been kept in view in
framing these instructions, and, as it appears so prominently in Europe,
it is hoped the additional observations between the four daily readings
to which probably many observers may habitually restrict themselves,
making on certain occasions and in particular localities a series of
observations at intervals of three hours, will not be considered too
frequent when the great importance of the problem to be solved is fully
apprehended. It need scarcely be said that the value of these
observations at three-hourly intervals will be greatly increased by the
number of observers co-operating in them. Upon such an extensive system
of co-operation a large space on the earth's surface, possessing
peculiarities which distinguish it from others extremely unlike it in
their general character, or assimilate it to such as possess with it
many features in common, is marked out below for particular observation,
occupying more than two-thirds of a zone in the northern hemisphere,
having a breadth of 40°, and including every possible variety of
terrestrial and aqueous surface, from the burning sands of the great
African desert, situated about the centre, to the narrow strip of land
connecting the two Americas on the one side, and the chain of islands
connecting China and Hindostan with Australia on the other. On each side
of the African continent we have spaces of open sea between 30° and 40°
west longitude north of the equator, and between 60° and 80° east
longitude, in or to the south of the equator, admirably suited for
contrasting the barometric affections, as manifested in these spaces of
open water, with those occurring in situations where the influence of
the terrestrial surface comes into more active operation.

The localities where three-hourly readings are chiefly desirable may be
specified under the heads of _Northern Atlantic, Southern Atlantic,
Indian_ and _Southern Oceans,_ and _Pacific Ocean_.

_Northern Atlantic. Homeward-bound Voyages._--The discussion of
observations made in the United Kingdom and the western border of
central Europe, has indicated that off the north-west of Scotland a
centre of great barometric disturbance exists. This centre of
disturbance appears to be considerably removed from the usual tracks of
vessels crossing the Atlantic; nevertheless some light may be thrown on
the barometric phænomena resulting from this disturbance by observations
during homeward-bound voyages, especially after the vessels have passed
the meridian of 50° west longitude. Voyagers to or from Baffin and
Hudson bays would do well during the whole of the voyage to read off the
barometer every three hours, as their tracks would approach nearest the
centre of disturbance in question. Before crossing the 50th meridian,
the undulations arising from the distribution of land and water in the
neighbourhood of these vast inland seas would receive considerable
elucidation from the shorter intervals of observation, and after passing
the 50th meridian the extent of undulation, as compared with that
observed by the more southerly vessels, would be more distinctly marked
by the three-hourly series. Surveying vessels stationed on the
north-western coasts of Ireland and Scotland may contribute most
important information on this head by a regular and, as far as
circumstances will allow, an uninterrupted series either of six-hourly
or three-hourly observations. The intervals of observation on board
vessels stationed at the Western Isles, the Orkneys, and the Shetland
Isles, ought not to be longer than _three_ hours, principally on account
of the great extent of oscillation observed in those localities. Vessels
arriving from all parts of the world as they approach the United Kingdom
should observe at shorter intervals than six hours. As a general
instruction on this head the series of three-hourly observations may be
commenced on board vessels from America and the Pacific by the way of
Cape Horn on their passing the 20th meridian, such three-hourly
observations to be continued until the arrival of the vessels in port.
Ships by the way of the Cape of Good Hope should commence the
three-hourly series either on leaving or passing the colony, in order
that the phænomena of the tropical depression hereafter to be noticed
may be well observed.

_Northern Atlantic. Outward-bound Voyages_.--Vessels sailing to the
United States, Mexico, and the West Indies, should observe at three
hours' interval upon passing the 60th meridian. Observations at this
interval, on board vessels navigating the Gulf of Mexico and the
Caribbean Sea, will be particularly valuable in determining the extent
of oscillation as influenced by the masses of land and water in this
portion of the torrid zone, as compared with the oscillation noticed off
the western coast of Africa, hereafter to be referred to.

_Southern Atlantic. Outward and homeward bound_.--Without doubt the most
interesting phænomenon, and one that lies at the root of the great
atmospheric movements, especially those proceeding northwards in the
northern hemisphere and southwards in the southern, is the equatorial
depression first noticed by Von Humboldt and confirmed by many observers
since. We shall find the general expression of this most important
meteorological fact in the Report of the Committee of Physics and
Meteorology, appointed by the Royal Society in 1840, as follows: "The
barometer, at the level of the sea, does not indicate a mean atmospheric
pressure of equal amount in all parts of the earth; but, on the
contrary, the equatorial pressure is uniformly less in its mean amount
than at and beyond the tropics." Vessels that are outward bound should,
upon passing 40° north latitude, commence the series of three-hourly
observations, with an especial reference to the equatorial depression.
These three-hourly observations should be continued until the latitude
of 40° south has been passed: the whole series will then include the
minimum of the depression and the two maxima or apices forming its
boundaries. (See Daniell's 'Meteorological Essays,' 3rd edition.) In
passages across the equator, should the ships be delayed by calms,
opportunities should be embraced for observing this depression with
greater precision by means of _hourly_ readings; and these readings will
not only be valuable as respects the depression here spoken of, but will
go far to indicate the character of any disturbance that may arise, and
point out, as nearly as such observations will allow, the precise time
when such disturbance produced its effects in the neighbourhood of the
ships. In point of fact they will clearly illustrate the diversion of
the tendency to rise, spoken of in the Report before alluded to, as
resulting in ascending columns and sheets, between which wind flaws,
capricious in their direction and intensity, and often amounting to
sharp squalls, mark out the course of their feeders and the indraft of
cooler air from a distance to supply their void. Hourly observations,
with especial reference to this and the following head of inquiry,
should also be made off the western coast of Africa during the
homeward-bound voyage.

Immediately connected with this part of the outward-bound voyage, hourly
observations, as often as circumstances will permit, while the ships are
sailing from the Madeiras to the equator, will be extremely valuable in
elucidating the origin of the great system of south-westerly atmospheric
waves that traverse Europe, and in furnishing data for comparison with
the amount of oscillation and other barometric phænomena in the Gulf of
Mexico and the Caribbean Sea, a portion of the torrid zone essentially
different in its configuration and in the relations of its area to land
and water, as contra-distinguished to the northern portion of the
African continent; and these hourly observations are the more desirable
as the vessels may approach the land. They may be discontinued on
passing the equator, and the three-hourly series resumed.

There are two points in the southern hemisphere, between 80° west
longitude and 30° east longitude, that claim particular attention in a
barometric point of view, viz., Cape Horn and the Cape of Good Hope; the
latter is within the area marked out for the three-hourly observations,
and too much attention cannot be paid to the indications of the
barometer as vessels are approaching or leaving the Cape. The northern
part of the South Atlantic Ocean has been termed the _true Pacific Ocean
of the world_; and at St. Helena a gale was scarcely ever known; it is
also said to be entirely free from actual storms (Col. Reid's 'Law of
Storms,' 1st edition, p. 415). It may therefore be expected that the
barometer will present in this locality but a small oscillation, and
ships in sailing from St. Helena to the Cape will do well to ascertain,
by means of the three-hourly observations, the increase of oscillation
as they approach the Cape. The same thing will hold good with regard to
Cape Horn: it appears from previous observation that a permanent
barometric depression exists in this locality, most probably in some way
connected with the immense depression noticed by Captain Sir James Clark
Ross, towards the Antarctic Circle. The general character of the
atmosphere off Cape Horn is also extremely different from its character
at St. Helena. It would therefore be well for vessels sailing into the
Pacific by Cape Horn, to continue the three-hourly observations until
the 90th meridian is passed.

Before quitting the Atlantic Ocean it may be well to notice the marine
stations mentioned in my Third Report on Atmospheric Waves,[5] as being
particularly suitable for testing the views advanced in that report and
for tracing a wave of the south-westerly system from the most western
point of Africa to the extreme north of Europe. A series of hourly
observations off the western coast of Africa has already been suggested.
Vessels staying at Cape Verd Islands should not omit to make
observations at three hours' interval _during the whole of their stay_,
and when circumstances will allow, hourly readings. At the Canaries,
Madeiras, and the Azores, similar observations should be made. Vessels
touching at Cape Cantin, Tangier, Gibraltar, Cadiz, Lisbon, Oporto,
Corunna, and Brest, should also make these observations while they are
in the localities of these ports. At the Scilly Isles we have six-hourly
observations, made under the superintendence of the Honourable the
Corporation of the Trinity House. Ships in nearing these islands and
making the observations already pointed out, will greatly assist in
determining the increase of oscillation proceeding westward from the
nodal point of the two great European systems. We have already mentioned
the service surveying vessels employed on the coasts of Ireland and
Scotland may render, and the remaining portion of the area marked out in
the report may be occupied by vessels navigating the North Sea and the
coast of Norway, as far as Hammerfest.

In connexion with these observations, having especial reference to the
European system of south-westerly atmospheric waves, the Mediterranean
presents a surface of considerable interest, both as regards these
particular waves, and the influence its waters exert in modifying the
two great systems of central Europe. The late Professor Daniell has
shown from the Manheim observations, that small undulations, having
their origin on the northern borders of the Mediterranean, have
propagated themselves northward, and in this manner, but in a smaller
degree, the waters of the Mediterranean have contributed to increase the
oscillation as well as the larger surface of the northern Atlantic. In
most of the localities of this great inland sea six-hourly observations
may suffice for this immediate purpose; but in sailing from Lisbon
through the Straits of Gibraltar, in the neighbourhood of Sicily and
Italy, and in the Grecian Archipelago, we should recommend the
three-hourly series, as marking more distinctly the effects resulting
from the proximity of land; this remark has especial reference to the
passage through the Straits of Gibraltar, where, if possible, hourly
observations should be made.

_The Indian and Southern Oceans. Outward and homeward bound._--On
sailing from the Cape of Good Hope to the East Indies, China, or
Australia, observations at intervals of three hours should be made until
the 40th meridian east is passed (homeward-bound vessels should commence
the three-hourly readings on arriving at this meridian). Upon leaving
the 40th meridian the six-hourly observations may be resumed on board
vessels bound for the Indies and China until they arrive at the equator,
when the readings should again be made at intervals of three hours, and
continued until the arrival of the vessels in port. With regard to
vessels bound for Australia and New Zealand, the six-hourly readings may
be continued from the 40th to the 100th meridian, and upon the vessels
passing the latter, the three-hourly readings should be commenced and
continued until the vessels arrive in port. Vessels navigating the
Archipelago between China and New Zealand, should make observations
every three hours, in order that the undulations arising from the
configuration of the terrestrial and oceanic surfaces may be more
distinctly marked and more advantageously compared with the Gulf of
Mexico, the Caribbean Sea, and the northern portion of the African
continent.

_The Pacific Ocean._--As this ocean presents so vast an aqueous surface,
generally speaking observations at intervals of six hours will be amply
sufficient to ascertain its leading barometric phænomena. Vessels,
however, on approaching the continents of North and South America, or
sailing across the equator, should resort to the three-hourly readings,
in order to ascertain more distinctly the effect of the neighbourhood of
land on the oscillations of the barometer, as generally observed, over
so immense a surface of water in the one case, and the phænomena of the
equatorial depression in the other: the same remarks relative to the
latter subject, which we offered under the head of South Atlantic, will
equally apply in the present instance. The configuration of the western
shores of North America renders it difficult to determine the precise
boundary where the three-hourly series should commence; the 90th
meridian is recommended for the boundary as regards South America, and
from this a judgment may be formed as to where the three-hourly
observations should commence in reference to North America.

In the previous sketch of the localities for the more important
observations, it will be seen that within the tropics there are three
which demand the greatest regard.

I. The Archipelago between the two Americas, more particularly comprised
within the 40th and 120th meridians west longitude, and the equator and
the 40th degree of north latitude. As a general principle we should say
that vessels within this area should observe the barometer every three
hours. Its eastern portion includes the lower branches of the storm
paths, and on this account is peculiarly interesting, especially in a
barometric point of view.

II. _The Northern portion of the African Continent, including the Sahara
or Great Desert._--This vast radiating surface must exert considerable
influence on the waters on each side northern Africa. Vessels sailing
within the area comprised between 40° west and 70° east, and the equator
and the 40th parallel, should also make observations at intervals of
three hours.

III. _The great Eastern Archipelago._--This presents a somewhat similar
character to the western; like that, it is the region of terrific
hurricanes, and it becomes a most interesting object to determine its
barometric phænomena; the three-hourly system of observation may
therefore be resorted to within an area comprised between the 70th and
140th meridians, and the equator and the 40th degree of north latitude.

The southern hemisphere also presents three important localities, the
prolongations of the three tropical areas. It is unnecessary to enlarge
upon these, as ample instructions have been already given. We may,
however, remark, with regard to Australia, that three-hourly
observations should be made within the area comprised between the 100th
and 190th meridians east, and the equator and the 50th parallel south,
and hourly ones in the immediate neighbourhood of all its coasts.

Next: Storms Hurricanes And Typhoons
Previous: Times Of Observation

Report
Privacy

SHARE

BOOKMARK

Viewed 489