

METEOROLOGY. 



437 



foi>t. Daily kite flights confirm the theory that 

 temperature changes in the upper air are cyclonic 

 in character, and arc due to the passage of warm 

 and cold waves, which are more strongly felt in the 

 upper air than near the ground. The changes with 

 altitude which precede a warm wave arc these : 

 During the day a decrease of temperature at the 

 adiabatic rates from the ground up to more than 

 1,000 feet, then a sudden rise of temperature, 

 amounting to perhaps 15, followed by a slow fall. 

 .Clouds form when the dew-point of the warm cur- 

 rent, which overflows the cold current, is sufficiently 

 high. Such conditions announce the arrival of a 

 warm wave from eight to twenty-four hours in ad- 

 vance of its appearance at the earth's surface. The 

 conditions that indicate the coming of a cold wave 

 lire a rapid fall of temperature, which exceeds the 

 adiabatic rate up to about 1,000 feet, and above 

 that is at the adiabatic rate to 3,000 feet higher. 

 During the prevalence of the cold wave the temper- 

 ature at the height of a mile, which is sometimes 

 its upper limit, may be 25 or 30 lofrer than at the 

 ground. After the cold wave has passed, and with 

 the coming of a southeast storm, the temperature 

 rises rapidly up to a height of 1,000 or 2,000 feet, 

 and then slowly falls. Cloud usually occurs when 

 the temperature begins to fall, and sometimes this 

 cloud extends downward to the earth as a fog. The 

 relative humidity generally increases to saturation 

 in the clouds and above them rapidly decreases. 

 In clear weather there may be change of relative 

 humidity with altitude, as during the cold wave; or, 

 with no change of temperature vertically, both the 

 absolute and relative humidity may decrease rapidly 

 with increase of altitude, as is the case in areas of 

 high barometric pressure. At the height of half a 

 mile the diurnal changes of relative humidity are 

 the 1 inverse of those at the ground. In brief, then, 

 during fair weather in the upper air the days are 

 relatively cold and damp, while the nights are warm 

 and dry, as compared with surface conditions. 

 Electricity is usually noticed on the kite wire when- 

 ever the altitude of the kite exceeds 1,700 feet. At 

 higher altitudes, as well as during snowstorms and 

 near thunderstorms, the potential increases, and is 

 sufficient to cause strong sparking discharges. It 

 therefore appears to be only necessary to tap the 

 great atmospheric reservoir to obtain an inexhaust- 

 ible supply of electricity, which, perhaps, may be 

 applied to the service of man. Kites are frequently 

 employed on Blue Hill to measure the heights of 

 certain low and uniform clouds which could not be 

 measured by either photographic or visual theodo- 

 lites. From the traces of the barometer and hy- 

 grometer the thickness of clouds mav be deter- 

 mined. 



In addition to a formerly published investigation 

 by Dr. 0. Pcttersson, based on observations made 

 during about twenty years on the Norwegian coast, 

 going to show that certain relations exist between 

 the behavior of the Gulf Stream and the subsequent 

 general character of the weather over Europe, con- 

 firmatory results, based on a longer series of obser- 

 vations, are published by Dr. W". Meinhardus, of 

 Berlin, in the " Meteorologische Zeitschrift." His 

 article, " On the Meteorological Relations between 

 the North Atlantic Ocean and Europe during the 

 Winter Half Year," shows that a good prediction of 

 the temperature over a large area may be made 

 with a considerable probability of success, and that, 

 generally speaking, a high (or low) temperature of 

 the Gulf Stream on the Norwegian coast in the first 

 pfirt of the winter (November to January) is usu- 

 ally followed by a high (or low) air temperature in 

 central Europe in the latter part of the winter 

 (February to March) and the early spring (March 

 uiul April). 



The subject of mild winters has been discussed 

 by Dr. G. Hellmann, upon the basis of temperature 

 observations in Berlin since the early part of the 

 last century. The author considers the frequency 

 and succession of mild winters; their general char- 

 acter; and the kind of summer weather that may be 

 expected after a mild winter defining as a mild 

 winter, for the purpose of the investigation, one in 

 which the mean temperature of December and Janu- 

 ary is above the average, and in which the sum of 

 the deviations of both amounts to at least 2 C. A 

 table giving the number of deviations from Novem- 

 ber to August shows that since 1720 there have 

 been 48 mild winters in Berlin, and that they have 

 never been isolated, but occur in groups of two or 

 three years, and especially after a longer period of 

 colder winters. The intervals between two groups 

 of mild winters vary from nine to fourteen years. 

 The table shows that these mild winters are usually 

 of long duration, and that the chances are nineteen 

 to twenty-one that after a mild winter February 

 will also have a high mean temperature. The 

 greatest deviations of temperature usually occur in 

 January. Whether a mild winter will be damp or 

 dry depends chiefly upon the distribution of atmos- 

 pheric pressure. Taking July and August as repre- 

 senting the summer, the author has further found 

 that the chances are 44 per cent, that a warm sum- 

 mer will follow a moderately mild winter, while 

 after a very mild winter the chances of a warm 

 summer amounts to 68 per cent. Cases of mild dry 

 winters are rare; and if the deficient rainfall is 

 not compensated for during springtime, the sum- 

 mer is likely to be wet and consequently cool. 



A chart of yearly isotherms and isabnormals of 

 the sea surface, prepared by Dr. Koppen, shows, in 

 addition to the isotherms, those districts where a 

 temperature anomaly of more than 2 C. exists. 

 The areas where the water is too cold or is too hot, 

 or which are thermically neutral, are distinguished 

 by different shadings. It is seen on this map that 

 between the equator and latitude 40 S. cold 1 cur- 

 rents extend like long tongues from the west coasts 

 of South Africa and South America toward the west, 

 while north of the equator analogous currents are 

 developed to a much less extent. On the coast of 

 the Sahara the sea temperature is only slightly be- 

 low the normal value of the latitude. On the west- 

 ern sides of the oceans, in similar latitudes, warm 

 current^ exist trending northward. In the South 

 Atlantic the warm and cold currents are nearly 

 equalized. In the South Pacific the cold current 

 and in the South Indian Ocean the warm current 

 predominates, as it does also in the northern hemi- 

 sphere, and more particularly in the North Atlantic. 

 It is also seen that an area of cold water occurs on 

 the western edge of the warm currents, and between 

 them and the continents, where the latter stretch 

 northward as far as the zone of westerly winds, viz., 

 on the east coasts of Asia and North and South 

 America. 



Among the noteworthy facts brought out in a 

 paper by Dr. Alexander 'Buchan on the mean at- 

 mospheric pressure and temperature of the British 

 Islands for forty years, 1856 to 1895, is the down- 

 curving of the annual isobaric lines as they cross 

 the Irish Sea and St. George's Channel. Another 

 distinct feature of the isobars is the influence of 

 the land in increasing the barometric pressures and 

 the opposite influence of the sea in depressing the 

 isobars. The author finds that where a winter cli- 

 mate is sought as for invalids, offering in the high- 

 est degree the combined qualities of mildness and 

 dryness, anywhere offered by the British Islands 

 such a climate is to be found on the shores of the 

 Channel, from about Dover to Portland. 



From his investigation of the ''cold days" of 



