Introduction - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 3

mountains, making observations on the slopes and at mountain summits. But, obvi-
ously, nobody seemed to be interested in such endeavours before the middle of the
seventeenth century. The situation changed with the invention of the barometer by
Evangelista Torricelli (1608-1647). Torricelli recognized that the column of mer-
cury in his barometer was supported by the pressure of the atmosphere acting on the
surface of the mercury in the dish, and in a letter to Michelangelo Ricci in 1644 he
made the dramatic statement that “We live submerged at the bottom of an ocean of
the element air, that by unquestioned experiments is known to have weight” (West
2005 ). If one leaves the bottom of this ocean, the weight of the remaining column
above the observer should decrease. In 1648, Blaise Pascal (1623-1662) persuaded
his brother-in-law, Florin Périer (1605-1672), to ascend the Puy de Dôme in France
and to carry a barometer with him. He detected what was expected: that air pressure
decreased with height; and from then on pressure readings were used to determine
altitude. Fostered by new ideas coming up in the era of enlightenment, moun-
tains became an object of interest for natural researchers in the following 30-40
years. For example, from 1774 on, Horace-Bénédict de Saussure (1740-1799) made
temperature, humidity, and radiation measurements in the Alps. In 1781, the first
mountain observatory on the Hohenpeissenberg, Germany, started its observations
within the network of the Societas Meteorologica Palatina, which are continued
without interruptions until today.
The next remarkable attempt to explore the atmosphere away from the surface
was letting soar kites for scientific purposes (Fig. 1.1 shows an example from
the beginning of the twentieth century). In 1749, the Scottish scientists Alexander
Wilson (1714-1786) and Thomas Melville attached thermometers to kites and mea-
sured and compared temperatures at different altitudes above ground. Three years
later, Benjamin Franklin (1706-1790) performed his famous kite ascents in order to
investigate the electrical field in the air before the onset of thunderstorms.
Then, from 1783 on, climbing up mountains was no longer enough. Human
beings began to travel up into the air with balloons, leaving the solid ground behind.
Scientists immediately discovered this new opportunity for making meteorological
Fig. 1.1 Kite for atmospheric
sounding from the beginning
of the twentieth century at the
Richard-Aßmann
Observatory of the German
Weather Service in
Lindenberg (east of Berlin),
Germany