TURBULENT ATMOSPHERIC DIFFUSION:
THE FIRST TWENTY-FIVE YEARS, 1920-1945
1.
When the Scientific Committee invited me to deliver this lecture, their
decision aas. I suppose, motivated by the conviction that nobody could be
better qualified to talk about the past than a iiian of the past! How much the
archaeologists would learn about the Stone Age if they could, at one of their
meetings, listen to a Stone Age Man! But there is a danger: the Stone Age
Man would talk only about his own cavern and thus give a biased account of
the whole story . . . . I am afraid that unfortunately this is what may happen
in my lecture: theoretical and experimental researches on turbulent diffusion
in thc atmosphere are not known to me by library files only; during the
twenty-five years from 1920 to 1945 I did in fact follow them day by day and
sometimes took part in some of them; looking at the field from my own
window, 1 am able to overemphasize some details and to neglect some
others. J apologize for the distortions that my souvenirs could possibly
introduce in some ports of the picture.
2.
Under the title tlifluusion one describes a large class of phenomena, concerning various types of scattering of many kinds of materials in fluids,
gaseous or liquid; diffusion in the atmosphere can be easily observed in
cveryday life; when smoke puffs out of a chimney, particles of unburned
coal, water droplets, and hot gases spread out; when the wind blows in
irregular gusts, it carries puffs of smoke to and fro through a wide wake,
which looks like a grey dark snake over the sky, undulating more or less
rapidly: the concentration of the wake is diminishing continuously as the
puffs propagate further, and finally the wake disappears completely. The fact
I
THE FIRST TWENTY-FIVE YEARS, 1920-1945
1.
When the Scientific Committee invited me to deliver this lecture, their
decision aas. I suppose, motivated by the conviction that nobody could be
better qualified to talk about the past than a iiian of the past! How much the
archaeologists would learn about the Stone Age if they could, at one of their
meetings, listen to a Stone Age Man! But there is a danger: the Stone Age
Man would talk only about his own cavern and thus give a biased account of
the whole story . . . . I am afraid that unfortunately this is what may happen
in my lecture: theoretical and experimental researches on turbulent diffusion
in thc atmosphere are not known to me by library files only; during the
twenty-five years from 1920 to 1945 I did in fact follow them day by day and
sometimes took part in some of them; looking at the field from my own
window, 1 am able to overemphasize some details and to neglect some
others. J apologize for the distortions that my souvenirs could possibly
introduce in some ports of the picture.
2.
Under the title tlifluusion one describes a large class of phenomena, concerning various types of scattering of many kinds of materials in fluids,
gaseous or liquid; diffusion in the atmosphere can be easily observed in
cveryday life; when smoke puffs out of a chimney, particles of unburned
coal, water droplets, and hot gases spread out; when the wind blows in
irregular gusts, it carries puffs of smoke to and fro through a wide wake,
which looks like a grey dark snake over the sky, undulating more or less
rapidly: the concentration of the wake is diminishing continuously as the
puffs propagate further, and finally the wake disappears completely. The fact
I