" Peter Clarke" wrote :
"Keith (Southend)" wrote :
A decade or so ago I would have looked at the forthcoming charts showing
high pressure on the near continent with a slack southerly flow and almost
guaranteed widespread fogs. However, so far the forecasts have hardly
mentioned fog(s). Is this to do with the "cleaner" air we now live with,
compared to the soot producing smogs of yester-year. Wew hardly get an
hour or two of fog in a year now, here at Southend-on-Sea, yet I can
remember days with it, and some days it never cleared at all through the
day.

What has changed?

I'm sure the main reason is that, 40 years and more ago, the main source
of heating houses and factories was coal. In the autumn and winter the
first job of the day in most households was to light the coal fire. On
calm, clear mornings the smoke from all these fires soon led to smoke
haze, and if conditions were at all misty, the smoke readily mixed with
it to produce fog.
In my young days, already a weather enthusiast, I used to look forward to
seeing the first fogs of autumn and seeing how long they took to clear.
The earliest date in autumn I noted an all day radiation fog was 30
October 1949, but in most years I expected at least one fog to last all
day before the end of November.

Peter, I remember a couple of days in September 1966 which were
foggy all day in my part of Bedfordshire. Usually, though, it was around
mid-October in Luton. In those days it seemed that the sky only had
to clear for an hour or so late-afternoon, and if the wind was F2 or less,
bang, the fog would clamp down.

Yes, the particulate pollution of domestic fires and industrial emissions
provided a far greater density of condensation nucleii in those days than
exists now.

Philip