Föhn spells and the false spring
Why valley temperatures jump fifteen degrees in an afternoon, and how to tell a föhn from an ordinary warm front.
Rhine Valley Field Notes
A private weather and wildlife record kept in the Rhine–Main lowlands since 2016. Readings are taken by hand three times a day; nothing here is automated and nothing is smoothed.
The notes below are the parts of the record that seemed worth writing up. Each states its definitions and its uncertainties, because a ten-year series is only useful if you can tell what was measured and what was estimated.
Notes
Counting fog days in the lowlands
A ten-year count of radiation fog, what disperses it, and why the number keeps falling.
Twenty seasons of swift arrivals
First-sighting dates for common swifts, and what they do and do not tell us about the season ahead.
How these notes are kept
Instruments, definitions, rounding rules and the errors that have been found and corrected.
Using the record
The underlying tables are available on request by post. They are plain text, one file per year, with the column definitions given in the method note. Please cite the year range you use and mention the three unreliable periods listed there.