Micro-meteorology: a discipline all should know about?
In the part of Milan I live, during spring and summer, plant and flower scent is deeper, more concentrated in the morning, to wave away later on, after the Sun really begins shining.
Mushrooms have evolved incredibly complicate structures to shoot their spores nearly 1cm away from their surfaces.
Plume smokes open up wide or stay packed depending on time of day.
These phenomena, and many more, have in common a simple driving phenomenon: air turbulence.
This is due mainly to two factors.
First, the "friction" of wind on any obstacle (rocks, leaves, animals, anything). This is "mechanical convection".
And second, the Sun light (more appropriately, its visible component) heats up soil which in turn heats by contact a very thin, millimeter size sheet of air immediately over it. This air, warmer, expands and loses weight-by-volume, then rising. This is "thermal convection".
Of course, on nighttime only mechanical turbulence is possible. On daytime, we have both.
Turbulence causes mixing. This is more effective as turbulence is larger and the layer of atmosphere already agitated (the "Planetary Boundary Layer") thicker - that is, non to afternoon, approximately. This is why flowers have a more intense scent in the morning: turbulent mixing is much less intense.
Turbulent mixing can not reach soil exactly, however: air, a fluid, is viscous (just a bit - yet enough to stop air mixing in the first centimeter from ground). There a "laminar" layer develops, giving one of the most extreme climate our Planet (and insects, tiny plants and other littles) experience.
The study of these phenomena is named "micro-meteorology". It's both an experimental and theoretical science.
Incidentally, I can say, it has a flavor much more experimental-inductive than deductive-theoretical: instruments able to probe the lower 2km of the atmosphere abound (ultrasonic and hot wire anemometers, SODAR/RASS, and the like). Meantime, the mathematical modeling of the PBL ("Planetary Boundary Layer", mentioned above) is to date mostly confined to semi-empirical relations. Stated in plain English: theer is still all to discover!
Micro-meteorology is extremely useful, as it directly deals with the part of atmosphere we humans live in. Micro-meteorological phenomena affect:
- Pollutant dispersion
- Seed, spore and larvae dissemination
- Forest and ecosystem function
- Global climate (through water vapor, itself mobilized by turbulence after mostly-plant-driven evapotranspiration)
- Much more...
To date, micro-meteorology is not that known.
What I find fascinating in this subject is, it is a "non-subject", spanning many fields. It deals with something operating as a sort of "blood", of connective tissue in the entire bio- and geo-spheres. It "lives" on timescale we humans can easily comprehend, much shorter than our patience spans.
And, what's not maybe so important, has nothing to do with weather forecasts.
Dear sisters, micro-meteorology it's desperately calling for attention. I confide that, contrary to common assumptions about women and science, a bit of formulae will not scare you.
I give to anyone interested some basic references:
R.B. Stull, "An Introduction to Boundary Layer Meteorology", Kluwer Academic Publishers, 1988
T.R. Oke, "Boundary Layer Climates", 2nd ed., Routledge, 1987
On request I may provide more specific references.
Thank for your attention, and cheers