Discussing classification of meteorological and agro meteorological phenomena

1. Tor Håkon SivertsenBioforsk Plant Health and Plant Protection, Hogskoleveien7, N‑1432 Aas (Norway); e-mail:tor.sivertsen@bioforsk.no Discussing classification of meteorological and agro meteorological phenomena

2. The concept of classification We classify meteorological phenomena while giving names to the phenomena we observe: • Air, parcel of air, cloud, time, space,shower, hail, rain, warm front, wind, storm, evaporation, condensation, tropical storm, extra tropical cyclone, boundary layer, soil, surface of soil, crop canopy

6. I make an unusual statement: Any physical and biological phenomenon contains a totality that includes time, space and consciousness

7. We then may use the concept of parameterization in this way: We are connecting measurable/ quantitative entities to the phenomena – and we call these entities parameters

8. Through the centuries the following parameters (and many many others) are developed: Length of time t, the spatial coordinates(x,y,z) , temperature of the air, pressure of the air, relative humidity of the air, density of the air, wind velocity of the air and density of the air. We call such parameters macro properties of the gas-mixture called air, or the parcels of air.

10. We model the nature by using parameters connected to the phenomena. Each of the parameters of the models has a ‘name’, it has a ‘definition’ and it has a ’unit’.

11. To actually use the model we must have input parameters we must have some sort of system for making measurement. Each parameter we derive through the system for making measurement has a ’name’, it has a ‘unit’, it has a ‘definition’. The parameter value derived is connected to the method for making measurements and we want it to be representative for the model parameter considered.

12. Macro physics The macro model of the air we may conceptually describe as a parcel of air (the mass is not clearly defined, merely the relative mass, the density); and connected to this parcel we have the quantitative parameters.

13. We may then extend our model by connecting spatial and temporal coordinates to each parcel of air (by using f.ex. Cartesian coordinates x,y,z and the time coordinate t) These coordinates are in fact parameters connected to each parcel of air. Two different mathematical systems have been developed for studying flow of parcels of fluid: The representation of Joseph Louise Lagrange, looking at tagged parcels of fluid, and the representation of Leonard Euler,looking at the parameter values of the fluid parcels as function of the spatial and temporal coordinates.

14. Micro physics There also are developed models of the molecular physics of the air, looking at the movements of the molecules. This may be considered a quite different world with quite different phenomena: Molecules, space, time We may connect parameters, measurable quantities to the phenomena of the microphysics. And through statistical physics macro properties of the air may be derived. .

15. Micro physics Examples of parameters connected to the microphysics of the air: Molecular mass, velocity of a molecule, momentum of a molecule, angular momentum of a molecule, spatial coordinates (x,y,z), temporal coordinate t. An interesting feature in this is that the temporal and spatial coordinates of the macro-physics and the micro-physics should not be the same. We consider two quite different worlds.

16. Physical ‘laws’ The parameters of the macro state, we connect to certain ‘physical laws’ or preliminary hypotheses containing combination of the parameters: Conservation of mass Conservation of energy ( containing The first law of thermodynamics). Conservation of momentum The second law of thermodynamics giving us the direction of certain processes.

17. Physical ‘laws’ We are able to use the laws of classical thermodynamics (the concept of reversible processes) for the parcels of air. We are able to use Newtons laws of motion for each parcel of air (and we call it convective flow). We then look at the fluid system as two different interrelated processes going on simultaneously on two different scales, the molecular movements of the air and the convective movements of the air

18. Most of the parameters used in meteorology and in meteorological models I think, might be derived from physical concepts of classical thermodynamics, fluid dynamics and the radiation ‘laws’ of short wave and radiation. Also changes of phase of the water of the parcels of air are included in this –water vapor – drops of liquid water – crystals of ice.

19. Examples of meteorological parameters connected to the ‘physical laws’ mentioned: Instant temperature of the air 2m above the ground Hourly mean temperature of the air 2m above the ground Daily mean temperature of the air 2m above the ground Monthly mean temperature of the air 2m above the ground Instant air pressure at the sea surface Instant relative humidity of the air 2m above the ground Hourly mean of the relative humidity of the air 2m above the ground Daily mean of the relative humidity of the air 2m above the ground Monthly mean of the relative humidity of the air 2m above the ground

20. We then move on to the practical systems for making measurements of meteorological parameters: Networks of meteorological stations, weather radar systems, satellites, radio sond systems

21. Agro meteorology Agro meteorological phenomena are combinations of meteorological and biological phenomena. The biological phenomena also may be describes by connecting measurable parameters to the phenomena: Leaf area index of a crop canopy, weight of the biomass etc.