Tor Håkon Sivertsen Bioforsk Plant Health and Plant Protection,

Hogskoleveien 7, N‑1432 Aas (Norway); e-mail:tor.sivertsen@bioforsk.no

Quality considerations on meteorological

parameters to be used for modelling UV-radiation

Connection to COST 726

The main objective of COST ACTION 726 ‘Long term changes and climatology of UV radiation over Europe’ is to advance the understanding of UV radiation distribution over Europe as well as understanding the UV changes.

Among the practical objectives is advancement of understanding UV reconstruction models for the calculation of UV climatology.

The engagement of Norwegian Institute for Agricultural and Environmental Research in COST ACTION 726

The practical contribution from the institute is providing data from a network of automated agro meteorological stations, as well as providing know how connected to administration of data and integration of data from different sources.

The network of agro meteorological stations was

established in 1987. 51 of the stations are measuring global radiation, hourly values of this parameter.

Data of interest for modelling UV radiation at the ground

I just mention some known facts. Data of interest are parameter values describing the spatial and temporal distribution of short wave radiation from the sun.

It is also necessary to have information on values of parameters describing the physical and chemical properties of the column of air above the ground.

Relevant data measured at the network of agro meteorological stations

The data from these stations are hourly parameter values. The following parameters are of interest:

Global radiation, amount of precipitation, temperature of the air, albedo, hours with direct

sun radiation and relative humidity of the air.

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’.

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.

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.

 

 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.

 

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

thephenomena of the microphysics. And through statistical

physics macro properties of the air may be derived.

 .

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.

 

Physical ‘laws’

  The parameters of the macro state, we connect to certain ‘physical laws’ or preliminary hypotheses containing combination of the parameters:

Conservation of massConservation of energy ( containing The first

law of thermodynamics).Conservation of momentum

The second law of thermodynamics giving us the direction of certain processes.

 

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

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.

 

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 groundDaily 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 groundHourly mean of the relative humidity of the air 2m above the

groundDaily mean of the relative humidity of the air 2m above the

groundMonthly mean of the relative humidity of the air 2m above the

ground 

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

 

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.