Transcript The Physics of Leaf Wetness

Reflections on the theme of
classifying, documenting and
exchanging meteorological data, and
some additional comments on agro
meteorological and biological data
sets.
Tor Håkon Sivertsen
The Norwegian Crop Research
Institute
The weather systems on the
planet earth do not respect the
borders put up by the nations.
•
The exchange of meteorological
data sets connected to the man
made systems for making
measurements and models for
predicting the global weather is a
concern of international character.
I will look at a few related
subjects:
• Classifying phenomena connected to weather
and climate.
• Existing systems of exchanging meteorological data
• What challenges of exchanging data will appear in
the future connected to real time exchange of data
between monitoring systems and models.
• The place of agro meteorological and biological
models in this.
• The different systems for making observations.
Classification of meteorological
phenomena and climate
• Classification of clouds (Luke Howard)
• Classification in synoptic meteorology
• Classification of in cloud physics,
tropical meteorology, physical
meteorology etc.
• Classification of climate (Wladimir
Köppen in the years 1918-1936)
The idea of using the modern tool of object
oriented analysis when constructing classes of
meteorological phenomena in numerical models
of weather and climate( COST718)
The basic idea is that in each class or sub class
of a phenomenon quantitative parameters/
attributes is attached to the phenomenon.
Then we have a numerical sub model or a
numerical model.
The existing systems of exchanging
meteorological data sets
in the frame of WMO( World
Meteorological Organisation):
CREX (Character form for the
Representation and EXchange of data)
BUFR (Binary Universal Form for
Representation of meteorological data).
Gridded data sets, called GRIB
(‘GRIdded Binary’).
The CREX/BUFR system
A BUFR-message consist of six sections(of
octets): ‘Indicator section’ ‘Identification
section’ ‘Optional section’ ‘Data description
section’ ‘Data section’ , ‘End section’ .
The metadata of the BUFR-system is contained
in the sections 1,2 and 3. The metadata is
interpreted by several tables information about
the ‘category’ of the data and the types of
quantitative information considered.
GRIB-system
A GRIB-record consists of six sections,
‘Indicator section’, ‘Product Definition Section
(PDS)’ containing metadata on the parameters
considered, ‘Grid Description Section’
containing information on the grid used (type
projection of mapping used) etc., ‘Bit Map
Section(BMS) –optional’ contains information
of parameter fields not defined in certain
subsystems of the gridded model by a bit-mapsystem,‘Binary Data Section (BDS)’ , ‘End
section’ ‘7777’ (human readable indication of
the end of the record)
The metadata of the ‘GRIB’system is mainly contained in
section number ‘1’, and section
number ‘2’ and the interpretation
is given in several tables. The
‘GRIB’-system is tailored for
representation and exchange of
the content of numerical weather
prediction models.
The metadata contained in the ‘BUFR’
and ‘GRIB’-systems is called
meteorological elements. According to
‘International Meteorological
Vocabulary’ a ‘meteorological element’
is defined in the following manner:
’Atmospheric variable which
characterizes the state of the weather at
a specific place at a particular time (e.g.
air temperature, pressure, wind,
humidity, thunderstorm and fog)’.
Attached to ‘BUFR’ and ‘GRIB’ there are
several tables giving the interpretation of
the meteorological elements. This
classification system consists of a mixture
of phenomena and parameters describing
the phenomena, and the system is very
flexible and has great scope.
But my message is: This meta data part
ought to be reconsidered according to the
ideas put up above.
The term ‘parameter’ is often used to
describe a quantitative property of the
atmosphere ( air pressure, air
temperature, wind velocity, global
radiation etc.)
The term ‘parameter’ is not defined in
The meteorological glossary , but the
term ‘parametrization’ is defined in the
following manner:
‘Approximate representation of subgridscale processes in a numerical model in
terms of variables which are explicitly
calculated’.
The use of the term ‘parameterisation’
could be more general. When a
weather phenomenon is described by
attaching quantitative measurable
attributes to it we call it
‘parameterisation’. The
parameterisation of the phenomena
then has to be different on the different
scales.
The work on quality and availability
of data made in COST718 ACTION
• In agro meteorological contexts the
need of exchange of data often is for
modelling purposes.
• Therefore the need for metadata and
documentation is connected to the
modelling (crop growth as well as crop
protection/ warning systems)
A Documentation System for Parameters
(a) Measured
(b) In Models
• Name of the
parameter
• Unit
• Defintion
• Method(s) for
measurement
• Name of the parameter
• Unit
• Defintion
• Representativeness in
model considered
• Representativeness
• Representativeness of
other models
• CREX/BUFR
descriptors
• CREX/BUFR
descriptors
I think this meta data discussion, and
the discussion on exchange of agro
meteorological and biological data
ought to be put in the frame set by the
planning of a new COST action and
the work in the frame of work led by
WMO and connected to weather
hazards, see THORPEX-project, A
global atmospheric research program.
A new COST action of agro meteorology
probably will get the name:’CLIMATE
CHANGE AND IMPACT OF
METEOROLOGICAL HAZARD ON
AGRICULTURE’ .
In this connection I refer to the THORPEXprogram of WMO , see session ‘NP 5.04
Weather hazards reduction(THORPEX)’ at
the EGU-meeting in Vienna in April 2005.
What is probably possible to develop is a
system for exchange of data and
information in almost real time between
the observation systems on the ground
(automated stations, weather radar
systems etc.) and the information from
the satellites and the different numerical
weather prediction systems running.
A question often raised to
meteorologists is the following
question: Is it possible to replace the
old ground based meteorological
stations with the measurements of
the meteorological parameters by
remote sensing equipment like
weather radars and satellites?
The work on ‘homogenisation’ of
long data series of meteorological
data is connected to the observing
systems. In studies on global
change and climate change it is
important to be able to refer to long
homogenous series of
meteorological data.
My conclusion is very short:
When looking at BUFR
and GRIB, what could be considered is
making some sort of parallel work of extending
the biological and agro meteorological models
to use the BUFR and GRIB-protocols, but at
the same time take a look at the metadata
systems of GRIB and BUFR first to see if the
classification systems may be constructed in a
more logical way using methods from object
oriented analysis of the modern IT-world?
Thank you very much!