This working group consists of an informal collaboration of members of the
meteorological community within the larger Alpine area (usually one partner per country).
The communication up to now takes place via the Internet or Fax, nevertheless joint
meetings are planned at a later stage. There are members of National Meteorological
Services as well as from Universities and research institutions volunteering to create an
international data set on meteorological observation networks in our area, which is
surprisingly not available up to now except for GTS-type data (WMO-files). The main goal
of the WG-Obs is to support the MAP community with information about meteorological
observation platforms with special emphasis to non-GTS data (governmental and
non-governmental). This information should then enable the MAP data center to collect data
from the different sources. The work concentrates on the MAP high-resolution data domain
defined as 2E-19E, 42N-50N including the islands of Corsica and Sardinia.
In a first step an inventory of meteorological observing systems in the MAP area is
being established. The working group started with surface and radiosonde stations. In a
second step, information about other observing systems will be collected, i. e. about
RADAR networks in cooperation with the MAP-WG on RADAR.
The information came from the NWS in digital files. A considerable part of it had to be
keyed in e.g. from station lists. A valuable information source was the precipitation
station list from Christoph Frei (ETH, Zurich). Figure 1 shows an approximate distribution
of the operators of the stations. This graph is somewhat preliminary since it was not
always clear to which category a particular institution belongs.
The following table lists the number of surface stations per parameter and elevation
class:
Figure 1: Approximate distribution of the ope-rators of the stations (preliminary). Although information of an impressive number of surface stations has been gathered, work is neither complete nor correct in each detail. For those countries, where different institutions operate weather stations (especially for Italy), a time-consuming and not yet fully acomplished task is to remove duplicates. The maps on the following pages show the locations for which detailed information was available by the end of 1996.
| Elevation [masl] | Temperature | Pressure | Humidity | Precipitation | Ground Temp. | Wind | Global Radiation | Sunshine duration | Snow depth |
| 0 to 500 | 1219 | 1103 | 458 | 3428 | 487 | 942 | 940 | 345 | 624 |
| 500 to 1000 | 474 | 412 | 145 | 1884 | 194 | 397 | 397 | 79 | 255 |
| 1000 to 1500 | 183 | 114 | 60 | 558 | 16 | 86 | 86 | 40 | 62 |
| 1500 to 2000 | 104 | 65 | 39 | 171 | 9 | 57 | 57 | 31 | 38 |
| 2000 to 2500 | 47 | 21 | 13 | 55 | 3 | 33 | 29 | 9 | 17 |
| 2500 to 4000 | 26 | 15 | 13 | 17 | 2 | 23 | 23 | 9 | 16 |
Table 1: Stations available per parameter and elevation class (collection state end of
1996).
Once meteorological data have been collected and stored in a database (certainly more
than 10000 stations are being expected to operate within the MAP high resolution data
domain), the quality of these data becomes a key issue. The users will be faced not only
with single outliers but also with biases originating from different processing algorithms
in different countries. There are open questions as:
The WG-Obs will try to contribute answers to these questions by:
The following maps give a preliminary overview over the location of the stations as
known by the end of 1996. Duplicates are removed only for some countries. Erroneous
coordinates are not corrected and the measuring programs are not completed for some
countries (e.g. for Austria the category 1-3 obs/day means at least 1 obs per day). From
other countries (e.g. Switzerland, Slovakia, Italy and others) we expect still more
information. In particular, additional lists of precipitation stations in Italy and
Croatia are currently in the process of being included into the database (they are partly
included in Figure 6). The shaded area denotes mean terrain elevations above 1500 masl.
Figure 2: Temperature measurements in the MAP high resolution data domain
Figure 3: Humidity measurements in the MAP high resolution data domain
Figure 4: Pressure measurements in the MAP high resolution data domain
Figure 5: Wind measurements in the MAP high resolution data domain
Figure 6: Precipitation measurements in the MAP high resolution data domain
Figure 7: Upper air stations in the MAP high resolution data domain
Phenomena which are centered at tropopause level, e.g. tropopause folds and potential
vorticity (PV) streamers, are called îupper level features” (ULF). It is a
supporting objective of MAP to study such features, since they are thought to be important
(see MAP Design Proposal). During the MAP meeting in Hall 1996 the idea has been launched
to form a MAP working group on upper level features (WG-ULF). This group has two aims:
Firstly, to initiate the contact between scientists interested in ULFs and to enhance the
exchange between them; secondly to formulate topics of interest, to define needs for
observational data and to design proposals for possible experimental work. This text is
based on a questionnaire sent out in May to all present members of WG-ULF as listed in the
last section.
The participants in WG-ULF plan to study:
Martin Leutbecher pointed out that raw data or processed data from radiosondes are
necessary in order to determine the location (latitude, longitude and height) of the sonde
as a function of time. The vertical resolution should be as high as possible, it should
correspond to a spacing of 200 m or less. Data should be stored up to the maximum altitude
the sonde reached.
Olaf Morgenstern emphasized that measurements of data, such as horizontal and vertical
wind, moisture contents, and in certain situations ozone and nitrogen oxides, might be
very helpful in order to verify and tune the HM model.
At present there are neither flight plans nor experiment designs for topics related to
WG-ULF within the MAP experiment. Therefore WG-ULF should state the requirements for this
type of experiment by designing and formulating an experimental plan. In the following
activities are listed, which might help to support experimental efforts in measuring upper
level features:
It is planned to hold a separate WG-ULF getting together during the next year MAP meeting in Italy. Those who are interested in participating in WG-ULF or want to get more information should
contact:
Klaus P. Hoinka,
Tel. +49-8153-282585;
email: klaus.hoinka@dlr.de.
Following colleagues have announced their interest in participating in WG-ULF:
At the beginning of 1996, a new MAP Forecasters working group (to be known as
Forecasters Forum) was formed to establish a cooperation among a group of forecasters
which should enhance, during the ongoing Phase I of the Project, their expertise on
meteorological phenomena relevant for MAP. The Forecasters Forum participants, currently
about 20 forecasters from 7 alpine Countries, will also take part in the Operational
Activity at MOC during the field phase in 1999, when the role of a smoothly geared
forecasting team will be crucial to provide adequate support and real time advising to the
decision making process during interesting meteorological events.
During the present phase 1 of MAP, the activity of the Forecasters Forum can give a
valuable support to the project by contributing to a better focusing of those scientific
and operational problems related to MAP objectives and through its link with other MAP
working groups and research activities. As often mentioned, MAP is in fact an important
opportunity to strengthen the interactions between operational forecasters and the
atmospheric scientific community. In principle, any new development in both meteorological
observing systems and diagnostic and prognostic methods should reflect into improvements
in forecasting capabilities. How effective this improvements are can only be evaluated
with certainty by bench forecasters.
In this logic, the first important action of the Forecasters Forum has been the
distribution of a questionnaire, prepared by Reinhold Steinacker and Andrea Buzzi, with
the purpose to ask the forecastersí viewpoint on experiences and difficulties in
forecasting weather phenomena related to MAP specific objectives. To make the analysis
more effective, the questionnaire has been divided in two parts, referred specifically to
WET and DRY MAP objectives.
The first workshop of the working group took place in Innsbruck on 22 May 1996. During
this workshop, the answers to the questionnaire have been presented and commented by
Andrea Buzzi and Reinhold Steinacker. Subsequently, some meteorological situations
relevant for MAP have been presented and discussed (Willemse and Muller, MAP newsletter no
5, October 1996). Since this workshop was the first opportunity for a plenary discussion
about the newborne cooperation, the last part of the meeting was devoted to a preliminary
definition of the forecasters cooperation procedure. Another important point evidenced
during this workshop was the strong interest of the participants to initiate a mutual
exchange of know-how and of operational forecasting methodologies referred to MAP-related
meteorological phenomena.
As a starting point, it was decided to initiate a joint activity for monitoring and
documenting those relevant meteorological situations occurring during the extended MAP
season from 15 June to 15 November of the years preceeding the 1999 field phase (i.e.
1996, 1997 and 1998). This forecasting/monitoring activity is carried on under the
coordination of four leading centres which were chosen both on a geographical basis and
also considering the precise nature of the meteorological phenomena in question. Such
leading centres, together with the meteorological phenomena for which they are reference
point, are listed below:
The leading centres have the responsibility, after consultations with the other
centres, to define an ALERT condition, specifying the time period and the geographical
domain over which the participating Services should collect all available data, including
non-GTS data, radar images, satellite data etc. The leading centre can also suggest
special actions to be taken as, for examples, to carry out additional soundings.
This pre-field phase activity will produce a catalogue of documented meteorological
situations useful for internal (to the working group) discussions and also for other
scientific activities (the most relevant cases could be included in the list of case
studies of the Numerical Modelling Working Group). Another important task will be to try
to quantify the forecasting skill of the MAP Forecasters Forum, taking in particular
account of the frequency of false alarms, especially regarding intense precipitation
events. Some false alarms could be considered as cases to be studied, similarly with
events that occurred but were not predicted.
At this stage, most of the activity will be devoted to improving some aspects of the
cooperation during the next MAP season. During the second workshop, which will be held in
Innsbruck on 27-28 February 1997. After a presentation of the interesting cases that
occurred in 1996, the cooperation will be discussed. In particular, all those aspects
related to the definition and management of alert conditions will be examined, together
with data archiving and transmission procedures.
The first year of activity, related to the 1996 extended MAP season, is now over, and
the first important consideration to be made is on the strong and enthusiastic
participation of the members of this working group in these activities. Apart from the
collective chairmanship (Reinhold Steinacker, Andrea Buzzi, Peter Binder and Tiziana
Paccagnella), most of the participants gave, and continue to give, a substantial
contribution to the planning and organisation of the activities. It is to be hoped that
the continuously improving cooperation procedures and reciprocal knowledge will allow,
îif the weather is on our side”, a successfull 1997 MAP season.
In this contribution we try to assemble relevant research topics in connection with possible studies on the Alpine boundary layer within the framework of MAP. It reflects the result of collecting contributions from the various members of the boundary layer working group within MAP and may, therefore, appear somewhat heterogeneous. However, we have tried to group each of the sub-topics into a section on 'open questions' and one containing 'existing concepts and studies' including selected references.
As a prerequisite to appreciate this 'collection of problems and research questions' it
might be worthwhile to briefly establish the state-of-the-art of boundary layer research:
for many decades the research focus was on understanding and describing the flow and
turbulence characteristics over idealized surfaces being horizontally homogeneous and flat
(with the additional assumption that the flow is stationary). For such situations the
theoretical understanding of boundary layer processes seems to be more or less settled and
can be found in a number of text books (e.g., Panofsky and Dutton, 1984; Stull, 1988). It
is important to notice that boundary layer parametrizations in virtually all existing
dynamical models are based on theory that evolved from this type of idealized setting, no
matter where they are to be applied.
In recent years (starting in the late 70's) extensions to this basic theory were seeked
for, which were again concerned with idealized settings of inhomogeneity:
Many of these recent developments can be found in Garratt (1992) or Kaimal and Finnigan (1994). The fundamental problem in the context of MAP is the fact that all three of the above mentioned types of small scale inhomogeneity will simultaneously occur with yet unknown relative importance over the given Alpine surface distribution. In addition, the large-scale topography will lead to non-equilibrium conditions in terms of, e.g., the mean horizontal pressure distribution.
Some material on orographically influenced boundary layers can also be found in reviews
on mountain meteorology as e.g. Smith (1979) although his main topic is lee waves. A
monograph on boundary layers over complex terrain has been compiled by Blumen (1990). A
short chapter on heterogeneous boundary layers has also be written by Nieuwstadt (1995).
The local distribution of these fluxes over the Alps, and spatial and time averages of
these fluxes will be essential for the study of severe (moist) convection and possible
subsequent flooding in the Alpine region.
Concepts that can be used for 'ideally inhomogeneous' surfaces are summarized below.
However, it will have to be carefully checked whether these concepts can be transferred to
real mountainous terrain:
Two basic approaches to these questions are possible. The dynamic approach addresses
the problem of generalization from the physics of the single phenomena in question. The
climatological approach on the other hand starts from frequently observed features and
then seeks for an explanation for these features.
Radiosonde data of most of the stations around and in the Alps are available for at
least the last 20 years. These data could be analyzed. Some of the data are in high
vertical resolution (for example in Payerne, data are taken every 6 - 8 seconds, which
gives a vertical resolution of about 30 m). From the viewpoint of climatology the
following problems should be addressed:
Hydrology has become an additional point of interest in MAP. The interrelation between
meteorological and hydrological phenomena in orographically heterogeneous terrain is
important.
Details on the concepts have still to be discussed with the hydrology working group.
On the interaction between local thermotopographic circulations and the turbulent
boundary layer, some answers to the questions raised above can be found in Blumen (1990),
Whiteman and Doran (1993), Kuwagata and Kimura (1995), and Whiteman et al. (1995) and some
further key references listed in these papers. It can be anticipated that local winds can
have important effects on the (local) turbulence structure, including autocorrelations and
higher order statistical moments (skewness, kurtosis). The skewness might be different
from zero (similar to a CBL over flat terrain), and the kurtosis is perhaps higher than in
shear-produced turbulence. This deserves careful measurements and modelling efforts.
Flux-gradient relationships seem to be inappropriate for these problems.
Recent experimental (aircraft) data which show different exchange intensities between
boundary layer and troposphere over two different types of terrain are presented in
Lehning et al. (1997). The determination of the height of the boundary TRACT data have
been used by de Wekker (1995) to derive the behaviour of the boundary layer height over
the Rhine valley and the Black Forest.
Here, there is a variety of possible questions and problems. In general, once the
turbulence and flow structure is 'known', the problem can be tackled using appropriate
models (e.g., using a particle dispersion model in connection with a flow model). For
details concerning such models, see, e.g., Lehning et al. (1996), Rotach et al. (1996), or
Ferrero et al. (1996).
Existing work mainly includes measurement campaigns (with or without associated
modelling efforts) of the following types:
This compilation has emerged from a variety of comments and suggestions from the
members of the MAP Working Group on Boundary Layer Meteorology (WG-PBL). We thank all of
them for their contributions. Present members are: Domenico Anfossi, Sandrine Anquetin,
Stefania Argentini, Joel van Baelen, Robert Banta, Katrin Baumann, William Blumen, Claudio
Cassardo, Manfred Dorninger, Stefan Emeis, Markus Furger, Christian Haeberli, Michael
Hantel, Sabine v. Huenerbein, Pierre Jeannet, Pirmin Kaufmann, Matthias Langer, Michael
Lehning, Matthias Lugauer, Bruno Neininger, Greg Poulos, Hans Richner, Mathias Rotach,
Petra Seibert, Francesco Tampieri, Siegfried Vogt, Stephan de Wekker, and David Whiteman.
Ambrosetti, P., D. Anfossi, S. Cieslik, G. Graziani, R. Lambrecht, A. Marzorati, K. Nodop, S. Sandroni, A. Stingele, and H. Zimmermann, 1996: 'Mesoscale transport of atmospheric trace gases across the central Alps: the TRANSALP tracer release experiments', Atmosph. Environ., in press.
Beljaars, A.C.M.; Walmsley, J.L. and Taylor, P.A., 1987: 'A Mixed Spectral Finite Difference Model for Neutrally Stratified Boundary Layer Flow over Roughness Changes and Topography', Bound.-Layer Meteorol., 38, 273-303.
Blumen W. (ed), 1990: 'Atmospheric Processes over Complex Terrain', AMS, 323pp.
Carruthers, D. J. and Hunt, J.C.R.: 1990, 'Fluid Dynamics of Airflow over Hills: Turbulence, Fluxes and Waves in the Boundary Layer', in: Blumen, W. (Ed.), Atmospheric Processes over Complex Terrain, Amer. Meteorol. Soc., 83-108.
de Wekker, S.F.J., 1995: 'The Behaviour of the Convective Boundary Layer Height over Orographically Complex Terrain', Diploma thesis Universitaet Karlsruhe/Wageningen Agricultural University. 74pp.
Emeis, S., 1987: 'Pressure Drag and Effective Roughness Length with Neutral Stratification', Bound.-Layer Meteorol., 39, 379-401.
Emeis, S., 1994: 'Bestimmung und Parametrisierung des Druckwiderstands an Hindernissen in der atmosphaerischen Grenzschicht', Ber. Dtsch. Wetterd., 191, 189 pp.
Emeis, S.; H.P. Frank and F. Fiedler, 1995: 'Modification of Air Flow over an Escarpment - Results from the Hjardemaal Experiment', Bound.-Layer Meteorol., 74, 131-161.
Ferrero, E., F. Desiato, G. Brusasca, D. Anfossi, G. Tinarelli, M.G. Morselli, S. Finardi, and D. Sacchetti, 1996: 'Intercomparison of 3D flow and particle models with TRANSALP 1989 meteorological and tracer data', In: Air Pollution Modelling and its Applications XI, in press.
Finnigan, J.J. and Brunet, Y., 1995: 'Turbulent Air Flow in Forests on Flat and Hilly Terrain', in: Coutts, M.P. and Grace, J. (Eds.), Wind and Trees, Cambridge University Press. Garratt, J.R., 1992: The Atmospheric Boundary Layer, Cambridge University Press, 316 pp.
Graber, W. K., S. Andreani-Aksoyoglu, J. E. Keller and C. M. Rosselet, 1995: 'Multi-Parcel Lagrangian Model for Quantification of Influence of Alpine Air Mass Exchange on Photo-Oxidant Production', Atm. Environ., 29, 2961-2976.
Horst, T.W. and Weil, J.C.: 1992, 'Footprint estimation for scalar flux measurements in the atmospheric surface layer', Bound.-Layer Meteorol., 59, 279-296.
Hunt , J.C.R., 1980: Wind over hills. In: Wyngaard, J.C. (Ed.), Workshop on the Planetary Boundary Layer, 14-18 August 1978, Boulder Co. Amer. Meteorol. Soc. Boston, 107-146.
Kaimal, J.C. and Finnigan, J.J., 1994: Atmospheric Boundary Layer Flows, Oxford University Press, 289 pp.
Kuwagata T. and Kimura F., 1995: 'Daytime Boundary Layer Evolution in a Deep Valley. Part I: Observations in the Ina Valley', J. Appl. Meteorol., 34, 1082-1091.
Lehning M., Richner H., Kok, G.L., 1996: 'Pollutant Transport over Complex Terrain: Flux and Budget Calculations for the POLLUMET Field Campaign', Atmos. Environ., 30, 3027-3044.
Lehning, M., H. Richner, G.L. Kok and B. Neininger, 1997: 'Fluxes and Budgets of Air Pollutants over Densely Populated Areas', Submitted to Atmos. Environ.
Marzorati, A. and D. Anfossi, 1993: Doppler SODAR measurements and evaluations in complex terrain. Il Nuovo Cimento, 16, 141-154.
Moran, M.D. and Pielke, R. A., 1996a, 'Evaluation of a Mesoscale Atmospheric Dispersion Modeling System with Observations from the Great Plains Mesoscale Tracer Field Experiment. Part I: Datasets and Meteorological Simulations', J. Appl. Meteorol., 35, 281-307.
Moran, M.D. and Pielke, R. A., 1996b, 'Evaluation of a Mesoscale Atmospheric Dispersion Modeling System with Observations from the Great Plains Mesoscale Tracer Field Experiment. Part I: Dispersion Simulations', J. Appl. Meteorol., 35, 308-329.
Nieuwstadt, F.T.M., 1995: Atmospheric boundary layer processes and influence of inhomogeneous terrain. In: Gyr, A. and F.-S. Rys (Eds.), Diffusion and transport of pollutants in atmospheric mesoscale flow fields. Kluwer, Dordrecht. 89-127.
Panofsky, H.A. and Dutton, J.A., 1984: Atmsopheric Turbulence, John Wiley and Sons, 397 pp.
Raupach, M.R, Antonia, R.A. and Rajagopalan, S: 1991: 'Rough-wall turbulent boundary layers', Appl. Mech. Rev., 44, 1-25.
Rotach, M. W., 1993a: 'Turbulence close to a rough urban surface, Part I: Reynolds stress', Bound.-Layer Meteorol., 65, 1-28.
Rotach, M. W., 1993b: 'Turbulence close to a rough urban surface, Part II: Variances and gradients', Bound.-Layer Meteorol., 66, 75-92.
Rotach, M. W., S. E. Gryning and C. Tassone, 1996: 'A two-dimensional stochastic Lagrangian dispersion model for daytime conditions', Quart. J. Roy. Meteorol. Soc., 122, 367-389.
Schmid, H.P, 1994: 'Source areas for scalars and scalar fluxes', Bound.-Layer
Meteorol., 67, 293-318.
Schmid, H.P. and Buenzli, D., 1995: 'The influence of surface texture on the effective roughness length', Quart. J. Roy. Meteorol. Soc., 121, 1-22.
Schumann, U., 1990, 'Large-Eddy Simulation of the up-slope boundary layer', Quart. J. Roy. Meteorol. Soc., 116, 637-670.
Senff, C., J. Bösenberg, G. Peters and T. Schaberl, 1996: Remote sensing of turbulent ozone fluxes and the ozone budget in the convective boundary layer with DIAL and RADAR-RASS: A case study. Beitr. Phys. Atmosph., 69, 161-176.
Smith, R.B., 1979: The influence of mountains on the atmosphere. Adv. in Geophys., 21, 87-230.
Stull, R.B., 1988: An Introduction to Boundary Layer Meteorology, Kluver Academic Publishers, 666 pp.
Taylor, P.A. and P.R. Gent, 1980: Modification of the boundary layer by orography. GARP Publ. Ser. No. 23, WMO, Geneva, 143-165.
Wanner, H., T. Kuenzle, U. Neu, B. Ihly, G. Baumbach and B. Steisslinger, 1993: 'On the Dynamics of Photochemical Smog over the Swiss Middleland - Results of the First POLLUMET Field Experiment', Meteorol. Atmos. Phys., 51, 117-138.
Whiteman D.C. and Doran C.J., 1993: 'The Relationship between Overlying Synoptic-Scale Flows and Winds within a Valley', J. Appl. Meteorol., 32, 1669-1682.
Whiteman D.C., McKee, T.B., Doran C.J., 199(5): 'Atmospheric Mass, Heat, and Moisture Budgets in a Canyonland Basin', in preparation.
Xu , D. and Taylor, P.A.: 1995, 'Boundary-Layer Parameterizations of drag over
small-scale topography', Quart. J. Roy. Meteorol. Soc., 121, 433-444.
