Helmut Mayer

• Prof. Dr.
• retired head at University of Freiburg

The applicability of the Universal Thermal Climate Index (UTCI) at the urban pedestrian level is ana-lysed in relation to the approach for the vertical wind speed profile (VWSP) used in the UTCI basics. As the UTCI refers to the human-biometeorological reference height (zh-b) of 1.1 m above ground level (agl), all meteorological input variables for...

Seoul has a high density of air quality monitoring stations (AQMSs) grouped into roadside, urban, and background types. Using the extensive data from 42 AQMSs in the period 2018 to 2021, the statistical characteristics of air pollutants required to calculate the daily air quality index DAQx* (daily maximum 1 h O3 and NO2 means and daily 24 h PM10 a...

The variability of daily air quality index DAQx* was analyzed for types of air quality monitoring stations (AQMSs) in Seoul, South Korea, from 2018 to 2021. Daily maximum 1-h means of O3 and NO2 and daily 24-h means of PM10 and PM2.5 from 42 AQMSs were used to calculate the DAQx*. The frequencies of DAQx* values in DAQx* classes 3 (satisfactory) an...

Due to their properties and dimensions, courtyards regulate their microclimate, which, above all, mitigates extreme situations and reduces energy consumption. Mainly for increased energy saving, existing courtyards in temperate climates are often subsequently roofed transparently, converting them into atria. Due to various advantages roofs made of...

For both tree-lined sidewalks of a shallow and deep E-W street canyon located in the city of Freiburg (Southwest Germany), the solar elevation impact on the magnitude of the daytime human heat stress mitigation (hhsm) is analysed in dependence of different tree scenarios. Identic ENVI-met simulations are carried out on the summer solstice day 21 Ju...

Local heat stress, which is caused by the combined effect of changed atmospheric background conditions due to regional climate change and the dynamics in the urban development, is a burden especially for people in urban quarters, which were less confronted with it in the past, such as in Central European cities. Due to its negative impacts on the i...

Concerning Central European conditions the mitigation of daytime heat stress for pedestrians by evenly positioned plane trees on both sidewalks of a shallow and a deep E-W street canyon is quantified by scenario simulations. Using the ENVI-met model v4.0 BETA, they were performed for a previous heat wave day in Freiburg (Southwest Germany). Related...

This study concerns the effects of the air flow initialisation of the ENVI-met model on simulated human heat stress in a fictive E-W street canyon with different aspect ratios that is typical of Central European cities. Human heat stress is described by near-surface air temperature (Ta), mean radiant temperature (Tmrt) and physiologically equivalen...

Based on the ENVI-met model v4.0 BETA, numerical simulations were carried out for five different sized building areas in the city of Stuttgart (Southwest Germany) on the heat wave day 4 August 2003. Human heat stress is primarily quantified by the physiologically equivalent temperature (PET). Additional background information is provided by both ne...

Numerical simulations based on the ENVI-met model were carried out for an E-W street canyon in the city of Stuttgart (Southwest Germany) to analyse the effect of increased albedo of building walls on outdoor human thermal comfort. It was quantified by air temperature (Ta ), mean radiant temperature (Tmrt ) and physiologically equivalent temperature...

The presented method enables a relatively quick evaluation of the human-biometeorological quality of urban areas against the background of summer heat. The method results in index values for the human-biometeorological significance (HBS) and human-biometeorological need for action (HBNA). HBS of an individual urban area indicates its current value...

The RayMan software is worldwide applied in investigations on different issues in human-biometeorology. However, only the simulated mean radiant temperature (T mrt) has been validated so far in a few case studies. They are based on T mrt values, which were experimentally determined in urban environments by use of a globe thermometer or applying the...

The presented method enables a relatively quick evaluation of the human-biometeorological quality of urban areas against the background of summer heat. The method results in index values for the human-biometeorological significance (HBS) and human-biometeorological need for action (HBNA). HBS of an individual urban area indicates its current value...

Freiburg´s city council began to update the city’s master plan and to adjust it for the year 2020. Local climate and air pollution were considered in this scheme through the application of a spatial urban climate analysis of the entire area. For the integral analysis and quantification all available methods and data were included and integrated. Th...

Rapid urbanization, higher density and more compact cities have brought about a new science of urban climatology. An understanding of the mapping of this phenomenon is crucial for urban planners. The book brings together experts in the field of Urban Climatic Mapping to provide the state of the art understanding on how urban climatic knowledge can...

For urban planning in Central Europeans cities, the intensification of severe summer heat, which will be typical of the future summer weather in Central Europe, represents a significant challenge. Long-term planning measures based on current knowledge of urban human-biometeorology are necessary in order to maintain outdoor human thermal comfort on...

This investigation deals with the role of radiant flux densities from different directions in com-plex urban settings for human thermal comfort in summer. The major aim is to analyze the vari-ous impacts of the 3-D short-and long-wave radiant flux densities absorbed by the standardized human-biometeorological reference person on the mean radiant te...

This study concerns the role of short-and long-wave radiant flux densities from different directions in complex urban settings for human thermal comfort on clear-sky summer days. The aims of the investigation are to quantify the importance of the sky view factor as an urban design-dependent variable for the 3-D radiant flux densities absorbed by th...

In the past few decades, severe heat waves were representative of the weather conditions in various parts of the world. They had distinctly negative impacts on humans, plants, animals and different economic sectors. Particularly in cities, where most humans are living, their well‐being, efficiency and health were affected, which even caused a relat...

Regional climate change in Central Europe will lead to an increase of severe summer heat. It causes a new challenge for urban planning in Central European cities, as their design and citizens are not adapted to this meteorological hazard. For the development and application of suitable methods, which enable a local reduction of the heat impacts on...

Although responses of aerial tree parts to wind excitation are of crucial importance for deciduous broadleaved tree stability against wind loading, only a few field studies have been conducted that explore wind–tree part interactions. Therefore, responses of aerial parts of an individual Norway maple tree (Acer platanoides) to wind excitation were...

Meteorological variables affect composition, structure, growth, health, and dynamics of forest ecosystems. The measurement of meteorological data at forest monitoring plots is essential for the interpretation of climate change effects. Within an ecological monitoring network, standard meteorological variables such as precipitation, air temperature,...

Forest meteorology is a very traditional scientific subject. Questions of forest meteorology have been investigated, for example, since 150 years, mostly as “accompanying part” of a systematic forest management. Importance of forest meteorology is due to the fact that about 30 percent of Earth’s surface is covered by forests making this land use to...

Extreme weather events are part of the natural disturbance dynamics of forest ecosystems. In Europe, severe winter storms are currently the main hazard in forest ecosystems, because of their large expansion and their high-impact near-surface flow field characteristics. In recent decades, storms have caused a much higher volume of damaged timber as...

Increasing heat will be a significant problem for Central European cities in the future. Shading devices are discussed as a method to mitigate heat stress on citizens. To analyze the physical processes, which are characteristic of shading in terms of urban human-biometeorology, experimental investigations on the thermal effects of shading by a buil...

The integration of extreme historical floods in contemporary flood protection contributes towards improved risk management and safer handling of floods in the future. As a case study within the “Xfloods” project at the University of Freiburg (Germany), the discharges of the extreme flood in 1824 in the Neckar River basin (Baden-Württemberg/southwes...

This paper presents a case study on the estimation of peak discharges of extreme flood events during the 19th century of the Neckar River located in south-western Germany. It was carried out as part of the BMBF (German Federal Ministry of Education and Research) research project RIMAX (Risk Management of Extreme Flood Events). The discharge estimat...

This paper presents an empirical approach for the decomposition, simulation, and reconstruction of wind-induced stem displacement of plantation-grown Scots pine trees. Results from singular spectrum analysis (SSA) allow a low-dimensional characterization of the complex and complicated tree motion patterns in response to non-destructive wind excitat...

The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers...

Due to its drought sensitivity, the performance and competitiveness of beech as a favoured species of forest management in Central Europe is likely to be negatively affected by the prognosticated climate change, leading to major impacts on the vulnerability of managed forest ecosystems. We studied the genetic differentiation between two populations...

Zusammenfassung Das Meteorologische Institut der Universität Freiburg betreibt im Rahmen des Sonderfor-schungsbereiches (SFB) 433 "Buchendominierte Laubwälder unter dem Einfluss von Klima und Bewirtschaftung" fünf mikrometeorologische Messstationen auf den gemeinsamen SFB-Versuchsflächen bei Möhringen (Schwäbische Alb, Südwestdeutschland). Vier die...

Wind-induced motion of 29 neighbouring trees growing in a Scots pine plantation was measured over the period 14 March to 24 March 2008. The bi-orthogonal decomposition (BOD) of the complex tree motion field into a limited number of spatio-temporal modes provided the basis for the analysis of the response behaviour to wind excitation of the group of...

This study deals with a current problem of urban human-biometeorology on the micro-scale, which becomes more important due to the future increase of severe summer heat in Central Europe. The impact of street design parameters on the thermal comfort of citizens is analysed in an experimental way for typical summer conditions in Central Europe. The i...

Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e. seedlings, mature trees, other woody and herbaceous understorey). Thi...

Economic activities and everyday life may create weekly variations in concentrations of air pollutants in urban settings. The present study contributes to this experience on the example of two typical medium-sized towns in Central Europe, Szeged and Freiburg considering the following air pollutants: NO, NO2, O3, Ox and PM10. Five-year data sets of...

For more than two decades modern data collection systems have been used. The internet and the development of networks have significantly reduced the temporal delay between meteorological measurements and the visualization of measured variables. However, not only the free of charge, current information of the public on the meteorological conditions...

The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers...

Ruß in Baden-Württemberg Statistische Auswertung von Rußmessungen an ausgewählten Luftmessstationen von 1995-2008 L

Photosynthetic photon flux density (PPFD) during the growing season and regeneration growth (height and base stem diameter) were investigated in two natural stands in the Patagonian region of Chile, one without silvicultural management and another with a regenerative felling under a shelterwood system. PPFD was measured by means of fifteen sensors...

Short- and long-wave radiation flux densities absorbed by people have a significant influence on their energy balance. The heat effect of the absorbed radiation flux densities is parameterised by the mean radiant temperature. This paper presents the physical basis of the RayMan model, which simulates the short- and long-wave radiation flux densitie...

Nitrogen (N) cycling in terrestrial ecosystems is complex since it involves the closely interwoven processes of both N uptake by plants and microbial turnover of a variety of N metabolites. Major interactions between plants and microorganisms involve competition for the same N species, provision of plant nutrients by microorganisms and labile carbo...

Luft 69 (2009) Nr. 7/8 -Juli/August 319 Umweltmeteorologie schritten sind, erfolgt unter statistischem Aspekt eine Hei-zung oder Kühlung von Gebäuden und Wohnungen [5]. Um ein Maß für den Wärmeverbrauch in der Heizperiode zu be-kommen, wird der Begriff "Gradtagszahl" eingeführt. Die Gradtagszahl ist nach VDI 2067 [6] das Produkt aus der Zahl der He...

We investigated the water balances of two beech stands (Fagus sylvatica L.) on opposite slopes (NE, SW) of a narrow valley near Tuttlingen in the southern Swabian Jura, a low mountain range in Southwest Germany. Our analysis combines results from continuous measurements of forest meteorological variables significant to the forest water balance, sta...

One significant characteristic of climate change is the increase of the near-surface air temperature T a on a global, regional and local scale. For the city of Freiburg (south-west Germany), the warmest city in Germany, the increase of T a until the end of the 21 st century will be in the range of about 3.5°C. The annual mean T a in Freiburg was 11...

This review article analyzes scientific meteorological literature concerning changes in frequency and intensity of winter storminess over the North-Atlantic European region with respect to climate change signals. Studies about conditions in the past were consid-ered as well as simulations of future storminess. In general we found that (i) analyses...

This article was submitted without an abstract, please refer to the full-text PDF file.

Based on human-biometeorological measurements at two different sites within a street canyon in the city of Freiburg (southwest Germany), the shading influence of the canopy of street trees on human thermal comfort was investigated for a typical Central European summer day within the scope of the joint research project KLIMES. The physiologically eq...

The influence of atmospheric exchange conditions on near-surface PM 10 concentrations is analysed for four cities in the South-West of Germany in the period from 2001 to 2005. For each city, the PM10 data originates from roadside stations and Urban Background (UB) stations, that is, two types of official urban air quality monitoring stations charac...

One significant characteristic of climate change is the increase of the near-surface air temperature Ta on a global, regional and local scale. For the city of Freiburg (south-west Germany), the warmest city in Germany, the increase of Ta until the end of the 21st century will be in the range of about 3.5 ?C. The annual mean Ta in Freiburg was 11.5...

Sealing factor, sky view factor or aspect ratio of street canyons or urban structures can be used to explain influences on phenomena of urban climate. Based on near-surface air temperature (Ta) data and statistical parameters being calculated from measured Ta values, single and multi- ple regression analyses were carried out to determine the influe...

The methodology of the recently developed Daily Air Quality Index (DAQx) and Long-term Air Quality Index (LAQx) is explained. Both indices consider air pollutants frequently monitored at long-term stations within official air pollution control networks. Therefore, they enable an assessment of the integral air pollution, which reflects the ambient a...

The aim of this paper is to examine the evaluation method of thermal comfort in outdoor environments. For this purpose, the thermal comfort of 10 subjects under the outdoor locations in 5 different measurement points was investigated by a questionnaire, along with the measurements of thermal environments. Thermal comfort index SET* and Physiologica...

Within the scope of the joint research project KLIMES, experimental investigations on the level of human thermal comfort are conducted on typical summer days within different urban structures in the city of Freiburg (SW Germany). Human thermal comfort is identified by the physiologically equivalent temperature PET. With respect to the influence of...