Four-hourly fluctuations in grass-pollen concentrations in relation to wet versus dry weather, and to short versus long over-land advection

The diurnal variation of Poaceae pollen concentrations in a rural area

“…The diurnal variation of Poaceae pollen has previously been considered by many authors, for example Jones (1952), Liem (1980), Ka È pyla È (1981), Galan et al (1989), Norris-Hill & Emberlin (1991), Spieksma & den Tonkelaar (1986) and Trigo et al (1997). However, most of these studies have been undertaken in urban areas, at sites some distance from the main pollen source areas, and so the diurnal patterns observed will re¯ect not only the timing of pollen release, but also the mechanisms in¯uencing pollen dispersal and transport as outlined by Heise & Heise (1957).…”

Diurnal Variation of Airborne Birch Pollen at Some Sites in Sweden

“…In an attempt to answer such questions we decided to study the diurnal variation of airborne birch pollen at different places in Sweden. It could be expected that the concentration of airborne pollen would be lower during the early morning and then increase to a maximum in the middle of the day or early evening, showing a rather smooth curve, as recently described by authors in other countries (Spieksma 1983, Kapyla 1984, Spieksma & den Tonkelaar 1986, Galin et al 1989. 1991, Jager 1990, Rantio-Lehtimtiki et al 1991.…”

“…Wind speed also effected pollen counts for several species, but not however for Beritln. Spieksma (1983) and Spieksma & den Tonkelaar (1986) in their studies of fluctuations in grass-pollen concentrations often found high nightly concentrations after warm, dry days, which could not be directly correlated with temperature inversions. It was concluded that the daily fluctuations are due to pollen production and release in combination with wind direction and precipitation.…”

Rythmes nycthéméraux de la pollinisation de quelques taxons allergisants

“…Par ailleurs en zone urbaine les phenomenes de convection sont plus importants; cette frequence des courants aeriens a composante ascendante empeche le pollen de se deposer jusqu'a l'heure ou Ia temperature diminue. (Spieksma & den Tonkelaar, 1986), ou rythme monomodal en Angleterre et en Espagne avec une culmination unique a 19 heures dans le premier cas (Corden & Milington, 1991) La determination des cycles diurnes permet de connaitre Ia chronobiologie de chaque plante, c'est-a-dire le moment de Ia journee ou elle emet preferentiellement son pollen ; ceci est interessant a deux niveaux :…”