Toward optimized temperature sum parameterizations for forecasting the start of the pollen season

The start date of flowering of allergenic species is of great interest in the context of allergy. Such forecasts can help to plan the therapy and design the medical treatment. For this purpose, temperature sum models are usually employed. Designing temperature sum models requires the selection of different parameters such as the base temperature and the start date for the temperature sum. However, the optimal parameterization is often unknown and varies depending on location and species. The purpose of this study was to systematically test parameterizations of temperature sum models based on 12 Swiss pollen stations. The examined taxa include Corylus, Alnus, Fraxinus, Betula, and Poaceae. We tested the simple thermal model type (forcing-only model hereafter) which relies solely on forcing temperatures and the sequential model type that includes also chilling temperatures. The mean absolute error was used to assess the performance of the models. Our study shows that the sequential model could not achieve a discernible reduction of the (statistical) error compared to the forcing-only model for all taxa. The mean absolute error lies roughly between 2 and 4 days with the lowest values for Betula. The optimized parameterizations in combination with temperature forecast and the climatological mean were used during the 2012 pollen season to provide daily updated forecasts of the start of flowering for all five taxa. Improvements of the models could possibly be achieved by testing additional temperature parameters as well as other meteorological factors such as precipitation or irradiation. Identification of a process-oriented model with high statistical performance for all stations would facilitate the implementation in numerical pollen dispersion models.     

Parameters of ragweed pollination in the Lyon’s area (France) from 14 years of pollen counts

This study analyzes the pollen counts obtained from the air of the greater Lyon (corresponding to the urban area of Lyon) an area which has been overrun by ragweed in the last 40 years. Two periods are investigated, 1982–1989 and 1990–1995. The year 1995 deserves specific attention because for the first time a campaign of ragweed eradication was launched in greater Lyon. From the data of the 14 pollination seasons it was possible to define some parameters: subpathological risk period, pathological risk period and the position and level of the pollen peak. Our study indicates the progression of the weed in the infested area over the two periods. In 1995 a slight decrease in the pollen count was observed but this was followed by a second peak probably related to later growth of some plants which had been cut. In this connection, 4 weeks weeding campaign is not long enough and in the future a 6-week campaign without the use of weedkillers should be planned. Determining the parameters of ragweed pollination every year will be useful both to patients and physicians concerned by allergy to ragweed pollen. According to the level of the ragweed pollen in the air, the patients may take appropriate medication. This study emphasizes the necessity to record air pollen concentrations over many years. In particular, the actual impact of cutting ragweed before pollination on ragweed pollen counts can only be evaluated after several years of eradication.     

An attempt to predict the start,peak and end of a pollen season

The different phases, start, peak and end of the pollen season were predicted using a cumulated activity method. This procedure is a development of the temperature sum method. The temperature was transformed to activity (A):

A = 2**[(T+g)/(10*h)] - k.

T = daily mean temperature over the treshold.

g,h,k = coefficients.

Other weather parameters are also to be included in the future.

The activity is cumulated day by day and the sum is used as an indicator of a specific phase. A cumulated activity model is defined by the above formula with specified values of the three coefficients g, h and k. Four conditions stating criteria for valid cumulation days and the cumulated target sum for the phase in question are to be defined. The model was based on pollen and weather data in Stockholm 1973–1988. The cumulated activity method was found to be best applicable to Ulmus, Betula and Pinus, but less useful for Alnus, Corylus and Quercus. The model was not satisfactory for Poaceae and Artemisia.     

Global warming and the earlier start of the Japanese-cedar (Cryptomeria japonica) pollen season in Toyama, Japan

Atmospheric pollen surveys were conducted in Toyama City, Japan over a 21-year period (1983–2003). Airborne pollen was collected by two methods, the gravimetric method and the volumetric method. The gravimetric method indicated that the start of the Cryptomeria japonica pollen season, as indicated by pollen dispersion, has advanced from day 73 (from January 1) in 1983 to day 47 in 2003. Measurements taken using the volumetric method confirmed this trend. There was a significant correlation between the start dates obtained by both methods. Meteorological data indicated that the most noticeable elevation in temperature during the experimental period occurred in February – an increase of 2.1°C. Significant correlations existed between the mean temperatures and the start dates of the pollen season. These results support the steadily increasing number of reports indicating a global warming trend. The temperature change in February in affecting the start dates of the C. japonica pollen season is particularly relevant in the context of human health. Further studies will be needed to clarify the effects of the global warming trend on the pollen season and human health in more detail.     

A comparative study of different temperature accumulation methods for predicting the start of the Quercus pollen season in Cordoba (South West Spain)

The aim of the present paper is to study the influence of air temperature on the start of Quercus pollination in Córdoba (Andalusia, Spain). Sixteen years of pollen counts were used. The start date of the pollen season in this period varied between 26^th February and 7^th April. Chilling requirements and heat accumulation were taken into account although no significant correlation between chilling hours and the start date was observed. Five different predictive methods based on heat accumulation were compared in this paper: 1) Number of days over a threshold; 2) Heat Units (accumulated daily mean temperature after deducting a base temperature); 3) Growing Degrees Days (Snyder 1988), as a measure of physiological growing time; 4) Accumulated maximum temperatures; and 5) Mean maximum temperature. Results indicated that the optimum base temperature for heat accumulation was 11 C^o. This threshold was used in the first three methods mentioned above. Good statistical results were obtained with the five methods, yielding high levels of explanation (p～99%). Nevertheless, the most accurate method appeared to be the Growing Degree Days (GDD^o) method, which indicated that a mean of 127.3 GDD^o must be accumulated from the end of the chilling period up to the beginning of the Quercus pollen season in Córdoba (South West Spain). Results were tested for predicting start dates in 1999 and 2000. The predicted dates were only one day after the actual dates.     

Ambrosia pollen in the air of Lublin, Poland

Studies on Ambrosia pollen concentrations were carried out in Lublin in the period 1995–2004. The effects of a number of meteorological factors were analysed. In the first period of the study, the gravimetric method was used (1995–1999), while in the second period, the volumetric method was applied. The results show an increasing trend in the amount of airborne pollen. The Ambrosia pollen season in Lublin lasts from August to October. Over a period of 5 years, the highest number of pollen grains was recorded in September (53%), followed by August (44%) and October (3%). There were wide variations in annual totals. The annual total pollen counts was 167–1180 grains, with the peak value in 2002. Maximum daily pollen concentrations (56–312 pollen grains m⁻³) were recorded in the first half of August and in the first half of September. On the days when high Ambrosia pollen concentrations occurred, the temperature was above 21°C and the winds were mainly from the southeast, south and east. Maximum intradiurnal concentrations of pollen grains occurred in the afternoon hours. These results indicate, to some degree, that Ambrosia pollen is transported for long distances before descent.     

Forecasting the onset of the grass pollen season in Melbourne (Australia)

In Melbourne, a southern hemisphere city with a cool temperate climate, the grass pollen season has been monitored using a Burkard spore trap for 12 years (11 pollen seasons, which extend from October through January). The onset of the grass pollen season (OGPS) has been defined in various ways using both arbitrary cumulative scores (Sum 75, Sum 100) and percentages (10% Pollen Fly). OGPS, based on the forecast model of pollen season devised by Lejoly-Gabriel (Acta Geogr. Lovan., 13 (1978) 1–260) has been most widely used in efforts to forecast the beginning of the pollen season. OGPS occurred in Melbourne between 20 October to 24 November (average 6 November), a difference of 35 days. Duration of the pollen season ranged from 46 to 81 days, with a mean of 55 days, one of the longest reported. The relationships between onset and various weather parameters for July have enabled us to modify a model, using linear regression analysis, to predict onset. The prediction model is based on a negative correlation between date of onset and the sum of rainfall for July (a winter month). The error of prediction (Ep) is 24% and predicted day of OGPS was precisely predicted on 2 occasions, and on others with a range of accuracy of 3 to 14 days.     

Airborne olive pollen in Vigo (Northwest Spain): a survey to forecast the onset and daily concentrations of the pollen season

Temperature is one of the main factors affecting the start of flowering in tree species that flower at the beginning of spring. Knowledge of the chilling and heat needs required by plants to overcome the period of dormancy enables us to determine the onset of pollination, which is of great importance to allergy sufferers. This study attempted to obtain behaviour models with a view to determining both the onset of the olive pollen season and daily pollen concentrations during the pollination period in Vigo. Monitoring was carried out using a Lanzoni VPPS 2000 pollen trap, from 1995 to 2002 inclusive.

Olea pollen is mainly detected during the spring, principally in May. Given the geographical location, the very limited presence of this tree in the study area and the low Olea pollen concentrations detected in northern Spain as a whole, the values recorded here in the atmosphere of Vigo are particularly striking. A strong correlation was observed between total quantity olive pollen collected over the season and rainfall recorded during the second fortnight in February. According to the proposed model, an average of 680 Chilling Hours (CH) are necessary to overcome the chill period and break the state of bud dormancy, and 481 Growth Degree Days (GDD) °C are needed to induce flowering. Models for predicting daily mean pollen concentrations combine temperature and the previous days' pollen concentrations as predictor variables to provide a high level of prediction.     

The duration and severity of the allergenic pollen season in Istanbul,and the role of meteorological factors

Aerobiologia - Information on the allergenic pollen season provides insight on the state of the environment of a region and facilitates allergy symptom management. We present a retrospective...     

Ragweed (Ambrosia) pollen presence in Livorno,Central Italy: Aerobiological and sensitization data

We have studied Ragweed pollen concentration in the atmosphere of Leghorn (Livorno). where Ragweed is not widespread. Our data, from 1991 to 1995, confirm the presence of Ragweed pollen in the atmosphere of Leghorn in low concentrations (highest value of 11 pollen grains/m³) from August to the end of September. Even if the sensitization level in our area is 6.76%, the clinical significance of Ragweed pollinosis is still very low.     

Ragweed (Ambrosia) pollen presence in Livorno,Central Italy: Aerobiological and sensitization data

We have studied Ragweed pollen concentration in the atmosphere of Leghorn (Livorno), where Ragweed is not widespread. Our data, from 1991 to 1995, confirm the presence of Ragweed pollen in the atmosphere of Leghorn in low concentrations (highest value of 11 pollen grains/m³) from August to the end of September. Even if the sensitization level in our area is 6.76%, the clinical significance of Ragweed pollinosis is still very low.     

Cloning the cDNA encoding the AmbtV allergen from giant ragweed (Ambrosia trifida) pollen.

Ragweed (Ambrosia) pollens contain a number of proteins that cause allergic disease in ragweed-sensitive people. The cloning of the AmbtV cDNA is important, since the 4.4-kDa AmbtV, one of the allergens in giant ragweed (Ambrosia trifida) pollen, serves as a simple model system to study the basic structural requirements for immune recognition of foreign protein allergens. We report the cloning of the AmbtV cDNA by means of the polymerase chain reaction (PCR) using degenerate primers. We generated three sets of overlapping cDNA clones by a combination of PCR and anchored-PCR, and determined the complete nucleotide (nt) sequence. From the nt sequence, the amino acid (aa) sequence of the protein was confirmed and the leader sequence was deduced. This general approach can be used to clone allergen and other cDNAs from complex biological sources provided partial aa sequence information is available. It may be the best available approach in cases where the isolation of clones from a cDNA library is difficult, which proved to be the case for AmbtV.     

Regional variations in the pollen season of Betula in Burgundy: two models for predicting the start of the pollination

Today, 10% of the French people suffer frompollen allergy, a world-wide rising ailmentsince the end of the last century.To prevent the appearance of the symptoms, physicians need precise and early information on the pollination date of the main allergenic species. This wascarried out in Burgundy on birch (Betula), which is responsible for frequent pollinoses inMarch–April. Two of the tested methods were both successful and complementary: the sum oftemperatures and the multiple regression. The first one is very precise but only allows forecastingfive days in advance: this is enough for people suffering from rhinitis or conjunctivitis, who muststart a preventive treatment one or two days before pollination is effective. But for asthmaticpatients, the treatment must one or two weeks in advance; the second method, although alittle less precise, is interesting becauseforecasting can be done at least two weeks inadvance. The results, from 1995 to 1998, were used prospectively in 1999.     

Responses in the start of Betula (birch) pollen seasons to recent changes in spring temperatures across Europe

A shift in the timing of birch pollen seasons is important because it is well known to be a significant aeroallergen, especially in NW Europe where it is a notable cause of hay fever and pollen-related asthma. The research reported in this paper aims to investigate temporal patterns in the start dates of Betula (birch) pollen seasons at selected sites across Europe. In particular it investigates relationships between the changes in start dates and changes in spring temperatures over approximately the last 20 years. Daily birch pollen counts were used from Kevo, Turku, London, Brussels, Zurich and Vienna, for the core period from 1982 to 1999 and, in some cases, from 1970 to 2000. The sites represent a range of biogeographical situations from just within the Arctic Circle through to North West Maritime and Continental Europe. Pollen samples were taken with Hirst-type volumetric spore traps. Weather data were obtained from the sites nearest to the pollen traps. The timing of birch pollen seasons is known to depend mostly on a non-linear balance between the winter chilling required to break dormancy, and spring temperatures. Pollen start dates and monthly mean temperatures for January through to May were compiled to 5-year running means to examine trends. The start dates for the next 10 years were calculated from regression equations for each site, on the speculative basis that the current trends would continue. The analyses show regional contrasts. Kevo shows a marked trend towards cooler springs and later starts. If this continues the mean start date will become about 6 days later over the next 10 years. Turku exhibits cyclic patterns in start dates. A current trend towards earlier starts is expected to continue until 2007, followed by another fluctuation. London, Brussels, Zurich and Vienna show very similar patterns in the trends towards earlier start dates. If the trend continues the mean start dates at these sites will advance by about 6 days over the next 10 years. Following this work, amendments will be needed to pollen calendars and local predictive models. It will also be important to assess the implications of earlier seasons for allergy sufferers.     

The effect of the meteorological factors on the Alnus pollen season in Lublin (Poland)

Alder pollen seasons and the effect of meteorological conditions on daily average pollen counts in the air of Lublin (Poland) were analysed. Alnus pollen grains reach very high concentrations in the atmosphere of this city during the early spring period and the parameters of pollen seasons were very different in the particular years studied. The pollen season lasted on average one month. The highest variation was observed for the peak value and the Seasonal Pollen Index (SPI). The pollen seasons, which started later, had shorter duration. Peak daily average pollen counts and SPI value were higher during the shorter seasons. Similarities in the stages of pollen seasons designated by the percentage method depended on the start date of the pollen season. Season parameters were mainly correlated with thermal conditions at the beginning of the year. Regression analysis was used to predict certain characteristics of the alder pollen season. The highest level of explanation of the variation in Alnus pollen season start and peak dates was obtained in the model using mean temperature in February. The obtained regression models may predict 82% of the variation in the pollen season start date, 73% of the variation in the duration, and 62% in the peak date.     

Poaceae pollen in Galicia (N.W. Spain): characterisation and recent trends in atmospheric pollen season

Airborne Poaceae pollen counts are greatly influenced by weather-related parameters, but may also be governed by other factors. Poaceae pollen is responsible for most allergic reactions in the pollen-sensitive population of Galicia (Spain), and it is therefore essential to determine the risk posed by airborne pollen counts. The global climate change recorded over recent years may prompt changes in the atmospheric pollen season (APS). This survey used airborne Poaceae pollen data recorded for four Galician cities since 1993, in order to characterise the APS and note any trends in its onset, length and severity. Pollen sampling was performed using Hirst-type volumetric traps; data were subjected to Spearman’s correlation test and regression models, in order to detect possible correlations between different parameters and trends. The APS was calculated using ten different methods, in order to assess the influence of each on survey results. Finally, trends detected for the major weather-related parameters influencing pollen counts over the study period were compared with those recorded over the last 30 years. All four cities displayed a trend towards lower annual total Poaceae pollen counts, lower peak values and a smaller number of days on which counts exceeded 30, 50 and 100 pollen grains/m³. Moreover, the survey noted a trend towards delayed onset and shorter duration of the APS, although differences were observed depending on the criteria used to define the first and the last day of the APS.