Extension of WRF-Chem for birch pollen modelling-a case study for Poland.

In recent years, allergies due to airborne pollen allergens have shown an increasing trend, along with the severity of allergic symptoms in most industrialized countries, while synergism with other common atmospheric pollutants has also been identified as affecting the overall quality of citizenly life. In this study, we propose the state-of-the-art WRF-Chem model, which is a complex Eulerian meteorological model integrated on-line with atmospheric chemistry. We used a combination of the WRF-Chem extended towards birch pollen, and the emission module based on heating degree days, which has not been tested before. The simulations were run for the moderate season in terms of birch pollen concentrations (year 2015) and high season (year 2016) over Central Europe, which were validated against 11 observational stations located in Poland. The results show that there is a big difference in the model's performance for the two modelled years. In general, the model overestimates birch pollen concentrations for the moderate season and highly underestimates birch pollen concentrations for the year 2016. The model was able to predict birch pollen concentrations for first allergy symptoms (above 20 pollen m-3) as well as for severe symptoms (above 90 pollen m-3) with probability of detection at 0.78 and 0.68 and success ratio at 0.75 and 0.57, respectively for the year 2015. However, the model failed to reproduce these parameters for the year 2016. The results indicate the potential role of correcting the total seasonal pollen emission in improving the model's performance, especially for specific years in terms of pollen productivity. The application of chemical transport models such as WRF-Chem for pollen modelling provides a great opportunity for simultaneous simulations of chemical air pollution and allergic pollen with one goal, which is a step forward for studying and understanding the co-exposure of these particles in the air.

Are estimates of wind characteristics based on measurements with Pitot tubes and GNSS receivers mounted on consumer-grade unmanned aerial vehicles applicable in meteorological studies?

The objective of this paper is to empirically show that estimates of wind speed and wind direction based on measurements carried out using the Pitot tubes and GNSS receivers, mounted on consumer-grade unmanned aerial vehicles (UAVs), may accurately approximate true wind parameters. The motivation for the study is that a growing number of commercial and scientific UAV operations may soon become a new source of data on wind speed and wind direction, with unprecedented spatial and temporal resolution. The feasibility study was carried out within an isolated mountain meadow of Polana Izerska located in the Izera Mountains (SW Poland) during an experiment which aimed to compare wind characteristics measured by several instruments: three UAVs (swinglet CAM, eBee, Maja) equipped with the Pitot tubes and GNSS receivers, wind speed and direction meters mounted at 2.5 and 10 m (mast), conventional weather station and vertical sodar. The three UAVs performed seven missions along spiral-like trajectories, most reaching 130 m above take-off location. The estimates of wind speed and wind direction were found to agree between UAVs. The time series of wind speed measured at 10 m were extrapolated to flight altitudes recorded at a given time so that a comparison was made feasible. It was found that the wind speed estimates provided by the UAVs on a basis of the Pitot tube/GNSS data are in agreement with measurements carried out using dedicated meteorological instruments. The discrepancies were recorded in the first and last phases of UAV flights.

The impact of data assimilation into the meteorological WRF model on birch pollen modelling.

We analyse the impact of ground-based data assimilation to the Weather Research and Forecasting (WRF) meteorological model on parameters relevant for birch pollen emission calculations. Then, we use two different emission databases (BASE - no data assimilation, OBSNUD - data assimilation for the meteorological model) in the chemical transport model and evaluate birch pollen concentrations. Finally, we apply a scaling factor for the emissions (BASE and OBSNUD), based on the ratio between simulated and observed seasonal pollen integral (SPIn) to analyse its impact on birch concentrations over Central Europe. Assimilation of observational data significantly reduces model overestimation of air temperature, which is the main parameter responsible for the start of pollen emission and amount of released pollen. The results also show that a relatively small bias in air temperature from the model can lead to significant differences in heating degree days (HDD) value. This may cause the HDD threshold to be attained several days earlier/later than indicated from observational data which has further impact on the start of pollen emission. Even though the bias for air temperature was reduced for OBSNUD, the model indicates a start for the birch pollen season that is too early compared to observations. The start date of the season was improved at two of the 11 stations in Poland. Data assimilation does not have a significant impact on the season's end or SPIn value. The application of the SPIn factor for the emissions results in a much closer birch pollen concentration level to observations even though the factor does not improve the start or end of the pollen season. The post-processing of modelled meteorological fields, such as the application of bias correction, can be considered as a way to further improve the pollen emission modelling.

Adequate vitamin D3 skin synthesis versus erythema risk in the Northern Hemisphere midlatitudes.

Health-optimum-exposure index (HOEI) is proposed to assess if the prescribed amount of vitamin D3 (target value) could be synthesized in the human skin without erythema appearance. It is defined as the ratio between the vitamin D3 quantity received during the maximum allowed outdoor exposure without erythema risk and the target value. Sunbathing is safe for HOEI>1 and 1/HOEI represents a part of minimal erythema dose (MED) necessary to obtain the target value. We examine the following targets: a vitamin D3 quantity equivalent to 1000 IU vitamin D3 taken orally, and an optimal vitamin D3 quantity defined by Krzyscin et al. (2016). The biologically weighted (previtamin D3 and erythemal) doses from the Northern Hemisphere midlatitudinal stations are analyzed to find HOEI dependence on personal and meteorological factors. HOEI depends mostly on the exposed skin area, person's age, and sun elevation at noon but not on the Fitzpatrick skin phototype. We found that only young adults (<21 yr) could safely obtain vitamin D3 quantity, which is equivalent to 1000 IU taken orally, almost throughout the whole year. Duration of such exposures appears <1 h only in the warm subperiods of the year (April-September) for a person with minimal erythema dose of 330 J m-2. Exposing larger part of the body (~30%) enables the oldest persons (>59 yr) to reach 1000 IU target during warm days in spring and summer. The optimal daily vitamin D3 quantity could only be synthesized only by young adults for about 40-60% of days in the May-August period if they expose at least 1/3 part of their body surface area. Vitamin D3 supplementation seems to be necessary over the whole year for the oldest persons with daily dosage of ~2000 IU but reduced to ~1000 IU in summer for sunseekers exposing significant part of the body.

Perspectives of UV nowcasting to monitor personal pro-health outdoor activities.

Nowcasting model for online monitoring of personal outdoor behaviour is proposed. It is envisaged that it will provide an effective e-tool used by smartphone users. The model could estimate maximum duration of safe (without erythema risk) outdoor activity. Moreover, there are options to estimate duration of sunbathing to get adequate amount of vitamin D3 and doses necessary for the antipsoriatic heliotherapy. The application requires information of starting time of sunbathing and the user's phototype. At the beginning the user will be informed of the approximate duration of sunbathing required to get the minimum erythemal dose, adequate amount of vitamin D3, and the dose necessary for the antipsoriatic heliotherapy. After every 20-min the application will recalculate the remaining duration of sunbathing based on the UVI measured in the preceding 20 min. If the estimate of remaining duration is <20 min the user will be informed that the deadline of sunbathing is approaching. Finally, a warning signal will be sent to stop sunbathing if the measured dose reaches the required dose. The proposed model is verified using the data collected at two measuring sites for the warm period of 2017 (1st April-30th September) in large Polish cities (Warsaw and Lodz). First instrument represents the UVI monitoring station. The information concerning sunbathing duration, which is sent to a remote user, is evaluated on the basis of the UVI measurements collected by the second measuring unit in a distance of ~7 km and 10 km for Warsaw and Lodz, respectively. The statistical analysis of the differences between sunbathing duration by nowcasting model and observation shows that the model provides reliable doses received by the users during outdoor activities in proximity (~10 km) to the UVI source site. Standard 24 h UVI forecast based on prognostic values of total ozone and cloudiness appears to only be valid for sunny days.

Controlling sunbathing safety during the summer holidays - The solar UV campaign at Baltic Sea coast in 2015.

Information regarding the intensity of surface UV radiation, provided for the public, is frequently given in terms of a daily maximum UV Index (UVI), based on a prognostic model. The quality of the UV forecast depends on the accuracy of column amount of ozone and cloudiness prediction. Daily variability of UVI is needed to determine the risk of the UV overexposure during outdoor activities. Various methods of estimating the temporary UVI and the maximum duration of UV exposures (received a dose equal to minimal erythemal dose - MED), at the site of sunbathing, were compared. The UV indices were obtained during a field experiment at the Baltic Sea coast in the period from 13th to 24th July 2015. The following UVI calculation models were considered: UVI measurements by simple hand-held biometers (Silver Crest, Oregon Scientific, or more advanced Solarmeter 6.5), our smartphone models based on cloud cover observations at the site and the cloudless-sky UVI forecast (available for any site for all smartphone users) or measured UVI, and the 24h weather predictions by the ensemble set of 10 models (with various cloud parameterizations). The direct UV measurements, even by a simple biometer, provided useful UVI estimates. The smartphone applications yielded a good agreement with the UV measurements. The weather prediction models for cloudless-sky conditions could provide valuable information if almost cloudless-sky conditions (cloudless-sky or slightly scattered clouds) were observed at the sunbathing site.

Optimal vitamin D3 daily intake of 2000IU inferred from modeled solar exposure of ancestral humans in Northern Tanzania.

Recently, high serum 25-hydroxyvitamin D concentration (~110nmol/L) was found in the Hadza tribe still keeping ancient hunter-gather life style. This level could serve as optimal vitamin D level that was built during millennia of human evolution. The personal vitamin D3 effective solar exposures of the Hadza adults are estimated using radiative model simulations with input from the satellite observations over lake Eyasi (3.7°S, 35.0°E). The calculations are carried out assuming the Hadza typical clothing habits and specific scenarios of the out-door activity comprising early morning and late afternoon working time in sun and prolonged midday siesta in the shade. The modeled doses received by the Hadza are converted to the vitamin D3 effective daily doses pertaining to the lighter skinned persons. We propose a novel formula to get adequate vitamin D level - exposure of 1/3 MED around local noon to 1/3 part of the whole body during warm sub-period of the year in the low- and mid-latitude regions. Such daily solar exposure is equivalent to ~2000IU of vitamin D3 taken orally. For many contemporary humans with limited out-door activity habit achieving such daily norm requires vitamin D3 supplementation of 2000IU throughout the whole year.