Janusz W. Krzyścin

Aerosol impact on the surface UV radiation from the ground‐based measurements taken at Belsk, Poland, 1980–1996

The aerosol optical depth (AOD) at 550 nm, inferred from the solar radiation measurements taken at Belsk, Poland (52°N, 21°E), with a Sonntag pyrheliometer in the period 1980–1996, has been analyzed for detection of its long-term characteristics. The overall mean AOD equals to about 0.27±0.14 (1σ). The AOD varies in the range 0.1–0.7, with a maximum (0.33) in April-May and a minimum (0.21) in November-December. The long-term decrease of AOD (−7.4% per decade) yields an increase of the surface UV dose (erythemally weighted) of ∼1% per decade. The influence of different parameters on the transmission of UV through the atmosphere on a day-to-day timescale has been analyzed on the basis of the multiple regression model that relates the daily UV erythemal dose at the ground level with total ozone, global solar radiation (surrogate for cloud properties variations), and AOD in the period 1993–1996. It is found that a 10% increase (decrease) of AOD at 550 nm relative to its reference value manifests as ∼1.5% decrease (increase) of the UV erythemal daily dose at the ground level. The changes of UV radiation due to the AOD variations are, in the mean, comparable with those due to total ozone changes. The mean cloud signal in the UV data has been found to be a few times larger than the mean ozone signal. The statistical model suggests that the extreme values of AOD in the Belsk record (that is, 0.1 and 0.7) would be associated with 20–30% changes of the erythemally weighted UV daily dose. This estimate is corroborated by radiative transfer model calculations.

Effects of clouds on the surface erythemal UV-B irradiance at northern midlatitudes: estimation from the observations taken at Belsk, Poland (1999–2001)

Abstract Results of 2-year measurements at Belsk, Poland, have been analyzed to investigate the effects of clouds on ultraviolet (UV) radiation. Data were collected using a Solar Light UV-biometer 501A (erythemally weighed UV irradiances), Kipp&Zonnen CM11 pyranometer (total solar radiation), and SCI-TEC Brewer Spectrophotometer (total ozone, aerosol and thin cloud optical depth). Hourly reports on total cloud cover and cloud type were also used in this study. It is found that overcast conditions prevail over central Poland and the sky is covered mainly by low-level clouds. The averaged cloud properties derived from visual observations correspond with those estimated from satellite measurements. An empirical relationship has been postulated for the cloud reduction factor of the erythemally weighted UV radiation as a function of the cloud reduction factor for total solar radiation. The relation may be used to reconstruct the past UV-time series. It is established that information of cloud amount and type to estimate the UV-B attenuation provides a substantial uncertainty. Stronger attenuation of the UV radiation by real clouds was found than that estimated by a radiative transfer model when examining results of the cloud optical depth at 320 nm and the cloud attenuation of the UV radiation measurements. The reduction of the erythemally weighted UV irradiance by thin clouds seems to be independent of the cloud type. It is reported that 1.4% of UV-B irradiance measurements were cloud enhanced in the snowless period of the year. The maximum UV-B enhancement of ∼20% greater than an equivalent clear-sky value was found. Numerous enhancements occurred when high-, mid-, and low- (broken Cu) clouds appeared simultaneously. Similar range of the observed enhancements and cloud composition as in previous cloud enhancement studies (over low latitudinal regions) suggest that common mechanisms may govern this phenomenon in low- and mid-latitudinal regions.

A mathematical model for seasonal variability of vitamin D due to solar radiation

It is widely recognized that vitamin D deficiency has detrimental health consequences. The ultraviolet (UV) B radiation increases the serum vitamin D level, expressed by 25-hydroxyvitamin-D(3) [25(OH)D]. An analytical model is presented to calculate the serum 25(OH)D changes throughout a year, caused by the solar exposure variability due to geophysical and habitual factors. The model is tuned by taking into account recent experimental results of serum 25(OH)D changes, after a series of artificial (by fluorescent tubes) UV exposures. The model uses the erythemal and vitamin D weighted irradiances, inferred from the Brewer spectrophotometer and the Kipp and Zonen broad-band meter measurements, carried out in Belsk (52°N, 21°E), Poland, in 2010. The modeled seasonal pattern of the serum 25(OH)D concentration in Polish indoor workers is only slightly different, than in subjects with typical outdoor activity habits, and in those with sun-seeking behavior. A deep minimum in the serum 25(OH)D concentration appears in late winter, regardless of outdoor activity habits. An extra sunbathing to boost the vitamin D level is not worth taking, because of a minor improvement of the vitamin D status, and because of a greater erythema risk. It would be much safer and more effective to maintain an adequate vitamin D level through diet supplements, even in summer, for non sun-seeking subjects.

Extreme events in total ozone over the Northern mid-latitudes: An analysis based on long-term data sets from five European ground-based stations

We apply methods from extreme value theory to identify extreme events in high (termed EHOs) and low (termed ELOs) total ozone and to describe the distribution tails (i.e. very high and very low values) of five long-term European ground-based total ozone time series. The influence of these extreme events on observed mean values, long-term trends and changes is analysed. The results show a decrease in EHOs and an increase in ELOs during the last decades, and establish that the observed downward trend in column ozone during the 1970–1990s is strongly dominated by changes in the frequency of extreme events. Furthermore, it is shown that clear ‘fingerprints’ of atmospheric dynamics (NAO, ENSO) and chemistry [ozone depleting substances (ODSs), polar vortex ozone loss] can be found in the frequency distribution of ozone extremes, even if no attribution is possible from standard metrics (e.g. annual mean values). The analysis complements earlier analysis for the world’s longest total ozone record at Arosa, Switzerland, confirming and revealing the strong influence of atmospheric dynamics on observed ozone changes. The results provide clear evidence that in addition to ODS, volcanic eruptions and strong/moderate ENSO and NAO events had significant influence on column ozone in the European sector.

On an improvement of UV index forecast: UV index diagnosis and forecast for Belsk, Poland, in Spring/Summer 1999

Abstract A forecast of the UV index for the following day is presented. The standard approach to the UV index modelling is applied, i.e., the clear-sky UV index is multiplied by the UV cloud transmission factor. The input to the clear-sky model (tropospheric ultraviolet and visible—TUV model, Madronich, in: M. Tevini (Ed.), Environmental Effects of Ultraviolet Radiation, Lewis Publisher, Boca Raton, 1993, p. 17) consists of the total ozone forecast (by a regression model using the observed and forecasted meteorological variables taken as the initial values of aviation (AVN) global model and their 24-hour forecasts, respectively) and aerosols optical depth (AOD) forecast (assumed persistence). The cloud transmission factor forecast is inferred from the 24-h AVN model run for the total (Sun+sky) solar irradiance at noon. The model is validated comparing the UV index forecasts with the observed values, which are derived from the daily pattern of the UV erythemal irradiance taken at Belsk ( 52° N , 21° E ), Poland, by means of the UV Biometer Solar model 501A for the period May–September 1999. Eighty-one percent and 92% of all forecasts fall into ±1 and ±2 index unit range, respectively. Underestimation of UV index occurs only in 15%. Thus, the model gives a high security in Sun protection for the public. It is found that in ∼35% of all cases a more accurate forecast of AOD is needed to estimate the daily maximum of clear-sky irradiance with the error not exceeding 5%. The assumption of the persistence of the cloud characteristics appears as an alternative to the 24-h forecast of the cloud transmission factor in the case when the AVN prognoses are not available.

Vitamin D serum level changes in psoriatic patients treated with narrowband ultraviolet B phototherapy are related to the season of the irradiation.

Vitamin D is produced in the human skin by short wavelength (290–315 nm) ultraviolet (UV) radiation.

UV controlling factors and trends derived from the ground‐based measurements taken at Belsk, Poland, 1976–1994

Monthly means of UV erythemal dose at ground level from the Robertson-Berger (RB) sunburn meter (1976-1992) and the UV-Biometer model 501 MED meter (1993-1994) located at Belsk (21°E, 52°N), Poland, are examined. The monthly means are calculated from all-sky daily means of UV erythemal dose. Ancillary measurements of column ozone (by Dobson spectrophotometer), sunshine duration (by Campbell-Stokes heliograph), and total (sun and sky) radiation (by a pyranometer) are considered to explain variations in the UV data. A multiple regression model is proposed to study trends in the UV data. The model accounts for the UV erythemal dose changes induced by total ozone, sunshine duration (surrogate for cloud cover variations), or total solar radiation (surrogate for combined cloud cover and atmospheric turbidity impact on the UV radiation), trends due to instrument drift, step changes in the data, and serial correlations. A strong relationship between monthly all-sky UV erythemal dose changes and total ozone (and total solar radiation) is found. Calculations show that an erythemal radiative amplification factor (RAF) due to ozone under all skies is close to its clear-sky value (about 1). However, the model gives evidence that the RAF due to ozone is smaller for cloudier (and/or more turbid) atmospheres than long-term reference. Total solar radiation change of 1% is associated with a change of 0.7% in the UV erythemal dose. Modeled trends in the Belsks UV data, inferred from the model using ozone and total solar radiation as the UV forcing factors, are 2.3% ± 0.4% (1σ) per decade in the period 1976-1994. The large increase in the UV erythemal dose, of the order of 4% per decade due to ozone depletion (-3.2% per decade), is partially compensated by a decreasing tendency (-2.8% per decade) in total solar radiation. The model estimates the trend in the UV data of the order of 0.1% per decade (not statistically significant) due to superposition of the instrument drift and long-term effects related to other UV influencing factors (not parameterized by the model).

Eyjafjallajokull volcano ash observed over Belsk (52° N, 21° E), Poland, in April 2010

Eruption of Eyjafjallajökull volcano took place on 13–14 April 2010, and created an ash cloud moving towards densely populated areas in Europe. Dispersion models show that the cloud appeared over Poland at noon on 16 April. Measurements of optical properties of the atmospheric aerosols by the Cimel Sun Photometer (optical thickness and volume size distribution) and lidar (backscatter coefficient) at Belsk (52° N, 21° E) for the period 15–26 April 2010 are examined to find volcanic ash in the atmosphere over the site. Thin aerosol clouds, linked to the volcanic eruption, were found below 5 km, and their optical thickness (at 500 nm) varied only slightly in the range of a few hundredths. The optical depth of the aerosol clouds in the 5–7.5 km layer was less than 0.01.

Space-based estimation of the solar UV-B doses for psoriasis heliotherapy in Poland using OMI data for the period 2005-2011.

A UV model is proposed to reconstruct the biologically weighted doses at the ground-level, erythemal, vitamin D(3), and antipsoriatic effective doses, based on the space data from the Ozone Monitoring Instrument on board of NASA EOS Aura spacecraft for the period 2005-2011. The model is training using the results of spectral UV measurements carried out at Belsk, Poland. The model outcome is verified using the UV spectra measured at Hradec Kralove, Czech Republic. The model uncertainty is almost the same for all examined action spectra and comparable to that found in earlier studies on differences between the satellite overpasses and ground-based erythemal data. Antipsoriatic doses, taken during 2h exposure periods near local noon, are reconstructed for selected sites in Poland to find if heliotherapy would be an alternative to standard treatment of psoriasis by tube irradiation in medical cabinets. Mountain-resort in the southern Poland, Zakopane, and rural-site in Central Poland, Belsk, are among the best location of potential heliotherapy centers in Poland for late spring/summer season. Łeba, resort on the Baltic Sea coast, is a potential heliotherapy center in June and July. The methodology to disclose possible heliotherapy periods over the territory of Poland could be extended to any region. It would help to prepare an optimal schedule of antipsoriatic heliotherapy that accounts for local weather conditions and medical standards of using UV cabinets.

Impact of the ozone profile on the surface UV radiation: Analyses of the Umkehr and UV measurements at Belsk (52°N, 21°E), Poland

We consider changes of the ozone vertical profile using Umkehr observations taken at Belsk (52°N, 21°E) by means of the Dobson spectrophotometer in the period 1963-1998. The ratio of ozone content in the Umkehr layers 1-4 (0-23.5 km) to total column ozone (layers 1-10) is used as a proxy characterizing the shape of the ozone profile. The long-term tendency in the ratio appears statistically insignificant for the periods 1963-1979 and 1980-1998. Analysis of the residuals from the multiple-regression model, which relates fluctuations in the measured daily UV doses (erythemally weighted) at Belsk with those in total ozone and global radiation (surrogate for the cloud and/or aerosol property variations) for the period 1993-1998, reveals that a 0.1 decrease (increase) of the ratio manifests as ∼ 2-3% increase (decrease) of the daily dose relative to its normal value. Extreme change in the vertical structure of the atmosphere yields about a 5% change in the UV daily dose. The simulations by means of a radiative transfer model also show that possible changes of the vertical structure of the atmosphere are rather a minor source of day-to-day variations in surface UV radiation. It is suggested that the temporal variations of the ratio may give an insight into the year-to-year variations of dynamical processes affecting total ozone content in the Northern Hemisphere midlatitudes.