Keyword: Automatic Weather Station (AWS), solar radiation, Total Solar Eclipse (TSE),

Transcription

1 The Performance of Automatic Weather Station (AWS) on Measurement of Meteorological Parameters during a Total Solar Eclipse of 2016 in Indonesia Kadarsah, Ratnasatyaningsih Center for Research and Development, Indonesian Agency for Meteorology Climatology and Geophysics (BMKG), Jl. Angkasa I No. 2 Kemayoran, Jakarta 10720, Indonesia kadarsah@bmkg.go.id Abstract. The performance analysis of Automatic Weather Station (AWS) on measuring meteorological parameter of a Total Solar Eclipse (TSE) of 2016 in Indonesia is conducted by comparing three groups AWS locations during The first group consists of AWS located in total solar eclipse path (sampling rate of 10 minutes) and plugged in 12 observation stations of Indonesian Mettoffice (BMKG). The second group AWS (sampling rate of 1 minute, 6.30 S, E), and the third group AWS (sampling rate of 20 seconds, N, 127 E) in special settings for observation TSE. Observed meteorological parameters are temperature, humidity, pressure, wind speed and solar radiation. The analysis showed that the third group of TSE able to analyze the events in detail. The AWS has net radiation parameter dropped from Wm-2 at 9:12:10 LT to Wm-2 at 09:52:50 LT. The condition occurs because the event lasted only a very short TSE especially when it reaches its peak with duration of less than 4 minutes. Therefore, for special events such as TSE, measurements of meteorological parameters in the meteorological station should use a shorter sampling rate in order to be better analysis of meteorological parameters and accurate. Keyword: Automatic Weather Station (AWS), solar radiation, Total Solar Eclipse (TSE), Introduction The total solar eclipse of March 9, 2016, occurred over the southern Pacific Ocean. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. On 2016 a total solar eclipse was visible along a narrow corridor which traversed half the Earth, starting in Indian Ocean, extending across the Indonesia (Sumatra, Kalimantan, Sulawesi, North Maluku), and then ended near the Hawaiian islands. The umbra traversed the Indonesia passing directly over the Ternate Island ( N, 127 E). A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometers wide. A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting shadows upon the Earth. It can only take place during new moon. During a total solar eclipse the Moon fully covers face of the Sun. Although eclipses are astronomical phenomena, they also draw considerable interest from atmospheric scientists because solar radiation is the main source of energy to atmosphere. In view of that, solar eclipses provide a natural laboratory for studying Earth s environment response to the abrupt disturbances in radiation. The study results may provide potential benefit to radiative transfer model evaluation or satellite data validation (Maturilli and Ritter, 2016). Variability of surface radiation during solar eclipses has been extensively studied (e.g. Fernandez et al., 1996; Foken et al., 2001;

2 Zerefos et al., 2001; Aplin and Harrison, 2003; Kazadzis et al, 2007; Gerasopoulos et al., 2008; Nymphas et al. 2012; Maturilli and Ritter, 2016). The greatest eclipse, the instant when the axis of the Moon's shadow cone passes closest to Earth's center, occurred over Pacific Oceans. Although there are a number of studies and observations carried out during a solar eclipse over Indonesia, most of them are related to solar physics such as corona (Tanabe et al., 1985; Hiei et al., 198; Pasachoff and Ladd, 1987) and circumsolar dust (Mizutani et al., 1984; Isobe et al., 1985). Evidence of atmospheric gravity waves were also reported (Seykora et al., 1985). The temperature drop reported on other solar eclipse events (e.g. Segal et al., 1996; Anderson, 1999; Hanna, 2000; Founda et al., 2007, Fernandez et al. 1996). The temperature decline induced by the eclipses occurred during the hours of the normal temperature increase should be even larger (Founda et al., 2007). Probably this is caused by the fact that our site was located in a small island surrounded by sea, similar to Kasteloriza in Greece. According to Founda et al. (2007), sea surrounded the island minimizes the temperature response due to its larger heat capacity. We realized the presence of buildings in the vicinity of our measurement site, which may have affected the wind and temperature profiles (Winkler et al., 2001; Nymphas et al., 2009). Therefore, if the measurements are conducted under undisturbed conditions, the temperature may still have been lower. Time lag between mid-eclipse and the time when air temperature reach its minimum is different from one location to the other and is linked to the thermal inertia of the air and the ground (Fernandez et al., 1996; Aplin and Harrison, 2003; Founda et al., 2007). 2. Site and Instrumentation We carried out field campaign on meteorological measurements in Indonesia region (Fig.1, Table 1) from 7-11 March 2016 for the first site. The first site consists of AWS located in total solar eclipse path (sampling rate of 10 minutes) and plugged in 12 observation stations of Indonesian Mettoffice (BMKG). The second site AWS (sampling rate of 1 minute, 6.30 S, E) located in the Jakarta region (Fig 2, Table 2). And the third site AWS (sampling rate of 10 seconds, 0.780N, E) in special settings for observation TSE (Fig.3, Table 3). Similar campaign has been performed during the 26 January 2009 annular solar eclipse (Hanggoro, 2011). The 2016 total solar eclipse has given a unique opportunity to assess impacts of the eclipse on various meteorological parameters in Ternate, Jakarta and other site in over the Indonesia region. The eclipse duration in Ternate is relatively longer compared to other sites in Indonesia. Ternate is one of islands in Maluku, where mean annual rainfall cycle peak in June to July with rainfall amount about 300 mm/month during the peak (Aldrian and Susanto, 2003). Ternate lies close to totality path of the solar eclipse of 2016 and experienced 100% obscuration during the solar eclipse. The eclipse at this location started at 08:36:3.9 LT, with mid-eclipse at 09:52:59.8 LT, and ended at 11:20:50.3 LT. The Local Time is UT+9h (Table 3). We focus for field experiments at the northeast part of Ternate island ( N, 127 E). Our measurement site was located in an open area in a neighborhood. An AWS was installed at this site, equipped with instruments capable of measuring temperature, relative humidity, pressure, wind speed and net radiation.

3 Fig.1 The 2016 total solar eclipse path over Indonesia region. Regions inside the blue lines experienced the total solar eclipse while those outside the line had partial solar eclipse. Red four-square in the figure shows the location of measurement site for the first group. Fig.2 The 2016 total solar eclipse path over Jakarta region. Regions inside the red lines experienced the partial solar eclipse with magnitude Red four-square in the figure shows the location of measurement site for the second group.

4 Fig.3 The 9 th March 2016 total solar eclipse path over the Ternate. Regions inside the red curves experienced the total solar eclipse while those outside the curve had partial solar eclipse. The blue line indicates the central line. Red square in the insert shows the location of measurement site for the third group. The Specifications of AWS instrument deployed during field campaign is described in Table 4. The data was recorded at a sampling interval of 20 seconds and its acquisition is acquired by connecting the instruments to the data logger. The field campaign was conducted from 7 March to Table 1. Timings of TSE of 2016 for 12 sites Phase of eclipse Time (LT) Altitude Azimuth Start of Eclipse 06 : 20 : Beginning of totality -- : - - : : - - : -- : - - Maximum -- : - - : : - - : -- : - - End of Totality -- : - - : : - - : -- : - - End of Eclipse 11 : 20 : Duration of totality -- : - - : -- Duration of eclipse -- : - - : -- Table 2. Timings of TSE of 2016 at Jakarta, Indonesia Phase of eclipse Time (LT) Altitude Azimuth Start of Eclipse 06 : 19 : Beginning of totality -- : - - : : - - : -- : - - Maximum 07 : 21 : End of Totality -- : - - : : - - : -- : - - End of Eclipse 08 : 31 : Duration of totality -- : - - : -- Duration of eclipse 02 : 11 : Eclipse magnitude at maximum 0.905

5 Table 3. Timings of TSE of 2016 at Ternate, Indonesia Phase of eclipse Time (LT) Altitude Azimuth Start of Eclipse 08 : 36 : Beginning of totality 09 : 51 : Maximum 09 : 52 : End of Totality 09 : 54 : End of Eclipse 11 : 20 : Duration of totality 00 : 02 : Duration of eclipse 02 : 44 : Eclipse magnitude at maximum 1,008 Table 4. List of instruments deployed during field campaign. Parameter Device Manufacturers Accuracy Air Temperature Weather Transmitter Vaisala ±0.3 C Relative humidity WXT520 ±3 %RH at 0-90 %RH ±5 %RH at %RH Barometric pressure ±0.5 hpa at 0-30 C ±1 hpa at C Wind speed ±3 % at 10 m/s Net radiation NR-Lite 2 Kipp & Zonen 10 V/Wm - ² 3. Summary and Discussion 3.1 Temperature Generally, the 12 sites show that the temperatures are not clear affected by the eclipse because sampling rate too long (10 minutes) (Fig.4). The sampling rate can t to detect the decreasing of temperature due to eclipse. On the second site at Meteorology Station 745, Kemayoran Jakarta (Fig.5), the temperature shows affected by the eclipse. The air temperature at 1.5 m decline about 1.94 C. A significant drop in diurnal pattern of air temperature during the solar eclipse of 2016 is clearly seen. The temperature started decreasing from C at the mid of the eclipse and this cooling during 20 minutes with the lowest temperature C. Therefore the total temperature decrease is 0.3 C, which is within the range already reported on other solar eclipse events (e.g. Segal et al., 1996; Anderson, 1999; Hanna, 2000; Founda et al., 2007). Hanggoro (2011) reported a temperature decrease of about 4 5 C in Lampung during the annular solar eclipse of 26 January 2009 as observed using AWS. The temperature decline induced by the eclipses occurred during the hours of the normal temperature increase should be even larger (Founda et al., 2007). Probably this is caused by the fact that our site was located in a big city surrounded by building od urban area. We realized the presence of buildings in the vicinity of our measurement site, which may have affected the wind and temperature profiles (Winkler et al., 2001; Nymphas et al., 2009). Therefore, if the measurements are conducted under undisturbed conditions, the temperature may still have been lower. Time lag between mid-eclipse and the time when air temperature reach its minimum is different from one location to the other and is linked to the thermal inertia of the air and the ground (Fernandez et al., 1996; Aplin and Harrison, 2003; Founda et al., 2007).

6 Temperature (C) Temperature ( C) Balikpapan Palu Digi Bariri Jekan Pangkalan Bun Pulau Baai Palangkaraya Palembang Pangkal Pinang sampit Ternate :00 8:40 9:50 11:20 16:00 20:00 Fig.4 Time variation of temperature at 2 m measured on 12 stations at The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse Start 6:20 LT Mid 7:21 LT End 8:31 LT Maret 9 Maret 10 Maret Fig.5 Time variation of air temperature at 2 m measured at Jakarta during Vertical lines denote the onset, mid, and end of the eclipse. At the Ternate site (Fig.6), the results show that those parameters are significantly affected by the eclipse. The air temperature at 1.5 m decline about 2.1 C. However this decrease is lower than the temperature drop reported by Fernandez et al. (1996). The temperature decline induced by the eclipses occurred during the hours of the normal temperature increase should be even larger (Founda et al., 2007). Probably this is caused by the fact that our site was located in a small island surrounded by sea, similar to Kasteloriza in Greece. According to Founda et al. (2007), sea surrounded the island minimizes the temperature response due to its larger heat capacity. We realized the presence of buildings in the vicinity of our measurement site, which may have affected the wind and temperature profiles (Winkler et al., 2001; Nymphas et al., 2009). Therefore, if the measurements are conducted under undisturbed conditions, the temperature may still have been lower. The minimum temperature during the eclipse of

7 Temperature ( C) 2016 is lagging to mid-eclipse by about 20 minutes. Time lag between mid-eclipse and the time when air temperature reach its minimum is different from one location to the other and is linked to the thermal inertia of the air and the ground (Fernandez et al., 1996; Aplin and Harrison, 2003; Founda et al., 2007). This result is within the temperature drop reported on other solar eclipse events (e.g. Segal et al., 1996; Anderson, 1999; Hanna, 2000; Founda et al., 2007). However this decrease is lower than the temperature drop reported by Fernandez et al. (1996) although both eclipses are the total solar eclipse and occurred at similar hour of day March :00 6:00 8:36 9:53 11:20 16:00 18:00 20:00 24:00 Fig.6 Time variation of temperature at 2 m measured at Ternate The beginning and end of the eclipse event is shown by the vertical lines while the dotted line shows the time of solar eclipse 3.2. Humidity Humidity depends on water vaporization and condensation, which, in turn, mainly depends on temperature. There are quite a number of studies and observations made during solar eclipses. They include observations of meteorological parameters, such as wind speed and direction, air temperature, atmospheric pressure, humidity (Anderson etal.,1972; Foken et al.,2001; Sza"owski,2002; Aplin and Harrison,2003). There are large numbers of previous reported studies during the earlier solar eclipses which includes observations of meteorological variables, such as wind speed and direction, humidity, (Nymphas et al., 2009; Krishnan et al., 2004). Their majority observations show the net reduction in temperature, wind speed, water vapour, while RH increases in proportion to obscuration of the sun disc. Observation of humidity at 12 sites (Fig.7) Meteorology Station 745 Kemayoran Jakarta (Fig.8) and Ternate (Fig.9). Increasing humidity in the 12 sites is not as clearly happened in the Meteorology Station 745 and Ternate. This happens because the sampling rate at the 12 sites is too large so it cannot capture the phenomenon of TSE. Humidity at Meteorology Station took about 29 minutes to increase from 85.8 % after the mid-eclipse started and the increase continued until it reached its maximum at 87.2 %. At Ternate, humidity also took about about 13 minutes to increase from 73.1 % to 73.9 %.

8 Humidity(%) Humidity (%) Humidity (%) Balikpapan Palu Digi Bariri Jekan Pangkalan Bun Pulau Baai Palangkaraya Palembang Pangkal Pinang sampit Ternate :00 8:40 9:50 11:20 16:00 20:00 24:00 Fig.7 Time variation of humidity at 2 m measured on 12 stations at The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse Start 6:20 LT Mid 7:21 LT End 8:31 LT 90 8 March Fig.8 Time variation of humidity at Jakarta during Vertical lines denote the onset, mid, and end of the eclipse March :00 6:00 8:36 9:53 11:20 16:00 18:00 20:00 24:00 Fig.9 Time variation of humidity at 2 m measured at Ternate The beginning and end of the eclipse event is shown by the vertical lines while the dotted line shows the time of solar eclipse

9 Radiation (W/m2) Radiation (W/m2) 3.3 Radiation The observed temporal variation of net radiation during at Ternate is shown in Fig. 3a Abrupt decrease in net radiation caused by cloud coverage occurred several times on March 7 and on March 10 in afternoon. These net radiation drops were different from that existed during the eclipse. The main difference between cloud covered sun and an eclipse lies on the negative net radiation during the eclipse, which is similar to night time condition. In contrast to experiments conducted by Eaton et al. (1997) during a partial eclipse and by Ahrens et al. during the total solar eclipse of 11August 1999, this negative radiation is similar to measurements during the total solar eclipse of 11August 1999 carried out by Foken et al. (2001) in Germany and by Nymphas et al. (2009) during the total solar eclipse of in Nigeria. At the 12 sites, the decrease is not clear like at Kemayoran Jakarta and Ternate. At Ternate, It took approximately 36 minutes after the beginning of the eclipse for net radiation to start decreasing (Fig.12). The net radiation dropped from Wm -2 at 9:12:10 LT to Wm -2 at 09:52:50 LT Balikpapan Palu Digi Bariri Jekan Pangkalan Bun Pulau Baai Palangkaraya Palembang Pangkal Pinang sampit Ternate 0 0 4:00 8:409:50 11:20 16:00 20:00 24:00 Fig.10 Time variation of radiation at 2 m measured on 12 stations at The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse Start 6:20 LT Mid 7:21 LT End 8:31 LT March Fig.11 Time variation of radiation measured at Jakarta during Vertical lines denote the onset, mid, and end of the eclipse.

10 Wind Speed(m/s) Wind Speed (m/s) Net Radiation (W/m2) March :00 6:00 8:36 9:53 11:20 16:00 18:00 20:00 24:00 Fig.12 Time variation of radiation at 2 m measured at Ternate The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse 3.4 Wind Speed The observation wind speed at the three locations does not indicate the significant (Fig.13 and Fig.14), even the wind speed at the 12 stations (not shown in the figure) Start 6:20 LT Mid 7:21 LT End 8:31 LT March Fig.13 Time variation of wind speed at 2 m measured at Jakarta during Vertical lines denote the onset, mid, and end of the eclipse March :00 6:00 8:36 9:53 11:20 16:00 18:00 20:00 24:00 Fig.14 Time variation of wind speed at 2 m measured at Ternate The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse

11 Pressure(mBar) Pressure (mbar) Pressure (mbar) 3.5 Pressure The TSE impact on pressure at 12 locations (Fig.15), Jakarta (Fig.16) and in the Ternate (Fig.17) showed no significant effect Balikpapan Palu Digi Bariri Jekan Pangkalan Bun Pulau Baai Palangkaraya Palembang Pangkal Pinang sampit Ternate :00 8:40 9:50 11:20 16:00 20:00 Fig.15 Time variation of pressure at 2 m measured on 12 stations at The beginning and end of the eclipse event is shown by the vertical lines while the dotted line shows the time of solar eclipse Start 6:20 LT Mid 7:21 LT End 8:31 LT March Fig. 16 Time variation of pressure at 2 m measured at Jakarta during Vertical lines denote the onset, mid, and end of the eclipse March :00 6:00 8:36 9:53 11:20 16:00 18:00 20:00 24:00 Fig.17 Time variation of pressure at 2 m measured at Ternate The beginning and end of the eclipse event is shown by the vertical lines while the doted line shows the time of solar eclipse

12 ACKNOWLEDGMENTS The authors thank to Prof.Edvin Aldrian and our colleagues from Division of Research and Development for Meteorology Jose Rizal, Eko Heriyanto, Tri Astuti Nuraini and Sultan Babullah Weather Station in Ternate for their support during surveying for the observation site and installing the instruments. REFERENCES Ahrens, D., Iziomon, M. G., Jaeger, L., Matzarakis, A., & Mayer, H. (2001). Impacts of the solar eclipse of 11 August 1999 on routinely recorded meteorological and air quality data in south-west Germany. Meteorologische Zeitschrift, 10 (3), Aldrian, E., & Susanto, D. (2003). Identification of Three Dominant Rainfall Regions Within Indonesia and Their Relationship to Sea Surface Temperature. International Journal of Climatology, 23, Anderson, J. (1999). Meteorological changes during a solar eclipse. Weather, 54, Aplin, K. L., & Harrison, R. G. (2003). Meteorological effects of the eclipse of 11 August 1999 in cloudy and clear conditions. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 459, pp Eaton, F. D., Hines, J. R., Hatch, W. H., Cionco, R. M., Byers, J., Garvey, D., et al. (1997). Solar Eclipse Effects bserved in the Planetary Boundary Layer Over a Desert. Boundary-Layer Meteorology, 83 (2), Fabian, P., Winterhalter, M., Rappengluck, B., Reitmayer, H., Stohl, A., Koepke, P., et al. (2001). The BAYSOFI Campaign Measurements carried out during the total solar eclipse of August 11, Meteorologische Zeitschrift, 10 (3), Fernandez, W., Hidalgo, H., Coronel, G., & Morales, E. (1996). Changes in Meteorological Variables in Coronel Ovedo, Paraguay, During the Total Solar Eclipse of 3 November Earth, Moon and Planets, 74, Foken, T., Wichura, B., Klemm, O., Gerchau, J., Winterhaller, M., & Weidinger, T. (2001). Micrometeorological measurements during the total solar eclipse of August 11, Meteorologische Zeitschrift, 10 (3), Founda, D., Melas, D., Lykoudis, S., Lisaridis, L., Gerasopoulos, E., Kouvarakis, G., et al. (2007). The effect of the total solar eclipse of on meteorological variables in Greece. Atmos. Chem. Phys., 7, Gerasopoulos, E., Zerefos, C. S., Tsagouri, I., Founda, D., Amiridis, V., Bais, A. F., et al. (2008). The total solar eclipse of March 2006: overview. Atmos. Chem. Phys., 8, Hanggoro, W. (2011). Pengaruh Intensitas Radiasi Saat Gerhana Matahari Cincin terhadap Beberapa Parameter Cuaca. Jurnal Meteorologi dan Geofisika, 12 (2), Hanna, & Hanna, E. (2000). Meteorological effects of the solar eclipse of 11 August Weather, 55, Hiei, E., Shimizu, Y., Miyazaki, H., Imai, H., Sato, K., Kuji, S., et al. (1983). Coronal Structure Observed at the Total Solar Eclipse of 11 June, 1983 in Indonesia. In M. Kitamura, & E. Budding (Eds.), Third Asian-Pacific Regional Meeting of the International Astronomical Union (pp. 9-15). Springer Netherlands. Isobe, S., Hirayama, T., Baba, N., & Miura, N. (1985). Optical polarization observations of circumsolar dust during the 1983 solar eclipse. Nature, 318, Kazadzis, S., Bais, A., Blumthaler, M., Webb, A., Kouremeti, N., Kift, R., et al. (2007). Effects of total solar eclipse of on surface radiation. Atmos. Chem. Phys., 7,

13 Krishnan, P., Kunhikrishnan, P. K., Nair, S. M., Ravindran, S., Ramachandran, R., Subrahamanyam, D. B., et al. (2004). Observations of the atmospheric surface layer parameters over a semi arid region during the solar eclipse of August 11th, Proc. Indian Acad. Sci. (Earth Planet. Sci.), 113, pp Maturilli, M., & Ritter, C. (2016). Surface Radiation during the Total Solar Eclipse over Ny-Ålesund, Svalbard, on 20 March Earth Syst. Sci. Data Discuss., doi: /essd Mizutani, K., Maihara, T., Hiromoto, N., & Takami, H. (1984). Near-infrared observation of the circumsolar dust emission during the 1983 solar eclipse. Nature, 312, Nymphas, E. F., Adeniyi, M. O., Ayoda, M. A., & Oladiran, E. O. (2009). Micrometeorological measurements in Nigeria during the total solar eclipse of 2, Journal ofatmospheric and Solar-Terrestrial Physics, 71, Nymphas, E. F., Otunia, T. A., Adeniyi, M. O., & Oladiran, E. O. (2012). Impact ofthetotalsolareclipseof29march2006onthesurfaceenergy fluxes atibadan,nigeria. Journal of Atmospheric and Solar-Terrestrial Physics, 80, Pasachoff, J. M., & Ladd, E. F. (1987). High-frequency oscillations in the corona observed at the 1983 eclipse. Solar Physics, 109 (2), Ratnam, M. V., Kumar, M. S., Basha, G., Anandan, V. K., & Jayaraman, A. (2010). Effect of the annular solar eclipse of 15 January 2010 on the lower atmospheric boundary layer over a tropical rural station. Journal of Atmospheric and Solar-Terrestrial Physics, doi: /j.jastp Segal, M., Turner, R. W., Prusa, J., Bitzer, R. J., & Finley, S. V. (1996). Solar Eclipse Effect on Shelter Air Temperature. Bulletin of the American Meteorological Society, 77 (1), Seykora, E. J., Bhatnagar, A., Jain, R. M., & Streete, J. L. (1985). Evidence of atmospheric gravity waves produced during the 11 June 1983 total solar eclipse. Nature, 313 (5998), Szałowski, K. (2002). The effect of the solar eclipse on the air temperature near the ground. Journal of Atmospheric and Solar-Terrestrial Physics, 64 (15), Tanabe, H., Isobe, S., Akiyama, H., Koma, Y., Okabe, T., Nishimura, J., et al. (1985). Balloon observation of the 1983 solar eclipse in Indonesia. Advances in Space Research, 5 (1), Winkler, P., Kaminski, U., Kohler, U., Riedl, J., Schroers, H., & Anwender, D. (2001). Development of meteorological parameters and total ozone during the total solar eclipse of August 11, Meteorologische Zeitschrift, 10 (3), Zerefos, C. S., Balis, D., Zanis, P., Meleti, C., Bais, A. F., Tourpali, K., et al. (2001). Changes in Surface UV Solar Irradiance and Ozone over the Balkans during the Eclipse of August 11, Adv. Space Res., 27 (12),