Micrometeorological measurements in Nigeria during the total solar eclipse of 29 March, 2006 E.F. Nymphas �, M.O. Adeniyi 1, M.A. Ayoola 2, E.O. Oladiran 3 Department of Physics, University of Ibadan, Ibadan, Nigeria a r t i c l e i n f o Article history: Received 8 September 2008 Received in revised form 15 April 2009 Accepted 16 April 2009 Available online 2 June 2009 Keywords: Total solar eclipse Solar radiation Micrometeorology Atmospheric pressure a b s t r a c t The total solar eclipse of 29 March, 2006 which was visible at Ibadan (7.551N, 4.561E), south-western Nigeria was utilized to document atmospheric surface-layer effects of the eclipse for the first time in Nigeria. The meteorological parameters measured are global radiation, net radiation, wind speed (at different heights), atmospheric pressure and soil temperature (5, 10 and 30 cm), moisture and heat flux and rainfall. The results revealed remarkable dynamic atmospheric effects. The observations showed that the incoming solar radiation, net radiation and air temperature were significantly affected. There was an upsurge of wind speed just before the first contact of the eclipse followed by a very sharp decrease in wind speed due to the cooling and stabilization of the atmospheric boundary layer. The atmospheric pressure lags the eclipse maximum by 1h 30min, while the soil temperature at 5 and 10 cm remain constant during the maximum phase of the eclipse. & 2009 Published by Elsevier Ltd. 1. Introduction One of nature’s most spectacular events is solar eclipse. It occurs when the Moon covers the Sun casting its shadow on the Earth. It is an astronomical phenomenon that has been known and observed since the earliest ages. Its astronomical background is well understood and documented (e.g. Mitchell, 1951; Zirker, 1984; Littman and Willcox, 1991). During a total solar eclipse, the Moon totally screens the incoming solar radiation to some location on the Earth’s surface, thereby, causing complete darkness lasting up to a few minutes. Spectacular optical phenomena, such as the changing colour of the sky, the moving shadow, the shadow bands, the Sun’s chromosphere, the corona, etc. can be seen if the eclipse takes place on a clear sky day (Anfossi et al., 2004; Stoeva et al., 2008; Krumov and Krezhova, 2008; Aushev et al., 2008). Although a solar eclipse is of astronomical interest, it also provides a unique opportunity for meteorologists to study the response of the atmosphere or biosphere to the sudden turn off/on of the incident solar radiation during and after the eclipse. The combine effect of the sudden light ‘‘switch off’’ and increased humidity together with temperature decrease during eclipses has been reported to have an impact on forest trees (Economou, et al., 2008). This phenomenon is similar to those that occur as night falls, but much more abrupt than the gradual decrease in solar energy as the Sun sets. Meteorological and other measurements during eclipses is interesting because the atmosphere, the Earth’s environment, plants and animals, marine and aquatic life, etc. response differently to the sudden and abrupt short-term disturbance in radiation and the thermal balance in the atmo- sphere (Segal et al., 1996; Eaton et al., 1997; Ahrens et al., 2001; Aplin and Harrison, 2003; Eckermann et al., 2007; Gerasopoulos et al., 2007; Economou et al., 2008). The interest expressed by people to the spectacular phenomenon of solar eclipses is indicated by over one and a half million results that can be found under the search ‘‘Solar eclipse March 2006’’ in the web (Gerasopoulos et al., 2007). The importance of eclipse meteorol- ogy is indicated by the following quotation from Clayton’s summary: ‘‘The eclipse may be compared to experiment by nature in which all the causes that complicate the origin of ordinary cyclone are eliminated except that of direct and rapid change of temperature’’ (Kimbal and Fergusson, 1919). 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 et al., 1972; Foken et al., 2001; Sza"owski, 2002; Aplin and Harrison, 2003), gravity waves (Chimonas, 1971; Davies, 1982; Seykora et al., 1985; Singh et al., 1989; Jones, 1999; Zerefos et al., 2007), ozone measurements (Bojkov, 1968; Chakrabarty et al., 1997; Zerefos et al., 2000, 2001; Chudzyński et al., 2001; Winkler et al., 2001; Zanis et al., 2007; Tzanis et al., 2007). Others include the sudden drop of the ion and ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jastp Journal of Atmospheric and Solar-Terrestrial Physics 1364-6826/$ - see front matter & 2009 Published by Elsevier Ltd. doi:10.1016/j.jastp.2009.04.014 � Corresponding author. Tel.: +234 8023516602. E-mail addresses: efnda@yahoo.co.uk (E.F. Nymphas), mojisolaadeniyi@yahoo.com (M.O. Adeniyi), rayola40@yahoo.com (M.A. Ayoola), oluyemi_oladiran@yahoo.co.uk (E.O. Oladiran). 1 Tel: +234 8033579081. 2 Tel: +234 8055305482. 3 Tel: +234 8034711147. Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–1253 UNIV ERSIT Y O F IB ADAN L IB RARY www.sciencedirect.com/science/journal/atp www.elsevier.com/locate/jastp dx.doi.org/10.1016/j.jastp.2009.04.014 mailto:efnda@yahoo.co.uk mailto:mojisolaadeniyi@yahoo.com mailto:rayola40@yahoo.com mailto:oluyemi_oladiran@yahoo.co.uk electron density of the ionosphere due to the solar eclipse (Horvath and Thean, 1972; Jakobi and Kürschner, 2000; Altadill et al., 2001; Baran et al., 2003; Gerasopoulos et al., 2007), changes in direct solar irradiance (Kolarž et al., 2005), and heat and momentum fluxes within the boundary layer, (Foken et al., 2001; Sza"owski, 2002) etc. Kirshnan et al. (2004) and Anfossi et al. (2004) provided further evidence for the decrease of turbulent fluxes during eclipses. The most important environmental effects of an eclipse takes place in the microscale and involved changes of the boundary layer parameters of physical and chemical nature such as the thermodynamic processes and plants’ response for light level decreases which subsequently causes a decrease of CO2 fluxes (Fabian et al., 2001; Economou et al., 2008). The impact of an eclipse on air temperature, which became noticeable when the Sun is about half-covered (Anderson, 1999), is very important since it changes the stability and convective processes of the boundary layer. The amplitude and pattern of temperature drop vary between less than 1 and 3.9 1C depending on several factors such as latitude, the season and time of the day, climatic conditions, the height of measurements, topography, soil con- ductivity, etc. (Founda et al., 2007). The latitudinal dependence of these parameters has shown that in the mid latitudes, it depends upon the time of the eclipse occurrence and nonlinearly upon the degree of eclipse obscuration. For example, Segal et al. (1996) have shown that for an equal degree of peak obscuration at different latitude but same longitude, the eclipse obscuration may be different enough to produce none negligible differences in temperature drops. The variation of some of the parameters with latitude is shown in Table 1 taken from Segal et al. (1996). The effects of a solar eclipse on Earth’s atmospheric surface layer are very controversial. In the literature, many studies have reported on the decrease of wind speed during a solar eclipse (Aplin and Harrison, 2003; Ahrens et al., 2001). However, there are also reports on the upsurge of wind speed before the start of an eclipse event (Anderson and Keefer, 1975; Eaton et al., 1997). This ‘‘wind eclipse’’ is usually attributed to either a wind chill effect (Founda et al., 2007) and or a cold-front in the penumbra (Aplin and Harrison, 2003, Anderson, 1999). The mean wind flow during a solar eclipse has been observed to be greatly decelerated (Fernández et al., 1996; Kirshnan et al., 2004; Stoev et al., 2005). The deceleration of the mean wind is due to the combined effect of the decrease of thermal gradient, the stabilization of surface layer following the drop of temperature and suppression of turbulence processes. This effect was not observed by Eaton et al. (1997) who observed variability in the mean wind speed and vertical momentum fluxes in New Mexico during the partial solar eclipse of 10 May, 1994. Kirshnan et al. (2004) detected pronounced eclipse-induced changes in turbulent and spectral characteristics of wind in India during the eclipse of 11 August, 1999. Depending on the synoptic situations, orographic winds can be formed and be noticeable on a local level. On 29 March, 2006, a total solar eclipse started in Brazil and extends across the Atlantic, northern Africa and central Asia where it ended at northern Mongolia at sunset. During its traverse across Africa, the Moon’s shadow enters the Gulf of Guinea passing through Ghana, Togo and Benin republics at 0.958km/s (Espenak and Anderson, 2006). The penumbra enters Nigeria at a further reduced speed of 0.818km/s taking about 16min to cross Western Nigeria into Niger Republic. During that time, the path of totality has expanded from 184km, when it entered Africa, to 188 km. The Sun’s altitude in Nigeria during the eclipse was 521 and the magnitude of the eclipse was about 97% (Espenak and Anderson, 2006). The path of the total solar eclipse of 29 March, 2006 as it passes across Africa is shown in Fig. 1. The shadow path, after leaving Brazil, curves northward across the Atlantic and then more northerly as it reaches the African coast, crossing the northern side of the Inter Tropical Convergence Zone (ITCZ) in ARTICLE IN PRESS Table 1 Temperature drops (DT1), the likely temperature drop at the eclipse peak (DT2) (subscripts ‘‘u’’ and ‘‘m’’ denote observed and modeled values, respectively), and maximum eclipse obscuration (EO) (%) for various sites during the 10 May, 1994 eclipse. Site Latitude (1N) SH (hhmm) EO (%) DT1 (1C)u DT2 (1C)u DT2 (1C)m Comment Boulder, CO 40 0931 74.5 1.1 2.2 2.9 PROFS, roof Estes Park, CO 40 0930 73.5 1.4 3.6 2.9 PROFS. 1.5m Ft. Collins, CO 41 0933 73.2 0.9 2.2 2.9 PROFS, 1.5m Keenestairg, CO 40 0935 74.5 1.4 3.0 2.9 PROFS, 1.5m Lakewood, CO 40 0931 75.3 1.8 2.7 2.9 PROFS, 1.5m Longmout, CO 40 0932 74.0 1.5 2.8 2.9 PROFS, 1.5m Loveland, CO 40 0933 73.5 0.7 3.3 2.9 PROFS, 1.5m Nunn, CO 41 0933 73.1 0.5 1.9 2.9 PROFS, 1.5m Rollinsvillc, CO 40 0929 74.5 0.8 2.3 2.9 PROFS, 1.5m Ames, IA 42 1041 82.7 1.3 2.3 3.8 Roof Chicago, TL 42 1117 88.2 5.8 6.1 4.5 Roof *Springfiled, IL 40 1101 88.9 5.0 6.1 4.5 1.6m Lamberton, MN 44 1035 76.0 0.8 3.1 2.9 – Morris, MN 46 1036 71.5 0.5 2.3 2.5 – St. Paul, MN 45 1049 75.2 0.5 1.5 2.8 Cirrus Waseca. MN 44 1045 76.5 1.0 3.7 2.9 – *Columbia, MO 39 1044 88.9 3.9 – 4.5 Airport *Columbia, MO 39 1044 88.9 6.4 – 4.5 0–15m *Sedalia, MO 39 1038 88.9 3.0 4.2 4.5 1.1m *Norman. OK 35 1006 88.7 2.0 3.6 4.5 – Source: Segal et al. (1996). The latitude of each site and the timing of the eclipse peak (SH) are also provided. Annular sites are indicated with an asterisk. Available shelter heights (in meters above ground level) are given in the comment column. Fig. 1. The path of the total solar eclipse of 29 March, 2006 through Africa. Also shown is the location of Ibadan. (Espenak and Anderson, 2006) (Source: http:// Sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html) E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–12531246 UNIV ERSIT Y O F IB ADAN L IB RARY http://Sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html http://Sunearth.gsfc.nasa.gov/eclipse/SEmono/TSE2006/TSE2006.html northern Nigeria and into the drier climate controlled by winds from the Sahara Desert. During the total solar eclipse of 29 March, 2006, we carried out micrometeorological measurements at Ibadan and Nigeria. This measurement, to our knowledge, is the first of its kind to be made during a total solar eclipse in West Africa. In this article, we report on some aspects of our measurements during the total solar eclipse of 29 March, 2006. The observed changes in the energy balance of this region during the same event are reported in a separate paper. The instruments diploid during the measurement and the description of the site is presented in Section 2, while Section 3 discusses the climatology of the study area. The results and discussion parameter-by-parameter are presented in Sections 4–6. The paper ends by a summary of the major findings in Section 7. 2. Measurement site and instrumentation The meteorological data used in this report is collected from one of three stations of the Nigeria Micrometeorological Experi- ment (NIMEX) in Ibadan (7.381N, 3.981E), Nigeria. The experiment started in February 2004 at the teaching and research farm of the Obafemi Awolowo University, Ile-Ife (7.551N, 4.561E). One of the primary objectives of NIMEX is to determine the surface energy balance of the humid tropical area of south-western Nigeria (Jegede et al., 2004). The other two stations, Ibadan and Akure, started operation in February 2006. Unfortunately, shortly after the simultaneous start of the experiment from all three stations in February 2006, the Akure and Ile-Ife stations developed technical problem that could not be resolved before the start of the eclipse of 29 March, 2006. This would have enabled us to compare our results from Ibadan with those from these stations. The Ibadan site is located inside the University of Ibadan, about 145km from the Gulf of Guinea Coast. The vegetation is characterized as a fallow bush-land of 0.5m canopy height. This canopy height was further reduced to bare surface and main- tained as such throughout the period of this special observation. The climate in this region is tropical with dry winter season and wet summer season according to Köppen (Essenwanger, 2001). It is characterized by low clouds, mainly cumulonimbus and stratocumulus. The experimental site is comprised of an area of about three and half hectares of land near the Faculty of Technology. The meteorological parameters measured and the instrumentation used is listed in Table 2. We set a high value for the quality of the selected instruments to obtain a reliable data set. Data acquisition and reduction was realized using CR 10X data logger from Campbell Scientific and PCs using programmes developed at the Obafemi Awolowo University, Ile-Ife and the University of Bayreuth, Germany (Mauder et al., 2007). The data were recorded daily and simple visual quality tests were performed (Foken, 2003). Nigeria is one hour ahead of GMT. 3. Climatology of the region Nigeria is located in the tropics between latitude 41N and 141N and longitude 31E and 151E in West Africa. Ibadan lies to the south-western part of the country (Fig. 1), and thus experiences a tropical weather of wet and dry climate (Hastenrath, 1991). The climate is influenced by two air masses—the moist southerly monsoon and the dry northerly winds blowing from the Azores of the subtropical high pressure system across the Sahara Desert. The pulsating boundary zone between the two wind regimes of contrasting thermodynamic properties which meet at the ITCZ is typical of the climate in tropical West Africa. The monsoon is usually linked to the southerly winds and the advection of moist marine air masses from the Gulf of Guinea into West Africa (Mauder et al., 2007). The year is roughly divided into wet or rainy season (April–October) and dry season (November–March). These seasons occur in association with the meridional movement of the ITCZ (sometimes called Inter Tropical Discontinuity, ITD) line across West Africa (Adedokun, 1978). The ITCZ determines the amount, seasonal distribution, type of rainfall and length of the wet season at any place in Nigeria. In any given year, there will be modest differences in the position and activity along the ITCZ, depending on the character of the season. Relative humidity is usually greater than 87% in Ibadan during the wet season due to the south-westerlies that are prevalent during this period. This warm and moist flow is associated with convective-type clouds and water vapour which are the most important attenuators of solar radiation. The dry season is determined by the cold, dry and dusty northeasterly winds blowing from the Sahara desert into West Africa. These northeasterly trade winds are locally called harmat- tan. During the dry season, the harmattan carry loose sand dust particles (fine silt/clayey) and other anthropogenic and atmo- spheric aerosols that are later deposited over the southern part of Nigeria and even extending up to the Gulf of Guinea (Adedokun et al., 1989). The dust rises to heights of between 2440 and 3660m and remains in the air for about 70% of the dry season period (Harris, 1971), thereby reducing visibility to less than 1km. The intensity and duration of the harmarttan depends on the strength and direction of the northeasterly winds and the position of the ITCZ. ARTICLE IN PRESS Table 2 The list of equipment deployed during NIMEX experiment and the special observation on 29 March, 2006. Parameter Device and model Manufacturers Accuracy Wind speed Cup anemometer A101ML/ A100L2 Vector instruments Dist. const. 2.3m Wind direction Wind vane W200P Vector instruments Dist. const. 2.3m Air temperature (wet and dry bulb) Frankenberger Theodor Friedrichs 70.05 1C Psychrometer Soil temperature PT-100Q Campbell scientific 71 1C Thermistor Thermocouple Soil heat flux Heat flux plate HFP01 Hukseflux �50mV/ Wm�2 HP3/CN3 Middleton �13mV/ Wm�2 Soil moisture Water content reflectometer CS615 and CS616 Campbell scientific 73% of water content Global radiation Pyranometer CM121 Kipp & Zonen 23.94mV/ Wm�2 SP-LITE Kipp & Zonen 80mV/Wm�2 Net radiation Net radiometer (REBS) Q7 Campbell scientific +9.6/ �11.9mV/ Wm�2 NR-LITE Kipp & Zonen CNR-1 Kipp & Zonen 13.9mV/ Wm�2 Rainfall amount Rainguage ARG100 Campbell scientific 0.203mm/ TIP Air pressure Capacitive barometer Ammonit 1hPa Data acquisition Data logger CR10X Campbell scientific Not applicable E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–1253 1247 UNIV ERSIT Y O F IB ADAN L IB RARY In the year 2006, the harmattan in Ibadan was very mild and came intermittently. During the eclipse of 29 March, 2006, there was no harmattan. The partial cloudy sky hours before the eclipse gave way to a clear sky 30min before the eclipse. Just before the commencement of the eclipse, there was a wind gust believed to be the ‘‘eclipse wind’’. Few unstable cumulus clouds emerged but did not obstruct visual observation of the eclipse. There were no thunderstorms or showers during the eclipse but showers passed over the station a day preceding the eclipse day in the afternoon. The wind velocity was almost zero during the eclipse particularly during totality. The detailed discussions of the results are now presented parameter-by-parameter. 4. Temperature The impact of solar eclipse on temperature has been widely reported in the literatures (Anderson, 1999; Winkler et al., 2001; Fabian et al., 2001; Foken et al., 2001; Ahrens et al., 2001; Aplin and Harrison, 2003; Kolarž et al., 2005; Founda et al., 2007). A compilation of the measured changes in air temperature at different heights above the ground during past eclipse events has been given by Anderson (1999). According to Anderson, the cooling starts when the Sun is about half-covered, with air temperature reaching its minimum value less than half an hour after mid-eclipse when the Sun’s limb has begun to reappear on the west side of the Moon. The pattern and precise amount of the decline in air temperature, however, vary from one location to the other. It is unique to each location depending on the time of the day, the local climate, site, surrounding vegetation, exposure to the sky and wind (Ahrens et al., 2001). During an eclipse, a change in the radiative heating or cooling of the atmosphere is first felt in the atmospheric surface layer where turbulent processes dom- inate in the mass, energy and momentum transport (Ahrens et al., 2001; Gerasopoulos et al., 2007). The rapid darkening during an eclipse does not allow cooling at the same rate as during sunset and night (Winkler et al., 2001).The solar flux first rapidly decreases, causing cooling of the atmosphere at all heights (Gerasopoulos et al., 2007). The decrease in surface temperature reduces the superadiabatic lapse rate near the surface and induces net radiation cooling throughout the troposphere within eclipse shadows (Eckermann et al., 2007). This result in the observed ARTICLE IN PRESS Time (Hours) 0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 S u n s e t S u n r is e E c lip s e T e m p e ra tu re d if fe re n c e 1 2 -1 m i n ° C Time (hours) 24 26 28 30 32 34 36 IVI Total Eclipse Td(6m) Td(12m) Td(1m) T e m p e ra tu re ( ° C ) 2 6 10 12 14 16 18 20 22 244 8 0 2 6 10 12 14 16 18 20 22 244 8 Fig. 2. (a) Air temperature variation at the 15m mast at Ibadan during the eclipse of 29 March, 2006. (b) Time variation of air temperature difference T12–T1m at the 15m mast during the eclipse of 29 March, 2006. E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–12531248 UNIV ERSIT Y O F IB ADAN L IB RARY differences in temperature as a function of height during eclipses as shown in Fig. 2a and many others in the literature (e.g. Eaton et al., 1997; Ahrens et al., 2001; Founda et al., 2007). Fig. 2a is the time variation of the temperature measured at Ibadan during the total solar eclipse of 29 March, 2006. The time profile of the temperature gradient between 12 and 1m (T12–T1) is shown in Fig. 2b. The effect of the high convective clouds present in the morning of the solar eclipse day can be clearly seen. During this time, the lapse rate in the air is much less stable than during the eclipse. This observation is similar to that of Winkler et al. (2001). The presence of buildings (the nearest building is at least 100m away) within the vicinity of the measurement site might have influenced the wind and temperature profiles especially taking into account the height of our mast (15m). If the mast were to be higher than 15m, say up 50m or more, it would have given us a good profile measurement of these meteorological parameters and a very good knowledge of boundary layer of this region. It is, therefore, expected that under clear undisturbed conditions the temperature at the lower levels will be lower. In fact, measurements from two undisturbed days gave 0.5 1C lower. The amplitude of the temperature change ranged from 0.8 to 1.6 1C depending on the height of measure- ment. The temperature dropped by about 1.6, 1.0 and 0.8 1C at 1, 6 and 12m, respectively, during the eclipse event. This is somewhat lower than that reported by Founda et al. (2007) who reported temperature amplitude range between 1.6 and 3.9 1C during the same eclipse event in Greece. Tzanis et al. (2007) and Economou et al. (2008) have reported temperature drops of 0.7 and 2.2 1C, respectively, while Gerasopoulos et al. (2007) reported tempera- ture drops of about 2.3 1C at the southern stations, 2.7 and 3.9 1C at the central and northern stations in Greece, respectively, during the sameMarch 2006 eclipse. These changes in temperature drops were attributed to the surrounding environment and local conditions rather than on the obscuration percentage (Founda et al., 2007). Foken et al. (2001) has reported a temperature decrease of about 1.5 1C and 2.5 1C at 6.0m height from two stations in Germany during the total solar eclipse of 11 August, 1999. Fabian et al. (2001) observed a decrease in air temperature by about 2 1C during the same solar eclipse. An approximate value of 2–3 1C at 1.5m above the ground has been widely reported in the literature (Anderson, 1999). Temperature measurement at 1m by Aplin and Harrison (2003) indicates minimum temperature occurred before totality. It fell to about 15.1 1C during and after totality for 10min after the third contact. Ahrens et al. (2001) reported that air temperature reached its minimum value about 5min after mid-eclipse. The maximum temperature fall ranged between 2.1 and 1.7 1C due to local factors coupled with the energy balance governing cloudiness. Founda et al. (2007) reported a drop in surface temperature in Greece ranging from 2.3 and 3.9 1C. The time lag between maximum eclipse and the occurrence of minimum temperature vary. For example, Winkler et al. (2001) and Aplin and Harrison (2003) reported a time lag of about 10–15min between the maximum eclipse and temperature minimum, while Ahrens et al. (2001) and Founda et al. (2007) observed 5 and 12–14min time lag, respectively. 5. Wind The eclipse wind, described as a wind burst before or after an eclipse (Eaton et al., 1997; Winkler et al., 2001), is rarely observed by most observers during solar eclipse. The existence of this ‘legendry’ phenomenon is still a subject of debate among many workers. While early observers attribute the eclipse wind to the flow of a cold-front in the penumbra (Aplin and Harrison, 2003), Anderson (1999) and Winkler et al. (2001) attributed it to eclipse gravity waves formed by a strong cooling in the upper strato- sphere and/or an enhanced wind chilled effect. Winkler et al. (2001) further argued that factors such as cooling rate, inversion strength and height, pressure gradient and obstacles could induce strong wind shear and turbulent mixing, hence eclipse wind. Fig. 3 shows a time variation of the profile of wind speed and direction at Ibadan during the total solar eclipse of 29 March, 2006. The morning of the eclipse day was characterized by low clouds which later disappear before the commencement of the eclipse. The EWwind speed dropped to below 0.5m/s by 07.00(LT) followed by a continuous increase in wind speed up to 09.19(LT), lasting for 2 h 19min. This we believed to be wind gust induced by the total solar eclipse. Thereafter, the wind speed continued to drop after the first contact reaching a minimum by 10.39(LT). The profile of wind speed before, during and after totality at different heights from our tower is presented in Table 3. We note that wind velocity is generally low (not exceeding 5.0m/s) in Ibadan during dry season. The increase in wind speed continued for about 52min, attaining a maximum at about 09.21(LT). Thereafter, it starts to decrease reaching its minimum value during totality. This ARTICLE IN PRESS 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Time (Hours) W in d s p e e d ( m /s ) 1m 3m 6m 12m 20 40 60 80 100 120 140 W in d d ir e c ti o n ( d e g ) Wind direction 2 4 6 8 10 12 14 16 18 20 22 24 Fig. 3. Wind speed and direction during the eclipse of 29 March, 2006. The vertical lines show the beginning and end of the eclipse and doted line shows totality of the eclipse. E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–1253 1249 UNIV ERSIT Y O F IB ADAN L IB RARY abrupt change in wind speed without much change in wind direction is consistent with other observers (Dolas et al., 2002; Stoev et al., 2005). The change in wind direction follows the motion of the shadow during totality. The mean wind speed at Ibadan is determined by both synoptic and orographic local wind circulations. Our readings indicate an increase in surface atmospheric pressure during the eclipse event. As shown in Fig. 4, the pressure only starts to decrease 1h 3min after the totality and for the rest of the day. This overall trend may be a synoptic change normally associated with frontal systems since the pressure continued to drop for the rest of the day. Unlike the readings of Aplin and Harrison (2003) where the pressure continued to decrease throughout totality, the pressure at Ibadan continued to increase reaching a maximum value of 1317.01hPa about 1h 3min after totality. The pressure continued to decrease thereafter reaching its lowest value of 1310.33hPa on this day around 16.07(LT). We also note that the pressure on the total solar eclipse day of 29 March, 2006 was generally higher than normal by a value of 8.01hPa. There was a delay in reaching its minimum value by about 1h 27min. On normal days, maximum pressure was 1313.00hPa and minimum pressure was 1309.00hPa. Thus, there is difference in maximum and minimum pressure of 4.01hPa and 1.33hPa, respectively. These values compare well with the measurements of Founda et al. (2007) but higher than that reported by Eckermann et al. (2007) and Economou et al. (2008) who reported a reduction of 0.7 hPa in atmospheric pressure for the same eclipse period. However, Kolarž et al. (2005) could not find any increase or decrease in pressure during the solar eclipse of 11 August, 1999. The observed reduction in pressure is as a result of the nonuniform cooling rate caused by the rapid darkening during the eclipse which reduces the superadiabatic lapse rate near the surface (Winkler et al., 2001; Eckermann et al., 2007). Pressure imbalaces then result from the rapid cooling of the atmosphere caused by the penumbra travelling at supersonic speeds (Aplin and Harrison, 2003). Other observers indicate a deceleration of the mean wind speed during a solar eclipse (Fernández et al., 1993, 1996; Dolas et al., 2002; Kirshnan et al., 2004; Stoev et al., 2005). These workers attributed their observations to the combined effect of the decrease of thermal gradient and stabilization of surface layer following the drop of temperature and the suppression of turbulent processes (Founda et al., 2007). This variability of mean wind speed was however, not observed by Eaton et al. (1997) during the partial eclipse of 10 May, 1994. However, the authors detected a decrease in the variance of the three wind speed components. Changes in turbulent and spectral characteristics of wind speed induced by an eclipse in India during the eclipse of 11 August, 1999, were detected by Kirshnan et al. (2004). It should be noted that orographic winds can be noticed on a local scale if synoptic situations allow (Anderson, 1999; Founda et al., 2007). Ahrens et al. (2001) have reported a decrease in horizontal wind velocity from 2.3 to 0.4m/s during the total solar eclipse of 11 August, 1999, while Winkler et al. (2001) reported a continuous increase in wind speed from eclipse maximum about 60% recovery of the Sun. Wind speed dropped from 2.02 to 0.50m/s at 1m height; 2.40 to 0.77m/s at 3m; 2.7 to 0.93m/s at 6m and 3.05 to 1.14m/s at 12m, respectively, at Ibadan during the eclipse. Measurements of meteorological parameters in Greece by Founda et al. (2007) during the total solar eclipse of 29 March, 2006 showed variability in wind speed and direction from one station to the other. Some stations showed an abrupt change in wind speed and direction and others did not. For example, Gerasopoulos et al. (2007) reported a decrease of the order of 2m/ s in wind speed without any simultaneous change in direction. This decrease was related to the cooling and stabilization of the atmospheric boundary layer (Amiridis et al., 2007). Foken et al. (2001) observed significant effects of the total solar eclipse of 11 August, 1999 on mean wind speed. They also observed a time shift of about 30min between the minimum irradiation and minimum wind velocity. We observed a time shift of 26min between minimum global radiation and minimum wind speed in our station. Foken et al. (2001) attribute this effect to a decoupling of the lower part of the surface layer on a local scale due to ARTICLE IN PRESS Table 3 Wind profile during the total solar eclipse of 29 March, 2006 at Ibadan. Height (m) Before Wind speed (m/s) 7.00(LT) 9.24(LT) Totality After 10.40(LT) 11.49(LT) 1 0.29 2.02 0.48 1.61 3 0.44 2.39 0.75 1.87 6 0.59 2.67 0.93 2.07 12 0.72 3.06 1.13 2.34 The effect of the eclipse wind is clearly shown here before totality. 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 IVI Time (hours) W in d s p e e d ( m /s ) 1m 3m 6m 12m 1310 1312 1314 1316 1318 Totality Day 88 P re s s u re ( h P a ) Pressure (hPa) 2 4 6 8 10 12 14 16 18 20 22 24 26 Fig. 4. Wind speed and pressure during the total solar eclipse of 29 March, 2006 at Ibadan. E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–12531250 UNIV ERSIT Y O F IB ADAN L IB RARY stabilization and/or change of pressure gradients in mesoscale due to reduced heating of the surface. 6. Radiation The total solar eclipse on 29 March, 2006 provides a unique opportunity to determine the effect of the eclipse on surface radiation fluxes for the first time in this sub-Saharan region. Fig. 5 presents the observed time variation of global solar radiation, Rg, net radiation, Rn, reaching the Earth’s surface and soil heat flux, Shf, at Ibadan during the total solar eclipse event. The diurnal pattern of these parameters is observed to be affected by the eclipse. By 09.33(LT) the global radiation had already reached 504.71W/m2 before falling to about 25.44W/m2 at totality. In contrast to experiments during partial solar eclipses (Eaton et al., 1997) and the total solar eclipse of 11 August, 1999 (Ahrens et al., 2001), the net radiation was negative during totality similar to measurement in Germany by Foken et al. (2001) during the total solar eclipse of 11 August, 1999. The net radiation dropped from 354.27 to �3.56W/m2 during totality. The course of global radiation and net radiation, however, ran parallel to each other similar to the observations of Ahrens et al. (2001). A comparison of the global radiation and air temperature (all measured at 1m above the ground) is shown in Fig. 5b. There is a time lag of about 9min between the global radiation and air temperature minima during totality. Foken et al. (2001) measured and compared extraterrestrial radiation and global radiation during the total solar eclipse of 11 August, 1999 in Germany. They reported a time shift of 25min during totality, attributing the short time when global radiation was higher than extra terrestrial radiation to reflection from the clouds. The large observed time shift has been variously explained to be caused by a decoupling of the lower part of the surface layer on local scales due to stabilization and/or change of pressure gradients on a meso-scale range due to a reduced heating of the surface (Handorf et al., 1999; Foken et al., 2001). Aplin and Harrison (2003) reported a significant influence of the eclipse on global radiation, net radiation and ground heat flux. The ground heat flux reached minimum value 31min after totality similar to the flux observa- tion of Foken et al. (2001). The effect of the total solar eclipse of 29 March, 2006 on global radiation, net radiation and soil heat flux at Ibadan was significantly high and similar to the observations of Founda et al. (2007). The percentage of reduction of these parameters was proportional to the obscuration percentage. ARTICLE IN PRESS 0 0 200 400 600 800 1000 IVI Totality Shf Rn Rg F lu x ( W m -2 ) Time (hours) 24 26 28 30 32 34 36 Time (Hours) A ir t e m p e ra tu re a t 1 m h e ig h t (° C ) 0 200 400 600 800 1000 IVI T o ta lit y Tair (1m) Rg G lo b a l ra d ia ti o n , R g , (W /m 2 ) 2 64 8 10 12 14 16 18 20 22 24 26 0 2 64 8 10 12 14 16 18 20 22 24 26 Fig. 5. (a) Surface energy fluxes at Ibadan during the total solar eclipse of 29 March, 2006. (b) Comparison of global radiation and air temperature (1m above the ground surface) at Ibadan during the total solar eclipse of 29 March, 2006. E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–1253 1251 UNIV ERSIT Y O F IB ADAN L IB RARY Soil temperature was measured at 5, 10 and 30 cm during the event. As shown in Fig. 6, there was a decrease in soil temperature of about 0.5 1C at 5 cm depth. Fabian et al. (2001) and Foken et al. (2001) had reported a temperature decrease of 0.5 and 0.2 1C, respectively, for soil temperatures measured at 2 cm level in Germany during the total solar eclipse of 11 August, 1999. Just like the measurement of Kirshnan et al. (2004), at 5 cm level, the temperature nearly followed the air temperature at 1 and 6m levels. The air temperature at 1m reached a minimum value 26.30min before soil temperature at 5 cm during maximum eclipse. The soil temperature remains approximately constant thereafter from 10.50 to 11.00(LT). At 10 cm, the temperature also remained constant from 10.24 to about 11.14(LT). Like other earlier workers (Foken et al., 2001; Kirshnan et al., 2004; Fabian et al., 2001), the eclipse did not have any significant effect on the soil temperature at 30 cm level. The soil moisture was mostly affected by the rain that fell a day preceding the eclipse. 7. Conclusion The occasion of the 29 March, 2006 eclipse, visible over Nigeria and other parts of West and North Africa, has provided the opportunity for micrometeorological measurements to be carried out for the first time in Nigeria. The meteorological parameters measured during the eclipse period include air temperature, global and net radiation, atmospheric pressure, soil temperature, moisture, heat flux and rainfall. The micrometeorological observations made during the total solar eclipse of 29 March, 2006 at Ibadan, Nigeria, showed that all the meteorological variables were strongly affected by the eclipse event. Global radiation and net radiation were significantly reduced during the eclipse period. The reduction in global and net radiation was proportional to the Sun’s percentage obscura- tion. The reduction in air temperature ranged from 0.8 to 1.6 1C depending on the height of measurement. These results are lower than those over Greece (Founda et al., 2007; Gerasopoulos et al., 2007; Tzanis et al., 2007; Economou et al., 2008) during the same eclipse event but compares well with that of other eclipses (Ahrens et al., 2001; Foken et al., 2001). A wind gust, believed to be ‘‘eclipse wind’’, was observed just before the first contact of the eclipse. This was followed by a significant decrease in surface wind speed as the eclipse progressed towards maximum phase. Unlike the observation of other workers (Aplin and Harrison, 2003), the pressure over Nigeria continued to increase throughout the eclipse period. This is because of the subtropical high pressure systems blowing over the Sahara Desert at this period of the year. This system forces the ITCZ to the extreme southern part of the country up to the Gulf of Guinea, thereby resulting in little or no rainfall throughout the country (the dry season). There was also a noticeable drop in soil temperature at 5 and 10 cm, respectively. No noticeable change in soil temperature at 30 cm. Acknowledgements We want to thank the International Science Programmes, University of Uppsala, Sweden for the equipment and financial support given to us for this work. This work was also partly supported by the Senate Research Grant of the University of Ibadan. References Adedokun, J.A., 1978. West African precipitation and dominant atmospheric mechanisms. Arch. Meteorol. Geophys. Bioclimatol. Ser. A 27, 289–310. Anderson, J., 1999. Meteorological changes during a solar eclipse. Weather 54 (7), 207–215. Anderson, R.C., Keefer, D.R., Myers, O.E., 1972. Atmospheric pressure and temperature changes during the 7 March, 1970 solar eclipse. J. Atmos. Sci. 29, 583–587. Ahrens, D., Moses, G.I., Lutz, J., Andreas, M., Helmut, M., 2001. Impacts of the solar eclipse of 11 August, 1999 on routinely recorded meteorological and air quality data in South-West Germany. Meteorol. Z. 10 (3), 215–223. Altadill, D., Sole, J.G., Apostolov, E.M., 2001. Vertical structure of a gravity wave like oscillation in the ionosphere generated by the solar eclipse of August 11, 1999. J. Geophys. Res. 106 (A10), 21419–21428. Amiridis, V., Melas, D., Balis, D.S., Papayannis, A., Founda, D., Katragkon, E., Giannakaki, E., Mamouri, R.E., Gerasopoulos, E., Zerefos, C., 2007. Aerosol lider observations and model calculations of the planetary boundary layer evolution over Greece during the March 2006 total solar eclipse. Atmos. Chem. Phys. Discuss. 7, 13537–13560. Anderson, R.C., Keefer, D.R., 1975. Observations of temperature and pressure changes during the 30th June, 1973 Solar eclipse. J. Appl. Meteorol. 32, 229–231. ARTICLE IN PRESS 0 26 28 30 32 34 36 38 IVI 5cm 10cm 30cm S o il te m p e ra tu re ( ° C ) Time (Hours) 2 4 6 8 10 12 14 16 18 20 22 24 Fig. 6. Soil temperature during the total solar eclipse of 29 March, 2006. Solid vertical lines show the beginning and end of the eclipse. The doted vertical line shows the time of totality. E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–12531252 UNIV ERSIT Y O F IB ADAN L IB RARY Anfossi, D., Schayes, G., Degrazia, G., Goulart, A., 2004. Atmospheric turbulence decay during the solar total eclipse of 11 August, 1999. Boundary-Layer Meteorol. 111, 301–311. Aplin, K.L., Harrison, R.G., 2003. Meteorological effects of the eclipse of 11 August, 1999 in cloudy and clear conditions. Proc. R. Soc. London A459, 353–371. Aushev, V.M., Lyahov, V.V., López-González, M.J., Shepherd, M.G., Dryn, E.A., 2008. Solar eclipse of the 29 March 2006: results of the optical measurements by MORTI over Almaty (43.031N, 76.581). J. Atmos. Sol.Terr. Phys. (doi:1016/ j.jastp.2008.01.018). Baran, L.W., Ephishov, I.I., Shagimuratov, I.I., Ivanov, V.P., Lagovsky, A.F., 2003. The response of the ionospheric total electron content to the solar eclipse on 11 August, 1999. Adv Space Res. 31 (4), 989–994. Bojkov, R.D., 1968. The ozone variations during the solar eclipse of 20 May, 1966. Tellus 20, 417–421. Chakrabarty, D.K., Shah, N.C., Pandya, K.V., 1997. Fluctuations in ozone column over Ahmenabad during the solar eclipse of 24 October, 1995. Geophys. Res. Lett. 24, 3001–3003. Chimonas, G., 1971. Atmospheric gravity waves induced by a solar eclipse. J. Geophys. Res. 76, 7003–7005. Chudzyński, W., Czyżewski, A., Ernst, K., Pietruczuk, A., Skubiszak, W., Stacewicz, T., Stelmaszczyk, K., Szymański, A., Sówka, I., Zwoździak, A., Zwoździak, J., 2001. Observation of ozone concentration during the solar eclipse. Atmos. Res. 57 (1), 43–49. Davies, K., 1982. Atmospheric gravity waves induced by a solar eclipse—a review. Proc. Indian Natl. Acad. 48a (Suppl. 3), 342–355. Dolas, P.M., Ramchandra, R., Sen Gupta, K., Patil, S.M., Jadhav, P.N., 2002. Atmospheric surface-layer processes during the total solar eclipse of 11 August, 1999. Boundary-Layer Meteorol. 104, 445–461. Eaton, F.D., Hines, J.R., Hatch, W.H., Cionco, R.M., Byers, J., Garvey, D., Miller, D.R., 1997. Solar eclipse effects observed in the planetary boundary layer over a desert. Boundary-Layer Meteorol. 83, 331–346. Economou, G., Christou, E.D., Giannakourou, A., Gerasopoulos, E., Georgopoulo, D., Kotoulas, V., Lyra, D., Tsakalis, N., Tziortzou, M., Vahamidis, P., Papathanassiou, E., Karamanos, A., 2008. Eclipse effects on field crops and marine zooplankton: the 29 March, 2006 total solar eclipse. Atmos. Chem. Phys. Discuss. 8, 1291–1320. Eckermann, S.D., Broutman, D., Stollberg, M.T., Ma, J., McCormack, J.P., Hogan, T.F., 2007. Atmospheric effects of the total solar eclipse of 4 December, 2002 simulated with a high-altitude global model. J. Geophys. Res. 112, D14105. Espenak, F., Anderson, J., 2006. NASA Technical Publication ‘‘Total Solar Eclipse of 2006 March 29’’ (NASA/TP-2004-212762). Essenwanger, O.M., 2001. Classification of Climates. Elsevier, Amsterdam, 113pp. Fabian, P., Martin, W., Bernhard, R., Heinrich, R., Andreas, S., Peter, K., Hans, S., Harold, B., Foken, T., Bodo, W., Karl-Heinz, H., Rainer, M., Thomas, K., 2001. The BAYSOFI campaign—measurements carried out during the total solar eclipse of August 11, 1999. Meteorol. Z. 10 (3), 165–170. Fernández, W., Castro, V., Hidalgo, H., 1993. Air temperature and wind changes in Costa Rica during the total solar eclipse of July 11, 1991. Earth, Moon and Planets 63, 133–147. Fernández, W., Hidalgo, H., Coronel, G., Morales, E., 1996. Changes in meteor- ological variables in Coronel Oviedo, Paraguay, during the total eclipse of 3 November 1994. Earth, Moon and Planets 74, 49–59. Foken, T., Bodo, W., Otto, K., Jörg, G., Martin, W., Tamás, Weidinger, 2001. Micrometeorological measurements during the total solar eclipse of August 11, 1999. Meteorol. Z. 10 (3), 171–178. Foken, T., 2003. Angewandte Meteorologie. Mikrometeorologische Methoden. Springer, Heidelberg, 289pp. Founda, D., Melas, D., Lykoudis, S., Lisarsidis, I., Gerasopoulos, E., Kouvarakis, G., Petrakis, M., Zerefos, C., 2007. The effect of the total solar eclipse of 29 March 2006 on meteorological variables in Greece. Atmos. Chem. Phys. Discuss. 7, 10631–10667. Gerasopoulos, E., Zerefos, C.S., Tsagouri, I., Founda, D., Amidiris, V., Bais, A.F., Belehaki, A., Christou, N., Economou, G., Kanakidou, M., Karamanos, A., Petrakis, M., Zanis, P., 2007. The total solar eclipse of March 2006: overview. Atmos. Chem. Phys. Discuss. 7, 17663–17704. Handorf, D., Foken, T., Kottmeier, C., 1999. The stable atmospheric boundary layer over an Antartic ice sheet. Boundary-Layer Meteorol. 91, 165–186. Horvath, J.J., Thean, J.S., 1972. Response of the neutral particle upper atmosphere to the solar eclipse of 7 March, 1970. J. Atmos. Terr. Phys. 34, 593–599. Jakobi, C., Kürschner, D., 2000. Ergebniss ionosphärischer messungen am observatorium collm während der totalen sonnenfinsternis vom 11.8. 1999. Wiss.Mitt. aus dem Meteorol. Inst. Der Univ. Leipzig 17, 88–94. Jegede, O.O., Mauder, M., okogbue, E.C., Foken, T., Balogun, E.E., Adedokun, J.A., Oladiran, E.O., Omotosho, J.A., Balogun, A.A., Oladosu, O.R., Sunmonu, L.A., Ayoola, M.A., Aregbesola, T.O., Ogolo, E.O., Nymphas, E.F., Adeniyi, M.O., Olatona, G.I., Ladipo, K.O., Ohamobi, S.I., Gbobaniyi, E.O., Akinlade, G.O., 2004. The Nigerian micrometeorological experiment (NIMEX-1): an overview. Ife J. Sci. 6, 191–202. Jones, B.W., 1999. A search for atmospheric pressure waves from the total solar eclipse of 9 March, 1997. J. Atmos. Sol. Terr. Phys. 61, 1017–1024. Kolarž, P., Šekarić, J., Marinković, B.P., Filipović, D.M., 2005. Correlation between some of the meteorological parameters measured during the partial solar eclipse, 11 August, 1999. J. Atmos. Sol. Terr. Phys. 67, 1357–1364. Kirshnan, P., Kunhikrishnan, P.K., Muraleedharan Nair, S., Ravindran, S., Ramachan- dran, R., Subrahamanyan, D.B., Venkata Ramana, M., 2004. Observations of the atmospheric surface layer parameters over a semi arid region during the solar eclipse of 11 August, 1999. Proc. Indian Acad. Sci. (Earth Planet Sci.) 113, 353–363. Krumov, A.H., Krezhova, D.D., 2008. Imaging of the total solar eclipse on March 29, 2006. J. Atmos. Sol. Terr. Phys. 70, 407–413. Littman, M., Willcox, K., 1991. Totality: Eclipses of the Sun. University of Hawaii Press, 224pp. Mauder, M., Jegede, O.O., Okogbue, E.C., Wimmer, F., Foken, T., 2007. Surface energy balance measurements at a tropical site in West Africa during the transition from dry to wet season. J. Theor. Appl. Climatol. 89, 171–183. Mitchell, S.A., 1951. Eclipses of the Sun, Fifth ed. Colombia University Press, New York, 482pp. Segal, M., Turner, R.W., Prusa, J., Bitzer, R.J., Finley, S.V., 1996. Solar eclipse effect on shelter air temperature. Bull. Am. Meteorol. Soc. 77 (1), 89–99. Stoev, A., Stoeva, P., Valev, D., Kishkinova, N., Tasheva, T., 2005. Dynamics of the microclimatic parameters of the ground atmospheric layer during the total solar eclipse on August 11, 1999. Geophys. Res. Abstr. 7, 10209. Seykora, E.J., Bhatnager, A., Jain, R.M., Streete, J.L., 1985. Evidence of gravity waves produced during the 11 June, 1983 total solar eclipse. Nature 313, 124–125. Singh, L., Tyagi, T.R., Somayajuh, Y.V., Vijayakumar, P.N., Dabas, R.S., Loganadham, B., Ramakirshna, S., Rama Rao, P.V.S., Dasgupta, A., Naneeth, G., Klobuchar, J.A., Hartmann, G.K., 1989. A multi-station satellite radio beacon study of ionospheric variations during solar eclipses. J. Atmos. Sol. Terr. Phys. 51, 271–278. Stoeva, P., Stoev, A., Kuzin, S., Shopov, Y., Kiskinova, N., Stoyanov, N., Perstsov, A., 2008. J. Atmos. Sol. Terr. Phys. 70, 414–419. Sza"owski, K., 2002. The effect of the solar eclipse on air temperature near the ground. J. Atmos. Sol. Terr. Phys. 64, 1589–1600. Tzanis, C., Varotsos, C., Viras, L., 2007. Impacts of solar eclipse of 29 March, 2006 on the surface ozone and nitrogen dioxide concentrations at Athens, Greece. Atmos. Chem. Phys. Discuss. 7, 14331–14349. Winkler, P., Uwe, Kaminski, Ulf, Köhler, Johann, Riedl, Hans, S., Doris, Anwender, 2001. Development of meteorological parameters and total ozone during the total solar eclipse of August 11, 1999. Meteorol. Z. 10 (3), 193–199. Zanis, P., Katragkou, E., Kanakidou, M., Psilolou, B.E., Karathanasis, S., Vrekoussis, M., Gerasopoulos, E., Lysaridis, I., Markakis, K., Poupkou, A., Amiridis, V., Melas, D., Mihalopoulos, N., Zerefos, C.S., 2007. Effects on surface atmospheric photo- oxidants over Greece during the total solar eclipse of 29 March, 2006. Atmos. Chem. Phys. Discuss. 7, 11399–11428. Zerefos, C.S., Balis, D.S., Meleti, C., Bais, A.F., Tourpali, K., Vanicek, K., Cappenlanni, F., Kaminski, U., Tiziano, C., Stubi, R., Formenti, P., Andreae, A., 2000. Changes in environmental parameters during the solar eclipse of August 11, 1999 over Europe, effects on surface UV 20 solar irradiance and total ozone. J. Geophys. Res. 105 (D21), 26463–26473. Zerefos, C.S., Balis, D.S., Zanis, P., Meleti, C., Bais, A.F., Tourpali, K., Melas, D., Ziomas, I., Galani, E., Kourtidis, K., Papayannis, A., Gogosheva, Z., 2001. Changes in surface UV solar irradiance and ozone over the Balkans during the eclipse of 11 August, 1999. Adv. Space Res. 27 (12), 1955–1963. Zerefos, C.S., Gerasopoulos, E., Tsagouri, I., Psilaglon, B., Belehaki, A., Herekakis, T., Bais, A., Kazadzis, S., Eleftheratos, C., Kalivitis, N., Mihalopoulos, N., 2007. Evidence gravity waves into the atmosphere during the March 2006 total solar eclipse. Atmos. Chem. Phys. Discuss. 7, 7603–7624. Zirker, J.B., 1984. Total Eclipses of the Sun. Van Nostrand Reinhold, New York, 228pp. ARTICLE IN PRESS E.F. Nymphas et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1245–1253 1253 UNIV ERSIT Y O F IB ADAN L IB RARY Micrometeorological measurements in Nigeria during the total solar eclipse of 29 March, 2006 Introduction Measurement site and instrumentation Climatology of the region Temperature Wind Radiation Conclusion Acknowledgements References