1. Welcome Ultraviolet (UV) Radiation and its Physical Modulating Factors in Africa Based on TOMS and NOAA Polar Orbiting Satellites Data

2. Introduction What is solar ultraviolet radiation? What is solar ultraviolet radiation? Ultraviolet radiation is part of the solar electromagnetic radiation spectrum from about 400 nm to 100 nm (where the visible ray range ends) Ultraviolet radiation is part of the solar electromagnetic radiation spectrum from about 400 nm to 100 nm (where the visible ray range ends) Ultraviolet radiation is part of the solar electromagnetic radiation spectrum from about 400 nm to 100 nm (where the visible ray range ends) Ultraviolet radiation is part of the solar electromagnetic radiation spectrum from about 400 nm to 100 nm (where the visible ray range ends) It is a little over 8% of the total solar spectrum It is a little over 8% of the total solar spectrum It is a little over 8% of the total solar spectrum It is a little over 8% of the total solar spectrum Classification: UV-A UV-A UV-A UV-B UV-B UV-B UV-C UV-C UV-C Spectral region wavelen gth % energy Infrared >700 nm 49.4 visible 4 00-700 nm 42.3 UV-A 400-315 nm 6.3 UV-B 315-280 nm 1.5 UV-C <280 nm 0.5

3. Effects of UV radiation Different types of Skin cancer (DNA damage) Different types of Skin cancer (DNA damage) Early ageing of skin Early ageing of skin Eye disease called cataract Eye disease called cataract Human immune system Human immune system Decreasing plant yield Decreasing plant yield Decrease in service time of infrastructure Decrease in service time of infrastructure Fading up of closes Fading up of closes

4. Gaps in understanding UV and the Determining Factors Very few scientific studies in Africa on isolated cases. Very few scientific studies in Africa on isolated cases. Reports say the total column ozone is intact (no depletion) in Africa. But few show the trend of ozone in Africa. Reports say the total column ozone is intact (no depletion) in Africa. But few show the trend of ozone in Africa. UV interaction with clouds is complex and no attempt has been made in Africa. UV interaction with clouds is complex and no attempt has been made in Africa.

5. Problem Statement and Contribution Having the gaps the problems are: a) Estimation of the dose of UV index (UVI) in Africa b) Quantification of the relationship of UV with ozone, aerosols and clouds in Africa c) Investigation of the vertical distribution of ozone in Africa and comparison with the higher latitudes.

6. Objectives The research s central objective is towards development and understanding modes of variability for UV radiation in Africa and establishment of its interplay with ozone, aerosols, and cloud parameters in eigenvector domain. The research s central objective is towards development and understanding modes of variability for UV radiation in Africa and establishment of its interplay with ozone, aerosols, and cloud parameters in eigenvector domain. Specific Objectives a) To quantify the UV dose in Africa b) To identify and explain the modes of variability of UV radiation, ozone, aerosols, and cloud physical parameters in Africa in space and time, c) To illustrate the seasonal variability of UV, Ozone, and aerosols in Africa, understand how UV are modulated by various physical processes and factors, d) To establish the physical mechanisms of the variation of UV in space and time

7. Absorption in the UV Absorption by ozone, oxygen and nitrogen are wavelength dependent Absorption by ozone, oxygen and nitrogen are wavelength dependent UV irradiance at surface are : - UV-A 94% -- very small absorbed - UV-A 94% -- very small absorbed - UV-B 6% -- almost all absorbed - UV-B 6% -- almost all absorbed - UV-C 0% -- all are absorbed - UV-C 0% -- all are absorbed

8. The UV absorption cross-sections :

9. UV Absorption Spectrum of Ozone: - The strongest absorption bands of O 3 is called Hartley bands (200 to 300 nm) - Weak absorption of UV by O 3 in Huggins bands (300 – 360 nm) - Very weak absorption of UV by O 3 in the visible and infrared region (440 – 1180 nm)

10. Biologically active UV radiation The dose rate is an instantaneous measure of the biologically-weighted UV irradiance Biological action spectrum Irradiance The dose rate is an instantaneous measure of the biologically- weighted UV irradiance

11. BAS Cont… Integration of the dose rate over a period of the year in units of Jm-2, dose rate = dose rate = Diurnal dependence of DNA damaging UV: Equator 40 0 60 0 Diurnal dependence of DNA-damaging dose rate on 21 June at three different latitudes (Madronich 1993a).

12. UV Dependence on Geophysical variables Surface UV (UV irradiance) affected Surface UV (UV irradiance) affected a) Scattering b) Absorption in the atmosphere c) The stability of extraterrestrial solar radiation: extraterrestrial solar spectrum results in Ozone which further results in UV extraterrestrial solar spectrum results in Ozone which further results in UV How is long term solar UV behaving? How is long term solar UV behaving? An increase of solar spectral irradiance at the 11- year solar activity cycle minimum since the Maunder minimum (year 1700) of 3.0% for wavelengths less than 300 nm and 1.3% for the band 300-400 nm An increase of solar spectral irradiance at the 11- year solar activity cycle minimum since the Maunder minimum (year 1700) of 3.0% for wavelengths less than 300 nm and 1.3% for the band 300-400 nm

13. Dependence of UV on ozone and other trace gases As ozone decreases UV rises. The ozone in any given location is a balance between three processes: in situ creation, in situ destruction, and transport in to or out of the location. How do we measure ozone? Mixing ratio (ppmv) Mixing ratio (ppmv) Number density P ozone = n KT (26) Number density P ozone = n KT (26) Partial pressure Partial pressure Dobson unit (1 DU = 10 -5 m ) Dobson unit (1 DU = 10 -5 m ) UVD Cont…

14. Ozone Circulation (Brewer Dobson Circulation) Average number density of ozone (DU per km) as measured by the Nimbus-7 Solar Backscatter ultraviolet Instrument (SBUV) plotted versus latitude and altitude, dataset from 1980-1989. The black arrows show the stratospheric Brewer – Dobson circulation.

15. UVD Cont… They attenuate UV flux through the atmosphere aerosol optical depth (AOD) and the average column value of the single scattering albedo They attenuate UV flux through the atmosphere aerosol optical depth (AOD) and the average column value of the single scattering albedo Dependence on Clouds! Dependence on Aerosols! Under overcast conditions, clouds decrease the irradiance measured at the surface Under overcast conditions, clouds decrease the irradiance measured at the surface However, enhancements of up to 25% can occur under broken cloud conditions However, enhancements of up to 25% can occur under broken cloud conditions

16. UV, aerosols and ozone data TOMS/ Nimbus 7 data (1979 to 1992) TOMS/ Nimbus 7 data (1979 to 1992) EPTOMS data (1997 to 2003) EPTOMS data (1997 to 2003) Vertical distribution of ozone data SBUV (TOMS/Nimbus 7) (1981 to 1985) SBUV (TOMS/Nimbus 7) (1981 to 1985) NOAA-11 (1999 to 2000) NOAA-11 (1999 to 2000) NOAA-16 ( 2001 to 2003) NOAA-16 ( 2001 to 2003) Clouds data Obtained from ISCCP (1984-2001) Data Types and Methods

17. DTM cont… Singular value decomposition (svd) /empirical orthogonal function (EOF)/ Principal Component analyses (PCA) Singular value decomposition (svd) /empirical orthogonal function (EOF)/ Principal Component analyses (PCA) variance analyses variance analyses Correlation and regression analyses Correlation and regression analyses Establishing physical relationship Establishing physical relationship Methods

18. The Spatial and Temporal Results of UV, AI and Ozone over Africa UV space-time mode The first few modes explain the total variability of the data. -The first spatial mode of UV ~19% of the total variability, -the second Spatial mode ~9% and so on: The first four modes alone explained The first four modes alone explained 39% Of the total variability of the 84 39% Of the total variability of the 84 modes modes Res. Cont…

19. In the JJAS 66% trend decrease (1979 to 1992) In the JJAS 66% trend decrease (1979 to 1992) In the same season 37 % trend increase (1997 to 2002) In the same season 37 % trend increase (1997 to 2002) Seasonal variability of UV in Africa

20. Aerosols space-time mode The first mode explains 28% The first mode explains 28% The second mode ~10% The second mode ~10% The third mode ~7% and The third mode ~7% and The fourth mode ~5% The fourth mode ~5% Res. Cont…

21. The aerosols temporal modes

22. The ozone spatial and temporal modes The first spatial mode ~30% The first spatial mode ~30% The second spatial mode ~17% The second spatial mode ~17% 11% the third mode 11% the third mode 5% by the fourth mode 5% by the fourth mode The first four values alone represent ~50% of the total variance in the data Res. Cont…

23. The Temproal modes of ozone

24. Vertical ozone mixing-ratio 10 years average ozone amount tropical Africa (ONDJ) Res. Cont…

25. Res. Cont… If ozone concentration is highest in the stratosphere in the period, it is also the least in the troposphere in the same period. If ozone concentration is highest in the stratosphere in the period, it is also the least in the troposphere in the same period. In general, the vertical ozone concentration shows opposite quantitative variability in the two spheres of the atmosphere. In general, the vertical ozone concentration shows opposite quantitative variability in the two spheres of the atmosphere.

26. Res. Cont… For the other cross sections ~30S and ~30N is taken and compared with the other latitudes, ~0, ~60S, ~60N, ~90S and ~90N. For the other cross sections ~30S and ~30N is taken and compared with the other latitudes, ~0, ~60S, ~60N, ~90S and ~90N. The vertical ozone concentration is relatively highest in October for 60N (9.544 ppmv), and least for 60S (8.48 ppmv). The difference is 11% lower than the peak. The vertical ozone concentration is relatively highest in October for 60N (9.544 ppmv), and least for 60S (8.48 ppmv). The difference is 11% lower than the peak.

27. Res. Cont… In November, the ozone- mixing ratio is least in values at and around 90N and 90S in the stratosphere. In November, the ozone- mixing ratio is least in values at and around 90N and 90S in the stratosphere. the greatest ozone- mixing ratio is observed for 30S and its nearest locations (because of the ozone transport from the equator to higher latitudes through Brewer-Dobson Circulation). the greatest ozone- mixing ratio is observed for 30S and its nearest locations (because of the ozone transport from the equator to higher latitudes through Brewer-Dobson Circulation). Brewer-Dobson Circulation). Brewer-Dobson Circulation).

28. Res. Cont…

29. Results and Discussion Ultraviolet Radiation in Africa Around 18N, Around 18N, UVery dose = 5500 J/m 2 At tropics high, At tropics high, At high latitudes less At high latitudes less UVI = dose rate/unit time (mW/m 2 ) x 20 m 2 /mW

30. a) Latitudinal Comparison of UV and ozone Why higher latitudes ? Why higher latitudes ? Res. Cont…

31. Ozone Circulation (Brewer Dobson Circulation) Average number density of ozone (DU per km) as measured by the Nimbus-7 Solar Backscatter ultraviolet Instrument (SBUV) plotted versus latitude and altitude, dataset from 1980-1989. The black arrows show the stratospheric Brewer – Dobson circulation.

32. Latitudinal Comparison of UV, ozone and Aerosol Index Due to the Saharan and Arabian Deserts Ozone UV

33. UV and ozone UV (O3) = -18.595 -12.233x O3 UV (O3) = -18.595 -12.233x O3 (41%)

34. b) Aerosols and UV Association only 7% of the total variability of UV over the African continent can be expressed by aerosols. only 7% of the total variability of UV over the African continent can be expressed by aerosols. UV (AI) = -4.085 – 210.140 x AI (Ts_1) – UV (AI) = -4.085 – 210.140 x AI (Ts_1) – 187.982 x AI (Ts_2) 187.982 x AI (Ts_2) – 717.297 x AI (Ts_4) – 717.297 x AI (Ts_4) where Ts (1-4) means respective time series of eigenvectors. Res. Cont…

35. The clouds, which have shown significant relationship, are as follows: All clouds- Top Temperature All clouds- Top Temperature Altocumulus Liquid clouds – Optical Thickness and top temperature Altocumulus Liquid clouds – Optical Thickness and top temperature Cirrostratus cloud – Top Pressure Cirrostratus cloud – Top Pressure Cirrus cloud – Water Path Cirrus cloud – Water Path Of 100 cloud parameters attempted to associate. Res. Cont…

36. The general model which accounts for the clouds in this UV investigation is The general model which accounts for the clouds in this UV investigation is UV = -30.293 – 11.492 x (all-cloud-temp.) – 56.791 x (altocumulus Liquid-top-opt.) – 49.453 x (altocumulus liquid – temp.) – 3.488 x (cirrostratus cloud – top - press) – 7.029 x (cirrus cloud water path) The overall contribution of clouds to the UV analysis is around 39%. The overall contribution of clouds to the UV analysis is around 39%. Res. Cont…

37. The possible range of values of UV index (UVI) obtained in Africa is between 4 and 9. The possible range of values of UV index (UVI) obtained in Africa is between 4 and 9. The overall trend of the UVery is decreasing in all of the seasons. The overall trend of the UVery is decreasing in all of the seasons. Ozone trend is on the increase in Africa. Ozone trend is on the increase in Africa. The tropical Africa vertical ozone profile show stable variability. The tropical Africa vertical ozone profile show stable variability. The 30N and 30S show relatively higher stratospheric ozone. The 30N and 30S show relatively higher stratospheric ozone. conclusion

38. UV interplayed with all cloud type and properties ( top pressure, top temperature, water path, and optical thickness) except cloud amount. UV interplayed with all cloud type and properties ( top pressure, top temperature, water path, and optical thickness) except cloud amount. Deep convective clouds does not show significant relationship with UV but are the main cloud types in tropical Africa. Deep convective clouds does not show significant relationship with UV but are the main cloud types in tropical Africa.

39. Interesting results come out from the UV and cloud relationships: Interesting results come out from the UV and cloud relationships: UV interplayed with all cloud type and properties ( top pressure, top temperature, water path, and optical thickness) except cloud amount UV interplayed with all cloud type and properties ( top pressure, top temperature, water path, and optical thickness) except cloud amount All clouds account for 39 % of the total variability of UV irradiance. All clouds account for 39 % of the total variability of UV irradiance. Deep convective clouds does not show significant relationship with UV but are the main cloud types in tropical Africa. Deep convective clouds does not show significant relationship with UV but are the main cloud types in tropical Africa. Sum. Cont….

40. Ultraviolet Radiation in Africa Clouds (39%) Ozone concentration (40%) Aerosol Index (7%)

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42. Ultraviolet radiation spectrum

43. UV Absorption Spectrum of Molecular oxygen: Schumann - Runge band: 200 – 125 nm Schumann - Runge band: 200 – 125 nm Several bands: 125 – 100 nm (e.g. Lyman- 121 nm) Several bands: 125 – 100 nm (e.g. Lyman- 121 nm) Hopfield bands: <100 nm Hopfield bands: <100 nm Hertzberg Bands: 260 – 200 nm Hertzberg Bands: 260 – 200 nm

44. BAS Cont… Seasonal and latitudinal dependence of daily dose rate (Jm-2 day-1) for DNA damage calculated for: Seasonal and latitudinal dependence of daily dose rate (Jm-2 day-1) for DNA damage calculated for: -clear skies -clear skies -using ozone -using ozone column (DU) column (DU) average (1979-1989) average (1979-1989)