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Ultraviolet (UV) Radiation and its Physical Ultraviolet (UV) Radiation and its Physical Modulating Factors in Africa Based on TOMS Modulating Factors in Africa Based on TOMS

and NOAA Polar Orbiting Satellites Dataand NOAA Polar Orbiting Satellites Data

IntroductionIntroduction

What is solar ultraviolet rWhat is solar ultraviolet radiation?adiation?

• Ultraviolet radiation is paUltraviolet radiation is part of the solar electromagrt of the solar electromagnetic radiation spectrum fnetic radiation spectrum from about 400 nm to 100rom about 400 nm to 100 nm (where the visible ra nm (where the visible ray range ends) y range ends)

• It is a little over 8% of theIt is a little over 8% of the total solar spectrum total solar spectrum

Classification:Classification:• UV-AUV-A• UV-BUV-B• UV-CUV-C

Spectral Spectral regionregion

wavelewavelengthngth

% % energenergyy

InfrareInfraredd

>700 nm>700 nm 49.449.4

visiblevisible 4400-700 00-700

nmnm42.342.3

UV-AUV-A 400-315 400-315 nmnm

6.36.3

UV-BUV-B 315-280 315-280 nmnm

1.51.5

UV-CUV-C <280 nm<280 nm 0.50.5

Effects of UV radiationEffects of UV radiation•Different types of Skin Different types of Skin

cancer (DNA damage)cancer (DNA damage)•Early ageing of skinEarly ageing of skin•Eye disease called Eye disease called

cataractcataract•Human immune systemHuman immune system•Decreasing plant yieldDecreasing plant yield•Decrease in service time Decrease in service time

of infrastructureof infrastructure•Fading up of closesFading up of closes

Gaps in understanding UV and Gaps in understanding UV and the Determining Factorsthe Determining Factors

• Very few scientific studies in Africa Very few scientific studies in Africa on isolated cases.on isolated cases.

• Reports say the total column ozone is Reports say the total column ozone is intact (no depletion) in Africa. But intact (no depletion) in Africa. But few show the trend of ozone in Africa. few show the trend of ozone in Africa.

• UV interaction with clouds is complex UV interaction with clouds is complex and no attempt has been made in and no attempt has been made in Africa.Africa.

Problem Statement and Problem Statement and ContributionContribution

Having the gaps the problems are:Having the gaps the problems are:

a)a) Estimation of the dose of UV index Estimation of the dose of UV index (UVI) in Africa(UVI) in Africa

b)b) Quantification of the relationship of Quantification of the relationship of UV with ozone, aerosols and clouds UV with ozone, aerosols and clouds in Africain Africa

c)c) Investigation of the vertical Investigation of the vertical distribution of ozone in Africa and distribution of ozone in Africa and comparison with the higher latitudescomparison with the higher latitudes. .

ObjectivesObjectives• The research’s central objective is towards The research’s central objective is towards

development and understandingdevelopment and understanding modes of modes of variability for UV radiation in Africa and variability for UV radiation in Africa and establishment of its interplay with ozone, aerosols, establishment of its interplay with ozone, aerosols, and cloud parameters in eigenvector domain. and cloud parameters in eigenvector domain.

Specific ObjectivesSpecific Objectivesa) To quantify the UV dose in Africaa) To quantify the UV dose in Africab) To identify and explain the modes of variability of UV b) To identify and explain the modes of variability of UV

radiation, ozone, aerosols, and cloud physical radiation, ozone, aerosols, and cloud physical parameters in Africa in space and time,parameters in Africa in space and time,

c) To illustrate the seasonal variability of UV, Ozone, c) To illustrate the seasonal variability of UV, Ozone, and aerosols in Africa, understand how UV are and aerosols in Africa, understand how UV are modulated by various physical processes and modulated by various physical processes and factors, factors,

d) To establish the physical mechanisms of the d) To establish the physical mechanisms of the variation of UV in space and timevariation of UV in space and time

Absorption in the UVAbsorption in the UV

• Absorption by ozone, oxygen and Absorption by ozone, oxygen and nitrogen are wavelength dependentnitrogen are wavelength dependent

UV irradiance at surface are :UV irradiance at surface are :

- UV-A- UV-A 94% -- very small absorbed94% -- 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

The UV absorption cross-sectionsThe UV absorption cross-sections : :

UV Absorption Spectrum of UV Absorption Spectrum of Ozone:Ozone:

- The strongest absorption bands of O- The strongest absorption bands of O33 is called is called Hartley bands (200 to 300 Hartley bands (200 to 300 nm) nm)

- Weak absorption of UV by OWeak absorption of UV by O3 3 in in Huggins bands (300 – 360 nm)Huggins bands (300 – 360 nm)

- Very weak absorption of UV by OVery weak absorption of UV by O3 3 in in the visible and infrared region (440 – the visible and infrared region (440 – 1180 nm)1180 nm)

Biologically active UV radiationBiologically active UV radiation

The dose rate is an instantaneous measure The dose rate is an instantaneous measure of the biologically-weighted UV irradiance of the biologically-weighted UV irradiance

dEB )()(Biological action spectrum

Irradiance

The dose rate is an instantaneous measure of the biologically-weighted UV irradiance

BAS Cont…BAS Cont…Integration of the dose rate over a period Integration of the dose rate over a period

of the year in units of of the year in units of Jm-2, Jm-2,

dose rate = dose rate =

Diurnal dependence Diurnal dependence

of DNA damaging UV:of DNA damaging UV:

dtdFB )()(

Equator

400

600

Diurnal dependence of DNA-damaging dose rate on 21 June at three different latitudes (Madronich 1993a).

UV Dependence on Geophysical UV Dependence on Geophysical variablesvariables• Surface UV (UV irradiance) affectedSurface UV (UV irradiance) affected

a)a) ScatteringScattering

b)b) Absorption in the atmosphereAbsorption in the atmosphere

c)c) The stability of extraterrestrial solar radiation:The stability of extraterrestrial solar radiation:

extraterrestrial solar spectrum results in Ozone extraterrestrial solar spectrum results in Ozone which further results in UV which further results in UV

How is long term solar UV behaving?How is long term solar UV behaving?

An An increaseincrease of solar spectral irradiance at the of solar spectral irradiance at the 11-year solar activity cycle minimum since the 11-year solar activity cycle minimum since the Maunder minimum (year 1700) of 3.0% for Maunder minimum (year 1700) of 3.0% for wavelengths less than 300 nm and 1.3% for the wavelengths less than 300 nm and 1.3% for the band 300-400 nm band 300-400 nm

Dependence of UV on ozone Dependence of UV on ozone and other trace gasesand other trace gasesAs ozone decreases UV rises.As ozone decreases UV rises.

The ozone in any given location is a balance The ozone in any given location is a balance between three processes: in situ creation, in between three processes: in situ creation, in situ destruction, and transport in to or out of situ destruction, and transport in to or out of the location. the location.

How do we measure ozone?How do we measure ozone?

• Mixing ratio (ppmv)Mixing ratio (ppmv)

• Number density P Number density P ozoneozone= n KT (26)= n KT (26)

• Partial pressurePartial pressure

• Dobson unit (1 DU = 10Dobson unit (1 DU = 10-5-5m )m )

UVD Cont…UVD Cont…

Ozone CirculationOzone Circulation (Brewer Dobson (Brewer Dobson Circulation)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.

UVD Cont…UVD Cont…

They attenuate UV flux through the atmosphere They attenuate UV flux through the atmosphere aerosol optical depth (AOD)aerosol optical depth (AOD) and the average and the average column value of the single scattering albedo column value of the single scattering albedo

Dependence on Clouds!Dependence on Clouds!

Dependence on Aerosols!Dependence on Aerosols!

• Under overcast conditions, clouds decrease Under overcast conditions, clouds decrease the irradiance measured at the surface the irradiance measured at the surface

• However, enhancements of up to 25% can However, enhancements of up to 25% can occur under broken cloud conditions occur under broken cloud conditions

UV, aerosols and ozone dataUV, 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 dataVertical 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 dataClouds data

Obtained fromObtained from ISCCP (1984-2001)ISCCP (1984-2001)

Data Types and MethodsData Types and Methods

DTM cont…DTM cont…

• Singular value decomposition (svd) Singular value decomposition (svd) /empirical orthogonal function (EOF)/ /empirical orthogonal function (EOF)/ Principal Component analyses (PCA)Principal Component analyses (PCA)

• variance analysesvariance analyses

• Correlation and regression analysesCorrelation and regression analyses

• Establishing physical relationship Establishing physical relationship

MethodsMethods

The Spatial and Temporal Results of UV, The Spatial and Temporal Results of UV, AI and Ozone over AfricaAI and Ozone over Africa

UV space-time modeUV space-time modeThe first few modes explain the total The first few modes explain the total

variability of the data.variability of the data.-The first spatial mode of UV ~19% of the -The first spatial mode of UV ~19% of the

total variability, total variability, -the second Spatial mode ~9% and so on: -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

modesmodes

Res. Cont…Res. Cont…

• 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 In the same season 37 % trend increase (1997 to 2002)to 2002)

Seasonal variability of UV in Seasonal variability of UV in AfricaAfrica

y = -0.0228x + 45.299

R2 = 0.6628

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

1980 1982 1984 1986 1988 1990 1992

Periods

UV

tim

e s

eri

es (

J/m

2) FMAM

JJASONDJLinear (JJAS)

Aerosols space-time modeAerosols 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% andThe third mode ~7% and

• The fourth mode ~5%The fourth mode ~5%

Res. Cont…Res. Cont…

y = -4E-05x + 1.1361

R2 = 0.2173

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

May-79

Oct-80

Feb-82

Jul-83

Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

ae

ros

ol i

nd

ex

tim

e s

eri

es

1 y = 3E-06x - 0.1025

R2 = 0.0039

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

May-79

Oct-80

Feb-82

Jul-83 Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

ae

ros

ols

ind

ex

tim

e s

eri

es

2

y = 2E-05x - 0.5088

R2 = 0.1422

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

May-79

Oct-80

Feb-82

Jul-83

Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

aero

sol i

nd

ex ti

me

seri

es 3

y = 4E-06x - 0.1331

R2 = 0.0182

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

May-79

Oct-80

Feb-82

Jul-83

Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

aero

sol i

nd

ex t

ime

seri

es 4

The aerosols temporal modesThe aerosols temporal modes

The ozone spatial and temporal modesThe 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 mode11% the third mode

• 5% by the fourth mode5% by the fourth mode

The first four values alone represent ~50% The first four values alone represent ~50% of the total variance in the dataof the total variance in the data

Res. Cont…Res. Cont…

The Temproal modes of ozoneThe Temproal modes of ozoney = 0.0008x - 25.979

R2 = 0.0863

-10

-5

0

5

10

15

May-79

Oct-80

Feb-82

Jul-83 Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

ozon

e co

nc. (

DU

)

y = 6E-05x - 1.9911

R2 = 0.0009

-8

-6

-4

-2

0

2

4

6

8

May-79

Oct-80

Feb-82

Jul-83

Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months,years)

ozo

ne

con

c. (

DU

)

y = -7E-05x + 2.458

R2 = 0.0018

-6

-4

-2

0

2

4

6

8

May-79

Oct-80

Feb-82

Jul-83 Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

ozon

e co

nc. (

DU

)

y = 0.0001x - 3.1752

R2 = 0.0078

-6

-4

-2

0

2

4

6

May-79

Oct-80

Feb-82

Jul-83

Nov-84

Mar-86

Aug-87

Dec-88

May-90

Sep-91

Jan-93

periods (months, years)

Ozo

ne

co

nc

. (D

U)

Vertical ozone mixing-ratioVertical ozone mixing-ratio

10 years average ozone amount tropical 10 years average ozone amount tropical

Africa (ONDJ)Africa (ONDJ)

Res. Cont…Res. Cont…

-1

4

9

14

19

24

29

34

39

44

49

54

2 3 4 5 6 7 8 9 10ozone (ppmv)

Pre

ssue

r le

vel (

hPa)

Jan

Oct

Nov

Dec

Stratospheric ozone

Tropospheric ozone

Res. Cont…Res. Cont…• If ozone concentration If ozone concentration

is highest in the is highest in the stratosphere in the stratosphere in the period, it is also the period, it is also the least in the least in the troposphere in the troposphere in the same period. same period.

• In general, the In general, the vertical ozone vertical ozone concentration shows concentration shows opposite quantitative opposite quantitative variability in the two variability in the two spheres of the spheres of the atmosphere.atmosphere.

0

10

20

30

40

50

60

2 4 6 8 10 12Ozone(ppmv)

Pressu

re (hPa

)

1981

1982

1983

1984

1985

1999

2000

2001

2002

2003

Res. Cont…Res. Cont… For the other cross For the other cross

sections ~30S and sections ~30S and ~30N is taken and ~30N is taken and compared with the compared with the other latitudes, ~0, other latitudes, ~0, ~60S, ~60N, ~90S and ~60S, ~60N, ~90S and ~90N. ~90N.

The vertical ozone The vertical ozone concentration is concentration is relatively highest in relatively highest in October for 60N (9.544 October for 60N (9.544 ppmv), and least for ppmv), and least for 60S (8.48 ppmv). The 60S (8.48 ppmv). The difference is 11% lower difference is 11% lower than the peak. than the peak.

Latitudinal comparison of vert. ozone (ppmv)

0

10

20

30

40

50

60

0 5 10 15

Ozone (ppmv)

Pres

sure

heigh

ts (hP

a)

Oct ~0

Oct ~30N

Oct ~30S

Oct 60N

Oct 60S

Oct 90N

Oct 90S

Res. Cont…Res. Cont…• In November, the In November, the

ozone-mixing ratio is ozone-mixing ratio is least in values at and least in values at and around 90N and 90S around 90N and 90S in the stratosphere. in the stratosphere.

• the greatest ozone-the greatest ozone-mixing ratio is mixing ratio is observed for 30S and observed for 30S and its nearest locations its nearest locations (because of the ozone (because of the ozone transport from the transport from the equator to higher equator to higher latitudes throughlatitudes through Brewer-Dobson CirculBrewer-Dobson Circulation).ation).

Vert. Ozone for latitudes ~0, 30N,30S, 60N, 60S, 90N, 90S in Nov.

0

10

20

30

40

50

60

2 4 6 8 10

Ozone (ppmv)

Pres

sure

heigh

ts (h

Pa)

Nov ~0

Nov~30NNov~30SNov 60N

Nov 60S

Nov 90N

Nov 90S

Res. Cont…Res. Cont…Antarctic ozone vertical distn.

0

10

20

30

40

50

60

0 5 10 15

Ozone (ppmv)

Pre

ss

ure

he

igh

ts (

hP

a)

Oct-81 ~90sOct-82 ~90sOct-83 ~90sOct-84 ~90sOct-85 ~90sOct-99 ~90sOct-00 ~90sOct-01 ~90sOct-02 ~90sOct-03 ~90s

Antarctic vertical ozone distn.

0

10

20

30

40

50

60

0 2 4 6 8 10 12

Ozone (ppmv)

Pressu

re h

eig

ht (

hP

a)

Nov-81 ~90sNov-82 ~90sNov-83 ~90sNov-84 ~90sNov-85 ~90sNov-99 ~90sNov-00 ~90sNov-01 ~90sNov-02 ~90sNov-03 ~90s

0

10

20

30

40

50

60

0 5 10 15

Antarctic Ozone (ppmv)

Pre

ss

ure

le

ve

ls (

hP

a)

Dec-81 ~90sDec-82 ~90sDec-83 ~90sDec-84 ~90sDec-85 ~90sDec-99 ~90sDec-00 ~90sDec-01 ~90sDec-02 ~90sDec-03 ~90s

Antarctic Ozone (ppmv)

0

10

20

30

40

50

60

0 5 10 15Ozone (ppmv)

Pre

ssu

re h

eig

hts

(h

Pa)

Jan-81 ~90s

Jan-82 ~90s

Jan-83 ~90s

Jan-84 ~90s

Jan-85 ~90s

Jan-99 ~90s

Jan-00 ~90s

Jan-01 ~90s

Jan-02 ~90s

Jan-03 ~90s

Results and DiscussionResults and DiscussionUltraviolet Radiation in AfricaUltraviolet Radiation in AfricaAround 18N, Around 18N,

UVery dose = 5500 J/mUVery dose = 5500 J/m22

At tropics high, At tropics high,

At high latitudes lessAt high latitudes less

UVI = UVI =

dose rate/unit time dose rate/unit time

(mW/m(mW/m22) x 20 m) x 20 m22/mW/mW

Ery UV in J/m2

0

1000

2000

3000

4000

5000

6000

-80 -60 -40 -20 0 20 40 60 80Latitude

Eryth

ermal

UV in

J/m2

a)a)Latitudinal Comparison of UV and ozoneLatitudinal Comparison of UV and ozone

Why higher latitudes ?Why higher latitudes ?

Res. Cont…Res. Cont…

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

-90 -60 -30 0 30 60 90

Latitude

Ozo

ne

an

d U

V a

mo

un

t Ozone amount (DU)

UV Index

Ozone CirculationOzone Circulation (Brewer Dobson (Brewer Dobson Circulation)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.

Latitudinal Comparison of UV, ozone and Aerosol Latitudinal Comparison of UV, ozone and Aerosol IndexIndex

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

Latitude

ozo

ne

, Uv

, an

d a

ero

so

l

ozone

uv

Aerosol

Due to the Saharan and Arabian Deserts

Ozone

UV

UV and ozoneUV and ozone

1050-5-10

Oz_NMBS_1

200

100

0

-100

-200

UV_N

MBS

_4Fit line for Total

Total

Legend

R Sq Linear = 0.413

UV (O3) = -18.595 -UV (O3) = -18.595 -12.233x O312.233x O3 (41%)

b) Aerosols b) Aerosols andand UV Association UV Association

• only 7% of the total variability of only 7% of the total variability of UV over the African continent can UV over the African continent can be expressed by aerosols.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 where Ts (1-4) means respective time series of eigenvectors.series of eigenvectors.

Res. Cont…Res. Cont…

The clouds, which have shown significant The clouds, which have shown significant relationship, are as follows:relationship, are as follows:

• All clouds- Top TemperatureAll clouds- Top Temperature

• Altocumulus Liquid clouds – Optical Altocumulus Liquid clouds – Optical Thickness and top temperatureThickness and top temperature

• Cirrostratus cloud – Top Pressure Cirrostratus cloud – Top Pressure

• Cirrus cloud – Water PathCirrus cloud – Water Path

Of 100 cloud parameters attempted to Of 100 cloud parameters attempted to associate.associate.

Res. Cont…Res. Cont…

The general model which accounts for The general model which accounts for the clouds in this UV investigation isthe clouds in this UV investigation is

UV = -30.293 – 11.492 x (all-cloud-temp.) – UV = -30.293 – 11.492 x (all-cloud-temp.) – 56.791 x 56.791 x (altocumulus Liquid-top-opt.) – (altocumulus Liquid-top-opt.) – 49.453 x (altocumulus liquid – temp.) – 3.488 49.453 x (altocumulus liquid – temp.) – 3.488 x (cirrostratus cloud – top - press) – 7.029 x x (cirrostratus cloud – top - press) – 7.029 x (cirrus cloud water path)(cirrus cloud water path)

The overall contribution of clouds to the The overall contribution of clouds to the UV analysis is around 39%.UV analysis is around 39%.

Res. Cont…Res. Cont…

• The possible range of values of UV index (UVI) obtained in The possible range of values of UV index (UVI) obtained in

Africa is between 4 and 9.Africa is between 4 and 9.

• The overall trend of the UVery is decreasing in all of the The overall trend of the UVery is decreasing in all of the

seasons.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 The tropical Africa vertical ozone profile show stable

variability.variability.

• The 30N and 30S show relatively higher stratospheric ozone.The 30N and 30S show relatively higher stratospheric ozone.

conclusionconclusion

• UV interplayed with all cloud type and properties UV interplayed with all cloud type and properties

( top pressure, top temperature, water path, and ( top pressure, top temperature, water path, and

optical thickness) except cloud amount.optical thickness) except cloud amount.

• UV interplayed with all cloud type and properties UV interplayed with all cloud type and properties

( top pressure, top temperature, water path, and ( top pressure, top temperature, water path, and

optical thickness) except cloud amount.optical thickness) except cloud amount.

• Deep convective clouds does not show Deep convective clouds does not show

significant relationship with UV but are the main significant relationship with UV but are the main

cloud types in tropical Africa.cloud types in tropical Africa.

• Interesting results come out from the UV and cloud Interesting results come out from the UV and cloud

relationships:relationships:

• UV interplayed with all cloud type and properties ( top UV interplayed with all cloud type and properties ( top

pressure, top temperature, water path, and optical pressure, top temperature, water path, and optical

thickness) except cloud amountthickness) except cloud amount

• All clouds account for 39 % of the total variability of UV All clouds account for 39 % of the total variability of UV

irradiance.irradiance.

• Deep convective clouds does not show significant Deep convective clouds does not show significant

relationship with UV but are the main cloud types in relationship with UV but are the main cloud types in

tropical Africa.tropical Africa.

Sum. Cont….Sum. Cont….

Ultraviolet Radiation

in

Africa

Clouds (39%)

Ozone concentration

(40%)

Aerosol Index (7%)

Thank y Thank y u!u!

Ultraviolet radiation spectrumUltraviolet radiation spectrum

UV Absorption Spectrum of UV Absorption Spectrum of Molecular oxygen:Molecular oxygen:

• Schumann - Schumann - Runge band: 200 Runge band: 200 – 125 nm– 125 nm

• Several bands: Several bands: 125 – 100 nm 125 – 100 nm (e.g. Lyman- (e.g. Lyman- 121 nm)121 nm)

• Hopfield bands: Hopfield bands: <100 nm<100 nm

• Hertzberg Bands: Hertzberg Bands: 260 – 200 nm 260 – 200 nm

BAS Cont…BAS Cont…• Seasonal and latitudinal dependence of Seasonal and latitudinal dependence of

daily dose rate (Jm-2 day-1) for DNA daily dose rate (Jm-2 day-1) for DNA damage calculated for:damage calculated for:

-clear skies-clear skies

-using ozone -using ozone

column (DU)column (DU)

average (1979-1989)average (1979-1989)