Three stories about Three stories about aerosolsaerosols

Marin Simić, 4.GMarin Simić, 4.GGimnazija “Matija Mesić” Slav. BrodGimnazija “Matija Mesić” Slav. Brod

C r o a t i aC r o a t i a

2424thth September 2012 September 2012

I. STORY:I. STORY:“There’s something sometimes “There’s something sometimes

in our atmosphere”in our atmosphere”

Solar radiation in the Earth Solar radiation in the Earth atmosphereatmosphere

Incoming solar Incoming solar radiationradiationi=ii=ioo exp (- m ∙ ( exp (- m ∙ (ΦΦaa++ Φ Φgg++ Φ ΦNOxNOx++ Φ Φww++ Φ ΦO3O3++ Φ Φrr))))

i i - intensity that reaches Earth’s surface- intensity that reaches Earth’s surface

iioo - intensity at the top of the atmosphere- intensity at the top of the atmosphere

m m - atmosphere optical mass- atmosphere optical mass

ΦΦ - optical thickness (- optical thickness (depthdepth))

a a - - aerosolsaerosols / absorption and scattering / absorption and scattering

g g - - atmospheric gases atmospheric gases /absorption/absorption

NOx NOx - - nitrogen oxidesnitrogen oxides/ absorption/ absorption

w w - - water vapour / water vapour / absorptionabsorption

OO33 - - ozoneozone /absorption /absorption

r r - - Rayley scattering on ORayley scattering on O22 and N and N22 molecules- molecules- “blue color of the sky”“blue color of the sky”

Atmosphere optical depthAtmosphere optical depthi=i=iioo exp (- m ∙ ( exp (- m ∙ (ΦΦaa++ Φ Φgg++ Φ ΦNOxNOx++ Φ Φww++ Φ ΦO3O3++ Φ Φrr))))

iiλλ=i=i0,0,λλexp(-exp(- m ∙ m ∙ ΦΦλλ))iiλλ tthe intensity of a narrow beam of sunlight of a he intensity of a narrow beam of sunlight of a

particular wavelength that reaches Earth's surfaceparticular wavelength that reaches Earth's surface

II0 0 λλ the intensity of sunlight just above Earth's the intensity of sunlight just above Earth's atmosphereatmosphere

ΦΦλλ atmosphere optical thickness – extinction atmosphere optical thickness – extinction coefficient of the incoming radiation due to coefficient of the incoming radiation due to scattering and absorption on molecules and aerosolsscattering and absorption on molecules and aerosols

m relative air massm relative air mass ΦΦaa aerosols optical thickness aerosols optical thickness is the degree to which aerosols prevent is the degree to which aerosols prevent

the transmission of light by absorption or scattering of light.the transmission of light by absorption or scattering of light. - - the integrated extinction coefficient over a vertical column of the integrated extinction coefficient over a vertical column of

unit cross sectionunit cross section

Relative air massRelative air mass- the path length relative to that at the zenith at the path length relative to that at the zenith at

sea levelsea level

relative optical mass = S/D = 1/sinrelative optical mass = S/D = 1/sinθθfor for θθ < 30 < 30oo

II. STORY:II. STORY:What we can do about it?What we can do about it?

Aerosol measurements made carefully Aerosol measurements made carefully according to the protocol with the GLOBE according to the protocol with the GLOBE sun photometer should be accurate to sun photometer should be accurate to within less than about 0,02 AOD units. within less than about 0,02 AOD units.

The accuracy of measurements made with The accuracy of measurements made with a GLOBE sun photometer is comparable to a GLOBE sun photometer is comparable to measurements made with other types of measurements made with other types of sun photometers. sun photometers.

In comparison even operational In comparison even operational “professional” sun photometers claim “professional” sun photometers claim accuracies of no better than 0,01 AOD. accuracies of no better than 0,01 AOD.

Efforts of scientists…Efforts of scientists… The very first calibrations of LED sun photometers The very first calibrations of LED sun photometers

were made at Seguin Texas, in December 1998, were made at Seguin Texas, in December 1998, and later at Mauna Loa Observatory, Hawaii on and later at Mauna Loa Observatory, Hawaii on several occasions. several occasions.

The experiment made by Mims and his team, as The experiment made by Mims and his team, as well as measurements performed by other well as measurements performed by other scientists show that AOD obtained from the LED scientists show that AOD obtained from the LED detector is consistent with data obtained from detector is consistent with data obtained from Sun photometers with narrowband optical filters. Sun photometers with narrowband optical filters.

Langley’s calibration plot for GLOBE LED sun Langley’s calibration plot for GLOBE LED sun photometers were presented in several papers photometers were presented in several papers prepared by GLOBE scientific team and other prepared by GLOBE scientific team and other scientists (Brooks 2001, Mims III 1998) . scientists (Brooks 2001, Mims III 1998) .

GLOBE Sun PhotometerGLOBE Sun Photometer

The true is:The true is:

Students can reliably make the Students can reliably make the required measurements and LED required measurements and LED based Sun photometers give results based Sun photometers give results that compare favourably with that compare favourably with conventional filter based instruments conventional filter based instruments even thought their optical properties even thought their optical properties are significantly different. are significantly different.

Our efforts together…Our efforts together…

More than 120 GLOBE schools More than 120 GLOBE schools around world are conducting aerosol around world are conducting aerosol measurements on daily basis and measurements on daily basis and have reported around 80.000 data on have reported around 80.000 data on AOD since the project started.AOD since the project started.

In 2010In 2010 tthere here wewere four GLOBE sun re four GLOBE sun photometers operating in Croatia photometers operating in Croatia andand 5000 measurements 5000 measurements

Student’s project Student’s project Medicinska skola Zagreb and II Gimnazija Medicinska skola Zagreb and II Gimnazija

Zagreb prepared together very interesting Zagreb prepared together very interesting project on air quality in Zagreb. project on air quality in Zagreb.

They took measurements on the same They took measurements on the same days and compare the AOD values. Beside days and compare the AOD values. Beside that they compare the official data on that they compare the official data on suspended particles and also use bio suspended particles and also use bio indicators as a measure of air quality. indicators as a measure of air quality.

High values of AOD, no matter what the High values of AOD, no matter what the cause, may be linked to human health cause, may be linked to human health through their influence on respiratory through their influence on respiratory system. system.

Atmosphere Transmission in Atmosphere Transmission in ZagrebZagreb

The connection with science…The connection with science…

Students are encouraged to compare Students are encouraged to compare their measurements with other their measurements with other ground and satellite based ground and satellite based measurements. Such comparison can measurements. Such comparison can serve both as a check on GLOBE serve both as a check on GLOBE measurements and on the measurements and on the performance of other sun performance of other sun photometers. photometers.

III. STORY:III. STORY:How does it impacts our present, How does it impacts our present,

our future?our future? Energy budget Energy budget ::

by directly scattering and absorbing radiationby directly scattering and absorbing radiation Water cycleWater cycle:: by by servservinging as condensation nuclei during cloud as condensation nuclei during cloud

formation and formation and by by influencinfluencinging precipitation precipitation Biogeochemical cycleBiogeochemical cycle::

vulcanic eruptions, dust storms, erosionvulcanic eruptions, dust storms, erosion Human healthHuman health

impact the quality of the air that we breathe and impact the quality of the air that we breathe and the health of all living organismsthe health of all living organisms

Don’t forget…Don’t forget… Information about the concentration, size Information about the concentration, size

distribution, and variability of aerosols in the distribution, and variability of aerosols in the atmosphere and AOD is needed for climate atmosphere and AOD is needed for climate studies, for comparison with satellite data, to studies, for comparison with satellite data, to track events that alter aerosol concentrations and track events that alter aerosol concentrations and to understand the global distribution and to understand the global distribution and variability of aerosols.variability of aerosols.

Routine ground based AOD observations are of Routine ground based AOD observations are of outmost importance for the calibration and outmost importance for the calibration and validation of AOD retrievals from satellites. In validation of AOD retrievals from satellites. In addition they are necessary to correct for aerosol addition they are necessary to correct for aerosol effects in the retrieval of other satellite products. effects in the retrieval of other satellite products.

  

And we are not allone…And we are not allone… Today, several networks use handheld LED Sun Today, several networks use handheld LED Sun

photometers as ground base instruments, and photometers as ground base instruments, and determine AOD values and validate satellite data determine AOD values and validate satellite data according to measurements performed by LED according to measurements performed by LED Sun photometers. Sun photometers.

Besides networks operated by students and Besides networks operated by students and volunteers, like GLOBE and The Haze network, volunteers, like GLOBE and The Haze network, some are operated by national weather service some are operated by national weather service or Institutes like The Chinese Sun Haze meter or Institutes like The Chinese Sun Haze meter Network that started in 2004 as the very first Network that started in 2004 as the very first standard network established to measure AOD standard network established to measure AOD through China (Xin 2007). through China (Xin 2007).

The networks are collaborating with Aerosol The networks are collaborating with Aerosol Robotic network (AERONET) and the Moderate Robotic network (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS). Resolution Imaging Spectroradiometer (MODIS).

Literature I.Literature I.1. Aničić J. et al., 2010: Kakav zrak udišemo u 1. Aničić J. et al., 2010: Kakav zrak udišemo u

središnjem I zapadnom dijelu Zagreba? središnjem I zapadnom dijelu Zagreba? (Proceedings of the 13 Annual Croatian GLOBE (Proceedings of the 13 Annual Croatian GLOBE Conferences, Zadar, available on Conferences, Zadar, available on www.vnovak.hr/globe/smotra2010/zadar_10_projekti.html))

  2. Boersma, K.F. and J.P. de Vroom, 2006: Validation 2. Boersma, K.F. and J.P. de Vroom, 2006: Validation

of MODIS aerosol observations over the of MODIS aerosol observations over the Netherlands with GLOBE student measurements, Netherlands with GLOBE student measurements, Journal of Geophysical Research, Journal of Geophysical Research, 111111, D20311, , D20311, doi:10.1029/2006JD007172doi:10.1029/2006JD007172

3. Brooks, D.R, and F.M. Mims III, 2001: Development 3. Brooks, D.R, and F.M. Mims III, 2001: Development of an inexpensive hand held LED-based Sun of an inexpensive hand held LED-based Sun photometer for the GLOBE program, Journal of photometer for the GLOBE program, Journal of Geophysical Research, Geophysical Research, 106106, 4733-4740, , 4733-4740, doi:10.1029/2000JD900545doi:10.1029/2000JD900545

Literature II.Literature II. 4. Mims III, F. M., 1992: Sun Photometer with 4. Mims III, F. M., 1992: Sun Photometer with

Light-Emitting Diodes as Spectrally Selective Light-Emitting Diodes as Spectrally Selective Detectors, Applied Optics, Detectors, Applied Optics, 3131, 6965-6967, 6965-6967

5. Mims III, F. M. , 1998: An Inexpensive and 5. Mims III, F. M. , 1998: An Inexpensive and Accurate Student Sun Photometer with Light-Accurate Student Sun Photometer with Light-Emitting Diodes as Spectrally Selective Detectors, Emitting Diodes as Spectrally Selective Detectors, Proceedings of the Third Annual GLOBE Proceedings of the Third Annual GLOBE Conference, 232-239Conference, 232-239

6.6.  Xin, J., et al., Xin, J., et al.,  2007: Aerosol optical depth 2007: Aerosol optical depth (AOD) and Ångström exponent of aerosols (AOD) and Ångström exponent of aerosols observed by the Chinese Sun Hazemeter Network observed by the Chinese Sun Hazemeter Network from August 2004 to September 2005, from August 2004 to September 2005, Journal of Journal of Geophysical ResearchGeophysical Research, , 112112, D05203, , D05203, doi:10.1029/2006JD007075doi:10.1029/2006JD007075

Literature IIILiterature III

7. 7. gaw.web.psi.ch

8. www.globe.gov8. www.globe.gov