Introduction Surface Albedo Albedo on different surfaces Seasonal change in albedo Aerosol radiative forcing Spectrometer (measure the surface albedo)

Measurement of the albedo on gray concrete. Measurement of the albedo on black surfaces. Measurement of the albedo on grass surfaces Measurement of the albedo on water surface at different

zenith angles. Comparison of the surface albedo on different surfaces

Conclusion

value of one means that all incoming light is reflected

Surface albedo is the fraction of Sun’s radiation reflected from a surface.

Albedo is measured on a scale of 0 to 1

value of zero indicates the surface does not reflect, it absorbs all incoming light .

value of one means that all incoming light is reflected from the surface.

An ideal white body has an albedo of 1 and an ideal black body has albedo of 0

• Earth receives both short and long wave radiation from the Sun

• Some radiation is reflected back to space

– Albedo-global mean planetary reflectance

• Clouds, air molecules, particles, surface reflection

• Earth’s albedo ~ 0.3

• About 30% of the incoming solar flux is reflected back to space

• reflection of solar radiation are due to ice, snow, clouds, aerosols, and deserts surfaces.

Liou Xie et .al. 2002

This graph shows the land surface albedo over wavelengths 400-1000nm.

From this graph we can see that the average albedo is approximately 0.3 or 30% and peaks around 900nm.

R. T. A. Prado, F. L. Ferreira/ Energy and Buildings 37 (2005) 295-300.

This graph shows the curve of reflection for red ceramics.

Values of reflectance were found to be around 9% in the UV range.

33% in the visible range 79% in the infrared(IV) range The average albedo over all

wavelengths between 290.0 and 2500.0nm was found to be 67.7%

Williams et al., 1993.

AEROSOL RADIATIVE FORCING Top of Atmosphere Idea

Modified from Dr. Seth Olsen’s AGU Presentation 2006.

Single scattering approximation

S = Solar constant (1386 [W/m2])

T = Atmospheric transmission (0.8)

N = Cloudiness (0.5)

g = Asymmetry parameter (0.7)

w = Single scattering albedo (0.75)

a = Surface albedo (MODIS)= Aerosol optical depth

Chylek and Wong, GRL, 1995

Strong Impacts on Boundary Layer Meteorology and Surface

Radiative Forcing.

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AEROSOL RADIATIVE FORCING

James Hansen, NASA Climatologist

Red Tide spectrometerLow costSmall foot print (89.1mm x 63.3 mm)The spectral response from 350nm to 1000nm wavelengthUtilizes a detector with 650 active pixel, that is 650 data point in one full spectrum. Integration times as fast as 3 milliseconds

Spectrometer help to measure :

AbsorbanceTransmissionReflectance

Solar RadiationVisible light (42% of solar energy)Near-infrared light (52%)Ultraviolet light (5%)

Albedo is the amount of sunlight that is reflected by a particular surface.

Black Asphalt Date: 28th April, 2012Time: 12:08 pm

Black PaperDate: 1st May, 2012Time: 4:35 pm

Zenith Angle = 64.5544°Time: 16:35:00Date: 05/01/2012Albedo = 0.015 – 0.08

Zenith Angle = 27.0551°Time: 12:08:03Date: 4/28/2012Albedo = 0.08 – 0.22

Zenith Angle = 27.0551°Time: 12:08:03Date: 4/28/2012Albedo = 0.08 – 0.22

Zenith Angle = 64.5544°Time: 16:35:00Date: 05/01/2012Albedo = 0.015 – 0.08

Date : 28th April, 2012Time : 3:52 pm

(nm)(nm)

Zenith Angle = 45.8890°Time: 15:52:15Date: 4/28/2012Albedo = 0.22 – 0.42

Date: 28th April, 2012Time: 11:50 am

Date: 28th April, 2012Time: 12:00 pm

Green GrassZenith Angle = 28.8215°Time: 11:50:02Date: 4/28/2012Albedo = 0.14 – 0.34

Green GrassZenith Angle = 28.8215°Time: 11:50:02Date: 4/28/2012Albedo = 0.14 – 0.34

Dry grassZenith Angle = 28.001°Time: 12:00:30Date: 4/28/2012Albedo = 0.18 – 0.47

Dry grassZenith Angle =28.001°Time: 12:00:30Date: 4/28/2012Albedo = 0.18 – 0.47

Date: 29th April, 2012Time: 1:19 pm andTime : 5:10 pm

Zenith Angle = 31.0610°Time: 13:19:03Date: 4/29/2012Albedo = 0.1 – 0.27

Zenith Angle = 60.3233°Time: 17:10:20Date: 4/29/2012Albedo = 0.31 – 0.76

Zenith Angle = 60.3233°Time: 17:10:20Date: 4/29/2012Albedo = 0.31 – 0.76

Zenith Angle = 31.0610°Time: 13:19:03Date: 4/29/2012Albedo = 0.1 – 0.27

Gray Concrete

Grass Surface

Water Surface

Black Road

Wavelength(nm)

Albedo

Liou Xie et .al. 2002

Wavelength(nm)

Albedo

Date: 5th April, 2012Time: 5:06 pm

Date: 12th April, 2012Time: 4:30 pm

Clear dayZenith Angle = 67.5875°Time: 16:30:30Date: 4/12/2012Albedo = 0.16 – 0.30

Cloudy dayZenith Angle = 75.3181°Time: 17:06:10Date: 4/05/2012Albedo = 0.01 – 0.22

Clear dayZenith Angle = 67.5875°Time: 16:30:30Date: 4/12/2012Albedo = 0.16 – 0.30

Cloudy dayZenith Angle = 75.3181°Time: 17:06:10Date: 4/05/2012Albedo = 0.01 – 0.22

(nm)(nm)

(nm)

Measuring and monitoring surface albedo plays an important role in the earths energy balance and climate.

The Surfaces which have albedo 1 or close to 1, reflect almost all incoming solar radiation.

Most surfaces that have an albedo of 1 or near 1 are white in color. The surfaces which have albedo zero or close to zero, absorb almost all

incoming radiation. Our measurements reveal that the albedo of black or dark surfaces was

very low, ranging from around zero to approximately 0.2. The albedo of grass varied from around 0.15 to 0.45 depending on the

condition of the grass. The albedo of water is dependent on the zenith angle and ranged from 0.1

to 0.76. Concrete was found to have the highest average albedo out of the surfaces

we measured, remaining at a fairly constant value of 0.3. Our measurements are consistent with current known surface albedo

values for various surfaces.