Environ Remote Sensing
Environ Remote Sensing ERS 186
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Dan Skiles IV
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Dan Skiles IV
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This 13 page Class Notes was uploaded by Dan Skiles IV on Tuesday September 8, 2015. The Class Notes belongs to ERS 186 at University of California - Davis taught by Staff in Fall. Since its upload, it has received 14 views. For similar materials see /class/187674/ers-186-university-of-california-davis in Environmental Resource Science at University of California - Davis.
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Date Created: 09/08/15
Clouds g raindrops 62 x 25 W x quot drizzle 9 23 x 6 39 39 Cloud drops Kquot 0w x 39 Q g 39 1 0quotquot 4 we a 39 s Smoke dust xquot 9 a 9 4 Q 2 Qc Air 39 a 2 molecules VisNIR Thermal l as ve radar microwave wavelength Raylelgh Scattenng X less than 01 greater than 10393 particle is small compared to wavelength insensitive to particle shape Mie Scattering X in the range of0l50 wavelength and circumference of the particle are comparable radiation interacts strongly with particle often strong absorption Nonselective scattering geometric optics X greater than 50 sphere is large in comparison with the wavelength shape matters Clouds In the Visible and NIR portion of the spectrum Cloud drops are nonselective scatterers scattering ef ciency is large liquid water does not absorb in the visible thus clouds have minimal absorption in the visible in the NIR absorption increases due to liquid and water vapor absorption Averaged over the solar spectrum clouds scatter roughly 74 absorb 10 and transmit 16 Clouds In the thermal region 85125 um Cloud droplets are Mie scatterers clouds absorb nearly all of the infrared radiation They are essentially blackbodies In the microwave portion of the spectrum X is approx 001 for cloud drops thus they are Rayleigh scatterers absorption due to cloud drops is very small transmittance is greater than 90 ice particles absorb even less Raindropsize particles interact strongly with microwaves Mie scatterers and thus transmittance is less for raining clouds Clouds Cloud characteristics received from passive remote sensing data cloud detection cloud re ectance cloud emissivity liquid water content optical depth cloud phase water or ice particle size distribution cloud top height Cloud Mask MODIS Cloud Mask Ackerman et al JGR 103 1998 MODIS cloud mask uses multispectral imagery to indicate whether the scene is clear cloudy or affected by shadows Cloud mask is input to rest of atmosphere land and ocean algorithms Mask is generated at 250 m and 1 km resolutions dayampnight Mask uses 17 spectral bands ranging from 0551393 um including new 138 pm band 11 different spectral tests are performed with different tests being conducted over each of 5 different domains land ocean coast snow and desert Algorithm based on radiance thresholds in the infrared and reflectance and reflectance ratio thresholds in the visible and nearinfrared Cloud mask consists of 48 bits of information for each pixel including results of individual tests and the processing path used bits 1 amp 2 give combined results confident clear probably clear probably cloudy cloudy Clouds Cloud type determination using Visible and thermal info Cold middle level high clouds Thermal Infrared Ther Cl and or semitransparent convective clouds Cloud Type Determination Based on Multispectral Measurements in the Visible and Thermal Infrared Regions of the Spectrum middle level convective clouds low cumuliform Cl and Visible Bright Cloud optical thickness Re ection function of a nonabsorbing band is pIimaIily a function of optical depth while the re ection function of an NIR absorbing band is Rerlpmance 2 11 pm function ofeffective radius 0 g V V 39 H 777 Ayn H A 4 4 06 O B 1 O 1 2 Re ectance O 86 um Am Luann 0mm Inmknaas llqmu am 15 Ice w Cloud optical thickness at Apnl 1000 raw IJIL Spherical Albedo Clouds Different water droplet sizes 08 06 MODIS Atmosphere Bands l l u l I I I ICO 75 um 16 r 4pm Burn 12um 16um 20um e e r G 6 r 04 02 I Oo l I l I I 05 10 15 20 2 5 Wavelength urn x I We quot39 Thermodynamic Phase detection Uses water and ice emissivity differences at the 85 85 11 pm indeX is large and positive for ice clouds small and negative for water clouds a re 20 urn Vapor e l up 3 39 11 m nus 11911ch ETEij Us Clouds Can be sensed using Sounding similarly to water vapor Sounding is used to determine cloud height amongst other things However this is dif cult due to spatial and temporal heterogeneity Clouds MISR multiangle Viewing of cloud properties Clouds MISR exploits the information content of the angular anisotropy of the upwelling radiation field Algorithms for remote sensing by way of angular signatures are in their infancy Plenty of pioneering work to be done with angular signatures 440 nm 865 nm Reflectance High Cloud 394 Low Cloud Clear Snow 6 80 60 40 20 0 20 40 60 80 View Angle Forward Backward Trepica Rainfall N en en mill110 Microwave Irrlager TIMI Data tha ned en lvilareli 3993 1998 A paSSive microwave sensor that measures in ve frequencies l0 7 45 km spatial resolution l9 4 2l 3 3 7 and 85 5 GHZ 5 km spatial resolution it has dual polarization at four of line frequencies Swath width is487 miles 780 km The 10 7 GHZ frequency provides a a linear response to rainfall Height km A TRMM Piecipitation Radar PR B data obtained on March 9 1998 u B 100 200 300 400 Distance km Alongtrack crosssection of TRMM Precipitation Radar data obtained on March 9 1998 I Snow and Ice Visible and NIR Microwave Significant Large penetration scattering in Visible in dry snow many penetration near m surface only 05m in sensitive to grain blue and few mm in size water content NIR and IR and layering mainly used for less penetration in determining extent in wet snow cloudless conditions Snow Different grain sizes REFLECTANCE 90 05 10 15 20 25 50 WAVELENGTH microns Snow mm mm 50 Snow water equivalent for different grain sizes a 50mm 01 mm o 05 mm 0 mm momsmun u i W WW i o n uolmolnstuw 2 um 05 l E 5qu ll 39 I 9911 01 pram 39 39 Eml ppmw Ice rODgn FD gm has I J J L r l l p f A Impurities in snow affect re ectance IJIII 39TScmr J J LHL 39 39 vapun gnaw 39 CIJpprru quot k I pnmw Smlil ppmw quot39 lee r IDUleLm FHOJPN L tare2 1II1rI11 Dl39 llllll lllllllk III I IIEIII 1T 13 Ll WAVE L ENGTH p ml Re ectance of Clouds and Snow in the Wavelength Interval 04 25 pm 80 60 E E40 0 Q a Q a 20 G 04 07 10 15 20 25 Wavelength um
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