Validation Of Land Surface Temperature Environmental Sciences Essay

Surface temperature for both land and ocean is one of the most of import parametric quantities ; surface temperature determines the biogeochemical activities, rate of heat flow and H2O transit between the surface and atmosphere. Global environmental procedures influence by it. In the growing of flora, dirt and canopy are two chief determiners of temperature, play a critical function in seasonal starting and dissolution in growing. Fluctuation in surface temperature effects hydrologic procedure such as evapotranpiration, snow and ice thaw. Furthermore in the categorization of land surface types and planetary land screen, surface temperature shown to be an of import perceptive factor. ( EOS )

When infinite radiometry is used to obtain land surface temperature, three chief effects have to be considered for: angular, atmospheric, and emissivity effects. Three most of import effects of ambiance are upward atmospheric emanation, downward atmospheric irradiance reflected from surface, and soaking up ( Franca & A ; Cracknell, 1994 ) . In the part of infrared window between 8 to12 um aerosol soaking up and sprinkling are minor and usually ignored ( Prata et.al. , 1995 ) . For atmospheric consequence H2O bluess are chiefly responsible, other gases such as C dioxide ( CO2 ) and ozone ( 03 ) vary easy. Furthermore, in the atmosphere C dioxide is distributed every bit, and ozone ( 03 ) is of limited importance in ambiance. Therefore H2O vapour is the most relevant gas which is ill assorted and varies on short clip graduated table, Therefore the regular information about the province of ambiance particularly temperature and H2O vapour profile is needed. Radiosonde is most accurate method for atmosphere, it gives information and consequences. When we are utilizing satellite measurings sounding have to be synchronal and co-located. Therefore the information from different sounders such as ( TIROS ) operational perpendicular sounder ( TOVS ) onboard National Oceanic and atmospheric Administration ‘s ( NOAA ) these are good suited for big graduated table surveies ( Reutter et.al. , 1994 ; Lakshmi & A ; Susskind 2000 ) . Land surface which is observed by satellite detectors from different sing angles, and hence approximative brightness temperature is compensated for zenith angle ( Kimes et.al. , 1980 & A ; 1983 ; Ignatov & A ; Dergileva, 1994 )

Land surface temperature and surface emissivity ( E ) is the most of import parametric quantities in the surveies of energy budget appraisal, earth surface characteristics and set down screen rating. Thermal belongingss of surface/subsurface stones, atmospheric province and surface energy balance is controlled by land surface temperature, and is most critical factors in legion environmental theoretical accounts ( Baker & A ; Li, 1990 ) . The most of import component of Surface/ Subsurface stones is silicate stones and emissivity is most of import factor for these types of stones ( Lyon, 1965 ; Vincent & A ; Thomson, 1972 ) . Thermal infrared remote detection is used to recover emissivities ; land surface temperature can be used for the appraisal of glow informations if atmospheric parametric quantities and emissivities are known.

The rectification of atmospheric province and surface emissivity is due to the retrieval of orbiter informations. The truth and preciseness in the retrieval of land surface temrpature is of import to supply possible land surface temperature and dependable information on quality of informations. Long term proof of land surface temperature is necessary to place the jobs in the informations and to work out these jobs by bettering land surface temperature algorithm. The most predictable method which is used for the proof of land surface temperature from satellite informations is to compare satellite informations with land measuring performed at field site with satellite flyover, this method is known as temperature based method ( T-Based ) . Homogeneous field country is necessary for measuring of point based to kilometers, to detect land surface temperature on several points in the field, to stand for land surface temperature over the instantaneous field of position of orbiter detector. Validation of land surface temperature is limited for heterogenous surfaces on this spacial graduated table, such as silt playas, lakes and agricultural Fieldss ( Wan et.al. , 2000 & A ; 2004 ; Coll et.al. , 2005 ) .

Land surface temperature is most of import factor among all the land surface temperature parametric quantities commanding chemical, physical and biological procedures in the Earth system, it normally place as skin temperature of earth surface ( Qin & A ; Karnieli,1999 ) . Because the surface of Earth is non-isothermal and heterogenous in instantaneous field of position ( IFOV ) , representation of land surface temperature in the pel is indispensable measure, so it is define as entire land surface temperature ( Dad et.al. , 2002 ; Norman & A ; Becker 1995 ) .

In the natural philosophies of land surface processes on regional and planetary graduated table land surface temperature is a cardinal parametric quantity because it is a good index of energy balance and is known as nursery gas consequence. Land surface temperature is used to unite the consequences of surface and atmosphere interaction and energy fluxes between the ambiance and land. Hence it is used in different field of natural surveies such as ecological, hydrological, clime and biogeochemical surveies. In the planetary clime alteration snow and ice surface temperature plays a cardinal function in our heat budget in the polar part. Due to the addition in green house gas and clime alterations in the polar part, we can happen out the reply of inquiry generated from these procedures, By utilizing long term orbiter derives land surface temperature, such as proof of land surface temperature by utilizing MODIS and unmoved temperature. Furthermore, land surface temperature derived from satellite informations may be used to better the methods of rating and theoretical accounts of land surface energy balance, canopy temperature and bare dirt temperature may be used to gauge surface heat fluxes between the ambiance and land. Additional, the higher land surface temperature in summer monsoon indicated by atmospheric general circulation theoretical account ( GCM ) simulation. The most effectual correlativity between green house gas consequence and land surface temperature is due to the radiative transportation correlativity based on the land surface temperature informations. In the field of agribusiness H2O demands for wheat can besides be evaluated by the canopy temperature. Finally the radiation emitted from the Earth surface need accurate computation of surface emissivity.

The planetary meteoric theoretical account is one of the most of import applications used for retrieval of land surface temperature signifier orbiter informations. Furthermore due to the importance of retrieval of LST, the surface emissivity can be used to separate the flora. In the procedures of land screen and set down cover-change analysis remotely sensed land surface temperature is used, and is besides used to bring forth satellite informations merchandises such as MODIS land cover merchandise. Soil wet can besides be proctor and estimated by land surface temperature.

Land measuring is used for the proof of land surface temperature derived from retrieval of different orbiter detectors informations, to avoid uncertainness due to spacial heterogeneousness this procedure is largely perform on big graduated table, level and homogenous trial sites ( Synder et.al. , 1997 ; Wan, 1999 ) . For heterogenous and assorted pels the retrieval of land surface temperature is really hard, uncertainness in land surface temperature is due to heterogeneousness ( Moran et.al. , 1997 ) .

Remote feeling for proof of Land surface temperature:

The cognition of planetary land imaging systems comes from old surveies indicate that indicate that proof is important for precise and realistic merchandise processs ( Justice et.al. , 1994 ; Cihlar et.al. , 1997 ) . The commission on Earth Observing Satellite ( CEOS ) working group on Calibration and proof ( WGCV ) defines proof as “ the procedure of measuring by independent means the quality of the information merchandises derived from the system outputs ” ( Justice et.al. , 2000 ) .

Global proof of land remote feeling merchandises is complicated by multiple factors, including trouble in mensurating land surface variables over the size of a orbiter pel, natural mistakes in orbiter informations standardization, cloud showing, atmospheric rectification, georegistration and the impossibleness and disbursal of field informations over a big figure of different ground/ atmosphere combinations over sufficiently long clip graduated table. These restrictions have hence limited careful proof attempts to several intensive field runs ( Jeffery et.al. , 2002 ) .

Thermal remote feeling method is used for earth surface spacial variableness and cyclicities. However, the rectification for the consequence cause by atmosphere, particularly surface emissivity and atmospheric H2O bluess, retrieval of land surface temperature from different orbiter informations is used, which can be varies spatially for both surface screen and type ( Coll et.al. , 2005 ) . In last two decennary several attacks developed for retrieval of land surface temperature signifier thermal infrared informations ( Dash et.al. , 2002 ) . All these techniques used for land surface temperature must be validated with unmoved temperature. Measuring the land surface temperature on land is really hard procedure after completion of measuring we can compare it with satellite informations. Validation site for utilizing land surface temperature must be homogeneous screen in term of surface emissivity and surface temperature, and unmoved measuring must be larger than the pel size ( Slater et.al. , 1996 ; Wan et.al. , 2002 ) . Within one pel size both spacial variableness for temperature and emissivity is relatively little. Water organic structures such as lakes and reservoirs are used for expressed standardization of orbiter thermal infrared radiometer, to minimise the variableness of surface temperature and emissivity. Conversely, we consider that proof of operational land surface temperature algorithms is on existent land surfaces. Different types of land surfaces are suited for proof of land surface temperature such as bare surfaces, vegetated surface and comeuppances.

In order to develop uncertainness information on EOS land merchandises multiple techniques will be used. The methods include comparing with informations from airborne, comparing with unmoved informations, analysis of tendencies in merchandises i.e. spacial and temporal, analysis of procedure theoretical accounts i.e. clime theoretical account and other spaceborne detectors i.e. AVHRR and GEOS.

For proof of satellite merchandise with land measuring there are different databases used in last two decennaries. The field measuring is used for the proof of land surface temperature derived from satellite remote feeling detectors for different field sites in Australia e.g. , National Oceanic and Atmospheric Administration ( NOAA ) and Advanced really high declaration Radiometer ( AHRR ) , in this field run unmoved measuring is collected along the twelvemonth, and so used for the proof of land surface temperature merchandise ( Prata, 2003 ) . For the proof of terra MODIS land surface temperature little databases were used. The present work is the part of bing databases used for the proof of land surface temperature derived from different satellite merchandise. For this intent the experimental site of Leicester University in Wicken fen country is used for the proof of land surface temperature. Land measurings were taken at the same time to forenoon flyover of Aqua orbiter during the summer 2010. Although land surface temperature variableness is smaller at dark, proof of land surface temperature from satellite merchandises of land surface temperature should be at twenty-four hours clip.

In this present survey we used land measuring for the proof of land surface temperature derived from MODIS informations utilizing split window algorithms. Split window algorithm was foremost used for sea surface temperature, and so used for land surface temperature to take emissivity consequence into history, split window algorithm is the most of import technique used for land surface temperature on regional and planetary graduated table ( Becker & A ; Li, 1995 ) . When the surface is heterogenous in term of both surface temperature and emissivity, Land surface temperature estimation from satellite thermic infrared radiometer is more hard so sea surface temperature in heterogenous land surfaces both in footings of surface emissivity and temperature.

Performance of MODIS TIR sets

The first Earth detecting system ( EOS ) moderate declaration spectrometer ( MODIS ) was successfully launched on December 1999, and provides new chances for planetary surveies of different procedures such as land, ocean and atmosphere ( King et.al. , 1992 ; Justice et.al. , 1998 ; Esaias et.al. , 1998 ) , and for satellite measuring of planetary land surface temperature procedure. MODIS is most suited for atmospheric, land and ocean survey because of its high radiometric declaration, planetary coverage and dynamic scopes, and in multiple thermic infrared sets it is used for accurate standardization for land surface temperature, sea surface temperature and atmospheric belongingss. There are different set which are used for different intents particularly band 21 is used to fire sensing ( Kaufman et.al. , 1998 ) , band 26 is used to observe circus clouds ( Gao & A ; Kaufman, 1995 ) . All other thermic infrared channels are used for H2O vapour profiles and for atmospheric temperature retrieval Smith et Al ( 1985 ) . Retrieval of surface emissivity, temperature and atmospheric effects thermic infrared sets ( TIR ) 20, 22, 23,29,31,32 and 33 will be used ( Wan & A ; Li, 1997 ) .

MODIS land Surface temperature Merchandises

MODIS LST merchandises are produced in a sequence ; the first level-2 merchandise of MODIS LST ( MOD11_L2 ) is retrieved with generalised split window algorithm at 1-Km spacial declaration for swath ( Wan & A ; Dozier, 1996 ) and is available from LPDAAC.

Second level-3 MODIS LST merchandise, MOD11A1 at a declaration of 1 Km is a tile of day-to-day LST merchandise ; it is constructed with consequences in the level-2 merchandises by mapping the pels from the level-2 merchandise for a twenty-four hours on the sinusoidal projection.

The 3rd merchandise is MOD11B1it is generated by the day/night LST algorithm ; it is a tile of day-to-day LST and emissivity at 5 Km spacial declaration ( Wan & A ; Li, 1997 )

The 4th merchandise, MOD11A2, is for the 8-day LST is produced by averaging the MOD11A1 merchandise in a period of 8 yearss. These two merchandises MOD11A1 and MOD11B1 daily LST are used to deduce other LST merchandises that are daily, 8 yearss, and monthly planetary LST merchandises in geographic projection of Climate Modelling Grid ( CMG ) cells.

The level-2 MOD11_L2 LST is generated utilizing the MODIS detector glow informations merchandise ( MOD021KM ) , the atmospheric temperature and H2O vapour merchandise ( MOD07_L2 ) , the cloud mask merchandise ( MOD35_L2 ) , the geo location merchandise ( MOD03 ) , the snow merchandise ( MOD10_L2 ) and quarterly land-cover merchandise ( MOD12Q1 ) . MOD11_L2 LST merchandise is generated for all swaths acquires at twenty-four hours and dark clip on the Earth for complete planetary coverage. This level_2 merchandise contains nine scientific informations sets ( SDSs ) : land surface temperature ( LST ) , Latitude, Longitude, QC for quality confidence ( QA ) control, position angle, Errors LST, Emis_31 and Emis_32.

Land surface temperature and emissivity Merchandises

Name

Platform

MODIS merchandise

Raster type

Spectral declaration ( M )

Temporal

Coarseness

MOD11_L2

Terra

Land Surface Temperature & A ; Emissivity

Swath

1000m

5 Min

MYD11_L2

Greenish blue

Land Surface Temperature & A ; Emissivity

Swath

1000m

5 Min

MOD11A1

Terra

Land Surface Temperature & A ; Emissivity

Tile

1000m

Daily

MYD11A1

Greenish blue

Land Surface Temperature & A ; Emissivity

Tile

1000m

Daily

MOD11A2

Terra

Land Surface Temperature & A ; Emissivity

Tile

1000m

8 Dayss

MYD11A2

Greenish blue

Land Surface Temperature & A ; Emissivity

CMG

1000m

8 Dayss

MOD11B1

Terra

Land Surface Temperature & A ; Emissivity

CMG

6000m

Daily

MYD11B1

Greenish blue

Land Surface Temperature & A ; Emissivity

CMG

6000m

Daily

MOD11C1

Terra

Land Surface Temperature & A ; Emissivity

CMG

5600m

Daily

MYD11C1

Greenish blue

Land Surface Temperature & A ; Emissivity

CMG

5600m

Daily

MOD11C2

Terra

Land Surface Temperature & A ; Emissivity

CMG

5600m

8 yearss

MYD11C2

Greenish blue

Land Surface Temperature & A ; Emissivity

CMG

5600m

8 yearss

MOD11C3

Terra

Land Surface Temperature & A ; Emissivity

CMG

5600m

Monthly

MYD11C3

Greenish blue

Land Surface Temperature & A ; Emissivity

CMG

5600m

Monthly

Method for land surface temperature remote feeling

In distant detection of land surface temperature figure of methods are published in the literature and used for the proof of land surface temperature from satellite merchandises. By utilizing accurate radiative transportation theoretical account we can recover land surface temperature from individual infrared channel, if temperature/ H2O profile is given by orbiter sounding and surface emissivity is known ( Price, 1983 ; Susskind et.al. , 1984 ; Chedin et.al. , 1985 ; Ottle et.al. , 1992 ) .

For the rectification of atmospheric surface emissivity effects land surface temperature surface emissivity must be known when split-window algorithm is used for atmospheric and surface emissivity effects based on the differential atmospheric soaking up in 10-13 um split window, split window algorithm can be used to better the truth of LST retrieval column H2O vapour without the cognition of atmospheric temperature/ H2O vapour profile ( Price, 1984 ; Kerr et.al. , 1992 ; Ottle & A ; Stoll 1993 ; Prata 1994 ; Wan & A ; Dozier, 1996 ) . In the truth of split window algorithm and individual channel methods truth of surface emissivity is really of import. In semi-arid and waterless part surface emissivity vary with clip and location these methods do non work in these parts.

Multi-spectral Thermal infrared information is used to pull out surface emissivities from different methods such as mention channel methods ( Kahle et.al. , 1980 ) , emissivity standardization methods ( Gillespie, 1985 ; Realmuto, 1990 ) , temperature independent spectral indices methods ( TISI ) ( Becker & A ; Li, 1990 ) , Spectral ratio method ( Watson, 1992 ) , and alpha residuary method ( Kealy & A ; Gabell, 1990 ) when compare all these methods with thermic infrared multispectral scanner method ( TIMS ) information uncertainnesss from ambiance are shows in all these methods ( Li et al, 1999 ) .

Accurate atmospheric temperature / H2O vapour profile is necessitating for all these above methods except split window algorithm method. In atmospheric profile all these methods depend on used for mistakes in emissivity and retrieval land surface temperature depend on uncertainnesss. In atmospheric H2O bluess big figure of fluctuations present on both temporal and spacial graduated table.

MODIS land surface temperature Algorithm

Basic consideration

Land surface temperature is retrieved from MODIS TIR merely in clear sky status, because TIR signals can non perforate clouds and the chance of cloudy status is frequently larger than 50 % at the regional and planetary graduated tables, in the LST processes cloudy pels must be skipped.

LST is defined by the radiation emitted by the land surface observed by MODIS at instant screening angles. Land surface temperature here is soil surface in au naturel dirt and canopy in vegetated countries. Due to weak sprinkling of TIR signals in clear sky status, instant MODIS thermal infrared informations collected for one sing angle do non incorporate information for another sing angle. A different algorithm used for proof of land surface temperature is as fallows.

Generalized Split window algorithm

In generalised split window algorithm LST of clear sky MODIS pel is retrieved from brightness temperatures in Bands 31 and 32 ( Wan and Dozier, 1989 ) . The major difference between this method and others are precise atmospheric profile is non necessary, Pixel by pel radiative transportation simulation is non necessary, and surface emissivity is of import for truth in this method. This method need really less computing clip because of utilizing simple signifier. For MODIS land surface temperature algorithm this method is proposed a first method. In Variation in LST, emissivity and atmosphere, generalized split window algorithm is used and is depend on the undermentioned consideration such as 1 ) in both horizontal and perpendicular way H2O vapour profile is extremely variable with clip, and is used to mensurate humidness profile non more than 10 % 2 ) land surface temperature and surface air temperature has really less relation with each other, so that land surface temperature is varies with clip and part, for different land screen types difference between both twenty-four hours and dark temperature may be larger than 10° degree Celsiuss ( Betts et.al. , 1996 ) . In MODIS bands 31 and 32 the emissivity of most land screen type is stable at certain parts. Pixel with sing angle of 45° is suited for LST algorithm, because at larger graduated table largely accuracy acquire hapless. In order to acquire planetary coverage of land surface temperature it is better to develop algorithm for whole sing angle.

The generalised split window algorithm ( Wan and Dozier, 1996 ) in signifier

Ts = C + ( A1 + A2 11-?„/ ?„ + A3 a?†?„/ E ^2 Aµ are ) T11 Aµ + T12 Aµ /2

+ ( B1 + B2 1- ?„ / ?„ + B3 a?† ?„ / ?„^2 ) T11 Aµ – T12 Aµ /2

Where vitamin E = 0.5 ( ?„ 11 Aµ + ?„ 12 Aµ ) and Delta ?„ = ?„ 11 Aµ – ?„ 12 Aµ and is known as mean of surface emissivity in sets 31 and 32. In these two sets T11 and T12 is the brightness temperature. C, Ai and Bi, I = 1, 2, 3 are coefficient in this signifier. In order to accomplish truth of 1° K LST is see for sing angle and atmospheric column H2O vapour. Land surface temperature algorithm is used to better generalised split window algorithm such as 1 ) position -angle Dependence, 2 ) column H2O vapour dependance and 3 ) dependance on the atmospheric lower boundary temperature. Set of sing angles covering the whole MODIS swath and is kept in one dimension of LUTs, so that pels on sing angle with higher truths can be retrieved by land surface temperature, set of overlapping period of column H2O bluess are in another dimension of LUTs, so that in MODIS LST merchandise information of H2O vapour can be used for scope of H2O vapour instead than it its values. Likewise, in order to better truth in LST retrieval MODIS merchandises gives us information about atmospheric lower boundary temperature ( Tair ) . Both surface and air temperature can be used to better truth in land surface temperature.

Day/Night algorithm

A natural philosophies based day/night algorithm is used for MODIS informations with seven thermal infrared sets to recover temperature and surface emissivity at 5-km declaration, such as sets 20,22,23,29, and 31-33. The retrieval of surface emissivity and temperature the day/night algorithm is the first operational algorithm capable of seting both H2O vapor profile and atmospheric temperature uncertainty ( Ma et.al. , 2000 ; Wan et. al. , 2002 ) . MODIS information is used in seven sets for brace of twenty-four hours and nighttimes, we have 14 observations. Maximum of 14 unknown variables present in day/night algorithm. Surface temperature and emissivities include in surface variables. In atmospheric temperature/water vapour retrieval big mistakes occur in surface emissivity because of uncertainnesss near to set down surface and ambiance ( Plokhenko & A ; Menzel, 2000 ) . These mistakes occur in the form of values of temperature in surface degree, column H2O vapour and humidness profiles. At the surface of anisotropic factors of solar beam BRDF there is merely one unknown variable left. ( Synder et al, 1997 ) For most tellurian stuff strong fluctuation occur in surface coefficient of reflection, this is shown by Bidirectional coefficient of reflection measuring of dirt and sand, in the scope of 3.3 to 4.2 um wavelength fluctuation is really little in BRDF anisotropic factor. Therefore for sets 20, 22 and 23 we can utilize individual anisotropic factor. Least-square method is used to work out these 14 nonlinear equations in this day/night algorithm ( Wan & A ; Li, 1997 ) . When we consider angular fluctuation in surface emissivity we can divide whole MODIS scope into sub-ranges, in each of these sub ranges we can utilize one emissivity.