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Appendix F: ATREM Pseudo-code

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Appendix F: ATREM Pseudo-code

GLOBAL VARIABLES AND THEIR DESCRIPTIONS

INTEGER

ERRNO Error number for error control (1=at least one invalid input)

FILEMODE Switch to determine whether to output to file(1) or memory(0)

FPIN File pointer for input file (used in conjunction with C)

FPOCUB File pointer for output cube file (used in conjunction with C)

FPOH2O File pointer for water vapour file (used in conjunction with C)

HDREC Header size of AVIRIS Data File

IAER Aerosol Model Number (0-3)

ICH4 switch for including ch4 in transmission calculations (0,1)

ICO switch for including co in transmission calculations (0,1)

ICO2 switch for including co2 in transmission calculations (0,1)

IDAY # of days that have passed during the year

IDY day

IED1 ending wavelength index for 3-channel ratioing, window 1

IED1P14 ending wavelength index for 1.14 um water vapour band

IED2 ending wavelength index for 3-channel ratioing, window 2

IED3 ending wavelength index for 3-channel ratioing, window 3

IED4 ending wavelength index for 3-channel ratioing, window 4

IEDCAL

IEDP94 ending wavelength index for 0.94 um water vapour band

IEND

IEND2

IH hour

IH2OLQ Flag for including liquid water vapour in calculations

IH2OVP switch for including h2o in transmission calculations (0,1)

IM minute

IMN month

IN2O switch for including n2o in transmission calculations (0,1)

IO2 switch for including o2 in transmission calculations (0,1)

IO3 switch for including o3 in transmission calculations (0,1)

IS seconds

IST1 starting wavelength index for 3-channel ratioing, window 1

IST1P14 starting wavelength index for 1.14 um water vapour band

IST2 starting wavelength index for 3-channel ratioing, window 2

IST3 starting wavelength index for 3-channel ratioing, window 3

IST4 starting wavelength index for 3-channel ratioing, window 4

ISTART

ISTRT2

ISTCAL

ISTP94 starting wavelength index for 0.94 um water vapour band

IYR year

JA output parameter from a table searching routine

MODEL Atmospheric Model Number (1-7)

NOBS # of observations in wavelength file

NATOT # of channels for AVIRIS grating Spectrometer A

NB # OF boundaries in atmospheric model

NB1 # of points to average for 1st window (0.94um channel)

NB2 # of points to average for 2nd window (0.94um channel)

NBP94 # of points to average for absorption feature

NB3 # of points to average for 3rd window (1.14um channel)

NB4 # of points to average for 4th window (1.14um channel)

NB1P14 # of points to average for absorption feature

NBANDS # of bands in AVIRIS Data File

NBTOT # of channels for AVIRIS grating Spectrometer B

NCTOT # of channels for AVIRIS grating Spectrometer C

NCV

NCV2

NCVHAF

NCVHF2

NCVTOT

NCVTT2

NDTOT # of channels for AVIRIS grating Spectrometer D

NGASTT total number of gases

NH2O number of water vapour values

NL NL=NB-1

NLINES # of lines in AVIRIS Data File

NO3PT # of ozone absolute coefficients points

NPSHIF # of points between 0.4 and 0.6 um

NSAMPS # of samples in AVIRIS Data File

REFIMG Memory file pointer for reflectance image

SORDER Storage order of AVIRIS DATA (0=BSQ, 1=BIP, 2=BIL)

WVIMG Memory file pointer for water vapour image

 

REAL

BUFA intermediate parameter for calculating water vapour spectra

BUFB intermediate parameters for calculating water vapour spectra

CLMVAP Column water vapour amount in cm

DLT Spectral Resolution (nm)

DLT2 Resolution of output spectra (0-100 nm)

DLTNEW Spectral Resolution (um) [DLT/1000]

DP

DWAVLN interval (or point spacing) of band model parameters

FINST2

FINSTR Gaussian instrumental function for each AVIRIS channel

FWHM(512) FWHM array for storing FWHM values for each channel

GCH4 Geometric Factor for Methane

GCO Geometric Factor for Carbon Monoxide

GCO2 Geometric Factor for Carbon Dioxide

GGEOM Geometric Factors for Gases

GGH20(60) Geometric Factors for water vapour

GN2O Geometric Factors for Nitrous Oxide

GO2 Geometric Factor of Oxygen

GO3 Geometric Factor of Ozone

H(15) Atmospheric Model Altitude (km) for each boundary

HSURF Mean surface elevation of image [0 - H(max)]

OBSPHI Observational Azimuth Angle

OBSZNI Observational Zenith Angle

P(15) Atmospheric Model Pressure (atm) for each boundary

PM

Q # of molecules about the surface at 1 atm (molecules/cm^2)

R094 channel ratio for .94 um region *

R114 channel ratio for 1.14 um region *

RLQAMT liquid water amount (cm)

SCALEF scaling factor for output reflectance values [1-32000]

SOLAZ Solar Azimuth Angle

SOLZNI Solar Zenith Angle

T(15) Atmospheric Model Temperature (Kelvin) for each boundary

TAER55 Aerosol Optical Depth at 0.55um for 5S model

TM(15) Median Temperature between Atmospheric Model Boundaries

TOTLO3 Total OZONE in sun-surface ray path

TPVMR(6,41) 2D array of values for six standard atmospheric models

TRAN Transmittances of different gases

TRNCAL atmospheric transmittance spectra

TRNSTD Transmittances used in internal calculations

V Visibility

VAPTT geometrically adjusted water vapour total

VEND ending wavelengths in internal calculations.

VMIN minimum wavelength to calculate atmospheric transmissions

VMR(15) Atmospheric Model Volume Mixing Ratio (ppm of each layer)

VMRM(15)

VRTO3 Column ozone amount (0.1 - 0.6)

VSTART starting wavelengths in internal calculations

WAVAVR(512) wavelengths of the AVIRIS channel centers (um)

WAVSTD(1050) Wavelengths used in internal calculations

WNDOW1 Midpoint of first window (0.94um channel) [0.6-2.5]

WNDOW2 Midpoint of second window (0.94um channel) [0.6-2.5]

WP94C Midpoint of water vapour absorption feature [0.6-2.5]

WNDOW3 Midpoint of third window (1.14um channel) [0.6-2.5]

WNDOW4 Midpoint of fourth window (1.14um channel) [0.6-2.5]

W1P14C Midpoint of 1.14um absorption feature [0.6-2.5]

WT1 Relative weight for window1

WT2 Relative weight for window2

WT3 Relative weight for window3

WT4 Relative weight for window4

XLATD Latitude, degrees

XLATM Latitude, minutes

XLATS Latitude, seconds

XLONGD Longitude, degrees

XLONGM Longitude, minutes

XLONGS Longitude, seconds

YY

 

CHARACTER*1

LATHEM Latitude, hemisphere

LNGHEM Longitude, hemisphere

 

CHARACTER*80

FINAV AVIRIS Data File Name

FOCUB Output reflectance cube file name

FOH2O output water vapour filename (512byte header,1band,BSQ)

 

GLOBAL PARAMETER LISTS

IN FORTRAN

AH2O_INIT1: AH2O

APH2O_INIT1: APH2O

BH2O_INIT1: BH2O

BPH2O_INIT1: BPH2O

CHNLRATIO1: R094,R114

ERRORS: ERRNO

GEOMETRY1: SOLZNI,SOLAZ,OBSZNI,OBSPHI,IDAY

GEOMETRY2: GCO2,GO3,GN2O,GCO,GCH4,GO2,GGH2O,TOTLO3,GGEOM

GETINPUT1: IH2OVP,ICO2,IO3,IN2O,ICO,ICH4,IO2

GETINPUT3: H,T,P,VMR,NB,NL,MODEL,IAER,V,TAER55,VRTO3

GETINPUT4: WAVAVR,FWHM

GETINPUT5: NOBS,HSURF,DLT,DLT2

GETINPUT6: WNDOW1,WNDOW2,WP94C,WNDOW3,WNDOW4,W1P14C

GETINPUT7: NB1,NB2,NBP94,NB3,NB4,NB1P14

GETINPUT8: IMN,IDY,IYR,IH,IM,IS

GETINPUT9: XLATD,XLATM,XLATS,LATHEM

GETINPUT10: XLONGD,XLONGM,XLONGS,LNGHEM

GETINPUT11: HDREC,NSAMPS,NLINES,NBANDS,SORDER

GETINPUT12: SCALEF

INIT_SPECCAL1: WAVSTD,TRNSTD

INIT_SPECCAL2: NPSHIF,FINSTR,DWAVLN

INIT_SPECCAL3: IH2OLQ,RLQAMT,NGASTT,NH2O,VSTART,VEND

INIT_SPECCAL4: NO3PT,NCV,NCVHAF,NCVTOT,VMIN,ISTART,IEND

INIT_SPECCAL5: ISTCAL,IEDCAL,DP,PM,TM,VMRM

INIT_SPECCAL6: IST1,IED1,IST2,IED2,ISTP94,IEDP94

INIT_SPECCAL7: IST3,IED3,IST4,IED4,IST1P14,IED1P14

INIT_SPECCAL8: WT1,WT2,WT3,WT4,JA

INIT_SPECCAL9: TRAN,BUFA,BUFB

INIT_SPECCAL10: NCV2,NCVHF2,NCVTT2,ISTRT2,IEND2,FINST2

INIT_SPECCAL11: NATOT,NBTOT,NCTOT,NDTOT

MODEL_ADJ1: CLMVAP,Q

O3CF_INIT1: O3CF

OUTPUT_MODE: FILEMODE

PROCCUBE1: YY

SODLT_INIT1: SODLT

SOGAM_INIT1: SOGAM

SOLAR_IRR1: YIRR

TPVMR_INIT1: TPVMR

TRAN_TABLE1: GH2O,VAPTOT,R0P94,R1P14,TRNTBL

TRANCAL1: TRNCAL,VAPTT

WAVLN_INIT1: WAVLN

 

 

USE WITH C PROGRAMS FOR CUBE I/O

OUTCUBE: FPOCUB,FOCUB,REFIMG

INCUBE: FPIN,FINAV

OUTH2OVAP: FPOH2O,FOH2O,WVIMG

 

 

MAIN PROGRAM

CALL GET_INPUT: obtain information needed to process the AVIRIS data

 

IF NO ERRORS OCCUR in obtaining information

CALL MODEL_ADJ: resets the bottom boundary of the input model if the

surface elevation is greater than 0, and calculates

the column water vapour amount in the selected model.

 

CALL GEOMETRY: calculates the solar and the observational geometric

factors.

 

CALL SSSSS: predicts the satellite signal from 0.25-4.0 um assuming

cloudy atmospheric effects (gaseous absorption by water vapour,

carbon dioxide, oxygen and ozone; scattering by molecules and

aerosols are taken into account). Inhomogeneous ground

condition may be considered.

 

CALL INIT_SPECCAL: Initialises global data for spectrum calculations

 

CALL SOLAR_IRR: Obtain solar irradiances above the atmosphere corresponding

to the measurement time and geographic location.

 

CALL TRAN_TABLE: Generates a table consisting of 60 atmospheric

transmittance spectra at the AVIRIS solar and

observational geometry and with 60 column water vapour

values. This table also include the total amounts of

column water vapour used in the calculations, and the

3-channel ratios calculated from the window and absorption

channels in and around the 0.94 and 1.14um water vapour

bands

 

CALL PROCESS_CUBE: Processes an input cube one spectral slice at a time to

derive surface reflectance for each spectrum and

calculate the column water vapour amount for each pixel.

The derived surface reflectance values are written to

an output image file with the same dimensions as the

input image, and the column water vapour amounts are

written to a separate file as a single channel image.

 

ENDIF

 

END PROGRAM

 

GET_INPUT

LOCAL VARIABLES

INTEGER

ANS Verifier to read next line of input

DIMS(4) Values read from AVIRIS Data file when file first opened

Header size, samples, lines, bands

ST_ORDER Storage order read from AVIRIS Data file when file first opened

 

CHARACTER*80

FINPWV Wavelength file name

FTPVMR Atmospheric Model File name

FOUT1 Filename for output table, atmos. trans. spectra

 

LOGICAL

GOOD_DATA Logical telling whether data was correctly read in

 

REAL

X Channel Number

 

********************************************************************************

INITIALIZE GOOD_DATA

 

READ in MONTH, DAY, YEAR, HOUR, MINUTE, SECOND

VERIFY

 

READ LATITUDE

VERIFY

 

READ LONGITUDE

VERIFY

 

READ Spectral Resolution

IF Spectral Resolution > 0

IF NOT Valid Value (8-100)

Report Bad Data

ELSE

Initialise FWHM Array

ENDIF

ENDIF

 

READ Wavelength File Name

OPEN File

VERIFY OPEN

ELSE

READ DATA from file

CLOSE File

ENDIF

 

Determine of channel ratio should be read

VERIFY READ

IF READ

READ 0.94um Channel Ratio Parameters

VERIFY

READ 1.14um Channel Ratio Parameters

VERIFY

ELSE

INITIALIZE DEFAULT atmospheric window and wv absorption regions

ENDIF

 

READ atmospheric model to use

VERIFY READ

IF MODEL = 7 (user-defined) THEN

READ Atmospheric Model File name

OPEN Atmospheric Model File

READ Atmospheric Model File

ELSE

Initialise Model Parameters (NB,H,P,T,VMR) from predefined atmos. model array

ENDIF

 

Determine which gases to include in calculations

VERIFY READ

 

READ Total Column Ozone Amount

VERIFY READ

 

READ Aerosol Model and Visibility

VERIFY READ

 

IF no aerosol THEN

V = -1 (set for 5s modeling program)

no optical depth

ELSE

VERIFY Visibility

ENDIF

 

IF no visibility THEN

READ aerosol optical depth

VERIFY READ

ENDIF

 

READ mean surface elevation

VERIFY READ

 

READ file name of AVIRIS Data

CALL OPENINFILE(IRET,DIMS,ST_ORDER)

VERIFY OPEN

 

Determine if cube dimensions should be read in

VERIFY READ

IF read in cube dimensions THEN

READ Header size, samples, lines, bands, and storage order

VERIFY READ

ELSE

USE values read from the file itself

ENDIF

 

READ Output reflectance cube file name

CALL OPENOUTFILE(IRET,512,NSAMPS,NLINES,NBANDS,SORDER)

VERIFY OPEN

 

READ Resolution of output spectra

VERIFY READ

 

READ scaling factor for output reflectance values

VERIFY READ

 

READ output water vapour file name

CALL OPENVAPFILE(IRET,512,NSAMPS,NLINES,1,0)

 

READ filename for output table

OPEN output table file

VERIFY OPEN

 

IF no good data THEN

ERRNO = 1

ELSE

ERRNO = 0

ENDIF

 

RETURN

 

MODEL_ADJ

Local Variables

INTEGER

K Index of HSURF in H

REAL

SL Slant path length

DSLODH =dSL/dH

RE Radius of Earth (m)

TSURF Surface Temperature at H(K) (Linearly interpolated)

VMRS Volume Mixing Ratio at H(K) (Linearly interpolated)

PSURF Surface Pressure at H(K) (Exponentially interpolated)

********************************************************************************

Set RE=6380

Set Q=2.152E25

 

Convert VMR from ppm unit to absolute unit by x 1.E-6

IF Surface Elevation > 0 THEN

Determine location of HSURF in H

Calculate change in model height

Calculate Change in height from surface elevation and location in H

Linearly Interpolate surface temp (TSURF) and VMR (VMRS)

Exponentially Interpolate for surface pressure (PSURF)

Reset Number of boundaries

Reset NL

Re-assign values from bottom up

Zero out pressures and VMRS of top atmospheric layers

ENDIF

 

Calculate Column water vapour amount by boundary and add up

 

RETURN

 

GEOMETRY

LOCAL VARIABLES

REAL

VAPVRT(60)

MD(12) Starting day of the year for the month (ie, June=151)

XLAT Latitude in Decimal Degrees

XLATR Latitude in Radians

XLONG Longitude in Decimal Degrees

XLONGR Longitude in Radians

XH Hours in real

XM Minutes in real

XS Seconds in real

TT Reference Time

DEC Declination of the Sun at time TT

HAZ Hour Angle minus Reference Time

EL Elevation

********************************************************************************

Convert Time of observation to distance in radians rotated by earth

Convert Latitude and Longitude into Radians

Assign Hemisphere to Lat and Long (S=-1;E=-1)

CALL SUNCOR(IDY,IMN,IYR,TT,DEC,HAZ)

CALL HAZEL(HAZ+TT-XLONGR,DEC,SOLAZ,EL,XLATR)

VERIFY ELEVATION

CONVERT Solar Azimuth to Radians

SET observation zenith and azimuth angles to 0; observations are straight down

CALCULATE solar zenith Angle

CALCULATE Gas Geometric Factor

CALCULATE individual Gas Geometric Factors

CALCULATE Total OZONE, ignore the 25 km ozone peak (AVIRIS flies below this)

CALCULATE the 60 water vapour geometry factors

CALCULATE # of days passed during the year the AVIRIS image was taken

 

RETURN

 

INIT_SPECCAL

LOCAL VARIABLES

REAL

FACDLT Factor to multiply DLT by to determine the range used in the

Gaussian function calculation for smoothing spectra

CONST1

CONST2 total area of Gaussian curve

DT small diff. between boundary layer temp and median temp (=TM-T)

DWVAVR Approximate wavelength spacing of AVIRIS data

RNCV

WAVCV

 

********************************************************************************

CALL WAVLN_INIT

SET the Number of column water vapour values

INDICATE if liquid water should be considered in the calculations

SET number of ozone data points

SET constants

CALCULATE FINSTR

DERIVE parameters and arrays to smooth output surface reflectance spectra

SET number of channels of the 4 AVIRIS spectrometers to be used in removing

null AVIRIS radiance values in the overlap portions

SET wv windows to closest AVIRIS wavelength

SET starting and ending wavelength indexes

CALCULATE weights for window and absorption channels

 

INITIALIZE JA for searching water vapour table (TRNTBL)

INITIALIZE WAVSTD (.4-3.0225)

INITIALIZE TRANSMITTANCE TABLE

INITIALIZE VMRM TABLE

CALCULATE median values between the atmos. model boundaries.

 

START TRANSMITTANCE CALCULATIONS LOOP

IF GAS NOT USED ASSIGN 1's to transmittance table for that gas

CALCULATE transmittance of each gas separately

ASSIGN transmittance to transmittance table

END LOOP

 

SOLOR_IRR

REAL

E(1050) Solar Irradiances starting at 0.34

WL Wavelength spectrum

E_SM(1050) Smoothing Irradiance Array

 

 

********************************************************************************

ASSIGN solar irradiances to array E

GENERATE wavelength spectrum (0.3475-2.66 um)

INITIALIZE Smoothing Irradiance Array

INTERPOLATE values of Smoothing Irradiance Array to AVIRIS wavelengths

 

CORRECT for Sun-Earth distance

 

TRAN_TABLE

LOCAL VARIABLES

 

 

********************************************************************************

 

CALCULATE the geometrically adjusted water vapour amount, the channel ratios,

and the transmittance spectrum

CALL TRANCAL

 

WRITE calculated values to file

 

PROCESS_CUBE

c each slice is one line

c each line has nsamples

c each sample has nbands

 

DO for all lines

Read in spectral slice

CALL REFLDRV to create a surface reflectance spectrum

REPLACE reflectance values with the newly found true surface reflectance

STORE water vapour amounts

WRITE slice to output file

END DO

 

WRITE the water vapour image to file