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1 ====================================================================== |
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2 R E A D M E . P R O C E S S D A T A |
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3 doc: Tue May 15 18:49:00 2012 |
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4 dlm: Fri Jun 15 07:24:53 2012 |
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5 (c) 2012 A.M. Thurnherr |
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6 uE-Info: 144 38 NIL 0 0 72 75 2 8 NIL ofnI |
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7 ====================================================================== |
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8 |
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9 =Overview= |
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10 |
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11 This README describes how to obtain profiles of vertical shear and |
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12 velocity from CTD/LADCP data. It assumes that all of the required |
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13 software has been installed (see [README.Install]). |
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14 |
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15 The re-implemented shear method software provides two commands: |
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16 |
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17 [LADCPproc] This utility produces LADCP shear data from a raw ADCP |
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18 data file and the corresponding CTD time series. |
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19 Additionally, it can create profiles of acoustic |
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20 backscatter, as well as BT-referenced velocity |
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21 profiles near the seabed from downlooking ADCPs. |
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22 |
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23 [LADCPintsh] This utility produces profiles of horizontal velocity |
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24 from the [LADCPproc] shear output. BT profiles (from |
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25 [LADCPproc] or from the LDEO_IX inversion software) or |
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26 SADCP profiles (manually constructed) can be used to |
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27 reference the velocity profiles. |
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28 |
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29 For non-standard processing, the shear output from [LADCPproc] can be |
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30 post-edited before gridding, e.g. in order to filter data collected at |
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31 very shallow depths when the ADCP may be affected by the magnetic field |
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32 of the surface vessel (see [README.PostEdit] for details). |
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33 |
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34 |
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35 =DATA REQUIREMENTS= |
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36 |
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37 ADCP DATA: The software reads binary RDI BB ADCP files from both down- |
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38 and upward-looking ADCPs. Clock setting of the ADCP is not important. |
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39 |
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40 CTD DATA: LADCP processing requires a CTD-derived time series of |
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41 elapsed time, pressure, temperature and salinity. A time resolution of |
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42 1Hz is recommended. The software is capable of reading both binary and |
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43 ASCII SeaBird .cnv files with lat/lon information in the header and |
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44 with the following fields: timeS, prDM, t090C and/or t190C, sal00 |
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45 and/or sal11. Alternatively, the CTD time series can be supplied as an |
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46 arbitrary headerless ASCII CTD file with the same information, as |
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47 described in [LADCPproc.defaults]. |
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48 |
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49 |
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50 =CALCULATE LADCP SHEAR PROFILE= |
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51 |
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52 The following simple example shows how to create separate shear profiles |
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53 from an upward- and a downward-looking ADCP, as well as a BT-referenced |
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54 velocity profile near the seabed: |
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55 |
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56 Input files: |
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57 001DL000.000 downlooker ADCP file |
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58 001UL000.000 uplooker ADCP file |
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59 001.cnv CTD file |
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60 |
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61 LADCPproc -p 001DL.sh -b 001.BT 001DL000.000 001.cnv > /dev/null |
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62 - this example creates two files, 001DL.sh (shear profiles) and |
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63 001.BT (bottom-track data) |
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64 - the default output (STDOUT) from [LADCPproc] is a list of |
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65 valid shear samples, which is ignored (sent to /dev/null) in |
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66 this example |
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67 - it is recommended that the diagnostic output (STDERR) is |
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68 captured in a log file; refer to the manual of your shell on |
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69 how to accomplish this |
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70 |
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71 LADCPproc -p 001UL.sh 001UL000.000 001.cnv > /dev/null |
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72 - this example creates one file, 001UL.sh (shear profiles) |
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73 |
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74 |
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75 In this simple example, processing is carried out with standard |
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76 parameters. Some of the important parameters can be modified with |
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77 [LADCPproc] options, which are listed when [LADCPproc] is ran without |
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78 input parameters. The following are the most important [LADCPproc] |
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79 options: |
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80 -d generate diagnostic output (recommended) |
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81 -r use RDI BT data instead of echo amplitudes to find |
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82 seabed and determine CTD velocity |
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83 -o <dz> output grid resolution (defaults to 5m) |
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84 -p <shearprof> generate shear profile output |
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85 -b <btm_track> generate BT output |
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86 -s <setup_file> read additional non-default processing parameters |
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87 from <setup_file> |
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88 |
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89 However, there are many more processing parameters than can be modified |
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90 with options --- a full list with comments can be found in |
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91 [LADCPproc.defaults]. To change any of the default parameter values, |
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92 create a perl-file with variable assignments (see [LADCPproc.defaults] |
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93 for syntax) and use the -s <setup_file> option in [LADCPproc]. |
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94 |
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95 |
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96 =CALCULATE LADCP VELOCITY PROFILE= |
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97 |
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98 Given the output from the above steps, different full-depth velocity |
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99 profiles can be produced as follows: |
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100 |
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101 LADCPintsh 001DL.sh > 001DL.bc |
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102 - this creates baroclinic (zero vertical mean) velocity profile |
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103 from the DL shear data |
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104 |
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105 LADCPintsh -r 001.BT 001DL.sh > 001DL.vel |
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106 - this creates a BT-referenced absolute velocity profile from |
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107 the DL shear data |
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108 |
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109 LADCPintsh -r 001.BT -u 001UL.sh 001DL.sh > 001.vel |
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110 - this creates a BT-referenced absolute velocity profile from |
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111 the combined DL/UL shear data |
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112 |
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113 It is also possible to use SADCP data to reference the velocity |
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114 profiles, although it is up to the user to create an input data file |
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115 in one of the supported formats. Note that it is *not* possible to use |
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116 multiple simultaneous referencing constraints with [LADCPintsh]. |
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117 |
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118 The following are common [LADCPintsh] options: |
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119 -u use uplooker shear (in addition to downlooker, |
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120 which is always used) |
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121 -r <file> use reference-velocity data to reference baroclinic |
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122 velocity profiles; the following file formats |
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123 are supported 1) bottom-track output produced by |
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124 the -b option of [LADCPproc], 2) bottom-track |
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125 output produced by the LDEO processing software |
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126 (.bot files). SADCP data can be used, too, but |
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127 they have to be supplied in one of the two |
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128 supported file formats. |
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129 -n <samp> set minimum number of shear samples to use |
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130 -m <samp> set minimum BT samples to use |
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131 |
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132 |
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133 =QUALITY CHECKS= |
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134 |
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135 After processing, the quality of the resulting profiles must be |
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136 assessed. The following steps are recommended: |
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137 |
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138 1) Compare the down- and up-cast profiles of velocity. Vertical |
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139 velocity is particularly useful in this context as problematic casts |
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140 often show a striking "X" pattern. |
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141 |
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142 2) Inspect the standard deviation profiles of the binned shear and |
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143 determine (by comparison with similar data) whether the standard |
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144 deviations have the correct magnitude. |
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145 |
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146 3) Calculate and compare independent solutions from the uplooker and |
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147 downlooker data. This will only validate the baroclinic velocities (i.e. |
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148 the vertical shear). |
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149 |
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150 4) Compare to velocity profiles calculated with different software (e.g. |
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151 with the LDEO_IX velocity inversion code). |