[272] | 1 | ;+ |
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| 2 | ; |
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| 3 | ; @file_comments |
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| 4 | ; get the time axis from a netcdf_file and transforms it in |
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| 5 | ; Julian days of IDL. |
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| 6 | ; |
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| 7 | ; @categories |
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| 8 | ; Read NetCDF file |
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| 9 | ; |
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| 10 | ; @param filename {in}{required}{type=scalar string} |
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| 11 | ; the name of the ncdf_file |
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| 12 | ; |
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| 13 | ; @param cdfid {in}{required}{type=scalar} |
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| 14 | ; the ID of the ncdf_file, which is already open |
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| 15 | ; |
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| 16 | ; @keyword TIMEVAR {type=string} |
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| 17 | ; It define the name of the variable that |
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| 18 | ; contains the time axis. This keyword can be useful if there |
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| 19 | ; is no unlimited dimension or if the time axis selected by default |
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| 20 | ; (the first 1D array with unlimited dimension) is not the good one. |
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| 21 | ; |
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| 22 | ; @keyword CALLER {required}{type=scalar} |
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| 23 | ; Used to specify the error messages. Give the name of the calling |
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| 24 | ; procedure. It can be only 'read_ncdf' or 'scanfile'. |
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| 25 | ; |
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| 26 | ; @keyword ERR |
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| 27 | ; Set this keyword to a named variable in which the value of the error |
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| 28 | ; message will be returned |
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| 29 | ; |
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| 30 | ; @keyword _EXTRA |
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| 31 | ; _EXTRA to be able to call ncdf_getmask with _extra keyword |
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| 32 | ; |
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| 33 | ; @returns |
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| 34 | ; a double 1D array of IDL Julian days |
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| 35 | ; In case of error return -1 if the time dimension was not found |
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[297] | 36 | ; or return -jpt if it as been found that the time dimension size is jpt |
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[272] | 37 | ; |
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| 38 | ; @restrictions |
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| 39 | ; the calendar variable must have the units attribute |
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| 40 | ; following the syntax bellow: |
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| 41 | ; |
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| 42 | ; time_counter:units = "seconds since 0001-01-01 00:00:00" ; |
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| 43 | ; time_counter:units = "hours since 0001-01-01 00:00:00" ; |
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| 44 | ; time_counter:units = "days since 1979-01-01 00:00:00" ; |
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| 45 | ; time_counter:units = "months since 1979-01-01 00:00:00" ; |
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| 46 | ; time_counter:units = "years since 1979-01-01 00:00:00" ; |
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| 47 | ; |
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| 48 | ; @history |
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| 49 | ; August 2007: Sebastien Masson (smasson\@lodyc.jussieu.fr) |
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| 50 | ; |
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| 51 | ; @version |
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| 52 | ; $Id$ |
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| 53 | ;- |
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[327] | 54 | FUNCTION ncdf_gettime, filename, cdfid $ |
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| 55 | , TIMEVAR=timevar, CALLER=caller, ERR=err, _EXTRA=ex |
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[272] | 56 | ; |
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| 57 | compile_opt idl2, strictarrsubs |
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| 58 | ; |
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| 59 | @cm_4cal ; needed for key_caltype |
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| 60 | ; |
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| 61 | inq = ncdf_inquire(cdfid) |
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| 62 | ;---------------------------------------------------- |
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| 63 | ;`find the variable containing the time axis |
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| 64 | ;---------------------------------------------------- |
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| 65 | ; we get its name through the keyword timevar |
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| 66 | IF keyword_set(timevar) THEN BEGIN |
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| 67 | timeid = ncdf_varid(cdfid, timevar) |
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| 68 | IF timeid EQ -1 THEN BEGIN ; the variable is not found |
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| 69 | CASE caller OF |
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| 70 | 'read_ncdf':err = 'No variable ' + timevar + 'found in '+filename+'. Use the TIMESTEP keyword' |
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| 71 | 'scanfile':err = 'No variable ' + timevar + 'found in '+filename+'. We create a fake calendar' |
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| 72 | ENDCASE |
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| 73 | return, -1 |
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| 74 | ENDIF |
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| 75 | timeinq = ncdf_varinq(cdfid, timeid) |
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| 76 | inq.recdim = timeinq.dim[0] |
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| 77 | ncdf_diminq, cdfid, inq.recdim, timedimname, jpt |
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| 78 | ENDIF ELSE BEGIN |
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| 79 | ; we try to find the time axis automatically |
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| 80 | ; we look for the infinite dimension |
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| 81 | IF inq.recdim EQ -1 THEN BEGIN |
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| 82 | CASE caller OF |
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| 83 | 'read_ncdf':err = 'the file '+filename+' as no infinite dimension. !C Use TIMESTEP or TIMEVAR keyword' |
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| 84 | 'scanfile':err = 'the file '+filename+' as no infinite dimension. We create a fake calendar' |
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| 85 | ENDCASE |
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| 86 | return, -1 |
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| 87 | ENDIF |
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| 88 | ncdf_diminq, cdfid, inq.recdim, timedimname, jpt |
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| 89 | ; we look for the variable containing the time axis |
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| 90 | ; we look for the first variable having for only dimension inq.recdim |
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| 91 | timeid = 0 |
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| 92 | REPEAT BEGIN ; As long as we have not find a variable having only one dimension: the infinite one |
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| 93 | timeinq = ncdf_varinq(cdfid, timeid) ; that the variable contain. |
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| 94 | timeid = timeid+1 |
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| 95 | ENDREP UNTIL (n_elements(timeinq.dim) EQ 1 AND timeinq.dim[0] EQ inq.recdim) $ |
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| 96 | OR timeid EQ inq.nvars+1 |
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| 97 | IF timeid EQ inq.nvars+1 THEN BEGIN |
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| 98 | CASE caller OF |
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| 99 | 'read_ncdf':err = 'the file '+filename+' as no time axis variable. !C Use the TIMESTEP keyword' |
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| 100 | 'scanfile':err = 'the file '+fullname+' has no time axis.!C we create a fake calendar ...' |
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| 101 | ENDCASE |
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| 102 | return, -jpt |
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| 103 | ENDIF |
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| 104 | timeid = timeid-1 |
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| 105 | ENDELSE |
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| 106 | ;---------------------------------------------------- |
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| 107 | ; look for attribute units and calendar to know how to compte the calendar |
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| 108 | ;---------------------------------------------------- |
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| 109 | ; no attribute for time variable... |
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| 110 | IF timeinq.natts EQ 0 then begin |
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| 111 | CASE caller OF |
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| 112 | 'read_ncdf':err = 'the variable '+timeinq.name+' has no attribute.!C Use the TIMESTEP keyword' |
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| 113 | 'scanfile':err = 'the variable '+timeinq.name+' has no attribute.!C we create a fake calendar ...' |
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| 114 | ENDCASE |
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| 115 | return, -jpt |
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| 116 | ENDIF |
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| 117 | ; get attributes names |
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| 118 | attnames = strarr(timeinq.natts) |
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| 119 | for attiq = 0, timeinq.natts-1 do attnames[attiq] = strlowcase(ncdf_attname(cdfid, timeid, attiq)) |
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| 120 | ; do we find units attribute? |
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| 121 | IF (where(attnames EQ 'units'))[0] EQ -1 then BEGIN |
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| 122 | CASE caller OF |
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| 123 | 'read_ncdf':err = 'Attribute ''units'' not found for the variable '+timeinq.name+' !C Use the TIMESTEP keyword' |
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| 124 | 'scanfile':err = 'Attribute ''units'' not found for the variable '+timeinq.name+'!C we create a fake calendar ...' |
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| 125 | ENDCASE |
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| 126 | return, -jpt |
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| 127 | ENDIF |
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| 128 | ; Is attribute "calendar" existing? |
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| 129 | ; If no, we suppose that the calendar is gregorian calendar |
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| 130 | ; |
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[344] | 131 | ncdf_getatt, cdfid, timeid, calendar = calendar, units = value |
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| 132 | CASE calendar OF |
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| 133 | 'noleap':key_caltype = 'noleap' |
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| 134 | '360d':key_caltype = '360d' |
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| 135 | 'greg':key_caltype = 'greg' |
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| 136 | ENDCASE |
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[272] | 137 | ;---------------------------------------------------- |
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| 138 | ; decode units attribute |
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| 139 | ;---------------------------------------------------- |
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| 140 | ; |
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| 141 | ; time_counter:units = "seconds since 0001-01-01 00:00:00" ; |
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| 142 | ; time_counter:units = "hours since 0001-01-01 00:00:00" ; |
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| 143 | ; time_counter:units = "days since 1979-01-01 00:00:00" ; |
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| 144 | ; time_counter:units = "months since 1979-01-01 00:00:00" ; |
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| 145 | ; time_counter:units = "years since 1979-01-01 00:00:00" ; |
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| 146 | ; |
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| 147 | ; we decript the "units" attribute to find the time origin |
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| 148 | value = strtrim(strcompress(string(value)), 2) |
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| 149 | words = str_sep(value, ' ') |
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| 150 | units = words[0] |
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| 151 | units = strlowcase(units) |
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| 152 | IF strpos(units, 's', strlen(units)-1) NE -1 THEN units = strmid(units, 0, strlen(units)-1) |
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| 153 | IF strpos(units, 'julian_') NE -1 THEN units = strmid(units, 7) |
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| 154 | IF units NE 'second' AND units NE 'hour' AND units NE 'day' $ |
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| 155 | AND units NE 'month' AND units NE 'year' THEN BEGIN |
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| 156 | CASE caller OF |
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| 157 | 'read_ncdf':err = 'time units does not start with seconds/hours/days/months/years !C Use the TIMESTEP keyword' |
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| 158 | 'scanfile':err = 'time units does not start with seconds/hours/days/months/years !C we create a fake calendar ...' |
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| 159 | ENDCASE |
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| 160 | return, -jpt |
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| 161 | ENDIF |
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| 162 | IF stregex(value, '[^ ]* since ([0-9]){1,4}-([0-9]){1,2}-([0-9]){1,2}.*', /boolean) EQ 0 THEN BEGIN |
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| 163 | CASE caller OF |
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| 164 | 'read_ncdf':err = 'attribute units of time has not the good format: [^ ]* since ([0-9]){1,4}-([0-9]){1,2}-([0-9]){1,2}.*!C Use the TIMESTEP keyword' |
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| 165 | 'scanfile':err = 'attribute units of time has not the good format: [^ ]* since ([0-9]){1,4}-([0-9]){1,2}-([0-9]){1,2}.*!C we create a fake calendar ...' |
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| 166 | ENDCASE |
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| 167 | return, -jpt |
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| 168 | ENDIF |
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| 169 | start = str_sep(words[2], '-') |
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| 170 | ;---------------------------------------------------- |
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| 171 | ; compute time axis |
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| 172 | ;---------------------------------------------------- |
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| 173 | ncdf_varget, cdfid, timeid, time |
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| 174 | time = double(time) |
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| 175 | case units of |
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| 176 | 'second':time = julday(start[1], start[2], start[0], 0, 0, 0)+time/86400.d |
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| 177 | 'hour':time = julday(start[1], start[2], start[0], 0, 0, 0)+time/24.d |
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| 178 | 'day':time = julday(start[1], start[2], start[0], 0, 0, 0)+time |
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| 179 | 'month':BEGIN |
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| 180 | if total(fix(time) NE time) NE 0 then $ ; we switch to days with 30d/m |
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| 181 | time = julday(start[1], start[2], start[0])+round(time*30) $ |
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| 182 | ELSE for t = 0, n_elements(time)-1 DO $ |
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| 183 | time[t] = julday(start[1]+time[t], start[2], start[0]) |
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| 184 | END |
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| 185 | 'year':BEGIN |
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| 186 | if total(fix(time) NE time) NE 0 then $ ; we switch to days with 365d/y |
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| 187 | time = julday(start[1], start[2], start[0])+round(time*365) $ |
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| 188 | ELSE for t = 0, n_elements(time)-1 do $ |
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| 189 | time[t] = julday(start[1], start[2], start[0]+time[t]) |
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| 190 | END |
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| 191 | ENDCASE |
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| 192 | time = double(time) |
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| 193 | ; |
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| 194 | return, time |
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| 195 | END |
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