Decoding Rawinsonde Observational Data

How to decode standard upper-air observations:

Part A -- Symbolic Form

    TTAA YYGGI IIiii                           message identification
    
    99PoPo ToToTaoDoDo dododofofo              surface data
    
    00hhh TTTaDD dddff                         1000 mb data
    
    92hhh TTTaDD dddff                          925 mb data
    
    85hhh TTTaDD dddff                          850 mb data
    
    70hhh TTTaDD dddff                          700 mb data
    
    50hhh TTTaDD dddff                          500 mb data
    
    40hhh TTTaDD dddff                          400 mb data
    
    30hhh TTTaDD dddff                          300 mb data
    
    25hhh TTTaDD dddff                          250 mb data
    
    20hhh TTTaDD dddff                          200 mb data
    
    15hhh TTTaDD dddff                          150 mb data
    
    10hhh TTTaDD dddff                          100 mb data
    
    88PtPtPt TtTtTatDtDt dtdtdtftft            tropopause data
    
    77 PmPmPm dmdmdmfmfm vbvbvava              maximum wind data
    66
    
    51515 101AdfAdf                            Regional additional data
    

Part B -- Symbolic Form

    TTBB YYGG/ IIiii                           message identification
    00PoPoPo ToToTaoDoDo                       surface data
    11PPP TTTaDD
    22PPP TTTaDD                               significant levels with
     ..........                                respect to temperature
    99PPP TTTaDD                               and/or humidity changes
    11PPP TTTaDD
     ..........
    
    PPBB YYGGa IIiii                           message identification
    9tnu1u2u3 dddff dddff dddff                
     .......                                   winds at fixed regional
    9rnu1u2u3 dddff dddff dddff                and significant levels
    

Parts A and B -- Symbol Definition

    Note: lowercase "o" indicates surface data. lowercase "t" indicates tropopause data. lowercase "m" indicates data from the level of maximum wind TTAA/TTBB Type of report which procedes. AA is only mandatory levels, while BB is significant levels with respect to temperature and/or humidity. YY Day of the month (GMT) of the observation plus 50. Example: 55 = 5th day of the month. GG Time of observation to the nearest hour (GMT). Id Indicator of the last standard isobaric surface for which the wind group is included. The number '1' is used for 100 mb and above. IIiii Block and station number. PPP Pressure in millibars. TT Observed temperature of the air in whole degrees (not rounded to nearest degree) in degrees Celsius. Ta Approximate tenths value and sign of the air temperature. If Ta is even (0,2,4,6,8), the temp TT is positive; the temp is negative if Ta is odd (1,3,5,7,9). DD Depression of the dew point temp. When the depression is 5.0 degrees C or less, the units and tenths digits of the depression are reported. When the depression is more than 5.0 degrees C, the tens and units digits of the depression are reported, plus 50, wiht 51-55 not used. Thus, DD = 10 is a depression of 1.0 degrees c and DD = 60 is a depression of 10.0 degrees c. ddd Wind direction reported to the nearest five degrees. (Examples: 320 = 320 degrees, 060 = 60 degrees). NOTE: IF THE WIND DIRECTION APPEARS TO BE GIVEN TO THE NEAREST DEGREE, (e.g., 321) THE DIRECTION WOULD BE DECODED TO THE NEAREST FIVE DEGREES (320 degrees in this case) BUT THE SPEED WOULD BE INCRESASE BY THE UNITS DIGIT MULTIPLIED BY 100 KTS. SEE "ff" IMMEDIATELY BELOW. ff Wind speed in knots, or knots plus 100. hhh Geopotential altitude of the standard isobaric suface in meters to 700 mb and in dekameters at 500 mb and above. To convert the height value to meters: 850 mb: a leading 1 is necessary 700 mb: a leading 2 or 3 is necessary 500-300 mb: a following 0 is necessary 250-100 mb: a leading 1 and a trailing 0 is necessary 88 Tropopause data. (The tropopause is defined as the lowest level where the lapse rate dereases to 2 degrees C/km or less for at least 2 km.) 77 Maximum wind data (for winds exceeding 60 kts above 500 mb). 66 When the maximum wind occurs within the sounding, 77 is used; when the max wind occurs at the termination of the sounding, 66 is used. 4 Vertical wind shear indicator. vbvb Vector difference below maximum wind. The absolute value of the vector difference between the max wind and the wind blowing at 3000 ft below the level of the max wind, to the nearest whole knot. vava Same as 'vbvb' group except for 3000' above the level of the maximum wind. 51515 Regionally developed codes follow. 101AdfAdf 101 is regional additional data indicator, while AdfAdf is the additional data two number code. 9 Indicator for wind height groups. 11-99 Indicators for significant levels with respect to temp/humidity. In general, a significant level is defined as a level at which temp and/or RH data are sufficiently important, or unusual. When the plotted report is compared with the actual sounding trace, the relative humidity is within 10 percent and the temp is within 2 degrees C of the actual sounding.

Upper wind (PPPB) codes

    a Indicator specifying type of wind measuring equipment used (0- pressure and wind instruments; 1,2- theodolite; 3- radar; 4- same as 0, but the equipment failed during the ascent.) tn Tens digit of the altitude, expressed in increments of 10,000' MSL applying to the data groups which follow. Example: "4" means winds between 40.000' and 50,000' MSL follow. u1,u2,u3 Units digit of the altitude, expressed in increments of 1,000 feet, which applies to the first, second, and third data groups following.

EXAMPLE OF A TTAA (MANDATORY LEVEL LAND STATION) RAWINDSONDE FOLLOWS:

         71853 TTAA  52121 71853 99975 09421 03003 00163 ///// /////
         85525 11056 25014 70122 01018 31018 50575 14320 31037 40741
         24520 32544 30945 393// 33048 25067 499// 33057 20209 607//
         33062 15384 665// 32547 10635 599// 33031 88180 661// 33563
         77176 33563 41008 51515 10164 00012 10194 01013 34518=
    
    EACH GROUPING DECODED, FOLLOWS: 71853 the block/station number 85525 850 mb info. TTAA mandatory levels follow 850 mb ht. (1525m) 52121 52-50=02 2nd day of month 11056 11.0(degrees c) temp. 12 12Z 56-50=6(degrees c) dp. dep. 1 last reported wind lvl=100 mb 99975 99 surface information 25014 250 degrees wnd. dir. 975 station pressure 14 kt wnd. spd. 09421 9.4(degrees c) sfc temp. 21 2.1(degrees c) dp. dep. 70122 700 mb info. 03003 030 wind direction 700 mb ht. (3122m) 003 wind speed (kts) 01018 1.0(degrees c) temp. 00163 00 1000 mb information 18 = 1.8(degrees c) dp. dep 163 1000 mb height (m) 31018 310 degrees wnd. dir. ///// missing data 18 kt. wnd. spd.

EXAMPLE OF A TTBB (SIGNIFICANT-LEVEL LAND STATION) FOLLOWS:

         71853 TTBB  5212/ 71853 00975 09421 11921 14457 22847 10850
         33782 08663 44697 00613 55636 03100 66631 04700 77468 17321
         88423 23323 99400 24520 11344 31157 22305 38359 33180 661//
         44162 669// 55147 665// 66143 625//=
    
    DECODED:
    
       71853 BLK/STN NUMBER                 11921 11 first sig. lvl.
       TTBB  SIGNIFICANT LEVELS                   921 mb
       5212/ 52-50=02 2nd day               14457 14.4(degrees c) temp.
             12    12Z                            57-50= 7(degrees c) dp. dep.
             /     last level NA            22847 22 second sig. lvl.
       71853 blk/stn number                       847 mb
       00975 00 sfc data                    10850 10.8(degrees c) temp.
             975 mb stn. pres.                    5.0(degrees c) dp. dep.
       09421 9.4(degrees c) temp.           33782 33  third sig. lvl.
             2.1(degrees c) dp. dep.              782 mb
                                            08663 8.6(degrees c) temp.
                                                  63-50=13(degrees c) dp. dep.
    

EXAMPLE OF A PPBB (SIGNIFICANT-LEVEL LAND STATION WIND DATA) FOLLOWS:

         PPBB  52120 72764 90023 12507 14511 18518 90467 20015 22507
         24509 9089/ 25512 26512 91124 29012 29513 30021 916// 30024
         92015 31030 32029 32032 93057 30535 33033 33032 94234 34549
         35039 31530 946// 30542 9503/ 32536 32024=
    
    DECODED:
    
       PPBB	winds at fixed levels
    
       52120   52-50=02   02nd day
               12         12Z
               0  measured with pressure and wind instruments
    
       72764   blk/stn number
    
       90023   9  indicator for wind height (MSL) groups
               0  tens of thousands of feet ("0" means winds between 0 and 10,000 ft. MSL.)
               0  sfc winds
               2  2000' MSL winds
               3  3000' MSL winds
    
       12507   sfc winds 125/07 kts
       14511   2000' winds 145 degrees/11 kts
       18518   3000' winds 185 degrees/18 kts
    
       90467   9  indicator for wind height groups
               0  tens of thousands of feet ("0" means winds between 0 and 10,000 ft MSL.)
               4  4,000' MSL winds
               6  6,000' MSL winds
               7  7,000' MSL winds
    
       20015   4000' winds 200 degrees/15 kts
       22507   6000' winds 225 degrees/7 kts
       24509   7000' winds 245 degrees/9 kts
    
    ....................................................
    
       9503/   9 indicator for wind height groups
               5 winds betwween 50,000' and 60,000' MSL follow
               0 50,000' MSL winds
               3 53,000' MSL winds
               / no more wind data between 50,000' and 60,000'
    
       32536   50,000' winds 325 degrees/36 kts
       32024   53,000' winds 320 degrees/24 kts

University of North Dakota / School of Aerospace Sciences / Atmospheric Science Department

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