Table 1-3.—MRS Mandatory Levels Printout (LIST) P r e s s H g h t T e m p H u m T  d d  d f R  I M R I h P a g p m C % C d e g kts 1000.0 431 /  /  /  /  / /   /   / /  /  /  /  / /   /   / /  /  /  / /   /   / /  /  /  / 925.0 606 6.1 95 5.2 273 13.0 298 395 850.0 1303 1.5 8 5 -0.7 277 15.4 268 395 700.0 2837 -8.8 9 4 -9.6 254 8.6 2 1 6 6 6 600.0 5360 -26.4 5 8 -32.2 190 9.3 160 1001 400.0 6927 - 4 0 . 1 5 0 - 4 6 . 6 159 6 . 0 1 3 4 1221 300.0 8829 - 5 1 . 4 2 3 - 6 3 . 5 258 1 0 . 1 1 0 5 1491 2 5 0 . 0 10022 - 4 6 . 3 2 - 7 6 . 8 281 2 4 . 3 8 6 1659 2 0 0 . 0 11510 -44.5 1 - 8 0 . 0 278 2 9 . 9 6 8 1875 1 5 0 . 0 13429 - 4 5 . 7 1 - 8 0 . 8 2 7 4 3 2 . 1 5 1 2160 1 0 0 . 0 16116 -47.1 1 - 8 1 . 8 270 3 1 . 3 34 2565 7 0 . 0 18467 -50.4 1 - 8 4 . 1 2 7 1 3 0 . 5 24 2924 5 0 . 0 20662 -52.7 1 - 8 5 . 7 279 2 4 . 5 18 3262 3 0 . 0 23980 / / / / / /  /  / /  /  /  /  / /   /   / /   /   /   / /   /   / /  /  /  / Significant  Temperature  and  Humidity  Levels The   following   criteria   apply   to   the   selection   of significant  levels  for  temperature  and  humidity changes.  They  are  considered  mandatory  and  must  be reported  whenever  observed.  The  MRS  is  programmed to  automatically  select  these  levels. Surface  level  and  the  highest  level  observed At  least  1  level  between  110  and  100  hPa Freezing   level(s) The   tropopause Bases   and   tops   of   all   temperature   inversions (layer  in  which  the  temperature  increases  with  height) and  bases  and  tops  of  all  isothermal  layers  (layer  in which the temperature does not change with height) that are  30-hPa  or  more  thick  and  located  below  300-hPa level  or  below  the  tropopause Bases  and  tops  of  all  temperature  inversions  in which the temperature changes by 2.5°C or more below the 300-hPa level or the tropopause Bases and tops of all  humidity inversions  (layer in  which  the  humidity  or  dew-point  temperature increases  with  height)  in  which  the  relative  humidity increases by at least 20% when located below the 300- hPa level or the tropopause Bases and tops for all layers thicker than 20 hPa in which temperature or humidity data is missing The  bases  and  tops  of  all  layers  delineated  as doubtful (must be entered manually) The  purpose  of  selecting  significant  levels  is  to ensure  that  the  vertical  profile  of  the  atmosphere  is accurately   represented. When  you  plot  significant levels  on  a  diagram  (such  as  the  Skew  T,  Log  P), connecting  each  plotted  temperature  and  dew-point temperature  with  a  straight  line  will  provide  a  good representation  of  the  actual  temperature  and  moisture changes in the atmosphere. The  manual  rawinsonde  system  operator  must select levels based on the same criteria listed above in addition  to  other  levels  outlined  in  the  FMH-3.  As previously   stated.   the   MRS   automatically   selects “mandatory”   significant   levels   and   “supplemental” significant levels to ensure that these criteria are met. But the MRS operator must review the selected levels to ensure that the system is operating correctly. 1-13