(7) The Showalter is defined as the temperature difference between the ambient 500-hPa temperature and the temperature a parcel of air, “Modified stability index” initially at a selected base level, would have if brought from its condensation level to the 500-hPa surface by a moist adiabatic process. Positive values denote stable conditions, while negative values denote unstable conditions. The base level is 850 hPa, 800 hPa or 750 hPa if the station elevation is less than 1000, 1000 to 1400 or 1401 to 2000 gpm above mean sea level, respectively. (8) An intensity of precipitation value of kg m–2 s–1 before scaling (–1 after scaling) and of mm h–1 before scaling (–1 after scaling) shall indicate a –0.00001 –0.01 "trace" in BUFR and in CREX, respectively. (9) Ice thickness (0 13 115) shall be preceded by Surface type (0 08 029) set to 11, 12, 13 or 14 to specify river, lake, sea or glacier, respectively. (10) Depth of fresh snow (0 13 118) set to before scaling (–1 after scaling or in CREX) shall indicate a little snow (less than 0.0005 m). Depth of fresh snow –0.001 (0 13 118) set to before scaling (–2 after scaling or in CREX) shall indicate cover not –0.002 “snow continuous”.
(7) The “Modified Showalter stability index” is defined as the temperature difference between the ambient 500-hPa temperature and the temperature a parcel of air, initially at a selected base level, would have if brought from its condensation level to the 500-hPa surface by a moist adiabatic process. Positive values denote stable conditions, while negative values denote unstable conditions. The base level is 850 hPa, 800 hPa or 750 hPa if the station elevation is less than 1000, 1000 to 1400 or 1401 to 2000 gpm above mean sea level, respectively. (8) An intensity of precipitation value of –0.00001 kg m–2 s–1 before scaling (–1 after scaling) and of –0.01 mm h–1 before scaling (–1 after scaling) shall indicate a "trace" in BUFR and in CREX, respectively. (9) Ice thickness (0 13 115) shall be preceded by Surface type (0 08 029) set to 11, 12, 13 or 14 to specify river, lake, sea or glacier, respectively. (10) Depth of fresh snow (0 13 118) set to –0.001 before scaling (–1 after scaling or in CREX) shall indicate a little snow (less than 0.0005 m). Depth of fresh snow (0 13 118) set to –0.002 before scaling (–2 after scaling or in CREX) shall indicate “snow cover not continuous”.
WMO306_vI2_BUFRCREX_TableB_en.docx