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Teruyuki KATO （ Meteorological Research Institute / JMA ）

3/11/2006: 5th International Conference on Mesoscale Meteorology and Typhoon. Cloud Top Heights of Cumulonimbi, Thermodynamically Estimated from Objective Analysis Data during the Baiu Season. Teruyuki KATO （ Meteorological Research Institute / JMA ）. Purposes of today’s presented study.

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Teruyuki KATO （ Meteorological Research Institute / JMA ）

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  1. 3/11/2006: 5th International Conference on Mesoscale Meteorology and Typhoon Cloud Top Heights of Cumulonimbi, Thermodynamically Estimated from Objective Analysis Data during the Baiu Season Teruyuki KATO （Meteorological Research Institute / JMA）

  2. Purposes of today’s presented study By using objective analysis data, • to clarify the thermodynamically atmospheric conditions around the Baiu Frontal Zone in relation to the development of cumulonimbi. • to examine the condition under which convection with cloud tops less than the melting level can form, and its cause. Such convection was often observed around the Baiu frontal Zone (e.g., Zhang et al. 2006).

  3. JULY JUNE Objective analysis data and statistical area Data used in this study Statistical area Regional Analysis data of the JMA Resolution: 20 km Vertical grids:s-p plane p plane Available: 6 hourly Period: June & July in 2001-2005

  4. Cloud top heights of cumulonimbi, thermodynamically estimated in this study Neutral Buoyancy Level (LNB) qe is conserved. Profile of qe* NOTE: Originating level - LFC < 200 hPa Moist Adiabat Level of Free Convection (LFC) Dry Adiabat Lifting Condensation Level Equivalent potential temperature qe ~ Level of Neutral Buoyancy (LNB) of an air with the maximum qe at the low level, except the surface Profile of Temperature in the environmental field Height Originating Level Temperature

  5. Upper-air sounding data Appearance frequency of LNB around the Japan Islands First half (June) Second half (July)

  6. Appearance frequency of LNB over Northwestern Pacific Upper-air sounding data

  7. ⑤ Appearance frequency of LNB over the other areasaround the Baiu frontal zone ④ ③ ②

  8. Dependency of LNB on Atmospheric Stability LNBmax Lqe*min Equivalent potential temperature Saturated equivalent potential temperature Lapse rate Large ← stability → Small 1000hPa-level temperature of Celsius 25 degrees

  9. JUNE JULY Dependency of LNB on low-level temperature LNBmax Lqe*min 相当温位 1000hPa-level Temperature

  10. Over the Sea Appearance rate of LNBtoMaxiumequivalentpotential temperatureat the low-level JUNE JULY JUNE JULY Domain: Around Japan Islands: On the land

  11. Over the Sea 5K/km 5K/km 5K/km 5K/km Appearance rate of LNBtoLapse rateBetween500m-altitudeand700hPa-level JUNE JULY JUNE JULY Domain: Around Japan Islands: On the land

  12. Conclusions In the appearance rate of LNB during the Baiu season, > Upper and middle peaks are found on the land. (~ 150hPa) (~ 700hPa) > Another peak (~ 900hPa) is also found over the sea. Cause：Stabilization of atmospheric conditions around the Japan Islands, brought from the inflow of middle-level airs warmed by convective activities over upstream areas, especially China Continent Factor to divide LNB into upper and middle peaks is （~ 150hPa）（~ 700hPa） dependent mainly on mean lapse late G below the middle level. For G > about 5K/km and large qe of lifted air, LNB appears at the upper level. For the other, LNB appears at the middle level.

  13. Formation mechanism of Upper- and Middle-level Peaks of LNB Tropopause Upper-level Peak Upper-level Peak 200 Profile ofqe* Profile ofqe* Pressure (hPa) GU ~ 6 K km-1 500 Adiabatic heating 600 Middle-level Peak 700 GL > 5 K km-1 200hPa GL < 5 K km-1 Originating Level qe (K)

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