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

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

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

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

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

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

Appearance frequency of LNB over the other areas around the Baiu frontal zone ② ③ ④ ⑤

Dependency of LNB on Atmospheric Stability L  e * min LNB max Lapse rate Large ← stability → Small Saturated equivalent potential temperature Equivalent potential temperature 1000hPa-level temperature of Celsius 25 degrees

相当温位 1000hPa-level Temperature L  e * min LNB max Dependency of LNB on low-level temperature JUNEJULY

Over the Sea On the land JUNEJULY JUNEJULY Domain  : Around Japan Islands: Appearance rate of LNB to Maxium equivalent potential temperature at the low-level

Domain  : Around Japan Islands: JUNEJULY JUNEJULY Over the Sea On the land Appearance rate of LNB to Lapse rate Between 500 m -altitude and 700 hPa-level 5K/km 5K/km 5K/km 5K/km

Appearance rate of LNB to 700 hPa-level Relative humidity Domain  : Around Japan Islands: JUNEJULY JUNEJULY Over the Sea On the land

Conclusions In the appearance rate of LNB during the Baiu season, > Upper and middle peaks are found on the land. (~ 150hPa) (~ 700hPa) (~ 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 （ ~ 150 hPa ）（ ~ 700 hPa ） （ ~ 150 hPa ）（ ~ 700 hPa ） For  > about 5K/km and large  e of lifted air, LNB appears at the upper level. For the other, LNB appears at the middle level. dependent mainly on mean lapse late  below the middle level.

Pressure (hPa)  e  (K) Profile of  e * hPa  U ~ 6 K km -1  L > 5 K km -1 Tropopause Middle-level Peak Profile of  e * Upper-level Peak Formation mechanism of Upper- and Middle-level Peaks of LNB Adiabaticheating Upper-level Peak  L < 5 K km -1 Originating Level

Lapse rate between a 500m-altitude and 500hPa-level Maximum equivalent potential temperature at the low level Temperature at a height of about 500 m

LNB の年変化 500hPa relative humidity

Diurnal variation of LNB High frequency at night over the sea High frequency at daytime on the land on the land Around Japan Islands But, the diurnal variation never appears for the height of NBL.

Over the Sea On the land Appearance rate of LNB to CAPE Domain  : Around Japan Islands: JUNEJULY JUNEJULY

Over the Sea On the land Appearance rate of LNB to 500 hPa-level Relative humidity Domain  : Around Japan Islands: JUNEJULY JUNEJULY

Cloud top heights of cumulonimbi thermodynamically estimated from objective analysis data Originating Level Height Temperature Level of Free Convection Profile of Temperature in the environmental field Moist Adiabat Dry Adiabat Lifting Condensation Level Neutral Buoyancy Level ~ Level of Neutral Buoyancy (LNB) of an air with the maximum  e at the low level Statistical area Data : Regional Analysis data of the JMA (20 km,6 hourly) the JMA (20 km,6 hourly) Period: June & July in

Detective method of LNB from equivalent potential temperature Saturated equivalent potential temperature  e ＊  e ＊ Equivalent potential temperature  e  e Potential temperature 

Typical heavy rainfall observed at the first and second part of rainy season in Japan July case: 2004 Niigata heavy rainfall 6 hourly accumulated rainfall June case: 2005 Niigata heavy rainfall

LNB estimated from objective analysis data and positions of lightning: x Occurrence condition of lightning Cloud top heights of cumulonimbi exceed 6-7 km, ~ the level of the temperature < -10 o C. July case June case

Factors to cause the difference of LNB Maximum equivalent potential temperature at the low level Lapse rate between a 500m-altitude and 500hPa-level

Difference of precipitation observed between June and July, analyzed by JMA radar June 2003 July 2003 NW SE NW SE NW SE