Convective indexes calculated from HIRLAM output St.Petersburg The Russian State Hydrometeorological...
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Transcript of Convective indexes calculated from HIRLAM output St.Petersburg The Russian State Hydrometeorological...
Convective indexes calculated from HIRLAM output
St.PetersburgThe Russian State Hydrometeorological
UniversityFaculty of Meteorology
Meteorological Forecasting DepartmentKanukhina Anna
Aims:
• to estimate possible use of convective indexes calculated on HIRLAM outputs for forecasting of place, beginning time and type of mesoscale convective phenomena
Initial data are HIRLAM analysis and forecast files : • - air temperature at surface and heights at various
periods;• - dew point temperature at surface and heights at
various periods; • - wind parameters at surface and heights at various
periods;• - surface pressure tendencies;• - specific humidity at surface and heights at
various periods;
3 types of indexes:
• diagnostic - atmospheric preparedness for convection development (Г, С, MOCON);
• index having triggering function ( );
• indexes estimating possible type of arising phenomena (CAPE,HEI);
atmosphere statical stability index Г
Ге =
Г =
Ze
eLeU
еГ
moisture convergence
• MOCON=
r –specific humidity, kg/kg;
V – wind speed at 10 m, m/s;
rVVrrV HHHh
generalized index indicating possibility of convective disturbance formation С
Г =
eC 22
еГ
г
г
convective instability indicator (Falkovich’s index) χ
= з
зкнс
EHI energy helicity index
EHI =CAPE*H
Н – relative wind helicity;
CAPE convective available potential energy:
CAP = dzgZh
e
ee
0
Studied cases divided into 3 groups
• 1 group: days with thunderstorms and showers; indexes indicate high possibility of these weather phenomena;
• 2 group: days without any convective phenomena but indexes shows existing possibility of phenomena arising( atmospheric instability);
• 3 group: days associated with thunderstorms and showers; atmosphere is stable according to indexes consideration;
Used data
• HIRLAM forecast;
• HIRLAM analysis;
• sounding data;
• surface observations (synoptic charts OSCAR, registered thunderstorm charts from FMI site http://www.ava.fmi.fi/~tjt/salark.html).
Studied cases
29.06.200019.06.200121-23.11.200103-06.07.200216-20.07.2003
23.11.2001 12UTC
Indexes profiles for
Kardla, Estonia
MOCON, 1/s for Kardla (Estonia) on 23.11.2001 12 UTC
analyse fc=12 fc=24
MOCON and χ scattering graph for 6 h forecast (on base of analisys on 23.11.2001 06:00 UTC and forecast
23.11.2001 00:00 UTC)
С and Γ scattering graph for 6 h forecast (on base of analisys on 23.11.2001 06:00 UTC and forecast
23.11.2001 00:00 UTC)
CAPE and HEI scattering graph for 6 h forecast (on base of analisys on 23.11.2001 06:00 UTC and forecast
23.11.2001 00:00 UTC)
29.06.2000 12UTC
MOCON, CAPE analysis on 29.06.2000 12 UTC
• Thunderstorms chat on 29.06.2000
• (http://www.ava.fmi.fi/~tjt/salark.html)
СAPE and MOCON scattering graph for 24 h forecast (on base of analisys on 29.06.2000 12:00 UTC and forecast
28.06.2000 12:00 )
С and Γ scattering graph for 24 h forecast (on base of analisys on 29.06.2000 12:00 UTC and forecast
28.06.2000 12:00 )
Indexes’ correlation coefficients (forecast and analysis)
• Ряд 1 –С
• Ряд 2 – Γ
• Ряд 3 – χ
• Ряд 4 – СAPE
• Ряд 5 – MOCON
• Ряд 6 – HEI
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
1 2 3 4 5
Number of 3h increament
Co
rre
lati
on
co
eff
icie
nt
0
0,2
0,4
0,6
0,8
1
1,2
1,4
Ряд2
Ряд1
Ряд6
Ряд3
Ряд4
Ряд5
Conclusions
- χ values defined by forecasts have essential distinctions with calculations from analysis and χ can not be used for atmospheric state estimation when forecasting at period more than 6h.
- The same could be said for HEI. - CAPE and MOCON may be used forecasting at
period no more than 12h. - С and Γ forecasts are close to real situation even at
24h forecast period particularly for C values.