reason for the failure of the simulation of heavy rainfall during x-baiu-01 - importance of a...
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Reason for the failure of the simulation Reason for the failure of the simulation of heavy rainfall during X-BAIU-01 of heavy rainfall during X-BAIU-01
- Importance of - Importance of a vertical profile of water vapor for a vertical profile of water vapor for
numerical simulations -numerical simulations -
KATO, TeruyukiKATO, Teruyuki11, Yoshiaki Sato, Yoshiaki Sato22,,1Meteorological Research Institute / Japan Meteorological Agency
2Meteorological Satellite center / Japan Meteorological Agency
andX-BAIU-01 observation groupX-BAIU-01 observation group
X-BAIU-01 (Sonde site of Nagashima)X-BAIU-01 (Sonde site of Nagashima)
Fifth International SRNWP-Workshop Fifth International SRNWP-Workshop on Non-Hydrostatic Modellingon Non-Hydrostatic Modelling
Background / MotivationBackground / Motivation
In 2001, a special field observation (X-BAIU-01) In 2001, a special field observation (X-BAIU-01) was conducted in western Japan during the rainy was conducted in western Japan during the rainy season, and a 5km-horizontal resolution season, and a 5km-horizontal resolution nonhydrostatic model was operated twice a day to nonhydrostatic model was operated twice a day to support this observation. support this observation.
5km-NHM usually predicted rainfalls successfully, 5km-NHM usually predicted rainfalls successfully, but it failed to predict the heavy rainfall observed in but it failed to predict the heavy rainfall observed in the morning of 23 June. the morning of 23 June.
In this study, by inspecting the reason of this failure In this study, by inspecting the reason of this failure it is examined what is significant for the formation of it is examined what is significant for the formation of heavy rainfall over the Baiu frontal zone.heavy rainfall over the Baiu frontal zone.
ContentContent
・・ Characteristics around the Baiu frontal zoneCharacteristics around the Baiu frontal zone (Mean field analysis produced from GANAL)(Mean field analysis produced from GANAL)
・ ・ Heavy rainfall observed on 23 June 2001Heavy rainfall observed on 23 June 2001・ ・ Numerical simulationsNumerical simulations・ ・ Comparison with observationsComparison with observations・ ・ Sensitive experimentsSensitive experiments using the modified initial field andusing the modified initial field and 4DVar method4DVar method・ ・ Trace back of an air inducing a heavy rainfallTrace back of an air inducing a heavy rainfall・ ・ ConclusionConclusion
Averaged fieldsduring intense
convective activity phase
over the Baiu frontal zone
Westerly windWesterly wind
Moist tongueMoist tongue
Pacific highPacific highS-SWS-liesS-SWS-lies
Baiu frontal Baiu frontal zonezone
S-SWS-liesS-SWS-lies
Baiu frontal Baiu frontal zonezone
Westerly windWesterly wind
Moist tongueMoist tongue
Pacific highPacific high
130E130E
45N45N
15N15N
Vertical cross sectionsduring intense
convective activity phase
over the Baiu frontal zone
15N15N 45N45N
Moist Moist tonguetongue
Subsidence of Subsidence of Pacific highPacific high
Baiu frontal Baiu frontal zonezone
15N15N 45N45N
Moist Moist tonguetongue
Baiu frontal Baiu frontal zonezone
15N15N 45N45N
Baiu frontal Baiu frontal zonezone
Characteristic features of the Baiu frontal zone in Japan
SouthSouth NorthNorth
TropopauseTropopause
Relative Relative humidity ~ 100%humidity ~ 100%
S-SWS-liesS-SWS-liesDepth ~ 1.5kmDepth ~ 1.5km
Baiu frontal Baiu frontal zonezone
SubsidenceSubsidenceof Pacific highof Pacific high
Moist tongueMoist tongue(( from China or from China or
East China East China SeaSea ))
ContinentalContinentalcold and dry cold and dry
air massair mass
Westerly windWesterly wind
Baiu front, water vapor front, is usually
analyzed here
Baiu front, water vapor front, is usually
analyzed here
Heavy rainfalls often occur at the southern edge of moist tongue.
Heavy rainfalls often occur at the southern edge of moist tongue.
Region with strongRegion with strongconvective activitiesconvective activities
Precipitation Precipitation intensityintensity
observed observed by JMA radarby JMA radar
10 JST 23 June10 JST 23 June
After 08 JSTAfter 08 JSTMCS almost stagnated.MCS almost stagnated.
At 04 JST At 04 JST a MCS suddenly formed a MCS suddenly formed over sea southwest of over sea southwest of Kyushu Is., and thenKyushu Is., and thenrapidly developed.rapidly developed.
Time cross sectionTime cross sectionin a S-N directionin a S-N direction
Surface weather map09 JST 23 June 2001
Baiu frontBaiu frontcrossed over crossed over
Kyushu Is.Kyushu Is.
TyphoonTyphoon
700h Paweather map
Moist tongueMoist tongue
SubsidenceSubsidenceof Pacific highof Pacific high
Infrared imageryInfrared imagery (( GMS-5)GMS-5)
Infrared imageryInfrared imagery (( GMS-5)GMS-5)
Cloud systems suddenly Cloud systems suddenly formed in the area without formed in the area without
clouds where the clouds where the subsidence of Pacific high subsidence of Pacific high
could dominate.could dominate.
NumericalNumerical models models
750km
RSM: JMA regional spectral modelRSM: JMA regional spectral model Precipitation schemePrecipitation scheme: Large scale condensation + Moist adjustment + Arakawa-Schubert
Resolution: Resolution: 20km20km , GridsGrids: 325 x 257 x 40
5km-NHM5km-NHM :: Nonhydrostatic modelNonhydrostatic model(MRI/NPD-NHM, Saito et al, 2001)(MRI/NPD-NHM, Saito et al, 2001) Precipitation schemePrecipitation scheme: Cold rain, predicting the mixing ratios of water vapor, cloud water, cloud ice, snow, and graupel.
Resolution: Resolution: 5km5km , GridsGrids: 150 x 150 x 38
ReproductionReproduction of the heavy rainfall of the heavy rainfall byby numerical models numerical models
ReproductionReproduction of the heavy rainfall of the heavy rainfall byby numerical models numerical models
Heavy rainfall failed toHeavy rainfall failed tobe reproduced.be reproduced.
""Observation of Baiu front over Observation of Baiu front over East China Sea and Kyushu in 2001East China Sea and Kyushu in 2001""
(( X-BAIU-01X-BAIU-01 )) Observation period:7 June – 8 July 2001
AerosondeAerosonde
Prediction Prediction between 1km-1.5kmbetween 1km-1.5km
well corresponds with well corresponds with observation.observation.
Low-level water vapor fieldsLow-level water vapor fields
after the MCS formed after the MCS formed Comparison betweenComparison between predictionprediction ofof 5km-NHM5km-NHM and and observation by observation by AEROSONDEAEROSONDE
12JST 23 June12JST 23 June
5km-NHM 5km-NHM failed to failed to
reproduce reproduce the southerly the southerly
inflow of inflow of humid air humid air
below 1 kmbelow 1 km..
Atmosphere Atmosphere below 1km below 1km
in 5km-NHM in 5km-NHM initial/boundary initial/boundary
conditionsconditionsis considerablyis considerably
drier than drier than it is in reality.it is in reality.
Before MCSs formedBefore MCSs formed
Comparison betweenComparison between TPWTPW predictedpredicted byby 5km-NHM5km-NHM
and and those derived by those derived by
TRMM TMI dataTRMM TMI data
03JST 23 June03JST 23 June
GSM IR-imageGSM IR-image
Large (Wet) Large (Wet) TPWTPW Small Small (Dry)(Dry)
Subsidence of Pacific Subsidence of Pacific high could exist in this high could exist in this
area (no cloud).area (no cloud).
5km-NHM5km-NHMTRMMTRMM
TPWTPW: Small: Small
Low-level water vaporLow-level water vapor : : SmallSmall
ModificationModification
Sensitive experimentsSensitive experiments with the modified initial field of 5km-NHM with the modified initial field of 5km-NHM
4DVar 4DVar withwith TMITMI-retrieved-retrieved TPW TPW
Modification Modification ofof low-level water vaporlow-level water vapor
15N15N 45N45N
Baiu frontal Baiu frontal zonezone
Low-level atmosphereLow-level atmosphereis humidified is humidified
to the south of to the south of Baiu frontal zone.Baiu frontal zone.
Forecast hour(t)
Forecast hour(t)
00 03 06 09 12 15 18 21 24 ● ○ ○ ○ ○ ○ ○ ○ ○ ↓ ↓ ↓ ↓ ↓ ↓ ↓
00 03 06 09 12 15 18 ○○○○○○○○○○○○○○○○○○○
●: Regional AnalysisAnalysis○: OutputOutput↓: Supply of dataSupply of data
This is improved by the following two methods.This is improved by the following two methods.
100%100%
1.5km1.5kmModificationModification
MOD:MOD: 4DV:4DV:
Forecast resultsForecast results
Valid Valid timetime ::10JST 10JST 23 June23 June
CNTLCNTL
MODMOD 44 DVDV
ObservationObservation
Improvement Improvement ofof low-level water vapor low-level water vapor fieldfield
Initial Initial time : time : 03JST 03JST 23 June23 June
CNTLCNTL
MODMOD
South
South
North
North
North
North
North
NorthSouthSouth
SouthSouth
No convection No convection forms, forms,
insofar as insofar as no strong no strong upward upward
motion existsmotion exists
Convection can form Convection can form over the region with over the region with weak updrafts, i.e.,weak updrafts, i.e.,in the south side of in the south side of
the Baiu frontal zone.the Baiu frontal zone.
Initial Initial time : time : 03JST 03JST 23 June23 June
CNTLCNTL
MODMOD
Lifting condensation level (Left)Lifting condensation level (Left)Level of free convection(Right)Level of free convection(Right)
Modification Modification ofof low-level water vapor low-level water vapor fieldfield
MODMOD
Initial time : Initial time : 03JST 03JST 23 June23 June
4DVAR4DVAR
South North
South North
Water vapor Water vapor is not is not
concentrated concentrated below 1.5km.below 1.5km.
No strong convective instability.No strong convective instability. Heavy rainfall can not Heavy rainfall can not occur.occur.
CNTLCNTL
TRACE BACKTRACE BACKof the areaof the area
withwith underestimatedunderestimated
TPWTPW
(RSM forecasts)(RSM forecasts)
TRACE BACKTRACE BACKof the areaof the area
withwith underestimatedunderestimated
TPWTPW
(RSM forecasts)(RSM forecasts)
Air with low TPW passed betweenAir with low TPW passed betweentwo upper-air sounding sites, two upper-air sounding sites,
Ishigaki and Naha.Ishigaki and Naha.
IshigakiIshigakiNahaNaha
xx
xx
10N
20N
30N
40N
140E
130E
120E
110E
×× Upper-air Upper-air sounding pointssounding points
Open spaceOpen space
Occurrence of Occurrence of heavy rainfallheavy rainfall
Special observation Special observation for the low-levelfor the low-level
and assimilation of and assimilation of satellite datasatellite data
are necessary.are necessary.
Airs pass the Airs pass the open spaceopen space
Inflow of low-level Inflow of low-level humid airhumid air
Upper–airUpper–airobservationobservation
byby sonde sonde
ConclusionConclusionTo reproduce heavy precipitation systems well,To reproduce heavy precipitation systems well,
accuracy accuracy ofof vertical water vapor analysis vertical water vapor analysis
isis very significant. very significant.
Future issues for four-dimensional assimilationFuture issues for four-dimensional assimilation
When TPW in the first guess is smaller than the observation,When TPW in the first guess is smaller than the observation,
4DVAR is not necessary to humidify the lower atmosphere.4DVAR is not necessary to humidify the lower atmosphere.
To use TPW data effectively, To use TPW data effectively,
dense observations of upper-air sounding dense observations of upper-air sounding
are necessary in the spatial and temporary.are necessary in the spatial and temporary.
Analysis of water vapor fieldAnalysis of water vapor field
The estimation of a water vapor field The estimation of a water vapor field among upper-air sounding points is difficult among upper-air sounding points is difficult
due to its being a passive tracer, due to its being a passive tracer, while dynamical fields such as temperature and while dynamical fields such as temperature and
wind can be reasonably interpolated by 4DV.wind can be reasonably interpolated by 4DV.
100%100%
1.5km1.5km
100%100%
1.5km1.5km
ModificationModificationwithoutwithoutweight functionweight function
ModificationModificationwithwithweight functionweight function
This modificationcan be used only
for such a case as the present event.
Modification of Modification of water vapor profilewater vapor profile
by assimilating TPW by assimilating TPW with 4DVwith 4DV
in areas without rain.in areas without rain.