kato, teruyuki 1 , yoshiaki sato 2 ,

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




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


15N15N 45N45N

Moist Moist tonguetongue


15N15N 45N45N


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


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


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


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


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.

kato, teruyuki 1 , yoshiaki sato 2 ,

Documents

observation group xbaiu

simulation of heavy

formation of heavy rainfall

cloud water

ratios of water vapor

ganalheavy rainfall

numerical modelsrsm

numerical modelsreproduction