Meso-γ scale Water Vapor Distributionsof the Rainfall Systems
Estimated by the Tomography Method
1)Hiromu SEKO* 1)Yoshinori Shoji ,2)Hajime NAKAMURA and 1)Tetsuya IWABUCHI
1)Meteorological Research Institute/Japan Meteorological Agency,
2)Numerical Prediction Division/Japan Meteorological Agency
3)Japan Society for the Promotion of Science/Meteorological Research Institute・GPS receivers（75）・Surface observation（9~10）
・Met-3s (P, T, U) （10）・WVR（4）・Sonde（MRI, HAO）
・BLR（MRI)・Doppler radar（MRI）
・Lidar（MRI）

GPS Satellites
SondeGPSGSIWVRSurfaceobservation
20km

GPS receiversSurface observation
Tsukuba
City20km

MRIObservation period:
2000/10/14〜11/13 (30days)
2001/7/14〜9/2(51days)

Tsukuba GPS Dense Net

Tomography method１Thunderstorm eventon 1st August 2001
Tsukuba
GPSDenseNet Area

・Small thunderstorm developed at 14JST(=5UTC) and began decaying at 15JST
over Tsukuba GPS Dense net area.
→Data of GPS Dense Net contains theinformation of the evolution of thisthunderstorm.

２(b) 850hPs(a) SurfaceKanto

Synoptic scale features(c) 500hPa

・High pressure area coveredKanto region, Japan.
・Thunderstorm was notassociated withlow pressure or front system.
３

L

13:00

13:00

L
14:00

14:00

15:00

15:00

・Large PWV was distributed over the Kanto region
・Water vapor moved toward Low pressure area near Tokyo.
・Around Low pressure, large PVW and precipitation areas were generated.

４Surface T, Qv, UV

PWV GradientSurface T, Qv, UV

13:50

13:50

14:20

14:20

14:30

14:30

PWV Gradient

28°C

14:00

14:00
18g/kg
D
28°C

14:10

14:10

C

14:40

14:40

・Precipitation in the southern part decreased surface T, Qv and PWV.
・Surface flows converged (diverged) at 1350JST (14３0JST).
・Gradient parameters in the northern part pointed to the south.
５13:50

14:10

14:30

14:50

GM01
GM11GM58
GM70
GM75

GM11Time(JST)・ Variation of
ZTD depended
on the locationof the GPS
receivers↓
Small scalevariation of ZTD
caused byThunderstorm.

Time(JST)・ ZTD increased
and decreased inthe period of20-40 minutes.

ZTD(m)

ZTD(m)

GM01

Time(JST)Time(JST)

ZTD(m)GM58

GM70
ZTD(m)

ZTD(m)

GM75

Time(JST)６

Estimation of slant water vapor (Tsukuba GPS Dense Net)

Zenith total delay

mappingfunction

Surfacepressure
Dense network
Met. Obs.

Zenith hydrostatic delay

Wet delay

Gradient of stacking map
ResidualTsukuba GPS Dense Net data(Dx=1.5-3.0km)

Gradient ofhydrostatic delay
mappingfunction

Slant water
Vapor
Input data for
tomography

Surfacepressure
ScaleheightSurfacetemperature

Dense network
Dense network AMeDAS
Met. Obs.
Sonde (Tateno)

Slant total vapor was estimated from following data:
・Tsukuba GPS Dense Net , Met. Observatory, AMeDAS, Sonde

Automated Meteorological Data Acquisition System

Following effects are taken into consider.
・ Gradient of stacking map → climatologic distribution of delay.
・ Gradient of hydrostatic delay ← ∇HPsurf * scale height.

８GM01・Slant water vapor
between the adjacent
GPS receivers arecorrelated.

Azimuth angle of the path

GM06
GM58

→ SWV contains thesignal of water vapor.
Sat26
GM58

GM06

GM58

GM06

GM01

Time(JST)Sat17Time(JST)

GM01

GM06

Time(JST)Sat09

SWD*m(ϕ)

GM58

SWD*m(ϕ)

SWD*m(ϕ)

GM01

SWD*m(ϕ)

SWD*m(ϕ)

Sat18

Sat10
GM01 GM06

GM58

GM58
GM06

Time(JST)
GM01

７Time(JST)14:30

14:10

13:50

14:50

GM58
GM70

GM58

Azimuth angleZTD,SWD*m(ϕ)

Sat10Sat17Time(JST)GM70
ZTD,SWD*m(ϕ)

Elevation angle

Sat26Sat10Time(JST)ZTD

・Large PWV region ( )passed
GM58 at 1430JST.
→ SWV of satellite 10 (17) at
GM58, which pointed toSE (NW), increased(decreased) at 1430 JST.
・SWV of satellite 26 at GM70,
which pointed to north,decreased rapidly at 1430JST.

Method of tomography
Observation equation
・ Water vapor along the slant

bpsinθp∆z3ppath b is used as input dataof tomography method・ Atmosphere is divided into∆z2GPS Sat.

a33x’33sinθpa43x’43sinθpa32x’32sinθpa21x’21sinθpa31x’31sinθp ∆z1

the boxes.
GPS Receiver
Water vapor is assumed to beuniform in each box (→Box method )p・ Water vapor along the slant path b is expressed as follows;
a21x21 +a31x31 + a32x32 +a33x33+a43x43 =bp,
where xij is water vapor density and aij is path length.
・Path length increases as elevation angle θp decreased.
To remove this effects, the equation is multiplied by sinθp１０

(a) Radar

13:50

14:00

(b) T,Qv,Wind Surface(d) Qv 0-1km(c) PWV, Gradient(e) Qv 1-2km

14:10

14:20

14:30

(f) Qv 3-4km(g) Schematic illustration of
precipitation system

Large Qv

Precipitation

Small Qv
Cold・Region of large (small) water vapor existed on the northernside of precipitation region (at precipitation region).
・Large water vapor region in the upper layer existed in southern part.
１５
This distribution is consistent with gradient parameter.

13:50

14:00

14:10

14:20

14:30

14:40

13:40-50

13:50-00

14:00-10 14:10-20

14:20-30

14:30-40

Surface,Temp,Qv,Wind
PWV
Gradient

Qv 0-1km

Qv 1-2km

Qv 2-3km

Qv 3-4km

・Time variation of water vapor shows that the water vapor deviation
did not jump to faraway place.

１６Summary
・GPS slant water vapor has the signal of the meso-γ
scale (∼10km) thunderstorm.
・Water vapor variations of the thunderstorm observedby Tsukuba GPS Dense Net：
1） Water vapor decreased under the developed thunderstorm
due to the low temperature.
2） Regions of large water vapor at z>3.5km correlated tothe intense reflectivity regions of 10minutes later.
3) From 10-20 minutes before the appearance of the echo,water vapor began to increase where the echo would appear,
especially z>3.5km.
4) Most of large water vapor regions at z>3.5km correlated tothe updraft regions.
17