data assimilation of side-looking radio occultation by observing system simulation experiment
DESCRIPTION
Data Assimilation of Side-looking Radio Occultation by Observing System Simulation Experiment. Hiromu Seko (MRI) , Toshitaka Tsuda and Naoto Yoshida (Kyoto Univ.) and Y.-H. Kuo (UCAR). Concept of the side-looking observation. Tangent point. Low Earth Orbit Satellite. T 3. - PowerPoint PPT PresentationTRANSCRIPT
Data Assimilation of Side-looking Radio Occultation by
Observing System Simulation Experiment
Hiromu Seko (MRI) , Toshitaka Tsuda and Naoto Yoshida (Kyoto Univ.)
and
Y.-H. Kuo (UCAR)
Low Earth Orbit Satellite
GPS Satellite
Tangent point
P1
T2
T3
P3P2
• Low earth orbit satellite (LEO) observes the signal of GPS satellite from the moving direction of the LEO satellite, because the short shift of the tangent point is required for the precise estimation of the tangent point profiles.
T1P2P3
Forward/backward-looking
Concept of the side-looking observation
GPS Satellite
Tangent point
P1
T2
T3
P3P2
• Low earth orbit satellite (LEO) observes the signal of GPS satellite from the moving direction of the LEO satellite, because the short shift of the tangent point is required for the precise estimation of the tangent point profiles.
• If slant path data is used in the assimilation, it is not necessary to use the data which have the small angle from the moving direction of LEO satellite.
T1P2P3
Forward/backward-looking
Concept of the side-looking observationLow Earth Orbit Satellite
GPS Satellite
• In general, impact of RO data is weak because the slant path data extends several hundred kilometers. For this reason, the total amount of assimilated data should be increased by using ‘side-looking’ data.
Forward/backward-looking
Side-looking
Concept of the side-looking observationLow Earth Orbit Satellite
GPS Satellite
• In general, impact of RO data is weak because the slant path data extends several hundred kilometers. For this reason, the total amount of assimilated data should be increased by using ‘side-looking’ data.
• In this study, the assimilation experiment of side-looking data is performed by ‘Observing System Simulation Experiment’.
Forward/backward-looking
Side-looking
Concept of the side-looking observationLow Earth Orbit Satellite
• We have focused on the intense rainfall that occurred in the city of Kobe.
• Intense rainfall raised the water level of Toga river, and five people drowned in the riverside park.
Intense rainfall occurred in the city of Kobe
Kobe
03-06UTC 28 July 2008
Initial: Operational Meso-analysis 18UTC 27 July
Boundary: GSM output
Conventional data
Conventional data
18UTC 27 July
21UTC00 UTC28 July
Analysis => initial condition
Boundary: GSM output
Flow chart of Assimilation of conventional data
JMA-NHM(x=10km)
Meso-4DVar systemGSM
MSM
NoRO (Conventional data)
FT=3
-6ho
urFT
=0-3
hour
Conventional data is not enough to reproduce the intense rainfall.
Assimilation results using conventional dataFT
=3-6
hour
FT=0
-3ho
urObservation
Initial: Operational Meso-analysis 18UTC 26 July
Boundary: GSM output
Conventional data
Conventional data + Simulated occultation data (slant path data)
18UTC 27 July
21UTC00 UTC28 July
Analysis => initial condition
Boundary: GSM output
Flow chart of Observation System Simulation Experiment
JMA-NHM(x=10km)True dataFirst guess
Meso-4DVar systemGSM
MSM
Number of OC All received data(28 July 2008)
Number of OC occ-type=44(28 July 2008)
Angle (degree)
Angle (degree)
We checked the occultation data.-Signal of data of which the angles from the moving direction are less than 60 degrees are received.
-However data was not received properly in half of data where the angles were larger than 50 degrees.
0
20
40
60
80
100
120
140
160
-10 0 10 20 30 40 50 60 70 80 90
14%
11%
73%
Angle (degree)
Angle (degree)
Number of OC occ-type=44(28 July 2008)
Number of OC obtained from satellite positions(28 July 2008)
Number of occultation where the angle from moving direction is larger than 60 degrees is about 11% when the same day’s data is used.
Because half of the data where the angles of 50-60 degrees are not received properly, the data that is expected to be increased byside-looking observation becomes about 18%.
SHAO
CHAN
DAEJSUWN
YSSK
tnmltwtf
bjfs
osn2
Assimilation of ground GPS ( Shoji et al. 2009)
Assimilation period: 30hour (06UTC 27- 00UTC 28)Assimilated data: Conventional data , Analyzed rainfall, PWV obtained by satellites, Wind profiler etc. + GPS (GEONET(blue triangles)
+ Korean and Chinese GPS data(red dot)
Assimilation of ground GPS ( Shoji et al. 2009)
Intense rainfall reproduced when GPS data were assimilated.
Analyzed fields were used as
true data
Observation NoGPS (only Convection data)
GPS+Convection data
FT=0-3h FT=3-6h
FT=0-3h FT=3-6h
03UTC 28 06UTC 28
There are several occultations of which the angle from moving direction were larger than 60 degrees.
Positions of Occultations during 12-15 UTC 13 September 2006
There are several occultations of which the angle from moving direction were larger than 60 degrees.
These occultation data were shifted to Japan.
Positions of Occultations during 12-15 UTC 13 September 2006
0km Sat_dir 65
10km0km10km Sat_dir 65
65deg.
Because the region where the occultations were shifted to are positive, the rainfall is expected to be higher when this data is assimilated.
10km10km
True data - NoROwater vapor at lowest layer Enlarged map
Below the height of 3km, path-averaged refractivity of true data is larger than that of first guess.
The enhancement of the rainfalls is expected, when this data is assimilated.
0.9km
10km1.3km10km
True data - NoROwater vapor at lowest layer
Vertical profiles of D-value (Simulated - First guess)
10km10km
D-value (N)
Hei
ght (
km)
FT=3
-6ho
ur
FT=0
-3ho
urFT
=3-6
hour
FT=0
-3ho
ur
NoRO (Conventional data )
Conventional data + Occultation data
As it is expected, the rainfall became more intense when the forecast was performed from the analyzed fields, which were obtained by assimilation of conventional data and occultation data.
FT=3
-6ho
ur
FT=0
-3ho
urFT
=3-6
hour
FT=0
-3ho
ur
Observation Conventional data +
Occultation data
Intensity and area of the heavy rainfall was similar to the observed one, although the position shifted westward at FT=0-3hour.
+Occultation datalowest data:
0km
FT=3-6hour
FT=0-3hourConventional data (NoRO)
Conventional data (NoRO) 1km
+Occultation datalowest data: about 0 km
1km
2km
2km
3km
3km
In this case, the improvement of forecast is expected, if the lowest data reached the height of 2km.
+Occultation datalowest height:
0km
FT=0-3hourConventional data (NoRO)
1km
+Occultation datalowest height:
0 km
1km
2km
2km
3km
3km
Increment of lowest water vapor
The improvement of rainfall was confirmed by the increment of water vapor at the lowest layer of the model.
Summary of preliminary results
1. When the side-looking data, of which angles from the moving direction of LEO are large, are included in assimilation data, analyzed fields are further improved.
2. Assimilation of side-looking occultation data are expected as the useful method because it improves the numerical forecast.
3. However, the problems including hardware are not considered.So, more experiments are needed under the more actual condition.
Thank you for your kind attention.