Assimilation of GNSS Radio Occultation Data at JMA. Hiromi Owada, Yoichi Hirahara and Masami Moriya Japan Meteorological Agency

Transcription

1 Assimilation of GNSS Radio Occultation Data at JMA Hiromi Owada, Yoichi Hirahara and Masami Moriya Japan Meteorological Agency COSMIC-IROWG 2017, September

2 Outline Current RO data utilization at JMA Updates implemented into the operational system in July 2017 Changing bending angle s threshold value of the gross error check in the tropics in the global analysis Changing the handling of quality flag in the global analysis Setting the lower limit of altitude for assimilating bending angle in the global analysis ROPP6 to ROPP8 New data monitoring We have got KOMPSAT-5/AOPOD data from CDAAC web site since February 2017 FY-3C/GNOS data have been disseminated into our system via GTS since August 2017 Summary 2

3 History on the use of RO data at JMA (1/2) Satellite CHAMP C/NOFS SAC-C GRACE-A Metop-A Metop-B COSMIC TerraSAR-X GRACE-B TanDEM-X KOMPSAT-5 FY-3C Global Analysis Current status of provided data No dissemination Operational use Refractivity: ~ 17 Mar Bending angle: 18 Mar ~ Validating for the operational use Red means updates from the former IROWG-5 Period of operational use (Available for experimental use) 22 Mar ~ 20 Nov Dec ~ 06 Nov (20 Dec ~ 2 Aug. 2011) 30 Nov ~ 04 Dec Dec ~ 30 Nov ~ 28 Nov ~ 01 Nov ~ 18 Dec ~ 15 Dec ~ (01 Jul ~) (17 Feb ~) (23 Aug ~) As of September

4 History on the use of RO data at JMA (2/2) Satellite CHAMP C/NOFS SAC-C GRACE-A Metop-A Metop-B COSMIC TerraSAR-X GRACE-B TanDEM-X KOMPSAT-5 FY-3C Meso-Scale (Limited Area ) Analysis Current status of provided data No dissemination Operational use (Refractivity) Validating for the operational use Red means updates from the former IROWG-5 Period of operational use (Available for experimental use) - 24 Mar ~ Data are not in time for the cut off (23 Aug ~) As of September

5 GRACE-B data in the global analysis GRACE-B data was added in the global analysis in Dec The preliminary result of O-B statistics showed that the quality of bending angle from GRACE-B was similar to GRACE-A The typhoon position error was reduced by using GRACE-B data in the cycle experiments Blue: GRACE-A Red: GRACE-B Gray: num. of data Solid line: mean Broken line: standard deviation Normalized O-B statistics during 2 months GRACE-A: Nov.-Dec (assimilated) GRACE-B: Aug.-Sep (passive) Average of typhoon track forecast errors for August 2015 (T1512-T1518) Blue: control experiment (CNTL) Red: CNTL+GRACE-B 5

6 The FSO result of global model FSO: Forecast Sensitivity to Observations RO 1 FSO(%) By courtesy of Ishibashi (JMA/MRI) The operational global analysis in September 2014 was used for calculating FSO 6

7 UPDATES IMPLEMENTED INTO THE OPERATIONAL SYSTEM IN JULY 2017 COSMIC-IROWG 2017, September

8 Updates in July 2017 Changing bending angle s threshold value of the gross error check in the tropics in the global analysis The previous threshold was flat value in the global ( observation error *1.5) The number of tropical bending angle observations passed through the gross error check was smaller than at other areas due to the poor first guess The new threshold in the tropics is observation error *3.0 Changing the handling of quality flag (16-bit flag in Bufr) in the global analysis Setting the lower limit of altitude for assimilating bending angle in the global analysis Metop data below 8km and other data below 2km are excluded ROPP6 to ROPP8 Results of preliminary investigations were reported at the last IROWG 8

9 A profile in the Tropics (previous) Blue: first guess, Red: analysis Black: temperature and specific humidity derived from observed refractivity and first guess. First guess of the pressure, specific humidity (in case of deriving temperature) and temperature (in case of specific humidity) were used. Back: altitude of assimilated or rejected bangle specific humidity temperature 9

10 A profile in the Tropics (current) Blue: first guess, Red: analysis Black: temperature and specific humidity derived from observed refractivity and first guess. First guess of the pressure, specific humidity (in case of deriving temperature) and temperature (in case of specific humidity) were used. Back: altitude of assimilated or rejected bangle specific humidity temperature 10

11 Handling of quality flag To reject bad quality observation in the preprocess Flags to check in the global analysis Previous: Bit 5 (Bending angle processing) only Current: Bit 5 + Bit 1 (Nominal or Non-nominal quality) 11

12 Hovmoeller diagrams of normalized O-B STDV Metop-B data passed through the quality flag check EUMETSAT s upgrade 5 July, 2016 EUMETSAT s upgrade 1 November, 2016 Previous: check bit 5 only Current: check bit 5 and bit 1 12

13 Hovmoeller diagrams of normalized O-B MEAN Data passed through the current quality flag check After EUMETSAT s upgrade, Pattern of Metop s O-B mean is similar to COSMIC COSMIC Metop-B 13

14 Results of cycle experiments Normalized changes in the STDV of FG departure (O-B) Radiosonde Temp., Area: Tropics Radiosonde U wind, Area: Tropics improved improved Control run: previous operation equivalent Test run: current operation Red: 124 day samples from 10 Jun. to 11 Oct Green: 123 day samples from 10 Nov Mar The error bar represents a 95% confidence interval, and the dots represent statistically significant changes. 14

15 Recent monitoring of global O-B, O-A Metop-A Bangle 25 km Metop-B Bangle 25 km Updated on 25 July O-B STDV Updated on 25 July O-B STDV O-A STDV O-A STDV 15

16 STDV of AMSU-A/ch13 O-B AMSU-A channel 13 is the higher sounding channel, peaking around 5 hpa STDV of AMSU-A/ch13 O-B on each satellite has been clearly reduced after the update on July 25 16

17 STDV of AMSU-A/ch14 O-B AMSU-A channel 14 is the highest sounding channel, peaking around 2 hpa STDV of AMSU-A/ch14 O-B on each satellite has been clearly reduced after the update on July 25 17

18 NEW DATA MONITORING COSMIC-IROWG 2017, September

19 Number of bending angle data used in the global analysis COSMIC data were decreased rapidly on 16 April 2017 Decrease of Metop-A,B data on 25 July 2017 is caused by excluding the RO data below 8km. 19

20 Number of recent COSMIC used data and new data from KOMPSAT-5 COSMIC data were decreased rapidly on 16 April 2017 KOMPSAT-5 data have been received since 17 February 2017 from CDAAC s web site. KOMPSAT-5 may compensate the lack of COSMIC 20

21 RO data coverage in the global analysis Use: COSMIC, Metop-A,B, TerraSAR-X, GRACE-A,B No use: TanDEM-X, KOMPSAT-5, FY-3C 21

22 Satellite: KOMPSAT-5 (all nominal data, passive) COSMIC (all nominal data) Statistics of normalized refractivity O-B Period: 14 days in Apr Global Arctic (60N-90N) N.H. (20N-60N) Tropics (20S-20N) S.H. (60S-20S) Antarctic (90S-60S) Blue: COSMIC Red: KOMPSAT-5 Blue: COSMIC num. Red: KOMPSAT-5 num. Solid line: mean Broken line: standard deviation 22

23 Statistics of normalized bending angle O-B Period: 14 days in Apr Satellite: KOMPSAT-5 (all nominal data, passive) COSMIC (all nominal data) Global Arctic (60N-90N) N.H. (20N-60N) Tropics (20S-20N) S.H. (60S-20S) Antarctic (90S-60S) Blue: COSMIC Red: KOMPSAT-5 Blue: COSMIC num. Red: KOMPSAT-5 num. Solid line: mean Broken line: standard deviation 23

24 Summary (1/2) Utilization of GRACE-B data in the global analysis Implemented in December 2016 The averaged typhoon position error was reduced by using GRACE-B data in the cycle experiments Updates in July 2017 The new threshold of gross error check in the global analysis doubled the number of passed data and improved the first guess temperature and wind fields especially in the tropics Checking not only bit 5 but also bit 1 of quality flags in bufr is effective for quality control After EUMETSAT s update in November 2016, biases of bending angle from Metop-A,-B are similar to COSMIC. The lower limit of altitude for assimilating data should be reconsidered for Metop-A,-B 24

25 New data monitoring Summary (2/2) The number of COSMIC data was declined rapidly in April 2017 We expect KOMPSAT-5 and FY-3C data may compensate the lack of COSMIC 25

26 Acknowledgement We would like to thank GFZ for providing GRACE, TerraSAR-X and TanDEM-X data, EUMETSAT for Metop data, NSPO and UCAR for COSMIC data, KMA and UCAR for KOMPSAT-5 data, CMA for FY-3C data and ROM SAF for ROPP. 26

27 BACKUP SLIDES 27

28 Operational NWP systems at JMA Model Global Model (GSM) & Analysis Meso-Scale Model (MSM) & Analysis Local Forecast Model (LFM) & Analysis Horizontal/vertical resolutions TL959/100 (0.01hPa) 5km/(48+2) (22km) 2km/58 (20km) Forecast range (initial time) Data assimilation (inner loop resolution) Assimilation window Data cut off time 84h (00,06,18UTC) 264h (12UTC) 4D-VAR (TL319) 6h (-3 to +3 hours) 39h (00,03,06,09, 12,15,18,21UTC) 4D-VAR (15km) 3h (-3 to 0 hours) 50m Early Analysis : 2h20m Cycle Analysis : 11h50m(00,12UTC), 7h50m(06,18UTC) 9h (every 1 hour) 3D-VAR (5km) Rapid Update Cycle 1h (-30 to +30 minutes) 30m GNSS RO data are assimilated. As of September