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The Global Observing System

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Presentation on theme: "The Global Observing System"— Presentation transcript:

1 The Global Observing System
Peter Bauer and colleagues European Centre for Medium-Range Weather Forecasts

2 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

3 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

4 ECMWF forecasting systems
Seasonal Forecasts Medium-Range Forecasts (Deterministic and EPS) Monthly Forecasts Atmospheric model Atmospheric model Wave model Wave model Ocean model Ocean data assimilation with 10-day window every 10 days. Forcing from ocean to atmosphere through SST+ocean currents (wave model), vice versa through P-E, wind stress, heat flux. Real Time Ocean Analysis ~8 hours Delayed Ocean Analysis ~12 days

5 Data assimilation system (4D-Var)
The observations are used to correct errors in the short forecast from the previous analysis time. Every 12 hours we assimilate 4 – 8,000,000 observations to correct the 100,000,000 variables that define the model’s virtual atmosphere. This is done by a careful 4-dimensional interpolation in space and time of the available observations; this operation takes as much computer power as the 10-day forecast.

6 Satellite observing system
Data types: Data volume:

7 Data sources: Conventional
SYNOP/SHIP/METAR: Meteorological/aeronautical land surface weather stations (2m-temperature, dew-point temperature, 10m-wind) Ships  temperature, dew-point temperature, wind (land: 2m, ships: 25m) BUOYS: Moored buoys (TAO, PIRATA) Drifters  temperature, pressure, wind TEMP/TEMPSHIP/DROPSONDES: Radiosondes ASAPs (commercial ships replacing stationary weather ships) Dropsondes released from aircrafts (NOAA, Met Office, tropical cyclones, experimental field campaigns, e.g., FASTEX, NORPEX) temperature, humidity, pressure, wind profiles PROFILERS: UHF/VHF Doppler radars (Europe, US, Japan)  wind profiles Aircraft: AIREPS (manual reports from pilots) AMDARs, ACARs, etc. (automated readings)  temperature, pressure, wind profiles

8 Example of conventional data coverage

9 Data sources: Satellites
Radiances ( brightness temperature = level 1): AMSU-A on NOAA-15/18/19, AQUA, Metop AMSU-B/MHS on NOAA-18/19, Metop SSM/I on F-15, AMSR-E on Aqua HIRS on NOAA-17/19, Metop AIRS on AQUA, IASI on Metop MVIRI on Meteosat-7, SEVIRI on Meteosat-9, GOES-11/12, MTSAT-1R imagers Bending angles ( bending angle = level 1): COSMIC (6 satellites), GRAS on Metop Ozone ( total column ozone = level 2): Total column ozone from SBUV on NOAA-17/18, OMI on Aura, SCIAMACHY on Envisat Atmospheric Motion Vectors ( wind speed = level 2): Meteosat-7/9, GOES-11/12, MTSAT-1R, MODIS on Terra/Aqua Sea surface parameters ( wind speed and wave height = level 2): Near-surface wind speed from ERS-2 scatterometer, ASCAT on Metop Significant wave height from RA-2/ASAR on Envisat, Jason altimeters

10 Example of 6-hourly satellite data coverage
LEO Sounders LEO Imagers Scatterometers GEO imagers Satellite Winds (AMVs) GPS Radio Occultation 9 April UTC

11 What types of satellites are used in NWP?
Advantages Disadvantages GEO - large regional coverage - no global coverage by single satellite - very high temporal resolution - moderate spatial resolution (VIS/IR) > short-range forecasting/nowcasting > 5-10 km for VIS/IR > feature-tracking (motion vectors) > much worse for MW > tracking of diurnal cycle (convection) LEO - global coverage with single satellite - low temporal resolution - high spatial resolution >best for NWP!

12 Observation numbers per cycle
EXP-HI EXP EXP-SV EXP-CLI EXP-RND Average radiance data count per analysis from period 08/12/ /02/2009:

13 Data Assimilation – Incremental 4D-Var
T799L91 T95L91 T159L91 T255L91 T799L91 (Trémolet 2004)

14 Transfer of information between radiances and control variables
Data Assimilation – Radiances Transfer of information between radiances and control variables Control Variable / state vector Forecast model State at time i Radiative transfer Radiance observations Wind and mass, humidity Dynamics, moist physics Wind and mass, humidity, Clear, cloud and rain including scattering Clear, cloud and rain Clear sky Clear sky clouds and rain

15 What is the observation operator?
Example 1: Radiosonde profile of T H = spatial interpolation Example 2: Clear-sky radiance observation H = spatial interpolation + clear-sky radiative transfer Example 3: Cloud/rain radiance observation H = spatial interpolation + moist physical parameterizations + multiple scattering radiative transfer MVIRI Model SSM/I Model

16 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

17 Combined impact of all satellite data
EUCOS Observing System Experiments (OSEs): 2007 ECMWF forecasting system, winter & summer season, different baseline systems: no satellite data (NOSAT), NOSAT + AMVs, NOSAT + 1 AMSU-A, general impact of satellites, impact of individual systems, all conventional observations.  500 hPa geopotential height anomaly correlation 3/4 day 3 days

18 Impact of microwave sounder data in NWP: Met Office OSEs
N-15,-16 and -17 AMSU N-16 & N-17 HIRS AMVs Scatterometer winds SSM/I ocean surface wind speed Conventional observations 2007 OSEs: N-16, N-18, MetOp-2 AMSU SSMIS AIRS & IASI (W. Bell)

19 Sensitivity of analysis increments to observations
2007 GMAO/GSI system, 1.875o, 64 levels, 6-hour window; J from analysis increments; August 2004. temperature zonal wind North-Pacific North Pacific US US satellite conventional total (Zhu & Gelaro 2008)

20 Advanced diagnostics Data assimilation: Forecast sensitivity: State at
max. 12 hours State at initial time NWP model State at time i Observation operator Observation simulations State at analysis time Sensitivity of cost to change at initial time AD of forecast model Sensitivity of cost to change in state at time i AD of observation operator Cost function J Observations State at initial time NWP model time i AD of forecast max. 48 hours Sensitivity of cost to change at initial time Analysis Cost function J Forecast sensitivity: Sensitivity of cost to observations

21 Advanced diagnostics Relative FC error reduction per system The forecast sensitivity (Cardinali, 2009, QJRMS, 135, ) denotes the sensitivity of a forecast error metric (dry energy norm at 24 or 48-hour range) to the observations. The forecast sensitivity is determined by the sensitivity of the forecast error to the initial state, the innovation vector, and the Kalman gain. Relative FC error reduction per observation (C. Cardinali)

22 Advanced diagnostics – MW sounder denial
3 AMSU-A, 2 MHS vs 1 AMSU-A, 0 MHS Forecast error reduction [%] (C. Cardinali)

23 Advanced diagnostics – MW imager denial
No MW-imagers Control Forecast error reduction [%] (C. Cardinali)

24 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

25 Data monitoring – time series
Time evolution of statistics over predefined areas/surfaces/flags (M. Dahoui)

26 Data monitoring – overview plots
Time evolution of statistics for several channels Useful for quick and routine verifications Can not be used for high spectral resolution sounders RTTOV version upgrade (M. Dahoui)

27 Data monitoring – automated warnings
Selected statistics are checked against an expected range. E.g., global mean bias correction for GOES-12 (in blue): -alert Soft limits (mean ± 5 stdev being checked, calculated from past statistics over a period of 20 days, ending 2 days earlier) Hard limits (fixed) alert: (M. Dahoui & N. Bormann)

28 Data monitoring – automated warnings
(M. Dahoui & N. Bormann)

29 Data monitoring – automated warnings
Satellite data monitoring Data monitoring – automated warnings (M. Dahoui & N. Bormann)

30 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

31 New data availabilities
2010: Oceansat-2 (Scatterometer: surface wind vector) DMSP F-18 SSMIS (MW T:, q-sounding, clouds and precipitation) SMOS (MW: soil moisture) Megha Tropiques MADRAS/SAPHIR (MW: q-sounding, clouds and precipitation) FY-3A IRAS/MWTS/MWHS/MWRI (IR/MW: T, q-sounding, clouds and precipitation) GOSAT FTS (Advanced IR: T, q, trace gas sounding) 2011: NPP (Advanced IR: T, q-sounding) ADM (Doppler-lidar: Atmospheric wind vector) 2012 and beyond: More advanced IR sounders in polar (Metop, NPOESS) and geostationary orbits (MTG, GOES) for general sounding More active instruments (wind, clouds, precipitation)

32 Cloudsat/CALIPSO data monitoring
(J.-J. Morcrette)

33 ECMWF usage of SMOS data
Global monitoring: Development of model forward operator (emissivity model) Data pre-processing (HDF2BUFR → ODB/IFS) Implementation of passive monitoring system, diagnostics, quality control Data assimilation study: Impact of SMOS constrained soil moisture on medium-range forecasts H-pol H-pol V-pol H-pol 22 January UTC; 1st background departure monitoring (no q/c)

34 FG departure in m3/m3 (January 2010)
Soil moisture from ASCAT data FG departure in m3/m3 (January 2010) FG departure bias vs ASCAT incidence angle Histograms of FG departures (P. de Rosnay)

35 Active instruments: ESA’s ADM
ESA ADM AEOLUS Doppler Lidar for wind vector observation Pressure (hPa) Control+ADM Control Control-sondes ECMWF is responsible for the development of the level 2 processor and will exploit the data as soon as available. Simulated DWL data adds value at all altitudes and well into longer-range forecasts. Zonal wind forecast error (m/s)

36 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

37 Areas of instability: Eady index
Eady-index as a proxy for baroclinic instability in the atmosphere difference between seasons is rather strong; year-to-year variability has significant seasonal dependence as well.

38 Data coverage 14/12/2008 00 UTC data density AMSU-A channel 9 EXP-HI:
EXP-SV: EXP-CLI: EXP-RND: 01-07/01/2009 Average SV RND CLI

39 Forecast impact: z500 – D08JF09
JAS08 D08JF09

40 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

41 Observations used in ERA-Interim:
ECMWF Reanalysis ERA-Interim is current ECMWF reanalysis project following ERA-15 & 40. 2006 model cycle, 4D-Var, variational bias-correction, more data (rain assimilation, GPSRO); period available, period finished, real-time in 2009. VTPR TOMS/ SBUV HIRS/ MSU/ SSU Cloud motion winds Buoy data SSM/I ERS-1 ERS-2 AMSU METEOSAT reprocessed cloud motion winds Conventional surface and upper-air observations NCAR/NCEP, ECMWF, JMA, US Navy, Twerle, GATE, FGGE, TOGA, TAO, COADS, … Aircraft data 1957 2002 1973 1979 1982 1988 1987 1991 1995 1998 1989 The ERA-40 observing system: Observations used in ERA-Interim: ERA-40 observations until August 2002 ECMWF operational data after August 2002 Reprocessed altimeter wave-height data from ERS Humidity information from SSM/I rain-affected radiance data Reprocessed METEOSAT AMV wind data Reprocessed ozone profiles from GOME Reprocessed GPSRO data from CHAMP ERA-Interim

42 Reanalysis as inter-calibration tool
Global mean bias corrections produced in ERA-Interim (MSU Channel 2): Recorded warm-target temperatures, NOAA-14: (Grody et al. 2004) Variations in warm target are due to orbital drift VarBC is able to correct the resulting calibration errors (D. Dee)

43 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

44 Combining NWP with CTM models and data assimilation systems
EC FP-6/7 projects GEMS/MACC (coordinated by ECMWF) towards GMES Atmospheric Service

45 Satellite data on CO2 and CH4 for use in MACC
Comments: Post-EPS sounder and Sentinels 4/5 should come into the picture late in period or soon after. Fire products (METEOSAT, MODIS, …) are a common requirement.

46 Satellite data on reactive gases for use in MACC
Comments: Post-EPS sounder and Sentinels 4/5 should come into the picture late in period or soon after. Fire products (METEOSAT, MODIS, …) are a common requirement.

47 Satellite data on aerosols for use in MACC
Comment: Fire products (METEOSAT, MODIS, …) are a common requirement.

48 NWP, conventional and satellite observations
General impact assessment of current observing system Data monitoring Future observations and observation usage Special Applications: Climate & Chemistry Concluding remarks

49 Concluding remarks At ECMWF, 95% of the actively assimilated data originates from satellites (90% is assimilated as radiances and only 5% as derived products and 5% from conventional products). Impact experiments demonstrate the crucial role of conventional observations! Ingredients for successful data implementation: - early data access after launch: (1) fast monitoring of data quality – feedback to space agencies, (2) early testing of data impact in NWP data assimilation systems. - near real-time data access to maximize operational use.  optimal return of investment by global user community (example: METOP). Currently most important NWP instruments at ECMWF: - advanced infrared sounders (temperature, moisture), - microwave sounders and imagers (temperature, moisture, clouds, precipitation), - GPS transmitters/receivers (temperature), - IR imagers/sounders in geostationary orbits (moisture, clouds, wind), - scatterometers (near surface wind speed, wave height), altimeters (height anomaly), - UV/VIS/IR spectrometers (trace gases, temperature).

50 Concluding remarks Future challenges with respect to observations: - active instruments – radar, lidar (wind, aerosols, clouds, precipitation, water vapour), - advanced imagers – synthetic aperture radiometers (soil moisture). Future challenges with respect to data assimilation: - model resolution upgrades also affect data assimilation resolution, - more intelligent data thinning using ensemble methods (B) and forecast error growth metrics, - assimilation of cloud/precipitation-affected data will require revised control variable, background error statistics. Future upgrades to data monitoring: - more sophisticated data co-location tools to compare performance between data from different sensors, - more advanced automated warning system.


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