Latest new EUMETSAT Products: - A 15 year Reprocessed RO Data Set - GRAS Occultation Prediction

Transcription

1 Latest new EUMETSAT Products: - A 15 year Reprocessed RO Data Set - GRAS Occultation Prediction A. von Engeln, C. Marquardt, Y. Andres, R. Notarpietro, C. Garcia-Serrano, L. EUMETSAT With Inputs from M. Ringer@UKMO, S. Healy@ECMWF 1 IROWG-6, September 2017, Estes Park, Colorado, US

2 Overview EUMETSAT based reprocessing of GRAS, COSMIC, CHAMP: GRAS v1.4 reprocessing finalized (Metop-A and -B up to 2016, shown here); COSMIC/CHAMP from level 0 ongoing (available Q1 2018) Internal GRAS validation ongoing; validations of / against: Orbit, Setting/Rising, AM/PM Wobble, overlap statistics ECMWF ERA-I (GRAS later assimilated, has however no discontinuities) UCAR GRAS data (metopa2016 stream direct match) COSMIC data (cosmic2013 stream 3h, 300km match) Long term trends: using neutral bending angles directly Occultation Prediction: New EUMETSAT product for Metop-A and -B up to 14 days in advance, provided daily 2 IROWG-6, September 2017, Estes Park, Colorado, US

3 LEO POD Orbit Overlaps GRAS reprocessing v1.4 POD overlap analysis for (left) Metop-A and (right) Metop-B. Daily overlaps are based on 2h data prior to and after the processed day (each daily POD runs over 30h, centred on the processed day), legend gives the number of 2h samples uses as well as the mean RMS error in [cm]. 3 IROWG-6, September 2017, Estes Park, Colorado, US

4 Statistics of Setting/Rising (1) No data points over Antarctic plateau. Metop-A GRAS reprocessing v1.4 number of setting vs. rising difference [%] at 5km impact height. Top left: 2006 to 2016 data; top right: 2006 to May 2013 data; bottom right: June 2013 to 2016 data (after instrument parameter update, increasing the number of rising measurements). Note: total difference out of colour scale. 4 IROWG-6, September 2017, Estes Park, Colorado, US

5 Statistics of Setting/Rising (2) Setting / Rising (O-B)/B bias difference has some geographical patterns at lower altitudes. Metop-A GRAS reprocessing v1.4 (O-B)/B of setting vs. rising difference [%]. Top left: at 5km impact height ; top right: at 10km; bottom right: at 40km. Note: total difference out of colour scale for top left. 5 IROWG-6, September 2017, Estes Park, Colorado, US

6 Statistics of Setting/Rising (3) Metop-A GRAS reprocessing v1.4 (O-B)/B of setting vs. rising robust weight difference [%]. Top left: at 5km impact height ; top right: at 10km; bottom right: at 40km. Setting / Rising (O-B)/B weight difference pattern emerging. 6 IROWG-6, September 2017, Estes Park, Colorado, US

7 AM / PM Statistics - The Wobble (1) Wobble is gone, but bias structure changes around mid/end 2013 around 20km. Metop-A GRAS reprocessing v1.0.2 and v1.4 robust (O-B)/B of All, AM, PM Mid Lat bias [%]. Top left: old v1.0.2 data with wobble; top right: v1.4 at 20km impact height ; bottom right: v1.4 at 30km. 7 IROWG-6, September 2017, Estes Park, Colorado, US

8 AM / PM Statistics - The Wobble (2) Bias structure comes from NH rising occultations. Metop-A GRAS reprocessing v1.4 robust (O-B)/B of All, AM, PM Mid Lat bias [%]. Top left: at 20km impact height (setting) ; top right: at 20km (rising). Bias structure not in the SH (and not in tropics or high lats either, might be due to lack of other data there, thus ECMWF follows more closely). 8 IROWG-6, September 2017, Estes Park, Colorado, US

9 Validation against ERA-I (1) Bias removal of 2007 data (red, black) e.g. here at high latitudes likely due to ERA-I not yet assimilating GRAS GRAS reprocessing v1.4 validation of Metop-A and -B against ERA-I, (O-B)/B statistics; (top) bias, (middle) standard deviation, (bottom) weight for (left) low latitudes, (middle) mid latitudes, (right) high latitudes for various months. Legend indicates total number of occs, occs/day, failures. Improved penetration to lower altitudes with instrument update 9 IROWG-6, September 2017, Estes Park, Colorado, US

10 Validation against ERA-I (2) GRAS reprocessing v1.4 validation of Metop-A and -B against ERA-I, (O-B)/B statistics; (top) rising, (bottom) setting of (left) bias, (middle) standard deviation, (right) weight for various months. Legend indicates total number of occs, occs/day, failures. Improved penetration to lower altitudes with instrument update primarily for rising 10 IROWG-6, September 2017, Estes Park, Colorado, US

11 Validation against GRAS (UCAR) Expected bias differences at low altitudes due to different wave optics processing Direct matches of GRAS (EUMETSAT) vs. GRAS (UCAR) in 2009; (left) different latitude bands, (right) setting/rising; both plots showing bias (left) and standard deviation (right). 11 IROWG-6, September 2017, Estes Park, Colorado, US

12 Validation against COSMIC (UCAR) Unexpected high lat bias vs. COSMIC (globally averages out, see right plots) also in UCAR GRAS to COSMIC Unexpected very different bias structure against COSMIC when compared to GRAS also in UCAR GRAS to COSMIC Expected std dev differences due to UCAR switch from geometric optics to wave optics processing (v1.4 WO all altitudes) 300km, 3h matches of GRAS (EUMETSAT) vs. COSMIC (UCAR) in 2009; (left) different latitude bands, (right) setting/rising; both plots showing bias (left) and standard deviation (right). 12 IROWG-6, September 2017, Estes Park, Colorado, US

13 Validation against GRAS and COSMIC (UCAR) GRAS reprocessing v1.4 validation of Metop-A against GRAS and COSMIC UCAR processing in 2009, (O-B)/B statistics; (top) bias, (middle) standard deviation, (bottom) weight for (left) low latitudes, (middle) mid latitudes, (right) high latitudes for various months. Legend indicates total number of occs, occs/day, failures. Generally higher data quality at higher altitudes of GRAS vs. GRAS matches (expected, GRAS has USO and instrument noise the same) 13 IROWG-6, September 2017, Estes Park, Colorado, US Unexpected higher data quality at lower altitudes for GRAS vs. COSMIC matches

14 Long Term Trends of v1.4 GRAS at 20km Reprocessing v1.4 trends at 20km, data averaged over 7days; (top) bias, (middle top) standard deviations, (middle bottom) weight, (bottom) number of occultations per interval, separated for different latitude bands. Note: bias, standard deviation normalized to average value at this altitude; compared to UCAR GRAS more data available here, UCAR uses more strict QC. Trends not too be taken very seriously (simple fit) High data quality through full period 14 IROWG-6, September 2017, Estes Park, Colorado, US Very stable number of occultations from about 2007 onwards

15 Long Term Trends of v1.4 GRAS at 50km Reprocessing v1.4 trends at 50km, data averaged over 7days; (top) bias, (middle top) standard deviations, (middle bottom) weight, (bottom) number of occultations per interval, separated for different latitude bands. Note bias, standard deviation normalized to average value at this altitude. Trend simple robust line fit, take with caution. Low latitude data quality decreasing with bi-annual pattern over the period 15 IROWG-6, September 2017, Estes Park, Colorado, US

16 Long Term Trends of cosmic2013, 20km Reprocessing cosmic2013 trends at 20km, data averaged over 7days; (top) bias, (middle top) standard deviations, (middle bottom) weight, (bottom) number of occultations per interval, separated for different latitude bands. Note bias, standard deviation normalized to average value at this altitude. Trend simple robust line fit, take with caution. Data quality degradation visible over period Highly varying number of occultations over period 16 IROWG-6, September 2017, Estes Park, Colorado, US

17 Deriving Trends from 10 years of GRAS data (left): Reprocessing v1.4 bending angle trends for 10yrs of GRAS / Metop-A data, after seasonal correction (top); ERA-I bending angle trends at GRAS locations, after seasonal correction (middle); ERA-I temperature trends at GRAS locations, after seasonal correction (bottom). Note: no sampling correction applied. (bottom): detection time of trends (purple >40yrs) 17 IROWG-6, September 2017, Estes Park, Colorado, US

18 New Occultation Prediction Product for GRAS/Metop Impact of GPS Manoeuvres Impact of LEO Manoeuvre GNSS Data Outage (NANU) Metop Data Outage (left) Example of GPS occultation prediction matches against GRAS observations over the 14 day prediction period (on average about 85% or predicted also observed by GRAS); (right) generally high accuracy in reference position prediction achieved, but LEO and GPS maneuvers impact the predicted occultation location accuracy; small LEO maneuver impact (on day 9) visible for each GPS satellite towards the end of prediction period (small ripples); large impact of GPS PRN 08 and 17 visible for these GPS satellites. 18 IROWG-6, September 2017, Estes Park, Colorado, US

19 Summary / Future Steps EUMETSAT based reprocessing of GRAS, COSMIC, CHAMP: GRAS v1.4 repro for Metop-A and -B finalized, covering setting / rising statistics generally okay, some known issue at lower troposphere validation of several months vs. ERA-I shows high data quality, some AM/PM issues first validation of full GRAS data set coverage/trends vs. UCAR COSMIC and GRAS processing confirms high and consistent data quality 10 yrs bending angle trends very consistent with ERA-I trends EUMETSAT COSMIC and CHAMP reprocessing available Q Open: improve lower tropospheric processing (make set/ris consistent) GRAS Metop-A, -B Occultation Prediction (further info): new product from EUMETSAT, predicting 14 days in advance daily about 85% of occultations are prediction, position/time with high accuracy GNSS/GPS manoeuvres show larger impact on position and time of occultation prediction; LEO impact is minor (albeit data is not available during the manoeuvre), looking into mitigation options (e.g. NANU use) 19 IROWG-6, September 2017, Estes Park, Colorado, US