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Po-Hsiung Lin Department of Atmospheric Sciences National Taiwan University

The validation of FORMOSAT-3/COSMIC atmospheric retrieval profile with high-resolution in-situ sounding data. Po-Hsiung Lin Department of Atmospheric Sciences National Taiwan University. motivation. Formosat-3/COSMIC provides ~1800 daily sounding around the world after 2006

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Po-Hsiung Lin Department of Atmospheric Sciences National Taiwan University

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  1. The validation of FORMOSAT-3/COSMIC atmospheric retrieval profile with high-resolution in-situ sounding data Po-Hsiung Lin Department of Atmospheric Sciences National Taiwan University

  2. motivation • Formosat-3/COSMIC provides ~1800 daily sounding around the world after 2006 • Comparison of T & N profiles between balloon radisondes and CHAMP has been made (Wickert, 2005). (Kuo et al.,2005)

  3. Cold bias at 100 hPa

  4. N: reflectivity P: atmospheric pressure (hPa) Pw: water vapor pressure (hPa) T: air temperature (k°) COSMIC Data Analysis and Archival Center (CDAAC) wetPrf Atmospheric profile: refractivity, temperature and water vapor. These profiles are based on 1D variational analysis using ECMWF low resolution analysis data (MSL_alt, Temp, Vp, P, Lat, Lon)/ 100 m

  5. objectives • Comparison* between the temperature and humidity retrieval profile of FORMOSAT-3/COSMIC Wetprf atmospheric soundings and high-resolution in-situ sounding data** near geo-location (less than 200 km radius) near synchronized time window (less than 2 hours) NCAR/Vaisala Dropsonde (DOTSTAR-2007, -2008) NCAR MIST-sonde (driftsonde, THORPEX/PARC 2008) fast response and high reliability from Vaisala sonde family (0.5 second sampling rate)

  6. FORMOSAT-3/COSMIC http://www.cosmic.ucar.edu • COSMIC (Constellation Observation System for Meteorology, Ionosphere and Climate) • GPS radio occultation (6 LEO GPS/Met receivers vs. 24 GPS satellites) • Launched on April 14,2006 • ~daily 2500 T/RH profiles worldwide

  7. In-situ sounding data -dropsonde • DOTSTAR 2007-2008 (May-Oct., typhoon season) 09/28,2008 Typhoon Jangmi Ceiling height : 14 km

  8. In-situ sounding data -MISTsonde • THORPEX/PARC driftsonde project (08/15-09/27, 2008) Big island, Hawaii Ceiling height : 20 km ~330 driftsondes available

  9. Inter-comparison • Condition for pair selection • nearby geo-location, within 200 km radius on 5000 m height • near-synchronized time, within 2 hours • 51 pairs for inter-comparison in 2007~2008 field campaigns • Profiled data is interpolated with 100 m vertical resolution for deviation calculation

  10. 8 extreme pairs # CASE NUMBER

  11. 72 min. later 197 km 32 min. earlier 38 km

  12. 00~05 km: 1.48 05~10 km: 0.51 10~20 km: 0.89 Average: 0.96 Unit: ℃ Case # 21 00~05 km: -0.46 05~10 km: -0.26 10~20 km: -0.15 Average: -0.29 Unit: g/kg

  13. Case # 8 00~05 km: -1.79 05~10 km: -0.92 10~20 km: 1.31 Average: -0.47 Unit: ℃ 00~05 km: -3.34 05~10 km: -0.95 10~20 km: 0.03 Average: -1.42 Unit: g/kg

  14. 00~05 km: -2.49 05~10 km: -0.66 10~20 km: -0.53 Average: -1.23 Unit: ℃ Case # 49 00~05 km: -1.56 05~10 km: 0.10 10~20 km: -0.01 Average: -0.49 Unit: g/kg

  15. Case #7: 10/04 12UTC, 2007

  16. 12:00 UTC, Oct. 4, 2007 Typhoon ?? 00~05 km: -0.27 05~10 km: -0.98 10~20 km: -1.10 Average: -0.79 Unit: ℃ 00~05 km: -1.61 05~10 km: -0.72 10~20 km: -0.18 Average: -0.84 Unit: g/kg 79 min later 51 km

  17. Summaries (1) Cloudy-sky weather condition (35 cases): F3/C temperature has Lightly warm bias for whole column dry bias for whole column

  18. Summaries (2) Clear-sky weather condition (6 cases) F3/C temperature has: cold bias for whole column Lightly dry bias below 5 km, wet bias between 5~10km and no bias above 10 km

  19. Summaries (3) All weather conditions F3/C temperature has cool bias below 10 km and warm bias above 10 km and dry bias for whole column

  20. Summaries (4) F3/C temperature has warm/dry bias in cloudy-sky condition cool/ non-dry bias in clear-sky condition

  21. Summaries (5) • The horizontal distance of F3/C limb-viewing profile is 220 ± 73 km, and the lowest height for data retrieving is 1.2 ± 0.9 km. • Slant dirfting from 36 dropsondes is 8.5 ± 4.0 km (ceiling height is ~14 km) and is 4.5 ± 3.2 km (ceiling height is ~20 km) from MIST-sondehave. • The comparison in clear-sky weather is accepted, but the bias of F3/C wetprf profile in cloudy weather should be cared

  22. January 26, 2009 • Much of the work at CDAAC is currently focussed on the understanding of various small biases in the data set. Small negative stratospheric biases can be caused by residual ionospheric noise. Small positive lower tropospheric biases are caused by low SNRs that affect occultations observed in off-bore-sight directions where antenna gain is lower. We are also in the process of revising our filtering algorithms aimed at bias reduction. Our work is aimed at reducing and quantifying these errors for COSMIC and at avoiding them in future missions. COSMIC Data Analysis and Archive Center

  23. Thank you polin@ntu.edu.tw

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