Jaekwan Shim, Yoon-Jeong Hwang, Yeon-Hee Kim, Kwan-Young Chung Forecast Research Division,

1. The Experiments of Sensitivity test with 2012 winter special observation data using WRF model Jaekwan Shim, Yoon-Jeong Hwang, Yeon-Hee Kim, Kwan-Young Chung Forecast Research Division, National Institute of Meteorological Research, KMA 2012 THORPEX-Asia Workshop

2. Background • Observation targets • Observe the weather elements using KMA ground-based • observation network • Observe the weather elements over the sea using Gisang1 • Observe the precipitation and cloud vertical structure • using Radio-sonde and wind-profiler, Radiometeor • The special observation has performed for two years around • middle area in south Korea West Sea Observation points of Central area Observation points of east coast line • Expectation of bservation effects− initial condition • Improve the initial field by assimilation scheme using obs data − cycle run • Reduce the forecast error (first guess) by adding observation • data continuously • − location • Verify the optimal locations of Observation that are sensitive to the • predictibility

3. Background Looks like Similar initial conditions for each observation It can make differences in 48-h forecasts! BOS BOSINC INC CNTL 00 fcst 48fcst

4. Objective • Sensitivity Analysis • − Evaluating how observation data affects a forecast • − Location for which additional observations may • reduce errors or improve the forecast • evaluate the initial increments translated downstream • investigation of observation location are sensitive to the forecast • the precipitation forecast is investigated.

5. Cases 1200UTC 31 JAN 2012 • The selected case is the developing cyclone while passing the West sea and • Korean peninsula • the cold front was formed over the south korea on 31 January 2012. • The relatively plenty of snow fall is recorded along cold front. • The stream line and moisture flux flowed in Korean peninsula between the • Siberia high and north Pacific high at least for 24 hours.

6. Experiment design(I)

7. Experiment design(II) 00 06 12 18 24 30 36 UTC 72-h forecast 72-h forecast CYCLE run 72-h forecast 3DVAR data assimilation

8. Sensitivity Experiment : Results Increments (A-B) on 0600UTC 26 JAN 2012 BOS BOSINC INC CNTL Increments (A-B) on 1200UTC 26 JAN 2012

9. Sensitivity Experiment : Results Increments (A-B) on 1200UTC 30 JAN 2012 BOS BOSINC INC CNTL Increments (A-B) on 1200UTC 31 JAN 2012

10. Sensitivity Experiment : Results 12 hr accumulated precipitation and difference (1200UTC 31 JAN 2012) BOSINC CNTL INC BOS Difference (experiments-CNTL) AWS TMPA

11. Sensitivity Experiment : Results Exps - CTN Difference of 850 hPa Mixing ratio (exp-ctl) on 0600 UTC 31 JAN 2012 at initial Difference of 850 hPa Mixing ratio (exp-ctl) on 0600 UTC 31 JAN 2012 at 12hr fcst

12. Sensitivity Experiment : Results INC BOS BOSINC Increments of 850 relative humidity 850 wind vectors F00 F12 F24

13. Sensitivity Experiment : Results INC BOS BOSINC F00 Increments of 500 height from -6 to 6 850 equivalent potential Temperature F12 F24

14. Sensitivity Experiment : Results ETS for 12 hours accumulated prec. On 31 January 2012 2.5mm/12hrETS (2012012600~2012020118) 12hrETS (2012013112)

15. Sensitivity Experiment : Results RMSE of height and Temperature Geopotential height Temperature • At low altitude, RMSE of height of all experiments show small difference. • Otherwise, CNTL and INC have the largest RMSE than BOS and BOSINC • at upper altitude. • RMSE of temperature is similar with RMSE of height except for low levels. • The observation data of Boseong reduced the RMSE in this case.

16. Summary and Conclusion • observation data is used to identify sensitivity regions of winter 2012 • over south Korea. • Sensitivity test is conducted using two points of observation data • initial increments in experiments were introduced near the • observing points. • These increments damped as they translated downstream. • Predictability of BOS and BOSINC are better than INC and CNTL(noDA). • The moisture adjustment contribute the improvement of predictability • To improve predictability of south Korea, observation of the south is • important in land. If supplementary observation is needed, it must be • conducted over the south of the Korean Peninsula.