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Smoothing of Soil Wetness Index (SWI) in ALADIN/LACE domain

Smoothing of Soil Wetness Index (SWI) in ALADIN/LACE domain. Stjepan Ivatek-Šahdan Meteorological and Hydrological Service of Croatia ivateks@cirus.dhz.hr. Problem: hot spots during the afternoon. - problem in LACE 2m Temperature forecasts during the June 2002

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Smoothing of Soil Wetness Index (SWI) in ALADIN/LACE domain

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  1. Smoothing of Soil Wetness Index (SWI) in ALADIN/LACE domain Stjepan Ivatek-Šahdan Meteorological and Hydrological Service of Croatia ivateks@cirus.dhz.hr 13th ALADIN Workshop, Prague, November 24th-28th 2003

  2. Problem: hot spots during the afternoon - problem in LACE 2m Temperature forecasts during the June 2002 - same problem in ARPEGE and ALADIN/FRANCE 2m Temperature SWI 13th ALADIN Workshop, Prague, November 24th-28th 2003

  3. How Optimum Interpolation surface analysis (operational global surface analysis) works? T2m t RH2m t Wp t 6-h 12-h 18-h 0-h Optimum Interpolation of T2m and RH2m using SYNOP observations interpolated at the model grid-point (by a 2m analysis) D T2m = T2ma - T2mfD RH2m = RH2ma - RH2mf Correction of surface parameters (Ts, Tp, Ws, Wp) using 2m increments between analysed and forecasted values Sequential analysis (every 6h) Tsa - Tsf = D T2m Tpa - Tpf = D T2m / 2p Wsa - Wsf = aWsT D T2m + aWsRHD RH2m Wpa - Wpf = aWpT D T2m + aWpRHD RH2m aWp/sT/RH = f (t, veg, LAI/Rsmin, texture, atm.cds.) -OI coefficients 13th ALADIN Workshop, Prague, November 24th-28th 2003

  4. The link between soil moisture and atmosphere The main interaction of soil moisture and atmosphere is due to evaporation and vegetation transpiration processes. E 0 <SWI< 1 Eg Etr Ws Wp Wp vegetation Ws bare ground WS - Surface soil water content WP - Total soil water content veg - Percentage of vegetation dz - Soil depth or reservoir depth 13th ALADIN Workshop, Prague, November 24th-28th 2003

  5. Soil Wetness Index (SWI) - I - represents the hydric stress of the vegetation - SWI ≤ 0 - transpiration of the plants is zero (dry soils) - SWI ≥ 1 - vegetation evaporate at the maximal rate (wet soils) Definition: Smoothing of SWI (land points, without snow cower & ice in a ground) few checks 13th ALADIN Workshop, Prague, November 24th-28th 2003

  6. Soil Wetness Index (SWI) - II Changes of SWI during the day There are no some important changes between analysis and forecasts! 13th ALADIN Workshop, Prague, November 24th-28th 2003

  7. Smoothing of Soil Wetness Index (SWI) - I - smoothing: with data from 5-ALADIN 7-ARPEGE nearest grid points; - radius: 4.1 km (1/3 of grid size) or 6.1 km (1/2 of grid size); - number of smoothing: 10, 21 and 30; - XXSMRR: smoothing is performed XX times, radius RR*0.1 km; - 30SM61- 30 smoothing with radius 6.1 km. winter 13th ALADIN Workshop, Prague, November 24th-28th 2003

  8. Smoothing of Soil Wetness Index (SWI) - II SWI for 19th June 2002 00 UTC - summer example 13th ALADIN Workshop, Prague, November 24th-28th 2003

  9. Smoothing of Soil Wetness Index (SWI) - III 13th ALADIN Workshop, Prague, November 24th-28th 2003

  10. Experiments and some results I - 12 days are chosen for testing: - 6 days in June 2002 and - 6 days in year 2003, 3 in January, 2 in April and 1 in May. - forecasts with ALADIN AL25T1_op2 in Croatia with different initial files For all Analyses no changes bigger than ±0.5 °C for T2m or ±2 % H2m. 3 days in January 2003 (07th, 13th and 16th) - 7th - lot of snow in Croatia and precipitation in South Europe, max T2m around 0°C; - 13th and 14th - max T2m around 0°C, some sunny periods; - 16th and 17th - lot of sunshine, without rain for continental Europe, max T2m > 0°C. T2m: more than 600 points changes max 5 points bigger than 0.5 °C for each forecast. H2m: more than 600 points changes max 40 points bigger than 5 % for each forecast. There is no important impact for January. 1st spring example, 2nd and 5th April 2003 - 2nd and 3rd - moving cyclone with frontal system over the Europe; - 2nd sunny in Central and East Europe; - amplitude of T2m in continental Croatia 2nd~20 °C, 3rd - west Croatia < 5 °C. - 5th and 6th West Europe no precipitation.T2m amplitude > 10 °C in South Europe. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  11. Experiments and some results II - T2m less than 5% p. changes > ±0.5 °C, just 1 % > 2 °C; - H2m max. 20 % p. changed > ±2 %, few times H2m changed > 10 %. The Change is greater than for winter but not very big. 2nd spring example, 6th May 2003 - 6th and 7th May, front moving over West Europe, and than stop on Alps, other parts of Europe T2m amplitude ~ 20 °C, lot of sunshine. Hot spots over a Central Europe, smaller for 7th. - T2m max. 22 % p. changed > ±0.5 °C, and 2 % > ±2 °C ; - H2m max. 45 % p. changed > H2m ±2 %, and 9 % > ±10 %. For this period impact of smoothing of SWI is relatively big. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  12. Experiments and some results III Results for problematic period in June 2002 - period from June 15th - 21st 2002 - very hot period T2m in Central Europe > 30 °C, with extreme values from the beginning of measuring. Very hot period for West Europe too, but not during the whole period. Generally when the number of smoothing or radius of smoothing are increased, values in more and more points change for more than ±0.5 °C or ±2 %, for forecasts. - T2m maximum 53 % p. changed > ±0.5 °C, and 9 % > ±2 °C; - H2m maximum 65 % p. changed > ±2 %, and 17 % > ±10 %. In this period, maximum changes of H2m and T2m were noticed in all examples. In summer examples, in areas with big gradients of surface temperature improvement in T2m forecast is really big, in same points for more than 2 °C, for radius of smoothing 6.1 km and for 21 or 30 times of smoothing, for 12 and 36 hrs forecast. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  13. Experiments and some results IV 13th ALADIN Workshop, Prague, November 24th-28th 2003

  14. Experiments and some results V Comparison of results against SYNOP data comparison of absolute errors for T2m If the points are dark yellow, orange or red smoothing forecast is better. If the points are green, light or dark blue operational forecast is better. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  15. Experiments and some results VI 13th ALADIN Workshop, Prague, November 24th-28th 2003

  16. Experiments and some results VII RMS and Bias for T2m For June 2002 T2m RMS is usually better for smoothed SWI, the differences are higher for 12, 36 and 18 hrs forecast, maximum for RMS=0.33 °C. BIAS is usually less than zero. Operational run is better for BIAS and difference is higher for 12, 18, 36 and 42 hrs forecasts. Maximum difference for BIAS=0.37 °C. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  17. Experiments and some results VIII Comparison of results against SYNOP data comparison of absolute errors for H2m If the points are dark yellow, orange or red smoothing forecast is better. If the points are green, light or dark blue operational forecast is better. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  18. Experiments and some results IX RMS and Bias for H2m For June 2002, with very high temperatures, RMS is better for runs with smoothed SWI, maximum improvement of RMS for H2m is 0.022. For H2m BIAS operational forecast is often better than run with smoothed SWI, maximum difference for BIAS=0.024. 13th ALADIN Workshop, Prague, November 24th-28th 2003

  19. Statistics for June 2002 against oper - “+++” - big improvement of forecast (greater than 2 °C or 5 %) ; - “++” - improvement (1-2 °C or 2-5 %) and; - “+” - small improvement in forecast (0.5-1 °C or 0.5-2 %). - Same is for “-” classes, but for worse forecasts. Number in table > 0 more points with better forecast. “1*+++1*++1*+1*-1*--1*---” same weight for all classes; “2*+++1.5*++1*+1*-2*--3*---” weight for worst forecast is little bit bigger; “2*+++1.5*++1*+1*-3*--4*---” bigger weight for worst forecast. Comparison of number of points with better and worse scores of operational run with smoothed runs, with different weights, for all days (15-20) and all forecasts (00, 06,…, 48) 13th ALADIN Workshop, Prague, November 24th-28th 2003

  20. Statistics for June 2002 against 21SM61 smoothing Number of points with better and worse scores for T2m and H2m in comparison of 20SM61 with other runs (OPER and other smoothings: 10SM61, 21SM41, 30SM41 and 30SM61), sum for all forecasts hours: 00, 06, 12… 48 UTC, and for whole period, 15th-20th of June 2002 Comparison of number of points with better and worse scores for T2m of 20SM61 with 30SM61 smoothed run, with different weights, |err(21SM61)|-|err(30SM61)|, 15th-20th of June 2002 13th ALADIN Workshop, Prague, November 24th-28th 2003

  21. Conclusion - during hot summer days, hot spots appear in T2m, caused by small scales features in the soil moisture, - problems in surface analysis and convective precipitation, - winter - small changes after smoothing; - summer - increasing number and radius of smoothing of SWI, SWI becomes smooth, maybe 30SM61 is to smooth, - with smoothed SWI - no more big gradients in T2m field, some points are colder for more than 2 °C, - January and April - no important changes in RMS and BIAS, - 15th – 20th June 2002 RMS is better for smoothed SWI, maximum improvement of RMS for H2m is 0.022, operational BIAS is better, maximum difference for BIAS=0.024. For T2m RMS is usually better for smoothed SWI, highest differences are for 12, 36 and 18 hrs forecast, maximum for RMS=0.334 °C. For all experiments BIAS is usually less than zero. Operational run better for BIAS and difference is higher for 12, 18, 36 and 42 hrs forecasts, maximum difference for BIAS=0.369 °C. -proposed solution: to use 21SM61 smoothing, smoothing applied 21 times and 6.1 km radius of smoothing (half of the horizontal grid), - test with longer parallel, - if the smoothing of SWI is used in ARPEGE it is not needed in ALADIN. 13th ALADIN Workshop, Prague, November 24th-28th 2003

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