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The improvement of typhoon initialization in CWB WRF

The improvement of typhoon initialization in CWB WRF. Ling-Feng Hsiao Chi-Sann Liou* Der-Song Chen Kang-Ning Huang Tien-Chiang Yeh Central Weather Bureau *Naval Research Laboratory, Monterey, CA. Relocation Scheme: ( u, v, t, q, ph+phb, mu+mub on σ-surface, max. to 4 TCs):.

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The improvement of typhoon initialization in CWB WRF

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  1. The improvement of typhoon initialization in CWB WRF Ling-Feng Hsiao Chi-Sann Liou* Der-Song Chen Kang-Ning Huang Tien-Chiang Yeh Central Weather Bureau *Naval Research Laboratory, Monterey, CA

  2. Relocation Scheme:(u, v, t, q, ph+phb, mu+mub on σ-surface, max. to 4 TCs): • apply filterto get environmental flows(filter out L< 1200km) Ue • (2) Compute perturbation fieldsas the residual of the environmental flow from total fields Up = U – Ue • (3) Interpolate sigma=.85 perturbation wind to TC centered polar coordinates and compute azimuthally averaged tangential wind speedat 24 directions Up(24) • (4) Determine the TC-edgelocations, • From the starting location, search outward at 24 directions to find the first place that • a. v < 6 m/s and dv/dr < 4x10-6, or b. v < 3 m/s until 800km end • (5) compute non-TC perturbation fieldsby the 2-pass Barnes analysis Up_ntc • (6) compute TC circulationas the residual of non-TC perturbation from the total perturbation fields Utc = Up – Up_ntc

  3. Skip the relocation scheme when: • The distance between (obs – firstguess)< 1 grid • The Max. wind of < 15m/s • The center is too close to domain LB < 300km • The center is too close to land (>10m) < 200km ( for σ-surface)

  4. Currently locate the u, v, t, q, ph+phb, mu+mub There is no problem to relocate (U,V), and q H(i,j) = ph(i,j) + phb(i,j) call relocation.f to relocat H to (i+dx , j+dy) ph(i+dx , j+dy) = H_relocated(i+dx , j+dy) - phb(i+dx , j+dy)

  5. U= Ue + Untc+ Utc

  6. TC Krosa and Lekima (45km)

  7. After relocation + bogus + 3DVAR

  8. TC Krosa and Lekima (15km)

  9. 12 24 36 48 60 72 HR U 109 103 96 121 148 180 km R 89 114 107 88 120 130 km

  10. Relocation on σ-surface : how to treat the filed over topography? • Should we try to relocate TC on the P-surface? • ( σ to P --- relocation --- P to σ) • 3. How many parameters must be relocated? • ( now: u, v, t, q, ph+phb, mu+mub)

  11. Policy to the typhoon initialization • To better descript the typhoon location and its structure (intensity) in the initial stage of the typhoon • If everything going smoothly, the 6-hr fcst error of typhoon location won’t be too much • In general, the relocation is just for a backup solution. • If something happened, then applying relocation • IF relocation happened frequently, then imply something in model • Model physics? • Typhoon initialization problem, 3DVAR analysis? Bogus?

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