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Ken Takahashi, Ph. D.

Thermotidal and land-heating forcing of the diurnal cycle of oceanic surface winds in the eastern tropical Pacific*. Ken Takahashi, Ph. D. * Geophysical Research Letters, 39, L04805, doi:10.1029/2011GL050692, 2012. Reuni ón LMI DISCOH, 29 de marzo, 2012 IMARPE, Callao.

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Ken Takahashi, Ph. D.

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  1. Thermotidal and land-heating forcing of the diurnal cycle of oceanic surface winds in the eastern tropical Pacific* Ken Takahashi, Ph. D. * Geophysical Research Letters, 39, L04805, doi:10.1029/2011GL050692, 2012 Reunión LMI DISCOH, 29 de marzo, 2012 IMARPE, Callao

  2. Diurnal variation in Quikscat winds (6 am minus 6 pm, local time) Gille et al., 2003

  3. “Upsidence wave”: Diurnal cycle in vertical velocity(wave forced by heating of the Andes, Garreaud & Muñoz, 2004) Rahn & Garreaud, 2010

  4. 01 Local time Diurnal cycle in surface winds in the tropical Pacific 04 Local time 07 Local time Data: TAO/TRITON Based in diurnal harmonic Ueyama & Deser, 2008 10 Local time 13 Local time

  5. Linear theory of the sea breeze(Rotunno, 1983) |Latitude| > 30° : Coastal trapping < 30° : Wave propagation =30° : Singular

  6. Surface wind diurnal variation(6 am minus 6 pm, local time, m/s) MM5 v3 MM5 v3 simulation (Δx=120 km) (Gayno-Seaman, Grell, CCM2) BC: NNRP Oct. 2008 mean conditions, fixed SST Takahashi, 2012

  7. Simulated diurnal cycle in surface wind and sea level pressure (SLP) (in local time) MM5 v3 Δx=120 km (GS, Grell, CCM2) Takahashi, 2012

  8. Migratory diurnal thermal tide Model with tropospheric solar absorption Tidal component in SLP (6 UTC) Observational estimate Lieberman & Leovy, 1995

  9. Global energy budget (Wm-2) Trenberth et al., 2009

  10. Atmospheric absorption SOLAR RADIATION TERRESTRIAL RADIATION Near IR Visible Infrared (IR) Atmospheric absorption (%) High absorption Hartmann 1994

  11. Absorción atmosférica Radiación terrestre (infrarrojo) Radiación solar H2O CO2 Gases invernadero O2, O3 CH4 N2O Hartmann, 1994 El vapor de agua es el responsable principal de la absorción de radiación solar en la atmósfera

  12. Modeled diurnal amplitude of • Land surface temperature • SLP Experiments Control Diurnal land heating suppressed* *Land-slab layer heat capacity and relaxation time-scale multiplied by 100. ** Corresponding absorption coefficients set to zero in radiation code. Absorption of solar radiation (near-IR) by atmospheric water vapor suppressed ** b) + c) Takahashi, 2012

  13. Modeled diurnal variations in SLP and surface wind Extended sea breeze Control Thermal tide x Solar “speed” = 462 m/s x x ~60 m/s Takahashi, 2012

  14. Zonal mean thermal tide Colors:Temperature (°C) Contours: Pressure (hPa) Vectors: (v,w) (m/s, cm/s) MM5 v3 Δx=120 km (GS, Grell, CCM2) Takahashi, 2012

  15. Sun West Migratory atmospheric thermal tide East Radiative air heating Low pressure Equatorward surface wind High pressure Not to scale

  16. Diurnal cycle off Ica (central-southern coast of Peru) 3 am 7 pm LT 11 pm Wind (m/s) at 40 m above surface Maximum 3 pm 7 am 11 am Takahashi et al, in preparation

  17. Diurnal anomalies 3 am 7 pm LT 11 pm Wind (m/s) at 40 m above surface 3 pm 7 am 11 am Takahashi et al, in preparation

  18. Conclusions • The diurnal cycle of surface winds has a substantial large-scale contribution (not only “sea breeze”) • Atmospheric shortwave absorption by water vapor is an important forcing of this diurnal cycle (thermal tides) • Diurnal land-heating produces an important contribution to the diurnal cycle within 2000 km from the coast.

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