Variabilidad del chorro costero frente a Chile central René Garreaud y Ricardo Muñoz Departamento de Geofísica - Universidad de Chile Agradecimientos: José Rutllant Mark Falvey David Painemal Fondecyt

Variabilidad del chorro costero frente a Chile central Introducción: Como llegamos a esto? Climatología: Campos medios Eventos: Estadística / Estructura Conclusiones

Proyecto Fondecyt : High frequency variability of the Sc deck off central Chile CIMAR-6 (Octubre 2000) frente a Chile central Radiosondas en R/V Vidal Gormaz y Robinson Crusoe, otros datos met. Simulación usando MM5 orientada a comprender cambios en la cubierta de Sc

CIMAR-6: , RH>90% at RCI Observed MM5 – HVR (60  levels) MM5 – LVR (30  levels)

En nuestro interes de entender las variaciones de la CLM en RCI, detectamos una interesante relación entre el máximo de viento cerca de la superficie y la nubosidad...

...la cual puede incluso tener importancia para pronóstico de la cobertura nubosa: Sc dificil de pronósticar Vientos costeros no tanto... MM5/DGF, corrida operacional (29 niveles) Viento meridional en superifice a 30S – 73W

...y asi cambiamos el foco de nuestra investigación desde los Sc a los viento costeros: Relación (indirecta?) con los Sc Surgencia costera Seguridad de navegación (ff > 20 m/s = 72 km/h) Turismo Energía Eólica Datos: QuikSCAT surface winds (12 h, 0.25°, ) GOES-derived cloud products MM5 simulation of CIMAR-6

Surface wind climatology (u,v,ws) SONDJF MAMJJA Coastal Jet

Sc climatology SONDJF Coastal Jet Min. Sc Max. Variance Sc

Surface wind variability (SONDJF) Diurnal amplitude Standard deviation Max. , but  /mean = 0.4 Min. PM-AM

3D structure from MM5 simulation (9-11 October): Lat-height at 73°W V U  w

3D structure from MM5 simulation (9-11 October): Lon-height at 30°S V U  w

Jet-structure in mean field, but how often a jet occurs? Cluster analysis using ws individual fields: Similarity measured by spatial correlation Ward method Two “best separated” clusters

V > 8 m/s off central Chile almost alwayd associated with a southerly jet (dark shaded) Jet events typically a week long (3-15 days) More frequent, stronger and longer in summer.

V(33S/73W) against: U,V elsewhere (vectors) WS elsewhere (contour) Cloud elsewhere (colors) Jet events associated with: Stronger anticyclone Anticyclone displaced south Reduced Sc near the coast Increased Sc off the coast 1-Point correlation map

Jet under clear skies evident in coastal data as well

Steady-state Dynamics

Steady-state dynamic seems to hold for day- to-day changes

Thus, day-to-day changes in the meridional pressure gradient (alongshore) explain more than 70% of the changes in meridional wind over the Jet region Meridional pressure gradient is in turn modulated by the passage of mid-latitude disturbances Indirect effect on zonal (cross- shore) pressure gradient Local R 2 : v sfc – d  900 /dy

Regresamos a los Sc y las bajas costeras