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EPIC 2001 Workshop, September 2003, Boulder, Colorado

EPIC 2001 Workshop, September 2003, Boulder, Colorado. Major atmospheric focus in EPIC2001 cold tongue region: Latitude-height structure and dynamics in lower troposphere. Robust observed features compared to NCEP GDAS. Deepening cloud-topped mixed layer as air flows over SST front.

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EPIC 2001 Workshop, September 2003, Boulder, Colorado

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  1. EPIC 2001 Workshop, September 2003, Boulder, Colorado

  2. Major atmospheric focus in EPIC2001 cold tongue region: Latitude-height structure and dynamics in lower troposphere

  3. Robust observed features compared to NCEP GDAS Deepening cloud-topped mixed layer as air flows over SST front Detached ABL wind maximum over the cold tongue reconnects as air flows over the SST front ABL continues to moisten and accelerate to the north of the SST front NCEP GDAS ABL inversion strength, cloudiness and horizontal wind accelerations are less than observed

  4. A regional high resolution 3D numerical model can simulate many of the observed features of the EPIC 2001 cold tongue region. Small (Poster #4) See also 2D WRF simulations by Thum et al (Poster #3) observed Deepening cloud-topped mixed layer as air flows northward over the SST front simulated From Small (Poster #4)

  5. observed Detached wind maximum over the cold tongue reconnects over the SST front and accelerates toward the ITCZ Comparison of a regional high-resolution 3D numerical model simulations with EPIC 2001 observations Small (Poster #4) See also 2D simulations of Thum et al (Poster #3) simulated Strong wind shear and light winds at the ABL top From Small (Poster #4)

  6. Cronin, M. F., S.-P. Xie, and H. Hashizume. Barometric pressure variations associated with eastern Pacific tropical instability waves. J. Climate, 16, 3506-3057, 2003. (Sep 2003 issue) Tropical Instability Wave SST variations are associated with a barometric pressure gradient.

  7. Momentum entrainment Entrainment drag plays an important role in the EPIC2001 growing cloud-topped boundary layer (McGauley et al 2003 diagnostic study and deSzoeke and Bretherton 2003 LES modeling) cloudy The generation of turbulence kinetic energy near the ABL top appears to be dominated by ABL cloud processes, rather than wind shear. Bond et al (Poster #1) clear

  8. How sharp is the SST front along 95W? The RV New Horizon encountered an SST front that was extremely sharp (1.7C in 700m) just south of the equator on 5-6 October 2001. Sensible heat flux of over 30 W/m2 was observed over the warm water to north of the front using the eddy correlation method; over the cold tongue, the fluxes were near zero and downward. Paulson et al (Poster #2)

  9. Comparison of observed and simulated surface fluxes from the Ron Brown,C-130, an LES, and the CAM 2.0 From deSzoeke (Poster #5)

  10. Budget Analysis Across the Equatorial Front of the CTIC Energy and moisture budgets across the CTIC for Fall 1999, 2000, 2001 composite. Total derivatives applied to meridional component only. Radiative terms calculated from the Column Radiation Model of the NCAR CCM. The vertical velocity was estimated as w=-Dz where D is specified. Surface fluxes are from ship observations. Composites from 1999-2001 transects along 95oW from ship (blue lines) and TAO buoy (red dots) measurements across the CTIC. The budget analysis was performed from 0o-5oN, across the strong SST gradient. Composite soundings averaged from 1999-2001 from the cold and warm sides of the equatorial front. Pyatt et al (Poster #18)

  11. (cm s-1) From fluxes From dh/dt Model Assessments: Observations and derived parameters provide a basis for evaluating model parameterizations and model response associated with flow across the CITC. Heat and Moisture Budgets (oC day-1) (og kg-1 day-1) Entrainment Rates ∆ and ∆q between the warm and cold composites. A multi-layered model would be necessary to determine more exactly the effects of this moisture structure on the overall budget. Uncertainty in entrainment rates are due to uncertainties in estimates of subsidence and radiation, and the neglect of zonal advection. Pyatt et al (Poster #18)

  12. GOES channel 1 (VIS) images for EPIC 95W flights RF03 7. Sep RF06 14. Sep RF08 19. Sep RF10 23. Sep RF11 25. Sep RF14 2. Oct RF18 9. Oct RF19 10. Oct 10N EQ 10S From deSzoeke (Poster #5)

  13. Cloud Forcing in the Tropical Eastern PacificM. F. Cronin (NOAA PMEL), N. Bond (NOAA/UW), C. Fairall (NOAA ETL), R. A. Weller (WHOI) Poster #11 Yikes! Solar Cloud Forcing (CFrs) and Longwave Cloud Forcing (CFrl) show the effect of clouds on radiation at the surface: CFrs = SWR - clearsky SWR CFrl = LWR - clearsky LWR

  14. NOAA ship Ron Brown cross-equatorial cruises ITCZ region latent heat flux • Comprehensive continuous measurements of clouds, rainfall, wind speed and direction, heat fluxes, momentum flux, radiative fluxes, air and sea surface temperatures, and specific humidity sensible heat flux net IR flux 95W and 110W stratocumulus region ITCZ and stratocumulus regimes Past 4 years, including EPIC2001 period Note larger diurnal cycle with thinner stratiform clouds during daytime Example: Diurnal variation of fluxes Hare et al (Poster #16)

  15. Daily Cycle of WindsObserved by 915-MHz Profiler at San Cristóbal, Galápagos • Meridional and deep: • El Niño events (top) • Feb-May seasons • 1997 Jul-Oct season • Meridional below ~500m, zonal above ~500m: • La Niña events (bottom) • 1998 & 1999 Jul-Oct seasons • Low-level meridional daily cycle apparently not correlated with daily cycle of ITCZ convection L. M. Hartten and P.A. Datulayta, Sept. 2003

  16. Talking points about surface wind stress and climate models The complex structure of eastern Pacific surface wind stress is accompanied by large changes in ABL vertical structure and air-sea interaction over the cold tongue region A high resolution regional numerical model gives a more realistic 95W ABL simulation than NCEP GDAS, suggesting that simply increasing horizontal and vertical resolution for the ABL may improve climate model simulation of eastern Pacific wind stress patterns The observed correlation between clouds and TKE in the growing convective ABL suggests that improved cloud momentum mixing parameterizations should be high priority for climate models Courtesy of Dudley Chelton and Michael Schlax

  17. Talking points about ABL clouds, surface fluxes and climate models The EPIC 2001 data set along 95W could be a useful case for the GEWEX Cloud System Study Working Group I and other groups of modelers and observationalists working on boundary layer parameterizations for climate models The good comparison between the ISCCP and buoy cloud forcing suggests that the NCEP analysis (and perhaps others) could be significantly improved through better assimilation of satellite-based products.

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