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The impact of solar cycle on the dry sand skin temperature at Ponce de Leon Beach

The impact of solar cycle on the dry sand skin temperature at Ponce de Leon Beach . Jeremy Fimat. Motivations. Skin temperature (T s ) is important to remote sensing (satellite). T s connected to airflow in dune environment through radiative fluxes (energy budget).

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The impact of solar cycle on the dry sand skin temperature at Ponce de Leon Beach

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  1. The impact of solar cycle on the dry sand skin temperature at Ponce de Leon Beach Jeremy Fimat

  2. Motivations • Skin temperature (Ts) is important to remote sensing (satellite). • Ts connected to airflow in dune environment through radiative fluxes (energy budget). • Fluxes impact the wind flow and atmospheric stability. • Biological effects: Turtles hatchlings.

  3. “The Denuded Beach”

  4. Transect From water’s edge to dune crest (East-to-West)

  5. Methods • Skin temperature measured with an IR thermometer. • Every 3 feet.

  6. When • Data collected over two days and two different periods of the day: - 23 June 2010: 10am – 3pm  6 transects. - 30 June 2010: 6pm – 9pm  3 transects.

  7. ZONE 3 ZONE 2 ZONE 1 ZONE 0 The 4 zones of the transect / 23 June Transect Wet sand “Beach”: Dry sand Damp sand Dune

  8. Sand temperature diurnal variation Dry sand temperature ( ̊C) Time R.J. Stathers, June 1984 1pm 9pm 8am 4pm 12am

  9. Diurnal skin temperature changes (ΔT) • Surface energy budget: energy balance under ideal conditions (e.g., clear sky). • 4 energy fluxes at skin surface: • Rn: Net radiation= incoming – outgoing radiation • SH: Sensible heat (Air). • GH: Ground heat flux. • LH: Latent heat: water vapor flux. Responses

  10. Surface Energy Budget: for dry sand in early-morning (8am) Sand surface Rn SH GH

  11. Surface Energy Budget: for dry sand at mid-morning (10am) Sand surface Rn SH GH

  12. Surface Energy Budget: for dry sand at solar peak (1pm-2pm) Sand surface Rn SH GH

  13. Surface Energy Budget: for dry sand at mid-afternoon (3/4pm) Sand surface Rn SH GH

  14. Surface Energy Budget: for dry sand in early evening (6pm) Sand surface Rn SH GH

  15. Surface Energy Budget: for dry sand in late evening (9pm) Sand surface Rn SH GH

  16. Expectations for ΔT • ΔT = T an hour – T at the previous hour. • ΔT>0 = warming. • ΔT<0 = cooling. • An important ΔT in early morning (10am). • ΔT decreasing until solar peak. • ΔT = 0 in early afternoon. • ΔT increasing until sunset (9pm).

  17. Local solar radiation on 23 June 2010 1 PM 2:30 PM

  18. ZONE 3 ZONE 2 ZONE 1 ZONE 0 The 4 zones of the transect / 23 June Transect Wet sand “Beach”: Dry sand Damp sand Dune

  19. The Beach Zone: ZONE 2 / 23 June

  20. ZONE 3 ZONE 2 ZONE 1 ZONE 0 The 4 zones of the transect / 30 June Transect “Beach”: Dry sand Damp sand Wet sand Dune

  21. The Beach Zone: ZONE 2 / 30 June

  22. Observed ΔT with timeBeach Zone (ZONE 2) Decreased warming: ΔT less positive. Increased cooling: ΔT more negative.

  23. Average ΔT = +0.4 ̊F • Average ΔT = +3.3 ̊F Average ΔT = +8.3 ̊F • Average ΔT = +6 ̊F • Average ΔT = -9.5 ̊F • Average ΔT = -11.4 ̊F Elevation sun angle with time ΔT > 0 : Warming ΔT < 0 : Cooling Decreased warming Increased cooling Sunrise Sunset

  24. Conclusion/Summary: Dry sand / Beach Zone (ZONE 2) • Maximum warming rate during mid-morning. • Maximum cooling rate during the evening. • Equilibrium after solar peak. • Dry sand skin temperature is correlated to slope of solar elevation angle. • Governed by surface energy budget.

  25. Questions ? Next: Erik Mackay

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