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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 Jeremy Fimat
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.
Transect From water’s edge to dune crest (East-to-West)
Methods • Skin temperature measured with an IR thermometer. • Every 3 feet.
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.
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
Sand temperature diurnal variation Dry sand temperature ( ̊C) Time R.J. Stathers, June 1984 1pm 9pm 8am 4pm 12am
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
Surface Energy Budget: for dry sand in early-morning (8am) Sand surface Rn SH GH
Surface Energy Budget: for dry sand at mid-morning (10am) Sand surface Rn SH GH
Surface Energy Budget: for dry sand at solar peak (1pm-2pm) Sand surface Rn SH GH
Surface Energy Budget: for dry sand at mid-afternoon (3/4pm) Sand surface Rn SH GH
Surface Energy Budget: for dry sand in early evening (6pm) Sand surface Rn SH GH
Surface Energy Budget: for dry sand in late evening (9pm) Sand surface Rn SH GH
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).
Local solar radiation on 23 June 2010 1 PM 2:30 PM
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
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
Observed ΔT with timeBeach Zone (ZONE 2) Decreased warming: ΔT less positive. Increased cooling: ΔT more negative.
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
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.
Questions ? Next: Erik Mackay