1 / 19

OEAS 604: Introduction to Physical Oceanography

OEAS 604: Introduction to Physical Oceanography. Surface heat balance and flux Chapters 2,3 – Knauss Chapter 5 – Talley et al. Outline. Review heat budget components Bulk flux calculations for sensible and latent heat flux Heat content versus heat flux

jerome-chapman
Download Presentation

OEAS 604: Introduction to Physical Oceanography

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. OEAS 604: Introduction to Physical Oceanography Surface heat balance and flux Chapters 2,3 – Knauss Chapter 5 – Talley et al.

  2. Outline • Review heat budget components • Bulk flux calculations for sensible and latent heat flux • Heat content versus heat flux • Heating and cooling and the seasonal thermocline • The diurnal warm layer

  3. Heat is exchange between the ocean and the atmosphere by the following processes: • Short-wave radiation (insolation) received from the sun [Qs] • Long-wave radiation (net infrared radiation) [Qb] • Latent heat flux (evaporation) [Qe] • Sensible heat flux (air-sea temperature difference) [Qh] Flux out Advection Flux in Change in Heat content with time

  4. Short- and long-wave radiation can be measured by radiometer (pyranometer) Need to measure both incoming and outgoing radiation: Short-wave radiation: Long-wave radiation: r is reflectivity or albedo

  5. Direct measurements of latent and sensible heat flux are difficult Direct measurements require “covariance” measurements of turbulent fluctuations of vertical velocity and temperature/humidity. ρa = density of air (~1.2 kg/m3) ca = specific heat capacity of air (1030 J/Kg/K) w' = vertical velocity fluctuations (m/s) t' = temperature fluctuations (°C) Le = latent heat of vaporization (~ 2.26×106J/kg) q' = specific humidity fluctuations (ratio of mass of water vapor, m_v , per unit mass of dry air m_a) More on turbulent fluxes and Reynolds averaging in a later class

  6. Because of difficulty with direct measurements, sensible and latent heat fluxes are often estimated using the bulk formulations ρa = density of air (~1.2 kg/m3) ca = specific heat capacity of air (~1030 J/kg°K) CS = bulk transfer coefficient (Dalton number) U10 = wind speed @ 10 m Tw = temperature of water (°C) Ta = temperature of air (°C) Sensible Heat Latent Heat ρa = density of air (~1.2 kg/m3) Le = latent heat of vaporization (~ 2.26×106 J/kg) CL = bulk transfer coefficient (Stanton number) U10 = wind speed @ 10 m (m/s) qs = specific humidity at saturation qa = specific humidity of overlying air

  7. Heat Content in the Ocean The change in the amount of heat due to a change in temperature ΔT is given by: Change in temperature Specific heat Change in Heat Content mass Normalize by Volume

  8. Change in heat content: cw = 4.186 J/gC° = 4186 J/kgC° ρ = 1028 kg/m3 10°C 20°C h = 10m A 10 m thick column of water warms by 10°C in 10 days. a) What is the change in heat content? b) If no heat was transferred through the sides or the bottom, what was the surface heat flux?

  9. Change in heat Content: cw = 4.186 J/gC° = 4186 J/kgC° ρ ~ 1028 kg/m3 Dimensionally, change in heat content has units: The total heat content over the whole water column is obtained by vertically integrating: h = 10m 10°C 20°C The rate at which heat content is changing is a function of time. 10 days This has same units as heat flux

  10. Heat Budget Change in Integrated Heat Content per time Flux In = Flux Out - Qin Qout 1m 1m

  11. Heat Flux HEAT FLUX = Q is defined as the amount of heat passing through a unit area in a unit time Q 1m 1m So the amount of energy entering the ocean surface through area A (m2) in time Δt is: Joules

  12. Heat Flux This input of heat goes into a volume (V = A×h), where h is the depth of the surface mixed layer, changing its temperature by ΔT QT A hML

  13. Thermocline Depth Changes in thermocline intensity and position indicate changes in the the heat content of the ocean

  14. What is the total change in heat content? • If the profiles were taken 10 days apart, what was the net surface heat flux?

  15. What is the total change in heat content? • If the profiles were taken 10 days apart, what was the net surface heat flux? • Is there any heat flux within the water column?

  16. What is the total change in heat content? • If the profiles were taken 10 days apart, what was the net surface heat flux?

  17. Diurnal Heating and Cooling Over the course of the day, the incoming shortwave radiation is cyclic while the heat loss is roughly steady.

  18. Diurnal Warm Layer

  19. Next Class • Conservation of mass • Chapter 4 – Knauss • Chapter 5 – Talley et al.

More Related