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Climates of Simple Non-vegetated Surfaces

From Boundary Layer Climates, T.R. OKE

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Climates of Simple Non-vegetated Surfaces

  1. 1. Pabitra Gurung CHAPTER 3 CLIMATES OF SIMPLE NON-VEGETATED SURFACES
  2. 2. CONTENTS 1. Sandy desert (a) Energy and water balances (b) Climate 2. Snow and ice (a) Radiation budget (b) Energy and water balance (c) Climate 3. Water (a) Radiation budget (b) Energy and water balance (c) Climate
  3. 3. Energy balance components and wind speed at a dry lake (desert) surface on 10-11 Jun 1950, at El Mirage, California (35°N) (Tropical desert) 1. ENERGY AND WATER BALANCES, AND CLIMATE Temperature in the air, at the surface and at two depths in a sand dune of the Central Sahara desert in mid-August Sandy Desert  Water vapour content is low and cloud is generally absent  ≈ 80% of the extra-terrestrial SW (K) radiation reaches at desert surface  High albedo (Large reflection) (0.20 – 0.45) (38°C) (27°C) (64°C) (Dry soil and sand: Low diffusivities) -ve energy flux +ve energy flux Zero energy flux
  4. 4. Typical profiles of solar radiation within snow and ice illustrating the exponential attenuation with depth 2. RADIATION BUDGET Snow and ice Water Transmission of SW radiation Yes Yes Ψ + 𝛼 + ζ = 1 𝑎 – extinction coeff. (m-1) Snow > Ice Impurities Depends on the nature of the transmitting medium and the wavelength of the radiation Albedo High (snow: 0.40-0.95, ice: 0.20-0.45) Low (0.03-0.10) Depends on the solar altitude 𝐵𝑒𝑒𝑟′ 𝑠 𝐿𝑎𝑤: 𝐾 ↓ 𝑧= 𝐾 ↓0 𝑒−𝑎𝑧 ,z Relation between solar altitude and the albedo of lake water for clear and cloudy days over lake Ontario
  5. 5. Variation of the radiation budget components over snow at Mizuho Station, Antarctica (70°S), on 13 Nov 1979 2. RADIATION BUDGET Snow and ice Water Transmission of SW radiation Yes Yes Ψ + 𝛼 + ζ = 1 𝑎 – extinction coeff. (m-1) Snow > Ice Impurities Depends on the nature of the transmitting medium and the wavelength of the radiation Albedo High (snow: 0.40-0.95, ice: 0.20-0.45) Low (0.03-0.10) Depends on the solar altitude ,z Variation of the radiation budget components for Lake Ontario (43°N), on 28 Aug 1969, with cloudless skies 𝜶 = 𝟎. 𝟎𝟕 High 𝑲∗ Low 𝑳∗ 𝑺 = 𝑲 ↓ −𝑫
  6. 6. Schematic depiction of the fluxes involved in the (a, b) energy and (c) water balances of a snowpack volume 3. ENERGY AND WATER BALANCES Snow and ice Water Vertical heat flux 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝑀 + 𝑄G 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝐴 𝑄R − Heat supply by rain , ∆𝑄S - Sensible storage, ∆𝑄 𝑀 - Latent heat storage (L 𝑓∆r), ∆𝑄A - Net horizontal heat transfer,Q 𝐸 = L 𝑠 𝐸 ,z Schematic depiction of the fluxes involved in the energy balance of a water volume Cold or frozen pack Wet or melting pack
  7. 7. Diurnal variation of the Energy balance components for a melting snow cover at Bad Lake, Saskatchewan (51°N) on 10 Apr 1974 3. ENERGY AND WATER BALANCES,z Diurnal variation of the Energy balance components for the surface of a melting glacier at Peyto Glacier, Alberta (51°N) on 29 Aug 1971 Snow and ice Water Vertical heat flux 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝑀 + 𝑄G 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝐴 𝑄R − Heat supply by rain , ∆𝑄S - Sensible storage, ∆𝑄 𝑀 - Latent heat storage (L 𝑓∆r), ∆𝑄A - Net horizontal heat transfer,Q 𝐸 = L 𝑠 𝐸
  8. 8. Diurnal variation of the Energy balance components in and above a shallow water layer on a clear September day in Japan 3. ENERGY AND WATER BALANCES,z Diurnal variation of the Energy balance components in and above the tropical Atlantic Ocean (20 Jun – 02 July, 1969) Snow and ice Water Vertical heat flux 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝑀 + 𝑄G 𝑄∗ + 𝑄 𝑅 = 𝑄 𝐻 + 𝑄 𝐸 + ∆𝑄 𝑆 + ∆𝑄 𝐴 𝑄R − Heat supply by rain , ∆𝑄S - Sensible storage, ∆𝑄 𝑀 - Latent heat storage (L 𝑓∆r), ∆𝑄A - Net horizontal heat transfer,Q 𝐸 = L 𝑠 𝐸
  9. 9. Diurnal sequence of snow temperature profiles from Devon Island 4. CLIMATE,z Sequence of nocturnal temperatures in a fresh snow cover and the underlying soil at Hamilton (a) Snow and ice  Occurrence of a maximum temperature just beneath the surface  Day radiative heat transfer dominates over heat conduction in the upper 0.5 m of snow, and the upper 5 m of ice.
  10. 10. Diurnal sequence of snow temperature profiles from Devon Island 4. CLIMATE,z Vertical variation of radiative loss and gain, and the resulting profile of net all-wave radiation (𝑄 𝑧 ∗ ), in the upper layer of a snowpack (a) Snow and ice  Occurrence of a maximum temperature just beneath the surface  Day radiative heat transfer dominates over heat conduction in the upper 0.5 m of snow, and the upper 5 m of ice.
  11. 11. Diurnal sequence of ocean temperature profiles for the tropical Atlantic Ocean from measurements (20 Jun-02Jul, 1969) 4. CLIMATE,z Profile of mean wind speed ( 𝑢), potential temperature ( 𝜃), & specific humidity ( 𝑞) over the tropical Atlantic Ocean (b) Water  Deep SW penetration  Mixing by fluid motions 0.275°C thermocline Most active in diurnal heat exchange Stable EPILIMNION HYPOLIMNION  Unlimited water availability, an efficient latent heat sink and evaporative cooling, and destabilize the surface layer  Large thermal capacity
  12. 12. THANK YOU

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