Questions and Answers
How does the depth of a water body affect the rate of evaporation?
Why do large, deep lakes have a lower rate of evaporation compared to shallow water bodies?
What is the phenomenon that occurs in deep lakes during spring and summer, affecting the distribution of heat and evaporation?
How does the thermocline affect evaporation from deep lakes during spring and summer?
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What happens to the water in deep lakes during the autumn and winter?
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How does the turnover in deep lakes affect the rate of evaporation during autumn and winter?
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What is the primary factor that drives the mixing process during turnover in deep lakes?
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In what geographic location would you expect to observe the most significant impact of water depth on the rate of evaporation?
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How do water temperatures compare to air temperatures during summer?
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What is the main factor that contributes to evaporation in the energy budget equation?
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What effect does water surface area have on the rate of evaporation?
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What happens to evaporation rates as salinity increases?
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How is the Bowen ratio B calculated?
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What is the most common method used to estimate evaporation from a free-water body?
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What does Qs represent in the energy budget equation for evaporation?
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How does turbidity indirectly affect evaporation rates?
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What effect does an increase in stored energy of water (Qx) have on evaporation?
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Which measurement is NOT required in the method of calculating evaporation?
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At what time are observations for evaporation typically recorded using an evaporation pan?
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What is a key factor in increasing the total volume of water evaporated?
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What is represented by the variable Qv in the energy budget equation?
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What effect do atmospheric conditions have on the values of the Bowen ratio B?
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Which meteorological data is NOT typically recorded with evaporation pans?
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How does reflected solar radiation (Qr) contribute to the energy budget for evaporation?
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Study Notes
Atmospheric Pressure
- Evaporation decreases as atmospheric pressure increases due to higher air molecule density.
- Increased collisions between vapor molecules and air molecules lead to reduced evaporation rates.
Geographical Factors
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Depth of Water Body:
- Shallow water has higher evaporation due to limited heat storage.
- Deep lakes store more heat and undergo thermal stratification, affecting evaporation.
- Spring and summer cause upper layers (epilimnion) to heat uniformly, while deeper layers remain cooler.
- Cooling in winter results in density change and uniform temperature throughout the water body.
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Energy Budget for Evaporation:
- The evaporation rate (E) is derived from various energy components like incoming solar radiation, reflected radiation, and long-wave radiation.
- The energy budget equation highlights the contributions of different energy types to evaporation.
Bowen Ratio
- Calculated using the difference in temperatures between air and water, and atmospheric pressure.
- Indicates energy exchange as sensible heat (Qh) and evaporation (Qe).
- Bowen ratio values range from 0.58 to 0.66 based on atmospheric stability.
Temperature Relations
- Water temperatures are lower than air in summer and higher in winter, leading to increased evaporation in colder months.
Surface Area Effects
- Evaporation rate is inversely related to surface area.
- As air moves over a large lake, it gains moisture, reducing saturation deficit and consequently evaporation rate.
- Total evaporated volume increases with water surface size.
Water Quality Factors
- Evaporation decreases approximately 1% with each 1% increase in salinity due to reduced vapor pressure.
- Turbidity affects reflectivity and heat budget, potentially impacting evaporation indirectly.
Methods of Estimating Evaporation
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Evaporation Pans:
- A common method to estimate evaporation from free-water bodies.
- Pans are placed near reservoirs for accurate meteorological data collection.
- Regular observations measure changes in water levels adjusted for precipitation.
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Description
Learn about the factors affecting evaporation, including atmospheric pressure and geographical factors such as depth of water body. Understand how these factors impact the rate of evaporation.
