Lecture 2 (technical)

Question 1

Explain how the water cycle works

Answer 1

The water cycle is an average model over a long period. It shows dynamics on short term atmospheric processes and human intervention.

At this point of the lectures, it starts with evapotranspiration (moisture rises up), this is kinda like ‘water vapour’. This vapour condensates (samengeperst). At this point, clouds emerge. Then you have precipitation (any form of ‘Neerslag’ e.g. snow, rain). However, the cycle is not complete. Time is also an important component of it (water changes seasonally), as well as people and spatial variation for example.

Question 2

What is the water balance?

Answer 2

A quantitative expression of the water cycle over a specified area/period, expressed in mm or m3. In tutorial 1, we for example, calculated the water balance for a Greek Island for a year. This included precipitation, evaporation and transpiration. In this case, there was a shortage of water on the Island. The change in storage (Delta S) showed this.

Question 3

Are the following particles nuclei or not?

Soot
Sand
Clay
Small stones
Granite

Answer 3

Soot = yes
Sand - yes
Clay - yes
Small stones - no
Granite - no

Question 4

Explain the three types of rain formation

Answer 4

Frontal/cyclonic:
WARMER AIR LIFTED OVER COOLER AIR.

Convergence of air masses with different characteristics, particularly temperature and humidity. This type of rainfall occurs along the boundaries of contrasting air masses, where warmer air is lifted over cooler air.

o Cyclonic flow: low pressure area movement of air.
o Anti-clockwise on the northern hemisphere
o Two air masses meet the ‘front’

Convectional
* Evapotranspiration
* Air rises
* Air expands: cools down
* Water condensates

Orographic
Occurs when moist air is forced to rise over elevated terrain, such as mountains. As the air ascends the windward side of the mountain, it cools and expands due to decreasing atmospheric pressure at higher altitudes. As the air cools, its ability to hold moisture decreases, leading to condensation and the formation of clouds. The condensed water droplets eventually fall as precipitation.

Moisture = vocht  condensates / perst samen.  precipitates

Cool air depleted of moisture sinks and warms  rain shadow = a patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather

Question 5

What are the effects of climate change on components of the water balance?

Answer 5

• river discharege
• Recharge of ground water, overland flow, soil water in different areas and at different times.

Question 6

In the lecture we discussed the hypothesis on hail/heavy rainfall. Explain

Answer 6

Higher temperatures lead to stronger upward movement in clouds as a result of released latent energy. This would in turn lead to stronger circular movement in clouds, which would cause more heavy rainfall hail.

Question 7

What does the crop coefficient say about a crop? If my crop coefficient is 1, is the crop dry or wet?

Answer 7

The crop coefficient (Kc) is a dimensionless factor that represents the water use or evapotranspiration (ETc) of a specific crop relative to the reference evapotranspiration (ETo) of a well-watered reference crop. WIth a coefficient of 1, the crop is wel watered, so wet.

Question 8

Which factors influence evapotranspiration?

Answer 8

• Soil moisture stress
• Soil water salinity
• Management induced stress

Question 9

Explain the process of precipitation

Answer 9

Warm parcels of air rise up. Pressure reduces so it cools down. Saturation reached (can no longer hold) –> cools down. –> falls down

Question 10

How does air cool?

Answer 10

When it meets other air or comes in contact with cold surface. Also –> with rising air:

As air rises, air pressure at the surface is lowered. Rising air expands and cools.