Lecture 3: Water in the atmosphere Flashcards
Water on earth- my notes
Water vapour is different to what makes up a cloud- cloud is liquid water droplets
Phase diagram- my notes
- solid to a gas is sublimation
- boiling point is not fixed at 100 degrees only at sea level- can change with different atmospheric pressure
Evaporation exceeds condensation- stage 1
- is a function of temperature
- rate of evaporation exceeds condensation
Dynamic equilibrium- Stage 2
- evaporation cat go anywhere- therefore water molecules tuns into condensation
Temperature increase- my notes
- more evaporation than condensation
- evaporation is so dependent on temp
- Britain in winter- less water vapor- in comparison to the tropics
what is a dew point?- my notes
where due will occur
Relative humidity in the home- my notes
- cold air- contains little water vapour
- were not adding water to the air- were heating – transforming the atmosphere in our home to extreme conditions- plants dry
Clouds - my notes
- smoke particle- is a flat surface
- increase of temp and pressure
no such thing as pure water on planet earth
Formation of fog- my notes
- Rapid cooling of the air
- -By adding water vapour from elsewhere
High clouds - my notes
Cirrus, cirrostratus and cirrocumulus- so high up – ice crystal – even in the tropics- below 0
Middle clouds - my notes
altostratus and altoculmus
-Foggier appearance
Low clouds - my notes
Most common in london
Phases of water
Water (H2O) is a dipole molecule consisting of one oxygen and two hydrogen atmos. It is an efficient absorber of infrared radiation.
• Water exists on Earth in three phases (or states):
• gasphase(watervapour) • liquidphase(liquidwater) • solidphase(ice)
- In the gas phase the molecules are moving freely, mixing with other gases. Compressible
- In the liquid phase molecules still move freely but are constantly bumping and jostling. Liquid water is virtually not compressible.
• When temperatures are lowered the molecules move slower and at temp’s below freezing point the molecules are arranged in grid-like structure, able to vibrate but not to move freely (solid phase)
Phase diagram
The Phase Diagram describes the boundaries/limits for the three phases of water as a function of ambient pressure and temperature
LATENT HEAT TRANSFER
As ice melts or water evaporates it absorbs heat and the surrounding environment cools in the process
• As water vapour condenses or liquid water freezes to ice it releases heat to the surrounding environment
• The transition between the gaseous and liquid phase involves about seven times as much heat energy as the transition between the liquid and the solid phase
• The energy that is transferred through these phase changes is called “latent heat”
HYDROLOGICAL CYCLE
Evaporation: Solar energy transforms liquid water into water vapour
• Transpiration: Moisture given up by plants (in form of water vapour)
• Condensation: Water vapour reverts back to liquid phase (formation of droplets)
• Precipitation: Liquid or solid forms of water falling from clouds (e.g. rain, snow, hail)
• Surface water returns as runoff to the oceans, or it percolates through openings in the
soil into groundwater
EVAPORATION AT ROOM TEMPERATURES
Water evaporates not only at boiling point but also at room temperatures.
• The temperature describes the average kinetic energy of a sample of molecules.
• In fact a range of kinetic energies (varying speeds of molecules) are found and they can be represented by a statistical distribution.
