Lecture 1 - Energy Balance Flashcards
What is the synonym for light
Electromagnectic radiation
What is a perfect blackbody?
A perfect blackbody is one that absorbs all incoming light (i.e. all wavelengths) and does not reflect any. At room temperature, such an object would appear to be perfectly black.
What does the Plankโs Radiation Law mean?
It means that with a perfect blackbodyโs temperature has a specific spectrum and intensity.
What are the five atmospheric absorption band?
- Solar radiation transmitted (70-75%)
- Infrared atmospheric window at 10 micrometer
- Most terrestrial radiation is absorbed (15-30% emitted)
- GHGs only absorb at specific wavelengths
Which are the most important greenhouse gases?
CO2 and H2O
What is forcing?
A forcing of 1 W/m2 means that at the top of the atmosphere the incoming SWR exceeds the outgoing
LWR by 1 W/m2.
What are positive forces?
- GHG
- Ozone
- Solar irradiation
- Albedo
What are negative forces?
- Aerosol effects
- Albedo
Where does a large proportion of the radiative imbalance goes to?
Oceans take of 93% and accumulates it as heat in the ocean.
What are the three most important positive feedbacks?
- Water vapor feedback: H2O is a strong greenhouse gas. Warming leads to more water vapor
in the atmosphere - Albedo feedback: melting ice reduces surface albedo, more SWR absorbed and thus
enhanced warming - Cloud feedback: Clouds affect both short wave radiation (reflectivity) and long wave
radiation (absorption/emission).
What is the most important negative feedback?
Stefan-Boltzmann law: The amount of heat removed from the earth changes with the fourth power of temperature. ๐น = ๐๐^4.
Why do clouds form differently in the tropics compared to the extra-tropics?
The tropics is characterized by deep convection, while extra-tropics is characterized by frontal systems.
What are the characteristics of High clouds?
Cold due to high altitude. Absorbed LWR is re-emitted at low temperatures and thus little LWR emitted to space, relatively transparant for sunlight: Warming effect.
What are the characteristics of Low clouds?
Very white, reflecting lots of SWR, relative warm so emit relatively much LWR: cooling effect
On average? What is the cloud effect? Cooling or warming? And how will this change with further global warming?
On average a cooling effect:
* Warming effect of high clouds expected to increase as high clouds will rise as the troposphere deepens. This results in an increase of cloud top and reface temperature.
* Cooling effect of low clouds expected to decrease. Reduction in mid- and low-level clouds. Shift of cloudy storm tracks poleward to regions with less sunlight meaning that less sunlight is reflected by clouds.
