1. METR112-Climate Modeling
Basic concepts of climate Modeling
Components and parameterization in the model
sensitivity of the model

2. How can you know the future climate and climate change?
time
past
Present
future
How can you know the future
climate and climate change?
Climate Model is the most important approach!

3. climate models are used to predict the future change
Source: Fig of IPCC AR4 chapter 10 3

4. Definition Climate Model (per NASA Earth Observatory Glossary)
A quantitative way of representing the interactions of
the atmosphere,
oceans,
land surface,
and ice.
Models can range from relatively simple to quite comprehensive.
Model components

5. Climate Model:
Equations believed to represent the physical, chemical, and biological
processes governing the climate system for the scale of interest
It can answer “What If” questions
for example, what would the climate be if CO2 is doubled?
what would the climate be if Greenland ice is all melt?
what………………………..if Amazon forest is gone?
what…………………………if SF bay area
population is doubled?

6. video
How Climate Models Work.mp4

7. Climate system

8. Atmosphere: composition
Even though with small percentage, trace gases such as CO2 and water vapor act as very important gas composition in the atmosphere

9. Atmosphere: vertical structure
Troposphere: where most weather processes take place
Note: the height of tropopause is not the same everywhere. The tropopause is lower in high latitude than in tropics

10. Atmosphere: energy budget
(Kiehl and trenberth 1997)

11. Atmosphere: general circulation
Hadley cell
Trade wind
Westerlies
ITCZ
Subtropical high
Strom track region
Polar Hadley cell

12. Ocean: critical roles in climate system
Physical properties and role in climate:
The biggest water resource on earth
Low albedo  excellent absorber of solar radiation
One of the primary heat sources for atmosphere
High heat capacity  reduces the magnitude of seasonal cycle of atmosphere
Important polarward energy transport
Large reservoir for chemical elements for atmosphere

13. Ocean: surface currents – the gyres
Wind derived
Coriolis force and location of land affect current pattern
Clockwise in NH, anticlockwise in SH
The water of the ocean surface moves in a regular pattern called surface
ocean currents. The currents are named. In this map, warm currents are shown I
n red and cold currents are shown in blue.

14. Role of ocean surface currents
Surface ocean currents carry heat from place to place in the
Earth system. This affects regional climates.
The Sun warms water at the equator more than
it does at the high latitude polar regions.
The heat travels in surface currents to higher latitudes.
A current that brings warmth into a high latitude region
will make that region’s climate less chilly.

15. Land: where most human impact are applied
Lower boundary of 30% of earth surface lower heat capacity than ocean
Higher variability in interaction with atmosphere than ocean surface
Moisture exchange
Albedo
Topography forced momentum change
Human impact directly change the land surface
Release of CO2 and other GHGs
Release of Aerosol
Change the Land surface cover
UHI effect

16. Land: aerosols
Aerosol: the small particles in the atmosphere which varying in size, chemical composition, temporal and spatial distribution and life time
Source: volcano eruptions, wind lifting of dust, biomass burning, vegetation
New result and great uncertainty of the effect of aerosol on climate
Small aerosol reflect back the solar radiation
Large aerosol can block longwave radiation

17. Land: Land cover/Landuse changes
Land-cover changes alter
surface albedo and emissivity
water uptake by roots
leaf area index
canopy interception capacity
etc

18. Land-cover changes enhance snow-albedo feedback
Before deforestation
wind,
weight
After deforestation

19. General climate model
Atmospheric GCM is first used in 1950s to predict short-time future weather
GCM develops and performs continuously improving since then with helps from updating computational resources and better understanding of atmospheric dynamics
A list of GCM and climate modeling programs
Model grid

20. Regional climate model
The first generation of regional climate model is developed by Dickinson et.al (1989) and Giorgi et. al (1990) due to the coarse resolution of GCM not able to resolve local process
Second generation of RCM (RegCM2) is developed in NCAR (Giorgi et al. 1993) based on MM5 and improved boundary layer parameterizations
Third generation of RCM (RegCM3) (Pal et al. 2007) is developed with various improvements in dynamics and physical parameterizations

21. Differences between Regional Climate Model (RCM) and Global Climate Model (GCM)
RCM GCM
Coverage: for selected region, for the globe
Model resolution: finer resolution, coarse resolution
1 km-10km km, or larger
3. Model components are different

22. The past, present and future of climate models
During the last 25 years, different components are added to the climate model to better represent our climate system

23. Model uncertainty
Model has uncertainty because model (equations) are based on our current understanding of the climate system. But our understanding needs to improve
Verify the predictions and statistics of predictions
Compatibility with observations
Various simulations to assure the agreement with basic theoretical understanding 23

24. Video: The Day after Tomorrow
Questions:
1. By which approach (observation or modeling) climatologist Jack Hall finds that there will have super-storm?
2. What is the reason Jack Hall thinks that there would be super-storm?
3. You comments on the possibility of sudden change in climate system