Hierarchy of atmospheric models Considerations Purpose Speed v

Hierarchy of atmospheric models • Considerations: – Purpose – Speed v. Complexity research forecast Process Models Limited-Area Models Global Models turbulence weather systems climate states balance regional climate paleoclimate hurricane intensity hurricanes global warming seasonal forecasts short-term weather climate extremes Ooyama 2001 Fig 8; http: //www. ucar. edu/news/releases/2005/wrf. shtml; http: //en. wikipedia. org/wiki/Global_climate_model

Hierarchy of atmospheric models • Considerations: – Purpose – Speed v. Complexity research forecast Process Models Limited-Area Models Global Models turbulence weather systems climate states balance regional climate paleoclimate hurricane intensity hurricanes global warming seasonal forecasts short-term weather climate extremes Ooyama 2001 Fig 8; http: //www. ucar. edu/news/releases/2005/wrf. shtml; http: //en. wikipedia. org/wiki/Global_climate_model

Hierarchy of atmospheric models • Considerations: – Purpose – Speed v. Complexity research forecast Process Models Limited-Area Models Global Models turbulence weather systems climate states balance regional climate paleoclimate hurricane intensity hurricanes global warming seasonal forecasts short-term weather climate extremes Ooyama 2001 Fig 8; http: //www. ucar. edu/news/releases/2005/wrf. shtml; http: //en. wikipedia. org/wiki/Global_climate_model

Hierarchy of atmospheric models • Considerations: – Purpose – Speed v. Complexity research forecast Process Models Limited-Area Models Global Models turbulence weather systems climate states balance regional climate paleoclimate hurricane intensity hurricanes global warming seasonal forecasts short-term weather climate extremes Ooyama 2001 Fig 8; http: //www. ucar. edu/news/releases/2005/wrf. shtml; http: //en. wikipedia. org/wiki/Global_climate_model

Complexity – Model Resolution • Spatial – Horizontal – Vertical • Temporal x-Δx x x+Δx http: //www. progonos. com/furuti/Map. Proj/Cart. Index/cart. Index. html; http: //www. climateprediction. net/science/model-intro. php; http: //en. wikipedia. org/wiki/Platonic_solid

Complexity – Parameterizations • Choices based on purpose, understanding, resolution: – Dry or moist – Friction or no friction – Subgrid processes • Cloud microphysics • Convection • Radiation • Land Surface

Example – Global Model • Defining the Purpose • Defining the System • Making Assumptions • Specifying the Equations • Determining Method of Solution • Evaluating Results Example developed from IPCC AR 4

Global Model – Purpose • Understanding the climate system • Predicting future climate • Evaluating climate sensitivity to anthropogenic forcing (read: human impacts on climate) Can we reproduce the global mean temperature trend over the past decade?

Global Model – Defining the system Conceptual model – Energy balance IPCC AR 4 WG 1 Ch 1 FAQ 1. 1 Fig 1

Global Model – Defining the system Conceptual model – Processes IPCC AR 4 WG 1 Ch 1 FAQ 1. 2 Fig 1

Global Model – Making assumptions IPCC AR 4 WG 1 Ch 1 Fig 1. 2

Global Model – Specifying the equations Determining method of solution • We already decided that we want to use a Global Model, but which one? • Each has pluses and minuses Acronym Soup NICAM BUGS IGCM AFES CCSM

Global Model – Evaluating results • Comparisons: – – – Theory Models Observations Global mean temperature predicted by different models, compared with observations. IPCC AR 4 WG 1 Ch 1 Fig 1. 1

Questions? http: //en. wikipedia. org/wiki/Dymaxion_map