Turbulence in the Atmospheric Boundary Layer

Aim and Content

An introduction into turbulence and turbulent energy fluxes in the atmospheric boundary layer is given in this course. This introduction is intended to provide a basis for further advanced studies in this field. It also aims to give students a sufficient background for assessing the relative importance and relevance of turbulence in other issues related to meteorology or climate. The course covers homogenous turbulence theory including spectral descriptions, definition and measurement of turbulent fluxes and the influence of stratification in the boundary layer in the atmosphere. Starting from the basic equations of conservation and using appropriate scaling arguments and approximations, a set of equations valid for boundary layer flow is derived. Based on that prognostic equations for the mean variables in turbulent flow and for covariances and variances are deduced. Based on the latter. The budget equation for the turbulent kinetic energy is derived as well and the different terms are discussed. Salient features of various processes in the atmospheric boundary layer are introduced. The profiles of scalars, such as temperature, humidity, and tracer concentration as well as velocity and their respective turbulent fluxes in the atmosphere are described and discussed in different forcing conditions. The turbulence closure problem is discussed and the most common local and non-local closure approaches are introduced. Specific mathematical methods related to the description of turbulence, as FFT and Buckingham-Pi analysis in similarity theory are shortly covered. An overview over the common instruments and measurement methods is given, as well as a short introduction in Large Eddy Simulation as turbulence modeling tool.

Learning Outcomes

Upon completing GEOF311 the student should be able to:

- describe and compare the salient features of the turbulent boundary layer in the atmosphere

- identify and sketch the profiles of tracers and turbulent fluxes in the boundary layer in the atmosphere under different forcing conditions

- explain and discuss the different terms of the budget equations for turbulence

- sketch an idealized energy spectrum and discuss the different subranges

- explain the turbulence closure problem and sketch different methods for its solution

- choose instrumentation and sampling scheme to measure turbulence fluxes in the atmosphere

- calculate and interpret turbulent key parameters as fluxes and turbulent kinetic energy, using direct and indirect methods, from a corresponding data set.

Course offered (semester)

Autumn

Language of Instruction

English, Norwegian if only Norwegians students

Department

Geophysical Institute

Pre-requirements

Bachelor in meteorology and oceanography or equivalent programs.

Recommended previous knowledge

GEOF220, or equivalent.

Subject Overlap

GEOF310: 5 ECTS

Teaching Methods

2 lectures á 2+1 hours per week

1 exercise á 1 hour per week

Compulsory Requirements

Approved exercises.

Assessment methods

Oral exam. If more than 15 candidates, the exam might be written. No auxiliaries allowed for the exam.

Grading Scale

The grading scale used is A to F. Grade A is the highest passing grade in the grading scale, grade F is a fail.

Contact Information

Study advisor Geophysical Institute: studierettleiar@gfi.uib.no