A Simple Model of Atmospheric developments during El-Nino

1. A Simple Model of Atmospheric developments during El-Nino Mentor: doc dr. Nedjeljka Žagar Author: Aljoša Slameršak

2. Structure of my seminar Description of El Nino. Significance and impacts of El Nino Southern Oscillation. Presentation of the model. Interpretation of model’s results and their coherence with measurements. Advanced models.

3. Definition and description of El Nino El Niño (EN) is characterized by a large scale weakening of the trade winds and warming of the surface layers in the eastern and central equatorial Pacific Ocean. (NOAA definition). It is a quasiperiodic occurance (t : 2-7 years) The expression was coined in 19th century, as the warm currents around Peru become most intense around christmas. East – west overturning of sea surface Temepratures / Source: Holton

4. Development of El-Nino Rise of sea surface pressure over Australonesia and fall over eastern pacific. Easterly trade winds weaken over the Pacific or change direction towards west. This change of wind stress excites Kelvin waves, which transfer the warm waters towards Eastern Pacific. This results in percipitation suprpluss over eastern and deficit over western part of the Pacific.

5. El Nino animation

6. Effects of El Nino Effects vary, depending on intensity of seasonal occurence Intensification of weather systems developments (hurricanes, droughts). Disruption of fishing, agriculture. Loss of life, infrastructure. Economic damage is measured in billions.

7. The model • Our task is to describe the atmospheric component of El Nino, that is the change of the wind stress, due to temperature changes. • We use simple shallow water equations and continuity equation,which will later be modified accordingly to our assumptions. Shallow water equations

8. Assumptions and transformations: • Lower boundary condition w(0) = 0 • Equatorial beta plane for Coriolis parameter • Geopotential instead of pressure gradients • Linear tranfsormation of variables for time and scale • We obtain a modified set od equations: Pressuposed solution form:

9. The solutions for our homogenous set are: • This is not the end of story. Sofar we have not mentioned any forcing or dissipative terms in equations. However these are crucial even for a rough description of macroscopic atmospheric systems. Hermite polynomial ε stands for Newtonian cooling Q is parameterized heating

10. Parameterization of heating

11. Results and coherence with measurements

16. Advanced models