1) In the tropics the climate conditions are to a high degree determined by the Inter-Tropical Convergence Zone (ITCZ).

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1 Exam in Climatology 1ME403, , 8-13 h Mini-calculator and mathematical-physical handbook may be used Teacher: Hans Bergström Maximum: =60 points 1) In the tropics the climate conditions are to a high degree determined by the Inter-Tropical Convergence Zone (ITCZ). a) Draw on the map the average positions of ITCZ over the Atlantic and over Northern Africa during January and during July. Discuss the reasons for the seasonal differences and for the differences between land and sea. (6 p) b) Show in a couple of sketches (vertical cross-sections from north to south) the structure of ITCZ over the Atlantic and over Sahara in Northern Africa. Show the typical cloud-, precipitation- and wind conditions that accompany ITCZ and surrounding areas. (4 p) c) Compare the seasonal migrations of the tropical convergence zone over the Atlantic and over the Indian Ocean. Discuss the reasons to what is observed. (4 p)

2 2) In the table below the maximum daily precipitation for July in Uppsala have been binned: mm No. of observations 0,0-4,9 6 5,0-9, ,0-14, ,0-19, ,0-24, ,0-29, ,0-34, ,0-39,9 5 40,0-44,9 4 45,0-49,9 0 50,0-54,9 0 55,0-59,9 3 a) Calculate and draw a figure showing the cumulative distribution. Use this information to estimate the probability for the maximum daily precipitation in July to be below 5 mm respectively above 50.0 mm. Also define and determine the median value and the upper and lower quartiles. (6 p) b) Theoretically define the arithmetic average value and the standard deviation, and determine those for the observed maximum daily precipitation in July. Determine the 95 % and the 99 % confidence limit for the average using these results. The calculations should be motivated. (5 p)

3 3) We will consider some aspects regarding angular momentum and energy balance of the earth/atmosphere system. a) The figure below may be related to the maintenance of the atmospheric angular momentum. Describe shortly what is shown in the figure. Give an explanation to the observed variations with latitude and the differences between winter and summer. Explain, based upon classical physics, what conclusions we may draw from what is shown in the figure regarding the meridional (north-south) transport of angular momentum. (5 p) N/m 2 c) To maintain the temperature climate energy need to be transported by the earth-atmosphere system in meridional (north-south) direction and in vertical direction. Describe why and discuss the mechanisms which are used by the climate system to accomplish this in different parts of the atmosphere. The figure below may be used as guidance for the discussion. Explain the physical meaning of the boxes and arrows. (6 p)

4 4) The temperature has been measured during a number of years at two nearby sites A and B, located on the countryside and in the same type of terrain. The resulting annual average temperatures ( C), given in the table below, will be studied. A: 5,5 6,1 6,0 5,2 4,9 5,7 6,1 5,4 5,4 5,7 B: 4,9 5,7 5,5 4,8 4,3 5,5 6,2 5,4 5,6 5,6 a) Make a simple judgment of the first 10 years of the measurements regarding their reliability. A graph showing the data may be useful. Describe the background for your judgment. (2 p) b) Calculate the average for site A and site B considering your judgment made above. A motivation should be given. (2 p) c) Draw the frequency distribution (a histogram) and the cumulative frequency distribution for site A using a suitable binning of the data. Define and determine the modal (or typical) value, the probability that the annual average temperature will be below 5 C, and the probability that the average temperature will be above 6 C. (4 p) d) Calculate for site A, assuming that the normal distribution may be used, the same probabilities that the annual average temperature will be below 5 C or that it will be above 6 C. Motivate your results. Compare with the results in c) and discuss possible differences. (4 p)

5 5) We are going to describe some aspects of the climate in South America by drawing some maps. All results should also be shortly discussed and explained, not only shown on the maps. a) Draw on map a) the average winds and the average location of ITCZ and polar fronts in January. (4 p) b) Some as a) but for July on map b). (4 p) c) Draw on map c) the important cold and warm ocean currents, and areas with desert climate in South America. Explain why deserts are found at these locations. (4 p)

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