ATOC 309: Weather Radars and Satellites Midterm Test
ATOC 309: Weather Radars and Satellites Midterm Test – 20 February 2015 This exam is marked out of 50 points. Note that the number of points each question is worth varies from question to question. This test comprises 3 pages. Answer all six questions. Translation dictionaries and protractors are permitted. No other aids are allowed. Short Answer Questions A1) (8 pts) What are the names of the four scattering regimes we have covered in class, and under what conditions do they apply? In addition, provide an example of a target that would qualify for each of those scattering regimes for a W-band radar (λ=3 mm). A2) (8 pts) What are radar products? Excluding the PPI, name and briefly describe two radar products. A3) (8 pts) Sometimes, the amount of ground echo observed on a radar picture increases significantly for a period of a few to several hours. Why should it change at all? Describe the meteorological conditions under which this can occur. A4) (6 pts) The following figures show a low-level Doppler PPI on the left, with a small portion zoomed on the right. The radar is annotated by a cross labelled EAX. Two small-scale signatures are observed, one originally circled and labelled “Couplet” and a smaller one inside the “couplet” within a rectangle. What are the signatures in those two areas? What causes them meteorologically speaking?
Case Study One day in February, southern Oklahoma: A winter storm is expected, the official forecast calling for a possible mix of snow, ice pellets, and freezing rain. B1) (6 pts) On the right is a Doppler PPI at 2.5° elevation. Range rings correspond to altitudes of 1, 2, and 3 km. Derive the mean winds at those three altitudes.
B2) At the same time, 2.5° PPIs of Z, Zdr, and ρco were also obtained and are plotted here. The small red lozenge shows the location of the radar. (10 pts) Based on the available information, what type of targets is observed by the radar at A at the altitude where measurements are taken (about 1 km above the surface)? Justify your assessment. (4 pts) And what type of precipitation do you expect to see at the surface under A? Briefly explain your reasoning (4 points).
A
Case Study One day in February, southern Oklahoma: A winter storm is expected, the official forecast calling for a possible mix of snow, ice pellets, and freezing rain. B1) (6 pts) On the right is a Doppler PPI at 2.5° elevation. Range rings correspond to altitudes of 1, 2, and 3 km. Derive the mean winds at those three altitudes.
B2) At the same time, 2.5° PPIs of Z, Zdr, and ρco were also obtained and are plotted here. The small red lozenge shows the location of the radar. (10 pts) Based on the available information, what type of targets is observed by the radar at A at the altitude where measurements are taken (about 1 km above the surface)? Justify your assessment. (4 pts) And what type of precipitation do you expect to see at the surface under A? Briefly explain your reasoning (4 points).
A
