Computation of zonal (u) and meridional (v) components. Useful websites.

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1 UNIVERSITY OF NAIROBI COLLEGE OF BIOLOGICAL AND PHYSICAL SCIENCES School of Physical Sciences Bachelor of Science in Meteorology Weather Analysis (SMR 204) Practical Manual for Academic Year 2014/15 (ODL GROUP 3L) Written By: Prof. Ininda J. M Department of Meteorology University of Nairobi

2 INTRODUCTION TO PRACTICALS IN WEATHER ANALYSIS The series of practical in WEATHER ANALYSIS are aimed at equipping the students with practical skills in current practices of weather analysis and computational skills. PRACTICAL TIME TABLE (SMR /15) SERIAL NO. DESCRIPTION DATE DUE FOR HANDING IN Practical - 01 Computation of zonal (u) and meridional (v) components Allocation of percentage Marks Practical - 02 Practical - 03 Practical 04 Practical - 05 Practical - 06 Practical - 07 Practical - 08 Computation speed and direction Isogon Streamline Anaysis Streamline-Isotach Analysis Decoding the weather message Plotting SYNOP report on the weather Chart Coding upper air the weather message Plotting the sounding on a T CAT March 2015 TOTAL MARKS Useful websites (For upper air wind and Temperature coding)

3 PRACTICAL 1: COMPUTATION OF ZONAL (u) and MERIDIONAL (v) COMPONENTS Objective: The practical is aimed at enabling the student compute the zonal and meridional wind components given the speed and direction. Tools a) A table of speed and direction b) Lecture Notes c) Excel software Procedure: Compute the zonal and meridional wind component at various levels given in table 1 Procedure: Compute the zonal and meridional wind component at various levels given in table 1 The zonal and meridional components are given by u V sin(dir) v V cos(dir) Where V TABLE 1 DATA FOR PRACTICAL NO 1 TABLE 1: Speed and Direction Given station DIR SPEED U V station DIR SPEED U V S S S S S S S S S S S S S S S S S S S S S S S S S S S S

4 S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S PRACTICAL 2: COMPUTATION SPEED AND DIRECTION Objective: The practical is aimed at enabling the student compute the speed and direction given the zonal and meridional wind components.. Tools a) A table of zonal and meridional wind components. b) Lecture Notes Procedure: Compute the speed and direction using the zonal and meridional wind component at various levels given in table 2. Use excel Software The speed is given by the equation 2 2 SP u v where SP is the speed, u the zonal wind and v the meridional wind. (a) Computation of Direction

5 The wind direction is define as the direction from where the wind is coming from. It is measure from the true north clockwise. When the wind is blowing from west (east), the u (zonal) component is positive (negative). While when the wind is blowing from south (north), the v (meridional) component is positive. To compute the direction were consider the four quadrants; Case 1: u<0 and v<0 The angle of the direction is between 0 o and 90 o and is given by 1 u dir tan ABS v or 1 v dir 90 tan ABS u Case 2: u<0 and v>0 The angle of the direction is between 90 o and 180 o and is given by 1 u dir 180 tan ABS v or 1 v dir 90 tan ABS u Case 3: u>0 and v>0 The angle of the direction is between 18 0 o and 270 o and is given by 1 u dir 180 tan ABS v or 1 v dir 270 tan ABS u Case 4: u>0 and v<0 The angle of the direction is between 270 o and 360 o and is given by

6 1 u dir 360 tan ABS v or 1 v dir 270 tan ABS u Table 2: Zonal and meridional components Given TIME 7.5N 7.5S U V SPEED DIRECTION U V SPEED DIRECTION Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May

7 PRACTICAL 03: ISOGONAL STREAMLINE ANALYSIS Objective: The practical is aimed at enabling the student gain skill in analysing wind using isogonstreamline method. Definition: Streamlines: Streamlines are lines that are tangential to the flow at a given instant of time Isogons: Isogons are lines joining points of equal direction Singular points: Singular points are points to which more than one streamlines can be drawn or about which streamlines form a closed curve. Tools: The data of wind direction is given on the chart (Figure 1) Procedure: (i) Draw isogons for 360 0,90 0, and (ii) Locate singular points (iii)draw intermediate isogons at 30 0 interval, smoothen the lines (iv) Refine the position of the singular points. (v) Draw short segments of streamlines along each isogon, (vi) Starting at the edge of the chart draw smooth streamlines, ensuring thsat each isogon is parallel to short segments (vii)where two streamlines diverge you may start another between them (viii) Where two streamline flow together join them smoothly

8 Figure 1. The spatial distribution of wind direction (DATA FOR PRACTICAL 03)

9 PRACTICAL 04: STREAMLINE-ISOTACH ANALYSIS Objective: The practical is aimed at enabling the student gain skill in analysing wind using streamlineisotach method. Definition: Isotach Isotach are lines joining points of equal wind speed Singular points: Tools: The wind data is given on the chart (Figure 2) Procedure: Draw two sets of lines, the streamlines and isotachs Streamline: Starting at the edge of the chart draw smooth streamlines, ensuring thsat each isogon is parallel to wind vector. Where two streamlines diverge you may start another between them Where two streamline flow together join them smoothly Identify singular points Isotach Determine a suitable interval and draw the isotachs.

10 Figure 2: The spatial distribution of wind (DATA FOR PRACTICAL 04)

11 PRACTICAL 5: DECODING THE WEATHER MESSAGE Objective: The practical is aimed at enabling the student decode the weather messages a) A table of coded weather messages b) The lecture notes Tools a) Extract the SYNOP REPORT for the station and date and time allocated to you.. For example to obtain data for 00GMT for 16 th April 2014 enter the information as shown.

12 Reg. No. Station TIME 1200GMT Lodwar Marsabit Kitale Wajir Kisumu Nyeri Embu Nairobi voi Mombasa Eldoret TIME 1500GMT Lodwar Marsabit Kitale Wajir Kisumu Nyeri Embu Nairobi voi Mombasa Eldoret PRACTICAL 6: PLOTTING THE WEATHER INFORMATION ON A CHART Objective: The practical is aimed at enabling the student plot on a weather chart. Tools a) A table of coded weather messages b) Lecture Notes

13 c) A chart (map) with station indicated on it Procedure: Plot the weather messages for the stations over Kenya date and time you were allocated REG. NO. & NAME MONTH, DATE AND TIME 12 GMT 15 TH APRIL GMT 15 TH APRIL GMT 16 TH APRIL GMT 16 TH APRIL GMT 17 TH APRIL GMT 17 TH APRIL GMT 18 TH APRIL GMT 18 TH APRIL GMT 19 TH APRIL GMT 19 TH APRIL GMT 20 TH APRIL GMT 20 TH APRIL GMT 21 ST APRIL GMT 21 ST APRIL GMT 22 ND APRIL GMT 22 ND APRIL GMT 23 RD APRIL GMT 23 RD APRIL GMT 24 TH APRIL GMT 24 TH APRIL GMT 25 TH APRIL GMT 25 TH APRIL GMT 27 TH APRIL GMT 27 TH APRIL GMT 28 TH APRIL GMT 28 TH APRIL GMT 29 TH APRIL GMT 29 TH APRIL GMT 30 TH APRIL GMT 30 TH APRIL 2014 (N B. You will need to print out the figure1)

14 Figure 3: The Synoptic stations over Kenya

15 PRACTICAL 7: CODING THEUPPER AIR OBSERVED WEATHER Objective: The practical is aimed at enabling the student code the observed weather a) A table of observed weather b) The lecture notes Procedure: Code the weather message give in table 2 TABLE 2 Sounding for station n at 15hr local time and the station is located at 75 O E. The radio sonde launched at 14hr 30min local time. Pressure level(mb) Geopotential Height (m) Temperature o C Dew point Temp C Wind speed Kt Direction

16 PRACTICAL NO. 8: PLOTTING THE SOUNDING ON A T Objective: The practical is aimed at enabling the student to plot the sounding on T And compute the convective parameters. Tools a) Extract the TEMP data for the station and date allocated to you at 00 GMTor 23 GMT For example to obtain data for 23GMT for 14 th April 2010 enter the information as shown. a) Using a T (i) Plot the given temperature and dew point temperature a T gram and Indicate the layers that experienced warming/ cooling and moistening / drying. (ii) Determine the LCL, equivalent potential temperature, lifted Index. (iii) Find the mixing ratio, specific humidity,,relative humidity and vapour pressure at surface, 800mb,700mb, 600mb, 500mb, and 400mb

17 REG. NO. & NAME MONTH, DATE AND TIME 23 GMT 14 TH &15 TH APRIL GMT 14 TH & 15 TH APRIL GMT 16 TH & 17 TH APRIL GMT 16 TH & 17 TH APRIL GMT 18 TH & 19 TH APRIL GMT 18 TH & 19 TH APRIL GMT 20 TH & 21 ST PRIL GMT 20 TH & 21 ST APRIL GMT 22 ND & 23 RD APRIL GMT 22 ND & 23 RD APRIL GMT 24 TH & 25 TH APRIL GMT 24 TH & 25 TH APRIL GMT 26 TH & 27 TH APRIL GMT 26 TH & 27 TH APRIL GMT 28 TH & 29 TH APRIL GMT 28 TH & 29 TH APRIL GMT 30 TH APRIL & 1 ST MAYL GMT 30 TH APRIL & 1 ST MAY GMT 14 TH &15 TH APRIL GMT 14 TH & 15 TH APRIL GMT 16 TH & 17 TH APRIL GMT 16 TH & 17 TH APRIL GMT 18 TH & 19 TH APRIL GMT 18 TH & 19 TH APRIL GMT 20 TH & 21 ST PRIL GMT 20 TH & 21 ST APRIL GMT 22 ND & 23 RD APRIL GMT 22 ND & 23 RD APRIL GMT 24 TH & 25 TH APRIL GMT 24 TH & 25 TH APRIL 2009 (N B. You will need to print out the figure1) Synop of a landstation The basic form of the SYNOP bulletin for a landstation is: AAXX YYGGiw IIiii irixhvv Nddff 1snTTT 2snTdTdTd 4PPPP 5appp 6RRRtR 7wwW1W2 8NhCLCMCH The rain group (6RRRtR) is not plotted. All other groups will be plotted using the plot model in

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