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CAMEX-4 MIPS SODAR Table of Contents
The University of Alabama in Huntsville (UAH) Mobile Integrated Profiling System (MIPS) includes a 915 MHz Doppler profiler, lidar ceilometer, 12 channel microwave profiling radiometer, Doppler Sodar, Radio Acoustic Sounding System (RASS), Field Mills, and surface observing stations. This dataset consists of data derived from the MIPS SODAR as described below. Instrument DescriptionThe Doppler SODAR operates much in the same manner as a Doppler radar, with the exception of the transmitted frequency. While radars operate transmitting microwaves, SODARs operate by transmitting sound waves, and are used to determine the three dimensional wind field in the lower boundary layer. The UAH MIPS SODAR transmits in the near 2000 Hz frequency range, and is tunable between 1800-2200 Hz. Instead of measuring reflectivity of the raindrops as does the radar, the SODAR transmitted pulse is scattered by fluctuations in the refractive index of the air. Several things may cause these fluctuations; temperature and/or humidity variations or gradients, as well as wind shear. But, because of the geometry of the system the SODAR is mainly sensitive to thermal fluctuations. The strength of the reflected signal depends strongly upon the size of the fluctuations, and is restricted to a value of half the wavelength of the signal (lambda/2). From the movement of the fluctuation (imagine a slight temperature gradient, or bubble as the target) wind direction and speed are determined as the fluctuation moves with the wind field through the beams. Vertical velocities may be derived directly from the vertical beam using the Doppler shift of the received signal. By arranging other sound transmitters orthogonally from each other and tilted at approximately 15 degrees off of vertical, three dimensional wind fields may be calculated. The pulse repetition period is about 6 seconds, and the vertical beam is sampled at periods of about 20 seconds. Input from these samples are combined to produce consensus winds along with the spectral moments along each beam about every 15 minutes. These data also provide information about the boundary layer stability and turbulence characteristics. This dataset consists of cdf and mom files tarred together for a day. The "cdf" file is a consensus data file, and reports 15 minute average 3-D wind profiles from the Doppler SODAR starting at the beginning of each day. The "mom" file is a momentum file and contains data from each beam about radial velocity and backscattter intensity. Each horizontal beam is approximately 7 seconds apart; vertical beams are approximately 21 seconds apart. Data for one day is tarred into a file whose name is of the form c4gmipsod_2001.jjj.tar, where c4gmipsod indicates that the data came from the CAMEX-4 experiment and the ground based MIPS SODAR in the year 2001 on the day of the year jjj. These daily files are then tarred together. When untarred, the data appears in two separate files. The first is named ECH1MMDD.CDF, and the second is ECH1MMDD.MOM where ECH indicates that these are SODAR (or echo sounder) files, 1 indicates the last digit of the year (2001) MMDD is the month and day of the month. The extension CDF or MOM describes this file as either a consensus data file or momentum file as described above. The momentum file contains basic instrument settings, as well as averaged moments and signal to noise ratio data used to calculate the winds aloft provided in the CDF file. Both files are ASCII, and are fairly self evident. And example of the CDF file is shown below. Note that there is a header section that precedes the actual data. The output data then repeats at approximately 15 minute intervals through the dataset. CDF Type: Wind Program: echosonde Version: 3.0.1
Station: echosonde
Date: 09/07/01 Julian Day: 250
Filename: Validation Level: 0.0
Created by: echosonde V. 3.0.1 Created on: 09/07/01 1530
Elev. (m msl): 0000 Elev. (ft msl): 0000
Lat (dec deg): 00.00000 n Long (dec deg): 000.00000 w
UTMN (km): 0000.000 UTME (km): 0000.000
Time Zone: cst Diff. to UTC (hr): 6
Mode Number: 2 Mode Title: Echosonde Winds
Avg. Int. (min): 15 Time Convention End
Pulse Len. (m): 0026 Spacing (m): 25
Max.Samples: 000 000 000 Req. Samples: 000 000 000
Ant. Azimuth (deg): 362 092 092 Ant. Elev. (deg): 075 075 090
QC Code Definition: 0=Valid, 1=Estimated, 7=Suspect, 8=Invalid
Data Code Definition: -940=Failed QC, -950=Failed Consensus,
-960=Exceeded Nyquist Vel., -980=Flagged by Reviewer
-999=Missing or Not Reported
Time # of Gates Radar Parameter Changes
HHMM NNN N
QC Height WS WD u v w No. in Cns SNR (db)
Code (m agl) (m/s) (deg) (m/s) (m/s) (m/s) 3 1 0 3 1 0
1530 27 0
0 50 2.9 56. -2.40 -1.63 1.42 7 8 7 9 8 9
0 75 3.3 52. -2.58 -2.02 -0.06 7 8 7 8 6 8
0 100 3.7 60. -3.18 -1.85 -0.06 7 8 7 7 6 8
0 125 3.8 62. -3.40 -1.79 0.00 7 8 7 6 4 8
0 150 3.3 65. -2.97 -1.41 -0.14 7 8 7 4 4 8
0 175 2.7 54. -2.23 -1.60 -0.09 7 8 7 5 4 8
0 200 3.1 42. -2.10 -2.30 -0.05 7 8 7 3 3 8
8 225 -950.0 -950. 15.97 -1.54 -0.15 7 8 7 4 -3 3
8 250 -950.0 -950. 16.28 -2.73 -0.07 7 8 7 2 -1 -1
8 275 -950.0 -950. 15.78 22.47 -0.06 7 8 7 -5 -6 0
8 300 -950.0 -950. 15.76 17.91 -0.03 7 8 7 1 0 1
8 325 -950.0 -950. 16.14 -8.22 -0.39 7 8 7 -10 -4 -4
8 350 -950.0 -950. 19.78 13.93 1.19 7 8 7 -6 -5 20
8 375 -950.0 -950. -1.06 7.67 4.86 7 8 7 -2 -2 20
8 400 -950.0 -950. 24.37 23.57 -1.68 7 8 7 -2 -3 20
8 425 -950.0 -950. 30.36 31.05 -3.20 7 8 7 -2 -3 -11
8 450 -950.0 -950. -3.36 1.05 4.47 7 8 7 -2 -1 -7
8 475 -950.0 -950. -41.69 -34.96 14.53 7 8 7 -1 -3 20
8 500 -950.0 -950. 39.18 38.31 -5.46 7 8 7 0 0 -7
8 525 -950.0 -950. 33.45 33.76 -4.37 7 8 7 -4 -1 -5
8 550 -950.0 -950. 34.85 34.17 -4.69 7 8 7 -3 -5 -5
8 575 -950.0 -950. -2.80 -2.49 5.16 7 8 7 -1 -2 -5
8 600 -950.0 -950. -8.54 -1.29 5.42 7 8 7 -2 -3 -4
8 625 -950.0 -950. -3.75 3.17 4.84 7 8 7 -1 -3 -13
8 650 -950.0 -950. -5.37 -1.40 5.43 7 8 7 -1 -2 -8
8 675 -950.0 -950. 33.90 -0.03 -4.64 7 8 7 -3 0 -13
8 700 -950.0 -950. -3.42 4.34 4.95 7 8 7 -5 0 -10
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