ESOP-95 ARM-CART Upper Air Sounding Dataset 1.0 General Description This is one of the upper air sounding datasets developed for the GEWEX Continental scale International Project (GCIP) 1995 Enhanced Seasonal Observing Period (ESOP-95) conducted from 1 April to 30 September 1995. Included in this dataset are five Atmospheric Radiation Measurement - Clouds And Radiation Testbed (ARM-CART) sounding stations; Lamont (Central Facility), Morris (B5), Purcell (B6), and Vici (B4) OK and Hillsboro (B1) KS. The area covered by the ESOP-95 experiment extends from approximately 91W to 107W longitude and 31N to 40N latitude. 2.0 Detailed Data Description 2.1 Data Remarks ARM-CART files from 1 April through 30 September were delivered as two separate files, one wind file and one thermodynamic file. These files were merged by OFPS to create a final sounding for each pair of files. These files have two-second vertical resolution thermodynamic data and 10-sec vertical resolution wind data. At each of the boundary facilities (B1, B4, B5, and B6) soundings were typically released once per weekday at 1800 UTC and at the central facility five times per weekday at 06, 12, 15, 18, and 21 UTC. However, during Intensive Observing Periods (IOPs) the sounding frequency increased to up to 8 per day (3-hourly; including weekends) at each of the sites. 2.2 OFPS Quality Control Format (ASCII-only) Description 2.2.1 Header records The header records (15 total records) contain data type, project ID, site ID, site location, release time and ascension number. The first five header lines contain information identifying the sounding, and have a rigidly defined form. The following 6 header lines are used for auxiliary information and comments about the sounding, and they vary significantly from dataset to dataset. The next line (line 12) contains the Nominal date and time of the release. The last 3 header records contain header information for the data columns. Line 13 holds the field names, line 14 the field units, and line 15 contains dashes ('-' characters) delineating the extent of the field. The six standard header lines are as follows: Line Label (fixed to 35 char in length) Contents 1 Data Type: Description of type and resolution of data. 2 Project ID: ID of weather project. 3 Launch Site Type/Site ID: Description of launch site. 4 Launch Location (lon,lat,alt): Position of launch site, in format described below. 5 UTC Launch Time: Time of release, in format: yyyy, mm, dd, hh:mm:ss 12 UTC Nominal Launch Time: Nominal release time. The release location is given as: lon (deg min), lat (deg min), lon (dec. deg), lat (dec. deg), alt (m) Longitude in deg min is in the format: ddd mm.mm'W where ddd is the number of degrees from True North (with leading zeros if necessary), mm.mm is the decimal number of minutes, and W represents W or E for west or east longitude, respectively. Latitude has the same format as longitude, except there are only two digits for degrees and N or S for north/south latitude. The decimal equivalent of longitude and latitude and station elevation follow. The seven non-standard header lines may contain any label and contents. The label is fixed to 35 characters to match the standard header lines. As mentioned above, line 12 has been used for the nominal release date and time. Sample header records are provided in the sample data file in section 2.2.3. 2.2.2 Data records The data records each contain time from release, pressure, temperature, dew point, relative humidity, U and V wind components, wind speed and direction, ascent rate, balloon position data, altitude, and quality control flags (see QC code description). Each data line contains 21 fields, separated by spaces, with a total width of 130 characters. The data are right-justified within the fields. All fields have one decimal place of precision, with the exception of latitude and longitude, which have three decimal places of precision. The contents and sizes of the 21 fields that appear in each data record are as follows: Field Format Missing No. Width Parameter Units Value ---------------------------------------------------------------------- 1 6 F6.1 Time Seconds 9999.0 2 6 F6.1 Pressure Millibars 9999.0 3 5 F5.1 Dry-bulb Temperature Degrees C 999.0 4 5 F5.1 Dew Point Temperature Degrees C 999.0 5 5 F5.1 Relative Humidity Percent 999.0 6 6 F6.1 U Wind Component Meters/Second 9999.0 7 6 F6.1 V Wind Component Meters/Second 9999.0 8 5 F5.1 Wind Speed Meters/Second 999.0 9 5 F5.1 Wind Direction Degrees 999.0 10 5 F5.1 Ascension Rate Meters/Second 999.0 11 8 F8.3 Longitude Degrees 9999.0 12 7 F7.3 Latitude Degrees 999.0 13 5 F5.1 Variable (see below) 999.0 14 5 F5.1 Variable (see below) 999.0 15 7 F7.1 Altitude Meters 99999.0 16 4 F4.1 QC flag for Pressure Code (see below) 99.0 17 4 F4.1 QC flag for Temperature Code (see below) 99.0 18 4 F4.1 QC flag for Humidity Code (see below) 99.0 19 4 F4.1 QC flag for U Component Code (see below) 99.0 20 4 F4.1 QC flag for V Component Code (see below) 99.0 21 4 F4.1 QC flag for Ascension Rate Code (see below) 99.0 ---------------------------------------------------------------------- Fields 13 and 14 are `variable' because depending on the sounding system the variables used in these positions can vary. For the ARM/ CART soundings these fields have been set to missing. Fields 16 through 21 contain the Quality Control information (flags) generated locally at OFPS. These flags are based on the automatic or visual checks made. See Section 3.0 for further information. The OFPS QC flags are as follows: Code Description ------------------------------------------------------------------------ 99.0 Unchecked (QC information is `missing.') (`UNCHECKED') 1.0 Checked, datum seems physically reasonable. (`GOOD') 2.0 Checked, datum seems questionable on physical basis. (`MAYBE') 3.0 Checked, datum seems to be in error. (`BAD') 4.0 Checked, datum is interpolated. (`ESTIMATED') 9.0 Checked, datum was missing in original file. (`MISSING') ------------------------------------------------------------------------ 2.1.3 Sample data The following is a sample portion of an OFPS QCF file including header records. The data portion is much longer than 80 characters and, therefore, wraps around to a second line. Data Type: ARM-CART Sounding. Project ID: 2 Launch Site Type/Site ID: C1 : Central_Facility Launch Location (lon,lat,alt): 97 29.40'W, 36 36.60'N, -97.5, 36.6, 315.0 GMT Launch Time (y,m,d,h,m,s): 1995, 09, 06, 05:30:00 Nominal Launch Time (y,m,d,h,m,s): 1995, 09, 06, 06:00:00 Time Press Temp Dewpt Rh Ucmp Vcmp Spd Dir Wcmp Lon Lat Ele Azi Alt Qp Qt Qrh Qu Qv Qdz Sec mb C C % m/s m/s m/s deg m/s deg deg deg deg m code code code code code code ------ ------ ----- ----- ----- ------ ------ ----- ----- ----- -------- ------- ----- ----- ------- ---- ---- ---- ---- ---- ---- 0.0 977.3 25.0 21.3 80.0 -2.4 2.0 3.1 130.0 999.0 -97.490 36.610 999.0 999.0 315.0 2.0 2.0 2.0 99.0 99.0 9.0 2.0 975.6 25.3 21.4 79.0 9999.0 9999.0 999.0 999.0 7.5 -97.490 36.610 999.0 999.0 330.0 2.0 2.0 2.0 9.0 9.0 99.0 4.0 974.9 25.5 21.4 78.0 9999.0 9999.0 999.0 999.0 3.5 -97.490 36.610 999.0 999.0 337.0 2.0 2.0 2.0 9.0 9.0 99.0 6.0 973.7 25.8 21.5 77.0 9999.0 9999.0 999.0 999.0 5.0 -97.490 36.610 999.0 999.0 347.0 2.0 2.0 2.0 9.0 9.0 99.0 8.0 972.3 26.0 21.5 76.0 9999.0 9999.0 999.0 999.0 6.5 -97.490 36.610 999.0 999.0 360.0 2.0 2.0 2.0 9.0 9.0 99.0 . . . etc. 3.0 Quality Control Processing ARM-CART soundings were quality controlled by the ARM program (Lesht 1995) and provided to UCAR/OFPS by the ARM-CART Project. This dataset underwent an OFPS QC process which consisted of internal consistency checks. This included gross limit checks on all parameters and vertical consistency checks on temperature, pressure, and ascent rate. OFPS did not perform visual quality control procedures on this data. However, spot checks of soundings at each site were conducted to examine for problems. 3.1 Gross Limit Checks These checks were conducted on each sounding and data were automatically flagged as appropriate. Only the data point under examination was flagged. OFPS conducted the following gross limit checks on the ARM/CART sounding dataset. In the table P = pressure, T = temperature, RH = relative humidity, U = U wind component, V = V wind component, B = bad, and Q = questionable. ---------------------------------------------------------------- Parameter(s) Flag Parameter Gross Limit Check Flagged Applied ---------------------------------------------------------------- Pressure < 0 mb or > 1030 mb P B Altitude < 0 m or > 35000 m P, T, RH Q Temperature < -80C or > 45C T Q Dew Point < -99.9C or > 30C RH Q > Temperature T, RH Q Relative Humidity < 0% or > 100% RH B Wind Speed < 0 m/s or > 100 m/s U, V Q > 150 m/s U, V B U Wind Component < 0 m/s or > 100 m/s U Q > 150 m/s U B V Wind Component < 0 m/s or > 100 m/s V Q > 150 m/s V B Wind Direction < 0 deg or > 360 deg U, V B Ascent Rate < -10 m/s or > 10 m/s P, T, RH Q ---------------------------------------------------------------- 3.2 Vertical Consistency Checks These checks were conducted on each sounding and data were automatically flagged as appropriate. These checks were started at the lowest level of the sounding and compared neighboring 6-sec averaged values to reduce the flagging frequency of the checks. In the case of checks ensuring that the values increased/decreased as expected, only the data point under examination was flagged. However, for the other checks, all of the data points used in the examination were flagged. All items within the table are as previously defined. ---------------------------------------------------------------- Vertical Consistency Parameter(s) Flag Parameter Check Flagged Applied ---------------------------------------------------------------- Time decreasing/equal None None Altitude decreasing/equal P, T, RH Q Pressure increasing/equal P, T, RH Q > 1 mb/s or < -1 mb/s P, T, RH Q > 2 mb/s or < -2 mb/s P, T, RH B Temperature < -15 C/km P, T, RH Q < -30 C/km P, T, RH B > 5 C/km (not applied at p , 150mb) P, T, RH Q < 30 C/km (not applied at p , 150mb) P, T, RH B Ascent Rate change of > 3 m/s or < -3 m/s P Q change of > 5 m/s or < -5 m/s P B ---------------------------------------------------------------- 3.3 Data Quality Issues The B6 (Purcell, OK) winds appear to be much more erratic than those at the other sites. OFPS only applied the simple extreme value checks shown above, and thus many problem winds can pass through without being flagged. B6 had over 10 times as many flagged wind errors per data point as the other sites. Also, the soundings at each site for the month of April 1995 were visually examined (not visually quality controlled, however) and the same conclusion was reached. Some examples of these problems can be seen in the B6 soundings at 18 UTC on 3 April and at 03 UTC on 22 April. Thus, OFPS recommends that the winds from B6 be used with some caution. The B4 (Vici, OK) soundings had much higher numbers of superadiabatic and strong inversion layers than the other sites. The other sites had 0.5 - 1.2% of all data points registering as superadiabatic (< -15 C/km). These values were typical of soundings from other projects. B4, however, had 4.2% of all data points registering as superadiabatic. Data from each of the months had higher percentages of superadiabatic layers than the other sites (the lowest monthly percentage at B4 was 2.4% in April). The problem was most pronounced in a period from mid July through early August (during an IOP; there was a similar increase in superadiabatic layers during late September as another IOP started, however, during the April-May IOP no such increase was evident). During this time the percentages of superadiabatic data points increased to 7.3% in July and 5.2% in August. The percentage of strong inversions also increased during this time. The percentage of all errors that were superadiabatic or large inversion layers increased from the typical value of about 80% to about 93% during July and August. The percentage of rapid ascent rate changes (3 m/s for consecutive 6-sec average layers) also increased, while other error types were largely unchanged. Also, these errors were not concentrated in the lower values. For example, about 60% of the B1 superadiabatic layers were 15-20 C/km, while at B4 this dropped to about 50%. Thus the errors increased in number and severity relative to those at the other sites. Similar problems did occur at other sites, but not as frequently. Some examples of these problems can be seen in the B4 soundings at 1800 UTC on 19 July and 06 UTC on 22 July as well as the B1 sounding at 0300 on 1 August. Thus, OFPS recommends that the user examine the flags applied to the data. All of the sites had many soundings with limited (< 100 mb depth near the surface) or no humidity values. One month of data from each site was visually examined to determine the extent. It was found that each site had soundings fitting this description: B1 20 of 115 17.4% B4 21 of 117 17.9% B5 3 of 116 2.6% B6 19 of 111 17.1% C1 5 of 159 3.1% All of the soundings that had some humidity data but with the early cutoff had relative humidity values of 100% for a significant period of time prior to the cutoff. In other cases, however, some soundings had 100% relative humidity values for lon periods without being cutoff. Also, in a general sense, there appears to be a rather large amount of saturated conditions. 4.0 References Lesht, B. M., 1995: An evaluation of ARM radiosonde operational performance. Preprint Volume, Ninth Symposium on Meteorological Observations and Instrumentation, American Meteorological Society, Charlotte, North Carolina.