Enhanced Seasonal Observing Period (ESOP-95) Fixed Class Format Upper Air Sounding Data Set 1.0 General Description This is one of the upper air sounding data sets developed for the GEWEX (Global Energy and Water Cycle Experiment) Continental scale International Project (GCIP). ESOP-95 was conducted from 1 April through 30 September 1995 and initiated the ongoing observations program supporting the South West portion of GCIP's Large Scale area(LSA-SW). ESOP-95's major objective is contributing a comprehensive Data set enabling diagnostic, evaluation, and modeling study. The LSA-SW contains four significant environmental features: large zonal(east - west) climate variability, large low level jet water vapor transport, a major proportion of LSA-SW's precipitation is convectively driven, and there is large diurnal summer season variability in hydrological components such as water vapor transport and convective regimes. ESOP-95 contains upper air soundings from 13 National Weather Service stations listed below. The Data set includes soundings launched at the regular 12 hour intervals: 00Z and 12Z, as well as additional special ascensions specifically for Norman, OK(ON). The final Data set contains 6 second vertical resolution soundings. ESOP-95's aerial coverage extends approximately from 91W to 107W longitude and 31N to 40N latitude. ID Station Name ST Lat/Lon degrees Elev.(m) Record Length total files ******************************************************************************* ABQ Albuquerque NM 35.00 -106.60 1615 950401-950930 365 AMA Amarillo TX 35.20 -101.70 1094 950401-950930 385 DNR Denver CO 39.80 -104.90 1611 950401-950930 356 DDC Dodge City KS 37.80 -100.00 790 950401-950930 372 ELP El Paso TX 31.80 -106.40 1199 950401-950909 324 EPZ Santa Teresa NM 31.90 -106.70 1257 950911-950930 40 FWD FT WORTH TX 32.80 -97.30 198 950401-950930 368 LIT North Little Rock AR 34.80 -92.30 172 950401-950930 365 MAF Midland TX 32.00 -102.20 873 950401-950630 201 UMN Monett MO 36.90 -93.90 438 950401-950517 84 OUN Norman OK 35.20 -97.40 357 950401-950930 374 SHV Shreveport LA 32.50 -93.80 83 950401-950930 352 SGF Springfield MO 37.20 -93.40 390 950519-950930 269 TOP Topeka KS 39.10 -95.60 270 950401-950930 358 There are a total of 14 stations ******************************************************************************* All stations are in the GIST domain On May 17th,1995 Monett(UMN) moved to Springfield(SGF). On September 10th, 1995 , El Paso(ELP) moved to Santa Teresa(EPZ). 2.0 Detailed Data Description 2.0.1 National Weather Service Sounding Algorithms The detailed description of NWS sounding collection and instrumentation is located in Section 2.2 below. 2.1 Detailed Format Description All upper air soundings were originally converted to UCAR/Office of Field Project Support(OFPS) Class Format(OCF). OCF is an ASCII format where a sounding file consists of 15 header records followed by that sounding's data records containing quality control(QC) information. Header Records -------------- The Header records (15 total records) contain data type,project ID, site ID, site location, release time, and comments. The first 5 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 may vary from data set to data set. The next line (line 12) contains the Nominal date and time of the launch. The last 3 header lines contain headers for the data columns, enhancing readability. Line 13 holds the field names, line 14 the field units, and line 15 dashes ('-' characters) delineating the field's extent. The six standard header lines are as follows: Line Label (padded to 35 char) 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 GMT Launch Time (y,m,d,h,m,s): Time of launch, in format: yyyy, mm, dd, hh:mm:ss 12 GMT Nominal Launch Time (y,m,d,h,m,s): Nominal launch time. The launch 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'X where ddd is the number of degrees (with leading zeros if need be), mm.mm is decimal minutes, and X represents W or E for west or east longitude respectively. Latitude has the same format, except there are only two digits for degrees and X represents N or S for north/south latitude. An example of line 4 would thus be: Launch Location (lon,lat,alt): 096 06.60'W, 39 49.80'N, -96.11, 39.83, 384 The seven non-standard header lines may contain any label and contents. As mentioned above line 12 has been used in the sounding composite for the nominal launch date and time. Data Records ------------ The data records (1 record per 6 second interval including surface) 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 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 place precision. The contents and sizes of the fields are detailed below. The 21 fields that appear in each data line are as follows: Field Format No. Width Parameter Unit Missing Flag 1 6 F6.1 Time Seconds 9999.0 2 6 F6.1 Pressure Millibar 9999.0 3 5 F5.1 Dry-bulb Temperature Degrees C 999.0 4 5 F5.1 Dew Point 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 (dZ) 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 for Pressure Code (see below) 99.0 17 4 F4.1 QC for Temperature Code (see below) 99.0 18 4 F4.1 QC for Humidity Code (see below) 99.0 19 4 F4.1 QC for U Component Code (see below) 99.0 20 4 F4.1 QC for V Component Code (see below) 99.0 21 4 F4.1 QC for Ascension Rate Code (see below) 99.0 where Format is the FORTRAN format that could be used to write the field, and Missing Flag is the missing data flag for that field. Note that the missing data flag consists of just enough 9s to fill the field. Note also that there is a space (FORTRAN format 1X) between each field. A FORTRAN 77 FORMAT statement that conforms to the above would be: 100 format(2(2(F6.1,1X),3(F5.1,1X)),F8.3,1X,F7.3,2(1X,F5.1),1X, + F7.1,6(1X,F4.1)) Fields 13 and 14 are "variable" because true CLASS soundings use these fields for range in km and angle in degrees, respectively, which is information unavailable for NWS soundings. NWS soundings do, however, have elevation in degrees and azimuth in degrees, which are used to fill these fields. Processing programs should simply copy the contents of these fields. Fields 16 through 21 contain the OFPS derived Quality Control information. Any QC information from the original sounding is ignored. Currently, field 21 will always be missing. The codes used are as follows: Code Meaning 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") 2.2 Data Remarks NWS soundings during ESOP-95 were of two types: Space Data radiosondes (Amarillo and El Paso TX) and VIZ radiosondes (Denver CO, Dodge City KS, Little Rock AR, Fort Worth TX, Monett MO, Norman OK, Topeka KS, Albuquerque NM, Shreveport LA, and Midland TX). Amarillo and El Paso began using VIZ radiosondes June 1st, 1995. 2.21 Missing Data The missing sounding list only refers to the normal 00Z and 12Z launch times. There may be soundings for these days that were launched at different times. Format of sounding name: YYMMDD HH where YY - year(95), MM - months(04 thru 09), DD - day(01 thru 31) and when applicable HH - hour(00Z or 12Z). When a sounding is not followed by HH, then both the 00Z and 12Z soundings for that date are missing. Albuquerque is missing soundings: 950407 00Z, 950411, 950419 12Z, and 950623 12Z. Amarillo is missing soundings: 950411 12Z thru 950412 12Z, 950513 12Z, and 950626 12Z. Denver is missing soundings: 950518 00Z, 950909 12Z, 950911 thru 950916, and 950919 00Z. Dodge City is missing soundings: 950429 12Z,950525 thru 950529, 950628 12Z thru 950629 12Z, 950808 12Z, and 950926 12Z. El Paso is missing soundings for 950910. Fort Worth is missing soundings: 950429 12Z, 950501 thru 950502 00Z, 950511, 950709 12Z thru 950714 00Z, and 950719 12Z thru 950724 00Z. Little Rock is missing soundings: 950728 00Z thru 950730 00Z and 950807 00Z. Midland is missing soundings: 950402 12Z, 950404 00Z, 950420 12Z, 950527 12Z, 950601 00Z and 950701 thru 950930. We did not receive any sounding data from Midland after 6/30/95. Monett is missing soundings: 950409 00Z, 950419 thru 950424, 950427 thru 950428 00Z, and 950518 thru 950519. 950518 thru 950519 occurred while Monett operations moved to Springfield. Norman is missing soundings: 950701 12Z thru 950704, 950719 12Z thru 950725 00Z, and 950917 12Z. Shreveport is missing soundings: 950421 12Z, 950427 00Z, 950428 thru 950429 12Z, 950515 12Z, 950524 12Z, 950620 12Z thru 950628 00Z, 950705 12Z, and 950822 12Z. Springfield is missing soundings: 950523, 950601, 950608, and 950610 12Z. Topeka is missing soundings: 950531 12Z, 950613 thru 950619 00Z, 950623 12Z thru 950630 12Z, 950726 00Z, 950815 00Z, and 950916 12Z. OFPS applied a correction to the Space Data radiosonde relative humidity(RH) calculations. In the resistance and RH calculations, the NWS Micro-ART sounding system used, instead of the observed temperature, the observed temperature divided by 100. The OFPS applied a correction re-deriving the resistance ratio, using the observed temperature divided by 100 and the observed RH, iterating the so termed "1A" and "1B" coefficients. Now using only the new calculated resistance ratio, the observed temperature and the "1A" coefficients , the new RH was obtained. Also, OFPS implemented a correction to the VIZ radiosonde RH calculations. Using the observed temperature and RH, and iterating both the "1A" and "1B" coefficients, the resistance ratio was re-derived. Using the calculated resistance ratio, the observed temperature and only the "1A" coefficients , the new RH was determined. In both radiosonde types, deriving winds using raw 6-sec resolution elevation and azimuth angle data containing elevation angle oscillations occasionally led to large oscillations in wind velocity, specifically at low elevation angles. The general approach correcting this problem was removing outlier radiosonde position data before computing the wind components. This process required fitting a ninth order polynomial to the azimuth and elevation angle data from 360 seconds to the end of the sounding, then comparing the calculated residuals and observed values, and finally removing the outliers when present. Applying some additional smoothing helped rectify the more extensive problem occurring when low elevation angles were within 10 degrees of the limiting angles (LA). When the elevation angle was between (LA + 7.5) and (LA + 10), the new elevation angle was computed using a 2 min linear fit. When the elevation angle was between (LA + 5) and (LA + 7.5), the new elevation angle was computed using a 3 min linear fit. When the elevation angle was less than (LA + 5), the new elevation angle was calculated employing a 4 min linear fit. No frequency smoothing occurred when the number of low elevation angle observations was greater than 20% of the total number of observations. A Finite Fourier Series analysis performed using the elevation angle's residuals allowed removal of 90-190 second periods and smoothing periods below 30 seconds. Obtaining the u and v wind components entailed fitting a 2 min second order polynomial to the position except for the beginning and end minute (or 1.5 minutes if over 50 mb) which used a 3 min fit. A linear fit was used when there were less than 15% of the total number of points, not including the beginning or end of the flight, on one side of the point under going the wind value calculation. 3.0 Quality Control Processing This data set under went a two-stage QC process. First, an internal consistency check which included two inspections: "reasonable" limit checks on all parameters and rate-of-change checks on temperature, pressure and ascension rate. Secondly, each sounding endured a visual examination verifying those parameters that are too variable for automatic checks: wind speed, wind direction and moisture. In addition, this stage of the QC process allowed verification of the automatic check's QC flags. 4.0 Reference Micro-ART Observation and Rework Programs Technical Document, National Weather Service, National Oceanic and Atmospheric Administration, Washington, D.C., March 1991. Williams, S.F., C.G. Wade, and C. Morel, 1993: A comparison of high resolution radiosonde winds: 6-second Micro-ART winds versus 10-second CLASS LORAN winds. Preprints, Eighth Symposium on Meteorological Observations and Instrumentation, Anaheim, California, Amer. Meteor. Soc., 60-65. Williams, S.F. January 1995: Tactical Data Collection And Management Plan for the 1995 Enhanced Seasonal Observing Period (ESOP-95), University Corporation For Atmospheric Research (UCAR) Office Of Field Project Support (OFPS).