*** PLEASE READ *** *** IMPORTANT NOTES CONCERNING ALL RADIOSONDE DATA *** I. Introduction This file, README.1ST, contains notes that pertain to all sounding data. Any information specific to particular sites is contained in the six other "README" files. Those files are labeled with a three-letter suffix that identifies the site. The suffixes are basically the first three letters of the site names: LES for LE Suroit (I left the "Le" in the name for coding reasons), MAL for MALcolm Baldrige, OCE for the OCEanus, POR for PORto Santo, SAN for SANta Maria and VAL for the VALdivia. Summary tables containing file names, launch times, termination of launch times, the approximate maximum height and minimum pressure of the sounding, the latitude and longitude at the start of launch (for ships only) and important comments concerning each launch are labeled with the prefix "SUMMARY." and the same site-specific suffixes as for the "README" files. It is strongly recommended that all explanatory information be read before using this data!!! If any user has questions about anything concerning the radiosonde data set, please feel free to contact me... Bill Syrett 408 Walker Building Department of Meteorology The Pennsylvania State University University Park, PA 16802 USA Phone: (814) 863-3094 FAX: (814) 865-3663 E-mail: syrett@psumeteo.psu.edu syrett@fire.essc.psu.edu I am sure there will be comments and questions, don't be shy. These notes are not meant to answer every possible question, just the most likely ones. II. Data File Names There are 3 sets of interpolated sounding data for each site. They are 5-second, 20-meter and 2-millibar. The file names are thus coded with either a "T", a "Z" or a "P" representing time, height and pressure interpolation, respectively. Also coded into the file name is the site identifier. These six identifiers are: L for Le Suroit, M for Malcolm Baldrige, O for Oceanus, P for Porto Santo, S for Santa Maria and V for Valdivia. The month is coded either MY for May or JN for June and, finally, the suffix is XXZ, where XX represents the official data time and is either 00, 03, 06, 09, 12, 15, 18, or 21 UTC. See the summary tables for start and end times for each sounding. Thus, SJN0492T.18Z is 5-second data from Santa Maria from 4 June 1992. From the summary table for Santa Maria (SUMMARY.SAN) one finds that launch time was 1635 UTC, the sounding terminated at 1755 UTC and reached about 14 km or 144 mb. The comments section indicates that temperatures were extrapolated below 514 m, which is explained in the file README.SAN. III. File Format Each file contains a 5-line header. The first line is the site name (up to 16 characters), the next line is the latitude and longitude at the time of launch, the third contains the date-time group at launch in YYMMDDHHMM format. Lines 4 and 5 describe the data to follow, which comprises no more than 1500 additional lines. The data are: minutes, seconds past launch, ascent rate, height, pressure, temp- erature, relative humidity, dewpoint, mixing ratio and wind speed and direction. The format is (i3,1x,i2,3x,f4.1,4x,i5,3x,f6.1,3(2x,f5.1),2x,f6.3,2x,i3,1x,f5.1). Missing data is flagged with the following values: RH, TD and wind speed equal -99.9, W equals -9.999 and wind direction is -99. Relative humidity only rarely dropped out, the winds frequently dropped out at upper levels. IV. The Data The measured parameters were pressure, temperature and relative humidity, with winds calculated using the Omega network, except at Porto Santo. A detailed exp- lanation of the calculation of Porto Santo winds can be found in "Analysis of Sounding Data From Porto Santo Island During ASTEX" by Schubert et al. The "Omega" winds actually were averaged over a one- to four-minute period by the software used at launch time. Sounding data from each site were output at various temporal intervals, ranging from 1.5 seconds at Porto Santo to about 30 seconds for upper-level Valdivia data. These "raw" data were cleaned up and then interpolated to 5-second intervals. Derived quantities include height, dewpoint and mixing ratio. The ascent rate is included, but due to occasional problems with the elapsed time in the raw data, it should only be treated as a rough approximation and definitely not used to infer vertical velocities. The formulas and procedures used for mixing ratio, dewpoint and height are (in FORTRAN format): Mixing Ratio (w): w = 622.0*(e/(p-e)) p = pressure (mb) e = vapor pressure (mb) where: e = RH*es/100.0 RH= relative humidity es= sat. vapor pres. (mb) where: es= 6.112*EXP((17.67*T)/(T+243.5)) T = temperature (deg C) Height (z): z(i) = z(i-1)+(R*TvA/g)*LN(p(i-1)/p(i)) R = gas constant (J/kg K) g = acc. due to gravity where: TvA is the layer-averaged virtual temp; Tv = T*(1.0+0.61*w) ; w in g/g, Tv in degrees Kelvin for height computation. Dewpoint: Td = (243.5*LN(e/6.112))/(17.67-LN(e/6.112)) Please note that the relative humidities from Le Suroit, Santa Maria, the Oceanus and the Malcolm Baldrige were adjusted upward based on observations and a conversation with a Vaisala employee familiar with the humidity sensor on the RS-80 sondes used at these sites. The adjustment procedure is described in the file REDAME.SAN. Relative humidities from the Valdivia occasionally went above 100 percent (a maximum of 105 percent) and were set to 100 percent in these cases. It appears that a slightly larger adjustment (1 to 4 percent additional) would be ideal, but more study needs to be done on this. There was no adjustment of the Porto Santo relative humidities. Obvious, singular bad data (spikes in humidity and temperature) were removed when discovered, and winds were occasionally adjusted when obviously bad (refer to the summary tables- adjusted only when bad data were infrequent and not deep). Super- adiabatic lapse rates found at the base of the inversion were not removed, so watch for these as they are ficticious (caused by evaporational cooling). They do not occur very often. The general data quality was quite good. Temperature data were consistently of high quality with the exception of the false super-adiabatic layers. Humidity data were of good quality, although apparently a few percent low when the air was moist. Porto Santo humidities were consistently higher at levels above 9 km than those from all other sites, but the importance of this observation seems minimal. Winds were subject to noise and were fairly frequently of less-than-good quality. Obvious bad data were adjusted, removed or simply mentioned in the summary tables- please be sure to refer to these tables before using the wind data.