BOREAS AFM-02 King Air 1994 Aircraft Flux and Moving Window Data Summary: The BOREAS AFM-02 team collected pass-by-pass fluxes (and many other statistics) for a large number of level (constant altitude), straight line passes used in a variety of flight patterns. The data were collected by the University of Wyoming King Air in 1994 BOREAS IFCs 1-3. Most of these data were collected at 60-70 m above ground level, but a significant number of passes were also flown at various levels in the planetary boundary layer, up to about the inversion height. This documentation concerns only the data from the straight and level passes that are presented as original samples and moving window values. Another archive of King Air data is also available, containing data from all the soundings flown by the King Air 1994 IFCs 1-3. Note that although there are less than 100 records in any data file, there are over 170 columns of data. Most spreadsheet software should be able to handle up to 256 columns of data. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification BOREAS AFM-02 King Air 1994 Aircraft Flux and Moving Window Data 1.2 Data Set Introduction The King Air was flown in a variety of flight patterns in BOREAS-94, but predominantly in various sequences of straight, constant-altitude passes for measurement of fluxes and flux profiles in the boundary layer above the BOREAS experiment sites. This document describes the contents of these "flux" archives, which also include statistical summaries of a large number of navigational, dynamic, and thermodynamic parameters. 1.3 Objective/Purpose The Wyoming King Air is one of four flux aircraft flown in BOREAS. The primary objectives of its operation were to measure fluxes of sensible heat, latent heat (moisture), momentum, and carbon dioxide in the boundary layer. In addition, atmospheric dynamic, thermodynamic, and radiation data were collected, along with the standard aircraft parameters of position, altitude, heading, etc. These data will be used for estimates of surface fluxes, boundary layer budgets, error analysis of flux measurements, and will be integrated with smaller and larger scale measurements from the project. 1.4 Summary of Parameters The following is a list of variables for each "flux pass" by the King Air. Section 7 defines the variables and their origins in detail. The moving window data values represent averages over 180-second measurement periods with each period overlapping the period before and the period after by 90 seconds. With the average King Air airspeed being 85-90 m/s, the segments will have an average length of 15.3 to 16.2 km. Note: Those variables flagged (**) were not measured by the King Air. VARIABLES: BOREAS aircraft i.d. Date BOREAS mission designator Mission number of day Pass number Segment number Run start time, GMT Starting latitude Starting longitude Starting BORIS grid E Starting BORIS grid N Run end time, GMT Ending latitude Ending longitude Ending BORIS grid E Ending BORIS grid N Aircraft heading Mean pressure altitude Mean radar altitude Mean wind direction Mean wind speed Air temperature Potential temperature Mixing ratio, H20 U, westerly wind component V, southerly wind component Static pressure Surface radiative temperature ** Downwelling total radiation Upwelling total radiation Downwelling longwave radiation Upwelling longwave radiation Net radiation ** Upwelling PAR ** Downwelling PAR ** Auxiliary radiation sensor ** Greenness index ** CO2 concentration as mole CO2 per mole dry air (also referred to as CO2 molar mixing ratio. If it were given as just CO2 mixing ratio, the units would be mass CO2 per mass dry air). Ozone concentration ** Methane concentration ** Satellite simulator channels 1-4 ** Standard deviations of the following: Air temperature Potential temperature Mixing ratio, H20 U, westerly wind component V, southerly wind component Static pressure Surface radiative temperature ** Downwelling total radiation Upwelling total radiation Downwelling longwave radiation Upwelling longwave radiation Net radiation ** Upwelling PAR ** Downwelling PAR ** Auxiliary radiation sensor ** Greenness index ** CO2 concentration (mole CO2 per mole dry air) Ozone concentration ** Methane concentration ** Satellite simulator, channels 1-4 ** Linear trends of the following: Trend in air temp. Trend in potential temp. Trend in mixing ratio Trend in u Trend in v Trend in static pressure Trend in surface radiation temperature ** Trend in downwelling total radiation ** Trend in upwelling total radiation ** Trend in downwelling longwave radiation ** Trend in upwelling longwave radiation ** Trend in greenness index ** Trend in CO2 concentration Trend in O3 concentration ** Trend in CH4 concentration ** In various categories to follow, the following variables are referred to as the flux variables: Vertical gust, w Westerly wind component, u Southerly wind component, v Along wind component Crosswind component Potential temperature H20 mixing ratio (mass H2O per mass dry air) CO2 mixing ratio (mass CO2 per mass dry air) O3 concentration ** CH4 concentration ** In various categories to follow, these variable pairs are referred to as the flux variable pairs: w, u w, v w, alongwind comp. w, crosswind comp. w, potential temp w, H2O mixing ratio (mass H2O per mass dry air) w, CO2 mixing ratio (mass CO2 per mass dry air) w, O3 concentration ** w, CH4 concentration ** Potential temperature, H2O mixing ratio List of fluxes: Momentum flux, south component Momentum flux, west component Momentum flux along mean wind Momentum flux across Sensible heat flux, H Latent heat flux, LE CO2 flux Ozone flux ** Ozone deposition velocity ** Methane flux ** Standard deviations for the raw flux variables Skewness for the raw flux variables Kurtosis for the raw flux variables Correlation coefficients for the raw flux variable pairs Fluxes using the raw data Constants used in the flux calculations (such as specific heats, latent heat) Standard deviations for the linearly detrended flux variables Skewness for the linearly detrended flux variables Kurtosis for the linearly detrended flux variables Correlation coefficients for the linearly detrended flux variable pairs Fluxes using the linearly detrended data 1.5 Discussion The King Air was flown in all three IFCs in BOREAS-1994. The archived data were collected during straight and level flight lines over the BOREAS Study Areas and on regional runs between Southern Study Area (SSA) and Northern Study Area (NSA). A variety of flight patterns were used, including grids, L- patterns, profiling stacks, and soundings, which are described in more detail in Section 7. Two separate sets of data have been submitted to the BORIS archive: 1-second resolution listings of various variables from the soundings, and fluxes and statistics from the level flux runs. Variables in the latter category include pass-length averages and other statistics, momentum and scalar fluxes, and supporting meteorological, radiometric and aircraft positional data. The high-rate data from which all these variables were computed were not submitted to BORIS. If required, they may be acquired from the University of Wyoming directly. 1.6 Related Data Sets Related data sets include the King Air sounding data for BOREAS-94 and the flux and/or sounding archives from the other three flux aircraft: BOREAS AFM-01 Moving Window Aircraft Flux Data BOREAS AFM-02 Aircraft Sounding Data BOREAS AFM-03 Aircraft Flux and Moving Window Data BOREAS AFM-03 Aircraft Sounding Data BOREAS AFM-04 Aircraft Flux Data BOREAS AFM-04 Aircraft Sounding Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Robert D. Kelly, Associate Professor University of Wyoming Laramie, WY 2.2 Title of Investigation Airborne Investigation of Biosphere-Atmosphere Interactions over the Boreal Forest. 2.3 Contact Information Contact 1 --------- Robert D. Kelly University of Wyoming Laramie, WY (307) 766-4955 (307) 766-2635 (fax) rkelly@grizzly.uwyo.edu Contact 1 --------- Jeffrey Newcomer Raytheon ITSS NASA/GSFC Greenbelt, MD (301)286-7858 (301)286-0239 (fax) Jeffrey.Newcomer@gsfc.nasa.gov 3. Theory of Measurements A series of introductory monographs addressing the theory and practice of measuring atmospheric variables from a moving, aircraft platform may be found in (Lenschow, D. H., ed., 1986: Probing the Atmospheric Boundary Layer, Amer. Meteor. Soc., Boston). An introduction to the general topic of eddy correlation fluxes may be found in (Stull, R. B., 1988: An Introduction to Boundary Layer Meteorology, Kluwer Acad. Pub., Boston). The aircraft uses gust sensors to measure the 3-D air motion relative to the aircraft and a combination of an inertial platform, accelerometers, and (more recently) satellite-based global positioning system (GPS) to measure the motion of the aircraft relative to the earth. These data are combined to determine aircraft position and the earth-relative 3-D winds. Scalar quantities, including static pressure, temperature, water vapor mixing ratio, and CO2 mixing ratio are also measured with fast-response, aircraft-mounted sensors. For each straight, level pass by the aircraft the local means or trends are removed from each of the wind components and the scalar values, leaving the gust components u', v', w', T', r', etc. with which the eddy correlation fluxes are calculated. 4. Equipment: 4.1 Sensor/Instrument Description Table of University of Wyoming King Air Instruments Variable Instrument Accuracy Resolution Hi-rate temperature Rosemount housing with fast-response thermistor (design by Friehe, UCI) 0.50 C 0.01 C Dewpoint temperature Cambridge Model 1373C 1.0 C, >0 C 0.006 C Water vapor mix ratio LICOR 6262 IR spectrometer 1% of reading 0.001 g/kg CO2 mix ratio LICOR 6262 IR spectrometer +/-1ppm at .01 ppm 350 ppm Magnetic heading King KPI553/Sperry C14-43 1 degree 0.02 degree Static pressure Rosemount 1201FA1B1A 0.5 mb 0.06 mb Static pressure Rosemount 1501 0.5 mb 0.003 mb Geometric Altitude Stewart Warner APN159 1% reading 0.24 ft Geometric Altitude King KPA 405 3% <500 ft 6% > 500 ft 0.48 ft Total pressure Rosemount 831CPX 2 mb 0.005 mb Azimuth VOR King KNR615 VOR 1 degree 0.02 degree Distance DME King KNR705A DME 0.2 nautical miles 0.1 nautical mile Latitude/longtitude Tremble 2000 GPS 100 m 0.000172 degree Latitude/longtitude Honeywell Laseref SM 0.8 nm/hr drift 0.000172 degree Ground velocity Honeywell Laseref SM 13.5 ft/s 0.0039 kts Vertical velocity Honeywell Laseref SM 0.5 ft/s 0.03215 ft/min Pitch/roll Honeywell Laseref SM 0.05 degree 0.000172 degree Platform heading Honeywell Laseref SM 0.2 degree 0.000172 degree Flow angle Rosemount 858AJ/831CPX 0.2 degree 0.00375 degree Vertical acceleration Humphrey SA0905021 0.002 g 0.0001 g Rate of climb Rosemount 1241A4BCDE 1%, <15000 ft 2%, >25000 ft 0.004 m/s Engine torque --- 0.2 ft-lbf Liquid Water Content In-house CSIRO hot wire 0.2 g/m3 0.0003 g/m3 Liquid Water Content Bacharach LWH 0.2 g/m3 0.0002 g/m3 Cloud drops PMS FSSP 3 micron 3 micron Radiation: Upwelling Shortwave (0.3-3 microns) Eppley Pyranometer 5 W/m2 1 W/m2 Downwelling Shortwave (0.3-3 microns) Eppley Pyranometer 5 W/m2 1 W/m2 Upwelling IR (4-50 microns) Eppley Pyrgeometer 15 W/m2 1 W/m2 Downwelling IR (4-50 microns) Eppley Pyrgeometer 15 W/m2 1 W/m2 4.1.1 Collection Environment 4.1.2 Source/Platform Platform: Beechcraft Super King Air model 200T, twin-turboprop aircraft 4.1.3 Source/Platform Mission Objectives See section 1.4 4.1.4 Key Variables See sections 1.4, 1.5, 7.3 4.1.5 Principles of Operation See section 3. 4.1.6 Sensor/Instrument Measurement Geometry The gust probe was mounted at end of aircraft nose boom, so that the gust probe tip was about 2 m ahead of the nose of the aircraft. Inertial platform (IRS) and accelerometers were mounted close to the main wing spar (close to aircraft c.g.). Fast-response (Friehe-type) Temperature probe mounted below nose of aircraft, 1.29 m aft from the gust probe tip. Water vapor and CO2 measurements obtained with LICOR 6262 infrared absorption spectrometer. Air drawn from airstream above aircraft cabin into 12.7-mm i.d. tube which faces forward, about 0.3 m above the fuselage skin and 4.06 m aft of the gust probe tip. Airflow in the tube maintained with high-capacity vacuum pump at 60-70 SLPM (about 9 m/s), for Reynolds number about 50,000 (fully developed turbulent flow). At 1.52 m from the inlet, air is drawn from the center of the tube into the LICOR trough a short 6.4-mm i.d. tube, again by vacuum pump, at average flow rate of 6-8 SLPM (also fully turbulent). As verified by flying the aircraft through a power-plant plume, there is a time delay of 0.3 s between the gust probe data and the LICOR data. This delay is removed in the software at the time of data processing. The LICOR 6262 was operated in absolute mode, in which the closed-path absorption in the sample chamber was simultaneously compared to the closed-path absorption in the reference chamber. Air in the reference chamber was circulated continuously through scrubbers that remove both water and CO2, and was circulated at a flow rate of 2 SLPM. Cambridge chilled-mirror dew-point hygrometer mounted inside cabin drew air from vacuum pump driven sample tube. All cloud and precipitation probes (PMS and liquid water content) were mounted near wing tips, both wings. 4.1.7 Manufacturer of Sensor/Instrument See table in section 4.1 4.2 Calibration Instruments subject to calibration as follows: Air temperature: Used manufacturer's one-time calibration for Rosemount model 102, then compared Friehe-type probe against Rosemount. Water vapor concentration: Before each flight, the LICOR H2O channel was calibrated by flushing the chamber with a beam-filling gas of known H2O concentration, generated with a LI-COR Model 610 Dew-Point generator, with accuracy +/-0.03 C. CO2 concentration: Before each flight, the LICOR CO2 channel was calibrated by flushing the chamber with a gas of known CO2 concentration (Source: Scott Specialty, Longmont, Colo., concentration 403.5 ppm, accurate to 4%). Static pressure and gust differential pressures: The gust probe differential pressure sensors (for up-down and left-right angle of flow measurements) and absolute pressure sensor (gust probe total pressure) were calibrated at the beginning of each IFC, using the Rosemount 1501 (accurate to 0.5 mb). 4.2.1 Specifications See table 4.1 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration See section 4.2 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods The straight-line, constant altitude passes used for the flux calculations were all parts of several different flight patterns uses throughout BOREAS-94. What follows here is a brief description of those patterns, including the short, two-letter identifier used for communications, labeling data files, etc. ID Description (second letter denotes NSA or SSA) ----- ---------------------------------------------------- CS Candle Lake runs, SSA only, usually along path a-d. FS,FN Flights of two (intercomparison runs), various locations. GS,GN Grid patterns. Sequence of 9 evenly spaced, parallel flight lines, covering a 32x32 km square area (King Air), with lines oriented either east-west or north-south. HS,HN Stack patterns LS,LN Transects of intermediate length (e.g. 100 km). PS,PN Budget box pattern (see Betts et al., 1990, Boundary Layer Meteorology, 50, 109-137. RT Regional transect. For King Air, route used in transit between NSA and SSA. Coincide with Electra RTs. TS,TN Site-specific run at a TF (tower flux) site. Navigation waypoints used for flying the patterns: Pt. Lat. Long. A 53° 32.0' -106° 34.0' C 53° 37.8' -106° 11.4' (same as PANP-OA) G 53° 55.6' -104° 59.7' H 54° 07.0' -104° 13.5' K 54° 41.7' -103° 47.5' L 54° 57.3' -101° 58.0' M 55° 54.8' -99° 07.5' O 55° 53.2' -98° 00.0' P 60° 30.0' -98° 00.0' Q 60° 30.0' -95° 30.0' R 59° 00.0' -95° 30.0' CH 58° 44.5' -94° 04.0' (Churchill airport) a 53° 34.7' -106° 23.8' b 53° 42.8' -105° 52.0' c 53° 55.0' -105° 04.0' d 53° 59.0' -104° 47.2' f 53° 59.8' -104° 43.5' g 53° 32.0' -104° 27.6' h 53° 56.8' -105° 20.5' i 54° 03.7' -104° 45.5' j 53° 43.8' -104° 34.0' k 53° 35.8' -106° 18.0' m 54° 05.2' -104° 50.5' n 53° 32.2' -104° 19.5' s 53° 17.0' -105° 43.0' t 53° 38.0' -105° 43.0' u 53° 17.0' -105° 32.0' v 53° 43.0' -105° 17.0' Centers of north and south KA grids: North 55° 52.5' -98° 31.5' South 53° 51.5' -104° 48.6' Other locations: NOAA radar 55° 56.0' -98° 36.8' 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The majority of the data were collected over the BOREAS SSA and NSA. The North American Datum 1983 (NAD83) corner coordinates of the SSA are: Latitude Longitude -------- --------- Northwest 54.321° N 106.228 W Northeast 54.225° N 104.237 W Southwest 53.515° N 106.321 W Southeast 53.420° N 104.368 W The NAD83 corner coordinates of the NSA are: Latitude Longitude -------- --------- Northwest 56.249° N 98.825 W Northeast 56.083° N 97.234 W Southwest 55.542° N 99.045 W Southeast 55.379° N 97.489 W The actual spatial coverage of the data values is defined by the flight pattern, leg length, etc. These values are contained in each archived set of numbers for each pass or segment. The moving window data values represent averages over 180-second measurement periods with each period overlapping the period before and the period after by 90 seconds. With the average King Air airspeed being 85-90 m/s, the segments will have an average length of 15.3 to 16.2 km. 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution The fluxes and statistics archived here are for passes or segments of passes between pre-defined waypoints, as part of various flight patterns (see Section 5). The shortest times for such passes/segments are about 2 min, i.e., about 10 km. Thus, the spatial resolution is about 10 km or greater. For the grid patterns (GS, GN) the passes are each 32 km in length. The Candle Lake (CS) runs were divided into two segments, one over the relatively homogeneous Old Aspen area surrounding the OA flux tower (east end of CL run), and the other over the area at the west end of the run dominated by black spruce. Each long leg of the regional transects (RT) was segmented into 180-second segments, each overlapping the adjoining two segments by 50%. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Times of data collection contained in table to follow in this section. Abbreviations used in weather notes in table: cu cumulus st status ci cirrus sct scattered Zi inversion height above ground H haze K smoke cist cirrostratus clr clear ovc overcast RW- light rain showers acu altocumulus Abbreviations in flight descriptions: rt round trip agl above ground level (in feet) msl above mean sea level (in feet) mult multiple TAS true airspeed lvl level wind "L" "L" with one leg parallel to wind direction, flown as at least one round trip. See section 5 for flight pattern descriptions. Summary of UW King Air research flights for BOREAS 1994 Times(UT) Date Start End Hrs Weather Description and comments 940525 1745 2000 2.9 5-10% sct cu CS, 2 rts a-h, 300 agl FS, first a-h with FE 940526 1646 1905 3.0 ci, small % cu GS, full rt, 300 agl 940531 1645 1929 3.6 cu incr 10-40% sharp jump Zi FS, 300 agl with FT PS, using W,E ends FK grid at 200 agl, 2500 and 3400 msl FS, a-d, 300 agl, with FE 940601 630 1802 2.4 H, ci, cist sct cu < 1% LS, j-i-h-i-j, 200 agl CS, one rt d-a-d, 200 agl 940604 1616 1919 3.8 clr then cu incr rapidly, end ovc CS, mult passes 200 agl, 3000 msl FS, d-a, 200 agl, with FL 940606 1546 1809 3.1 cu < 5% LS, mult h-i-j, 200 agl-2900 msl 940607 1447 1649 4.8 clr entire pattern RT, a-h-k-l-m, 200 agl 1649 1904 clr entire pattern GN, full rt, all 300 agl, EW lines 940608 1520 1742 2.9 clr LN, mult t-o at 200 agl, 2100 msl FN, m-o, 300 agl with FT 940610 1642 1901 3.0 sct ci, K all sky GN, full rt, 200 agl, NS lines 940611 1646 1844 2.6 K, cu to 80%, RW- RT, o-m-l-k-h-a, 200 agl 940720 1656 2044 4.4 H, K, cu 10-50% CS, a-d, 300 agl to 4800 msl (co-ord with FE) FS, two a- d, 300 agl with FE 940721 1652 1905 3.0 clr? GS, full rt, 200 agl, NS lines FS, one run SW of grid with FT 940723 1528 1800 3.2 clr, incr to 20% cu CS, mult a-d at 200 agl, 3500 msl 940724 1655 1943 3.4 clr over site GS, full rt, 200 agl, EW lines 940725 1519 1753 3.2 clr CS, mult a-d at 200 agl, 3000 msl 940726 1628 1832 2.7 K, ci RT, a-h-k-l-m-o, 200 agl 940727 1609 1909 4.3 K, altocu, cu GN, full rt 200 agl, NS lines TN (mult) at radar, 500-1000 agl 940728 1620 1810 2.6 K, ci HN(GN) time-centered m-o, 200 agl, 1800 and 2700 msl 940731 1550 1859 3.7 K, clr above GN 940831 1720 1938 2.9 K, cu <1 to 40% GN, full rt, 200 agl, EW lines 940901 1550 1717 1.9 clr above K FN, rt 200 agl, with FT FN, rt 200 agl, diff TAS than FT LN, o-m-o-m-o, 200 agl 940903 1548 1811 3.0 ci, K, cu 0-10% GN, full rt, 200 agl, EW lines 940906 1605 1833 2.9 cu 20-80% GN, full rt, 200 agl, NS lines 940908 1606 1823 2.8 acu, ci, cist, ci ovc RT, o-m-l-k-h-a, 200 agl 940909 1940 2131 2.7 ci, cist thinning CS, mult 200 agl-2600 msl, with FE FS, 300 agl, with FE 940912 1735 2004 3.6 cu incr 0-30% CS, 3 rts, all 200 agl Test = 3 rt over OA area of CS 940913 1645 1905 3.4 clr, then cist and ci GS, full rt, 200 agl, EW lines Test = wind "L" at 8500 msl 940916 1653 1914 4.8 clr GS, full rt, NS lines, 200 agl 1925 2053 clr then <5% cu CS, d-a mult lvls, with FE FS, second a-d with FE, 600 agl 940917 1712 1902 2.4 clr, thin ci to W FS, one end=a, 200 agl, with FT CS, a-d, two rts, 200 agl 7.2.2 Temporal Coverage Map See section 7.2.1 7.2.3 Temporal Resolution See section 7.2.1. Also, each archived data entry contains the start and end times for the pass/segment being summarized. The moving window data values represent averages over 180-second measurement periods with each period overlapping the period before and the period after by 90 seconds. With the average King Air airspeed being 85-90 m/s, the segments will have an average length of 15.3 to 16.2 km. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (faamwdat.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (faamwdat.def). 8. Data Organization 8.1 Data Granularity The King Air data are in two files: one for unaveraged flux pass data and a second for moving window averaged data. 8.2 Data Format(s) The data files contain ASCII numerical and character fields of varying length separated by commas. The character fields are enclosed with single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition file (faamwdat.def). 9. Data Manipulations 9.1 Formulae Constants used in flux calculations: The specific heat of air (Cp) is calculated as a function of the average water vapor mixing ratio, ignoring the pressure-dependent isobaric residual (Smithsonian Meteorological Tables, p. 339). In equation form, Cp=Cp0 + b*rbar, where Cp0=1004.42 J/kgK, b=1845.98, and rbar is the average water vapor mixing ratio, in units of g/g of kg/kg. The latent heat of vaporization, Lv, is calculated as a function of the average temperature, Tbar, as Lv=Lv0 + c*Tbar, where Lv0=3.15209e06 J/kg, and c=-2382.9 for Tbar in degrees Kelvin. These values were obtained by a least-squares fit to values tabulate in the Smithsonian Meteorological Tables, p. 343). Formulas used for the various eddy covariance fluxes. In these expressions, the angle brackets <> denote an average over the length of the time series. Sensible heat flux: Sensible heat flux, H, calculated as H=(density of moist air)*(Specific heat of air at constant pressure)*. Here w is the vertical air motion component (updraft), and theta is the air potential temperature. Resulting units: W m^-2. Latent heat flux: Latent heat flux, E, calculated as E=(density of moist air)*Lv*, where r is the water vapor mixing ratio. Resulting units: W m^-2. Carbon dioxide flux: Carbon dioxide flux, A, calculated as A=(density of dry air)*, where C is the CO2 concentration expressed as mixing ratio (mass CO2 per mass dry air). The units from this calculation would be mass CO2/m^2 s. By BORIS convention, however, the archived units are converted to micromole CO2 m^-2 s^-1. Momentum fluxes: The various vertical fluxes of horizontal momentum are calculated as (density of moist air)*, giving units of kg/ms^2, where vel is u, v, unat, or vnat. Here, (u,v) is the horizontal wind vector in east-west and north-south coordinates, while (unat,vnat) is the vector of along- and cross-wind components of the horizontal wind, with unat parallel to the pass-average wind direction. 9.1.1 Derivation Techniques and Algorithms Not applicable. 9.2 Data Processing Sequence 9.2.1 Processing Steps As listed in Section 7.3, there are two basic categories of numbers (statistics and fluxes) in the archived values for each pass. The first category (groups 3, 4, and 6-10) are statistics and fluxes based on the "raw" data, i.e., on the time series data as they were recorded and processed. The second category (groups 12-16) are "detrended." In these cases the linear trends were removed by calculating an equal-weight least-squares line fit (y=mx+b) for each variable, then subtracting that line from the original series. Group 5 contains the linear trends (the slopes, or m values) from those least-squares fits. The fluxes for the first category ("raw") are based on the covariance values w's', where w'=w-wmean, s=s'-smean, wmean is the simple arithmetic average of w, and smean is the simple arithmetic average of the scalar s. The second category "detrended" fluxes are based on w's' where w'=w-(fitted line for w) and s'=s-(fitted line for s). The moving window data values represent averages over 180-second measurement periods with each period overlapping the period before and the period after by 90 seconds. With the average King Air airspeed being 85-90 m/s, the segments will have an average length of 15.3 to 16.2 km. 9.2.2 Processing Changes None. 9.3 Calculations See 9.1. 9.3.1 Special Corrections/Adjustments Time lag between CO2/H2O measurements and gust probe: Due to the geometry of the instrument locations (See section 4.1.6), there is a significant lag between measurements by the LICOR device (water vapor and carbon dioxide) and the 3-D winds. Based on instrument placement, external airflow velocities, and internal (sampling tubes) flow velocities, the lag was predicted to be 0.3 sec. In contrast, the distance between the gust probe tip and the Friehe temperature probe causes negligible lag between the temperature and wind measurements. Thus, the lag between the temperature and LICOR measurements should be equivalent to that between the wind and LICOR measurements. The predicted temperature-LICOR lag (0.3 sec) was verified by flying the plane several times through the plume from a local power plant, at distances close enough to the source that changes in temperature, water vapor, and CO2 were very abrupt at the plume edges. Thus, prior to any other calculations, the LICOR data are shifted 0.3 sec, to bring those data in sync with the remainder of the data. 9.3.2 Calculated Variables See lists of variables in sections 1.4, 7.1, and 7.3. 9.4 Graphs and Plots Not applicable. 10. Errors 10.1 Sources of Error As with any time-series measurements, there are uncertainties in the values of the resulting measured and derived quantities simply due to the limits of the sampling techniques. Each archived flux and statistic is a single sample, or single realization, of the measurement, and thus has a higher level of uncertainty than if multiple measurements were possible. Sampling limits: As detailed by Lenschow and Stankov (1986, J. Atmos. Sci., 43, 1198-1209), substantial uncertainties are present in single-pass measurements of fluxes. Even to reduce such uncertainties below the 10% range, for example, would require a single aircraft pass to be very long (distance), in fact, so long that other uncertainties would result from 1) having the BL characteristics change with time and 2) having the flight track pass over changing surface characteristics. The most direct technique available with aircraft to address this problem is to make repeated, shorter passes along the same track or at least along similar tracks. The fluxes and statistics from the individual passes may then be combined to at least reduce the standard error of each measurement. This strategy was incorporated into many of the King Air flight patterns. Instrument limits: See 11.2 10.2 Quality Assessment An extensive intercomparison of the BOREAS flux aircraft has been written and submitted for publication in an issue of J. Geophys. Rsch. dedicated to BOREAS analyses (authorship: R. Dobosy, J. I. MacPherson, R. Desjardins, R. D. Kelly, S. Oncley, and D. H. Lenschow). In that text, King Air measurements, including means and variances of all the flux variables, as well as the fluxes themselves, are compared with corresponding values from the Canadian NRC Twin Otter and the NCAR Electra, for multiple wing-to-wing passes at various times during the 1994 experiment. As of this writing, these comparisons are the best available assessments of the overall data quality for the King Air, at least in comparison with similarly instrumented platforms. 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgement None given. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center Data were examined for general consistency and clarity. 11. Notes 11.1 Limitations of the Data For each pass or segment of a pass, the statistics and fluxes are archived for time series with simple arithmetic means removed and then again for time series with simple linear trends removed. The first set ("demeaned") thus represents the original, raw data with no filtering applied. The second set (detrended) also represents unfiltered data, having only the linear trends removed. In order to apply more complicated, non-linear detrending or filtering methods, the original data must be obtained. 11.2 Known Problems with the Data Vertical velocity measurements: Spectral density plots of vertical velocity (w) generally show a fairly well defined inertial subrange, with -5/3 slope out to about 9 Hz, at which point the effects of the anti-aliasing low-pass filter are evident. Many of the w spectral plots do, however, show a slight "bulge" above the -5/3 line in the range 0.1-1 Hz. As of this writing (July 9, 1996) we believe this is an artifact of the post-flight calculations. Examples of these spectra can be seen in the JGR manuscript comparing the four BOREAS flux aircraft (Dobosy et al., 1996, JGR dedicated issue). High-rate H2O measurements (LICOR 6262): The LICOR 6262 response is described by the manufacturer as being a 90% response to step-function changes in concentration in 0.1 s. The combination of this characteristic, any along-flow mixing in the sample tubes, and the anti-aliasing filter are evident in the spectral density plots for H2O mixing ratio. These plots generally show an inertial subrange (slope -5/3) out to about 2 Hz, at which point the response drops sharply. At 2 Hz, the SNR is usually about 20 dB. Implications of this response for the flux calculations are that the H2O fluxes are being resolved only to about 2 Hz (about 40 m for typical research airspeeds). CO2 measurements (LICOR 6262): The response characteristics for CO2 are generally the same as for H2O, except that the SNR at 2 Hz is usually 10 dB or less. As with CO2, these figures imply that the CO2 fluxes are being resolved only to about 2 Hz (about 40 m for typical research airspeeds). 11.3 Usage Guidance Note that although there are less than 100 records in any data file, there are over 170 columns of data. Most spreadsheet software should be able to handle up to 256 columns of data. 11.4 Other Relevant Information None given. 12. Application of the Data Set These data can be used to obtain study area and regional scale estimates of the various fluxes. 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description Not applicable. 14.2 Software Access Not applicable. 15. Data Access 15.1 Contact for Data Center/Data Access Information These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 15.2 Procedures for Obtaining Data BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www-eosdis.ornl.gov/ or users may place requests for data by telephone, electronic mail, or fax. 15.3 Output Products and Availability Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes. The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also available. 16. Output Products and Availability 16.1 Tape Products Not applicable. 16.2 Film Products Not applicable. 16.3 Other Products Comma-delimited ASCII text files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation See refs listed in section 17.2 17.2 Journal Articles and Study Reports Baijards, S.A.M., S. O. Ogunjemiyo, R. D. Kelly, and P. H. Schuepp. 1996: Preliminary analysis of dual aircraft boundary layer grid flux. Submitted to J. Geophys. Rsch. Baijards, S. A. M. and R. D. Kelly 1996. Conditional sampling applied to BOREAS aircraft data., Preprints, 22nd Conf. on Agric. and Forest Meteor., 28 Jan. - 2 Feb. 1996, Atlanta, GA. Betts, A. K., R. L. Desjardins, and J. I. MacPherson 1989: Boundary layer heat and moisture budgets. Spring 1989 meeting of Amer. Geophys. Union, May 7-11, 1989, Baltimore. Betts, A. K., R. L. Desjardins, and J. I. MacPherson. 1990. Boundary layer heat and moisture budgets from FIFE. AMS Symposium on First ISLSCP Field Experiment (FIFE), 70th AMS Annual Meeting, Feb. 5-9, 1990, Anaheim, CA. Dobosy, R.J., T. L. Crawford, J. I. MacPherson, R. L. Desjardins, R. D. Kelly, S.P. Oncley, and D. H. Lenschow. 1994. Intercomparison among the four flux aircraft at BOREAS. Submitted to J. Geophys. Rsch. Kelly, R. D., J. I. MacPherson, R. J. Dobosy, and T. L. Crawford 1996. BOREAS 1994 intercomparison among three flux aircraft., Preprints, 22nd Conf. On Agric. and Forest Meteor., 28 Jan. - 2 Feb. 1996, Atlanta, GA. McDermott, M.L. and R. D. Kelly. 1996. Variation of boundary layer fluxes with heterogeneous surface vegetation and seasonal change. Submitted to J. Geophys. Rsch. McDermott, M. L. and R. D. Kelly 1995. Fluxes over a heterogeneous forest., Preprints 11th Symposium on Bound. Layers and Turbulence, Charlotte, NC, 27-31 March, 1995. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. 1997. BOREAS in 1997: Experiment Overview, Scientific Results and Future Directions. Journal of Geophysical Research 102 (D24): 28,731-28,770. 17.3 Archive/DBMS Usage Documentation None given. 18. Glossary of Terms and abbreviations Abbreviations used in weather notes: cu cumulus st status ci cirrus sct scattered Zi inversion height above ground H haze K smoke cist cirrostratus clr clear ovc overcast RW- light rain showers acu altocumulus Abbreviations in flight descriptions: rt round trip agl above ground level (in feet) msl above mean sea level (in feet) mult multiple TAS true airspeed lvl level wind "L" "L" with one leg parallel to wind direction, flown as at least one round trip. 19. List of Acronyms BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center NASA - National Aeronautics and Space Administration ORNL - Oak Ridge National Laboratory URL - Uniform Resource Locator NCAR - National Center for Atmospheric Research NRC - National Research Council, Canada BL - atmospheric Boundary Layer 20. Document Information 20.1 Document Revision Date Written: 16-JUL-1996 Last Updated: 11-Feb-1999 20.2 Document Review Date(s) BORIS Review: 08-Feb-1999 Science Review: 20.3 Document ID 20.4 Citation 20.5 Document Curator 20.6 Document URL AFM02_AC_Flux.doc 03/03/99