README file for Sagavanirktok River meteorological data Edward J. Kim & Anthony W. England University of Michigan, Ann Arbor 2/29/96 original EK (v0 data) 5/2/97 revised by EK (v0 data) 1/98,11/8/98 revised by EK (v1 data) This file should provide enough basic information for the reader to understand the micro-meteorological data contained in this subdirectory. For more detailed descriptions & explanations of the instrumentation or the field experiment, please refer to University of Michigan Radiation Laboratory Report #RL-918 "Field Data Report for Radiobrightness Energy Balance Experiment-3 (9/94-9/95), Alaskan North Slope, E.J.Kim and A.W.England," or contact the persons listed above. Contact information is provided below. CONDITIONS FOR USE: All ARCSS investigators may freely use these meteorological data. The above-mentioned report would be the source to cite. If you find these data useful, the investigators would also appreciate a short email note. "Patched & interpolated" data (suitable for models requiring fairly uninterrupted input data) incorporate some data from the neighboring Sagavanirktok River LTER site. That site was operated by Gus Shaver & Jim Laundre of the Marine Biological Laboratory (Woods Hole, Massachusetts, USA), and they should also be contacted regarding use of LTER data. ------------------------------------------------------------------------------ LOCATION: all data were collected at a single site, adjacent to the Sagavanirktok River (Slope Mt.) Alaska Dept. of Transportation Maintenance Camp at mile 306 on the Dalton Highway (pipeline Haul Road) or 109 miles from the Deadhorse end of the Highway. This is approximately 20 miles north of Toolik Camp, 30 miles south of Happy Valley, and 6 miles south of Pump Station 3. LATITUDE: 68*45'47" N = 68.76306* N LONGITUDE: 148*52'55" W = 148.88194* W ELEVATION: approximately 500 m, based on USGS topo map SLOPE, ASPECT: very flat DATES: mid-September,1994 to mid-September,1995 (one year). MEASUREMENT INTERVAL: 20 or 30 minutes. See "NOMINAL INTERVALS" section below. SITE DESCRIPTION: The instruments were deployed on a flat moist acidic tussock tundra area adjacent to an abandoned gravel pad west of the pad housing the DOT camp. The support trailer housing the controlling computer was parked at the northwest corner of the abandoned pad. The site was east of the Dalton Highway and north of the access road to the DOT. SOIL: Pergelic Cryaquept (Michaelson, 1996). VEGETATION: sedges, mosses, lichens. NEARBY SITES: The Sagavanirktok River LTER site (Shaver+Laundre, 68*46'N, 148*51'W) was 1.5 km to the east along the Sagavanirktok River. A soil analysis (Ping+Michaelson) was conducted in 1996 for a pit 1.2 km to the east and 0.6 km north (68*46.085'N, 148*51.157'W). A snow analysis (Sturm+Liston) was conducted in 1995. The trench was approximately 100m to the north. A 6 or 8-foot radar retroreflector was located 1.4 km to the southeast (Hinzman, 68*45.305' N, 148*51.329' W). ------------------------------------------------------------------------------ Program: ARCSS/LAII Project Title: Development and validation of a biosphere model for arctic tundra with linkages to satellite radiobrightness. Funding source: NSF grant OPP-9409227 PI: Anthony W. England, england@eecs.umich.edu Investigator: Edward J. Kim, ejk@eecs.umich.edu Affiliation: Dept. of Electrical Engineering & Computer Science and Dept. of Atmospheric, Oceanic, and Space Sciences Address: University of Michigan 1301 Beal Ave. Ann Arbor, MI 48109-2122 U.S.A. Telephone: +1-734-936-1340, +1-734-763-8162 Fax: +1-734-647-2106 WWW site: http://www.eecs.umich.edu/grs/ these data are also avail. at this URL, under "Field Data" and "Rebex-3". PURPOSE: The objective of the project is to develop and validate a land surface process/radiobrightness (LSP/R) model for arctic tundra. Land surface process models provide land-atmosphere boundary conditions for atmospheric circulation models. The accuracy of the LSP parameterizations used in various atmospheric circulation model scenarios is a significant source of uncertainty. By linking the LSP model to satellite observations, the performance of the LSP model over areas such as the North Slope can be monitored more widely and more frequently than is currently feasible. Using satellite observations of radiobrightness, estimates of surface temperature and depth and moisture content of the active layer with a spatial resolution of ~40 km (the resolution of the 37 GHz channel of the Special Sensor Microwave/Imager (SSM/I)) should be possible. The first version of the LSP/R model is being developed for moist acidic tundra - a major landscape unit of the Alaskan arctic (Auerbach, 1995). Model development is supported by data from our one-year field experiment, Radiobrightness Energy Balance Experiment 3 (REBEX-3). ACKNOWLEDGEMENTS: Many persons and organizations contributed suggestions, information, and assistance to make this project successful. We are especially grateful to the Alaska DOT-particularly the two Sagavanirktok River crews, USGS in Fairbanks, Alascom, the Water Research Center at UAF, IAB, PICO/UAF, PICO/UNL, Arctic Wilderness Lodge, and many students at U. Michigan. Funding was provided by NSF, NASA, and USGS. ------------------------------------------------------------------------------ DESCRIPTION OF INSTRUMENTATION: All of the data collected during REBEX-3 were collected using our Tower Mounted Radiometer System 2 (TMRS2), developed at the University of Michigan. TMRS2 is composed of a Radiometer Subsystem, a Micro-Meteorological Subsystem (MMS), and a Control and Data Management Subsystem (CDMS). The components of the MMS and CDMS are listed below. description mfr/model -------------------------------------- ------------------------------ MICRO-METEOROLOGICAL INSTRUMENTS: 10-meter anemometer Met-One 014A 2-meter anemometer & wind vane Davis Instruments 7911 2m Air temperature & Relative humidity Vaisala HMP-35AC Bowen Ratio (intakes at 1 & 2 m) Campbell 023 Downwelling shortwave hemispherical flux Eppley 8-48 (black & white) Upwelling shortwave hemispherical flux Eppley 8-48 (black & white) Net radiometer w/aspirator REBS Q-6 Rain gage Texas Electronics 525 Rain gage wind screen Novalynx Alter-type TDR Soil moisture (10 probes) Campbell(Tektronix) Subsurface temperature (12 probes) Campbell thermistor 107, 107B Snowpack temperature (12 probes) Campbell-equivalent thermistors Snowpack depth graduated rod & video camera Subsurface heat flux (3 disks) Thornthwaite 610 OTHER INSTRUMENTS Video camera Panasonic 1410 CDMS COMPONENTS Data logger & controller (hardware) Apple Macintosh, National Instruments Data logger & controller (software) custom Hypercard program POWER: A 1000-foot arctic-grade 440 volt extension cord to the DOT generators. Maximum power usage: under 7 kW during the winter with all heaters running. Summertime power usage: 3-4 kW. COMMUNICATIONS: System control and data dumps via Alascom radiophone. Link speed: maximum 2400 bps back to Michigan, usually less. ------------------------------------------------------------------------------ TIME SCALE: Listed as 1994 Julian Day for the entire experiment period. So, 1 Jan 94 = Day 1 and 1 Jan 95 = Day 366. The data officially start on day 253 (10 Sep 94) and end on day 624 (16 Sep 95). Three time files are provided: "UTC", "AST", and "LST". UTC = Coordinated Universal Time AST = Alaska Standard Time, the civil time zone for the site. LST = Local Solar Time (the sun crosses the site meridian at exactly 1200). Interrelationships are as follows: AST = UTC - 9 hours = UTC - 0.375 days. LST = UTC - (Longitude in degrees)/360 = UTC - 148.88194/360 = UTC - 0.41356 days. DATA FORMAT: Each variable is saved in a separate ASCII text file. E.g., there are 12 files for the 12 soil temperature probes. File names have the format "nameX.v#", where "name" is the short name of the variable, "X" is an optional single-letter suffix such as "a" or "b", and "v#" indicates the revision number. The data consist of one entry per line. Every file contains 18906 data entries with NO header line. All variables are time-synchronized: the Nth values in all files were recorded simultaneously at the time listed as the Nth value in the "UTC", "AST", or "LST" file. See next section on time scale. The short and full variable names, sensor arrangement, measurement units, and other information for individual sensors are given at the end of this README file. NOMINAL INTERVALS: For the first 1391 data points, the nominal interval was 20 minutes, or 0.0139 days. For the rest of the data points, the nominal interval was 30 minutes, or 0.0208 days. DATA GAPS, NOT-A-NUMBER: Not all instruments were activated for the entire year. For example, the upwelling shortwave hemispherical flux sensor was added in early May, 1995. The rain gage was activated in early May, during snowmelt and before any liquid precipitation for 1995. The TDR & Bowen ratio instruments were also activated beginning in early May. All missing values are listed as "NAN" (not a number) followed by a 3-digit number in parentheses. Obviously out-of-range or erroneous values have been replaced by "NAN". A user can easily replace the "NAN" values with their own missing data flag for compatibility with their programs. The variable called "GAPS" was originally a flag indicating longer-than-usual time intervals between successive original data entries. [*.v0 data:] GAPS(p) = -1 when the time between the (p)th data point and the (p+1)th data point exceeded the value of MAXGAP, otherwise GAPS = 0. For the first 1214 data points, the nominal interval was 20 minutes, and MAXGAP = 0.015 days. For the rest of the data points, the nominal interval was 30 minutes, and MAXGAP = 0.032 days. [*.v1 data:] "GapsA" is a time-regularized version of "gaps". GapsA(p) = -1 for data entries which are not actual measured Rebex 3 values (i.e., NANs from *.v0 data, gaps added & patched or interpolated values in *.v1 data). Note that each data variable was individually cleaned/patched/etc, so variables do not have identical Gap locations. Thus, a single "Gaps" variable cannot identify all gaps in all variables. TIME-REGULARIZATION, PATCHING, AND INTERPOLATION: Beginning with "v1" data, many gaps have been filled in order to provide more continuous data suitable for model input applications. First, the time interval was "regularized" by inserting "blanks". For example, a 2-hour gap which formerly appeared as a 2-hour jump in time between consecutive entries in the data files would, in "*.v1" files, include "NAN" entries spaced 30 minutes apart between the original entries. Files containing 18906 entries have been time-regularized. The filenames also are of the form "nameA.v#" or "nameB.v#". Next, where LTER data were available and appropriate, LTER data were substituted for gaps in Rebex 3 data. Following this "patching," remaining gaps were filled via interpolation. Large gaps or gaps for which insufficient information was available to attempt a reasonable interpolation were left as gaps. The philosophy in these cases was to let the user make their own decisions concerning "estimated data." Patched/interpolated data are in the "nameB.v#" files. "name.v0" data files are not time-regularized, and contain only 15752 data entries. To make it absolutely clear which data points are actual measured Rebex 3 data, and which are patched or interpolated values, the "nameA.v#" files contain un-patched, un-interpolated versions of data. The primary reason for patching/interpolating, was to generate data more suitable for model input. Thus, only quantities which are input variables to our current models have been processed into "nameB.v#" files. ------------------------------------------------------------------------------ DATA NOTES: (1) Net radiation: dome cracked after AST day 587.75 (bad data deleted). Beginning on AST day 499.708 the ventilator was on continuously, and daytime values have been recalibrated (multiplied) by 1.05 to account for ventilator+wind effects. Snow/ice/frost on domes (RsUp and RsDn, too) can corrupt winter data; use with caution. (2) Snow temperature #7: bad channel, no data. Tn data are NOT masked using snow depth data, and Tn probes are NOT accurate Tair sensors, particulary when heated by sunlight. (3) TDR channel #1: connection broke during the winter, no data. Other channels not yet processed. (4) SWalbedo (= RsUpAvg/RsDnAvg) is a calculated quantity. At night, both RsUpAvg & RsDnAvg are near zero & their relative accuracies degrade, leading to unreasonable values of the shortwave albedo (pegged at 0 or 1). (5) Bowen data have not been fully cleaned, especially to eliminate bad data due to water leaking into the plumbing (appearring as high dewpoint values during daytime). Portions are noisy, etc. They are being released "as is" for now. Campbell has since redesigned the seals. Our early model Bowen instrument did not employ aspirated/shielded thermocouples. Arms pointed southeast; U2phi data can be used to mask Bowen data, if desired. (6) U2 wind speed and direction sensor was intended only for coarse measurements, not necessarily accurate enough for wind profile determination. Both the U2 anemometer and direction vane had significant threshholds. (7) RsDnAvg: mfr (Eppley) changed calibration methods between the times this instruments were calibrated (before & after the experiment). RsDnAvg values have been multiplied by 0.9259 to be consistent with the newer calibration method. RsUpAvg was always calibrated w/the newer method. (8) Soil/Snow temps: Tg's reduced by 0.43 C (mean calib. offset of all channels). Tn's reduced by 0.20 C (mean calib. offset of all channels). ------------------------------------------------------------------------------ REVISION PLAN: Data checking and cleaning are continuing. A revision log appears at the end of this document. Send all "bug reports" and suggestions to ejk@eecs.umich.edu. ------------------------------------------------------------------------------ LIST OF VARIABLES: Listed below in alphanumeric order (by short name) are all the variables, units, FORTRAN format specifier, data precision, and sensor arrangement details. All numbers are real numbers except "gaps", and "u2phi" which are integers. All data are single-precision and have been left-justified to eliminate leading blank spaces. Precision is implied by the number of significant figures used, unless otherwise noted. short long units format sensor name name loc'n -------------------------------------------------------------------------- Model Input Parameters: AST Alaska Standard Time 1994JD F7.3 n/a LST Local Solar Time 1994JD F7.3 n/a UTC Coordinated Universal Time 1994JD F7.3 n/a BdelT Bowen ratio temp. difference Kelvin F7.3 lower - upper Bdp1 Bowen ratio upper dewpoint Kelvin F7.3 2m Bdp2 Bowen ratio lower dewpoint Kelvin F7.3 1m Precip liquid precipitation mm F7.3 ~0.5m RH relative humidity % F5.1 2.6m RnAvg net radiation W/m^2 F7.1 1.5m RsDnAvg downwelling SW hemi. Flux W/m^2 F6.1 3.1m RsUpAvg upwelling SW hemi. flux W/m^2 F6.1 1.4m SWalbedo SW albedo 0-1 F5.3 calculated Tair air temperature Kelvin F5.1 2.6m U10Avg 10m wind speed m/s F4.1 10m U2Avg 2m wind speed m/s F4.1 2.3m U2phi 2m wind direction degrees I3 2.3m gaps time gap flag n/a I2 n/a Model Validation Parameters: Hg1 soil heat flux 1 W/m^2 F6.1 -2cm S Hg2 soil heat flux 2 W/m^2 F6.1 -5cm C Hg3 soil heat flux 3 W/m^2 F6.1 -2cm N Tg1 subsurface temperature 1 Kelvin F5.1 -40cm C Tg2 subsurface temperature 2 Kelvin F5.1 -30cm C Tg3 subsurface temperature 3 Kelvin F5.1 -20cm S Tg4 subsurface temperature 4 Kelvin F5.1 -20cm C Tg5 subsurface temperature 5 Kelvin F5.1 -15cm S Tg6 subsurface temperature 6 Kelvin F5.1 -15cm C Tg7 subsurface temperature 7 Kelvin F5.1 -10cm C Tg8 subsurface temperature 8 Kelvin F5.1 -10cm C Tg9 subsurface temperature 9 Kelvin F5.1 -5cm S Tg10 subsurface temperature 10 Kelvin F5.1 -5cm C Tg11 subsurface temperature 11 Kelvin F5.1 -1cm S Tg12 subsurface temperature 12 Kelvin F5.1 -1cm N (see notes below for Tn height references) Tn1 snowpack temperature 1 Kelvin F5.1 40cm Tn2 snowpack temperature 2 Kelvin F5.1 50cm Tn3 snowpack temperature 3 Kelvin F5.1 20cm Tn4 snowpack temperature 4 Kelvin F5.1 30cm Tn5 snowpack temperature 5 Kelvin F5.1 0cm Tn6 snowpack temperature 6 Kelvin F5.1 10cm Tn8 snowpack temperature 8 Kelvin F5.1 10cm Tn9 snowpack temperature 9 Kelvin F5.1 20cm Tn10 snowpack temperature 10 Kelvin F5.1 30cm Tn11 snowpack temperature 11 Kelvin F5.1 40cm Tn12 snowpack temperature 12 Kelvin F5.1 50cm TMRS2 Diagnostic Parameters: Ttrlr CDMS trailer interior temp. Kelvin F5.1 Ttripod MMS box interior temp. Kelvin F5.1 ABBREVIATIONS: SW = shortwave; temp = temperature; 1994JD = 1994 Julian Day; hemi = hemispherical; S/C/N = south/center/north one-third of a tussock. POLARITIES: BdelT>0 when (lower intake temp.) > (upper intake temp.); RnAvg & Hg's are positive into the ground. U2phi=0 when the wind was blowing from geographic north, 90 when the wind was from the east, etc. SENSOR HEIGHT REFERENCES (up is positive): Tg's relative to the top of the "Tg tussock"; Tn1-6 relative to the top of the "Tn tussock"; Tn8-12 relative to the valley bottom between the "Tn tussock" and an adjacent tussock; probes Tn1-6 were 10cm higher than Tn8-12; Hg's relative to the Tg tussock "surface" in the vertical direction; all other sensor heights are relative to the "average" tundra surface height; typical vertical distance between tussock tops and valley bottoms 20-25 cm? with quite a few examples outside that range. ------------------------------------------------------------------------------ DATA ACCURACY: variables accuracy range ----------------------------------------------------------------------------- AST,LST,UTC 1 minute BdelT ** +/- 2 C ## +/- 0.006 C resol Bdp1,Bdp2 +/- 0.5 C 232-314 K dewpnt ## 0.05 C repeatability -30 to +70 C ambient +/- 0.003 C resol 10-90 % equiv. RH@26 C Hg1,Hg2,Hg3 ** +/- 160 W/m2 ## Precip +/- 1.0% 0-5.1 cm/hr (0-50 C) RH +/- 2% (over 0-90%) 0-100% +/- 3% (over 90-100%) -20 to +60 C oper. RnAvg +/- 5% of full scale -340 to +1020 W/m2 RsDnAvg,RsUpAvg** +/- 1.0% linearity 0-1400 W/m2 +/- 1.5% temp depend. (-20 to +40 C) Sdepth +/- 4 cm 0-80 cm SWalbedo (calculated) varies 0-1.0 Tair +/- 0.4 K *** 240-321 K Tg1--Tg12 +/- 0.4 K *** 240-321 K Tn1--Tn12 +/- 0.4 K *** 240-321 K Thous,Tps,Ttrlr,Ttripod +/- 0.4 K *** 240-321 K U10Avg +/- 1.5% or 0.11 m/s 0-45 m/s (-50 to +70 C) 0.447 m/s threshhold U2Avg ** 1.4-52 m/s U2phi **, 10deg* 0-360 deg TDR soil moisture tbd 0-100 % vol. fraction * estimated ## intentionally limited ** no manufacturer's specification given *** worst case: sensor interchangeability + bridge tolerance + polynomial R->T conversion accuracy; majority contribution = +/- 0.2 K interchangeability which is primarily offset, so can be compensated with a single-point calib. ------------------------------------------------------------------------------ REVISION LOG 5/2/97 EK: Minor additions: slope, aspect, soil, vegetation, nearby sites. 9/97 EK: RsDnAvg multiplied by 0.9259 to acct. for mfr's new calib. method. 1/98 EK: Major rev v0 -> v1 data. Added note regarding included LTER data usage. Added info on: time-regularization, patching & interpolation, new variables in "list of variables", data accuracy. Updated: contact info, website URL, new time scale info, filename convention, number of data entries, nominal intervals, gaps, revision plan, sensor height references, data notes. 11/8/98 EK:minor edits. Tg's reduced by 0.43 C (mean calib. offset of all channels). Tn's reduced by 0.20 C (mean calib. offset of all channels).