Atmospheric Surface Flux Group Data from "Met City". Processed data from flux group tower is given in 4 tab-delimited ASCII files. The site, instrument, and data processing descriptions can be found in Andreas et al (1999) and Persson et al (2001). Andreas, E.L., C. W. Fairall, P. S. Guest, and P. O. G. Persson, 1999: An overview of the SHEBA atmospheric flux program. Preprints, Fifth Conf. on Polar Meteor. And Ocean., Jan. 10-15, 1999, Dallas, TX, 550-555. Persson, P. Ola G., C. W. Fairall, E. Andreas, P. Guest and D. Perovich, 2001: Measurements near the Atmospheric Surface Flux Group tower at SHEBA Part I: Site description, data processing, and accuracy estimates. J. Geophys. Res. Submitted. Other ASFG SHEBA publications describe additional details of specific instruments. A list of these publications can be found on the ASFG website http://www.weather.nps.navy.mil/~psguest/sheba/ Two files contain hourly values and two files contain daily averages. Our current version is ASFG3.0 and was completed in January 2001. Fluxes are calculated using the observed surface pressure (at Florida) rather than an assumed constant one. Wind direction is true wind direction accounting for the rotation of the tower during the year. Both objective and some subjective editing has been done at various stages of the data processing. Hourly averages were calculated as long as at least 4 10-minute periods during the hour contained 2 or more minutes of good data. Fluxes are also eliminated when the airflow was from the ship or through the tower. The data does include intercomparison calibrations done during the year and has been corrected based on the intercomparisons and methods described in http://www.weather.nps.navy.mil/~psguest/sheba/tower_cal/ and Persson et al 2001. One file (prof_file_all6_ed_hd.txt) contains data from all 5 levels on the tower as well as the radiometer and surface measurements (include the Barnes, GE and the two thermistors). The tower data includes sensible heat and momentum fluxes as well as the RH, wind speed, temperature data. This file also includes variances, structure functions, etc for each level. The other file (main_file6_hd.txt) is derived from the first file by taking the median fluxes and interpolating the temperature, humidity and wind to 2.5 and 10-m. This file does not contain any of the variances, etc, but does contain bulk estimates of latent and sensible heat fluxes at 2.5 and 10 m. Each file has a header that explains each column of data. There are headers in each of the files which will give you an idea of what each column is. I will list them below so you might have an idea which file you want. For file prof_file_all6_ed_hd.txt, the column headers are: JD lat lon Press z1 z2 z3 z4 z5 zoph ws1 ws2 ws3 ws4 ws5 wd1 wd2 wd3 wd4 wd5 T1 T2 T3 T4 T5 q1 q2 q3 q4 q5 rh1 rh2 rh3 rh4 rh5 rhi1 rhi2 rhi3 rhi4 rhi5 T_GE Td_GE T_s_epp T_s_brns Tsnw Tice Tsfc LWd Lwu SWd Swu RR_org RR_ncr twr_orien u*1 u*2 u*3 u*4 u*5 hs1 hs2 hs3 hs4 hs5 hl ww1 ww2 ww3 ww4 ww5 sgu1 sgu2 sgu3 sgu4 sgu5 sgv1 sgv2 sgv3 sgv4 sgv5 sgw1 sgw2 sgw3 sgw4 sgw5 sgT1 sgT2 sgT3 sgT4 sgT5 cu21 cu22 cu23 cu24 cu25 cv21 cv22 cv23 cv24 cv25 cw21 cw22 cw23 cw24 cw25 cT21 cT22 cT23 cT24 cT25 No1 No2 No3 No4 No5 fl1 fl2 fl3 fl4 fl5 with respective units: UTC deg deg mb m m m m m m m/s m/s m/s m/s m/s deg true deg true deg true deg true deg true deg C deg C deg C deg C deg C g/kg g/kg g/kg g/kg g/kg % % % % % % % % % % deg C deg C deg C deg C deg C deg C deg C W/m^2 W/m^2 W/m^2 W/m^2 mm/h mm/h deg true m/s m/s m/s m/s m/s W/m^2 W/m^2 W/m^2 W/m^2 W/m^2 W/m^2 m/s m/s m/s m/s m/s m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 m/s^2 deg C^2 deg C^2 deg C^2 deg C^2 deg C^2 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 x^2/m^2/3 For main_file6_hd.txt, the column headings are: JJD lat lon Press ws2.5 ws10 wd2.5 wd10 T2.5 T10 q2.5 q10 rhi2.5 rhi10 T_sfc T_s_epp T_s_brns Tice LWd Lwu SWd Swu RR_org RR_ncr twr_orien ww u* hs hl usb_2.5 usb_10 hsb_2.5 hsb_10 hlb_2.5 hlb_10 with the respective units: UTC deg deg mb m/s m/s deg true deg true deg C deg C g/kg g/kg % % deg C deg C deg C deg C W/m^2 W/m^2 W/m^2 W/m^2 mm/h mm/h deg true m/s m/s W/m^2 W/m^2 m/s m/s W/m^2 W/m^2 W/m^2 W/m^2 The Julian Day is based on Jan. 1, 1997 being Julian Day 1, so Jan. 1, 1998 is Julian Day 366. The daily files contain similar parameters, and are called prof_file_davg_all6_ed_hd.txt and main_file_davg6_hd.txt. Daily means were only calculated if at least 20 hours of data was available. The columns "No#" and "fl#" in prof_file_all6_ed_hd.txt indicate the number of points used in the turbulence FFTs and a flag indicating whether the turbulence data passed (=0) or failed(=1) various quality control checks, respectively. If fl=1, the wind data might be suspect, as it is also determined from the sonic anemometers. Note that rhi is relative humidity with respect to ice recalculated from the original measurement of relative humidity with respect to water. twr_orien is the orientation of the tower sonic boom arms, which was used to calculate the true wind direction wd. Three surface temperature measurements are available from the General Eastern, the Eppley radiometer and the Barnes radiometer. The Eppley is the most reliable, though there are periods when the other two are also reasonable, and one period (May) when the Eppley data may be slightly off. Tsfc is our best estimate of the surface temperature, and is principally based on slight corrections to the Eppley temperatures and the Barnes temperatures when the Eppley was known to be wrong. Check with one of the PIs on the latest status of the estimated errors. The measurements of stress and sensible heat flux are the median values of the levels with "good" measurements. Eddy correlation measurements of the latent heat flux from the Ophir instruments are included, but are quite low with respect to bulk estimates so should be used with caution. The bulk estimates of stress, sensible and latent heat flux are calculated using a modified COARE flux algorithm that computes fluxes over the ocean or sea ice. For ice it uses Andreas 1987 for Ch and Ce; presently it sets zo=4.5e-4 m. Other data files are also available from the four PIs. These data files include similar data as above but with higher temporal resolution, files of covariance and quadrature spectra for each hour and level, and sodar data. This data is currently at various stages of development. Two manuscripts describing this dataset and the near-surface conditions determined from this data set have been submitted for publication and can be requested from Ola Persson (ola.persson@noaa.gov). Please let us know if you have any questions, and especially let us know if you find anything odd or an obvious error. Ola Persson