Atmospheric Surface Flux Group Data from "Met City". Until the final data set is submitted to JOSS in the fall, these files can be requested from any of the 4 Co-PIs (Ed Andreas, Chris Fairalll, Ola Persson, Peter Guest). Please include a detailed specification of the intended use of the data. Processed data from flux group tower will be given in 4 space-delimited ASCII files. Two files contain hourly values and two files contain daily averages. These files are still preliminary and the formats and precise parameters in the final files to be submitted in the fall may differ. Our current version (ASFG1.0 – completed in March 1999) is cleaner than previous ones and include original relative humidity, pre and post radiometer calibrations, and more accurate calculation of mixing ratio (there was a formula error before and a constant atmospheric pressure had been assumed). Fluxes are calculated using the observed surface pressure (at Florida) rather than an assumed constant one. Wind direction is now true wind direction accounting for the rotation of the tower during the year. Also, editing was done at a much earlier stage of the analysis on 10- minute segments, thereby permitting hourly average values to be considered good when previously an hour was flagged as bad when only a few minutes of bad data may have existed during that hour. This earlier editing has also prevented fewer "bad" hourly average points from getting through (e.g., when the data acquisition was shut down for 10 minutes, a 10-minute value of 0 was averaged into the rest of the hour. For some parameters, e.g., temperature, this bad average was not always detected before). 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 not as yet include intercomparison calibrations done during the year. There are other details that make these files slightly different than previous ones we have released, and I am in the process of documenting these details. One file (prof_file_all2_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_file2_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. 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_all2_ed_hd.txt, the column headers are: JD Press z1 z2 z3 z4 z5 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 T_s_epp T_s_brns Tsnw Tice 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 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 mb 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 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 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_file2_hd.txt, the column headings are: JD Press ws2.5 ws10 wd2.5 wd10 T2.5 T10 q2.5 q10 rhi2.5 rhi10 T_GE T_s_epp T_s_brns Tice LWd Lwu SWd Swu RR_org RR_ncr twr_orien ww u* hs hl usb hsb hlb with the respective units: UTC 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 W/m^2 W/m^2 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. 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 not yet available. 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=3e-4 m. It is planned that some data files with higher temporal resolution will also be available when all the work is done. This will likely include files of covariance spectra for each hour and level. We are currently working on a detailed description of the processing that was done for each parameter. In the meantime, let us know if you have any questions, and especially let us know if you find anything odd or an obvious error. Ola Persson