Date: Wed, 25 May 2011 15:13:56 MDT To: russell.monson@Colorado.EDU, laura.scott@Colorado.EDU, nicole.trahan@Colorado.EDU, amy.m.watson@Colorado.EDU, lynette.laffea@Colorado.EDU, lindsay.young@Colorado.EDU, allyson.eller@Colorado.EDU, sean.burns@Colorado.EDU From: Sean Burns Subject: Re: Release of Updated CU AmeriFlux Data... Hi All, fyi---Dave Moore noticed a mistake in the flag file for the ustar-filtered co2 flux (ie, Fco2_21m_nee_wust) in the data files released on 4/20/2011. These are the flags in column 8 (i.e., "C02 NEE Flux Flag") of the flux flag data file (ie, flux_flags_YYYY_ver.2011.04.20.dat).... the problem: the Fco2_21m_nee flag is sometimes set to "1", "2", or "3" when the Fco2_21m_nee_wust data have been ustar-filtered and filled with an empirical relationship between Tsoil and Fco2_21m_nee...since this problem can be fixed using the existing data (see below), my plan is to fix the problem for the next data release early next year....in the meantime, here is a short description of how to fix this problem yourself...I'm showing this example with matlab using the 2005 data: % find the pts that are ustar-filtered.... load flux_2005_ver.2011.04.20.dat load climate_2005_ver.2011.04.20.dat load flux_flags_2005_ver.2011.04.20.dat climate=climate_2005_ver_2011_04_20; flux= flux_2005_ver_2011_04_20; flux_flag= flux_flags_2005_ver_2011_04_20; nee_raw=flux(:,8); % NEE without ustar-filter nee_ustar=flux(:,9); % NEE with ustar-filter r=find(abs(nee_raw-nee_ustar) > 0); % find the points where nee_raw and nee_ustar differ % note that most of these pts have an NEE flag= "1"...they should NOT be "1". % I'm going to use a unique flag ID of "7" to indicate these data are % ustar-filtered...here is how to fix the flags: nee_flag= flux_flag(:,8); plot(nee_flag(r),'.') nee_flag(r)=7; % set NEE flag to "7" for ustar-filtered NEE data. flux_flag(r,8)=7; % also do in the flag matrix... % now if you plot the ustar-filtered data you % will see the ustar-filtered fit/correction, ie: Tsoil=climate(:,19); plot(Tsoil(r),nee_ustar(r),'.') % note, summer and winter data use a slightly % different relationship.... sorry for this inconvenience and if you have any further questions or notice any other problems please let me know... cheers, SpB. % --------------------------------- Original email: > > Hi All, > > We have updated the climate and flux datafiles collected from the > Niwot Ridge Subalpine Forest AmeriFlux tower (for the years > 1998-2010)...as many of you know, last year we found a bug in the code > that calculated the co2 fluxes (both a dilution and WPL correction > were used)....the co2 flux data in this release have been corrected > for this bug as well as several other items (see list below). After > correcting the co2 fluxes, the annual NEE uptake by the forest > approximately doubles....here is an example: > > http://urquell.colorado.edu/sean/plots_interyearly/plots_fluxes/p_Fco2_2001.png > > The new data are available at: > > http://urquell.colorado.edu/data_ameriflux/data_30min/ > > and all the files can be downloaded from a single zip file at: > > http://urquell.colorado.edu/data_ameriflux/data_30min/ameriflux_data_ver.2011.04.20.zip > > I'll list all the new data files below as well as information from > a data file header which details all the changes made with > this new data release... > > if anyone has any questions or notices any problems with these data > files please let me know (or if you want to be removed from these > email updates let me know that too). > > Tom and Bai, please use these files to update the data in your > archive... > > thanks! > > SpB. > > ------------------------------------------------------------------------------ > Sean Burns > Department of Ecology and Evolutionary Biology (EEB) > Campus Box 334 > University of Colorado > Boulder, CO 80309-0334 > > for FEDex: Ramaley Building, Room N122 > > Internet: sean.burns@colorado.edu > http://www.mmm.ucar.edu/people/burns/ > Phone: (303) 492-5796 Fax: (303) 492-8699 > ------------------------------------------------------------------------------ > > > Header Info: > > % > % Current Data Version: ver.2011.04.16 > % > % Updates and Changes from ver 3.0 (11 Aug 2009) to ver.2011.04.16: > % > % * Heat, water vapor, and co2 fluxes are recalculated from the hi-rate > % data. NOTE: a bug was found in the software that calculated the > % previous version of the co2 fluxes (the co2 flux was "double- > % corrected" for the effect of water vapor, i.e., both a dilution and > % WPL correction were applied). With the new co2 fluxes, the forest is > % about twice as large a co2 sink (over a year) as previously thought. > % > % * closed-path co2 and water vapor fluxes are now calculated using a > % lag-time that varies with time. Also, the lag for h2o is now about > % 0.4 sec longer than the one used for co2. > % > % * a krypton hygrometer is used as the primary latent heat flux (Qe) > % instrument; however when the krypton data are missing, an "enhanced" > % Qe from the closed-path LI-6262 are used. The enhancement factor > % takes into account Qe information lost in the tubing. > % > % * for periods in 2008-2010 the sensible heat flux (Qh) is calculated > % from a thermocouple near the csat rather than using the csat/sonic > % temperature (this is because there was a problem with the csat). > % > % * decreased the measured barometric pressure by 0.76 kPa (based on > % comparisons with other pressure sensors). Correction is: > % > % P_baro = P_baro_raw + P_corr, where P_corr=-0.76 kPa > % > % * z/L has been recalculated using the appropriate form of Qh > % > % * the sign of the momentum flux has been corrected so that: > % flux_mom=-1.*rho.*u_w_21m. > % > % * a consistent empirical gap-filling technique has been applied to flux > % data from all years > % > % * the planar-fit has now been applied to the early years. Also, planar > % fit coefficients are allowed to vary/change with time (i.e., to take > % into account when the sonic has been moved and re-deployed) > % > % * Wind Direction (wd_21m) has been recalculated for all years. > % > % * Scalar wind speed (ws_21m) is used for all years (previously 1998 > % and most of 1999 used the vector wind speed). > % > % * VPD is now calculated using the 8m T/RH rather than the 21.5m T/RH. > % (this is supposed to simulate the VPD within the needles, so it is > % more appropriate to use the T/RH that is near the canopy) > % > % * Percent Absorbed PPFD is no longer part of the climate data files, > % this has been replaced by the outgoing PPFD data, Rppfd_out_25m > % > % * A flag for Rppfd_out_25m has been added: > % > % 23. Rppfd_out_2 Outgoing PPFD Flag > % > % while the two flags: > % > % 23. Rppfd_in_mo PPFD Model fit from Rnet Flag > % 24. Rppfd_abs_2 Percent Absorbed PPFD Flag > % > % have been removed (see the header of the climate flag data file for > % more details) > % > % * A consistent flag-nomenclature is now used for all flag variables > % (the exceptions are: Qe_21m_flag, Energy Balance, Stationarity, > % and the Inegral Stats flags---see header of flux flag file for > % more details as well as the flag nomenclature details) > % > % > % Updates and Changes from Version 2.1 to 3.0 (11 Aug 2009): > % * checked for any RH values over 100 > % recalculated VPD with the new RH values. > % * checked that nighttime PAR > 0 > % * re-did the ustar filter for Fco2_21m_nee_wust. see info at: > % http://urquell.colorado.edu/data_ameriflux/docs/ustar.txt > % * to remove spikes in flux data, applied a very light 5-point median > % filter to Fco2_21m_nee_*, Qe_21m, Qh_21m > % > % Updates and Changes from Version 2.0 to 2.1 (11 Mar 2008): > % * changed the time stamp to the CENTER of the averaging period > % (previously the time stamp was at the START of the 30-min time > % period) > % > % Updates and Changes from Version 1.1 to 2.0 (4 May 2005): > % * replaced 960 missing Tsoil data with "optimized-fit" data > % (provided by Bill Sacks) > % * replaced bad value for s_P_bar_12m at day = 314.3229 > % > % Updates and Changes from Version 1.0 to 1.1 (20 Jul 2004): > % * recalculate vpd > % * use local standard time (MST) for the time stamp > % (previous data versions used a combination of MST and MDT) > % * add decimal day of year (column 7) > % > % NOTES: > % > > > File Listing: > > -rw-r--r-- 1 sburns aster 938469 Apr 20 09:38 climate_1998_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5550426 Apr 20 09:39 climate_1999_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5564340 Apr 20 09:41 climate_2000_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549409 Apr 20 09:43 climate_2001_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549326 Apr 20 09:45 climate_2002_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549167 Apr 20 09:47 climate_2003_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5564483 Apr 20 09:50 climate_2004_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549790 Apr 20 09:52 climate_2005_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5550973 Apr 20 09:54 climate_2006_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5550422 Apr 20 09:56 climate_2007_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5565631 Apr 20 09:58 climate_2008_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549672 Apr 20 10:00 climate_2009_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 5549669 Apr 20 10:02 climate_2010_ver.2011.04.20.dat > > -rw-r--r-- 1 sburns aster 496958 Apr 20 09:38 flux_1998_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2920102 Apr 20 09:40 flux_1999_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2926813 Apr 20 09:42 flux_2000_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2919081 Apr 20 09:44 flux_2001_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2919000 Apr 20 09:46 flux_2002_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2918845 Apr 20 09:48 flux_2003_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2926975 Apr 20 09:51 flux_2004_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2919471 Apr 20 09:53 flux_2005_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2920658 Apr 20 09:55 flux_2006_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2920105 Apr 20 09:57 flux_2007_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2928108 Apr 20 09:59 flux_2008_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2919350 Apr 20 10:01 flux_2009_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2919345 Apr 20 10:03 flux_2010_ver.2011.04.20.dat > > -rw-r--r-- 1 sburns aster 468431 Apr 20 09:38 climate_flags_1998_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2745668 Apr 20 09:40 climate_flags_1999_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2751896 Apr 20 09:42 climate_flags_2000_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2744645 Apr 20 09:44 climate_flags_2001_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2744566 Apr 20 09:46 climate_flags_2002_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2744408 Apr 20 09:48 climate_flags_2003_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2752054 Apr 20 09:50 climate_flags_2004_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2745039 Apr 20 09:52 climate_flags_2005_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2746225 Apr 20 09:54 climate_flags_2006_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2745671 Apr 20 09:56 climate_flags_2007_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2753195 Apr 20 09:58 climate_flags_2008_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2744917 Apr 20 10:00 climate_flags_2009_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 2744918 Apr 20 10:02 climate_flags_2010_ver.2011.04.20.dat > > -rw-r--r-- 1 sburns aster 321180 Apr 20 09:38 flux_flags_1998_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1868803 Apr 20 09:41 flux_flags_1999_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1872635 Apr 20 09:43 flux_flags_2000_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1867784 Apr 20 09:45 flux_flags_2001_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1867705 Apr 20 09:47 flux_flags_2002_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1867547 Apr 20 09:49 flux_flags_2003_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1872793 Apr 20 09:51 flux_flags_2004_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1868179 Apr 20 09:53 flux_flags_2005_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1869364 Apr 20 09:55 flux_flags_2006_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1868811 Apr 20 09:57 flux_flags_2007_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1873935 Apr 20 09:59 flux_flags_2008_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1868057 Apr 20 10:01 flux_flags_2009_ver.2011.04.20.dat > -rw-r--r-- 1 sburns aster 1868057 Apr 20 10:03 flux_flags_2010_ver.2011.04.20.dat