MWR DATA REPROCESSING NOTES 17 December 1998 Jim Liljegren Ames Laboratory 515-294-8428 liljegren@ameslab.gov ------- SUMMARY ------- Data from the ARM MWR at the SGP central facility (instrument serial number 10) for the period February 1996 - May 1998 have been reprocessed to apply a consistent calibration and to provide quality control flags. Zenith line-of-sight observations have been extracted from the tip curve data files and merged with the LOS data to provide as complete a data set as possible. The data are availble in daily netcdf-formatted files consistent with the original files distributed by ARM. A sample netcdf file header is included at the end of this note. ------- DETAILS ------- 1. Data The following variables are included in the reprocessed files: tbsky23:long_name = "23.8 GHz zenith brightness temperature" ; tbsky31:long_name = "31.4 GHz zenith brightness temperature" ; vap:long_name = "Total water vapor along zenith line-of-sight" ; liq:long_name = "Total liquid water along zenith line-of-sight" ; wet_window:long_name = "Water on Teflon window (1=WET, 0=DRY)" ; qc_flag:long_name = "Data quality flag" ; lat:long_name = "north latitude" ; lon:long_name = "east longitude" ; alt:long_name = "altitude" ; Raw signal levels and instrument temperatures were not repeated from the original netcdf files. 2. Calibration Tip curve data have been re-analyzed to determine and remove a pointing angle offset ranging from 0.5 to 1.5 degrees. A beamwidth correction has also been applied. The calibrations have been linearly interpolated in time, except for a jump in the calibration of the 23.8 GHz channel which occured at 18:00 GMT on 14 March 1997. 3. Quality Control Checks for thermal stabilization (warm-up and overheat), water on the microwave window, unexplained anomalies (spikes), and invalid optical depths (due either to brightness temperatures less than the cosmic background or greater than the mean radiating temperature) have been identified and are included in a new variable named "qc_flag": 0 = good data 1 = water on window likely 2 = thermal stabilization problems (warm-up) 3 = thermal stabilization problems (overheat) 4 = unexplained anomaly (spike) 5 = invalid optical depth (TBTmr) The qc_flag indication of water on the window is based solely on an analysis of the variance of the integrated vapor measurement and the magnitude of the integrated liquid measurement. The output of the dew sensor is also included. This sensor indicates condensing conditions as well as rain and is subject to error depending on several factors. Because the heated blower prevents the formation of dew on the window, condensing conditions cause a false-positive indication. If the sensitivity is not appropriately adjusted for the prevailing temperature range, a false-positive or false-negative indication may result. 4. Sample Netcdf Header netcdf sgpmwrlosC1.b2.970317.000020 { dimensions: time = UNLIMITED ; // (4293 currently) variables: long base_time ; base_time:string = "1997-03-17 00:00:20 GMT" ; base_time:long_name = "Base time in Epoch" ; base_time:units = "seconds since 1970-1-1 0:00:00 GMT" ; double time_offset(time) ; time_offset:units = "seconds" ; time_offset:long_name = "Time offset from base_time" ; float tbsky23(time) ; tbsky23:long_name = "23.8 GHz zenith brightness temperature" ; tbsky23:units = "K" ; float tbsky31(time) ; tbsky31:long_name = "31.4 GHz zenith brightness temperature" ; tbsky31:units = "K" ; float vap(time) ; vap:long_name = "Total water vapor along zenith line-of-sight" ; vap:units = "cm" ; float liq(time) ; liq:long_name = "Total liquid water along zenith line-of-sight" ; liq:units = "cm" ; float wet_window(time) ; wet_window:long_name = "Water on Teflon window (1=WET, 0=DRY)" ; wet_window:units = "unitless" ; wet_window:note = "Window heater ON when wet_window=1" ; float qc_flag(time) ; qc_flag:long_name = "Data quality flag" ; qc_flag:units = "unitless" ; qc_flag:note = "0=good data, 1=water on window, 2=warming up, 3=overheated, 4=spike anomaly, 5=invalid optical depth" ; float lat ; lat:long_name = "north latitude" ; lat:units = "degrees" ; lat:valid_range = -90.f, 90.f ; float lon ; lon:long_name = "east longitude" ; lon:units = "degrees" ; lon:valid_range = -180.f, 180.f ; float alt ; alt:long_name = "altitude" ; alt:units = "meters above sea level" ; // global attributes: :site-id = "sgp" ; :facility-id = "C1 : Central_Facility" ; :ingest-software = "asc2cdf.f,v 1.0 1998/12/15 J.C. Liljegren" ; :creation-date = "1998-12-16 20:09:20 GMT" ; :serial-number = "MWR10" ; :sample-int = "20 seconds" ; :averaging-int = "1 second" ; :beamwidth_23 = " 5.70000" ; :beamwidth_31 = " 4.60000" ; :beamwidth_correction = "ON" ; :noise_injection_at_nominal_temp_23_K = "290.00000" ; :noise_injection_at_nominal_temp_31_K = "290.00000" ; :temperature_correction_coef_23 = " 0.05000" ; :temperature_correction_coef_31 = " 0.04000" ; :teflon_window_correction_coef_23 = " 0.00164" ; :teflon_window_correction_coef_31 = " 0.00217" ; :vapor_retrieval_coefficient_0 = " 0.03140" ; :vapor_retrieval_coefficient_1 = " 22.06200" ; :vapor_retrieval_coefficient_2 = "-12.65700" ; :vapor_retrieval_rms_accuracy_cm = " 0.06090" ; :liquid_retrieval_coefficient_0 = " -0.01357" ; :liquid_retrieval_coefficient_1 = " -0.21847" ; :liquid_retrieval_coefficient_2 = " 0.69196" ; :liquid_retrieval_rms_accuracy_cm = " 0.00349" ; :cosmic_background_temperature_K = " 2.75000" ; :mean_atmos_radiating_temp_23_K = "273.89499" ; :mean_atmos_radiating_temp_31_K = "270.30200" ; :gunn_diode_warmup_time_msec = "250" ; :sample_time_blackbody_msec = "1000" ; :sample_time_blackbody_plus_noise_diode_msec = "1000" ; :sample_time_sky_msec = "1000" ; :missing-data = "-9999" ; }