SGP/RL/C1 - Interference filter replaced temporarily

The sensitivity of the Raman lidar has been degrading since the fall of 2005.  One 
possible source of the degradation is the interference filters; i.e., their transmission could 
be becoming smaller for some reason.  To evaluate this hypothesis, we removed the 
interference filter from the narrow field-of-view nitrogen channel (i.e., the N2 high channel) on 
3/9/2007, and replaced it with its spare.  

The original filter was sent to the manufacturer for evaluation.  Its transmission was 
measured by the manufacturer to be nearly identical to its original performance; in other 
words, the filter is not responsible for the lidar's loss of sensitivity.  The original 
interference filter was reinstalled in the system on 3/23/2007.  

The temporary use of the spare interference filter in the high N2 channel should not 
affect the data quality, as the transmission characteristics of the spare and the original 
filter are nearly identical.

• Cloud optical thickness computed from nitrogen data(cloud_optical_thickness_n2)
• base time(base_time)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Number of laser shots recorded(shots_summed)
• Depolarization calibration factor(calibration_factor)
• cloud top height(cloud_top_height)
• lon(lon)
• lat(lat)
• Cloud attenuation flag(attenuation_flag)
• Cloud depth(cloud_depth)
• Cloud base height, measured by MPL(cloud_base_height)
• Average laser energy of the ensemble shots(average_energy)
• Linear depolarization ratio profile(depolarization_ratio)
• Dummy altitude for Zeb(alt)
• Array of heights for the range gates(height)
• Cloud mask(cloud_mask)
• Cloud optical thickness computed from aerosol (elastic) data(cloud_optical_thickness_aer)
• Time offset of tweaks from base_time(time_offset)
• Uncertainty of the linear depolarization ratio profile(depolarization_ratio_error)

• Cloud liquid water vapor by the microwave radiometer(liq_mwr)
• Fraction of the total column amount of water vapor the Raman lidar senses(pwv_rl_fraction)
• relative humidity with respect to saturation over a flat surface of liquid wate(relative_humidity)
• Calibration factor used to match the high channel mixing ratio to the low
  channel mixing ratio(calib_high_low)
• Precipitable water vapor observed by the microwave radiometer(pwv_mwr)
• Precipitable water vapor observed by the Raman lidar(pwv_rl)
• Random error in the precipitable water vapor observed by the Raman lidar(pwv_rl_err)
• Height range of the high channel water vapor mixing ratio profile(height_high)
• Array of heights for the range gates(height)
• Uncertainty of the water vapor mixing ratio profile created by merging the two
  calibrated channels(mixing_ratio_3_error)
• Average laser energy of the ensemble shots(average_energy)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Water vapor mixing ratio(mixing_ratio_other)
• Suggested maximum altitude to use the water vapor data from the Raman lidar(wv_rl_max_height)
• Water vapor mixing ratio profile from the low channel(mixing_ratio_low)
• Water vapor mixing ratio profile from the high channel(mixing_ratio_high)
• Vertical resolution of bright mode (mode == 2) data(vertical_resolution_bright_mode)
• Uncertainty of the water vapor mixing ratio profile created by merging the two
  channels(mixing_ratio_1_error)
• Uncertainty of the water vapor mixing ratio profile from the high channel(mixing_ratio_error_high)
• Number of laser shots recorded(shots_summed)
• Dummy altitude for Zeb(alt)
• Vertical resolution of normal mode (mode == 1) data(vertical_resolution_normal_mode)
• base time(base_time)
• Differential transmission correction for aerosols(diff_trans_aerosol_corr)
• air temperature (NGM250 predicted)(temperature)
• Water vapor mixing ratio profile created by merging the two calibrated channels
  together with the surface in-situ measurements(mixing_ratio_3)
• Flag indicating whether or not there was a sample from the temperature_source
  dataset during the lidars averaging interval (1) or not (0)(sample_times_other)
• Uncertainty of the water vapor mixing ratio profile from the low channel(mixing_ratio_error_low)
• Height range of the low channel water vapor mixing ratio profile(height_low)
• atmospheric pressure at mean sea level and at tropopause (NGM250 predicted)(pressure)
• Time offset of tweaks from base_time(time_offset)
• Calibration factor for entire profile(calib_factor)
• Uncertainty of the water vapor mixing ratio profile created by merging the two
  calibrated channels(mixing_ratio_2_error)
• Water vapor mixing ratio profile created by merging the two calibrated channels(mixing_ratio_2)
• lon(lon)
• Cloud base height(cloud_base_height_other)
• Water vapor mixing ratio profile created by merging the two channels(mixing_ratio_1)
• lat(lat)
• Relative humidity over ice calculated from the merged water vapor mixing ratio
  data(relative_humidity_over_ice)
• Mode of the dataset (as defined by the filter arrangement of the lidar)(mode)

• Vertical resolution of the merged aerosol extinction coefficient profile data(extinction_1_resolution)
• Uncertainty of the aerosol extinction coefficient profile created by merging the
  two N2 channels extinction profiles(extinction_1_error)
• Aerosol extinction coefficient profile from the high N2 channel data, where the
  low N2 channel was used to correct for the overlap of the high channel(extinction_high_olap_corrected)
• Maximum altitude used in the calculation of the aerosol optical depth from the
  extinction_1 profile(aod_1_max_ht)
• Error in the aerosol optical depth calculated from the extinction_married1
  profile(aod_married1_error)
• Uncertainty in the aerosol backscatter coefficient at 355 nm(backscatter_error)
• Height range of the low channel water vapor mixing ratio profile(height_low)
• Aerosol extinction coefficient profile calculated from backscatter and the
  extinction-to-backscatter ratio(extinction_from_backscatter)
• Uncertainty of the aerosol extinction coefficient profile calculated from the
  aerosol backscatter coefficient(extinction_from_backscatter_error)
• Vertical resolution of the high aerosol extinction coefficient profile data(extinction_high_resolution)
• Uncertainty of the aerosol extinction coefficient profile from the high N2
  channel(extinction_high_error)
• Vertical resolution of the low aerosol extinction coefficient profile data(extinction_low_resolution)
• Error in the aerosol optical depth calculated from the
  extinction_from_backscatter profile(aod_bscat_error)
• lat(lat)
• Aerosol optical depth from the surface computed from the
  extinction_from_backscatter profiles(aod_bscat_profile)
• Maximum altitude used in the calculation of the aerosol optical depth from the
  extinction_from_backscatter profile(aod_bscat_max_ht)
• Maximum altitude used in the calculation of the aerosol optical depth from the
  extinction_married1 profile(aod_married1_max_ht)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Mask indicating from where the extinction value came from in the aerosol
  extinction coefficient profile created by marrying the merged extinction from N2
  data w(extinction_married1_mask)
• Error in the aerosol optical depth calculated from the extinction_1 profile(aod_1_error)
• Aerosol extinction coefficient profile from the low N2 channel data(extinction_low)
• Aerosol extinction coefficient profile created by merging the two N2 channels
  extinction profiles(extinction_1)
• Uncertainty of the aerosol extinction coefficient profile from the overlap
  corrected high N2 channel(extinction_high_olap_corrected_error)
• Height range of the high channel water vapor mixing ratio profile(height_high)
• Ratio of aerosol extinction to aerosol backscatter(Sa_1)
• Aerosol optical depth calculated from the extinction_1 profile(aod_1)
• Average laser energy of the ensemble shots(average_energy)
• Aerosol optical depth from the surface computed from the extinction_1 profiles(aod_1_profile)
• Uncertainty of the married aerosol extinction coefficient profile(extinction_married1_error)
• base time(base_time)
• Aerosol optical depth calculated from the extinction_married1 profile(aod_married1)
• Aerosol optical depth calculated from the extinction_from_backscatter profile(aod_bscat)
• Aerosol backscatter coefficient at 355 nm - smoothed to N2 extinction resolution(smoothed_backscatter)
• Uncertainty of the aerosol extinction coefficient profile from the low N2
  channel(extinction_low_error)
• Aerosol optical depth from the surface computed from the married1 extinction
  profiles(aod_married1_profile)
• Mode of the dataset (as defined by the filter arrangement of the lidar)(mode)
• Time offset of tweaks from base_time(time_offset)
• Number of laser shots recorded(shots_summed)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Dummy altitude for Zeb(alt)
• Uncertainty in the aerosol backscatter coefficient at 355 nm - smoothed to N2
  extinction resolution(smoothed_backscatter_error)
• Aerosol extinction coefficient profile created by marrying the merged extinction
  from N2 data with the extinction from backscatter data(extinction_married1)
• lon(lon)
• Ratio of aerosol extinction to aerosol backscatter(Sa_2)
• Aerosol extinction coefficient profile from the high N2 channel data(extinction_high)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

• Calibrated Aerosol scattering ratio profile from the low channel(cal_asr_low)
• lat(lat)
• Cloud mask(cloud_mask)
• base time(base_time)
• lon(lon)
• Vertical scale factor to make shape of high channel profile match low channel(vert_scale_hi)
• Scale factor added to the high aerosol scattering ratio at each time sample and
  height (2nd iteration)(scale_add_hi_2)
• Corrected Aerosol volume backscattering coefficient at 355 nm - removed negative
  vals(corr_bscat)
• air temperature (NGM250 predicted)(temperature)
• Dummy altitude for Zeb(alt)
• Type of calibration used to compute the high channel calibration at each time
  interval(hi_cal_type)
• Uncertainty of the aerosol scattering ratio profile from the low channel(asr_error_low)
• Random error in the aerosol backscatter coefficient profile(bscat_err)
• Time offset of tweaks from base_time(time_offset)
• Calibration factor applied to the low aerosol scattering ratio at each time
  sample(cal_factor_lo)
• Average laser energy of the ensemble shots(average_energy)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Vertical scale factor for statistical T-test sanity check on high channel data(vert_scale_hi_2)
• Aerosol scattering ratio profile created by merging the two Calibrated channels(cal_asr_1)
• Uncertainty of the aerosol scattering ratio profile created by merging the two
  channels(asr_1_error)
• Calibration factor applied to the high aerosol scattering ratio at each time
  sample(cal_factor_hi)
• Uncertainty of the aerosol scattering ratio profile from the high channel(asr_error_high)
• Aerosol scattering ratio profile from the high channel(asr_high)
• Uncertainty of the Calibrated aerosol scattering ratio profile from the high
  channel(cal_asr_error_high)
• Aerosol scattering ratio profile from the low channel(asr_low)
• Aerosol scattering ratio profile created by merging the two channels(asr_1)
• Uncertainty of the aerosol scattering ratio profile created by merging the two
  Calibrated channels(cal_asr_1_error)
• Scale factor added to the low aerosol scattering ratio at each time sample(scale_add_lo)
• Height range of the high channel water vapor mixing ratio profile(height_high)
• Uncertainty of the Calibrated aerosol scattering ratio profile from the low
  channel(cal_asr_error_low)
• Calibrated Aerosol scattering ratio profile from the high channel(cal_asr_high)
• Scale factor added to the high aerosol scattering ratio at each time sample and
  height(scale_add_hi)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Differential transmission correction for aerosols(diff_trans_aerosol_corr)
• Height range of the low channel water vapor mixing ratio profile(height_low)
• Number of laser shots recorded(shots_summed)

• Linear depolarization ratio profile(depol)
• Random error in the aerosol extinction coefficient profile(ext_err)
• lon(lon)
• Random error in the precipitable water vapor observed by the Raman lidar(pwv_rl_err)
• Resolution of the aerosol scattering ratio profile(scattering_ratio_resolution)
• Water vapor mixing ratio from the Raman lidar near 60 m(rl_w_60m)
• Number of laser shots recorded(shots_summed)
• Random error in the water vapor mixing ratio profile(w_err)
• Random error in the aerosol optical depth(aod_err)
• Average laser energy of the ensemble shots(average_energy)
• Water vapor mixing ratio error from the Raman lidar near 60 m(rl_w_60m_err)
• Random error in the aerosol backscatter coefficient profile(bscat_err)
• Flag indicating whether or not there was a sample from the temperature_source
  dataset during the lidars averaging interval (1) or not (0)(sample_times_other)
• Aerosol scattering ratio profile(asr)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Dummy altitude for Zeb(alt)
• Aerosol extinction coefficient at 355 nm(ext)
• Aerosol optical depth profiles at 355 nm(aod_profile)
• Time offset of tweaks from base_time(time_offset)
• Water vapor mixing ratio from the 60 m tower(twr_w_60m)
• Maximum altitude used while computing AOD from the extinction profile(aod_max_height)
• Resolution of the water vapor profiles(mixing_ratio_resolution)
• Resolution of the depolarization ratio profile(depolarization_resolution)
• lat(lat)
• Cloud base height(cbh)
• Random error in the aerosol scattering ratio profile(asr_err)
• Cloud liquid water vapor by the microwave radiometer(liq_mwr)
• Random error in the linear depolarization ratio profile(depol_err)
• Array of heights for the range gates(height)
• Suggested maximum altitude to use the water vapor data from the Raman lidar(w_max_height)
• Mode of the dataset (as defined by the filter arrangement of the lidar)(mode)
• Pressure(p)
• Precipitable water vapor observed by the microwave radiometer(pwv_mwr)
• Fraction of the total column amount of water vapor the Raman lidar senses(pwv_rl_fraction)
• Resolution of the aerosol extinction and backscatter profiles(extinction_resolution)
• Water vapor mixing ratio profile(w)
• Aerosol backscatter coefficient at 355 nm(bscat)
• Temperature(t)
• Cloud mask(cmask)
• Aerosol optical depth at 355 nm(aod)
• Relative humidity inside the instrument enclosure(rh)
• base time(base_time)
• Precipitable water vapor observed by the Raman lidar(pwv_rl)

• Number of laser shots recorded for the high nitrogen channel(shots_summed_nitrogen_high)
• Supplemental 8(s8)
• Dummy altitude for Zeb(alt)
• Time offset of tweaks from base_time(time_offset)
• Number of laser shots recorded for the high elastic channel(shots_summed_elastic_high)
• Laser pulse energy(pulse_energy)
• Number of photons counted in the low elastic (aerosol) channel(elastic_counts_low)
• Number of photons counted in the high water vapor channel(water_counts_high)
• Supplemental 11(s11)
• Temperature 3 inside the instrument enclosure(temp3)
• Summed analog signal in the low water vapor channel(water_analog_low)
• Supplemental 10(s10)
• Number of photons counted in the high depolarization channel(depolarization_counts_high)
• Supplemental 5(s5)
• Temperature 1 inside the instrument enclosure(temp1)
• Supplemental 6(s6)
• Supplemental 3(s3)
• Number of photons counted in the high elastic (aerosol) channel(elastic_counts_high)
• Temperature 4 inside the instrument enclosure(temp4)
• Summed analog signal in the low nitrogen channel(nitrogen_analog_low)
• Supplemental 1(s1)
• Temperature 5 inside the instrument enclosure(temp5)
• Supplemental 2(s2)
• Supplemental 7(s7)
• Temperature 2 inside the instrument enclosure(temp2)
• Number of photons counted in the low nitrogen channel(nitrogen_counts_low)
• Supplemental 4(s4)
• Number of laser shots recorded for the high water channel(shots_summed_water_high)
• Relative humidity inside the instrument enclosure(rh)
• Number of laser shots recorded for the low elastic channel(shots_summed_elastic_low)
• time(time)
• Number of laser shots recorded for the low nitrogen channel(shots_summed_nitrogen_low)
• Number of photons counted in the high nitrogen channel(nitrogen_counts_high)
• Number of laser shots recorded for the low water channel(shots_summed_water_low)
• Temperature 6 inside the instrument enclosure(temp6)
• Summed analog signal in the high depolarization channel(depolarization_analog_high)
• Nominal number of seconds of data acquired(acquisition_time)
• Number of laser shots recorded(shots_summed)
• Number of photons counted in the low water vapor channel(water_counts_low)
• Number of laser shots recorded for the high depolarization channel(shots_summed_depolarization_high)
• Cloud value check flag(cloud_value_check)
• lat(lat)
• lon(lon)
• Supplemental 9(s9)
• Summed analog signal in the high water vapor channel(water_analog_high)
• Summed analog signal in the low elastic channel(elastic_analog_low)
• Summed analog signal in the high nitrogen channel(nitrogen_analog_high)
• base time(base_time)
• N2 cloud check value(n2_cloud_check_value)
• Supplemental 12(s12)
• Summed analog signal in the high elastic channel(elastic_analog_high)
• Laser head in use(laser_head)
• Flag indicating the filters (or lack of) added to the instrument(filter)

• Water vapor mixing ratio profile(w)
• Flag denoting the occurrence of power or alignment tweaks(tweaks)
• Resolution of the aerosol scattering ratio profile(scattering_ratio_resolution)
• Mode of the dataset (as defined by the filter arrangement of the lidar)(mode)
• Pressure(p)
• Dummy altitude for Zeb(alt)
• Cloud base height(cbh)
• Precipitable water vapor observed by the microwave radiometer(pwv_mwr)
• Flag indicating whether or not there was a sample from the temperature_source
  dataset during the lidars averaging interval (1) or not (0)(sample_times_other)
• Random error in the aerosol optical depth(aod_err)
• base time(base_time)
• Fraction of the total column amount of water vapor the Raman lidar senses(pwv_rl_fraction)
• Suggested maximum altitude to use the water vapor data from the Raman lidar(w_max_height)
• Water vapor mixing ratio from the 60 m tower(twr_w_60m)
• Resolution of the water vapor profiles(mixing_ratio_resolution)
• Relative humidity inside the instrument enclosure(rh)
• Aerosol optical depth at 355 nm(aod)
• Aerosol extinction coefficient at 355 nm(ext)
• Number of laser shots recorded(shots_summed)
• Aerosol backscatter coefficient at 355 nm(bscat)
• Cloud mask(cmask)
• Cloud liquid water vapor by the microwave radiometer(liq_mwr)
• Resolution of the aerosol extinction and backscatter profiles(extinction_resolution)
• lon(lon)
• Water vapor mixing ratio from the Raman lidar near 60 m(rl_w_60m)
• Random error in the aerosol extinction coefficient profile(ext_err)
• Time offset of tweaks from base_time(time_offset)
• Aerosol scattering ratio profile(asr)
• Random error in the linear depolarization ratio profile(depol_err)
• Linear depolarization ratio profile(depol)
• Array of heights for the range gates(height)
• lat(lat)
• Temperature(t)
• Water vapor mixing ratio error from the Raman lidar near 60 m(rl_w_60m_err)
• Precipitable water vapor observed by the Raman lidar(pwv_rl)
• Resolution of the depolarization ratio profile(depolarization_resolution)
• Aerosol optical depth profiles at 355 nm(aod_profile)
• Average laser energy of the ensemble shots(average_energy)
• Random error in the aerosol scattering ratio profile(asr_err)
• Random error in the aerosol backscatter coefficient profile(bscat_err)
• Maximum altitude used while computing AOD from the extinction profile(aod_max_height)
• Random error in the precipitable water vapor observed by the Raman lidar(pwv_rl_err)
• Random error in the water vapor mixing ratio profile(w_err)