1/31/97 OH, H2SO4, MSA Measurements NCAR Fred Eisele The data presented for final submission differ from that presented in the preliminary submission. The calibration for OH makes use of the H2O absortion cross-section and the data in the preliminary submission were calculated using a value of 5.5 x 10-20 molec/cm2 for an H2O absorption cross-section at 1849 nm. Recent work performed NCAR and Harvard indicate that the reported value should be higher. A value of 7.2 x 10-20 molec/cm2 was used in this analysis. The H2O cross-section may decrease as much as 10% with decreasing temperature, thus the values reported for higher altitudes may actually be lower than reported. The values presented in the preliminary submission were calculated using a calibration constant measured at sea-level, where an altitude dependent calibration constant was used in this analysis. The calibration constant was found to increase as a function of altitude, and the data presented here were analyzed using an exponential fit to the measured calibration values. Conditions during the mission were such that calibrations could not be reliably made at altitudes > 20,000 feet, thus the calibration values were held constant for altitudes higher than 465 mBar. Due to the low water concentration at higher altitudes, it is difficult to obtain calibrations except at night when ambient OH ~ 0. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. A few of the later flights (2-5) were plagued with detector problems which greatly enhanced scatter in the measured data. This scatter should not significantly alter the uncertainty of the data except that a larger number of data points must be averaged to reduce the scatter in this data. The reported error for flights 2-5 is +/- a factor of two for measurements made at pressures above 940 mBar and an additional 20% for meassurements made below 940 mBar. The increase in uncertainty at higher altitudes reflects the increased spread in the observed calibration coefficients and the increased uncertainty in the concentration of H2O at higher altitudes. Times reported are the beginning of the measurements period. To obtain times for the middle of the measurement period add 15 sec for the data reported on 30 sec intervals, and 30 sec for the OH data reported on 1 min intervals. Data values reported as -- are null values, with no value being reported for that time. We ask that we be contacted before any work is published containing this data. Contact either: Lee Mauldin mauldin@acd.ucar.edu (303) 497-1861 or Fred Eisele eisele@acd.ucar.edu (303) 497-1483 Flight 01 Instrument was plagued with high noise, due to a bad signal pre-amp. No data is reported for this flight. Flight 02 Instrument was still operating with bad signal pre-amp. H2SO4 was measured periodically during the flight. Reported error is +/- a factor of two for measurements made above 940 mBar, and an addtional 20% for measurements made below 040 mBar. Flight 03 Instrument was still operating with bad signal pre-amp. H2SO4 was measured periodically during the flight. Reported error is +/- a factor of two for measurements made above 940 mBar, and an addtional 20% for measurements made below 040 mBar. Flight 04 Instrument was still operating with bad signal pre-amp. H2SO4 was measured during the flight. The H2SO4 values are reported ass 30 sec measurements. The increase in noise level increases the uncertainty for the measurements. The precision can be increased by averaging the 30 sec H2SO4 values over longer time periods. Reported error is +/- a factor of two for measurements made above 940 mBar, and an addtional 20% for measurements made below 040 mBar. Flight 05 Instrument had signal pre-amp replaced before the flight. Measurements were still plagued with incidents of high noise levels. The problem seemed to diminish later in the flight. H2SO4 was measured periodically during the flight. Reported error is +/- a factor of two for measurements made above 940 mBar, and an addtional 20% for measurements made below 040 mBar. Flight 06 Instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. The large amount of scatter in the OH values at altitudes > 5500 m has no found systematic cause, and could be due to changing dew point. These OH values should be considered to have the same error as high altitude values reported for earlier flights. The remaining measurements have a reported error limits of +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 07 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 08 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 09 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 10 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 11 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 reported on 30 sec intervals. No MSA was measured this flight. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 12 The instrument ran nominally well the entire flight. OH was measured on one min intervals, and H2SO4 and MSA reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 13 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 14 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 15 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 16 The instrument ran nominally well the entire flight, with the exception of a circuit which controlled the switching between OH signal and background. OH was measured on one min intervals, and H2SO4 reported on 30 sec intervals. No MSA was measured on this flight. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 17 The instrument ran nominally well the entire flight. Propane required for OH measurements ran out at ~29:00 (UTC since 00:00 11/27/95), thus no OH values are reported after this time. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 18 The instrument ran nominally well the entire flight. Propane required for OH measurements was replaced since the last flight, with a lower quality propane. This propane yielded artificially high OH background values resulting in an apparent negative offset in OH values. This offset has been estimated to be ~2.3 x 10^5 molec/cc OH. This value was determined from OH measurements at night, when the [OH] should be zero. This amount of OH should be added to the reported values to yield correct OH values. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 19 The instrument ran nominally well the entire flight. A lower quality propane (required for OH measurements) was used. This propane yielded artificially high OH background values resulting in an apparent negative offset in OH values. This offset has been estimated to be ~2.3 x 10^5 molec/cc OH. This value was determined from OH measurements at night on flight 18, when the [OH] should be zero. This amount of OH should be added to the reported values to yield correct OH values. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 20 The instrument ran nominally well the entire flight. A lower quality propane (required for OH measurements) was used. This propane yielded artificially high OH background values resulting in an apparent negative offset in OH values. This offset has been estimated to be ~2.3 x 10^5 molec/cc OH. This value was determined from OH measurements at night on flight 18, when the [OH] should be zero. This amount of OH should be added to the reported values to yield correct OH values. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 21 The instrument ran nominally well the entire flight. A lower quality propane (required for OH measurements) was used. This propane yielded artificially high OH background values resulting in an apparent negative offset in OH values. This offset has been estimated to be ~2.3 x 10^5 molec/cc OH. This value was determined from OH measurements at night on flight 18, when the [OH] should be zero. This amount of OH should be added to the reported values to yield correct OH values. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 22 The instrument ran nominally well the entire flight. A lower quality propane (required for OH measurements) was used. This propane yielded artificially high OH background values resulting in an apparent negative offset in OH values. This offset has been estimated to be ~2.3 x 10^5 molec/cc OH. This value was determined from OH measurements at night on flight 18, when the [OH] should be zero. This amount of OH should be added to the reported values to yield correct OH values. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 23 The instrument ran nominally well the entire flight. The low quality propane used on flights 18-22 was replaced with good quality propane. A clogged injector line prevented OH from being measured 12:00-15:00 UTC since 00:00 12/07/95. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 24 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 25 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 26 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 27 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. There are two periods (25:30-26:30 and 28:00-29:00 UTC since 00:00 12/10/95 where H2SO4 was measured on 0.15 sec intervals. During this time the instrument was exclusively measuring H2SO4, thus no other values are reported. These fast time H2SO4 values have a detection sensitivity of ~1 x 10^6 molecule/cc. Better detection sensitivities can be achieved by averaging these values over longer time intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 28 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 29 The instrument experienced a short in the atmospheric pressure electrostatic lenses for most of the flight, thus few measurements are reported. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 30 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 31 Due to clouds and concerns of condensation, the instrument was off line for ~ the first half of the flight. When operational, the instrument ran nominally well. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 32 The instrument ran nominally well the entire flight. OH, H2SO4 and MSA are reported on 30 sec intervals. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma. Flight 33 The instrument ran nominally well, with the exception of the OH measurements. A clogged injector line prevented OH measurements from being made. H2SO4 and MSA are reported on 30 sec intervals. At ~24:00 UTC since 00:00 12/22/95, the buffer N2 cylinder ran out preventing further measurments. Reported error limits are +/- 42.0% for measurements made at pressures above 940 mBar, and +/- 62.0% for measurements made below 940 mBar. The quoted errors are 2 sigma.