John J. DeLuisi

Optical depth, size distribution and flux of dust from Owens Lake, California

A joint United States/Russian/French collaborative experiment was undertaken in March 1993 and March 1996. Projects LODE I and II (Lake Owens Dust Experiments) took place on the anthropogenically desertified playa (dry lakebed) and surrounding regions of Owens Lake, in east-central California. One of the five parts of Project LODE was to determine relationships between optical depth and flux of dust emitted from the dry lake. Project LODE II included subsequent dust plume measurements and size distributions obtained through April 1996, to further refine the flux measurements for distinct mineral aerosol source regions at Owens Lake. Size distributions of dust aerosol were determined and aerosol optical depths were calculated from sunphotometer solar extinction measurements taken downwind in plumes coming from the emissive areas of Owens Lake. This source was visually observed for 10 measured dust storms. The plume mass was calculated to be 1·5 × 109 g using ground-based measurements and ≥1·6 × 109 g from satellite data. Project LODE II results were found to be consistent with LODE I results for the south end of the playa, but flux values were found to be reduced for the northeastern portion of the playa by comparison. Vertical flux values estimated by sunphotometry were found to be consistent with values estimated via a micrometeorological method. Copyright

PIXE analysis of south pole aerosol

Abstract The Geophysical Monitoring tor Climatic Change (GMCC) program of the National Oceanic and Atmospheric Administration (NOAA) operates an atmospheric monitoring observatory at Amundsen-Scott Station, South Pole. Long-term measurements of carbon dioxide, ozone, aerosols, and other background pollutants are obtained to understand their possible effects on the earths climate. The aerosol measurement program consists of the continuous measurement of condensation nucleus (CN) concentration and aerosol scattering extinction coefficient ( σ sp ). During 1982 Nuclepore-filter aerosol samples were taken with 8-h time resolution for analysis by the proton induced X-ray emission (PIXE) technique. A time series of sodium, chlorine, and sulfur concentrations shows that the sulfur and CN records are similar and that the sodium, chlorine, and σ sp records are similar. Episodes of sodium are measured at the ground in the austral winter and are apparently caused by large-scale transport from coastal regions and vertical transport to the surface during times of surface warming and weakening of the surface temperature inversion. These episodes are characterized by increases in sodium concentration, CI/Na ratio, σ sp , and particle size, and decreases in nonseasalt sulfur concentration, suggesting a decrease in atmospheric acidity with a displacement of sulfuric acid aerosol. An analysis of back trajectories suggests transport times of several days from the Antarctic coast.

Interpretation of Mauna Loa atmospheric transmission relative to aerosols, using photometric precipitable water amouts

Precipitable water measurements made coincident in time and space with direct broadband solar irradiance measurements are used in conjunction with an atmospheric transmission model to derive a parameter whose major dependence is on total aerosol extinction. Irradiance measurements are used to calculate an atmospheric transmission factor (ATF) that is independent of the instrument calibration and the extraterrestrial solar constant. The dependency of the ATF on precipitable water is determined using LOWTRAN5, an atmospheric transmission model with high spectral resolution. Precipitable water measurements are then used to adjust the measured ATF to correspond to an ATF value obtained for a constant precipitable water amount. The remaining variability in the adjusted ATF is due mostly to aerosol extinction. The technique is applied to a 6-year period (1978–1983) for clear-sky mornings at Mauna Loa, Hawaii (MLO). MLO ATF aerosol residuals are compared with independently measured monochromatic aerosol optical depth. Results show that the ATF aerosol residual is nearly equal to the 500 nm aerosol optical depth prior to the eruption of E1 Chichon, at which time a nonlinear time-dependent relationship between the two quantities is evident. ATF aerosol residuals reflect the spectrally integrated aerosol influence on transmission and, therefore, could indicate better than monochromatic optical depth the radiation balance perturbations due to aerosols. The 6-year precipitable water record for MLO, determined from a dual-channel sunphotometer, has a mean value of 0.3 cm. An annual cycle in precipitable water is evident, as is a 4-month 5-standard-deviation “drought” from December 1982 through March 1983.

An Aerosol Climatology of Samoa

An atmospheric monitoring station is operated at Cape Matatula, American Samoa, by the Geophysical Monitoring for Climatic Change program under the National Oceanic and Atmospheric Administration. A nearly continuous record of condensation nucleus (CN) concentration and multiwavelength aerosol scattering extinction coefficient (σsp) is available from mid-1977 to the present. This report presents the 1977–1983 data. The long-term mean of CN concentration is 274 cm-3 the long-term mean of σsp (550 nm) is 1.54×10-5, and no significant long-term, annual, or diurnal trend is apparent in either data record.

Shortwave aerosol optical depth of Arctic haze measured on board the NOAA WP-3D during AGASP-II, April 1986

Measurements of spectral aerosol optical depth in the Alaskan and Canadian Arctic were made from the NOAA Lockheed WP-3D aircraft as part of the second Arctic Gas and Aerosol Sampling Program (AGASP-II) during April 1986. The flight tracks and altitudes flown enabled measurements of the vertical and horizontal distribution of aerosol optical depth in the troposphere as well as direct determination of the stratospheric component. Tropospheric aerosol optical depth ranged from about 0.1 to 0.7. The factor of 7 variability sometimes occurred within 50 km horizontally; comparable variability occurred within less than 1 to 2 km vertically. The Angstrom exponents of the spectral optical depths ranged from 0.5 to 2.0, and some of the variability was apparently related to distinct aerosol regimes.

Comparison of NOAA‐11 SBUV/2 ozone vertical profiles with correlative measurements

Vertical profiles of ozone have been determined from observations with the Solar Backscatter Ultraviolet (SBUV/2) instrument on the NOAA-11 operational satellite. These observations began in January 1989 and continue to early 1995. Comparisons have been made with selected sets of ozone vertical profiles derived from an ensemble of satellite and land-based measurements. These include; 1) lidar and microwave measurements performed at Table Mountain, CA. 2) Umkehr observations with a mid-northern latitude set of Dobson spectrophotometers. 3) balloon ozonesondes launched from Boulder, CO. 4) measurements with the NASA SBUV on Nimbus-7. Overall, the SBUV/2 profiles within the altitude range of 1–20mb agree with the other measurements to about ±5% with a −3 to −5% bias, the SBUV/2 values being lower. This level of agreement is consistent with the expected performance of the SBUV/2 instrument based on an extensive characterization of the instrument both in pre-launch calibration and in-orbit performance and also with current understanding of the test optical components used in pre-flight calibration.

South Pole aerosol measurements during 1987

An aerosol experiment was conducted during 1987 at the Amundsen-Scott station, South Pole. We measured condensation nuclei (CN) concentration, aerosol scattering extinction ((Yp), aerosol chemistry, aerosol size distribution in the Aitken size range, and aerosol carbon concentration. In addition, a complete set of meteorology data was obtained.