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The response of the Forward Scattering Spectrometer probe (FSSP) is affected by the optical properties of measured particles. The manufacturer's size calibration data are specifically applicable to nonabsorbing water droplets. Response functions of the FSSP probe are calculated for different complex refractive indices corresponding to different types of atmospheric aerosols under various relative humidity Conditions. Based on the results of these response calculations, new corrected size calibrations are determined for six relative humidity values (0%, 50%, 70%, 80%, 90% and 99%) and for three atmospheric aerosol types (Rural, Urban and Maritime). Sample calculations with these corrected size calibration data show that a significant underestimation of the aerosol size/volume distribution can result, especially for dry atmospheric aerosols, if the manufacturer's size calibration data are used.

Measurements of H2O2 and related species were made by aircraft on 18 flights over 11 days during June 1987 over Ohio. Measurements typically encompassed an altitude range from the surface to 5.5 km above mean sea level and were conducted under a variety of meteorological conditions, but focussed on conditions conducive to the formation of convective storms. Concentrations of H2O2 ranged from

Airborne gamma-ray measurements were made aboard the Pacific Northwest Laboratory (PNL) DC-3 and the National Oceanic and Atmospheric Administration (NOAA) King Air research aircraft before and during the first passage of the Chernobyl radioactive cloud over the west coast of the North American continent. Measurements were made from Anchorage, Alaska south to Reno, Nevada. Calculated trajectories were used to estimate the location of the Chernobyl plume. The in-situ gamma-ray analysis systems first detected the cloud on May 8, 1986. Subsequent analysis of concurrently collected air filters indicated that the leading edge of the plume was just reaching the west coast of the United States on May 6, 1986. The ratios of the observed volatile radionuclides (131I and134Cs normalized to137Cs) agreed with the reported discharge ratio.

Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems.

Airborne measurements of NOx, NOy, CO, and O3 were conducted in the vicinity of a line of towering cumulus and cumulonimbus clouds (approximate altitude, 9 km) in south-central Oklahoma, on the afternoon of June 17, 1985. NOx, NOy, and CO concentrations in the upper tropospheric outflow region of these clouds were near environmental levels. Meteorological analyses show that these clouds were located above a cold front, which prevented the entry of air from the boundary layer directly below and near the cloud. Examination of the [NOy]/[CO] and [NOx]/[CO] ratios, as well as determination of the lifting condensation level and other thermodynamic analyses, indicated that the most likely origin of the air in the cloud outflow region was the layer immediately above the top of the boundary layer, which was quite clean. It appears that very little NOy was available to be scavenged by the clouds. The results for this case suggest that the large amount of vertical trace gas transport that has been noted in previous observations and model results cannot simply be extrapolated to all convective cells. The results also show the usefulness of CO as a conserved tracer.