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The interactions between aerosols and clouds are among the least understood climatic processes and were studied over Ascension Island. A ground-based UV polarization lidar was deployed on Ascension Island, which is located in the stratocumulus-to-cumulus transition zone of the southeastern Atlantic Ocean, to infer cloud droplet sizes and droplet number density near the cloud base of marine boundary layer cumulus clouds. The aerosol-cloud interaction (ACI) due to the presence of smoke from the African continent was determined during the monsoonal dry season. In September 2016, a cloud droplet number density ACIN of 0.3±0.21 and a cloud effective radius ACIr of 0.18±0.06 were found, due to the presence of smoke in and under the clouds. Smaller droplets near the cloud base makes them more susceptible to evaporation, and smoke in the marine boundary layer over the southeastern Atlantic Ocean will likely accelerate the stratocumulus-to-cumulus transition. The lidar retrievals were tested against more traditional radar-radiometer measurements and shown to be robust and at least as accurate as the lidar-radiometer measurements. The lidar estimates of the cloud effective radius are consistent with previous studies of cloud base droplet sizes. The lidar has the large advantage of retrieving both cloud and aerosol properties using a single instrument.

For the first time, the Michigan Educational Assessment Program emphasizes providing classroom teachers with extensive information about the performance of students on selected performance objectives that are tested in the program. This guide was prepared to help educators interpret the information provided for individual students and for classroom groups. This booklet contains four sections. The first section describes the tests used in the 1973-74 educational assessment program. The second section describes and illustrates the various report forms that are used to present individual student and classroom data. The third section contains aids in interpreting the information contained in the reports. The final section contains cautions that should be exercised in the interpretation of individual student and classroom reports. The selected performance objectives measured by the objective-referenced mathematics and reading tests are given in Appendix A of this report. (Author)

This explanatory report was prepared to assist educators in the interpretation of the local and school district summary reports provided by the 1973-74 Michigan Educational Assessment Program. Information concerning the interpretation of student and classroom reports was provided in a separate report. The first section of this report describes the educational assessment measures used in the 1973-74 program. The second contains aids for interpreting the information contained in the reports and includes facsimiles of the forms used to report assessment results to local school districts. The final section contains cautions that should be exercised in the interpretation of the school and school district reports. Appendix A contains a listing of the mathematics and reading performance objectives for grades four and seven assessed in the 1973-74 program; Appendix B contains the norm tables necessary for interpreting the human and financial resource information at the school and district levels; Appendix C contains the definitions of the educational assessment measures. (Author)

Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN and IN over large areas have not been possible and can be only roughly approximated from satellite-sensor-based estimates of optical properties of aerosols. Our lack of ability to measure both CCN and cloud updrafts precludes disentangling the effects ofmeteorology fromthose of aerosols and represents the largest component in our uncertainty in anthropogenic climate forcing.Ways to improve the retrieval accuracy include multiangle and multipolarimetric passive measurements of the optical signal and multispectral lidar polarimetric measurements. Indirect methods include proxies of trace gases, as retrieved by hyperspectral sensors. Perhaps the most promising emerging direction is retrieving the CCN properties by simultaneously retrieving convective cloud drop number concentrations and updraft speeds, which amounts to using clouds as natural CCN chambers. These satellite observations have to be constrained by in situ observations of aerosol-cloud-precipitation-climate (ACPC) interactions, which in turn constrain a hierarchy of model simulations of ACPC. Since the essence of a general circulation model is an accurate quantification of the energy and mass fluxes in all forms between the surface, atmosphere and outer space, a route to progress is proposed here in the form of a series of box flux closure experiments in the various climate regimes. A roadmap is provided for quantifying the ACPC interactions and thereby reducing the uncertainty in anthropogenic climate forcing.