Artificial Cloud Seeding Using Liquid Carbon Dioxide: Comparisons of Experimental Data and Numerical Analyses

An artificial seeding experiment was carried out over the Genkai Sea, Japan, using liquid carbon dioxide. The seeded cloud was followed by an aircraft and radar at Kyushu University. A radar-echo intensity of 19 dBZ was formed in the seeded cloud where no radar echo was observed previously. The results of the experiment are analyzed using a numerical model [Weather Research and Forecasting Model (WRF), version 3.1] to evaluate the effects of the artificial seeding. The numerically simulated radar echo has a slightly stronger intensity and wider area than that observed. The results of the experiments were similar to those produced by the numerical model, however. Evaporation of cloud liquid water; growth of snow particles that is due to deposition, autoconversion, aggregation, and collection; and convection caused by released latent heat are shown in the numerical results as effects of the seeding experiment. The falling snow particles cause downward flow, which is compensated for by upward flow that causes the formation of new cloud liquid water as a secondary effect of seeding, although this secondary effect is confirmed only in the numerical results.

Vegetation successions over 30 years of high country grassland invasion by Pinus contorta

The invasion of a high country grassland site (850 m asl) by lodgepole or contorta pine (Pinus contorta Dougl) wildings was monitored over 32 years in the Craigieburn Range Canterbury The first wildings appeared in 1975 By 1985 density had reached 34550 stems/ha with a mean height of 185 m and a basal area of 17 m2/ha By 2007 stocking had dropped to 11400 stems/ha with a mean top height of 143 m and a basal area of 104 m2/ha Thirtyeight plant species were present 10 years after wilding invasion started Twentysix species (68) were indigenous By 2007 the number of species present had dropped to seven none of which were indigenous The introduced tussock hawkweed (Hieracium lepidulum) featured in both assessments It was concluded that more species are likely to invade as the canopy opens up but if native species are wanted they may have to be introduced by artificial seeding

Effects of Thinning, Patch Clearcutting, Site Preparation, and Planting on Development of Yellow Birch in Quebec

This is a report of a 1964 thinning and patch clearcutting to increase the proportion of yellow birch in a sugar maple-yellow birch stand in the Dudswell Forest. In 1984, 20 years after treatment, improved quality, health, and growth of thinned stands were observed. Dieback or partial mortality of the crown varied between 0 and 10% in thinned plots and between 25 and 50% in unthinned plots. Despite this dieback in unthinned plots, net growth between 1979 and 1984 was 6 m3/ha. The abundant natural regeneration was growing well, especially in the openings created by clearcutting. Soil scarification, with or without yellow birch artificial seeding, stimulated yellow birch establishment, but the effect did not persist and had disappeared by 1969 or within 5 years. Planting yellow birch increased the number of dominant yellow birch saplings in 1969 and in 1974 or for 10 years. In 1979, when the first release cutting was carried out in the patches clearcut 15 years before, yellow birch dominated in 4% of the subplots; this increased to 18% after the release cutting. From 1979 to 1984, released yellow birch saplings doubled in diameter and were of better quality than the unreleased ones. North. J. Appl. For. 5:248-251, December 1988.