Ice Nucleus Counts and Variations at 3.4 Km. And Near Sea Level in Hawii

Abstract

Concurrent ice nucleus counts made twice daily at M a m a Loa Observatory (3.4 h i .) and near sea level at Hilo, Hawaii, from December 1, 1061, to February 5 , 1062, and :it intervals of a few minutes during 24 hours on July 10-11, 1963, indicated thc wide fluctuations observed elsewhere, with counts varying not oiily from day to day, but by as mnch as an order of magnitude within minutes. Background levels at M a m a Loa Observatory ran mcll below those a t Hilo and averaged tinder 10 ice crystals in 10 liters a t-24OC., values comparable with the lowest rcportecl from other isolated localities. At both sites diurnal variations, evidently reflecting thc diurnal mountain circulation and its effects, saw afternoon counts a t Mauna Loa Obscrvatory tending to increase with the influx of more turbid air from lower elevations and those at Hilo to decrease from dispersion of the accumulatcd contaminants by convection and onshore winds. Although the investigation was not designed to look into fundamental questions, the rclativcly small distance betwccn thc two stations, their large difference in elevation, and the Observatory's isolation for much of the day from the underlying atmosphere permitted inferences concerning such matters as the source and vertical distribution of the ice nuclei and the possibility of estraterrcstrial (meteoritic) influcnces. It would appear that the ice nuclei observed at Hilo did not ordinarily or in major part come from aloft, but rather from the lower atmosphere, and that-in gcncral, and in thc prescncc of the trade inversion-the number of icc nuclei decreased with height in thc Hawaiian area. Major oscillations in the four ice nucleus count-sequences (Mauna Loa Observatory and Hilo, morning and afternoon) appeared to be closcly synchronous and to accompany the air mas; changes or other synoptic events implied by the deepening and thinning of the moist layer on the Hilo sounding.

Ice-forming Nuclei and Their Dominant Source Region

“…Equally low or very much lower values have been reported in the maritime airmasses, as for example, less than 100 per cubic metre at -20°C in the air from the Pacific Ocean (Isono et al, 1959), 500 per cubic metre at -24°C in Hawaii (Price and Pales, 1964) and less than 2 per litre at -18 °C at Eskdalemiur in England (Stevenson 1968). The question which, however, arises in this context is about the source region of these nuclei in the maritime air.…”

“…Several studies have been made tracing the origin of the natural ice-forming nuclei to the sea (Brier and Kline;1959;Battan and Riley, 1960), to the land (Isono et al 1959;Price and Pales, 1964), to the stratosphere (Bigg and Miles, 1963) and to extra terrestrial sources (Maruyama and Kitagawa, 1967). Based on measurements made at Delhi (28°35' N, 77°12' E, 210 meters A.M.S.L.)…”

Ice nucleation and overseeding of ice in volcanic clouds

“…There are conflicting views in the literature regarding the effectiveness of volcanic ash as IN, with some investigators concluding that volcanic emissions contain abundant IN [ Hobbs et al , 1971b; Isono and Ikebe , 1960; Isono et al , 1959a, 1959b] and others who suggest the opposite [ Langer et al , 1974; Price and Pales , 1964; Pueschel and Mendonca , 1972; Schnell and Delany , 1976; Schnell et al , 1982]. One difficulty with some of the latter studies relates to an inadequacy in the “membrane filter” measurement technique used, which biases measurements toward an underestimate of IN concentrations [ Hussain and Saunders , 1984].…”

Ice nucleus characteristics of Mount St. Helens effluents

“…Active volcanoes have been suggested as being sources of atmospheric ice nuclei (IN) [Isono et al, 1959;Hobbs et al, 1971;Tanaka, 1980], the relatively rare aerosol particles that are thought to initiate much of the Earth's precipitation. Other researchers have indicated that at least some active volcanoes are not releasing IN to the atmosphere [Price and Pales, 1964;Pueschel and Mendonca, 1972;Schnell and Delaney, 1976].…”