A New Version of Hydrometeor Videosonde for Cirrus Cloud Observations

Abstract

A new version of hydrometeor videosonde (HYVIS) has been developed to measure the vertical distribution of hydrometeors in cirrus clouds with low ice crystal concentrations. This sonde has two small video cameras that take pictures of particles from 7 pm to 5 mm in size, and transmits particle images by 1.6 GHz microwave to a ground station. The original HYVIS did not have enough sampling volume to evaluate the size distribution of hydrometeors in clouds with low number concentrations. To increase sampling volume, a small suction fan was added. From laboratory experiments, we have estimated the variation in sampling volume with changes of ambient air pressure and ascent velocity of the sonde. Theoretical calculation showed that the collection efficiency of the new HYVIS should be unity for all ice crystals larger than 10um.Some examples of cirrus cloud observations have demonstrated that the new HYVIS enabled us to determine reliable size distributions of ice crystals larger than 10um at 250m intervals. The results of the new HYVIS measurements provide us with useful information about mechanisms for the formation and maintenance of cirrus clouds.

Radiative Properties of Mid-latitude Frontal Ice-Clouds Observed by the Shortwave and Longwave Radiometer-Sondes

“…By a synergetic use of the wind-profiler and a YAG lidar in the JACCS cirrus experiment, Kobayashi et al (1999) have developed a technique to detect ice-cloud structures. Another newly added device was a combined-sonde scheme: we have developed a sonde observing scheme by combining a shortwave (SW) and longwave (LW) radiometer-sonde (Asano et al 2004) and an improved hydrometeor-video-sonde (Orikasa and Murakami 1997), both of which were developed at MRI. Although no direct aircraft measurement was available in the experiment, the combined-sonde observing scheme could simultaneously measure height distributions of cloud microphysical properties and radiative fluxes as well as temperature and humidity (Asano et al 1997).…”

“…The former HYVIS was improved to get a better image resolution and a larger sampling volume in tenuous ice-clouds (Orikasa and Murakami 1997). The reformed HYVIS has two (microscopic and close-up) micro-video-cameras with different magnifications, and it can take images of ice-particles larger than 10 mm up to 1 mm by the two cameras in a 10-second cycle.…”

“…In order to increase the sampling volume, the HYVIS has a small suction fan that forces hydrometeors to fall on the sampling film through the particle inlet. The detailed structure and performance of the improved HYVIS have been discussed by Orikasa and Murakami (1997). In order to obtain smoothed vertical profiles of icecrystal size distributions, we averaged the HYVIS size distribution data over every 250 mthick cloud layer, and the empirical equations proposed by Davis (1974) and Mitchell et al (1996) were used to calculate mass and projected-area size distributions, respectively.…”

“…Unfortunately, however, no direct aircraft measurement was available in the JACCS cirrus experiment. In order to simultaneously measure vertical distributions of the cloud microphysical properties and radiative properties in high-level ice-clouds from the ground, we have developed a sonde observing scheme by connecting a hydrometeor-video-sonde (Orikasa and Murakami 1997) and a shortwave and longwave radiometer-sonde (Asano et al 2004) in series to a balloon. Although observations by high-altitude research aircraft have advantages in higher measurement accuracy and horizontal resolution, but they have drawbacks such as expensive cost with less operational flexibility and coarse vertical resolution.…”

Ground-Based Cirrus Observation

“…Therefore, we cannot draw a definitive conclusion that the above results are typical characteristics of cirrostratus associated with the stationary Bai-u fronts. In order to measure more accurate size distribution, the improvement of the HYVIS has been continued (Orikasa and Murakami, 1997) and it is necessary to accumulate the observation results.…”