Thunderstorm Anvil Research Articles

Properties of Cirrus Generating Cells

Particle size spectra were measured during 20 hr of sampling in cirrus generating cells (uncinus, stratus, spissatus, thunderstorm anvil) and the particle concentration, mean crystal length, ice water content, reflectivity factor, and precipitation rate were calculated from these spectra. Average values of the physical properties in the generating cells were: Ice crystal concentration: 10,000–25,000m−3 Mean crystal length: 0.6–1.0 mm Particle habit: bullet, rosette, column (75%)-plate (25%) Ice crystal density. 0.6–0.9 gm m−3 Ice water content. 0.15–0.25 gm −3 Reflectivity factor: 5.0–20.0 mm6−3 Precipitation rate. 0.5–0.7 mm hr−1 Growth was found to be downward, reaching a maximum ice water content just below the base of the generating cell. The maximum ice water contents (not including the thunderstorm anvil) were found in cirrus uncinus. Liquid water was not found throughout the cirrus sampling by measurement with the Johnson-Williams hot wire liquid water meter; however, we believe that liquid water is present as a transient phase.

The use of cumulonimbus anvil growth data for inferences about the circulation in thunderstorms and severe local storms

The cumulonimbus anvil, studied by means of geosynchronous satellite, is used to reveal the circulation characteristics of local storms. Data is given for volume flux and divergence at the top of the storm, and these are compared with previous results by other investigators. Agreement is good, suggesting that satellite study of local storms is both useful and reliable. In regard to thunderstorm anvil outflow, a simple model of a point source in a uniform stream is shown to be a good approximation to observed anvil growth. Some evidence suggesting the interaction of proximate local storms with one another and with the environmental wind shear is presented. DOI: 10.1111/j.2153-3490.1972.tb01558.x

Mapping a Thunderstorm Anvil Flow by Doppler Radar

Abstract The mean motion of particles in a thunderstorm anvil has been measured at various heights and elevation angles by Doppler radar, using the velocity-azimuth scanning mode of Lhermitte and Atlas with the harmonic analysis scheme of Browning and Wexler. An error analysis indicated that the measurement accuracy, even at elevation angles as high as 80°, is comparable to the inherent radar resolution of 0.9° in direction and 0.6 m sec−1 in speed. The scale of temporal and spatial variability of wind at anvil height was more than an order of magnitude greater than the errors; consequently, the measurements of anvil winds obtained by Doppler radar are considered to be significantly informative. Estimates of divergence, on the other hand, were quite unreliable at elevation angles >50° and not especially trustworthy at any of the smaller elevation angles. All measurements of divergence, however, showed a trend of increase with greater height in the anvil. Pronounced anomalies in the measured wind component...

Relationships Between the Size of Satellite-Observed Cirrus Shields and the Severity of Thunderstorm Complexes

Seventeen thunderstorm complexes, observed by TIROS satellite over the United States, were investigated. The diameter of the conspicuously bright storm cloud shield, composed of integrated thunderstorm anvils, has been found to be a useful index of severity. Seven out of ten complexes with shield diameters greater than 60 n mi were accompanied by severe local storms. Another, but less reliable, index of severity is the presence of cirrus streamers or “blowoffs.” The line structure, commonly observed by radar, is generally masked by the cirrus shield.