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  • Author or Editor: Bh V. Ramana Murty x
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A. S. Ramachandra Murty
and
Bh V. Ramana Murty

Abstract

In an attempt to investigate conditions under which ice crystals can form at comparatively warm temperatures in supercooled regions of a cloud, the scope of experiments on drop freezing, previously undertaken by the authors, has been enlarged. The results of the present extensive series of experiments have confirmed that supercooling drops, when subjected to evaporation, freeze more readily due to what has been called the “dynamic effect” of evaporation. When sodium sulphate was added to the drops in arbitrary concentration, their freezing probability also showed a significant inctease. These findings indicate that, in supercooled regions of a cloud where prevailing conditions are similar to those of the reported experiments, the ice crystal concentration should be two to three orders of magnitude higher than the existing ice nucleus concentration.

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A. S. Ramachandra Murty
and
Bh V. Ramana Murty

Abstract

No abstract available.

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Bh V. Ramana Murty
,
A. K. Roy
, and
K. R. Biswas

Abstract

The study of echo intensity profile below bright band, when this appears on radar in certain rain situations, has shown that raindrops, after leaving melting level and falling through clouds in warmer layers below do not, as a rule, undergo any noticeable increase in their sizes, suggesting that lower level clouds at this stage have little or no significant liquid water content. The implications of this on the life cycle of rain situations associated with development of bright band are discussed, with reference to a few instances of study, using radar, of such rain at Delhi.

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B. K. Mukherjee
,
K. S. Rao
, and
Bh V. Ramana Murty

Abstract

Computations of vertical motions in the middle atmosphere over the Indian tropical region have been made based on the thermodynamic equation with the geostrophic approximation. The authors have used the once weekly rocketsonde temperature and wind data for the tropical station Thumba India, (8°32′N, 76°52′E) for the four summers (1972, 1973, 1975 and 1976) and two winters (1971 and 1972) which are also years of varying monsoon activity.

In the tropical middle atmosphere, downward motion (subsidence) is the dominant feature when the motion field is considered in a longer time scale. The trend of fluctuations in vertical motion suggests wave structures in the tropical middle atmosphere. The magnitude of the extreme values of the vertical motion in the stratosphere over the high latitudes is larger, by a factor of 2 or more, than those obtained over the low latitudes (tropics). Whereas the magnitude of the vertical motion in high latitudes is associated with stratospheric warmings during winter, the values relating, to low latitudes are computed at 3 h intervals during March.

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A. Mary Selvam
,
G. K. Manohar
,
L. T. Khemani
, and
Bh V. Ramana Murty

Abstract

Simultaneous measurements of raindrop charge, atmospheric electric field and rain intensity were made at Poona using fast response, continuous recording surface instruments during four types of rain: pre-monsoon (thunderstorm rain), monsoon rain type I (tight intermittent rain), monsoon rain type II (heavy continuous rain) and post-monsoon (thunderstorm rain). Measurements were also made of the conductivity of rainwater samples collected during the monsoon season. On some days of this period data on cloud thickness as obtained from the aircraft flights in the region were also available.

The electric field associated with negatively charged raindrops was less negative than that associated with positively charged drops. The raindrop charge spectrum showed different characteristics during the four types of rain studied. It was broadest during the pre-monsoon rain when the convective activity was a maximum. It followed a log-normal distribution during the monsoon rain type I and it was peaked and skewed to the positive side during the monsoon rain type II. Rainwater conductivity was inversely correlated with the cloud vertical thickness. The results of the present study support the warm cloud charge generation mechanism proposed by Takahashi (1974).

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