Progress of Meteorological Instrumentat ion in India* J" S. )L\T IlUH Lid ia .1Leteurul /J/ j icul [A'j HITI/ll e/lI , S c,c lJelhi (R<' cd ml 2V JUlluar!J 100:) t. Introduction J. l. Perhaps there can be no better prouf uf the proyerb : ' .Necc :-iS ity is the )I ot her of Invention ' than the of met eorulogi - cal instrumentation in the India )!etcorolngical Department. \rith the growing need for meteoro- logical data for various scientific disciplines and other applied fields, it became necessary to extend ourmeteorologicalobserving net-workon a. country- wide ha. .'-s iN and ahlU equip our obscrvntorics with more and more tmphiliticu tCtl instruments . In tho context uf limited flnauciul resourccs, particnla.rly ill terms of foreign exchange, there was 110 ot her a ltcrnntivo but to take up the mrul1lfa ct uw of in- st r uments in Hi e dcpurtmeut itself. A stnr t. wns made first in tho early thirt ies of thi scentury by setting up two smnll repairand maintellance units at Agra and in regard to upper air and surface meteorological in struments respective ly. In course of time these t wo small units hccarne th e cent res of design, devel opment and prOl luction of routin e meteorological instruments. 1·2. By 1938, tho workshop organisation at .Agra became a fairly well est a blished manufac- turingunit. aud sta rted product ion of self-recording meteorcgr sphs and ot her simple meteorological instruments, far the exp loration of the upper atmosphere from a few selected stat ions in India. Similarly, the meteorological workshop at Poona started manufacturing tho routine surface meteo- rological instruments, such as, raingsuges and nnemometers. In the year 1911, th e workshop at AgTl\ \\0\5 moved to tho now site of the Upper Air Office at New Delhi. Pro gress was made here on tho development of a suirable radiosonde for Indian conditi ons, which could be easily fabricated from components and mat erials locally available and emplo ying a simple technique so that tho the n nvuiluble scient ific staff could handle the ins truments without much difficulty. III order to expedite the development of S IlC] , an instrument, tho t. wo unit s at NeW' Delhi and Poena were encouraged to evolve a. suitable radioscude 011 a hl\. 'ii lol. This proved to he :\ vcry -Presented at tho UNESCO Seminar on " Iasrrumcnentlou" (CSIO) and held at Chandlgarh from 12 to 16 November 1961 crhca ciou s method for t he quick dcvvlojnueut of thc in s trumen t. By 19 -1':.! , both the centres evolved two different t)1 )(':8 of radiosondes one using a clock-work called the e-Type Radiosonde and tho other using a fan called the F-Typo Radoisoudc. 1-3 Dur ing World War ll , need arose for getting upper air temperature and humidity (bta from a number of sturious in India ami these two cent res helped in setting Ill' 13 to 1-1 radiosonde stations within a. few ycal'ij . The two types of rudioaoudo instruments UfC still in use at sixteen stations in India. These are, however, 011 the verge of ro- placcmmcnt by nudio-frequeucy modulated rad io- sondea in which the meteorological parnmcters chan ge the electrical proI,erty of th e sensor which is made to frequency-modulate an nudio signal. Tho exte nt of audio-mo dulation determines die value of meteorological parameter in quest ion. This development also came 1 \S a matter cf nc- cessity , Thoprevious sondes were of the mechnni- cal nnd t herefure. subject tu errors due to zero- shift, and hysteresis. These Ronde' placed serious limitations 011 t he accuracy of measurement and the maximum height of observation. TIll' advent of jet. aircraft.in tho post-war period aml suporsonio aircraft of the fu ture have made th e need far more pressing for probing the atmosphere to \'cry lligh levels. A progr i.unme of rcorg.lnising and expand- ing our workshops has been made to meet tho needs of the time. 1, ·1. Besides the production of the convcu tion al meteorological instruments both for surface allli upper air observations, tho department a lso pro- duces a very large number of specialised ins tru- ment s in t he field of geoph)'sic.., agr icul tural meteorology and other allied branches. In the subsequ ent paragraphs a brief accuunt i t! given of some of th ese instruments. 2. Departmental Workshops Each oue of the work shops at Now Doll'; allll three main divi sions, dz ., (1) Machiuo- shop, (II) Assembly-shop and (iii) Design and Development-shop_ organised by Central Scien ti flc Instrumc ete Organisation