VIP Call Girls Service Chaitanyapuri Hyderabad Call +91-8250192130
Climatological atmospheric dilution indices
1. IJEP 15 ( 10 ) : 734 - 7 3 8 ( Received on A u g u s t 24, 1995 )
Climatological Atmospheric Dilution Indices over India
D.V. V i s w a n a d h a m , S t u t i M i s h r a a n d A.N.V. Satyanarayana
Banaras Hindu University, Department of Geophysics, Faculty of Science, Varanasi - 2 2 1 0 0 5
A t m o s p h e r i c d i l u t i o n indices ( A D l ) given an idea of the capacity of t h e a t m o s p h e r e to disperse
and dilute the p o l l u t a n t s e m i t t e d i n t o it by m y r i a d sources. The higher the index t h e b e t t e r is the
d i l u t i o n . These indices are c o m p u t e d based on the vertical and h o r i z o n t a l e x t e n t of m i x i n g of t h a
atmosphere by s u i t a b l y devising the s t r u c t u r e of the indices. In the present paper A D l have been
c o m p u t e d on a c l i m o t o l o g i c a l bases for 20 stations spread all over India. W i t h the help of isopleth
analysis the spatial d i s t r i b u t i o n of these indices over India has been s t u d i e d f o r 4 m o n t h , nam-
ely January, April, July and October, w h i c h are t y p i c a l of 4 seasons. The analysis has been ca-
rried o u t t w i c e a day at t h e occurance of m i n i m u m a n d m a x i m u m t e m p e r a t u r e . It is observed t h a t
peninsular India shows relatively higher indices in almost all t h e seasons. The early m o r n i n g A D l
are e x t r e m e l y l o w t h r o u g h o u t the c o u n t r y in all the m o n t h s . A m i n i m u m ADl of 4 is d e s i r a b l e f o r
a s u f f i c i e n t d i l u t i o n w h i c h is absent t h r o u g h o u t the c o u n t r y during morning hours.
INTRODUCTION
There is a growing concern and awareness about
the increasing problems caused by air pollution. Se-
veral episodes of air pollution were known to have
occured under adverse atmospheric conditions, such
as stable atmosphere, low mixing, calm winds, te-
mperature inversions, etc. It is known that disper-
sion and dilution of the pollutants emitted into the
atmosphere are solely governed by the prevailing
meteorological conditions. For an effective enviro-
nmental planning it is rather desirable to have an
idea of the dispersion and dilution capacity of the
atmosphere for any given region or locaiitiy. A sui-
table index clearly defining the dispersive and dil-
utive capacity of the atmosphere would be extreme-
ly useful for general public, the industry and the
policy makers.
To this end, a simple but effective structure of indi-
ces has been developed by the authors closely foll-
owing Holzworth ( 1 9 6 4 ) . The indices are develop-
i
ed based on the extent of vertical and horizontal
mixing of the atmosphere. These indices have been
studied on a seasonal basis over the entire country
and the regions of effective and poor dilution have
been delineated.
MATERIAL
The daily upper data for the months of January, Ap-
ril, July and October typical of winter, pre - mon-
soon and post - monsoon seasons, respectively for
a period of 9 year from 1977 to 1 9 8 5 have been
made use of for the present study, hi addition, the
maximum and minimum temperatures, surface win-
ds have been made use of. The stations for which
data have been collected are Patiala, New Delhi,
Jodhpur, Ahemadabad, Nagpur, Gwaliar, Lucknow,
Gorakhpur, Ranchi, Calcutta, Agartala, Bombay,
Goa, Mangalore, Cochin, Trivendrum, Bangalore,
Hyderabad, Madras and Visakhapatnam.
ATMOSPHERIC DILUTION INDICES (ADl)
These indices have been devised in such a way that
low values correspond to poor dilution capacity and
higher values correspond to better dilution. These
indices are numbered from 1 to /, respectively co-
rresponding to very low, low, low medium, medium,
high medium, high, very high. The criteria for these
indices are based on the mixing heights and wind
speeds. Tables 1 to 3 depict the criteria for obtain-
ing ADl.
M E T H O D O L O G Y
The methods of determination of mixing heights has
been presented in several publications and hence
not attempted here ( Vittal Murty et at., 1 9 8 0 ; Vis-
wanadham and Santosh, 1989; Viswanadham and
Pinakapani, 1994). The minimum and maximum mi-
xing heights have been obtained for the period un-
der study. The surface wind speeds nearer to these
timings have been noted. The ADl are first obtained
based on the mixing heights and then based on w i -
7 3 4 INDIAN J. ENVIRONMENTAL PROTECTION, V O L 15, NO. 10, OCTOBER .1995*
<S> 1695 - Kaip&na C o r p o r a t i o n