the u! 
APPLICATION OF THE AERIAL REMOTE SENSING IN THE STUDY ON LAND its u 
ROUNGHNESS AND DIFFUSION MODEL IN SHANGHAI multi: 
ence 
Wang Zhi Sheng the 
under 
( Shanghai Normal University, Shanghai, Chnia ) betwe 
time, 
atmos 
Abstract tatio 
Land roughness is the main factor causing the diffusion of mechanical turbulence 
near the ground surface, the main conclusions of which are obtained via the 
interpretation of the Shanghai colour infrared aerial maps with 1:5000 and by the where 
numerical calculation method: first, the land roughness from 0 to 1 metre under ©: 
different wind directions occupies an absolute dominant position in Shanghai, 
while the average land roughness greater than 5 metres is less than 9%; secondly, Gi: 
the regional distribution of vertical turbulent diffusion in Shanghai can be 
divided into five scales from A to E. Notwithstanding the directions of the wind, The a 
diffusion conditions in the city proper are all less than or equal to level B. effic 
The diffusion model in the form of discontinuous polygonal frame under the north 
or south wind directions can match the distribution of the pollutant concentration 
very well. 
Key words: Remote Sensing Application, Image Interpretation, Roughness length. 
  
  
  
t where 
Foreword lowing experimental formula during his Hi : 
solving the urban roughness in 1970: 
Deducing and predicting the concentration Zi: 
distribution of urban atmospheric pollu- =i HS «> 
tion may design many kinds of diffusion ZA Zo: 
models; in each diffusion model, the diff- 
usion parameter value 6 is a parameter where,H: the height ( metre ) of obstacle : 6 : 
which is more sensitive to concentration met by the air stream; i-1,: 
distribution.Because of the close relation a: lateral area (m^) of the obstacle . point 
of the atmospheric pollution diffusion met by the air stream; augme 
rate with the index of wind speed profile, A: the covered area ( m? ) of the cript 
the latter is strongly influenced by atmo- obstacle. (83:3 
spheric stability and the properties of For one city, the obstacles met by the air rough 
underlying surface (i.e. land roughnees ). stream,i.e. different types of buildings, 0.03; 
Therefore, the value G should be the com- and building complex with different mesh 
prehensive index of various kinds of shapes, while the different size of build- value 
differences for atmospheric stability and ing density and the location azimuth of funct 
underlying surface.  Pasquill's P-G curve the buildings can affect directly the ing | 
method is always used as its traditional diffusion rate of the pollutants under a the C 
method of ditermination. But, this method certain prevailing wind direction in diffe 
is obtained by test under the conditions general, thus, according to Lettau's cacu- its 
that underlying surface of the land lating formula, the following three kinds Tabl: 
surface in the plains is more single. The of caculating formula under the different of bi 
condition errors used for the urban  com- conditions have been deduced and derived. the : 
plicated underlying surface are obviously type 
great. After taking the geometric paramet- a.When the prevailing wind direction is aver: 
ers reflecting the land roughnees from vertical with the azimuth of building: mesh 
the image source and forming a data base a (con: 
via the interpretation of the aerial maps 7 LH: 2) whicl 
for the color infrared images in Shanghai 2 s over 
and according to the geographic coded mesh b.When the prevailing wind direction is of à 
points, and in terms of numerical calcula- paralleled with the azimuth of building: laye 
tion method, the value Z of roughness 2 
under the different prevailing wind direc- Xr H 43) — 
tions is quantitatively derived. After 2 L S 
correcting by augmentation coefficient c.When the prevailing wind direction is 
method, and finally, the value 6 -- the oblique with the azimuth of building: = 
diffusion parameter -- for determining 27 
atmospheric diffusion capacity is obtained, = dt. (4) 
while the structure of special distribu- 2 S 
tion of vertical diffusion parameter 6; in In the formula mentioned above, 
Shanghai can be simulated by "land surface H: the covered height of the building; Tabl 
source" and "overhead source". area of the building covered; 
S: 
L: length of building: 
y 
L 
=/ L + ASA) 
2. Augmentation coefficient 7 : Due to the 
  
I. Method & Principle 
  
  
l. Z--land surface roughness: one physical complexity of environmental conditions,the 
quantity of air turbulence of underlying atmospheric diffusion model, established 
surface, caused by being rough surface, and obtained by stable and uniform turbu- 
can be measured to some extents by land lent field in the region of plains, has no Tabl 
roughness.H. H. Lettau applied the  fol- universal significance. Especially, for