JAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
  
(Amreli) 
63 aat T € — n 
1 (slope =-40.384) | 
  
0.701 02-03 04-05 
NDVI 
50 (slope =-28.3010 | 
  
Figure 1: A scatterogram between LST and NDVI 
on 15 january 1999 
that high NDVI was associated with low LST over more 
densely vegetated areas(Kheda and Banaskantha), generally 
during the peak growing season (i.e January ) as compared to 
sparsely vegetated area (Amreli and Rajkot). Greater scatter 
and steeper slopes was also observed for Amreli and Rajokt 
than Kheda and Banaskantha districts. These differences in 
slope were related to vegetation physiological control as the 
partitioning of net radiation into latent heat and sensible heat 
fluxes with steeper slopes for the sites with reduced soil 
moisture and vegetation amount. The small differences in LST 
at large NDVI (i.e >0.3) between densely vegetated areas 
(Kheda and Banaskantha) could be attributed to variation in 
LST being causefl by factors such as spatially variable 
meteorological conditions, physiological and architectural 
differences in the plants and the variations in the terrain 
resulting in site to site differences in insolation. 
The AVHRR-LAC derived LST versus NDVI relationship for 
four dates in 1998-99 (figure 2) that characterize most of the 
variability through the growing seasons of mustard, the 
dominant crop of Banaskantha district. Differences between 
slope of regression may be ascribed to soil moisture and 
vegetational evaporative fraction, with the steeper slope during 
mid growth stages (i.e January 15 (slope=-31.019)) and 
(February 18 (Slope=-28.301)) and shallowest slope during 
early (December 15(Slope=-37.061)) and late (March 17 
(Slope=-43.517)) stages. The regression lines for all four dates 
converged as the NDVI approached a value of 0.4. Nemani and 
(Rajkot) 
  
(sope = -36.941) 
  
  
  
  
0 01---02-<0:3-—-04-—05 
NDVI 
(slope z -43.517) 
LST(C) 
  
0 0.1 0.2 03 04 05 
Figure 2 : A scatterogarm between LST and NDVI for 
Banaskantha Distric (a)15 Dec, 1998, (b) 15 Jan., 1999, 
( c) 18 Feb., 199 (d) 17 Mar., 1999 
Running (1989) observed a similar phenomenon and found that 
the Ts-NDVI regressions calculated for two different dates over 
a conifer stand had different slope but converged as the NDVI 
approached the maximum observed value. The spread of 
scatterogram also observed to increase with progress of crop 
growth and fractional vegetation cover. Greater scatter was 
noticed during the early and late growing stages of rabi crop 
growing season of mustard in Banaskantha. 
4.3 Validations of surface meteorological parameters 
Validation of surface land surface land temperatures derived 
from the satellite data was done using in-situ measurements of 
soil temperatures (5,10 and 20 cm depth) at 14.30h IST from 
three agro meteorological stations, over dates of satellite 
overpass. These soil temperatures were extrapolated to obtain 
the soil surface temperatures using statistical regression model. 
The comparison of observed satellite temperature and satellite 
retrieved surface temperature is shown in table 2. A good 
agreement was observed between satellite retrieved surface 
temperature and with ground estimates of mid-day surface soil 
temperatures. Satellite retrieved surface temperatures matching 
with observed soil surface temperatures within 0.0 to 1.7°C, 0.2 
to 2.1°C and 0.2 to 2.3°C for S.K.Nagar, Narsari and Godhara, 
respectively. This shows that average bias in retrieved surface 
temperature compared with observed surface soil temperature is 
approximately 2°C or less over three meteorological stations for 
all dates. Figure 3 shows 
Table 2 :Comparison of satellite derived surface temperature with observed surface soil temperatures (14.30 IST) 
  
  
  
  
  
  
  
  
  
  
  
  
December 31, 1998 January 15, 1999 February 18, 1999 March 17, 1999 
Met. Station 
Retrieved Observed Retrieved Observed Retrieved Observed Retrieved Observed 
(°C) (°C) (°C) (C) (CC) °C) CC) (°C) 
Godhara 30.23 30.0 32.5 30.2 37.6 36.4 41.7 43.0 
Navsari 32.2 NA 30.1 28.0 36.6 35.0 38.8 39.0 
SK Nagar 30.7 30.7 31.8 30.1 36.2 35.2 41.9 41.6 
  
  
  
  
NA: Observed data not available 
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