Ground-based measurements of land surface temperature as measured by Platinum resistance thermometer partly buried in the soil surface radiation temperature measured by infrared thermometer and near surface air temperature measurements at Gaize (32.30°N 84.06°E 4420 m) on the western Tibetan Plateau from January 2001 to December 2003 were compared with Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) products (Version 4) produced by the generalized split-window (MOD11A1) and the day/night LST algorithm (MOD11B1). A comparison of LSTs shows that the LSTs produced by the day/night LST algorithm agree quite well with ground-based surface temperature and surface radiation temperature measurements with a mean difference of zero and root mean square errors being less than 1 K. MODIS LST retrieved by the day/night LST algorithm is found to be 2.2 K less than the air temperature at 0. 5 m above the surface. Compared to that produced by the day/night LST algorithm the LST produced by the generalized spit-window LST algorithm is underestimated by 1.9 K.
The global land-surface temperature (LST) and normalized difference vegetation index (NDVI) products retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) data in 2001 were used in this study. The yearly peak values of NDVI data at 5km grids were used to define six NDVI peak zones from -0.2 to 1 in steps of 0.2, and the monthly NDVI values at each grid were sorted in decreasing order, resulting in 12 layers of NDVI images for each of the NDVI peak zones. The mean and standard deviation of daytime LSTs and day-night LST differences at the grids corresponding to the first layer of NDVI images characterize the thermal status of terrestrial ecosystems in the NDVI peak zones. For the ecosystems in the 0.8-1 NDVI peak zone, daytime LSTs distribute from 0-35 °C and day-night LST differences distribute from -2 to 22 °C. The daytime LSTs and day-night LST differences corresponding to the remaining layers of NDVI images show that the growth of vegetation is limited at low and high LSTs. LSTs and NDVI may be used to monitor photosynthetic activity and drought, as shown in their applications to a flood-irrigated grassland in California and an unirrigated grassland in Nevada.
12 MODIS (Moderate Resolution Imaging Spectroradiometer) was launched on board the NASA's Terra Earth Observing System (EOS AM-1) Satellite on December 18, 1999. We propose in this work operative split-window algorithms for retrieving sea surface temperature (SST) and land surface temperature (LST) using MODIS data. In order to attain our goal, the MODTRAN 3.5 radiative transfer code was used to predict radiances for MODIS channels 31 and 32. To analyze atmospheric effects, a set of radiosoundings was used to cover the variability of surface temperature and water vapor concentration on a worldwide scale. These simulated data were split into two sets which have very similar distributions in space and time. The first one was used to fit the coefficients of the algorithms for retrieving both SST and LST, while the second one was used to test the fitted coefficients. Later, a sensibility study, including the effects of noise, emissivity and water vapor content uncertainties, has been done using the error theory.
The greatly reduced stratospheric ozone concentrations over the Antarctic continent (popularly known as the Antarctic ozone hole), the consequent increase in short wavelength ultraviolet radiation (UVB), and the influence of this increased UVB on the Antarctic ecosystem has led to the development of new instruments for the measurement of these effects. One instrument, arguably a compromise between a more complex and expensive full spectral narrow-band instrument and a simpler broad-band instrument, is manufactured by Biospherical Instruments (BSI) for the measurement of surface and in-water UV radiation. Here we present preliminary results of direct observations of springtime UVB, using the BSI PUV-510, under the Antarctic ozone hole and provide an algorithm, using the radiative transfer code of Wan, for the accurate estimation of column ozone based upon these measurements. We show that data from the PUV-510 can be used to estimate column ozone, given a rough estimate of surface albedo, to within an accuracy of +/- 10 DU and that this algorithm is robust, working well for both clear and cloudy skies.