MODIS image products were used to examine dust and sand storms occurred in Tarim Basin and identify major land cover types that may have contributed most to the recent severe dust storms. The near daily global coverage and multispectral capability of the MODIS sensors have made MODIS image products one of the best satellite observation data sources for monitoring large-scale Earth surface features and phenomena. The Level 1-B granule image quicklooks provided by the MODIS Atmosphere Science Team have proved sufficient for tracking dust storms in Tarim Basin. Within the last twenty-two months, Tarim Basin was covered by different scales of dust or sand storms almost year round. However, the basin-wide dust or sand storms were rare and they occurred mostly in March and April, when soil surface protection is the poorest and wind speed is the highest. As indicated by the compiled image quicklooks series, all dusts and sands were derived from within the basin. Once suspended in the air they were confined to the basin by the high mountains bordering the Basin. Only a relative small amount of dusts were exported to the east when they were associated with strong cold frontal systems. Analysis on the land cover type maps derived from full-resolution and cloud free MODIS Level 1-B radiance images suggest that the former Tarim River delta complex and current and past fluvial plains are the newest additions to the source areas of dust and sands. These two land cover types deserve the highest priority in the restoration of desert ecosystems effects in the region.
Remote Sensing data acquired by various sensors during the last 40 years for the Turfan Basin in northwest China were compiled and processed to map and monitor changes of surface features related to hydrological conditions within the basin. Various image processing techniques were used to map surface features directly or indirectly related to former lake levels and groundwater tables for inferring conditions of the past climate. Special attention has been paid to the distribution of open water body, playa salt crust, waterlogged and salinized soils, and desert vegetation. With improved spatial resolution and more spectral bands, data acquired by ASTER sensor were explored to get additional information for discriminating these surface features. The compiled data indicate that Aiding Lake was a seasonal lake as early as in 1961. For the last 40 years, Aiding Lake has existed as a lake with open water only during the spring and early summer months. The size of the lake water body and timing and duration of the lake phase have varied year to year, suggesting that Aiding Lake is highly sensitive to climatic fluctuations and it is an ideal location for detecting possible impacts of global climatic changes.
The varying fire frequency in the Santa Monica Mountains provides unique opportunities for examining the impacts of disturbance and succession on community composition and ecosystem function at the landscape scale. Fire resets the 'successional clock' of this evergreen-dominated ecosystem and favors early successional annuals that tend to have higher photosynthetic rates and leaf transpiration rates than mature, long-lived woody perennials. Hyperspectral sensors like the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) offer promising opportunities for remotely detecting these dynamic physiological properties in changing landscapes. Specifically, we expect altered photochemical reflectance index (PRI) and water band index (WBI) values for stands in early succession following fire. PRI and WBI from Santa Monica Mountains AVIRIS imagery indeed show complex patterns varying with season and successional state, possibly revealing varying photosynthetic activity in these dynamic, fire-prone landscapes. Further work is attempting to also consider the impact of changing canopy structure and vegetation type on physiological properties detectable with hyperspectral imagery.
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