For à trous wavelet-based remote sensing image fusion, it is significant to determine the number of decomposition levels (NDL) to derive the best tradeoff between the spatial and spectral qualities of the fused image. The tradeoff is modeled as a cost function from a novel three-dimensional variational point of view. By solving this cost function, a new fusion scheme is proposed that can be used to customize the tradeoff by weighting the wavelet planes with a factor. The optimal NDL is decided by the intersection of the characteristic curves of the spatial and spectral qualities. Three pairs of remote sensing images are used to test the analysis. The experimental results show that the proposed method provides the practitioner with a reference for selecting the fused image with different spatial and spectral qualities for different applications.
Accurate estimation of evapotranspiration (ET) has long been an important issue in hydrology. Many experimental observations indicate advection has a great impact on ET in arid and semiarid areas. However, most of the remote sensing models only focus on the vertical energy balance and deviate from reality. A revised Penman equation has been derived to estimate actual ET under normal conditions in order to account for advection. The parameter of the water availability for ET is introduced and the T s /f (surface temperature and vegetation fraction) space is used to characterize this parameter in the revised formula. The estimates were validated using the observations measured with eddy covariance systems at the Yingke station. In 22 of all 24 days, the difference between the observations and the estimates was smaller than 70 W/m 2 . The correlation coefficient is 0.91 and the RMSE is 48.38 W/m 2 . This finding reveals that this approach is capable of providing reliable results. In addition, when considering advection, the potential ET can be 83.23 W/m 2 larger than the available energy. This finding indicates that the advection effect needs to be considered in remote sensing models in order to derive more reliable regional ET.
The purpose of this study is to examine the conversions of forests in Northeast China during 1988-2005 by using a 1-km area percentage data model (1-km APDM) with remote sensing data and to find the spatiotemporal characteristics of land conversions between forests and other land uses/covers and internal conversions between forest cover types. Data were derived from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM) images of bands 3, 5, and 4 acquired in 1988, 1995, 2000, and 2005. Research results show that in the period between 1988 and 2005, the forest area in Northeast China underwent dramatic changes, and 4.11 million ha of forest area was aggregately lost because of the conversions of forests to other land uses/covers; at the same time, the forest area also gained 2.00 million ha because of the conversions from other land uses/covers to forests. The results also demonstrate the forest degradation resulting from the conversions between different forest cover types. This research demonstrates the feasibility and importance of using the 1-km APDM at a finer resolution to trace the spatiotemporal patterns of the forest conversions.
To meet future earth system science challenges, NASA will develop constellations of smart satellites in sensor web
configurations that provide timely on-demand data and analysis to users, and that be reconfigured based on the changing
needs of science and available technology. Sensor webs can eclipse the value of disparate sensor components by
reducing response time and increasing scientific value, especially when integrated with science analysis, data
assimilation, prediction modeling and decision support tools. The prototype Land Information Sensor Web (LISW) is a
project sponsored by NASA, trying to integrate the Land Information System (LIS) in a sensor web framework which
allows for optimal 2-way information flow that enhances land surface modeling using sensor web observations, and in
turn allows sensor web reconfiguration to minimize overall system uncertainty. This prototype is based on a simulated
interactive sensor web, which is then used to exercise and optimize the sensor web - modeling interfaces. These
synthetic experiments provide a controlled environment in which to examine the end-to-end performance of the
prototype, the impact of various design sensor web design trade-offs and the eventual value of sensor webs for particular
prediction or decision support. The Study of virtual Land Information Sensor Web (LISW) is expected to provide some
necessary priori knowledge for designing and deploying the next generation Global Earth Observing System of systems
(GEOSS). In this paper, the progress of the LISW study will be presented, especially in scenario experiment design,
sensor web framework and uncertainties in current land surface modeling.
In this paper we presented a model for calculating CO2 flux in the wheat field based on field simulate test. We adopted crop transpiration as 'information picker' of CO2 flux instead of the potential evaporation and crop water stress index. Another crucial factor is leaf index and air vapor saturation deficit. Experimental coefficient is equal to 1/58. Calculating values have a good agreement with real measurements. The model is useful to estimate regional distribution of CO2 flux.
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