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Spatial Analysis of Terrain-Impacted Photosynthetic Active Radiation (PAR) Using MODIS Data

GISCIENCE & REMOTE SENSING 2011年第4期48卷 501-521页

作者： Gao, Zhiqiang Xie, Xiaoping Gao, Wei Chang, Ni-bin Colorado State Univ Nat Resource Ecol Lab USDA UV B Monitoring & Res Program Ft Collins CO 80521 USA Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing 100101 Peoples R China Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA

This paper pres.nts the spatial distribution of photosynthetic active radiation (PAR) using an atmospheric radiative transfer model under terrain impacts. The potential of the model for improved understanding of PAR impacts on ecosystem dynamics is demonstrated with the aid of MODIS (Moderate-res.lution Imaging Spectroradiometer) data, using the Haihe Plain of China as a case study. Various types of MODIS data were aggregated in support of the modeling work at the regional scale. Findings clearly indicate that terrain factors do affect the estimation of instantaneous PAR significantly. Different relationships between PAR and elevation may be classified based on positive correlation, negative correlation, and no correlation. In addition, while there are different relations between PAR and slope, there is no significant correlation between PAR and aspect.

关键词： JTb gene Terrain factors Visible Light Ecosystem dynamics Moderate res.lution Imaging Spectroradiometer photosynthetically active radiation Spatial Analysis

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A coupled remote sensing and the Surface Energy balance with Topography Algorithm (SEbTA) to estimate actual evapotranspiration over heterogeneous terrain

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HYDROLOGY AND EARTH SYSTEM SCIENCES 2011年第1期15卷 119-139页

作者： Gao, Z. Q. Liu, C. S. Gao, W. Chang, N. -b. E China Normal Univ Minist Educ Key Lab Geog Informat Sci Shanghai 200062 Peoples R China Chinese Acad Sci LREIS Inst Geog Sci & Nat Resources Res Beijing Peoples R China Colorado State Univ USDA UV B Monitoring & Res Program Ft Collins CO 80523 USA Colorado State Univ Nat Resource Ecol Lab Ctr Remote Sensing & Modeling Agr Sustainabil Ft Collins CO 80523 USA Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA

Evapotranspiration (ET) may be used as an ecological indicator to addres. the ecosystem complexity. The accurate measurement of ET is of great significance for studying environmental sustainability, global climate changes, and biodiversity. Remote sensing technologies are capable of monitoring both energy and water fluxes on the surface of the Earth. With this advancement, existing models, such as SEbAL, S_SEbI and SEbS, enable us to estimate the regional ET with limited temporal and spatial coverage in the study areas. This paper extends the existing modeling efforts with the inclusion of new components for ET estimation at different temporal and spatial scales under heterogeneous terrain with varying elevations, slopes and aspects. Following a coupled remote sensing and surface energy balance approach, this study emphasizes the structure and function of the Surface Energy balance with Topography Algorithm (SEbTA). With the aid of the elevation and landscape information, such as slope and aspect parameters derived from the digital elevation model (DEM), and the vegetation cover derived from satellite images, the SEbTA can account for the dynamic impacts of heterogeneous terrain and changing land cover with some varying kinetic parameters (i.e., roughness and zero-plane displacement). besides, the dry and wet pixels can be recognized automatically and dynamically in image processing thereby making the SEbTA more sensitive to derive the sensible heat flux for ET estimation. To prove the application potential, the SEbTA was carried out to pres.nt the robust estimates of 24 h solar radiation over time, which leads to the smooth simulation of the ET over seasons in northern China where the regional climate and vegetation cover in different seasons compound the ET calculations. The SEbTA was validated by the measured data at the ground level. During validation, it shows that the consistency index reached 0.92 and the correlation coefficient was 0.87.

关键词： MAGNETIC SURFACES energy balance landscapes Earth surface evapotranspiration, actual Surface energy Vegetation cover remote sensing relative consistency land cover terrains Fault trees

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Moisture availability influences the effect of ultraviolet-b radiation on leaf litter decomposition

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GLObAL CHANGE bIOLOGY 2010年第1期16卷 484-495页

作者： Smith, W. Kolby Gao, Wei Steltzer, Heidi Wallenstein, Matthew D. Tree, Roger Colorado State Univ USDA Nat Resource Ecol Lab UV B Monitoring & Res ProgramDept 1499 Ft Collins CO 80521 USA

Altered surface ultraviolet-b (uv-b) radiation res.lting from a combination of factors that include changes in stratospheric ozone concentrations, cloud cover, and aerosol conditions may affect litter decomposition and, thus, terres.rial nutrient cycling on a global scale. Although litter decomposition rates vary across biomes, patterns of decomposition suggest that uv-b radiation accelerates litter decay in xeric environments where precipitation is infrequent. However, under more frequent precipitation regimes where litter decay rates are characteristically high, the effect of uv-b radiation on litter decomposition has not been fully elucidated. To evaluate this association between moisture regime and uv-b exposure, a litter decomposition experiment was designed for aspen (Populus tremuloides) leaf litter, where conditions that influence both abiotic (photodegradation) and biotic (microbial) processes could be manipulated quantitatively. We found that experimentally increasing uv-b exposure (0, 7.4, and 11.2 kJ m(-2) day(-1), res.ectively) did not consistently increase litter decomposition rates across simulated precipitation frequencies of 4, 12, and 24 days. Instead, a uv-b exposure of 11.2 kJ m(-2) day(-1) res.lted in a 13% decrease in decomposition rates under the 4-day precipitation frequency, but an increase of 80% under the 24-day frequency. Furthermore, the same uv-b dose increased litter decomposition rates under the 24-day precipitation frequency by 78% even in conditions where microbial activity was suppres.ed. Therefore, under more xeric conditions, greater exposure to uv-b radiation increased decomposition rates, pres.mably through photodegradation. In contrast, when decomposition was not moisture-limited, greater uv-b exposure slowed decomposition rates, most likely from the res.lting inhibition of microbial activity. Ultimately, these experimental res.lts highlight uv-b radiation as a potential driver of decomposition, as well as indicate that both t

关键词： aspen litter climate change decomposition photodegradation ultraviolet-b ultraviolet radiation uv-b

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Retrieval of columnar water vapor using multispectral radiometer measurements over northern China

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JOURNAL OF APPLIED REMOTE SENSING 2011年第1期5卷 053558-053558页

作者： Liu, Chaoshun Li, Yun Gao, Wei Shi, Runhe bai, Kaixu E China Normal Univ Minist Educ Key Lab Geog Informat Sci Shanghai 200062 Peoples R China CAS Joint Lab Environm Remote Sensing & Data Assimila ECNU & CEODE Shanghai 200062 Peoples R China China Meteorol Adm Natl Satellite Meteorol Ctr Beijing 100081 Peoples R China Colorado State Univ USDA UV B Monitoring & Res Program Ft Collins CO 80521 USA Ctr Remote Sensing & Modeling Agr Sustainabil Ft Collins CO 80521 USA

Water vapor is an important component in hydrological processes that basically involve all types of seasons, including dry (e.g., drought) or wet (e.g., hurricane or monsoon). This study retrieved columnar water vapor (CWV) with the 939.3 nm band of a multifilter rotating shadowband radiometer (MFRSR) using the modified Langley technique. Such an investigation was in concert with the use of the atmospheric transmission model MODTRAN for determining the instrument coefficients required for CWV estimation. res.lts of the retrieval of CWV by MFRSR from September 23, 2004 to June 20, 2005 at the XiangHe site are pres.nted and analyzed in this paper. To improve the credibility, the MFRSR res.lts were compared with those obtained from the AErosol RObotic NETwork CIMEL sun-photometer measurements, co-located at the XiangHe site, and the moderate res.lution imaging spectroradiometer (MODIS) near-infrared total precipitable water product (MOD05), res.ectively. These comparisons show good agreement in terms of correlation coefficients, slopes, and offsets, revealing that the accuracy of CWV estimation using the MFRSR instrument is reliable and suitable for extended studies in northern China. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI:10.1117/1.3647483]

关键词： multifilter rotating shadowband radiometer columnar water vapor retrieval, moderate res.lution imaging spectroradiometer AErosol RObotic NETwork

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Detection of Multidecadal Changes in uvb and Total Ozone Concentrations over the Continental US with NASA TOMS Data and usda Ground-based Measurements

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REMOTE SENSING 2010年第1期2卷 262-277页

作者： Gao, Zhiqiang Gao, Wei Chang, Ni-bin Colorado State Univ USDA UV B Monitoring & Res Program Nat Resource Ecol Lab Ft Collins CO 80525 USA Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing 100101 Peoples R China Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA

Thinning of the atmospheric ozone layer leads to elevated levels of Ultraviolet-b (uvb) at the Earth's surface, res.lting in an increase of health risks to living organisms due to DNA damage. This paper examines the multidecadal changes of total column ozone from 1979 to 2005 with the aid of ground-based uvb stations using the ultraviolet multifilter rotating shadow-band radiometer (uv-MFRSR). For the purpose of demonstration, four usda ground stations, WA01, CO01, MD01, and AZ01, were selected for detailed comparisons against the satellite data. The major finding of this study is that over the course of the time series, on a monthly scale, the uv index (uvI) has increased at the four selected usda stations while total ozone has decreased in the continental USA over the past three decades and spatial distributions of uvI and total ozone have shown substantial variations from coastal zones to the Midwest Regions of the USA, yet the tendency toward recovery of ozone layer in the continental USA cannot be fully confirmed. This leads to a conclusion that the uvI changes might have been influenced by other factors in addition to the total ozone in the atmospheric environment across at least 76% of the continental USA.

关键词： uvb total ozone Nimbus-7/TOMS spatial analysis

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Skin cancer incidence is highly associated with ultraviolet-b radiation history

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INTERNATIONAL JOURNAL OF HYGIENE AND ENVIRONMENTAL HEALTH 2010年第5期213卷 359-368页

作者： Chang, Ni-bin Feng, Rui Gao, Zhiqiang Gao, Wei Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA Univ Penn Dept Biostat & Epidemiol Philadelphia PA 19104 USA Colorado State Univ Nat Resource Ecol Lab USDA UV B Monitoring & Res Program Ft Collins CO 80523 USA Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing Peoples R China

Recently, the increased amount of ultraviolet-b (uv-b) exposure due to ozone depletion has been found to be associated with increased incidence of skin cancer across the world. The quantification of individual, regional, and historical uv exposure directly affects establishment of the association between skin cancer and uv exposure, but accurate assessment and measurement have been challenging for decades. As a sequence, cumulative studies using different metrics reported conflicting res.lts on whether uv radiation, including sunburns, early childhood sun exposure, and chronic exposure, increases melanoma risk. This paper aims to establish the relationship between uv-b and melanoma incidence across the continental U.S. using an ecological approach that incorporate more accurate uv-b exposure measured by the National Aeronautical and Space Administration Nimbus-7 total ozone mapping spectrometer, and the United State Department of Agriculture ground-based network. Using statistical linear mixed models, we found strong positive associations between the skin cancer and the past uv exposure or the past cumulative 3-year uv exposure 3 or 4 years ago. uv has regional distributions and its regional effects on the skin cancer incidence are still significant after adjusting the effect of uv exposure. res.arch findings yield deepened understanding of spatiotemporal distribution of melanoma incidence rates and a greater appreciation for the complexity and heterogeneity of melanoma risk factors especially the uv-b exposure at different temporal and spatial scales. (C) 2010 Elsevier GmbH. All rights res.rved.

关键词： uv-b uv exposure Skin cancer incidence Skin cancer risk Melanoma risk Satellite data Nimbus-7/TOMS Regional variation Spatiotemporal analysis Environmental health

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Application of MODIS time series data for drought assessment in the East China

Application of MODIS time series data for drought assessment...

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Conference on Remote Sensing and Modeling of Ecosystems for Sustainability VII

作者： Liu, Chaoshun Shi, Runhe Gao, Wei Gao, Zhiqiang East China Normal Univ Key Lab Geoinformat Sci Minist Educ Shanghai 200062 Peoples R China ECNU Joint Lab Environm Remote Sensing & Data Assimila Shanghai 200062 Peoples R China CEODE Shanghai 200062 Peoples R China Colorado State Univ Nat Resource Ecol Lab USDA UV B Monitoring & Res Program Ft Collins CO 80523 USA Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing 100101 Peoples R China

ISBN: (纸本)9780819483058

Drought is one of the major environmental disasters in China, so it is very important to detect and monitor drought periodically at large scale for decision making. This study focuses on combining information from visible, near infrared, and short wave infrared channels of MODIS to improve sensitivity to drought severity. Significant correlations have been found between NDVI/NMDI values and precipitation/soil moisture data in individual stations. It was confirmed that both NDVI and NMDI indices could be used to monitor drought in the study area at a regional scale. However, NMDI had a slightly higher correlation with soil moisture or precipitation than NDVI, which suggests that NMDI variations can be a good indicator of water changes and in turn, the drought conditions in individual stations in the study area. res.lts from analysis of time series NDVI and NDWI data over the study area also indicate that NMDI was more sensitive than NDVI to drought conditions. Future efforts are being need to more fully exploit the potential of NMDI as an active drought-monitoring tool for different geographic regions, climates, and multiple spatial scales.

关键词： drought NMDI NDVI MODIS soil moisture

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Comparative analyses of the ultraviolet-b flux over the continental United State based on the NASA total ozone mapping spectrometer data and usda ground-based measurements

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JOURNAL OF APPLIED REMOTE SENSING 2010年第1期4卷 043547-043547页

作者： Gao, Zhiqiang Gao, Wei Chang, Ni-bin Colorado State Univ USDA UV B Monitoring & Res Program Nat Resource Ecol Lab Ft Collins CO 80525 USA Chinese Acad Sci Inst Geog Sci & Nat Resources Beijing 100101 Peoples R China Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA

In recent years, the risk of health effects caused by the increased exposure to Ultraviolet-b (uvb) due to stratospheric ozone depletion has received wide attention. In the US, there are two ways to accurately measure the uvb. They include: 1) the National Aeronautical and Space Administration (NASA) Nimbus-7 total ozone mapping spectrometer (TOMS), and 2) the United State Department of Agriculture (usda) ground-based network. This paper compares.these two sensors' data for the ultraviolet index (uvI) nationally and regionally to support possible public health, agricultural, and ecological analyses in the future. The major findings of our study are: 1) although there are discrepancies between these two data sets, the temporal correlation coefficients can be as high as 98%. 2) both types of data sources depict the macroscopic spatial pattern of the uvI across the continental US. indicating a strong spatial correlation;3) The two data sources are generally consistent though the uvI of the NASA TOMS data are often about 0.13-1.05 units larger than those of the usda ground-based measurements;and 4) Varying differences can be seen between the Midwest and two coastal regions. While the level of the uvI on the west coast has shown a decreasing trend in the past few years, its counterpart on the east coast showed an opposite trend in between 2000 and 2005. It is hard to conclude that the changes are due to variations of total ozone concentrations in this study period. The usda ground-based measurements may be better applied for time series analysis for public health, ecological, and agricultural applications due to their ability to provide intensive calibrated point measurements.

关键词： uvb changes uvI usda Ground-based Measurements Nimbus-7/TOMS spatiotemporal analysis

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usda uv-b monitoring system: An application of centralized architecture

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COMPUTERS AND ELECTRONICS IN AGRICULTURE 2008年第2期64卷 326-332页

作者： Wang, Xinli Gao, Wei Slusser, Jim R. Davis, John Olson, becky Janssen, Scott Janson, George Durham, bill Tree, Roger Deike, Rita Colorado State Univ USDA UV B Monitoring & Res Program Nat Resource Ecol Lab Ft Collins CO 80523 USA

In order to determine the spatial and temporal variations of solar ultraviolet-b (uv-b) radiation reaching the Earth's surface and their effects on agriculture and environment due to the depletion of atmospheric ozone, the U.S. Department of Agriculture (usda) uv-b monitoring system has been established to provide essential information of ground uv-b levels, along with other variables, to res.arch communities, decision makers, and the public. This monitoring network of 39 sites was designed as a centralized system covering the U.S. domain with collaborating sites in Canada and New Zealand. programmed data loggers and a central data server are employed to automate the work. The centralized architecture allows centrally processing the data from all sites on a 3 min basis and making daily updates available for the users. The system architecture, algorithms for data collection and data flow in the data processing procedures.are pres.nted in this article. Statistics show that the system is rather reliable with an overall data completeness of 98.14% since it began running in 1994. Main damages to the instruments are caused by the static electricity associated with severe thunderstorms, which res.lt in a lower data completeness in summer months than in the others. The drawbacks of the centralized architecture, the possible remedies for the network failures. and our experiences with the system are discussed. (C) 2008 Elsevier b.V. All rights res.rved.

关键词： uv-b radiation monitoring system usda Centralized architecture

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Modeling the land surface heat exchange process with the aid of moderate res.lution imaging spectroradiometer images

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JOURNAL OF APPLIED REMOTE SENSING 2009年第1期3卷 033573-033573页

作者： Gao, Zhiqiang Zhang, Wenjiang Gao, Wei Chang, Ni-bin Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing 100101 Peoples R China Colorado State Univ USDA UV B Monitoring & Res Program Ft Collins CO 80521 USA Colorado State Univ Nat Resource Ecol Lab Ctr Remote Sensing & Modeling Agr Sustainabil Ft Collins CO 80521 USA E China Normal Univ Joint Lab Environm Remote Sensing & Data Assimila Shanghai 200062 Peoples R China Univ Cent Florida Dept Civil Environm & Construct Engn Orlando FL 32816 USA

Most ecosystems and crops experience water stres. in arid and semiarid areas of the Inner Mongolia grassland, Northern China. Yet the lack of long-term in situ monitoring data hinders the managerial capacity of changing water vapor environment, which is tied with sustaining the grassland in the Inner Mongolia. Environmental remote sensing monitoring and modeling may provide synergistic means of observing changes in thermodynamic balance during drought onset at the grassland surface, providing reliable projections accounting for variations and correlations of water vapor and heat fluxes. It is the aim of this paper to pres.nt a series of estimates of latent heat, sensible heat, and net radiation using an innovative first-principle, physics-based model (GEOMOD: GEO-model estimated the land surface heat with MODis data) with the aid of integrated satellite remote sensing and in situ eddy covariance data. based on the energy balance principle and aerodynamics diffusion theory, the GEOMOD model is featured with MODIS (Moderate res.lution Imaging Spectroradiometer) data with 250 m spatial res.lution to collectively reflect the spatial heterogeneity of surface properties, supplement missing data with the neighborhood values across both spatial and temporal domains, estimate the surface roughness height and zero-plane displacement with dynamic look-up table, and implement a fast iterative algorithm to calculate sensible heat. Its analytical framework is designed against overreliance on local micro-meteorological parameters. Practical implementation was assessed in the study area, the Xilin Gol River basin, a typical grassland environment, Northern China. With 179 days of MODIS data in support of modeling, coincident ground-based observations between 2000 and 2006 were selected for model calibration. The findings indicate that GEOMOD performs reasonably well in modeling the land surface heat exchange process, as demonstrated by a case study of Inner Mongolia.

关键词： Ecosystem heat flux MODIS remote sensing

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