ALBERT

Description: Typhoon Talas (2011) caused extensive damage through landslides on the Kii Peninsula, Japan, in September 2011. The purpose of the present study is to quantitatively describe the potential for the occurrence of heavy rainfall-induced disasters if the typhoon track perturbs slightly or the typhoon intensifies. Regarding to the consideration of the track displacement of the typhoon, a procedure is proposed to generate different typhoon tracks perturbed from the original track of the typhoon. In this procedure, the position of a typhoon is artificially shifted at a certain time before landing in a physically consistent manner by applying potential vorticity inversion (PVI) methodology. After relocating the typhoon, the subsequent progress is simulated by a mesoscale meteorological model. Using the output, which consists of a set of realizations having different typhoon tracks, the worst-case scenario is discussed in terms of the soil water index (SWI) of the Kii Peninsula. The SWI is an indicator of the amount of water in soil that represents the hazard of landslide disasters. The maximum spatially averaged SWI is 1.10 times as large as that from the original typhoon track. Regarding the consideration of severer typhoon, the same method is used, but the intensity of the potential vorticity of a typhoon is artificially modified at the position instead of relocating potential vorticity to a different place. The maximum spatially averaged SWI is 1.28 times as large as that of the original typhoon intensity.

Description: Typhoon Talas (2011) caused extensive damage through landslides on the Kii Peninsula, Japan, in September 2011. The purpose of the present study is to quantitatively describe the potential for the occurrence of heavy rainfall-induced disasters if the typhoon track perturbs slightly or the typhoon intensifies. Regarding to the consideration of the track displacement of the typhoon, a procedure is proposed to generate different typhoon tracks perturbed from the original track of the typhoon. In this procedure, the position of a typhoon is artificially shifted at a certain time before landing in a physically consistent manner by applying potential vorticity inversion (PVI) methodology. After relocating the typhoon, the subsequent progress is simulated by a mesoscale meteorological model. Using the output, which consists of a set of realizations having different typhoon tracks, the worst-class scenario is discussed in terms of the soil water index (SWI) of the Kii Peninsula. The SWI is an indicator of the amount of water in soil that represents the hazard of landslide disasters. The maximum spatially averaged SWI is 1.10 times as large as that from the original typhoon track. Regarding the consideration of severer typhoon, the same method is used, but the intensity of the potential vorticity of a typhoon is artificially modified at the position instead of relocating potential vorticity to a different place. The maximum spatially averaged SWI is 1.28 times as large as that of the original typhoon intensity.

Description: As a unique geological and geographical unit, the Tibetan Plateau dramatically impacts the world's environment and especially controls climatic and environmental changes in China, Asia and even in the Northern Hemisphere. Tibetan Plateau, therefore, provides a field laboratory for studying global change. With support from various agencies in the People's Republic of China, a Tibetan Observation and Research Platform (TORP) is now implementing. Firstly the background of the establishment of the TORP, the establishing and monitoring plan of long-term scale (5–10 years) of the TORP has been introduced. Then the preliminary observational analysis results, such as the characteristics of land surface heat fluxes and CO2 flux partitioning (diurnal variation and inter-monthly variation etc.), the characteristics of atmospheric and soil variables, the structure of the Atmospheric Boundary Layer (ABL) and the turbulent characteristics have also been shown in this paper.

Description: The mesoscale snow distribution over the Namco lake area of the Tibetan Plateau on October 2005 has been investigated in this paper. The base and revised experiments were conducted using the Weather Research Model (WRF) with three nested grids that included a 1 km finest grid centered on the Namco station. Our simulation ran from 6 October through to 10 October 2005, which was concurrent with long term meteorological observations. Evaluation against boundary layer meteorological tower measurements and flux observations showed that the model captured the observed 2 m temperature and 10 m winds reasonably well in the revised experiment. The results suggest that output snow depth maximum amounts from two simulated experiments were centered downwind of the Namco lakeshore. Modified surface state variable, for example, surface skin temperature on the lake help to increase simulated credibility.

Description: Land surface heat fluxes are essential measures of the strengths of land-atmosphere interactions involving energy, heat and water. Correct parameterization of these fluxes in climate models is critical. Despite their importance, state-of-the-art observation techniques cannot provide representative areal averages of these fluxes comparable to the model grid. Alternative methods of estimation are thus required. These alternative approaches use (satellite) observables of the land surface conditions. In this study, the Surface Energy Balance System (SEBS) algorithm was evaluated in a cold and arid environment, using land surface parameters derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Field observations and estimates from SEBS were compared in terms of net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λE) over a heterogeneous land surface. As a case study, this methodology was applied to the experimental area of the Watershed Allied Telemetry Experimental Research (WATER) project, located on the mid-to-upstream sections of the Heihe River in northwest China. ASTER data acquired between 3 May and 4 June 2008, under clear-sky conditions were used to determine the surface fluxes. Ground-based measurements of land surface heat fluxes were compared with values derived from the ASTER data. The results show that the derived surface variables and the land surface heat fluxes furnished by SEBS in different months over the study area are in good agreement with the observed land surface status under the limited cases (some cases looks poor results). So SEBS can be used to estimate turbulent heat fluxes with acceptable accuracy in areas where there is partial vegetation cover in exceptive conditions. It is very important to perform calculations using ground-based observational data for parameterization in SEBS in the future. Nevertheless, the remote-sensing results can provide improved explanations of land surface fluxes over varying land coverage at greater spatial scales.

Description: Surface fluxes are important boundary conditions for climatological modeling and Asian monsoon system. The recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection radiometer) sensor has enabled us to estimate surface fluxes. ASTER covers a wide spectral region with 14 bands from the visible to the thermal infrared with high spatial, spectral and radiometric resolution. The spatial resolution varies with wavelength: 15 m in the visible and near-infrared (VNIR), 30 m in the short wave infrared (SWIR), and 90 m in the thermal infrared (TIR). A parameterization method based on ASTER data and field observations has been proposed and tested for deriving surface albedo, surface temperature, Normalized Difference Vegetation Index (NDVI), Modified Soil Adjusted Vegetation Index (MSAVI), vegetation coverage, Leaf Area Index (LAI), net radiation flux, soil heat flux, sensible heat flux and latent heat flux over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP/Tibet), which located at the north Tibetan Plateau. The ASTER data of 24 July 2001, 29 November 2001 and 12 March 2002 was used in this paper for the case of summer, winter and spring. To validate the proposed methodology, the ground-measured surface variables (surface albedo and surface temperature) and land surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in three different months over the study area are in good accordance with the land surface status. Also, the estimated land surface variables and land surface heat fluxes are in good accordance with ground measurements, and all their absolute percent difference (APD) is less than 10% in the validation sites. It is therefore concluded that the proposed methodology is successful for the retrieval of land surface variables and land surface heat fluxes using the ASTER data and filed observation over the study area.

Description: Surface fluxes are important boundary conditions for climatological modeling and the Asian monsoon system. Recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) sensor has enabled us to estimate surface fluxes to bridge the gap between local scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A Surface Energy Balance System (SEBS) method based on ASTER data and field observations has been proposed and tested for deriving net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λ E) over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the WATER (Watershed Allied Telemetry Experimental Research), located at the mid-to-upstream sections of the Heihe River, northwest China. The ASTER data of 3 May and 4 June in 2008 was used in this paper for the case of mid-to-upstream sections of the Heihe River Basin. To validate the proposed methodology, the ground-measured land surface heat fluxes (net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λ E)) were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in different months over the study area are in good accordance with the land surface status. It is therefore concluded that the proposed methodology is successful for the retrieval of land surface heat fluxes using the ASTER data and filed observation over the study area.

Description: As a unique geological and geographical unit, the Tibetan Plateau dramatically impacts the world's environment and especially controls climatic and environmental changes in China, Asia and even in the Northern Hemisphere. Tibetan Plateau, therefore, provides a field laboratory for studying global change. With support from various agencies in the People's Republic of China, a Tibetan Observation and Research Platform (TORP) is now implementing. Firstly the background of the establishment of the TORP, the establishing and monitoring plan of long-term scale (5–10 years) of the TORP has been introduced. Then the preliminary observational analysis results, such as the characteristics of land surface heat fluxes and CO2 flux partitioning (diurnal variation, inter-monthly variation and vertical variation etc.), the characteristics of atmospheric and soil variables, the structure of the Atmospheric Boundary Layer (ABL) and the turbulent characteristics have also been shown in this paper.

Description: The mesoscale snow distribution over the Namco lake area of the Tibetan Plateau on October 2005 has been investigated in this paper. The control and sensitive experiments were conducted using Weather Research Model (WRF) with three nested grids that included a 1 km finest grid centered on the Namco station. Our simulation ran from 6 October through 10 October 2005, which was concurrent with long term meteorological observations. Evaluation against boundary layer meteorological tower measurements and flux observations showed that the model captured the observed 2 m temperature and 10 m winds reasonably well in the sensitive experiment. The results suggested that output snow depth maximum amounts from two simulated experiments were centered downwind shore of Namco lake. Modified surface parameters for example surface skin temperature on the lake help to increase simulated credibility.

Description: Turbulence statistics such as flux-variance relationship are critical information in measuring and modeling ecosystem exchanges of carbon, water, energy, and momentum at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT), this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environments such as nocturnal stable boundary layer.