Global Soil Moisture Patterns Observed by Space Borne Microwave Radiometers and Scatterometers

Within the scope of the upcoming launch of a new water related satellite mission (SMOS) a global evaluation study was performed on two available global soil moisture products. ERS scatterometer surface wetness data was compared to AMSR-E soil moisture data. This study pointed out a strong similarity between both products in sparse to moderate vegetated regions with an average correlation coefficient of 0.83. Low correlations were found in densely vegetated areas and deserts. The low values in the vegetated regions can be explained by the limited soil moisture retrieval capabilities over dense vegetation covers. Soil emission is attenuated by the canopy and tends to saturate the microwave signal with increasing vegetation density, resulting in a decreased sensor sensitivity to soil moisture variations. It is expected that the new low frequency satellite mission (SMOS) will obtain soil moisture products with a higher quality in these regions. The low correlations in the desert regions are likely due to volume scattering or to the dielectric dynamics within the soil. The volume scattering in dry soils causes a higher backscatter under very dry conditions than under conditions when the sub-surface soil layers are somewhat wet. In addition, at low moisture levels the dielectric constant has a reduced sensitivity in response to changes in the soil moisture content. At a global scale the spatial correspondence of both products is high and both products clearly distinguish similar regions with high seasonal and inter annual variations. Based on the global analyses we concluded that the quality of both products was comparable and in the sparse to moderate vegetated regions both products may be beneficial for large scale validation of SMOS soil moisture. Some limitations of the studied products are different, pointing to significant potential for combining both products into one superior soil moisture data set. © The Author(s) 2008

An evaluation of ASCAT surface soil moisture products with in-situ observations in Southwestern France

A long term data acquisition effort of profile soil moisture is currently underway at 13 automatic weather stations located in Southwestern France. In this study, the soil moisture measured in-situ at 5 cm is used to evaluate the normalised surface soil moisture (SSM) estimates derived from coarse-resolution (25 km) active microwave data of the ASCAT scatterometer instrument (onboard METOP), issued by EUMETSAT for a period of 6 months (April–September) in 2007. The seasonal trend is removed from the satellite and in-situ time series by considering scaled anomalies. One station (Mouthoumet) of the ground network, located in a mountainous area, is removed from the analysis as very few ASCAT SSM estimates are available. No correlation is found for the station of Narbonne, which is close to the Mediterranean sea. On the other hand, nine stations present significant correlation levels. For two stations, a significant correlation is obtained when considering only part of the ASCAT data. The soil moisture measured in-situ at those stations, at 30 cm, is used to estimate the characteristic time length (<i>T</i>) of an exponential filter applied to the ASCAT product. The best correlation between a soil water index derived from ASCAT and the in-situ soil moisture observations at 30 cm is obtained with a <i>T</i>-value of 14 days

Afternoon rain more likely over drier soils

Land surface properties, such as vegetation cover and soil moisture, influence the partitioning of radiative energy between latent and sensible heat fluxes in daytime hours. During dry periods, a soil-water deficit can limit evapotranspiration, leading to increased surface heating ofwarmer and drier conditions in the lower atmosphere and affecting the climate. Soil moisture can influence the development of convective storms through such modifications of low-level atmospheric temperature and humidity, which in turn feeds back on soil moisture. Yet there is considerable uncertainty in how soil moisture affects convective storms across the world, owing to a lack of observational evidence and uncertainty in large-scale models. Here we present a global-scale observational analysis of the coupling between soil moisture and precipitation. We show that across all six continents studied, afternoon rain falls preferentially over soils that are relatively dry compared to the surrounding area. The signal emerges most clearly in the observations over semi-arid regions, where surface fluxes are sensitive to soil moisture, and convective events are frequent. Mechanistically, our results are consistent with enhanced afternoon moist convection driven by increased sensible heat flux over drier soils, and/or mesoscale variability in soil moisture. We find no evidence in our analysis of a positive feedback—that is, a preference for rain over wetter soils—at the spatial scale (50–100 kilometres) studied. In contrast, we find that a positive feedback of soil moisture on simulated precipitation does dominate in six state-of-the-art global weather and climate models—a difference that may contribute to excessive simulated droughts in large-scale models

Synthesis of triazolylmethyl-linked nucleoside analogs via combination of azidofuranoses with propargylated nucleobases and study on their cytotoxicity

KARAYILDIRIM, Tamer/0000-0001-7451-0810; HALAY, Erkan/0000-0002-0084-7709WOS: 000429350900009Copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition reactions (CuAAC) between azidofuranoses and propargyl-nucleobases were carried out in the presence of CuSO4 center dot 5H(2)O and sodium ascorbate as catalytic system to provide the corresponding 1,4-disubstituted-1,2,3-triazole-bridged nucleoside analogs in good yields. Twelve new sugar-based triazolylmethyl-linked nucleoside analogs were synthesized and screened for their cytotoxic activity against MDA-MB-231, Hep3B, PC-3, SH-SY5Y, and HCT-116 cancer cell lines and control cell line (L929). Most of the compounds were moderately effective against all the cancer cell lines assayed. Particularly, among the tested compounds, 1,2,3-triazole-linked 5-fluorouracil-mannofuranose hybrid was found to be the most potent cytotoxic agent against HCT-116, Hep3B, SH-SY5Y cells with IC50 values of 35.6, 71.1, and 75.6 mu M, respectively. None of the triazolylmethyl-linked nucleoside analogs exhibited cytotoxic effect against the control cells L929.TUBITAK-Research Council of Turkey [114Z757]; TUBITAK-BIDEBTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [2211A]This work was supported by TUBITAK-Research Council of Turkey with the project number 114Z757. Author E. Halay also offers his profound thanks to TUBITAK-BIDEB 2211A for their bursary support

Role of the Filters in the Formation and Stabilization of Semiquinone Radicals Collected from Cigarette Smoke

The fractional pyrolysis of Bright tobacco was performed in nitrogen atmosphere over the temperature range of 240 – 510 °C in a specially constructed, high temperature flow reactor system. Electron paramagnetic resonance (EPR) spectroscopy was used to analyze the free radicals in the initially produced total particular matter (TPM) and in TPM after exposure to ambient air (aging). Different filters have been used to collect TPM from tobacco smoke: cellulosic, cellulose nitrate, cellulose acetate, nylon, Teflon and Cambridge. The collection of the primary radicals (measured immediately after collection of TPM on filters), the formation and stabilization of the secondary radicals (defined as radicals formed during aging of TPM samples on the filters) depend significantly on the material of the filter. A mechanistic explanation about different binding capability of the filters decreasing in the order: cellulosic < cellulose nitrate < cellulose acetate < nylon ~ teflon is presented. Different properties were observed for the Cambridge filter. Specific care must be taken using the filters for identification of radicals from tobacco smoke to avoid artifacts in each case