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[1] It has been long believed that the dominant microwave signature of snowfall over land is the brightness temperature decrease caused by ice scattering. However, our analysis of multiyear satellite data revealed that on most of occasions, brightness temperatures are rather higher under snowfall than nonsnowfall conditions, likely due to the emission by cloud liquid water. This brightness temperature increase masks the scattering signature and complicates the snowfall detection problem. In this study, we propose a statistical method for snowfall detection, which is developed by using CloudSat radar to train high-frequency passive microwave observations. To capture the major variations of the brightness temperatures and reduce the dimensionality of independent variables, the detection algorithm is designed to use the information contained in the first three principal components resulted from Empirical Orthogonal Function (EOF) analysis, which capturẽ 99% of the total variances of brightness temperatures. Given a multichannel microwave observation, the algorithm first transforms the brightness temperature vector into EOF space and then retrieves a probability of snowfall by using the CloudSat radar-trained lookup table. Validation has been carried out by case studies and averaged horizontal snowfall fraction maps. The result indicated that the algorithm has clear skills in identifying snowfall areas even over mountainous regions.Citation: Liu, G., and E.-K. Seo (2013), Detecting snowfall over land by satellite high-frequency microwave observations: The lack of scattering signature and a statistical approach,

Four independently developed high-resolution precipitation products [HRPPs; the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), the Climate Prediction CenterMorphing Method (CMORPH), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), and the National Research Laboratory (NRL) blended precipitation dataset (NRL-blended)], with a spatial resolution of 0.258 and a temporal resolution of 3 h, were compared with surface rain measurements for the four summer seasons (June, July, and August) from 2003 to 2006. Surface measurements are 1-min rain gauge data from the Automated Weather Station (AWS) network operated by the Korean Meteorological Administration (KMA) over South Korea, which consists of about 520 sites. The summer mean rainfall and diurnal cycles of TMPA are comparable to those of the AWS, but with larger magnitudes. The closer agreement of TMPA with surface observations is due to the adjustment of the realtime version of TMPA products to monthly gauge measurements. However, the adjustment seems to result in significant overestimates for light or moderate rain events and thus increased RMS error. In the other three products (CMORPH, PERSIANN, and NRL-blended), significant underestimates are evident in the summer mean distribution and in scatterplots for the grid-by-grid comparison. The magnitudes of the diurnal cycles of the three products appear to be much smaller than those suggested by AWS, although CMORPH shows nearly the same diurnal phase as in AWS. Such underestimates by three methods are likely due to the deficiency of the passive microwave (PMW)-based rainfall retrievals over the South Korean region. More accurate PMW measurements (in particular by the improved land algorithm) seem to be a prerequisite for better estimates of the rain rate by HRPP algorithms. This paper further demonstrates the capability of the Korean AWS network data for validating satellite-based rain products.

A new prenylated chalcone, 3' ',3' '-dimethylpyrano[3',4']2,4,2'-trihydroxychalcone (1), was isolated from the heartwood of Artocarpus communis. Two flavonoid derivatives, (-)-cycloartocarpin (9) and (-)-cudraflavone A (10), were isolated as new isomers. In addition, eight known flavonoids, isobacachalcone (2), morachalcone A (3), gemichalcones B (4) and C (5), artocarpin (6), cudraflavone C (7), licoflavone C (8), and (2S)-euchrenone a(7) (11), were isolated and identified from this plant for the first time. Compounds 1-4, 6, and 11 exhibited potent inhibitory activity on nitric oxide production in RAW264.7 LPS-activated mouse macrophage cells with IC(50) values of 18.8, 6.4, 16.4, 9.3, 18.7, and 12.3 microM, respectively. The structure of compound 1 was elucidated by spectroscopic data analysis, including 1D and 2D NMR experiments.

[1] A snowfall retrieval algorithm based on Bayes' theorem is developed using high-frequency microwave satellite data. In this algorithm, observational data from both airborne and surface-based radars are used to construct an a priori database of snowfall profiles. These profiles are then used as input to a forward radiative transfer model to obtain brightness temperatures at high microwave frequencies. In the radiative transfer calculations, two size distributions for snowflakes and ten observed atmospheric sounding profiles are used with snowfall profiles from observations. In addition, the scattering properties of the snowflakes are calculated on the basis of realistic nonspherical shapes using discrete dipole approximation. The algorithm is first verified by airborne microwave and radar observations and then applied to the Advanced Microwave Sounding Unit-B (AMSU-B) satellite data. The retrieved snowfall rates using AMSU-B data from three snowfall cases in the vicinity of Japan show reasonable agreement with surface radar observations with correlation coefficients of about 0.8, 0.6, and 0.96 for the three cases, respectively. The comparison results also suggest the algorithm performs better for dry and heavy snow cases, but is less accurate for wet and weak snow cases.

Daphne genkwa SIEB. et ZUCC. (Thymelaeaceae) is a traditional oriental medicine that is widely distributed in Korea and China.1) The flower of this plant (Genkwa flos) has been traditionally used for abortifacient, diuretic, antitussive, expectorant, and anticancer effects.1-3) Previous phytochemical investigations of Genkwa flos led to the isolation of various compounds such as flavonoids, coumarins, amides, and diterpenes.4-9) Daphnane-type diterpenoids are typical constituents of plants from the families Thymelaeaceae and Euphorbiaceace. There have been reported several biological activities of daphnanes including antileukemia, piscicidal, toxicity, anticancer, abortion, and neurotrophy. 8,10,11) As part of our ongoing study for discovery of plant-derived anticancer agents, two new daphnane diterpenoids, namely, yuanhuahine (1) and yuanhualine (2), were isolated from Genkwa flos. The present study describes the structural elucidation of the two new isolates 1 and 2, along with their antiproliferative activities against human lung cancer cells and normal lung epithelial cells. Results and DiscussionCompound 1 was obtained as a white amorphous powder. Its molecular formula was determined as C 33 H 44 O 10 by the pseudo molecular ion peak at m/z 601.3013 [MϩH] ϩ in positive HR-FAB-MS. The IR spectrum of 1 showed absorptions at 3456 cm Ϫ1 for the hydroxyl groups and at 1695 cm Ϫ1 for the conjugated carbonyl group. The 13 C-and distortionless enhancement by polarization transfer (DEPT) 135 spectra of 1 indicated the presence of five methyls, seven methylenes, twelve methines, and nine quaternary carbons. In particular, an unusual quaternary carbon (C-1Ј) at d 117.2 was attributable to an orthoester group, which is a structural feature of daphnane-type diterpenoids. The quaternary carbon signals at d 209.7 and 173.4 in the 13 C-NMR spectrum were assignable to an a,b-unsaturated cyclopentanone and an ester group, respectively. The resonances of d H 3.56 and d C 64.3 (C-7) for an oxygenated methine group and at d C 60.7 (C-6) for an oxygenated quaternary carbon were upfield shifted, suggesting the presence of an epoxy group between C-6 and C-7. C-NMR of 1 were similar to those of yuanhuadine (4), except for the ethyl signals (C-2Љ and C-3Љ) of 1 instead of the methyl signal for the acetyl group in 4. 8,[12][13][14] The methyl signal at d H 1.09 (3H, t, 7.5, H-3Љ) exhibited three-bond connectivity with the conjugated carbon at d C 173.4 (C-1Љ) in the heteronuclear multiple bond correlation (HMBC) spectrum of 1, indicating that the ethyl group was attached to the carbon at C-1Љ (Fig. 2).The relative stereochemistry was determined by analysis of the rotating frame Overhauser enhancement spectroscopy (ROESY) data of 1 as shown in Fig. 3. The ROE correlation between H-12 and CH 3 -18 indicated the trans configuration between the functional groups at C-11 and C-12. Additional correlations between H-7 and H 2 -20, and between H-8 and H-11 and H-14 confirmed their cis positions to each other. Continuous correlations of H-1...

[1] A framework to retrieve ice water paths over a broad area by combining observations of surface cloud radar and satellite high-frequency microwave measurements in a physically consistent way is presented. The surface cloud radar provides the statistics of vertical distribution of ice water content, while the satellite retrievals use those statistics to broaden a point measurement to an areal measurement. This study seeks to improve retrievals by adopting newly available ice microphysical properties from recent in situ observations, and by treating single scattering properties based on discrete dipole approximation simulations of realistic nonspherical ice particles. First, a new radar reflectivity-ice water content relation is derived using backscattering cross sections calculated from six types of nonspherical ice particles. Ice water content profiles derived from radar reflectivity profiles are then used to calculate brightness temperatures at satellite observing frequencies by a radiative transfer model, which forms an a priori database for a Bayesian ice water path retrieval algorithm. Comparison between the satellite and surface radar retrievals shows that the two agree better for cases with ice water paths greater than 100 g m À2. For lower ice water paths, the difference between satellite and surface radar retrievals becomes large, presumably because of the insensitivity of the microwave scattering to optically thin ice clouds.Citation: Seo, E.-K., and G. Liu (2005), Retrievals of cloud ice water path by combining ground cloud radar and satellite high-frequency microwave measurements near the ARM SGP site,