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The correlation between climate change and pine tree dieback must be understood to implement a proactive forest management system. In this study, an ensemble model combining random forest, the generalized boosting model, and the generalized linear model was used to analyze the topographical and environmental characteristics of pine trees suffering from dieback in the Wangpicheon Ecosystem and Landscape Conservation Area, and the areas in which pine trees are at risk of dieback were evaluated to promote efficient pine forest management. The results showed that pine trees suffering from dieback in the conservation area were mainly located on ridges, were age class 6 or older, or were in areas with a low topographic wetness index south of the conservation area. An evaluation of the risk of dieback among pine trees was performed based on the results of two ensemble models. An area of 365 ha accounting for 6.8% of the total area was identified as requiring "caution" with respect to the risk of dieback of coniferous forests and mixed forests. The developed methodology is expected to provide valuable information for the implementation of an appropriate management system for the protection of pine and mixed forests from the negative effects of climate change. [ABSTRACT FROM AUTHOR]

Analysis of precipitation radar (PR) and Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI) data collected from the TRMM satellite shows that rainfall inhomogeneity, as represented by the coefficient of variation (CV), depends on a spatial scale, i.e., the CV appears to be nearly constant at all rain rates within the field of view (FOV) of the TMI 37-GHz channel, while it decreases with rain rate at lower spatial resolutions, such as the FOV sizes of the low-frequency TMI channels (10.7 and 19.4 GHz). It is known that the brightness temperature ([T.sub.b]) for a low-frequency channel decreases with increasing rainfall inhomogeneity for a given rain rate. As such, more inhomogeneous rainfall at low rain rates leads to a lower Tb compared with that of a FOV with homogeneous rainfall; however, less inhomogeneous rainfall at high rain rates tends to produce a Tb similar to that of homogeneous rainfalls. These results indicate that the observed radiometric signatures of low-frequency channels at low spatial resolutions are characterized by a larger response range and smaller variability than those at a higher spatial resolution. Based on the observational characteristics of the TMI and PR data sets, we performed synthetic retrievals of rainfalls, employing a Bayesian retrieval methodology at different retrieval resolutions corresponding to the FOV sizes of the TMI channels at 10.7, 19.4, and 37 GHz. Comparisons of the rainfalls retrieved at the different resolutions and their temporal and regional averages show that the systematic bias resulting from the rainfall inhomogeneity is smaller in the lower resolution data than in their higher resolution counterparts. We note that such low-resolution rainfall retrievals are not expected to describe the instantaneous features of rain fields; however, they could be useful for climatological estimates at large temporal and spatial scales. Index Terms--Passive microwave remote sensing, precipitation, rainfall variability.

The accuracy of a physically based passive microwave precipitation retrieval algorithm is affected by the quality of the a priori knowledge it employs, which indicates the relationship between the precipitation information obtained from cloud-resolving models (CRMs) and the simulated brightness temperatures (TBs) from radiative transfer models. As various microphysical assumptions reflecting a wide variety of sophisticated microphysical properties are applied to the CRMs, the TBs simulated based on the model-driven 3-D precipitation fields are determined by the selected microphysical assumption. In this article, we developed a prototype precipitation retrieval algorithm that incorporates various cloud microphysics schemes in its a priori knowledge (i.e., databases). In the retrieval process, a specific a priori database is selected for every target precipitation scene by comparing the similarities of the simulated and observed microwave emission and scattering signatures. The prototype algorithm was tested through application to precipitation retrieval for tropical cyclones at various intensity stages, which occurred over the northwestern Pacific region in 2015. The a priori databases constructed using the weather research and forecasting double-moment (WDM6) and Thompson Aerosol Aware schemes are superior when used for weak-to-moderate rainfall systems, whereas the databases constructed with the other schemes are superior within strong rain rate regions. The retrieval results obtained using the best-performing database are generally superior for all rain rate regions. Furthermore, we confirm that the database quality is more important than the number of databases. In comparison with the data from the dual-precipitation radar, the retrieval’s correlations, bias, and root mean square are 0.75, 0.14, and 5.62, respectively. [ABSTRACT FROM AUTHOR]

Physically based rainfall retrievals from passive microwave sensors often make use of cloud-resolving models (CRMs) to build a priori databases of potential rain structures. Each CRM, however, has its own cloud microphysics assumptions. Hence, approximated microphysics may cause uncertainties in the a priori information resulting in inaccurate rainfall estimates. This study first builds a priori databases by combining the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) observations and simulations from the Weather Research and Forecasting (WRF) model with six different cloud microphysics schemes. The microphysics schemes include the Purdue-Lin (LIN), WRF Single-Moment 6 (WSM6), Goddard Cumulus Ensemble (GCE), Thompson (THOM), WRF Double-Moment 6 (WDM6), and Morrison (MORR) schemes. As expected, the characteristics of the a priori databases are inherited from the individual cloud microphysics schemes. There are several distinct differences in the databases. Particularly, excessive graupel and snow exist with the LIN and THOM schemes, while more rainwater is incorporated into the a priori information with WDM6 than with any of the other schemes. Major results show that convective rainfall regions are not well captured by the LIN and THOM schemes-based retrievals. Rainfall distributions and their quantities retrieved from the WSM6 and WDM6 schemes-based estimations, however, show relatively better agreement with the PR observations. Based on the comparisons of the various microphysics schemes in the retrievals, it appears that differences in the a priori databases considerably affect the properties of rainfall estimations. [ABSTRACT FROM AUTHOR]

Physically based rainfall retrieval algorithms for passive microwave radiometers usuallydepend on the quality of a-priori information including assumptions on microphysicalproperties and distributions of hydrometeors. This study makes a-priori databases based onvarious microphysics (MP) schemes from the Weather Research and Forecasting (WRF)model. The tested MP schemes include Thompson, Morrison two moment, WRF DoubleMoment (WDM6), National Severe Storms Laboratory 2 moment (NSSL-2), and Thompsonaerosol aware schemes. Emission and scattering signals in the databases were simulated byconsidering microphysical properties of hydrometeors including hydrometeors’ density andsize distributions for each scheme. The simulated radiometric signatures are thencompared with the observation data from the Global Precipitation Measurement(GPM) Microwave Imager (GMI) for several tropical cyclones. Rainfall retrievalsfor the tropical cyclone cases are also performed with different MP scheme-baseddatabases. In comparison with the GPM Dual frequency Precipitation Radar (DPR)rainfall data, results show that better matching rainfall intensity tends to be producedby WDM6-based a-priori database for weak to moderate rainfall regions, and byThompson and Thompson aerosol aware schemes-based databases over strong rainfallregions. However, this study suggests it is incomplete to use only one MP scheme forconstructing a-priori database, but rather a variety of microphysical assumptions should betaken into account to describe various characteristics of precipitating cloud systems. [ABSTRACT FROM AUTHOR]

This study develops a stereoscopy-based cloud top height (CTH) retrieval algorithm using visible images acquired almost simultaneously from two geostationary satellites: the Japanese Himawari-8 (140.7 ºE) and the Chinese Feng-Yun-2E (FY-2E; 86.5 ºE). This algorithm is based on the parallax in cloud structure caused by the different viewing geometries of two geostationary satellites. The algorithm starts with reading observed digital numbers (DNs) and converting DNs to reflectance. The Himawari-8 data is projected into the FY-2E footprints (remapping) so that cloud structures can be comparable on the same location and the distortion of cloud structures from the different viewing geometries can be removed. Then, the parallax of cloud structure is measured by a normalized cross-correlation technique. The CTH is finally retrieved by a trigonometric calculation using the measured parallax and the satellite geometry information including satellite zenith angle and satellite azimuth angle. Retrieved CTH products are compared to other satellite products such as the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud product (MOD 06), which is the infrared brightness temperature-based product. The comparison results will be discussed. [ABSTRACT FROM AUTHOR]

Statistical approaches for quantitative precipitation nowcasts (QPNs) have emerged with recent advances in sensors in geostationary orbits, which provide more frequent observations at higher spatial resolutions. Several investigations have reported that extrapolation-based prediction can be more effective than numerical weather model-based prediction for a short lead time of less than a few hours. This study introduces the algorithm based on extrapolation method to produce QPN products for Advanced Meteorological Imager (AMI) onboard South Korea's second geostationary satellite (GEO-KOMPSAT-2A). The algorithm first provides the 3-hour potential accumulated rainfall (PAR) for a very-short-range forecast using extrapolation and then calculates the probability of rainfall (POR) during the same time period through statistical methods. The algorithm for PAR first identifies rainfall features and computes the motion vectors of the identified rainfall features through tracking between two consecutive GEO-KOMPSAT-2A rain rate images. The algorithm can then extrapolate future rainfall rates from current and previous rainfall rates outputs. In addition, the extrapolated rainfall fields are used as inputs for the POR estimation process, which produces the rainfall probability during the same 3-h period. POR is estimated based on rainfall frequency and adjusted by neighboring rainfall feature information. POR can provide a quantitative measure for the uncertainty in the PAR estimates. Retrieved PAR and POR from the QPN algorithm are validated with 3-h accumulated rainfalls obtained from the GEO-KOMPSAT-2A rain rate products. Forecasting accuracy of the PAR algorithm with time has also been investigated. The accuracy tends to decrease with increasing lead time, as expected. It may be due to the limitations of the extrapolation technique and degradation of the accuracy of the PAR estimates. The details on the improvements from the prototype algorithm and validation statistics will be discussed.AcknowledgementThis work is supported by the Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (Grant 18AWMP-B127555-02). [ABSTRACT FROM AUTHOR]

Abstract: The washout effect of summertime rain on surface air pollutants (O3, CO, NO2, SO2, and PM10) has been investigated over South Korea during 2002–2012 using routinely available air-monitored and meteorological data. Three new washout indices for PM10, SO2, NO2, and CO are developed to express the effect of precipitation scavenging on these pollutants. All of these pollutants show statistically significant negative correlations between their concentrations and rain intensity due to washout or convection. The washout effect is estimated for precipitation episodes classified by rain intensity (one set included all episodes and another included a subset of moderate intensity episodes that exclude Changma and typhoons), based on the log-transformed hourly data. The most sensitive air pollutant to the rain onset among these five air pollutants is PM10. The relative effect of the rainfall washout on the air pollutant concentrations is estimated to be: PM10 > SO2 > NO2 > CO > O3, indicating that PM10 is most effectively scavenged by rainfall. The analysis suggests that the O3 concentrations may increase due to vertical mixing leading to its downward transport from the lower stratosphere/upper troposphere. The concentrations of CO are reduced, probably due to both the washout and convection. The concentrations of NO2 are affected by the opposing influences of lightning-generation and washout and this are discussed as well. [Copyright &y& Elsevier]

We evaluated the change of corneal endothelium after trabeculectomy with mitomycin-C soaking (0.2 mg/ml, 2.4 +/- 1.2 minutes) and the effect of viscoelastic material in reducing this change. In randomly selected cases, 0.05 ml of sodium hyaluronate(Healon) was injected into anterior chamber (Healon group, n = 20), and same amount of balanced salt solution was injected in the other eyes (Control, n = 18) at the beginning of surgery. There were no differences in clinical variables and specular microscopy result between 2 groups before surgery. After surgery, the change of endothelial cells were significantly reduced in Healon group (cell density; -2.5 +/- 1.6%, variability of cell area; 5.8 +/- 2.5%, and percentage of hexagonal cell; -2.2 +/- 0.7%) compared to control group (-7.7 +/- 6.0%, 8.9 +/- 4.4%, and -4.8 +/- 3.5% respectively, p < 0.01). In trabeculectomy with mitomycin-C, the damage to the corneal endothelium was reduced significantly by injecting the viscoelastic material without significant complication.