A Machine Learning-based Cloud Detection Algorithm for the Himawari-8 Spectral Image

Cloud Masking is one of the most essential products for satellite remote sensing and downstream applications.This study develops machine learning-based(ML-based)cloud detection algorithms using spectral observations for the Advanced Himawari Imager(AHI)onboard the Himawari-8 geostationary satellite.Collocated active observations from Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)are used to provide reference labels for model development and validation.We introduce both daytime and nighttime algorithms that differ according to whether solar band observations are included,and the artificial neural network(ANN)and random forest(RF)techniques are adopted for comparison.To eliminate the influences of surface conditions on cloud detection,we introduce three models with different treatments of the surface.Instead of developing independent ML-based algorithms,we add surface variables in a binary way that enhances the ML-based algorithm accuracy by~5%.Validated against CALIOP observations,we find that our daytime RF-based algorithm outperforms the AHI operational algorithm by improving the accuracy of cloudy pixel detection by~5%,while at the same time,reducing misjudgment by~3%.The nighttime model with only infrared observations is also slightly better than the AHI operational product but may tend to overestimate cloudy pixels.Overall,our ML-based algorithms can serve as a reliable method to provide cloud mask results for both daytime and nighttime AHI observations.We furthermore suggest treating the surface with a set of independent variables for future ML-based algorithm development.

Grid-cell Aerosol Direct Shortwave Radiative Forcing Calculated Using the SBDART Model with MODIS and AERONET Observations：An Application in Winter and Summer in Eastern China

Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer（SBDART） model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth（AOD）occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo（SSA） in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere（TOA） and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity.Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.

Impact of Local Climate Zones on the Urban Heat and Dry Islands in Beijing:Spatial Heterogeneity and Relative Contributions

Based on the building height and density data on a 100-m resolution,hourly 2-m temperature and humidity data at83 automatic weather stations,and gridded local climate zone(LCZ)data on a 120-m resolution in urban Beijing in2020,this study first employs the semivariogram combined with building parameters to calculate spatial correlations and has identified an LCZ grid resolution of 500 m suitable for best usage of the available observation data.Then,how the spatially heterogeneous LCZs affect and contribute to the canopy urban heat island intensity(UHII)and urban dry island intensity(UDII)are quantitatively investigated.It is found that UHII is high in winter and low in summer with a unimodal diurnal variation while UDI is low in winter but high in summer with a bimodal diurnal variation.The LCZ with compact mid-rise(open high-rise)buildings exhibits the highest UHII(UDII),followed by the compact high-rise(compact low-rise),while the LCZ of scattered trees presents both the lowest UHII and the lowest UDII.The most significant difference in the UHII(UDII)among the nine LCZ types in the urban area of Beijing is2.62℃(1.1 g kg^(-1)).Area-weighted averaging analysis reveals that the open mid-rise LCZ is the most significant contributor to the UHII(UDII),immediately followed by compact mid-rise(open low-rise),with the least contribution from bare rock or paved(scattered trees).The results also indicate that beyond the intrinsic physical properties of the LCZs of a city,their area proportions cannot be overlooked in evaluating their impact on the UHI and UDI.These quantitatively findings could help urban planners to create a livable urban climate and environment by adjusting the relevant land use.

城市热浪与冠层热岛协同作用研究进展与展望

城市化的加速和人口聚集不仅加剧了城市冠层热岛效应,还影响高温热浪事件,二者的叠加效应将严重影响城市发展和居民健康。目前部分研究认为热浪与热岛之间存在协同加强的变化特征,但是热浪与城市热岛的叠加效应仍存在较大差异性。通过全面回顾和总结国内外关于热浪与热岛协同作用差异性方面的研究,并从气候背景、局地环流以及城市形态等方面探讨了城市高温的形成机制。在不同气候背景和局地环流条件下,热浪与热岛协同作用呈现出显著的时空差异性,尤其是局地环流的调节作用不可忽视。近10年提出的局地气候区分类在热浪与热岛协同作用方面的研究已经取得了一些成果,但是有必要从城市三维形态方面入手进一步探索其响应特征。目前,未统一标准的热浪定义对深入理解热浪—城市热岛相互作用带来了不确定性。当下需要更全面地了解热浪和热岛带来的城市过度变暖的时空差异性及其形成机制和调节因素,为高温监测和城市居住环境改善提供更详细的指导和理论支撑。

Advances in Atmospheric Radiation:Theories,Models,and Their Applications.PartⅡ:Radiative Transfer Models and Related Applications

The subject of“atmospheric radiation”includes not only fundamental theories on atmospheric gaseous absorption and the scattering and radiative transfer of particles(molecules,cloud,and aerosols),but also their applications in weather,climate,and atmospheric remote sensing,and is an essential part of the atmospheric sciences.This review includes two parts(Part I and PartⅡ);following the first part on gaseous absorption and particle scattering,this part(PartⅡ)reports the progress that has been made in radiative transfer theories,models,and their common applications,focusing particularly on the contributions from Chinese researchers.The recent achievements on radiative transfer models and methods developed for weather and climate studies and for atmospheric remote sensing are firstly reviewed.Then,the associated applications,such as surface radiation estimation,satellite remote sensing algorithms,radiative parameterization for climate models,and radiative-forcing related climate change studies are summarized,which further reveals the importance of radiative transfer theories and models.

Reporting quality evaluation of clinical practice guidelines for pulmonary nodules with the RIGHT checklist

To the Editor:Pulmonary nodules are defined as localized opacities of up to 30 mm in diameter,surrounded by pulmonary parenchyma or located adjacent to the pleura.^([1])The ideal management for pulmonary nodules is to diagnose and treat malignant nodules as early as possible and minimize radiation exposures,based on the general guidance.Clinical practice guidelines(CPGs)always provide efficient recommendations based on systematic reviews of high-quality evidence and reporting to optimize patient care.^([2])Accumulating evidence shows that adherence to the guidelines improves patient outcomes.^([3])However,the reporting quality of CPGs seems poor.^([4])Several instruments have been generated to evaluate the quality of CPGs.

Climatological Characteristics of Summer Precipitation over East Asia Measured by TRMM PR:A Review

Precipitation is an important indicator of climate change and a critical process in the hydrological cycle, on both the global and regional scales. Methods of precipitation observation and associated analyses are of strategic importance in global climate change research. As the first space-based radar, the Tropical Rainfall Measuring Mission （TRMM） Precipitation Radar （PR） has been in operation for almost 17 years and has acquired a huge amount of cloud and pre- cipitation data that provide a distinctive view to help expose the nature of cloud and precipitation in the tropics and subtropics. In this paper we review recent advances in summer East Asian precipitation climatology studies based on long-term TRMM PR measurements in the following three aspects： （1） the three-dimensional structure of precipita- tion, （2） the diurnal variation of precipitation, and （3） the recent precipitation trend. Additionally, some importantprospects regarding satellite remote sensing of precipitation and its application in the near future are discussed.

The most typical shape of oceanic mesoscale eddies from global satellite sea level observations

In this research, we normalized the character- istics of ocean eddies by using satellite observation of the Sea Level Anomaly （SLA） data to determine the most typical shape of ocean eddies. This normalization is based on modified analytic functions with nonlinear optimal fitting. The most typical eddy is the Taylor vortex （~50%）, which exhibits a Gaussian-shaped exp（-r2） SLA and a vorticity distribution of （1-rZ）exp（-r2） as a function of the normalized radii r. The larger the amplitude of the eddy, the more likely the eddy is to be Gaussian-shaped. Furthermore, approximately 40% of ocean eddies are combinations of two Gaussian eddies with different parameters, but the composition of these types of eddies is more like a quadratic eddy than a Gaussian one. Only a small portion of oceanic eddies are pure quadratic eddies （ 〈 10%） with the same vorticity distribution as a Rankine vortex. We concluded that the Taylor vortex is a good approximation of the typical shape of ocean eddies.

Relationship between Extreme Precipitation and Temperature in Two Different Regions:The Tibetan Plateau and Middle–East China

The change of extreme precipitation with temperature has regional characteristics in the context of global warming.In this study, radiosonde data, co-located rain gauge(RG) observations, and Tropical Rainfall Measuring Mission(TRMM) precipitation radar(PR) products are used to explore the relationship between extreme precipitation intensity and near-surface temperature in Middle–East China(MEC) and the eastern Tibetan Plateau(TP) during1998–2012. The results show that extreme precipitation intensity increases with increasing temperature at an approximate Clausius–Clapeyron(C–C) rate(i.e., water vapor increases by 7% as temperature increases by 1°C based on the C–C equation) in MEC and TP, but the rate of increase is larger in TP than in MEC. This is probably because TP(MEC) is featured with deep convective(stratiform) precipitation, which releases more(less) latent heat and strengthens the convection intensity on a shorter(longer) timescale. It is also found that when temperature is higher than 25°C(15°C) in MEC(TP), the extreme precipitation intensity decreases with rise of temperature, suggesting that the precipitation intensity does not always increase with warming. In this case, the limited atmospheric humidity and precipitable water could be the primary factors for the decrease in extreme precipitation intensity at higher temperatures.

Bronchoscopic transparenchymal nodule access in the diagnosis and management of pulmonary nodules

To the Editor:Transthoracic needle aspiration(TTNA)and bronchoscopy have been the preferred methods for the sampling of pulmonary nodules suspected of lung cancer.However,despite having a higher diagnostic accuracy,TTNA has been associated with a high rate of pneumothorax.Moreover,conventional bronchoscopy with a low rate of pneumothorax has exhibited a low diagnostic yield for peripheral pulmonary nodules,particularly for nodules<2 cm in size or those without a bronchus leading directly to them.Thus,Herth et al[1]developed a novel bronchoscopy technique called bronchoscopic transparenchymal nodule access(BTPNA)under the guidance of Archimedes Virtual Bronchoscopic Navigation(VBN)System for the purpose of accessing pulmonary nodules using a transparenchymal approach without relying on the airway to approach the lesion.Here,we systematically reviewed evidence regarding BTPNA to provide general guidance on the safe implementation and development of this novel approach.