High saline waters in Bay of Bengal

Bay of Bengal is well known for less saline waters in the surface layer of northern Indian Ocean. High saline waters of the Bay are considered as an influx from the Arabian Sea within a depth range of 200 to 900 m. Some of the recent observations in the western Bay of Bengal have shown salinity values higher than those reported earlier (35-2 × 10⁻³). Such values are explained on the basis of regional climatology suggesting their local formation on the shallow continental shelf during pre-monsoon months and their subsequent distribution along the coast.     

Assessment of the importance of moderate spatial resolution cloud climatology data in solar radiation modeling

Improving solar radiation models is critical for supporting the increase in solar energy usage and modeling ecosystem dynamics. However, coarse spatial resolutions of solar radiation models overlook the impacts resulting from spatial variability of clouds at meso- and micro-scales. To address this problem, Moderate Resolution Imaging Spectroradiometer (MODIS) cloud climatology developed by the National Severe Storms Laboratory was used to relate cloudiness to surface solar radiation observations. We developed a linear regression model between the surface solar radiation and MODIS cloud climatology and used the model to estimate average radiation across Oklahoma. Furthermore, the study compared the average error and coefficient of determination to measured ground radiation. Error analysis of the regression model showed that the differences between observed radiation and estimated radiation were spatially autocorrelated for the Aqua MODIS satellite scan. This suggests cloudiness alone is not sufficient to predict surface solar radiation. This study found that simple cloud datasets alone can account for approximately 50% of the variation in observed solar radiation at 250-m spatial resolution, but additional datasets such as optical depth, elevation, and slope are needed to accurately explain spatial distributions of incoming shortwave radiation.     

Monitoring the Sensible Heat Flux over Urban Areas using Large Aperture Scintillometry: Case Study of Marseille City During the Escompte Experiment

Abtract Sensible heat flux estimated by Large Aperture Scintillometry (LAS) has been tested against the more traditional eddy covariance technique over Marseille city centre, a reasonably homogeneous surface. Over the 3 week test period fluxes were found to be similar, yet less noisy for the LAS due to the spatial integration. No systematic bias between the estimates was found as a function of wind direction, indicating the homogeneity of the site. Sensitivity analysis of the required aerodynamic parameters shows that careful attention must be paid to the displacement height along the measurement path. Spatial variability of surface sensible heat flux is studied via a second LAS measurement path over the city.     

云和辐射 （I）:云气候学和云的辐射作用

本文介绍与气候变化研究有密切关系的云的辐射作用的有关工作。这一部分从云微物理特性和云粒子光学性质入手，介绍了水云、冰云的太阳和红外辐射特性的理论和实测工作以及云的不均匀性对云辐射特性的影响。此外，还介绍了云气候学及云对辐射收支影响方面的工作。     

浑沌气候学研究进展

对近几十年来兴起的动力气候模式作了全面的介绍和分析,指出气候系统是一类浑沌动力系统,具有对参数和初值的极其敏感性、内在随机性,以及自相似性等。Lorenz最先发现气候系统中的浑沌性质,之后Saltzman建立一系列简单的海洋、大气、海冰耦合的动力气候模式,通过对这些模式的试验研究,揭示了气候随太阳辐射、二氧化碳、气溶胶等参数的变化规律及其浑沌动力学性质。这些性质都表现在各种气候因子的时间序列中,为此,人们开始从时间序列中提取动力系统的演变信息,如计算分维数、Lyapunov指数以及建立相空间预报模式等。本文就上述问题的研究进展进行了全面的综述并作了展望。     

粤东暴雨中心的降水气候统计特征和成因分析

基于广东省1967—2018年气象观测站和2003—2018年自动监测站降水数据,以及ERA-Interim每日4次的再分析资料,分析了粤东暴雨中心降水气候统计特征和形成原因。结果表明:根据年降水量≥1 800 mm且年强降水日≥8.0 d的标准,粤东暴雨中心的范围为莲花山脉附近的惠州惠东,汕尾全市和揭阳市揭西、惠来、普宁以及汕头市潮南,区域内易出现极端强降水;粤东暴雨中心降水具有明显的月和季节变化特征,汛期降水量和强降水日分别占全年的84.3%和90.0%,且前汛期略多于后汛期。月变化为单峰型分布,年变化总体趋势较为平稳;粤东暴雨中心的形成与莲花山山脉及附近地形和海陆分布息息相关,在有利的大气环流配置下,当低空暖湿急流在粤东沿海脉冲、辐合时,易在莲花山山脉附近出现强降水过程。     

近10年严重影响云浮市台风的特征

通过对云浮市2009—2018年致灾严重(直接经济损失达到1 000万元以上)的台风资料进行统计分析,结果表明:对云浮市致灾严重的台风其生成源地多为西北太平洋。移动路径为西北太平洋西北行或者西行的台风、南海的北行台风。登陆地点在珠江口以西,特别是在江门地区附近。登陆时强度达到台风级别。登陆月份在8和9月。台风影响云浮市时的最大风力点多出现在新兴县和罗定市。台风影响云浮市24和48 h最大雨量点均出现在新兴县和罗定市。     

1962—2017年恩平市气温与降水的气候特征

采用数理统计、线性趋势、复Morlet小波变换、M-K突变检验和滑动平均T检验等方法,分析了恩平市1962—2017年气温和降水的气候特征,结果表明:恩平市近56年年平均气温上升趋势极端显著,在1993年发生由偏低向偏高的突变,并包含13、9、4年左右的多重周期变化。气温波动的幅度先增大后减小,气温冷和暖的年份相对集中。年、汛期、前汛期、后汛期降水均呈递减趋势,在1999年年降水发生由偏多向偏少的突变,并包含20、13、10、5、3年左右的多重周期变化。年降水呈Weibull分布,50年一遇年降水对应重现期的雨量阈值为3 665.6 mm。近10年年平均气温呈自东向西降低分布,年平均降水呈自西南向东北递减分布。     

Dynamical Downscaling of the Arctic Climate with a Focus on Polar Cyclone Climatology

We present a dynamical downscaling of the Arctic climatology using a high-resolution implementation of the Polar Weather Research and Forecasting, version 3.6 (WRF3.6) model, with a focus on Arctic cyclone activity. The study period is 1979–2004 and the driving fields are data from the Hadley Centre Global Environmental Model, version 2, with an Earth System component (HadGEM2-ES) simulations. We show that the results from the Polar WRF model provide significantly improved simulations of the frequency, intensity, and size of cyclones compared with the HadGEM2-ES simulations. Polar WRF reproduces the intensity of winter cyclones found in ERA-Interim, the global atmospheric reanalysis produced by the European Centre for Medium-range Weather Forecasts (ECMWF), and suggests that the average minimum central pressure of the cyclones is about 10?hPa lower than that derived from HadGEM2-ES simulations. Although both models underestimate the frequency of summer Arctic cyclones, Polar WRF simulations suggest there are 10.5% more cyclones per month than do HadGEM2-ES results. Overall, the Polar WRF model captures more intense and smaller cyclones than are obtained in HadGEM2-ES results, in better agreement with the ERA-Interim reanalysis data. Our results also show that the improved simulations of Arctic synoptic weather systems contribute to better simulations of atmospheric surface fields. The Polar WRF model is better able to simulate both the spatial patterns and magnitudes of the ERA-Interim reanalysis data than HadGEM2-ES is; in particular, the latter overestimates the absorbed solar radiation in the Arctic basin by as much as 30?W?m^?2 and underestimates longwave radiation by about 10?W?m^?2 in summer. Our results suggest that the improved simulations of longwave and solar radiation are partly associated with a better simulation of cloud liquid water content in the Polar WRF model, which is linked to improvements in the simulation of cyclone frequency and intensity and the resulting transient eddy transports of heat and water vapour.     

中国太阳总辐射的气候学计算法研究(英文)

Angstrom-Prescott公式的气候学计算法是应用较广的太阳辐射模拟方法,其系数一般通过线性回归确定。近年来,许多研究显示该系数存在明显的空间变异性,常见的解决方法是将研究区划分子区域逐个拟合。本研究采用1961-2010时段日照时数与太阳辐射站点资料,以天文辐射为起始值,基于地理加权回归得到全国尺度连续变化的Angstrom-Prescott系数。通过高精度曲面建模方法(HASM)构建的日照时数资料和天文辐射曲面,得到国家尺度太阳辐射曲面。空间非平稳和误差比较检验等结果表明,系数存在显著的空间非平稳性;与已有研究相比,本研究的模拟方法效果较好。