基于MODIS雪盖数据的北疆雪深多元非线性回归克里金插值

为了提高北疆地区雪深时空分布监测的准确性,以该区域48个气象站点2006年12月—2007年1月的月平均雪深观测数据为基础,通过分析月均雪深空间自相关性及其与经纬度、高程的相关性,结合MODIS雪盖数据构建了多元非线性回归克里金插值方法,插值获得了北疆地区较高精度的雪深空间分布数据。将插值雪深数据与普通克里金插值法、考虑高程为辅助变量的协同克里金插值法的预测结果进行比较,结果表明:1相对普通克里金和协同克里金方法,多元非线性回归克里金法的12月份雪深预测精度分别提高了15.14%和9.54%,1月份的提高了4.8%和6.7%;2由于充分利用了经纬度和地形信息,多元非线性回归克里金法的雪深预测结果可提供更多细节信息;3预测结果客观地表达了雪深随经纬度和地形变化的趋势,反映了积雪深度的空间变异性;4基于不显著相关的协变量高程的协同克里金插值法预测的雪深数据精度劣于普通克里金插值法的预测结果。     

京津冀及周边地区冬季能见度与PM2.5浓度和环境湿度的多元回归分析

2013年至今,中国冬季与雾霾相伴的低能见度事件频发,京津冀及周边地区尤为严重。PM_2.5浓度与环境湿度是导致低能见度的最关键影响因素。为了深入研究PM_2.5浓度与环境湿度对大气能见度的影响,利用2017年1月京津冀及周边地区MICAPS气象数据与PM_2.5观测数据,运用天气学诊断分析方法讨论了不同相对湿度下PM_2.5浓度、环境湿度对冬季能见度变化的相对贡献,按照地理环境与污染程度差异将京津冀及周边地区划分为北京-天津地区与河北-山东地区,建立了PM_2.5浓度与环境湿度（由露点温度、温度代表）对能见度的多元回归方程,并对2015、2016、2018、2019年冬季能见度进行了回算检验。结果显示:相对湿度低于70%、PM_2.5浓度低于75 μg/m3时,北京-天津地区与河北-山东地区能见度多高于10 km,PM_2.5浓度升高是此时能见度迅速降低的主导因素;相对湿度从70%上升至85%和PM_2.5浓度从75 μg/m3升高200 μg/m3的共同作用导致了能见度降低到10 km至5 km;能见度进一步从5 km下降至2 km则更多依赖于相对湿度进一步从85%升高至95%,PM_2.5浓度与此时能见度相关减弱;能见度降低至2 km甚至更低主要是由于水汽近饱和状态下（相对湿度95%以上）的雾滴消光引起,与PM_2.5浓度的变化关系不大。与不分组直接拟合相比,以相对湿度85%为界线,分别拟合能见度能够很大程度优化多元回归模型,相对湿度高于85%时能见度拟合值的均方根误差从9.2和5.2 km下降至0.5和0.7 km,5 km以下拟合能见度的误差大幅度减小。按相对湿度85%将数据分组所得的拟合方程对2015、2016、2018、2019年1月能见度估算结果较好,观测值与拟合值相关系数均高于0.91,为雾-霾数值预报系统提供了新的能见度参数化算法。      

干冷空气入侵台风"海棠"残余低压引发的华北地区大暴雨分析

利用地面逐小时观测资料、NCEP/NCAR (1°×1°)再分析资料、FY-2F卫星加密观测(6 min分辨率)的云顶亮温(TBB)和常规观测资料,对1710号台风"海棠"残余低压北上与冷空气结合导致华北东部大暴雨天气过程进行分析。结果表明:(1)该华北东部大暴雨过程分为两个主要时段,2017年8月1日23时—2日20时(北京时)华北东南部暴雨,由台风残余低压产生,8月2日20时—3日11时华北东北部暴雨,是由减弱变性的台风环流与西风槽东移带来的干冷空气结合进而导致新生气旋和低涡产生引起。(2) 8月2日20时,台风与冷空气逐渐结合,干冷空气从对流层中高层进入变性台风北部,造成位涡下传,进而导致对流层低层形成低涡、地面形成新生气旋,同时激发出中尺度对流系统,系统稳定发展并缓慢向东北方向移动,导致持续近5 h的短时强降雨。(3)暴雨水汽来源主要有两部分,一是台风本身携带来的由南风输送的水汽,二是来自黄渤海由东风输送的水汽,二者结合后从对流层低层将水汽带至华北东北部,且在燕山前形成了水汽强辐合,为该暴雨过程大提供充足的水汽条件。     

太阳能热水器雷电防护技术分析

太阳能热水器的雷电防护隐患很大,每年都有不少雷击案例发生。通过调查发现,大多数热水器无雷电防护装置;多安装在屋顶,易招致雷击;安装人员多为非专业人员,缺乏必备的雷电防护知识。对太阳能热水器造成危害的不仅有直击雷,还有感应雷。因此,太阳能热水器的雷电防护,既要采取防直击雷防护措施,也要采取防雷电感应措施。     

Simulation of the Direct Radiative Effect of Mineral Dust and Sea Salt Aerosols in a Doubled Carbon Dioxide Climate

The authors examine the equilibrium climatic response to the direct radiative effect(DRE)of mineral dust and sea salt aerosols in a doubled-CO2climate with two-way coupling of aerosol-climate interactions.In response to the drier and windier conditions,dust emissions increase by 26%in the Sahara Desert and by 18%on the global scale relative to present day.Sea salt emissions increase in high latitudes(60°)but decrease in middle latitudes(30°–60°)of both hemispheres due to the poleward shift of westerlies,leading to a 3%decrease in global emissions.The burdens of dust and sea salt increase by 31%and 7%respectively,because reductions in rainfall over the tropical oceans increase the lifetime of particles in the warmer climate.The higher aerosol loading in the doubled-CO2climate reinforces aerosol DRE by0.2 W m 2,leading to an additional cooling of 0.1°C at the surface compared with the climatic effects of aerosols in present day.The additional cooling from changes in natural aerosols compensates for up to 15%of the regional warming induced by doubled CO2.     

A Case Study of the November 2012 Mixed Rain-Snow Storm over North China

A mixed rain-snow storm associated with a strong burst of cold air and development of an extratropical cyclone occurred over North China from 3 to 5 November 2012.This early snowfall event was characterized by a dramatic drop in temperature,strong winds,high precipitation intensity,broad spatial extent,and coexistence of multi-phase precipitating hydrometeors.This study investigates the multi-scale interactions between the large-scale circulation background and the synoptic-scale weather systems associated with the storm.The results are as follows.（1） The Arctic Oscillation （AO） had been in its negative phase long before the event,leading to southward advection of cold air into North China in advance of the storm.（2）The large-scale atmospheric circulation experienced a decreased number of long waves upstream of North China prior to the storm,resulting in reduced wave velocity and an almost stagnant low pressure system （extratropical cyclone） over North China.（3） An Ω-shaped blocking high over East Asia and the western Pacific obstructed the eastward movement of an upstream trough,allowing the corresponding surface cyclone to stabilize and persist over Beijing and its neighboring areas.This blocking high was a major factor in making this event a historically most severe precipitation event in autumn in Beijing for the past 60 years.（4） Baroclinic instability at lower levels gave rise to rapid development of the cyclone under the classical ＂second type＂ development mechanism for extratropical cyclones.（5） Moisture originated from the Yellow Sea entered the slowly-moving cyclone in a steady stream,creating fairly favorable water vapor supply for the heavy rainfall-snowfall,especially during the later stage of the cyclone development.（6） Moisture transport and frontal lifting triggered low-level instability and updrafts.Intensification of the front enhanced the vertical wind shear,causing conditional symmetric instability （CSI） to expand upward within the unstable lower troposphere,and to eventually gear into the CSI region of the upper troposphere,which facilitated the upward development of low-level updrafts.     

Quantifying global climate feedbacks, responses and forcing under abrupt and gradual CO2 forcing

Experiments with abrupt CO₂ forcing allow the diagnosis of the response of global mean temperature and precipitation in terms of fast temperature independent adjustments and slow, linear temperature-dependent feedbacks. Here we compare responses, feedbacks and forcings in experiments performed as part of version 5 of the coupled model inter-comparison project (CMIP5). The experiments facilitate, for the first time, a comparison of fully coupled atmosphere-ocean general circulation models (GCM’s) under both linearly increasing and abrupt radiative forcing. In the case of a 1 % per year compounded increase in CO₂ concentration, we find that the non-linear evolution of surface air temperature in time, when combined with the linear evolution of the radiative balance at the top of the atmosphere, results in a feedback parameter and effective climate sensitivity having an offset compared to values computed from abrupt 4× CO₂ forcing experiments. The linear evolution of the radiative balance at the top of the atmosphere also contributes to an offset between the global mean precipitation response predicted in the 1 % experiment using linear theory and that diagnosed from the experiments themselves, and a potential error between the adjusted radiative forcing and that produced using a standard linear formula. The non-linear evolution of temperature and precipitation responses are also evident in the RCP8.5 scenario and have implications for understanding, quantifying and emulating the global response of the CMIP5 climate GCMs.     

闽南沿海地区低能见度事件变化特征分析

利用2005-2010年闽南沿海地区9个气象站(厦门、同安、漳州、东山、漳浦、龙海、诏安、晋江和崇武)的日常观测能见度、相对湿度等气象资料,采用统计方法,探讨了闽南沿海地区低能见度事件的年、季和日变化等变化特征规律.分析发现,闽南沿海地区低能见度事件的年平均能见度一般在6 km左右,且低能见度在霾时总体要好于(轻)雾时;上半年低能见度事件持续时间较长且多发,下半年低能见度事件持续时间短且出现频率低于上半年.通常,08时的能见度最差,14时和20时转好,02时的能见度较08时要好,只有沿海测站东山站和崇武站在冬春季02时能见度较08时差.霾是造成闽南沿海地区出现低能见度事件的主要原因,(轻)雾次之,反映出该地区经济快速发展对能见度的影响.