商丘紫外线指数变化规律及气象因子影响分析

利用2003年4月至2006年6月商丘市气象台观测到的太阳紫外线指数资料及总云量、能见度、气温和相对湿度资料,分析了商丘市区紫外线指数的月、日变化规律以及气象因子与紫外线指数的关系。结果表明:①商丘紫外线指数1～2月和11～12月小,3～10月大,7～8月最大。②紫外线指数的日变化规律显著,基本上遵循正态分布,一天中辐射最强的时段在11:00～14:00,紫外线指数基本在6以上,辐射等级超过3级,紫外线照射强度中等以上。③紫外线指数与总云量、能见度、气温和相对湿度有较好的相关性。14:00的紫外线指数与同时次的总云量呈反相关,相关系数为-0.57;与能见度呈正相关,相关系数为0.64;与气温呈正相关,相关系数为0.46;与相对湿度呈反相关,相关系数为-0.8。     

贵阳地区太阳紫外辐射变化特征及主要影响因子分析

利用贵阳地区近6年太阳紫外辐射的观测资料及相关的气象因子,分析了该地区太阳紫外辐射的变化特征。结果表明,贵阳地区紫外辐射逐时平均最大值为21W.m-2（四级强度）,瞬时最大值为26.4W.m-2,未出现很强辐射（五级）的情况;4～9月出现强紫外辐射的时段较长,在10：00～15：00可达四级;13：00强紫外辐射在4～...     

贵阳地区太阳紫外线辐射及其预报方法研究

对近一年的紫外线辐射观测资料分析后发现：贵阳地区紫外线辐射较强，夏季辐射量比冬委大，一天中12－15时是紫外辐射最强的时段，少云天或晴天，冬季此外线辐射指数可达5以上，属中等辐射，夏季紫外辐射指数可达8以上，属较强或很强辐射。决定紫外线辐射强度的重要因素的重要因素主要主要是纬度，当地日照时间，云量，云状，空气污染程度等。因此可以通过对云量的预报作出相应的紫外线辐射量及紫外线指数预报。     

临沂市紫外线辐射变化特征分析

利用临沂市2004年7月至2005年6月逐日紫外线观测资料,分析太阳紫外线辐射强度指数和等级的年、季、月和日变化特征。指出临沂市日紫外线最大辐射强度为4级的日数为多数,即紫外线辐射指数为7~9的日数占52%,4级以上紫外线辐射主要出现在春夏季节,冬季紫外线辐射较弱,出现4级辐射日数很少且无5级辐射。晴空条件下,冬季太阳紫外线辐射强度日变幅明显小于其他季节,夏季日最大辐射强度出现在12-14时,较其他季节的日最大辐射强度出现时段滞后1小时。     

南宁市紫外线辐射变化特征及相关因子分析

文章分析了南宁市紫外线辐射的变化特征及其与太阳总辐射和云量的关系。指出南宁市紫外线辐射具有明显的季节变化，夏季最大，冬季最小。4月下旬开始紫外线逐渐增强，5～9月长达5个月时间紫外线强度维持在一个较高的水平，10月上旬开始紫外线迅速减弱。日最大值出现时间多数在12～14时。紫外线辐射量与太阳总辐射量相关系数达0．67，与部分月份云量也有较好的相关性，晴天的紫外线日变化曲线最为平滑，多云天气次之，少云天气下日变化曲线有较大波动。     

呼和浩特市紫外线辐射强度变化特征及相关因子分析

通过对2005年6月至2006年5月期间的紫外线辐射强度监测资料和同期太阳总辐射量、云量、相对湿度资料的统计分析,研究了紫外线辐射强度的变化特征及与相关气象因子的关系。指出紫外线辐射强度具有明显的季节变化,夏季最强,冬季最弱。紫外线辐射强度日变化有明显规律,日最大值出现时间多集中在12—14时。紫外线辐射强度与太阳总辐射量呈明显正相关,与云量、相对湿度呈明显负相关。     

湛江市地面太阳紫外线辐射观测及分析

利用湛江市气象观测站2006年3月～2007年2月的紫外线辐射资料及地面气象资料,分析了湛江市紫外线指数日变化和季节变化特征。结果表明,紫外线指数与总云量、低云量、日照时数、地面水平能见度、相对湿度有较好的相关性。运用多元线性回归、逐步回归方法,分析了紫外线的影响因子,发现太阳高度角、总云量、地面水平能见度和日照时数,是影响湛江市紫外线辐射强度的关键因素,通过信度为0.05的F检验,发现拟合方程对紫外线的趋势变化具有一定的能力。     

基于晴空阈值法的全天空红外图像云量计算

为提高新疆戈壁地区云的自动化观测水平,基于全天空红外成像仪(WSIRCMS)获取的红外辐射图像,利用辐射传输模式SBDART分析了仪器测量波段对有云无云状况的敏感性并构建了拟合方程,同时利用典型季节的晴空辐射样本拟合了晴空曲线并统计形成了晴空阈值,最后利用统计晴空阈值对全天空红外辐射图像进行云像素识别和总云量计算。将不同季节总云量计算结果同人工观测结果对比验证表明：观测时段算法计算总云量和人工观测总云量差值在±2成以下的概率均在80%以上,说明该方法具有较高的准确度和较强的实用性,在观测业务中具有较好的应用前景。     

影响白银市区太阳紫外辐射的初步分析

利用白银市区2003年3月～11月所采集的到达地面的太阳紫外辐射数据,分析了白银市区紫外辐射的月、日变化规律以及气象因子对紫外辐射的影响程度。分析结果表明,一年中,夏季的紫外线辐射最大,春季次之,秋季偏弱,冬季最弱;一日中,早晚时段辐射量小,中午时段辐射量大：云、气温、湿度等气象要素与紫外线辐射强度密切相关,尤其是云对紫外线有很大衰减作用。     

紫外线强度等级确定因子的季节性选择

利用南京市2005年2月—2009年1月的紫外线辐射观测资料,分析了到达地面的紫外线辐射强度的季节变化和日变化规律,并重点对各月10—14时的紫外线辐射平均值、最大值和最小值的强度级别分布频率进行了分析和讨论,提出根据不同季节来选择不同的紫外线辐射特性值作为紫外线强度等级的确定因子,夏季采用10—14时的紫外线辐射强度的最大值,冬季采用其最小值,春季和秋季采用其平均值。     

郑州地区紫外线辐射强度变化规律分析

由于地球自转和公转的原因,太阳紫外线辐射强度呈现出以一年和一天为周期的规律性变化.一年之内,以夏季最强,冬季最弱;一天之内,中午前后最强,早晚最弱.影响紫外线辐射强度的因子比较多,最主要的是云量、云状和能见度.经分析,紫外线辐射强度随着云量的增加而减小,随着能见度的增大而增强;高云对紫外线辐射强度影响较小,低云影响较大,中云居中.通过研究,确定了它们之间的定量关系.     

Characteristics of UV radiation at Tazhong of the Tarim Basin,west China

Tazhong station, located at the hinterland of the Taklimakan Desert in northwest China, experiences frequent dusty weather events during spring and summer seasons (its dusty season) caused by unstable stratified atmosphere, abundant sand source and strong low-level wind. On average, it has 246.2 dusty days each year, of which 16.2 days are classified as sand and dust storm days. To better understand the characteristic of solar ultraviolet (UV) radiation and factors influencing its variations under such an extreme environment, UV radiation data were collected continuously from 2007 to 2011 at Tazhong station using UVS-AB-T radiometer by Kipp and Zonen. This study documents observational characteristics of the UV radiation variations observed during the five-year period. Monthly UV radiation in this region varied in the range of 14.1–37.8 MJ m^?2 and the average annual amount was 320.7 MJ m^?2. The highest value of UV radiation occurred in June (62.5 W m^?2) while the lowest one in December (29.3 W m^?2). It showed a notable diurnal cycle, with peak value at 12:00–13:00 LST. Furthermore, its seasonal variation exhibited some unique features, with averaged UV magnitude showing an order of summer > spring > autumn > winter. The seasonal values were 37.0, 29.1, 24.9 and 15.9 MJ m^?2, respectively. In autumn and winter, its daily variations were relatively weak. However, significant daily variations were observed during spring and summer associated with frequent dust weather events occurring in the region. Further analysis showed that there was a significant correlation between the UV radiation and solar zenith angle under different weather conditions. Under the same solar zenith angle, UV radiation was higher during clear days while it was lower in sand and dust storm days. Our observations showed that there was a negative correlation between UV radiation and ozone, but such a relationship became absent in dusty days. The UV radiation was reduced by 6 % when cloud amount was 1–4 oktas, by 12 % when the cloud amount was 5–7 oktas, and by 24 % when the cloud amount was greater than 8 oktas. The relative reduction of UV radiation reached 26, 38, and 45 % in dust day, blowing sand day and sand and dust storm day, respectively. The results revealed that decrease in UV radiation can be attributed to cloud coverage and dust aerosols. Moreover, the reduction of UV radiation caused by dust aerosols was about 2–4 times greater than that caused by cloud coverage. These observational results are of value for improving our understanding of processes controlling UV radiation over sand desert and developing methods for its estimation and prediction.     

广州市地面太阳紫外线辐射观测和初步分析

通过对广州市2000～2001年两年的地面紫外线辐射观测资料的分析表明广州市全年紫外线辐射强度84.3%出现在"中等"以上级别,"强"、"很强"级别占65.1%,尤其是第二、三季度分别有46.2%、62.1%的时间紫外线出现"很强"级别,分析表明广州市属于紫外线高辐射地区;各候(旬)的最小紫外线指数在夏秋季节的涨落脉动比冬春季节要大,尤其是秋季更加明显.另外,定义了每月云衰减因子(CAF),12～4月为明显的云衰减加强期;6～9月为明显的云衰减减弱期,分析期间最大云衰减因子仅为0.11.     

到达地面的太阳紫外辐射强度的观测

紫外辐射强度的公众服务一般用紫外线指数来表示，是衡量某地正午前后到达地面的太阳紫外辐射对人体皮肤（或眼睛）可能损害的程度指标,沱主要依赖于纬度，季节，平流层臭氧，云况，海拔，地面反照率和大气污染状态等条件，紫外线辐射强度的观测主要使用紫外光谱辐射计与滤光片式的紫外辐射表。     

商丘市紫外线辐射与气象因子的关系

利用2003年4月至2006年6月商丘太阳紫外线辐射强度资料及气象资料,分析了商丘市紫外线辐射的月、日变化规律及气象因子对紫外线辐射的影响。结果表明:商丘紫外线辐射月际分布是,年初、年底辐射量小,3~9月辐射量大,最大辐射指数为11.4;紫外线辐射的日变化规律显著,基本上遵循正态分布,呈抛物线型变化,早晚辐射量小、中午前后紫外线辐射量大;紫外线辐射强度与总云量呈反相关,与能见度呈正相关,与气温呈正相关,与相对湿度呈反相关。     

紫外线辐射特征及影响因素分析

对太原市2002~2004年紫外线观测资料进行统计分析结果发现:紫外线辐射具有正午强早晚弱,夏季强冬季弱的特点;紫外线大值出现时间夏季明显早于冬季;通过与同时段气象因素对比分析,揭示了云状和云量、气压、能见度、湿度、空气污染对紫外线辐射的不同影响程度;紫外线辐射占太阳总辐射百分比具有冬季少夏季多和有云时非同比衰减的特点。紫外线的预报还要注重最大半小时平均值的预报,以预估紫外线对人体的最大可能伤害程度。     

南京市紫外线辐射强度的变化及影响因子

利用南京市2005-02—2009-01共4 a的紫外线辐射观测资料,分析了到达地面的紫外线辐射强度的变化特征,并探讨了云、污染物浓度和雾、霾天气等对紫外线辐射强度的影响。结果表明,低云量对紫外线强度的衰减更明显,最大达58.15%,蔽光性云层对紫外线辐射强度的衰减可达71%～80%;紫外线辐射强度与污染物浓度呈负相关,其中与NO2的相关性最好,为-0.39;晴空条件下,严重霾对紫外线辐射强度的衰减率可达20%以上,浓雾对紫外线辐射强度的衰减接近50%。     

On the use of a cloud modification factor for solar UV (290–385 nm) spectral range

Summary  Knowledge of ultraviolet radiation is necessary in different applications, in the absence of measurements, this radiometric flux must be estimated from available parameters. To compute this flux under all sky conditions one must consider the influence of clouds. Clouds are the largest modulators of the solar radiative flux reaching the Earth’s surface. The amount and type of cloud cover prevailing at a given time and location largely determines the amount and type of solar radiation received at the Earth’s surface. This cloud radiative effect is different for the different solar spectral bands. In this work, we analyse the cloud radiative effect over ultraviolet radiation (290–385 nm). This could be done by defining a cloud modification Factor. We have developed such cloud modification Factor considering two different types of clouds. The efficiency of the cloud radiative effect scheme has been tested in combination with a cloudless sky empirical model using independent data sets. The performance of the model has been tested in relation to its predictive capability of global ultraviolet radiation. For this purpose, data recorded at two radiometric stations are used. The first one is located at the University of Almería, a seashore location (36.83° N, 2.41° W, 20 m a.m.s.l.), while the second one is located at Granada (37.18° N, 3.58° W, 660 m a.m.s.l.), an inland location. The database includes hourly values of the relevant variables that cover the years 1993–94 in Almería and 1994–95 in Granada. Cloud cover information provided by the Spanish Meteorological Service has been include to compute the clouds radiative effect. After our study, it appears that the combination of an appropriate cloudless sky model with the cloud modification Factor scheme provides estimates of ultraviolet radiation with mean bias deviation of about 5% that is close to experimental errors. Comparisons with similar formulations of the cloud radiative effect over the whole solar spectrum provides evidence for the spectral dependency of the cloud radiative effect. Received November 15, 1999 Revised September 11, 2000     

Profiles of cloud fraction and water content deduced from ground-based solar radiation measurements

Ground-based measured solar radiation fluxes are used to derive simultaneously cloud water content and cloud fraction cover. In this paper we present a new method for prognostically inferring cloud microphysical properties based on previous work of Chou and Suarez. A look up table method combined with simulated annealing process is associated with the Chou and Suarez radiation transfer model called CLIRAD-SW. This model which is of great sensitivity has been validated for several atmospheres. Calculations here are conducted for an equivalent period of one year of measurement realized by the MINREST-LRE program for the Yaoundé meteorological station during the year 1984 and are focused on the previously derived average solar days similar to those proposed by Klein and more representative of the monthly solar radiation profile. In order to reduce computational time, mean values of liquid, mixed phase and ice cloud effective radius are used according to those proposed by Chou M.D. As part of our retrieving method, diffuse and global fluxes calculated for each set of cloud and aerosol microphysical characteristics are compared with the fluxes measured during the corresponding period. The obtained results are in very good agreement with those fluxes with relative errors ranging from 0.001% to 1.9% for diffuse flux and from 0.0009% to 2% for global flux. Mean cloud fraction profile obtained was generally well correlated with seasons whereas the correlation of cloud water content with seasons was not very good. However, the characteristic trend was in good agreement with the change in seasons. The overall agreement observed suggests that the method is capable of characterizing cloud water content and fraction for the given period of the day and the year although the lack of in situ measurements was a limitation for a valuable verification of the accuracy of the method.