Spectral dependence on the correction factor of erythemal UV for cloud,aerosol, total ozone,and surface properties: A modeling study

Radiative transfer model simulations were used to investigate the erythemal ultraviolet(EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors(CFEUV) for UV-A[CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from-5.0% to 25.0% for aerosols, and from-9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions(i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%–4.1% per 0.1 albedo change,depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.     

The effect of ozone and aerosols on the surface erythemal UV radiation estimated from OMI measurements

Surface erythemal UV radiation is mainly affected by total column ozone, aerosols, clouds, and solar zenith angle. The effect of ozone on the surface UV radiation has been explored many times in the previous studies due to the decrease of ozone layer. In this study, we calculated the effect of aerosols on the surface UV radiation as well as that of ozone using data acquired from Ozone Monitoring Instrument (OMI). First, ozone, aerosol optical depth (AOD), and surface erythemal UVB radiation measured from satellite are compared with those from ground measurements. The results showed that the comparison for ozone was good with r ² of 0.92. For aerosol, there was difference between satellite measurements and surface measurements due to the insufficient information on aerosol in the retrieval algorithm. The r ² for surface erythemal UV radiation was high (～0.94) but satellite measurements showed about 30% larger values than surface measurements on average by not considering the effect of absorbing aerosols in the retrieval process from satellite measurements. Radiative amplification factor (RAF) is used to access the effect of ozone and aerosol quantitatively. RAF for ozone was 0.97～1.49 with solar zenith angle. To evaluate the effect of aerosol on the surface UV radiation, only clear-sky pixel data were used and solar zenith angle and total column amount of ozone were fixed. Also, RAF for aerosol was assessed according to the single scattering albedo (SSA) of aerosols. The results showed that RAF for aerosol with smaller SSA (< 0.90) was larger than that for with larger SSA (> 0.90). The RAF for aerosol was 0.09～0.22 for the given conditions which was relatively small compared to that for ozone. However, considering the fact that aerosol optical depth can change largely in time and space while the total column amount of ozone does not change very much, it needs to include the effect of aerosol to predict the variations of surface UV radiation more correctly.     

Long-Term Trend in Ozone and Erythemal UV at Indian Latitudes

The role of atmospheric ozone to protect the living organisms and vegetation from the harmful effects of ultraviolet irradiation is well known. Depletion of the ozone layer is a great threat to the human society. In this paper we have discussed the lethal effects of ozone depletion and have presented the ozone and UV-B scenarios from 1979 to 2005 at different Indian latitudes using satellite data. The erythemal UV irradiance data obtained from Nimbus-7 and Earth probe total ozone mapping spectrometer (TOMS) and the tropospheric and stratospheric ozone data obtained from the convective cloud differential (CCD) method have been used to study the variability of erythemal UV irradiance and the stratospheric and tropospheric column ozone, respectively, over a period from 1979 to 2005. The observed results along with the expected upper and lower tolerance limits for tropospheric and stratospheric ozone, respectively, for different Indian latitudes, which have been estimated statistically using monthly mean CCD ozone data from 1979 to 2005 have been discussed in detail.     

The influence of clouds on surface UV erythemal irradiance

The purpose of this study is to examine the effect of clouds on the ultraviolet erythemal irradiance. The study was developed at three stations in the Iberian Peninsula: Madrid and Murcia, using data recorded in the period 2000–2001, and Zaragoza, using data recorded in 2001. In order to determine the cloud effect on ultraviolet erythemal irradiance, we considered a cloud modification factor defined as the ratio between the measured values of ultraviolet erythemal irradiance and the corresponding clear-sky ultraviolet erythemal irradiance, which would be expected for the same time period and atmospheric conditions. The dependence of this cloud modification factor on total cloud amount, cloud type and solar elevation angle was investigated. The results suggest that the effect of cloud on ultraviolet erythemal irradiance can be parameterized in a simple way in terms of the cloud amount. Our results suggest that the same cloud modification factor model can be used at the three analysed locations estimating the ultraviolet erythemal irradiance with mean bias deviation (MBD) in the range of the expected experimental errors. This cloud modification factor is lower than that associated to the whole solar spectral range, indicating that the attenuation for the ultraviolet erythemal irradiance is lower than that associated to other solar spectral ranges. The cloud modification factor for ultraviolet erythemal irradiance presents dependence with solar elevation, with opposite dependencies with solar elevation for overcast and partial cloud cover conditions, a fact that can be explained in terms of the influence of reflection-enhancement of the ultraviolet irradiance in the last case. Concerning the influence of cloud type, a limited study of two cloud categories, low and medium level and high level, indicated that for overcast conditions, lower clouds presents an attenuation of ultraviolet erythemal irradiance 20% greater than that associated to high level clouds.     

Ozone and Spectroradiometric UV Changes in the Past 20 Years over High Latitudes

Abstract

This study analyzes changes in solar ultraviolet (UV) irradiances at 305 and 325?nm at selected sites located at high latitudes of both hemispheres. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets of the past twenty years (1990–2011). The results show that over northern high latitudes, between 55° and 70°N, UV irradiances at 305?nm decreased significantly by 3.9% per decade, whereas UV irradiance at 325?nm remained stable with no significant long-term change. Over southern high latitudes (55°–70°S), UV irradiances did not show any significant long-term changes at either 305 or 325?nm. Changes in solar UV irradiances are discussed in the context of long-term ozone and other atmospheric parameters affecting UV variability at ground level.     

Assessment of Erythemal UV Level in Nepal Based on Solar UV Estimates from Total Ozone Mapping Spectrometer

Nepal lies on the southern slope of Himalaya in Asia. In a width ranging between 150 and 250 km, the altitude varies greatly from about 100 m at its southern border to a maximum of 8848 min the northern part. Like the variation in altitude, climatic condition varies quite a lot. Long-term monthly mean erythemal UV daily dose values for Nepal are evaluated using Total Ozone Mapping Spectrometer (TOMS) estimation from the time of its overpass between 1996 and 2003. The results are presented as summer and winter maps of mean UV levels in each satellite grid. The mean winter erythemal UV daily dose ranges between 2.1 and 3.6 kJ m-2 whereas summer values are found to lie between 4.6 and 9.7 kJ m-2. The altitude variation increases the UV levels by about 0.2 kJ km-1 in winter months, and 0.9 kJ km-1 in summer. A multiyear monthly average erythemal daily dose in most of the areas shows that the summer value is about three times higher than that in winter. Although year-to-year variation is not pronounced in high- and mid-elevation regions, UV levels seemed to decrease from 1997 to 2002 in the southern part of the country in the low elevation region by about 5.35%. Due to the combined effects of the altitude, low ozone concentration in the troposphere, and thin air, surface UV radiation at higher altitudes is found to be higher than in the surrounding regions.     

Influence of Clouds on UV Irradiance at Ground Level and Backscattered Exittance

The influence of various cloud parameters and the interactions with the ground albedo and the solar zenith angle have been studied by means of model simulations. The radiative transfer model suitable for a cloudy atmosphere as well as for a clear atmosphere has been developed on the basis of the Discrete Ordinate Method. This study leads to a general understanding for cloudy atmospheres: in the presence of a uniform cloud, the cloud scattering is dominant to molecular and aerosol scattering, and it is also wavelength-independent; the ratio of transmitted irradiance in a cloudy atmosphere to that in the background clear atmosphere is independent of cloud height and solar zenith angle. That’s to say, the radiation downwelling out of a cloud is quite isotropic; it decreases approximately exponentially with the cloud optical depth at a rate related to the ground albedo; the reflected irradiance at the top of the atmosphere is dependent on cloud optical depth as well as on solar zenith angle, but not on ground albedo for clouds of not very thin optical depth.     

长春地区紫外光谱（UV-A，UV-B）辐射观测和初步分析

利用我们研制的太阳—大气紫外光谱辐射计，从1992年5月在长春开始试验了野外观测，监视到达地表的太阳直射和大气散射紫外光谱辐射，主要给出长春地区地面紫外辐射，特别是紫外（UV）B段（280～320 nm）光谱辐射的一些基本特点和初步统计特征。由于地表UV-B辐射对生态系统和人类健康有危害作用，其强度随着臭氧减少而增加。该项观测分析将有助于监测和研究臭氧层变薄的实际效应。     

UV-B辐射增强对河南省夏直播花生产量及品质的影响

在大田条件下,研究了模拟地表UV-B辐射增强对花生（开农49号）的产量及品质的影响.UV-B辐射设3个水平,即对照、增强20%和增强40%.结果表明：UV-B辐射增强能显著降低花生产量,产量下降的原因主要是由单位面积产量、株荚果数、百仁重减少造成的;花生品质受UV-B影响较为复杂,UV-B增强20%时,花生脂肪质量分数为51.02%,蛋白质质量分数为22.34%,油酸/亚油酸质量比为1.19,较对照组提高了0.02;UV-B增强40%时,花生脂肪质量分数为51.82%,蛋白质质量分数为22.56%,油酸/亚油酸质量比为1.28,较对照组提高了0.11.研究认为,UV-B辐射增强,不足以对花生的品质产生显著影响,这可能与设定的UV-B辐射强度、试验设计方案及花生的品种有关.     

Impact of 3-D topography on surface radiation budget over the Tibetan Plateau

The 3-D complex topography effect on the surface solar radiative budget over the Tibetan Plateau is investigated by means of a parameterization approach on the basis of “exact” 3-D Monte Carlo photon tracing simulations, which use 90 m topography data as building blocks. Using a demonstrative grid size of 10?×?10 km², we show that differences in downward surface solar fluxes for a clear sky without aerosols between the 3-D model and the conventional plane-parallel radiative transfer scheme are substantial, on the order of 200 W/m² at shaded or sunward slopes. Deviations in the reflected fluxes of the direct solar beam amount to about +100 W/m² over snow-covered areas, which would lead to an enhanced snowmelt if the 3-D topography effects had been accounted for in current climate models. We further demonstrate that the entire Tibetan Plateau would receive more solar flux by about 14 W/m², if its 3-D mountain structure was included in the calculations, which would result in larger sensible and latent heat transfer from the surface to the atmosphere.     

支持向量机方法在南京太阳总辐射推算中的应用

利用1981、1996和2001年逐日南京站太阳总辐射和日照时数观测资料,建立了基于支持向量机(support vector machine,SVM)方法的太阳总辐射推算模型,预测了1982、1997和2002年的太阳总辐射,并把推算结果和采用线性的气候学方法所得到的推算结果分别与实测值进行对比。采用线性方法得到的1982、1997和2002年的太阳总辐射预测值与实测值间基于1:1线的决定系数(R~2)分别为0.800、0.859和0.838,均方根误差(RMSE)分别为3.250、2.649和2.925 MJ·m~(-2)·d~(-1)。采用SVM方法得到的1982、1997和2002年的R~2分别为0.894、0.938和0.936,RMSE分别为2.353、1.726和1.804 MJ·m~(-2)·d~(-1)。SVM方法得到的太阳总辐射预测值与实测值之间的误差较小,预测精度高于线性方法,更适用于实际太阳总辐射的计算。     

Determination of radiation amplification factor of atmospheric aerosol from the surface UV irradiance measurement at Gwangju, Korea

Summary This study investigated the impact of atmospheric aerosols on surface ultraviolet (UV) irradiance at Gwangju, Korea (35°13′N, 126°50′E). Data analyzed included surface UV irradiance measured by UV radiometers from June 1998 to April 2001 and the aerosol optical depth (AOD) in the visible range determined from a rotating shadow-band radiometer (RSR). The radiation amplification factor (RAF) of ozone for UV-B (280–315 nm) at Gwangju was 1.32–1.62. Values of the RAF of aerosols (RAF_AOD) for UV-A and UV-B were 0.18–0.20 and 0.22–0.26, respectively. Authors’ addresses: Jeong Eun Kim, Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute of Science and Technology (GIST) and Korea Meteorological Administration (KMA); Seong Yoon Ryu, Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute of Science and Technology (GIST) and Division of Metrology, Korea Research Institute of Standards and Science (KRISS); Young Joon Kim, Advanced Environmental Monitoring Research Center (ADEMRC) Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea.     

亚音速飞机排放物对地面紫外辐射的影响

根据世界民航组织和世界气象组织有关专家对当前亚音速飞机排放量的估计和将来20年内增长的预测,用辐射传输模式估算了飞机排放物对地面紫外辐射水平的影响。计算使用DISORT程序,这是一个经过检验可以较好地包括多次散射作用的离散坐标法程序。分别检验了飞机排放煤烟、硫酸盐粒子和卷云的多次散射及引起的臭氧增加对地面280～400 nm紫外辐射的影响。结果表明：根据目前的估计和预测,飞机排放的煤烟和硫酸盐粒子对地面紫外辐射没有影响;引起的臭氧变化也不至于引起地面紫外辐射的变化。但如果天空存在一层卷云（光学厚度0.042）,就足以使得地面直射紫外辐射减少5%,总紫外辐射增加1%～2%。有资料表明,飞机排放的水汽可能使得某些地区卷云量增加了10%。因此,可能会对地面紫外辐射产生影响。     

紫外辐射传输模式计算与实际测量的比较

利用改进的离散坐标法紫外辐射传输模式,应用各种可测得的实际大气物理参数,模拟了1993年7月24日德国加尔米希-帕特科琛（Garmisch-Partenkirchen,47.47oN, 11.07oE）地面紫外辐射的全天分布,并与1993年秋天第三次欧洲紫外辐射光谱仪比对活动期间通过了严格绝对标定的奥地利英斯布鲁克（Innsbruck）大学的紫外光谱仪的实际观测资料进行了比较,进行了余弦响应订正后,计算与测量的绝对值差别很小,最大误差对地面UVB通量（280～320 nm）是0.07 W/m2（正午的通量为3.2 W/m2）。对UVA（320～400 nm）最大误差是2.6 W/m2（正午通量为54 W/m2）。计算与测量的平均偏差为5%～13%,这表明,地面紫外辐射水平也可以利用其他大气观测资料通过模式计算间接得到。     

Ground-Based UV Measurements of BrO and OClO over Ny-Ålesund during Winter 1996 and 1997 and Andøya during Winter 1998/99

Presented here are measurements of BrO and OClO performed by ground-based UV-visible zenith-sky viewing spectrometers developed by the Norwegian Institute for Air Research (NILU). Measurements were taken at Ny-Ålesund, Spitsbergen (79° N, 11° E), in winter and spring1996 and 1997 and at Andøya (69.3° N, 16° E) from summer 1998 until summer 1999. AM and PM differential slant column densities (DSCDs) at 90°SZA of BrO and OClO reached their maxima during polar vortex conditions in the winter months and were anti-correlated to temperature andNO₂. Comparison of BrO with a 3-D chemical transport model showed good agreement for seasonal trends and non-vortex conditions. BrO AM/PM ratios were underestimated by the model for vortex conditions, indicating the need for better quantification of BrO source and sink reaction rates. The detection of OClO above 200 K at the 475 K isentropic level indicates the possible activation of chlorine on sulphate particles. Several episodes of boundary layer ozone depletion due to marine-derived BrO were evident in our zenith-skyspectra during April 1997 in Ny-Ålesund.     

紫外线辐射增加对大豆的影响及其估算

在田间及盆栽试验中观测到经超量紫外线（UV280～400 nm）辐射处理的大豆作物，其株型、生理活动及产量均受到不同程度的影响，其影响量随UV辐射强度，大豆品种以及环境条件不同而异。文章还给出了计算紫外线辐射对大豆影响程度的公式，该计算方法效果较好。     

基于宽带网的河南省太阳紫外线强度监测系统研究

使用自主研发的Gstar-Ⅱ型太阳紫外线监测仪,建立基于宽带网的河南省城市紫外线强度监测系统。太阳紫外线强度自动监测站将从紫外线传感器获得的气象要素信息传给本地专用计算机,进行数据处理和编码,然后通过互联网把数据信息送到数据业务中心站,数据业务中心站具有对接收数据进行初步处理和进库的功能;各级气象台站可以很方便地通过宽带Internet网WinSock协议进入数据处理中心,按照自己的要求调用全省紫外线强度历史和实时资料,为本地紫外线预报提供有力的科学依据和手段。     

UV-B辐射增强对不同品种花生结荚期生理特性日变化的影响

以3个花生品种（开农49号、64号和69号）为材料,通过大田模拟试验,研究UV-B辐射增强对花生结荚期叶片的净光合速率（P_n）、气孔导度（G_s）、胞间CO₂浓度（C_i）、蒸腾速率（T_r）和水分利用效率（E_wu）日变化的影响,为筛选高产、抗旱、抗UV-B辐射花生品种提供依据.UV-B辐射设2个水平即自然光（CK,1.5 kJ·m^-2）和UV-B增强20%（T,1.8 kJ·m^-2）.结果表明,UV-B辐射增强明显抑制花生的光合作用和蒸腾作用,与对照相比,UV-B增强条件下,开农49号、64号和69号P_n日均值分别降低19.4%、27.8%、24.7%;G_s日均值降低26.7%、42.9%、28.6%;C_i日均值降低27.2%、20.4%、23.1%;T_r日均值降低17.8%、23.3%、25.1%;E_wu日均值降低16.6%、23.2%、23.9%.UV-B辐射增强对3个品种生长都具有抑制效应,但品种间存在一定的敏感性差异,其中开农49号最不敏感,因此,开农49号在抗UV-B辐射方面比其他2个品种具有更大的优势.     

太阳紫外光谱及NO2光解系数的观测

本文讨论了利用自动太阳光谱仪测量地面的紫外辐射光谱,并进一步计算了NO_2的光分解系数.光谱测量范围为310—375nm.测量结果表明,在北京地区秋季NO_2的光解系数变化在(1—4)×10~(-3)S~(-1),有明显的日变化.