The characteristics of ultraviolet radiation in arid and semi-arid regions of China

Measurements of the broadband global solar radiation (R _S) and total ultraviolet radiation (the sum of UV-A and UV-B) were conducted from 2005 to 2010 at 9 sites in arid and semi-arid regions of China. These data were used to determine the temporal variability of UV and UV/R _S and their dependence on the water vapor content and clearness index. The dependence of UV/R _S on aerosol optical depth (AOD) and water vapor content was also investigated. In addition, a simple and efficient empirically model suited for all-weather conditions was developed to estimate UV from R _s. The annual average daily UV level in arid and semi-arid areas is 0.61 and 0.59 MJ m^?2 d^?1, respectively. The highest value (0.66?±?0.25 MJ m^?2 d^?1) was recorded at an arid area at Linze. The lowest value (0.53?±?0.22 MJ m^?2 d^?1) was recorded at a semi-arid area at Ansai. The highest daily value of UV radiation was measured in May, whereas the lowest value was measured in December. The monthly variation of the UV/R _s ratio ranged from 0.41 in Aksu to 0.35 in Qira. The monthly mean value of UV/R _s gradually increased from November and then decreased in August. A small decreasing trend of UV/R _s was observed in the arid and semi-arid regions due to recently increasing amounts of fine aerosol. A simple and efficient empirically model suit for all-weather condition was developed to estimate UV from R _s. The slope a and intercept b of the regression line between the estimated and measured values were close to 1 and zero, respectively. The relative error between the estimated and measured values was less than 11.5%. Application of the model to data collected from different locations in this region also resulted in reasonable estimates of UV.     

1960—2009年中国冬季区域性极端低温事件的时空特征

采用区域性极端低温事件客观识别技术对1960—2009年的区域性极端低温事件进行检测,并分析其空间分布和时间演变特征。结果表明：区域性极端低温事件指标中最低温度和几何中心纬度的频次分布为双峰特征,发生频次较高的纬度主要位于30°N和42°N附近,且1980年代中期以前南北两个带并存,之后则以30°N附近为主;1960—2009年事件的发生频次、强度和最大覆盖面积等呈总体减弱趋势,在1980年代后期存在显著的转折,1990年代后期变化逐渐趋于平缓,并且这种变化主要是由占总数10%的持续时间长和空间范围广的事件作用的结果。此外,对体现事件多方面影响的综合指标进行等级划分并分析其变化特征。     

洛阳市城市环境气象监测预报服务研究

利用洛阳市环境监测资料和气象资料,分析了洛阳市污染物浓度的日变化、季节变化、年际变化规律,并分析了污染物浓度与气象因子的关系。在此基础上,通过回归分析预报方法、污染潜势预报方法、CAPPS模式预报方法对洛阳市3种主要污染物的浓度和级别进行了24 h和48 h预测,并建立了气象局与环保部门共享的气象和污染数据库平台,为双方今后的合作奠定了基础。     

Quantifying Arctic contributions to climate predictability in a regional coupled ocean-ice-atmosphere model

The relative importance of regional processes inside the Arctic climate system and the large scale atmospheric circulation for Arctic interannual climate variability has been estimated with the help of a regional Arctic coupled ocean-ice-atmosphere model. The study focuses on sea ice and surface climate during the 1980s and 1990s. Simulations agree reasonably well with observations. Correlations between the winter North Atlantic Oscillation index and the summer Arctic sea ice thickness and summer sea ice extent are found. Spread of sea ice extent within an ensemble of model runs can be associated with a surface pressure gradient between the Nordic Seas and the Kara Sea. Trends in the sea ice thickness field are widely significant and can formally be attributed to large scale forcing outside the Arctic model domain. Concerning predictability, results indicate that the variability generated by the external forcing is more important in most regions than the internally generated variability. However, both are in the same order of magnitude. Local areas such as the Northern Greenland coast together with Fram Straits and parts of the Greenland Sea show a strong importance of internally generated variability, which is associated with wind direction variability due to interaction with atmospheric dynamics on the Greenland ice sheet. High predictability of sea ice extent is supported by north-easterly winds from the Arctic Ocean to Scandinavia.     

2001-2010年内蒙古空中水汽含量时空分布特征及变化趋势分析

利用2001年1月至2010年12月内蒙古地区12个探空站的资料,求算全区空中水汽含量,对其时空分布特征及变化趋势进行分析.分析结果表明,近10a来,1月份内蒙古地区月平均空中水汽含量最低只有0.303cm;7月份月平均空中水汽含量最大达到3.106cm;空中水汽含量高值区在河套地区有西凸的倾向;空中水汽含量和降水量分布有正相关关系;逐年平均空中水汽含量处于缓慢的减少过程中.     

福建沿海赤潮灾害气象预报

根据福建沿海2001～2008年赤潮灾害资料以及相应时期的气象数据,寻找与赤潮灾害发生密切相关的气象因子,分析赤潮灾害发生期间的地面及不同高度的天气形势,并探讨南方涛动指数与赤潮灾害发生的关系,在此基础上根据前期气温、风、云及海况进行福建沿海赤潮灾害气象预报。研究结果表明,福建沿海的风、气温、湿度、日照和气压等气象因子与赤潮的发生存在着密切的关系,但不同海区影响赤潮发生的主要气象因子不尽相同,低层850 hPa和地面形势能较好地反映福建沿海赤潮发生的天气背景,南方涛动指数与第2年赤潮发生日数有着很好的对应关系,二者相关系数为-0.745。     

豫西一次强对流天气过程的诊断分析

2010年9月4日凌晨,豫西地区出现罕见的强对流天气过程,造成严重损失.利用1°×1°的NCEP再分析资料、常规观测资料、卫星观测资料以及多普勒雷达资料,对此次过程进行诊断分析.结果表明,此次强对流天气过程中不仅具有明显的低层辐合、高层辐散的气流垂直运动,而且在多普勒雷达上有明显的辐合型中气旋存在.通过对垂直积分液态水...     

五道梁地区总辐射的年际变化

利用实测的太阳总辐射通量密度及地气温差资料，建立了月平均地气温差与月平均太阳总辐射通量密度的回归方程，并用该回归方程计算了五道梁地区1980-1993年共14年的月平均总辐射通量密度，分析了该地区总辐射通量密度的年际变化，发现该地区总辐射通量密度具有较明显的6～7年的振荡周期。20世纪后10年年平均总辐射通量密度有增大的趋势。     

A copula-based multivariate analysis of Canadian RCM projected changes to flood characteristics for northeastern Canada

In the present work, climate change impacts on three spring (March–June) flood characteristics, i.e. peak, volume and duration, for 21 northeast Canadian basins are evaluated, based on Canadian regional climate model (CRCM) simulations. Conventional univariate frequency analysis for each flood characteristic and copula based bivariate frequency analysis for mutually correlated pairs of flood characteristics (i.e. peak–volume, peak–duration and volume–duration) are carried out. While univariate analysis is focused on return levels of selected return periods (5-, 20- and 50-year), the bivariate analysis is focused on the joint occurrence probabilities P1 and P2 of the three pairs of flood characteristics, where P1 is the probability of any one characteristic in a pair exceeding its threshold and P2 is the probability of both characteristics in a pair exceeding their respective thresholds at the same time. The performance of CRCM is assessed by comparing ERA40 (the European Centre for Medium-Range Weather Forecasts 40-year reanalysis) driven CRCM simulated flood statistics and univariate and bivariate frequency analysis results for the current 1970–1999 period with those observed at selected 16 gauging stations for the same time period. The Generalized Extreme Value distribution is selected as the marginal distribution for flood characteristics and the Clayton copula for developing bivariate distribution functions. The CRCM performs well in simulating mean, standard deviation, and 5-, 20- and 50-year return levels of flood characteristics. The joint occurrence probabilities are also simulated well by the CRCM. A five-member ensemble of the CRCM simulated streamflow for the current (1970–1999) and future (2041–2070) periods, driven by five different members of a Canadian Global Climate Model ensemble, are used in the assessment of projected changes, where future simulations correspond to A2 scenario. The results of projected changes, in general, indicate increases in the marginal values, i.e. return levels of flood characteristics, and the joint occurrence probabilities P1 and P2. It is found that the future marginal values of flood characteristics and P1 and P2 values corresponding to longer return periods will be affected more by anthropogenic climate change than those corresponding to shorter return periods but the former ones are subjected to higher uncertainties.     

湖泊底泥疏浚环境效应:Ⅰ.内源磷释放控制作用

通过为期一年的疏浚模拟试验,在试验室培养疏浚与对照柱样研究了底泥疏浚对内源磷释放的控制效果．结果发现,疏浚表层30cm能够有效的消减沉积物中不f司形态磷含量与孔隙水中PO4^3-P含量．在一年的试验周期内,疏浚和对照柱沉积物-水界面的PO4^3-P通量分别为-143．8至14．4与-237．3至3047．6μg／（m^2·d）,疏浚柱沉积物-水界面的磷通量总体上低于未疏浚对照的磷通量,尤其是在温度较高的月份,从2006年3-10月疏浚柱沉积物-水界面磷释放通量显著低于未疏浚对照柱,疏浚沉积物的磷的释放潜力低于未疏浚对照沉积物．研究结果表明,在外源磷得到有效控制的前提下,底泥疏浚是消减研究区内源磷负荷有效的技术手段．