应用通量方差法估算戈壁绿洲下垫面湍流通量的研究

利用“绿洲系统能量与水分循环过程观测试验” 2005年绿洲、戈壁点的观测资料, 分析与讨论了温度、水汽的归一化标准差随稳定度变化的通量方差关系, 应用通量方差法对感热、 潜热通量进行了计算, 并同涡动相关系统的观测结果进行了比较。不稳定条件下, 戈壁点温度归一化标准差随稳定度变化的通量方差关系优于下垫面非均匀性更强的绿洲点, 绿洲点水汽的归一化标准差随稳定度变化的通量方差关系较温度量表现得更好。对同一站点, 归一化温度标准差的通量方差关系并不总是优于水汽的通量方差关系, 其取决于该站点的温度以及水汽的源汇分布情况; 通量方差法对两个站点的感热、 潜热通量均有较好的再现, 但戈壁点感热通量的计算效果优于非均匀性更强的绿洲点。应用通量方差法对潜热通量计算时若采用直接观测的感热通量, 则潜热通量的计算效果具有一定程度的改善。     

CAM3模式海气湍流通量参数化的改进及其应用

通过对流性阵风参数化方法,在CAM3原有海气湍流通量参数化方案(CAM3方案)中引入边界层自由对流和降水深对流对海表湍流通量的贡献,改进了CAM3模式的海气湍流通量参数化方案(CAM3 ME方案).在此基础上,利用观测海温积分改进的CAM3模式,分析改进模式对冬(DJF)、夏季(JJA)大气环流异常的模拟性能.结果表明,采用改进的海气湍流通量参数化方案,模式对冬(DJF)、夏季(JJA)大气环流异常年际变化的模拟能力有了很大提高,尤其是冬季(DJF)北太平洋和北美大陆地区以及夏季(JJA)南半球海洋上空.     

青藏高原西部地表通量的年、日变化特征

利用青藏高原西部地区改则和狮泉河两个自动观测气象站1998年全年每天24个时次的风速、温度和湿度等梯度观测资料,采用湍流相似理论．计算了改则和狮泉河的动量通量、感热通量以及潜热通量。结果表明：改则和狮泉河两地的地表湍流通量都具有明显的季节变化和日变化,且其季节变化的相同点表现在感热通量均在5月份最大,1月份最小：而潜热通量均在8月份最大。不同点表现在改则的潜热通量在12月份最小,狮泉河1～5月平均潜热通量为负,以凝结为主,改则的月平均蒸发及全年的蒸发总量比狮泉河的要大。而其感热通量比后者的都小。日变化幅度随季节变化明显,表现在夏季地表通量的日变化幅度大,冬季要小得多。     

青岛市海雾海气通量观测及其作用初探

概述１９９３年６月下旬－７月上旬在青岛市小麦岛东侧进行的风、温、湿梯度观测。其资料经迭代计算得到了黄海北部、青岛市近海平流雾季节海气间动量、热量和水汽的通量。并对７月１—２日的一个海雾过程进行了微物理分析。     

Countergradient Fluxes of Conserved Variables in the Clear convective and Stratocumulus-topped Boundary Layer: The role of the Entrainment Flux

Large-eddy simulations of a clear convective boundary layer (CBL)and a stratocumulus-topped boundary layer are studied. Bottom-upand a top-down scalars were included in the simulations, and theprinciple of linear superposition of variables was applied toreconstruct the fields of any arbitrary conserved variable.This approach allows a systematic analysis of countergradient fluxesas a function of the flux ratio, which is defined as the ratio betweenthe entrainment flux and the surface flux of the conserved quantity.In general, the turbulent flux of an arbitrary conserved quantityis counter to the mean vertical gradient if the heights where thevertical flux and the mean vertical gradient change sign do notcoincide. The regime where the flux is countergradient is thereforebounded by the so-called zero-flux and zero-gradient heights. Becausethe vertical flux changes sign only if the entrainment flux has anopposite sign to the surface flux, countergradient fluxes arepredominantly found for negative flux ratios. In the CBL the fluxratio for the virtual potential temperature is, to a good approximation,constant, and equal to -0.2. Only if the moisture contribution to thevirtual potential temperature is negligibly small will the flux ratio forthe potential temperature be equal to this value. Otherwise, theflux ratio for the potential temperature can have any arbitrary(negative) value, and, as a consequence, the fluxes for thepotential temperature and the virtual potential temperature willbe countergradient at different heights. As a practical application ofthe results, vertical profiles of the countergradient correction termfor different entrainment-to-surface-flux ratios are discussed.     

南亚高压强度的年代际变化及可能原因分析

利用NCEP/NCAR再分析资料和NOAA ERSST海温资料,对夏季南亚高压的年代际变化特征及其可能机制进行了分析。结果表明,南亚高压由弱到强的年代际转折发生在1970年代末,或者说南亚高压强度在1978年前后发生了年代际突变。对南亚高压偏弱和偏强两个阶段的对比分析表明,大气环流(包括风场、温度场和垂直运动场等)的异常形势和特征显著不同,几乎是相反的。夏季地表潜热通量异常的分析说明,夏季高原(特别是高原西北部)的地表热通量异常对南亚高压强度的年代际变化有重要影响;相对而言,地表感热通量异常可能对南亚高压强度的年代际变化起更重要作用。夏季热带印度洋海温的全区一致型模态在1970年代末也发生了明显的年代际变化,与南亚高压强度的年代际异常有很好的一致性,表明夏季热带印度洋海温一致型模态异常对南亚高压年代际变化有影响。      

Characteristics of Lake Breezes and Their Impacts on Energy and Carbon Fluxes in Mountainous Areas

In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(F_{CO_2}) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_{CO_2}. For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange.     

IMPACT OF LATENT HEAT FLUX ON INDIAN SUMMER MONSOON DURING EL NI(N)O/LA NI(N)A YEARS

El Ni(n)o or La Ni(n)a manifest in December over the Pacific and will serve as an index for the forecasting of subsequent Indian summer monsoon,which occurs from June to mid-September.In the present article,an attempt is made to study the variation of latent heat flux (LHF) over the north Indian Ocean during strong El Ni(n)o and strong La Ni(n)a and relate it with Indian monsoon rainfall.During strong El Ni(n)o the LHF intensity is higher and associated with higher wind speed and lower cloud amount.During E1 Ni(n)o all India rainfall is having an inverse relation with LHF.Seasonal rainfall is higher in YY+1 (subsequent year) than YY (year of occurrence).However there is a lag in rainfall during El Ni(n)o YY+1 from June to July when compared with the monthly rainfall.     

2002/2003年与2003/2004年冬季爆发性增温期间的动力特征

利用ECMWF提供的60层气象场资料诊断分析了2002/2003和2003/2004年两个冬季的爆发性增温(stratospheric sudden warming,SSW)过程,比较了两次SSW期间高纬温度和纬向风的差异,计算了SSW期间的EP通量和剩余环流.结果表明:2003/2004年增温持续时间长、强度大,而2002/2003年则发生了波动;增温都是从平流层上层开始向下传播,但是2003/2004年高层极涡崩溃后迅速恢复,低层极涡恢复得慢,2002/2003年极涡在高层和低层都是缓慢恢复;SSW期间行星渡活动较多,2003/2004年极地EP通量的辐合引起东风长时间持续从而阻止了行星渡再次上传,而2002/2003年行星波则发生多次上传;2002/2003年SSW发生时高纬地区为下沉气流,没有形成环流圈,增温后形成逆时针的环流圈比2003/2004年偏低.     

甘肃东部一次暴雪过程的诊断分析和数值模拟

应用NCEP1°×1°的6 h再分析资料和常规气象观测资料以及RUC模式高分辨资料,对2013年2月17日甘肃河东暴雪天气从天气实况、环流特征、水汽条件、动力条件及西北区域RUC模式输出的模拟结论进行了诊断分析。结果表明：高空冷槽、700 hPa低涡、地面冷锋是这次暴雪的主要影响系统;降雪前期,低层正涡度增强,低层辐合、高层辐散是暴雪发生的动力机制;降雪前期,由于低涡辐合作用,700 hPa高度以下,湿度猛增,为降雪提供了充沛的水汽条件;降雪中心和政上空有θse密集强能量锋区;西北区域RUC模式模拟的24 h内降水量范围、落区、量级与实况一致,模拟的地面风速偏大。