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本文用新的边界层顶垂直速度参数化方案研究了当地形和边界层摩擦同时存在时二者对Eady波不稳定性的影响,得到了边界层层结、地面粗糙度、地形坡度的影响,还研究了摩擦和地形对一般化Eady波不稳定性的影响。 相似文献
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SST日变化对西太平洋暖池海表热通量季节内变化的影响(英文) 总被引:2,自引:0,他引:2
基于利用日最大太阳辐射、日平均海面风和日降水量近似计算海表温度(SST)日变化的振幅的方法,发展了一个计算SST日循环的参数化方案。利用周平均SST强迫美国国家大气研究中心(NCAR)的CCM3大气模式进行了有、无考虑SST日变化的比较试验。热带海洋与全球大气计划之耦合海气响应实验(TOGA COARE)的强化观测期间 IMET浮标的逐时海表观测资料不仅验证了该参数化方案的合理性,也表明了利用参数化方案对强迫场SST迭加日变化使CCM3较真实地模拟出西太平洋暖池海表热通量的季节内变化的位相结构。 相似文献
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SST日变化对西太平洋暖池海表热通量季节内变化的影响 总被引:1,自引:0,他引:1
基于利用日最大太阳辐射、日平均海面风和日降水量近似计算海表温度(SST)日变化的振幅的方法,发展了一个计算SST日循环的参数化方案。利用周平均SST强迫美国国家大气研究中心(NCAR)的CCM3大气模式进行了有、无考虑SST日变化的比较试验。热带海洋与全球大气计划之耦合海气响应实验(TOGA COARE)的强化观测期间IMET浮标的逐时海表观测资料不仅验证了该参数化方案的合理性,也表明了利用参数化方案对强迫场SST迭加日变化使CCM3较真实地模拟出西太平洋暖池海表热通量的季节内变化的位相结构。 相似文献
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利用中国科学院寒区旱区环境与工程研究所那曲高寒气候与环境观测研究站的BJ观测站2012年1 12月大气湍流观测资料及自动气象站观测资料,应用一种独立的确定地表动力学粗糙度Z0m的方法及两种热力学粗糙度Z0h的参数化方案(Z98和Y07),得出了Z0m和Z0h以及附加阻尼kB-1的变化规律。结果表明,Z0m在一定时间尺度(月、季)上存在着波动,Z0h在高原季风前、盛行期、衰退期有不同的日变化和季节变化特征。结合陆面模式CoLM将地表特征参数代入该模式进行数值模拟,初步探讨了地表粗糙度的变化规律及其对地表通量的影响,结果表明,Z0m的动态变化和Z0h参数化方案的改进提高了CoLM模式的模拟性能,模拟的地表通量更接近观测值。 相似文献
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在求解含有运动方程、湍流动能平衡与耗散方程的闭合方程组基础上,考虑大气与海洋之间的相互作用,模拟其边界层中的过程。在建立表达式时,考虑了风浪对大气和海洋湍流垂直结构的影响,引入依赖外部因子的湍流参数的垂直分布。指出,随着波高的增长,最大湍流系数移向海面。并得出,动力速度、粗糙度及其与波高的比等,均与近海面的风速有关,这些均与实验资料相符合。提供了根据天气船观测资料进行模式计算的典型个例。 相似文献
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利用2013年7月1日至2014年6月30日鄱阳湖东岸70 m铁塔涡动相关观测资料,应用Martano方法和TVM(Temperature Variance Method)方法分别计算了该地地表零平面位移d和粗糙度z0,通过代回Monin-Obukhov相似性理论的风廓线关系计算摩擦速度,以验证与实测摩擦速度的一致性。速度和温度标准差的归一化拟合线分别与Panosky等和Tillman给出的曲线趋势一致,表明该站观测数据总体满足近地层相似性。Martano方法计算结果随季节变化较大,春夏季的粗糙度是秋冬季的6.3倍;陆面方向零平面位移和粗糙度分别为来自湖面的2倍和10倍;Martano方法比TVM方法对季节和方向的敏感性更强。Martano方法计算得到零平面位移和粗糙度对摩擦速度造成了约9.9%的高估;而TVM方法对摩擦速度造成了约32.8%的高估;Martano方法计算的摩擦速度和观测值的一致性更好。 相似文献
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SAMIL大气环流模式海面湍流通量参数化方案研究 总被引:1,自引:1,他引:0
将中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的大气环流谱模式SAMIL_R42L26 2.08中的海气通量参数化方案——Louis方案, 与新发展的一种新型近海层湍流通量参数化方案——LGLC方案进行比较和分析。离线测试结果表明, LGLC方案计算的通量结果与观测数据具有更好的一致性, 且由于其区分热力粗糙度和动力粗糙度, 使得对热量通量的计算更加准确。在线测试则证明, 引入LGLC方案的SAMIL模式对洋面风应力、 感热通量、 潜热通量和降水率的模拟能力有了进一步的提高, 尤其对北半球夏季印度季风和南海季风区的降水改善明显。 相似文献
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利用2006年南京地区边界层外场观测资料对摩擦速度(u*)和摩擦温度(θ*)的几种计算方案进行了比较.u*计算方案的比较结果表明:在不稳定条件下,Pleim方案计算结果同实测值相比,二者在量值及变化趋势上都有较好的一致性;而在稳定条件下,计算结果较差,为此本文给出了一个新的计算方案,结果表明,改进方案有效的提高了u*计算精度,平均相对误差由56%降低到21%.θ*计算方案的比较结果表明:基于动力粗糙度和热力粗糙度相等的Lee方案计算误差较大,而引入阻尼项的Wesely方案计算结果较前者有明显改进. 相似文献
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In this paper,the observational data from Marine and Meteorological Observation Platform(MMOP)at Bohe,Maoming and buoys located in Shanwei and Maoming are used to study the characteristics of air-sea temperature and specific humidity difference and the relationship between wind and wave with the tropical cyclones over the South China Sea(SCS).The heat and momentum fluxes from eddy covariance measurement(EC)are compared with these fluxes calculated by the COARE 3.0 algorithm for Typhoon Koppu.The results show that at the developing and weakening stages of Koppu,both these differences between the sea surface and the near-surface atmosphere from the MMOP are negative,and data from the buoys also indicate that the differences are negative between the sea surface and near-surface atmosphere on the right rear portion of tropical cyclones(TCs)Molave and Chanthu.However,the differences are positive on the left front portion of Molave and Chanthu.These positive differences suggest that the heat flux is transferred from the ocean to the atmosphere,thus intensifying and maintaining the two TCs.The negative differences indicate that the ocean removes heat fluxes from the atmosphere,thus weakening the TCs.The wind-wave curves of TCs Molave and Chanthu show that significant wave height increases linearly with 2-min wind speed at 10-m height when the wind speed is less than 25 m/s,but when the wind speed is greater than 25 m/s,the significant wave height increases slightly with the wind speed.By comparing the observed sensible heat,latent heat,and friction velocity from EC with these variables from COARE 3.0 algorithm,a great bias between the observed and calculated sensible heat and latent heat fluxes is revealed,and the observed friction velocity is found to be almost the same as the calculated friction velocity. 相似文献
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Wave-dependence of friction velocity,roughness length,and drag coefficient over coastal and open water surfaces by using three databases 总被引:3,自引:0,他引:3
The parameterization of friction velocity, roughness length, and the drag coefficient over coastal
zones and open water surfaces enables us to better understand the physical processes of air-water interaction.
In context of measurements from the Humidity Exchange over the Sea Main Experiment (HEXMAX), we recently proposed
wave-parameter dependent approaches to sea surface friction velocity and the aerodynamic roughness by using the
dimensional analysis method. To extend the application of these approaches to a range of natural surface conditions,
the present study is to assess this approach by using both coastal shallow (RASEX) and open water surface measurements
(Lake Ontario and Grand Banks ERS-1 SAR) where wind speeds were greater than 6.44 m s-1. Friction velocities,
the surface aerodynamic roughness, and the neutral drag coefficient estimated by these approaches under moderate wind
conditions were compared with the measurements mentioned above. Results showed that the coefficients in these approaches
for coastal shallow water surface differ from those for open water surfaces, and that the aerodynamic roughness length
in terms of wave age or significant wave height should be treated differently for coastal shallow and open water surfaces. 相似文献
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Aerodynamic roughness of the sea surface at high winds 总被引:2,自引:0,他引:2
The role of the surface roughness in the formation of the aerodynamic friction of the water surface at high wind speeds is
investigated. The study is based on a wind-over-waves coupling theory. In this theory waves provide the surface friction velocity
through the form drag, while the energy input from the wind to waves depends on the friction velocity and the wind speed.
The wind-over-waves coupling model is extended to high wind speeds taking into account the effect of sheltering of the short
wind waves by the air-flow separation from breaking crests of longer waves. It is suggested that the momentum and energy flux
from the wind to short waves locally vanishes if they are trapped into the separation bubble of breaking longer waves. At
short fetches, typical for laboratory conditions, and strong winds the steep dominant wind waves break frequently and provide
the major part of the total form drag through the air-flow separation from breaking crests, and the effect of short waves
on the sea drag is suppressed. In this case the dependence of the drag coefficient on the wind speed is much weaker than would
be expected from the standard parameterization of the roughness parameter through the Charnock relation. At long fetches,
typical for the field, waves in the spectral peak break rarely and their contribution to the air-flow separation is weak.
In this case the surface form drag is determined predominantly by the air-flow separation from breaking of the equilibrium
range waves. As found at high wind speeds up to 60 m s−1 the modelled aerodynamic roughness is consistent with the Charnock relation, i.e. there is no saturation of the sea drag.
Unlike the aerodynamic roughness, the geometrical surface roughness (height of short waves) could be saturated or even suppressed
when the wind speed exceeds 30 m s−1. 相似文献
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The atmospheric surface layer over sea has a density stratification which varies with moisture content and air/sea temperature difference. This influences the growth of water waves. To study the effect quantitatively, the Reynolds equations are solved numerically. For given wind speed and surface roughness, wave growth is found to be more rapid in unstably stratified conditions than in stable conditions. This is due to an increase in turbulence, primarily caused by an increase of mixing length.Under the assumption of a Charnock relation between surface roughness and friction velocity, it is found that for large inverse wave age (u
*/c>0.07), the effect of stratification on wave growth is weell described by Monin-Obukhov scaling of the friction velocity. For smaller values ofu
*/c, Monin-Obukhov scaling overpredicts.The effect on duration-limited wave growth is studied with the third-generation WAM surface wave model driven by 10 m winds. Effects of stratification on the significant wave height are found to be of the order of 10%. The results are comparable to those of a recent reanalysis of field measurements, although the measured stratification effect is somewhat stronger. Implementation of a stratification-dependent growth in wave models is recommended, as it can lead to small but significant improvements in wave forecasts when accurate air and sea temperatures are available. 相似文献
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P. A. Taylor 《Boundary-Layer Meteorology》1972,2(3):381-389
Results are presented from a numerical experiment of wind and shear stress profile development away from a shore line; the water surface is assumed to obey the Charnock-Ellison relation between surface roughness and friction velocity. In typical cases the upwind, land surface is rough relative to the sea and the velocity and shear stress results are qualitatively similar to those for flows from relatively rough to relatively smooth solid surfaces. In the present case, however, the downwind surface roughness and friction velocity vary with position and we find that wind profile development may play a significant role in the relationship between sea surface roughness and fetch. 相似文献
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M. Segal 《Boundary-Layer Meteorology》1990,52(1-2):193-198
Calculations are made of the effects of thermal stability under a range of conditions, over the sea and land, on the physical factors (including the critical wind speed) affecting dust-storm generation, snow drift, and rough sea conditions. The computational procedure involves the surface friction velocity, u
*, and its relation with the aerodynamic roughness over aerodynamically rough, mobile surfaces. The results indicated that even at relatively high wind speeds, thermal effects under extreme advection situations may be significant, particularly for those properties of the agitated surface dependent on u
*
3 and u
*
4. 相似文献
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Development and Validation of an Evaporation Duct Model.Part Ⅰ:Model Establishment and Sensitivity Experiments 总被引:1,自引:0,他引:1
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Based on the Coupled Ocean-Atmospheric Response Experiment(COARE)bulk algorithm and the Naval Postgraduate School(NPS)model,a universal evaporation duct(UED)model that can flexibly accommodate the latest improvements in component(such as stability function,velocity roughness,and scalar roughness)schemes for different stratification and wind conditions,is proposed in this paper.With the UED model,the sensitivity of the model-derived evaporation duct height(EDH)to stability function(Ψ),ocean wave effect under moderate to high wind speeds,and scalar roughness length parameterization,is investigated,and relative contributions of these factors are compared.The results show that the stability function is a key factor influencing the simulated EDH values.Under unstable conditions,the EDH values from stability functions of Fairall et al.(1996)and Hu and Zhang(1992)are generally higher than those from others;while under stable conditions,unreasonably high EDHs can be avoided by use of the stability functions of Hu and Zhang(1992)and Grachev et al.(2007).Under moderate to high wind speeds,the increase in velocity roughness length z0 due to consideration of the true ocean wave effect acts to reduce modeled EDH values;this trend is more pronounced under stable conditions.Although the scalar roughness length parameterization has a minor effect on the model-derived EDH,a positive correlation is found between the scalar roughness length z0qand the model-derived EDH. 相似文献
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利用2010年古浪近地层野外观测试验取得的干旱区典型下垫面(荒滩、沙漠和农田)的观测资料,对常用的3种空气动力学阻抗算法——Verma—R算法、Liu算法、Thom算法进行了适用性检验,并通过分离Thom算法中的动量和热量粗糙度对其进行改进(下称Thom-2算法)。对比不同下垫面空气动力学阻抗估算结果发现:在沙漠和荒滩下垫面,动力因素较热力因素影响大,空气动力学阻抗与风速的指数关系较农田下垫面明显;与其他3种算法相比,考虑了热量粗糙度的Thom-2算法在各种典型下垫面上的估算结果与观测值相比偏差最小,且在较为均匀的荒滩和沙漠下垫面上估算的空气动力学阻抗精度较农田高;通过比较4种算法估算干旱区不同典型下垫面空气动力学阻抗结果,说明干旱区空气动力学阻抗的估算应考虑热力粗糙度的影响。 相似文献