共查询到20条相似文献，搜索用时 84 毫秒
1.
To investigate the impacts of solar radiation on tropical cyclone (TC) warm-core structure (i.e., the magnitude and height), a pair of idealized simulations are conducted by specifying different strengths of solar shortwave radiation. It is found that the TC warm core is highly sensitive to the shortwave radiative effect. For the nighttime storm, a tendency for a more intense warm core is found, with an elevated height compared to its daytime counterpart. As pointed out by previous studies, the radiative cooling during nighttime destabilizes the local and large-scale environment and thus promotes deep moist convection, which enhances the TC's intensity. Due to the different inertial stabilities, the diabatic heating in the eyewall will force different secondary circulations. For a strong TC with a deeper vertical structure, this promotes a thin upper-level inflow layer. This inflow carries the lower stratospheric air with high potential temperature and descends adiabatically in the eye, resulting in significant upper-level warming. The Sawyer-Eliassen diagnosis further confirms that the height of the maximum temperature anomaly is likely attributable to the balance among the forced secondary circulations. 相似文献
2.
Based on idealized numerical simulations, the impacts of the diurnal cycle of solar radiation on the diurnal variation of outer rainbands in a tropical cyclone are examined. It is found that cold pools associated with precipitation-driven downdrafts are essential for the growth and propagation of spiral rainbands. The downdrafts result in surface outflows, which act as a lifting mechanism to trigger the convection cell along the leading edge of the cold pools. The diurnal cycle of solar radiation may modulate the diurnal behavior of the spiral rainbands. In the daytime, shortwave radiation will suppress the outer convection and thus weaken the cold pools. Meanwhile, the limited cold pool activity leads to a strong modification of the moisture field, which in turn inhibits further convection development. 相似文献
3.
已有研究表明辐射对热带气旋发生发展具有明显调制作用,高原涡与热带气旋有类似的暖心低压结构,辐射在高原涡发生发展过程中的作用也值得探讨。本文利用ERA-Interim再分析资料,通过中尺度数值模式WRF-ARW研究了辐射日变化对高原涡个例发展的影响机制。模拟结果表明,太阳短波辐射对高原涡的发生发展具有明显的调制作用。控制试验（CTL;即保留太阳辐射日变化）较好的再现了高原涡的发展过程。在去掉短波辐射过程的夜间试验（All_night）中,前期高原涡发展速度较快。而在白天（All_day）试验中,短波辐射过程抑制了高原涡的发展。诊断分析表明,夜间长波辐射冷却加强对流层温度递减率,减弱大气静力稳定度;同时,大气温度的降低使得夜间相对湿度增大,有利于对流层低层出现位势不稳定,进而促使高原涡的形成和发展。反之,太阳短波辐射有利于对流层高层增温,加强大气静力稳定度,从而抑制对流活动发展。夜间低层辐合更为强盛,有利于上升运动的加强并诱发高原涡形成;非平衡项结果显示,在高原涡环流中心区域存在正值区,而低涡四周为明显的负值区。从动力学和热力学特征来看,高原涡的发展与热带气旋具有一定的相似性。 相似文献
4.
Myong-In Lee Ildae Choi Wei-Kuo Tao Siegfried D. Schubert In-Sik Kang 《Climate Dynamics》2010,34(2-3):419-437
The mechanisms of summertime diurnal precipitation in the US Great Plains were examined with the two-dimensional (2D) Goddard Cumulus Ensemble (GCE) cloud-resolving model (CRM). The model was constrained by the observed large-scale background state and surface flux derived from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program’s Intensive Observing Period (IOP) data at the Southern Great Plains (SGP). The model, when continuously-forced by realistic surface flux and large-scale advection, simulates reasonably well the temporal evolution of the observed rainfall episodes, particularly for the strongly forced precipitation events. However, the model exhibits a deficiency for the weakly forced events driven by diurnal convection. Additional tests were run with the GCE model in order to discriminate between the mechanisms that determine daytime and nighttime convection. In these tests, the model was constrained with the same repeating diurnal variation in the large-scale advection and/or surface flux. The results indicate that it is primarily the surface heat and moisture flux that is responsible for the development of deep convection in the afternoon, whereas the large-scale upward motion and associated moisture advection play an important role in preconditioning nocturnal convection. In the nighttime, high clouds are continuously built up through their interaction and feedback with long-wave radiation, eventually initiating deep convection from the boundary layer. Without these upper-level destabilization processes, the model tends to produce only daytime convection in response to boundary layer heating. This study suggests that the correct simulation of the diurnal variation in precipitation requires that the free-atmospheric destabilization mechanisms resolved in the CRM simulation must be adequately parameterized in current general circulation models (GCMs) many of which are overly sensitive to the parameterized boundary layer heating. 相似文献
5.
利用2001-2012年MODIS地表温度资料,分析了三峡库区蓄水后水体对冬、夏两季白天和夜间地表温度的影响。由于下垫面水陆和地势的影响,白天地表温度高值区主要位于四川盆地东部,夜间则主要出现在长江江面;温度日较差在长江和海拔较高地区较小,且夏季水体日较差小于冬季。分别用水体和I～X缓冲区地表温度减去XI缓冲区去除气候背景场影响,发现冬季白天地表温度趋势在水体及I～VI缓冲区由下降转为上升,夜间地表温度在相同距离内显著升高。利用蓄水后（2003-2012年）地表温度或日较差分别减去蓄水前（2001-2002年）剔除地形影响,发现：冬季,三峡工程水库蓄水对局地地表温度具有增温效果,且强度和范围夜间大于白天;夏季,对地表温度有降温作用,白天大于夜间;同时,冬、夏季的温度日较差减小;且水体对局地地表温度和日较差的影响随距水体距离的增加而减小,其影响范围基本维持在0～8 km范围内。 相似文献
6.
We examine the climatological diurnal cycle of surface air temperature in a 6 km resolution atmospheric simulation of Southern California from 1995 to the present. We find its amplitude and phase both have significant geographical structure. This is most likely due to diurnally-varying flows back and forth across the coastline and elevation isolines resulting from the large daily warming and cooling over land. Because the region’s atmosphere is generally stably stratified, these flow patterns result in air of lower (higher) potential temperature being advected upslope (downslope) during daytime (nighttime). This suppresses the temperature diurnal cycle amplitude at mountaintops where diurnal flows converge (diverge) during the day (night). The nighttime land breeze also advects air of higher potential temperature downslope toward the coast. This raises minimum temperatures in land areas adjacent to the coast in a manner analogous to the daytime suppression of maximum temperature by the cool sea breeze in these same areas. Because stratification is greater in the coastal zone than in the desert interior, these thermal effects of the diurnal winds are not uniform, generating spatial structures in the phase and shape of the temperature diurnal cycle as well as its amplitude. We confirm that the simulated characteristics of the temperature diurnal cycle as well as those of the associated diurnal winds are also found in a network of 30 observation stations in the region. This gives confidence in the simulation’s realism and our study’s findings. Diurnal flows are probably mainly responsible for the geographical structures in the temperature diurnal cycle in other regions of significant topography and surface heterogeneity, their importance depending partly on the degree of atmospheric stratification. 相似文献
7.
中国西北干旱区戈壁下垫面夏季的热力输送 总被引：6，自引：1，他引：5
以敦煌戈壁站2004年6月和2008年8月的常规观测和超声观测为例,分析了西北干旱区戈壁下垫面夏季热力输送的一般过程及特征。首先评价了湍流通量的观测质量以及仪器观测的地表能量通量闭合问题,结果表明敦煌戈壁站的观测在白天总体较好。夏季地表能量通量的平均日变化显示,潜热通量整天都很小,可以忽略,白天到达地表的短波辐射以及地表向上的长波辐射非常强,地表净辐射主要转化为感热输送（敦煌戈壁站在中午时平均分别达380W·m-2以上和250W·m-2以上）;夜间土壤释放热量以平衡地表的辐射冷却,感热通量略低于0。白天时地表大气经常触发自由对流活动,影响动量通量的观测质量,并有效输送地表热力至上层大气中,有助于形成超厚大气边界层。分析了戈壁下垫面的动量粗糙度特征和热力粗糙度特征（敦煌戈壁站动量粗糙度约为0．6mm）,热力粗糙度基本小于动量粗糙度一个量级,这符合目前对干旱区戈壁下垫面热力输送特征的初步认识。 相似文献
8.
Diurnal and Seasonal Variations of Thermal Stratification and Vertical Mixing in a Shallow Fresh Water Lake 总被引：1，自引：0，他引：1
Yichen Yang Yongwei Wang Zhen Zhang Wei Wang Xia Ren Yaqi Gao Shoudong Liu Xuhui Lee 《Acta Meteorologica Sinica》2018,32(2):219-232
Among several influential factors, the geographical position and depth of a lake determine its thermal structure. In temperate zones, shallow lakes show significant differences in thermal stratification compared to deep lakes. Here, the variation in thermal stratification in Lake Taihu, a shallow fresh water lake, is studied systematically. Lake Taihu is a warm polymictic lake whose thermal stratification varies in short cycles of one day to a few days. The thermal stratification in Lake Taihu has shallow depths in the upper region and a large amplitude in the temperature gradient, the maximum of which exceeds 5°C m–1. The water temperature in the entire layer changes in a relatively consistent manner. Therefore, compared to a deep lake at similar latitude, the thermal stratification in Lake Taihu exhibits small seasonal differences, but the wide variation in the short term becomes important. Shallow polymictic lakes share the characteristic of diurnal mixing. Prominent differences on the duration and frequency of long-lasting thermal stratification are found in these lakes, which may result from the differences of local climate, lake depth, and fetch. A prominent response of thermal stratification to weather conditions is found, being controlled by the stratifying effect of solar radiation and the mixing effect of wind disturbance. Other than the diurnal stratification and convection, the representative responses of thermal stratification to these two factors with contrary effects are also discussed. When solar radiation increases, stronger wind is required to prevent the lake from becoming stratified. A daily average wind speed greater than 6 m s–1 can maintain the mixed state in Lake Taihu. Moreover, wind-induced convection is detected during thermal stratification. Due to lack of solar radiation, convection occurs more easily in nighttime than in daytime. Convection occurs frequently in fall and winter, whereas long-lasting and stable stratification causes less convection in summer. 相似文献
9.
In this paper the impacts of vertical resolution on the simulations of Typhoon Talim (2005) are examined using the Weather Research and Forecasting (WRF) model, with cumulus parameterization scheme representing the cumulus convection implicitly. It is shown that the tropical cyclone (TC) track has little sensitivity to vertical resolution, whereas the TC intensity and structure are highly sensitive to vertical resolution. It is partly determined by the sensitivity of the planetary boundary layer (and the surface layer) and the cumulus convection processes to vertical resolution. Increasing vertical resolution in the lower layer could strengthen the TC effectively. Increasing vertical resolution in the upper layer is also beneficial for the storm intensification, but to a lesser degree. In contrast, improving the midlevel resolution may cause the convergence of environmental air, which inhibits the TC intensification. The results also show that the impacts of vertical resolution on features of the TC structure, such as the tangential winds, secondary circulations and the evolution of the warm-core structure, are consistent with the impacts on the TC intensity. It is suggested that in the simulations of TCs, the vertical levels should be distributed properly rather than the more the better, with higher vertical resolution being expected both in the lower and upper layer, while the middle layer should not hold too many levels. 相似文献
10.
Chunlei Meng 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(3):327-338
In a surface urban heat island (SUHI), the urban land surface temperature (LST) is usually higher than the temperature of the surrounding rural areas due to human activities and surface characteristics. Because a SUHI has many adverse impacts on urban environment and human health, SUHI mitigation strategies are very important. This paper investigates the mechanism of a SUHI based on the basic physical laws that control the formation of a SUHI; five mitigation strategies are proposed, namely: sprinkling and watering; paving a pervious surface; reducing the anthropogenic heat (AH) release; using a “white roof”; increasing the fractional vegetation cover or leaf area index (LAI). To quantify the effect of these mitigation strategies, 26 sets of experiments are designed and implemented by running the integrated urban land model (IUM). The results of the sensitivity analysis indicate that sprinkling and watering is an effective measure for mitigating a SUHI for an entire day. Decreasing the AH release is also useful for both night- and daytime SUHI mitigation; however, the cooling extent is proportional to the diurnal cycle of AH. Increasing the albedo can reduce the LST in the daytime, especially when the solar radiation is significant; the cooling extent is approximately proportional to the diurnal cycle of the net radiation. Increasing the pervious surface percentage can mitigate the SUHI especially in the daytime. Increasing the fractional vegetation cover can mitigate the SUHI in the daytime but may aggravate the SUHI at night. 相似文献
11.
The validity of a spectral cumulus parameterization (spectral scheme) for simulating a diurnal cycle of precipitation over the Maritime Continent (MC) was examined using a regional atmospheric model. The impacts of entrainment parameterization and each type of convective closure, i.e., non-equilibrium (or equilibrium) closure for deep convection, mid-level, and shallow convective closures, were also examined. When vertically variable entrainment and appropriate convective closures were employed, the model adequately simulated a diurnal cycle of precipitation over both land and ocean as compared to the observation. Analysis regarding the entrainment parameterization revealed that variable entrainment parameterization was needed not only for simulating better mean patterns of precipitation, but also for more realistic phases of diurnal cycles. The impacts of convective closures appeared in the differences in the precipitation amplitude. Analysis on diurnal cycles of convective properties and tendencies revealed that the cycles between boundary layer forcing and convective heating determined convection strength and were affected by each type of convective closure. It can be concluded that the spectral scheme with appropriate convective closures is able to simulate a realistic diurnal cycle over the MC. 相似文献
12.
The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variations are remarkably different.The variability of the instant flux in the afternoon is much larger than in the nighttime.The afternoon and nighttime flux anomalies tend to be opposite.The diurnal and seasonal dependence of sensible heat flux variations is closely related to the diurnal cycle of mean land-air temperature difference.The relationship of sensible heat flux with land-air temperature difference based on the instant value differs from that based on the daily mean.The present study indicates the importance for the models to properly simulate mean land-air temperature difference and its diurnal and seasonal variations in order to capture surface sensible heat flux variability over Northwest China and predicts its plausible impacts on climate. 相似文献
13.
利用塔克拉玛干沙漠北缘肖塘陆气相互作用观测站2009年8-10月探测的资料,对该地区能量收支状况进行了初步分析。结果表明：2009年8-10月的平均能量闭合率为78%,闭合差为22%。夏季白天,感热、潜热、土壤热通量各占净辐射的52%、6%、16%,夜间依次占净辐射的53%、3%、6%。夏季白天、夜间能量不平衡率分别为26%、38%。8月肖塘的总体输送系数CD平均值为4.5×10-3,CH为2.2×10-3。CD、CH季节变化和日变化显著,都是夏季大于秋季,白天大,夜间小。 相似文献
14.
The effects of sea surface temperature(SST) and its diurnal variation on diurnal variation of rainfall are examined in this study by analyzing a series of equilibrium cloud-resolving model experiments which are imposed with zero large-scale vertical velocity.The grid rainfall simulation data are categorized into eight rainfall types based on rainfall processes including water vapor convergence/divergence,local atmospheric drying/moistening,and hydrometeor loss/convergence or gain/divergence.The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the increase in SST from 27°C to 29°C during the nighttime,whereas they are decreased during the daytime.The rainfall contributions of the rainfall types with water vapor convergence are decreased as the SST increases from 29°C to 31°C but the decreases are larger during the nighttime than during the daytime.The rainfall contributions of the rainfall types with water vapor convergence are decreased by the inclusion of diurnal variation of SST with diurnal difference of 1°C during the nighttime,but the decreases are significantly slowed down as the diurnal difference of SST increases from 1°C to 2°C.The rainfall contributions of the rainfall types with water vapor convergence are insensitive to the inclusion of diurnal variation of SST during the daytime. 相似文献
15.
针对2004年5月26日-2005年10月15日盘锦湿地芦苇生态系统碳通量、感热通量和潜热通量资料进行分析。结果表明:芦苇湿地具有较强的碳汇作用;2005年芦苇湿地固定二氧化碳为13.32 t/hm2,日平均感热通量和潜热通量分别为2 464 kJ/m2和3 880 kJ/m2。2004年和2005年6～9月的日累积值波文比平均值均为0.15。芦苇湿地碳通量、感热通量和潜热通量的日动态呈单峰单谷型变化,极值出现在中午前后,夜间线形平直。芦苇生长季白天通量绝对值远较夜间大,白天碳吸收,夜间碳排放。CO2浓度年平均日变化曲线亦为单谷单峰型,夜间浓度较高且逐渐升高,直到日出前达到峰值;日出后急剧下降,傍晚又开始逐渐增加。芦苇湿地感热通量昼正夜负,潜热通量与林地不同,全天为正。各通量季节变化明显,冬季CO2通量日变化不明显,趋近于零;感热通量总体向上输送,春季数值较大,生长季数值较小;潜热通量冬季最小,接近0,春季开始显著增加,生长季达到最大。 相似文献
16.
17.
M. A. Tadross W. J. Gutowski Jr B. C. Hewitson C. Jack M. New 《Theoretical and Applied Climatology》2006,86(1-4):63-80
Summary Two cumulus convection and two planetary boundary layer schemes are used to investigate the climate of southern Africa using
the MM5 regional climate model. Both a wet (1988/89) and a dry (1991/92) summer (December–February, DJF) rainfall season are
simulated and the results compared with three different observational sources: Climate Research Unit seasonal data (precipitation,
2 m surface temperature, number of rain days), satellite-derived diurnal precipitation and the Surface Radiation Budget diurnal
short-wave fluxes and optical depth.
Using the ETA model boundary layer in MM5 simulates too much incident short-wave radiation at the surface at 12 UTC, whereas
the medium range forecast model boundary layer yields a diurnal cycle of short-wave radiation closer to the observed. The
Betts-Miller convection scheme in MM5 simulates peak rainfall later in the day and less rain days than observed, whereas when
using the Kain-Fritsch convection scheme a peak rainfall earlier in the day and more rain days than observed are simulated.
The intensity of the hydrological cycle is therefore dependent on the choice of convection scheme, which in turn is further
modified by the boundary layer scheme. Precipitation during the wet 1988/89 season is reasonably captured by most simulations,
though using the Betts-Miller scheme more accurately simulates rainfall during the dry 1991/92 season. Mean DJF biases in
the surface temperature and diurnal temperature range are consistent with biases in the number of rain days and the diurnal
cycles of surface moisture and energy. 相似文献
18.
J.-F. Miao D. Chen K. Wyser K. Borne J. Lindgren M. K. S. Strandevall S. Thorsson C. Achberger E. Almkvist 《Meteorology and Atmospheric Physics》2008,99(1-2):77-103
Summary The performance of MM5 mesoscale model (Version 3.6.3) using different planetary boundary layer (PBL) and land surface model
(LSM) parameterizations is evaluated and compared using high temporal and spatial resolution G?TE2001 campaign data at local
scale (a few kilometers) over the Greater G?teborg area along the Swedish west coast during 7–20 May 2001. The focus is on
impact of PBL and LSM parameterizations on simulated meteorological variables important for air quality applications such
as global radiation, diurnal cycle of near-surface air temperature and wind, diurnal cycle intensity, near-surface vertical
temperature gradient, nocturnal temperature inversion, boundary layer height, and low-level jet (LLJ). The model performance
for daytime and nighttime and under different weather conditions is also discussed. The purpose is to examine the performance
of the model using different PBL and LSM parameterizations at local scale in this area for its potential applications in air
quality modeling. The results indicate that the influence of PBL and LSM parameterizations on simulated global radiation,
diurnal cycle of near-surface air temperature and wind speed, diurnal cycle intensity, vertical temperature gradient, nocturnal
temperature inversion and PBL heights, which are critical parameters for air quality applications, is evident. Moreover, the
intensity and location of LLJ are simulated well by all schemes, but there also exist some differences between simulated results
by using different PBL and LSM schemes. Therefore, the choice of PBL and LSM parameterizations is important for MM5 applications
to air quality studies.
Correspondence: Junfeng Miao, Department of Earth Sciences, G?teborg University, P.O. Box 460, 405 30 G?teborg, Sweden 相似文献
19.
Modeling the potential effects of climate change on water temperature downstream of a shallow reservoir,lower madison river,MT 总被引：2，自引：0，他引：2
A numerical stream temperature model that accounts for kinematic wave flow routing, and heat exchange fluxes between stream water and the atmosphere, and stream water and the stream bed is developed and calibrated to a data-set from the Lower Madison River, Montana, USA. Future climate scenarios were applied to the model through changes to the atmospheric input data based on air temperature and solar radiation output from four General Circulation Models (GCM) for the region under atmospheric CO2 concentration doubling. The purpose of this study was to quantify potential climate change impacts on water temperature for the Lower Madison River, and to assess possible impacts to aquatic ecosystems. Because water temperature is a critical component of fish habitat, this information could be of use in future planning operations of current reservoirs. We applied air temperature changes to diurnal temperatures, daytime temperatures only, and nighttime temperatures only, to assess the impacts of variable potential warming trends. The results suggest that, given the potential climatic changes, the aquatic ecosystem downstream of Ennis Lake will experience higher water temperatures, possibly leading to increased stress on fish populations.Daytime warming produced the largest increases in downstream water temperature. 相似文献
20.
利用非静力中尺度模式WRF模拟了台风Chanchu（0601）,模式再现了台风Chanchu的路径、强度及结构。利用模式资料分析了台风Chanchu发展增强过程中其流出层和流入层风速的日变化特征、造成该日变化特征的机制及其对台风强度的影响。分析表明:台风Chanchu流出层和流入层的风速均存在显著的日变化特征,表现在低层径向入流和高层径向出流在夜间至清晨明显增强,在白天增加缓慢;切向风变化趋势同径向风类似,位相较径向风落后约6 h。通过对比夜间和白天云顶温度（CTT）和垂直速度频率（CFADS）的分布,发现夜间对流较白天更加活跃,这与夜间云顶冷却所导致的静力稳定度降低有关。利用切向风倾向方程进行收支分析,结果显示太阳辐射日变化通过调节对流日变化,引起高低层径向气流的日变化,进而造成切向风速的日变化,从而影响台风强度,在一定程度上揭示了日变化对台风强度变化的指示意义。 相似文献