坡面日出日没时角的配置关系与坡向坡度

对于给定的纬度和太阳赤纬,在水平面非极昼时的偏东（偏西）坡面上存在一对互补的坡向,以互补的两个坡向（一般临界坡向）为界,坡面日出日没时角的配置关系具有三种不同的形式。在两个一般临界坡向之间,在坡面日出日没时角的配置关系与坡度无关,或者为ω1=ωs1,ω2=ω0（偏西坡）,或者为ω1=-ω0,ω2=ωs2（偏东坡）。存在一参考坡度α0（arccos（sinφ／cosδ））,一般临界坡向之外的时角配置关系以坡度α0为界,具有不同的形式。如果坡度一定,可存在使非水平面极昼或极夜的特别临界坡向,在一般临界坡向之外,特别临界坡向前后,坡面日出日没时角的配置关系也不同。在一般临界坡向之外,如果坡向一定,可存在参考纬度φ0=arccos（｜cosδ／cosβ｜）,以及使非水平面极昼或极夜的临界坡度。以参考纬度为界,坡面日出日没时角的配置关系或者随临界坡度而变化,或者与坡度无关。     

山地天文辐射的地形影响与空间尺度效应研究

基于1∶25×104数字高程模型数据,依据起伏地形下天文辐射分布式模型算法,研究了陕西山地天文辐射空间分布规律,详细分析了地形因子对天文辐射的影响规律;同时,从不同的DEM分辨率和不同地貌类型两个方面探讨了天文辐射的空间尺度效应。结果表明:陕西天文辐射总量随着纬度的升高呈由南向北降低的趋势;局地地形因子对天文辐射的影响随季节、纬度、坡度及坡向等因素而变;同时山地天文辐射的空间尺度效应在地势起伏较大的山区和高原地区表现尤为明显。     

坡面辐射场的模式计算及结果分析

本文旨在建立一个不依靠地面辐射观测资料的坡面辐射场的计算模式。在全国范围内均匀地选取74个气象台站,计算了我国1、7月份8个坡向和8个坡度的坡面辐射平衡及其分量,并进行了分析,揭示了一些规律。     

起伏地形下深圳市天文辐射的空间分布

以起伏地形下天文辐射的分布模型为基础,借助地理信息系统(GIS)处理数据,将深圳市1∶250,000DEM数据作为地形的综合反映,模拟计算了起伏地形下(坡度、坡向和地形遮蔽)深圳市天文辐射,分析了起伏地形下深圳市天文辐射的分布规律,完成了深圳市100m×100m分辨率的各月及全年的天文辐射的空间制图。结果表明:对于局部地形起伏引起的天文辐射的变化,秋、冬季最为显著,向阳坡和背阴坡的极值差异较大,这和太阳高度角随着季节变化而冬半年相对较低、夏半年相对较高有关。坡度对天文辐射的影响在冬半年较大,随着坡度的增大,辐射差值增大的幅度呈递减趋势。     

改进任意时期天文辐射总量的计算方法初探

采用本文提供的公式计算任意时期的天文辐射总量,不需要查取天文年历上的太阳赤纬、时差、日地距离等数据,只要输入台站纬度和计算日期的年内日序数,就能启动电算程序打印出准确可靠的结果。     

墙面可能晴天太阳辐射小时总量的计算与分布

以卡斯特洛夫公式为理论基础,得到各朝向墙面可能晴天太阳总辐射和直接辐射小时总量的计算方案,计算了我国704个气象站各月代表日各个朝向墙面的逐时辐射值,分析其变化规律,并讨论了最大1h辐射量的全国分布。结果表明：南墙晴天最大1h辐射量随纬度升高而增大,而且在冬季其辐射量在各墙面中最大;东、西墙受纬度因素影响相对较小,在夏季其辐射量在各墙面中最大。     

广西地面太阳辐射分布特征以及对人体健康的影响

选用2001-2010年广西桂林、南宁、北海3个地面太阳辐射站的总辐射资料及日照时数资料,分析了总辐射日总量、日最大值的年变化规律,时总量的日变化规律,日最大值出现时间频率的分布区间等,结果表明：（1）广西太阳总辐射的日总量、日最大值强度的年变化规律明显。总体呈现夏季最大,春秋季次之,冬季最小的特点。大多数情况下,随着纬度由北向南递减,总辐射值递增。日总量与日照时数的年变化趋势存在正向的线性相关。（2）广西太阳总辐射的时总量的日变化规律明显。总体呈现中午前后强．早晚弱的特点。最大值一般出现在一天中的10-14时这个区间．     

以前1万年至未来3千年天文辐射时空分布的长期演变

大气上界太阳辐射又称为日射、完全透明大气的太阳辐射、入射太阳辐射、没有大气时的太阳辐射或天文辐射等等。本文均采用“天文辐射”一词。它较好地揭示了大气上界太阳辐射日变化、年变化与随纬度分布的原因实质(即地球自转角速度、赤纬、日地距离等天文参数的变化及地理纬度的分布)。而且,天文辐射在地质时代的长期演变也主要取决于地球轨道参数(黄赤交角、偏心率及岁差)的周期性变化。这主要是由于太阳系中的其他8个行星以及月亮等施加的引力所造成的。根据以上的分析可以认为,采用天文辐射一词是较为确切的。它从天体力学角度揭示了大气上界太阳辐射时(日变化、年变化、长年变化)空(地理纬度)变化的原因实质,相对于其他学术词汇而言,含有实质性的信息量。     

坡面散射辐射的分布特征及其计算模式

本文应用安装在经纬仪上的天空辐射表所观测的坡面散射辐射资料,对散射辐射的各向异性问题作了较为详尽的分析。揭示出坡面散射辐射随坡向、坡度变化的基本规律。文中还对前人所提出的计算坡面散射辐射的各种模式进行了检验、评述。最终提出一种通用性较强的坡面散射辐射通量密度的计算模式。其物理意义和计算精度都较国外同类模式优越。     

焦作市太阳辐射资源分析评估

利用焦作市辖区7个县(市)1961-2010年的月日照百分率观测资料,以天文辐射为起始值,采用气候学计算方法获取辖区各站相应的太阳辐射资料.统计分析显示,全市近50 a的年均总辐射量在4625.026 ～5020.026MJ/m2,受所处太行山南麓的地形影响,区内太阳总辐射呈北低南高分布,与同纬度(30-40°N)内我国中东部地区太阳总辐射北高南低的分布特征相反.年内太阳辐射最少月出现在12月份(1月份次之),与天文辐射最少月相吻合;最多出现在5月份(6月份次之),较天文辐射最多的7月份提前2个月,这与该月日照时数≥6h天数的晴好天气比率最高相对应.按照太阳能资源评估国家标准(QX/T 89-2008)评估,辖区东南部属于资源很丰富区,北部和西部属于丰富区;辖区太阳能资源均属于稳定级别,但西北部山区稳定程度稍差.金市太阳辐射总量减少幅度明显大于全国平均减幅:20世纪60-70年代,全市平均年均辐射量超过5148.5 MJ/m2(达资源很丰富标准),但在20世纪80年代中前期太阳辐射量锐减,进入21世纪以来减少趋势不明显,市区有回升的态势.另外,年太阳辐射总量年变化曲线围绕着趋势线表现出较明显的波动,且振荡频率在加大.     

贵州高原起伏地形下日照时间的时空分布

由于坡度、坡向和地形之间相互遮蔽等局地地形因子的影响, 实际起伏地形下的日照时间与水平面上的日照时间有一定差异。该文建立了一种基于数字高程模型 (DEM) 的起伏地形下日照时间的模拟方法, 计算了起伏地形下贵州高原100 m×100 m分辨率日照时间的时空分布。结果表明:坡度、坡向、地形遮蔽对日照时间的影响较大, 实际起伏地形下日照时间的空间分布具有明显地域特征。1月太阳高度角较低, 坡度、坡向的作用非常明显, 地形遮蔽面积较大, 日照时间的空间差异较多, 日照时间为16~142 h, 最大值约为最小值9倍; 7月太阳高度角较高, 地形遮蔽面积相对较小, 日照时间的空间差异相对较少, 日照时间为133~210 h, 最大值为最小值1.6倍, 但由于7月日照时间相对较多, 局地地形对日照时间影响仍明显。4月、10月日照时间及其变化幅度介于1月和7月之间。     

Single and double ITCZ in an aqua-planet model with constant sea surface temperature and solar angle

It has been known for more than a decade that an aqua-planet model with a globally- and temporally-uniform sea surface temperature and solar isolation angle can generate intertropical convergence zones (ITCZ). Employing such a model, previous studies have shown that one of several means can be used to change between a single ITCZ over the equator and a double ITCZ straddling the equator. These means include switching to a different cumulus parametrization scheme, making changes within the cumulus parametrization scheme, and changing other aspects of the model such as horizontal resolution. Here, an interpretation of these findings is offered. In an aqua-planet model with globally and temporally uniform sea surface temperature and solar isolation angle, the latitudinal location of an ITCZ is the latitude where a balance exists between two types of attraction, both resulting from the Earths rotation. The first attraction pulls the ITCZ towards the equator and is not sensitive to changes in model design. It is directly related to the Coriolis parameter, which provides stability to the atmosphere. The second ssattraction pulls the ITCZ poleward and is sensitive to changes in model design. It is related to the convective circulation, modified by the Coriolis force. A balance between the two types of attraction is reached either at the equator or more than 10° north and south of the equator, depending on the shape and magnitude of the attractions. A balance at the equator yields a single ITCZ over the equator, whereas a balance north and south of the equator yields a double ITCZ straddling the equator.     

太阳总辐射最佳倾角的时空分布

本文根据倾斜面上太阳总辐最佳倾角的角析表示式，利用平均太阳总辐射和直接辐月总量以及实际地表面反射率，计算分析了我国各月最佳倾角和最佳总辐射比的时空变化特征。同时对用天空散射辐射各同性模式计算倾斜面上总辐日总量的适用性问题亦作了简要讨论。     

Diurnal momentum budget analysis of thermally induced slope winds

Summary  Data measured during the TRACT field campaign at various stations along a 7.5° steep and west-northwest facing slope of the Black Forest mountain range (Germany) are used to analyze the thermal structure and the momentum budget associated with thermally induced slope winds. Acceleration of the air close to the ground is found to be directed nearly vertically downward during the night and nearly vertically upward during the day, rather than parallel to the slope. This means that during the night the airflow is deflected by the slope surface in the down-slope direction, whereas during daytime stable stratification above the heated slope layer is required to establish up-slope flow parallel to the slope. The diurnal cycle of the momentum budget of the along-slope wind component near the surface is analyzed in detail with respect to the driving forces (buoyancy and pressure gradient force) and friction. It is found that a small imbalance between forcing and friction is responsible for the diurnal change in slope flow intensity. The along-slope components of the horizontal pressure gradient force and the buoyancy force are shown to have the same order of magnitude. This means that for small to moderate slope angles the pressure gradient force cannot be neglected as is done in some analytical slope wind models. The reaction time of the slope flow to changes in forcing is estimated to be in the range of 30 to 120 seconds, which confirms the empirically known fact that slope winds react very quickly. Received December 1, 1999 Revised June 13, 2000     

The tropopause slope as a characteristic of its deformation

The slope of the tropopause is calculated from the data of its height in the points of a regular grid. From the NCEP Reanalysis-2 for 1990–2007, the slope angles are calculated of the tropopause approximated by different constant values of Ertel potential vorticity within the latitude band of 30°–70° N. Effects of horizontal resolution of the data under use on the calculation results are studied on the basis of ten-day samples of objective analysis by UKMO, NCEP, and operative objective analysis of Hydrometeorological Center of Russia in different seasons of 2009.     

Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

Modulation of a monsoon under glacial forcing is examined using an atmosphere?Cocean coupled general circulation model (AOGCM) following the specifications established by Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2) to understand the air?Csea?Cland interaction under different climate forcing. Several sensitivity experiments are performed in response to individual changes in the continental ice sheet, orbital parameters, and sea surface temperature (SST) in the Last Glacial Maximum (LGM: 21?ka) to evaluate the driving mechanisms for the anomalous seasonal evolution of the monsoon. Comparison of the model results in the LGM with the pre-industrial (PI) simulation shows that the Arabian Sea and Bay of Bengal are characterized by enhancement of pre-monsoon convection despite a drop in the SST encompassing the globe, while the rainfall is considerably suppressed in the subsequent monsoon period. In the LGM winter relative to the PI, anomalies in the meridional temperature gradient (MTG) between the Asian continents minus the tropical oceans become positive and are consistent with the intensified pre-monsoon circulation. The enhanced MTG anomalies can be explained by a decrease in the condensation heating relevant to the suppressed tropical convection as well as positive insolation anomalies in the higher latitude, showing an opposing view to a warmer future climate. It is also evident that a latitudinal gradient in the SST across the equator plays an important role in the enhancement of pre-monsoon rainfall. As for the summer, the sensitivity experiments imply that two ice sheets over the northern hemisphere cools the air temperature over the Asian continent, which is consistent with the reduction of MTG involved in the attenuated monsoon. The surplus pre-monsoon convection causes a decrease in the SST through increased heat loss from the ocean surface; in other words, negative ocean feedback is also responsible for the subsequent weakening of summer convection.     

Equatorial Atlantic variability and its relation to mean state biases in CMIP5

Coupled general circulation model (GCM) simulations participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) are analyzed with respect to their performance in the equatorial Atlantic. In terms of the mean state, 29 out of 33 models examined continue to suffer from serious biases including an annual mean zonal equatorial SST gradient whose sign is opposite to observations. Westerly surface wind biases in boreal spring play an important role in the reversed SST gradient by deepening the thermocline in the eastern equatorial Atlantic and thus reducing upwelling efficiency and SST cooling in the following months. Both magnitude and seasonal evolution of the biases are very similar to what was found previously for CMIP3 models, indicating that improvements have only been modest. The weaker than observed equatorial easterlies are also simulated by atmospheric GCMs forced with observed SST. They are related to both continental convection and the latitudinal position of the intertropical convergence zone (ITCZ). Particularly the latter has a strong influence on equatorial zonal winds in both the seasonal cycle and interannual variability. The dependence of equatorial easterlies on ITCZ latitude shows a marked asymmetry. From the equator to 15°N, the equatorial easterlies intensify approximately linearly with ITCZ latitude. When the ITCZ is south of the equator, on the other hand, the equatorial easterlies are uniformly weak. Despite serious mean state biases, several models are able to capture some aspects of the equatorial mode of interannual SST variability, including amplitude, pattern, phase locking to boreal summer, and duration of events. The latitudinal position of the boreal spring ITCZ, through its influence on equatorial surface winds, appears to play an important role in initiating warm events.     

The influence of thermocline slope on equatorial thermocline displacement

The influence of a zonal slope in the thermocline on both wave- and wind-induced equatorial upwelling is studied. It is shown that the vertical displacement of the thermocline induced by a long Kelvin or planetary wave varies as the thermocline depth to the power $\text{?3}\text{8}$, as the wave propagates into a region of changed thermocline depth The zonal and meridional velocities induced by a wave vary as the thermocline depth to the power $\text{?7}\text{8}$. The wind-induced upwelling associated with a zonal slope of the thermocline is shown to be strongly confined to the equator. The importance of thermocline slope on the Ekman divergence is found to increase with time from the initial application of the wind stress perturbation. In the Pacific Ocean the meridional velocity may be altered by up to 60% by the thermocline slope before the influence of the boundaries becomes important.     

Changes in the South Pacific Convergence Zone in IPCC AR4 future climate projections

The response of the South Pacific Convergence Zone (SPCZ) to climate change is examined using simulations from 16 coupled climate models under the A2 emission scenario carried out for the Intergovernmental Panel on Climate Change Fourth Assessment Report. Characteristics of the austral summer SPCZ in the late twenty-first century are compared with the late twentieth century: the orientation and latitude of the SPCZ precipitation band; the area and intensity of precipitation within the SPCZ; and the eastern extent of the SPCZ. Changes in the SPCZ position are examined using a simple linear fit to the band of maximum precipitation and using a “pattern matching” technique. Both techniques find no consistent shift in the slope or mean latitude of the austral summer SPCZ. However, many models simulate a westward shift in the eastern edge of the SPCZ in austral summer, with reduced precipitation to the east of around 150°W. The westward contraction of the SPCZ is associated with a strengthening of the trade winds in the southeast Pacific and an increased zonal sea surface temperature gradient across the South Pacific. The majority of models simulate an increase in the area of the SPCZ and in mean and maximum precipitation within the SPCZ, defined by a 6?mm/day precipitation threshold, consistent with increased moisture convergence in a warmer climate. Changes in the SPCZ response to ENSO are examined using ENSO precipitation composites. The SPCZ has a reduced slope and is shifted towards the equator in the A2 multi-model mean El Ni?o composite.     

A comparison of the Vostok ice deuterium record and series from Southern Ocean core MD 88-770 over the last two glacial-interglacial cycles

Taking advantage of the fact that the Vostok deuterium (δD) record now covers almost two entire climatic cycles, we have applied the orbital tuning approach to derive an age-depth relation for the Vostok ice core, which is consistent with the SPECMAP marine time scale. A second age-depth relation for Vostok was obtained by correlating the ice isotope content with estimates of sea surface temperature from Southern Ocean core MD 88-770. Both methods lead to a close correspondence between Vostok and MD 88-770 time series. However, the coherence between the correlated δD and insolation is much lower than between the orbitally tuned δD and insolation. This reflects the lower accuracy of the correlation method with respect to direct orbital tuning. We compared the ice and marine records, set in a common temporal framework, in the time and frequency domains. Our results indicate that changes in the Antarctic air temperature quite clearly lead variations in global ice volume in the obliquity and precession frequency bands. Moreover, the average phase we estimated between the filtered δD and insolation signals at precessional frequencies indicates that variations in the southern high latitude surface temperature could be induced by changes in insolation taking place during a large period of the summer in northern low latitudes or winter in southern low latitudes. The relatively large lag found between Vostok δD variations and obliquity-driven changes in insolation suggests that variations in the local radiative balance are not the only mechanism responsible for the variability in surface temperature at those frequencies. Finally, in contrast to the cross-spectral analysis method used in previous studies, the method we use here to estimate the phases can reveal errors in cross-correlations with orbitally tuned chronologies. Received: 11 April 1995 / Accepted: 19 July 1995