湛江地区近海岸雾产生的天气条件及宏微观特征分析

利用2011年2～3月广东省湛江市东海岛雷达站观测得到的12次雾过程中雾滴谱、能见度、边界层风温场资料以及常规气象资料,对沿岸海雾发生时的天气系统进行分类,分析了雾发生时的气象条件、边界层特点、微物理特征等,并对典型个例进行讨论。总结发现:海雾易出现在低压前部、高压后部和冷锋前部等天气形势下;雾过程中,地面以偏东风为主,高空以偏东、偏南风为主;雾滴数浓度(N)的平均值变化范围为170～372 cm-3,液态水含量(LWC)为0.018～0.170 g m-3,平均半径为1.71～3.28 μm。选取了一个典型个例来研究典型天气形势下海雾宏微观特征,该过程发展初期以核化凝结为主,在水汽不充足时,大量的雾滴凝结核争食水汽,使得N增加而平均半径几乎不变。根据自动转化阈值T可以看出,成熟时期碰并效率增加,大滴端数密度增加,滴谱拓宽。结合边界层气象要素演变分析发现,在夜间急流显著时,不利于雾滴生长,LWC较低;而高空风速较小,逆虚温较强可能是消散阶段平均半径出现跃增的原因。雾滴谱呈双峰分布,且瞬时谱符合Gamma分布;液态水含量与消光系数、有效半径呈正相关关系,相关系数分别为0.95和0.97。     

多层递阶回归分析

在经典多层递阶预报模型中,预报因子对模型的贡献大小主要取决于各因子间的相对量值差异,而与预报因子本身的实际预报价值关系甚微。本文针对这一缺陷,提出了一种回归分析与多层递阶方法相结合的统计预报模型——多层递阶回归分析。它既摒弃了经典统计理论中的固定参数预报模型,又较好地消除了由于变量间相对量值差异所造成的贡献差异,充分体现了高相关因子在预报模型中的重要作用。实例计算结果表明,多层递阶回归分析方法的预报效果明显优于经典多层递阶方法和回归分析。     

Surface ocean response to synoptic-scale variability in wind stress and heat fluxes off south-central Chile

The effect of the high frequency (synoptic) variability of wind and heat fluxes upon the surface ocean off south-central Chile (west coast of South America) is investigated using a regional ocean model. We focus our analysis in austral summer, when the regional wind experiences significant day-to-day variability superimposed on a mean, upwelling favorable flow. To evaluate the nature and magnitude of these effects, we performed three identical simulations except for the surface forcing: the climatological run, with long-term monthly mean wind-stresses and heat fluxes; the wind-synoptic run, with daily wind stresses and climatological heat fluxes; and the full-synoptic run, with daily wind-stresses and daily fluxes. The mean currents and surface geostrophic EKE fields show no major differences between simulations, and agree well with those observed in this ocean area. Nevertheless, substantially more ageostrophic EKE is found in the simulations which include synoptic variability of wind-stresses, impacting the total surface EKE and diffusivities, particularly south of Punta Lavapie (37° S), where the lack of major currents implies low levels of geostrophic EKE. Summer mean SSTs are similar in all simulations and agree with observations, but SST variability along the coast is larger in the runs including wind-stress synoptic variability, suggesting a rather linear response of the ocean to cycles of southerly wind strengthening and relaxation. We found that coastal SST variability does not change significantly in the first tenths of kilometers from the shore when including daily heat fluxes, highlighting the prominent role of wind-driven upwelling cycles. In contrast, in the offshore region situated beyond the 50 km coastal strip, it is necessary to include synoptic variability in the heat fluxes to account for a realistic SST variability.     

2000年夏季河南大暴雨的预报特征

以 2 0 0 0年 7月河南省 10站以上连成片、日雨量≥ 10 0mm且降水中心日雨量 >2 0 0mm的 4次大暴雨过程为样本 ,从天气形势、水汽条件、不稳定度和中小尺度等方面进行了分析 ,并辅以部分物理量计算 ,进而揭示出大暴雨过程的部分预报特征     

珠江三角洲地区天气类型与污染潜势及污染浓度的关系

利用１９８６—１９９３年珠江三角洲地区主要城市的污染浓度资料和天气资料，计算了不同月份各种天气类型下大气污染物浓度超过二级标准的频率，得出珠江三角洲地区天气类型和地面空气污染浓度之间的定性关系。发现大气中的污染物浓度（如ＳＯ２、ＮＯｘ、ＴＳＰ、ＣＯ）不仅与当天的天气类型有着密切联系，而且与前几天的天气类型的持续时间、地面气压场和高空气压场的配置、锋面移动的快慢、热带气旋的影响等天气因素均有关系。     

天气形势对南昌市空气质量影响的初步分析

利用2007--2010年南昌市空气污染监测资料以及气象观测资料,分析了空气质量与天气形势的关系,以及造成南昌市空气污染的主要天气形势特征。结果表明：（1）南昌市空气污染具有明显的季节性变化特征,冬季污染日出现频次最高,其次是春、秋两季,夏季由于雨水的冲刷稀释作用、热对流作用,极少出现空气污染日。（2）影响南昌市空气质量的地面形势主要分为低压类（倒槽、锋前）和高压类（高压底部、高压后部、弱高压）,而高空系统主要为槽后西北气流以及西南气流的影响。（3）当出现空气污染时,地面至1000hPa近地层逆温非常明显,地面风速弱,基本在3m／s以下,且以偏东风出现频次最高。（4）污染物浓度与霾天气密切相关,霾日的空气质量较差。     

我国东南部地形对降水量分布的气候影响

利用１９５１－１９８０年地面测站网的年、月平均降水量资料，分析出我国东南部地区的地形对降水量分布存在着气候影响。其影响表现在浙闽山区的东西两侧山坡各有一条多雨带，南岭南北两侧山坡附近各有一个多雨区。从这些多雨带和多雨区出现的季节清楚地呈出出地形的向风坡在多雨带和多雨区形成中的作用。指出这些多雨带和多雨区是由地形对降水天气系统影响产生的向风坡多雨带。     

影响准东西向切变线运动的一些因子分析

本文认为江淮切变线是由于纬向风的不连续切变形成涡层的表现形式,且呈准东西向。对此涡层的分析得到一些关系到切变线移动的因素。     

Characteristics of Stable Flows over Southern Greenland

The main characteristic features of stable atmospheric flows over a large mountain plateau are summarised and then compared with mesoscale and synoptic scale numerical simulation, meteorological analysis, satellite imagery, and surface observations for the cases of flows over Southern Greenland for four wind directions. The detailed features are identified using the concepts and scaling of stably stratified flow over large mountains with variations in surface roughness, elevation, and heating. For westerly and easterly winds detached jets form at the southern tip, where coastal jets converge, which propagate large distances across the ocean. Near coasts katabatic winds can combine with barrier jets and wake flows generated by synoptic winds. Note how the approach flow rises/falls over southern Greenland for easterly/westerly winds, leading in both cases to more cloud on the western side. Some conclusions are drawn about the large-scale influences of these flows; detached jets in the atmosphere; air-sea interaction; formation of low pressure systems. For accurate simulations of these flows, mesoscale models are necessary with resolutions of order of 20 km or less.     

台风浪场及天气形势图的智能检索研究

本文对台风浪场及天气图的智能检索功能提出了许多设想，其中着重阐述了智能相似检索的机制，并对各种随机检索和静态相似检的系统软件进行了开发设计和试验研究。