海岛地区分区大风预报探讨

利用海岛自动测风站网的风力资料分析了舟山海域风力的分布特征,在此基础上有针对性地把舟山海域划分为5个海区,针对目前舟山沿海海面风力预报（公众预报）范围偏大,不能正确反映舟山海域风力局地特征的重大缺陷,提出了以分海区大风预报代替舟山沿海海面风力预报的设想和预报技术思路.预报实践表明：与目前的舟山沿海海面风力预报相比,分海区大风预报不仅更加客观合理和具有针对性,而且能够有效地解决海上安全与效益之间的矛盾,适合在海岛地区推广应用.     

冬小麦赤霉病流行程度长期预报模型

小麦赤霉病的发生流行程度主要由天气条件决定,而５００ｈＰａ大气环流因子是较好地表征天气形势和控制天气条件的物理量。利用最优化相关分析方法,分区挑选了与小麦赤霉病显著、稳定相关的５００ｈＰａ大气环流因子,在此基础上建立了冬小麦赤霉病流行程度长期预报环流模型。     

模型参数对赤霉病人工神经网络预报模型精度的影响

运用最优化相关普查方法,选取确定了对江苏省太湖地区小麦赤霉病发生程度有着显著指示意义的预报因子,将其作为输入变量经多层前馈神经网络的ＢＰ算法进行学习训练,建立了赤霉病病穗率的人工神经网络预报模型。分析了结构参数对模型效果的影响情况,发现训练的总体误差平方和对模型的效果最为显著,历史样本的拟合率随着总体误差平方和的拳小而稳定上升,但总体误差平方和取值偏小时模型对独立样本的预报精度下降;当总体误差平方     

基于自动站资料的海上风客观预报方法

根据辽宁省沿海自动站资料,采用卡尔曼滤波方法对沈阳区域气象中心MM5中尺度数值预报产品进行解释应用,制作环渤海及邻近海域海面最大风矢量预报的技术方法,对2009年8-12月预报结果进行检验。结果表明：海上最大风矢量预报结果中风速的预报要明显好于风向的预报,其中风向预报最好的海区为黄海北部,准确率为57.3 %;风速预报最好的海区为渤海中部,准确率为64.6 %;风速误差以正误差为主,说明风速的预报值与实况值相比偏大。该方法对于环渤海及邻近海域海上风的预报效果较好,能够比较真实地反映海上风演变过程,具有预报参考价值。     

粤东海面冷空气强风的统计分析与预报

近年粤东海面强风日数比过去偏少,分析粤东海区不同季节强风天气形势,气压差与海面风的相关性表明,随着时间后延,相关系数极大值从东南沿海向西北方向延伸,6、12、24、48 h相关性最好地区分别位于福建沿海、浙江沿海、长江中下游、河套地区.确定强风预报指标,用统计方法建立了强风的回归预报方程.     

用海温预测二代粘虫发生区一代成虫迁入期的模式研究

影响粘虫发生的外界因素很多，因此预测粘虫发生期的因子和方法必然也是多样的。本文中用前期海温作为预报因子，采用逐步回归方法，通过电子计算机建立了二代粘虫发生区一代成虫迁入期预测模式。其方法和结果如下:1．以二代粘虫发生区一代成虫迁入期为预报对象。2．对一代成虫迁入前期的上一年1月至当年5月北太平洋逐月海面水温资料进行了相关分析。各预报量都得到了几十个高相关海区，以此作为预报因子。3．用它们建立的预测模式，都得到比较好的结果。这说明用前期海温直接预报粘虫发生期是可行的。     

山东省沿海冬春季海陆大风对比分析

利用山东省划分的沿海12个海区代表站和部分海岛站资料,6艘渤海和黄海救助船资料,验证了2010年11月以来冬春季海区大风过程(≥6级)中,烟台北部沿海和威海南部沿海站大风资料的可用性,并对渤海湾、渤海中部海区、黄海北部海区和山东沿海大风进行了对比分析,得到以下结论:(1)渤海湾海区,滨州北部和东营北部沿海站均比海面风速偏小。(2)渤海中部海区,当天气系统为低槽冷锋时,东营东部、潍坊北部、烟台北部和烟台西部沿海站均比海面风速偏小。(3)黄海北部海区,在统计时段内,成山头站非常接近海面风速,其次是长岛县大黑山比海面风速小3 m·s-1左右。     

基于GIS的小麦赤霉病气象等级预报系统的设计与实现

以江苏省为例,介绍了基于地理信息系统的小麦赤霉病气象等级预报系统的设计思路及核心技术。系统采用VB.Net 2005和ArcEngine做为开发平台,基于MSSQL SERVER 2005数据库查询,利用日平均相对湿度、日平均气温和日照时数3个气象要素,用两种算法来计算小麦赤霉病发生发展的气象等级,生成包含地理信息的文字产品和图形产品,实现了小麦赤霉病气象等级业务预报。系统具有功能强大,算法高效,操作简单等特点,解决了业务部门资料分析处理和赤霉病气象等级预报的相关问题,具有很好的业务应用和推广价值。     

小麦赤霉病预报专家系统建立和应用

根据本地农业气象服务的需要,为了进一步完善小麦赤霉病预报方法、普遍推广专家预报经验、提高预报准确率和服务效益,我们建立了金华小麦赤霉病预报专家系统。该系统引用了北京工业学院人工智能研究所和卫星气象中心用 lisp 语言研制的气象预报专家系统的有关基础程序,较广泛地收集了国内有关赤霉病预报的先进经验,结合本地具体情况综合整理成推理规则,在 IBM-PC 机上进行,建成专家系统。试报和应用效果较好。本文对该系统的建立和应用作简要介绍。     

完全预报（PP）方法在广东冬半年海面强风业务预报中的应用

在进行大量普查分析和统计的基础上, 将最近10年历史天气图的地面气压和有关海面强风代表站的风场资料在日本数值预报模式输出报文的1.25°×1.25°格点分布上进行客观分析, 对比传统的以关键区域划分冷空气入侵路径与广东海面强风的关系, 提出了一套与广东冬季海面强风关系更密切、作用更直接的地面关键区气压场分布特征进行客观定量的分型;根据梯度风原理, 用经验加统计的因子挑选方法, 形成了一套应用日本数值预报模式输出、适用于广东海面强风预报的完全预报(PP)方法。检验和业务试用结果均表明:该方法对广东的海面强风具有较强的预报能力;用完全预报方法做沿海海面强风预报是可行的。     

青藏高原和热带印度洋5月热力异常与新疆夏季降水的关系

基于1979-2017年美国国家海洋和大气管理局(NOAA)提供的海表温度资料和美国国家环境预测中心(NCEP)/美国国家大气研究中心(NCAR)提供的大气环流再分析资料以及青藏高原地区149个站点观测资料计算的地表感热通量和新疆气象信息中心提供的全疆81站逐月降水资料等,研究了5月青藏高原和热带印度洋加热对新疆夏季降...     

Influence of sea surface temperatures on air temperatures in the tropics

Interannual variations of tropical tropospheric temperatures are closely related to sea surface temperature (SST) changes in the tropical eastern Pacific (TEP). This study investigated the physical mechanisms for such an air-sea interrelationship. SSTs and latent heat flux were analyzed to find the unique properties of their variations during El Niño. A Gill-type model was used to investigate how a local heat source communicates with the entire tropics. Radiative fluxes in the tropics were evaluated to search for the factors limiting air temperature increases when warm SSTs remain in the TEP. We found that interannual variabilities of SST and latent heat flux are dominated by the variations in the TEP region. The SST variations there have three unique properties that allow the ocean to influence the atmosphere effectively: large magnitude, long persistence, and spatial coherence. The Gill-type model shows that a local heat source can warm the entire tropical troposphere when the heat source is near the equator. Released latent heat in the heat source region and forced adiabatic subsidence elsewhere in the tropics warm the atmosphere. As a result, a local heat source warms the entire tropical strip. The forced subsidence depresses clouds, allowing more infrared radiation to leave the atmosphere and preventing further atmospheric warming when warm SSTs remain in the TEP. This finding is verified by reanalysis data from the National Centers for Environmental Prediction.     

RELATIONSHIPS BETWEEN PRECEDING PACIFIC SEA SURFACE TEMPERATURES AND SUBTROPICAL HIGH INDEXES OF MAIN RAINING SEASONS

With correlation analysis and factor analysis methods, the effects of preceding Pacific SSTs on subtropical high indexes of main raining seasons are discussed. The results of correlation analysis show that the effects of SSTs on five subtropical high indexes differ in seasons and regions. The variation of SSTs mostly affects the area and intensity indexes of the subtropical high, followed by the western ridge index, and the effect on the ridge line index is more remarkable than on the north boundary index. The results of factor analysis reveals that the first common factor of SST of each season reflected mainly the inverse relation of SSTs variation between the central and eastern part of equatorial Pacific and the western Pacific, which correlates better with the subtropical high indexes in the main raining seasons than other common factors of SST. The analysis of interdecadal variation indicated that the variation of SSTs was conducive to the emergence of the La Ni?a event before the end of 1970s, such that in the summer the subtropical high is likely to be weaker and smaller and located eastward and northward. After the 1980s, the opposite characteristics prevailed.     

长江流域夏季降水及其与海温的滞后相关

基于月平均台站降水资料分析了中国东部降水的气候特征。由于其降水分布在空间和时间上的复杂性，为便于研究其与海温的关联，特别是海温对降水的影响，根据台站间降水变化在季节变化和年际变化以及与海温相关的一致性，将中国东部区域分成四个子区域。以长江流域的降水为代表，分析了海温对降水的超前相关。给出了主要影响海区和它们的超前时间。综合各影响海区海温和超前时间建立的回归方分析表明：回归降水和观测降水的相关系数大于０．８５。回归的平方根误差是其标准差的６０％和平均雨量的１５％。另外还分析了海温与降水相关与环流变化的一致性。     

热带大西洋海温异常季节内演变对中国江南地区夏季持续性高温事件影响的初步研究

中国江南地区是高温热浪灾害的高影响区.以往的一些研究发现了不同海域海温异常在年际或年代际尺度上的变化对中国南方夏季平均温度异常的影响效应.但是,关于这些关键海域海温季节内尺度变化对江南地区高温事件发生和维持影响的研究尚不多见.为此,本文利用中国站点观测、美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)再...     

Assessing levels of uncertainty in recent temperature time series

 We examine to what degree we can expect to obtain accurate temperature trends for the last two decades near the surface and in the lower troposphere. We compare temperatures obtained from surface observations and radiosondes as well as satellite-based measurements from the Microwave Soundings Units (MSU), which have been adjusted for orbital decay and non-linear instrument-body effects, and reanalyses from the European Centre for Medium-Range Weather Forecasts (ERA) and the National Centre for Environmental Prediction (NCEP). In regions with abundant conventional data coverage, where the MSU has no major influence on the reanalysis, temperature anomalies obtained from microwave sounders, radiosondes and from both reanalyses agree reasonably. Where coverage is insufficient, in particular over the tropical oceans, large differences are found between the MSU and either reanalysis. These differences apparently relate to changes in the satellite data availability and to differing satellite retrieval methodologies, to which both reanalyses are quite sensitive over the oceans. For NCEP, this results from the use of raw radiances directly incorporated into the analysis, which make the reanalysis sensitive to changes in the underlying algorithms, e.g. those introduced in August 1992. For ERA, the bias-correction of the one-dimensional variational analysis may introduce an error when the satellite relative to which the correction is calculated is biased itself or when radiances change on a time scale longer than a couple of months, e.g. due to orbit decay. ERA inhomogeneities are apparent in April 1985, October/November 1986 and April 1989. These dates can be identified with the replacements of satellites. It is possible that a negative bias in the sea surface temperatures (SSTs) used in the reanalyses may have been introduced over the period of the satellite record. This could have resulted from a decrease in the number of ship measurements, a concomitant increase in the importance of satellite-derived SSTs, and a likely cold bias in the latter. Alternately, a warm bias in SSTs could have been caused by an increase in the percentage of buoy measurements (relative to deeper ship intake measurements) in the tropical Pacific. No indications for uncorrected inhomogeneities of land surface temperatures could be found. Near-surface temperatures have biases in the boundary layer in both reanalyses, presumably due to the incorrect treatment of snow cover. The increase of near-surface compared to lower tropospheric temperatures in the last two decades may be due to a combination of several factors, including high-latitude near-surface winter warming due to an enhanced NAO and upper-tropospheric cooling due to stratospheric ozone decrease. Received: 5 May 1999 / Accepted: 15 December 1999     

Seasonal predictability of ENSO teleconnections: the role of the remote ocean response

In this modelling study, the teleconnections of ENSO are studied using an atmospheric general circulation model (AGCM), HadAM3. The influence of sea surface temperature anomalies (SSTAs) remote from the tropical Pacific but teleconnected with ENSO is investigated. Composite cycles of El Niño and La Niña SSTs are created and imposed on HadAM3. These SSTs are imposed in different areas, with climatological SSTs elsewhere, in order to find the influences of SSTs in different regions. It is found that most of the reproducible response to ENSO is forced directly from the tropical Pacific before the peak of the event. However, during the peak and decay of ENSO, remote SSTs become increasingly influential throughout the tropics (at the 98% significance level). This could lead to extended ENSO-related predictability due to the memory of the remote oceans. The Indian Ocean and Maritime Continent SSTs are found to be particularly influential. Indian Ocean SSTAs dampen the teleconnections from the tropical Pacific and force the atmosphere above the tropical Atlantic. More generally, when a tropical SSTA is imposed, atmospheric anomalies are forced locally with anomalies of the opposite sign to the west. Some of the reproducible response to ENSO in the tropical Atlantic is forced, not directly from the tropical Pacific but from the Indian ocean, which in turn is forced by the tropical Pacific. Subsequently, delayed SSTAs in the tropical Atlantic damp the local response and force the atmosphere above the tropical Pacific in the opposite manner.     

Links between tropical SST anomalies and precursory signalsassociated with the interannual variability of Asian summer monsoon

Summary ?The interannual variability of broad-scale Asian summer monsoon was studied using a general circulation model (GCM) and NCEP (National Center for Environmental Prediction) data set during 1979–95. In the GCM experiment, the main emphasis was given to isolate the individual role of surface boundary conditions on the existence of winter-spring time circulation anomalies associated with the interannual variability of Asian summer monsoon. In order to understand the role of sea-surface temperatures (SSTs) alone on the existence of precursory signals, we have conducted 17 years numerical integration with a GCM forced with the real-time monthly averaged SSTs of 1979 to 1995. In this experiment, among the many surface boundary conditions only SSTs are varying interannually. The composite circulation anomalies simulated by the GCM have good resemblance with the NCEP circulation anomalies over subtropical Asia. This suggests that the root cause of the existence of winter-spring time circulation anomalies associated with the interannual variability of Asian summer monsoon is the interannual variability of SST. Empirical Orthogonal Functions (EOFs) of 200-mb winds and OLR were constructed to study the dynamic coupling between SST anomalies and winter-spring time circulation anomalies. It is found that the convective heating anomalies associated with SST anomalies and stationary eddies undergo systematic and coherent interannual variations prior to summer season. We have identified Matsuno-Gill type mode in the velocity potential and stream function fields. This suggests the existence of dynamic links between the SST anomalies and the precursory signals of Asian summer monsoon. Received June 9, 1999/Revised April 7, 2000     

Climate sensitivity to tropical land surface changes with coupled versus prescribed SSTs

Tropical land cover change experiments with fixed sea-surface temperatures (SSTs) and with an interactive ocean are compared to assess the relevance of including the ocean system in sensitivity studies to land surface conditions. The results show that the local response to deforestation is similar with fixed and simulated SSTs. Over Amazonia, all experiments simulate a comparable decrease in precipitation and no change in moisture convergence, implying that there is only a change in local water recycling. Over Africa, the impact on precipitation is not identical for all experiments; however, the signal is smaller than over Amazonia and simulations of more than 50 years would be necessary to statistically discriminate the precipitation change. We observe small but significant changes in SSTs in the coupled simulation in the tropical oceans surrounding the deforested regions. Impacts on mid and high latitudes SSTs are also possible. As remote impacts to deforestation are weak, it has not been possible to establish possible oceanic feedbacks to the atmosphere. Overall, this study indicates that the oceanic feedback to land surface sensitivity studies is of second importance, and that the inclusion of the oceanic system will require ensembles of long climate simulations to properly take into account the low frequency variability of the ocean.