ENSO事件与鲁西北夏季降水的关系

应用近百年ENSO事件的研究成果和ENSO事件影响年的资料，统计分析近50年来ENSO事件与鲁西北夏季降水关系，为短期气候预测和汛期气象服务提供参考依据。     

2003 - 08 - 24 咸阳市大暴雨过程分析

利用高空、地面天气图、红外云图、多普勒雷达图等资料对临汾市2004年6月16日局地降雹的天气背景、形势演变、层结稳定度、云图和雷达回波等变化特征进行了综合分析，结合以往冰雹预报经验对新一代雷达的探测能力进行了初步检验。分析发现，这次降雹过程属典型的西北冷涡影响型，此类型降雹相对于西北气流型和西风槽型降雹具有其自身特征；从多普勒速度图上，可分析出降雹过程中飑线前后较明显的中尺度天气系统。     

2002年6月13日重庆区域大暴雨分析

通过对重庆西部“6 1 3”区域大暴雨的分析 ,发现此次天气过程是一次典型的高原涡与西南涡耦合 ,结合地面弱冷空气条件下产生的 ,同时对ECMWF和T2 1 3数值预报产品进行了简要的分析 ,发现ECMWF和T2 1 3的形势预报能力都比较好 ,但T2 1 3的部分物理量要素和降水量预报能力还有待提高。     

从安徽气候变化看2003年洪涝和高温的必然性

利用近 50年温度和降水资料研究了安徽夏季气候变化特征 ,解释了 2 0 0 3年夏季洪涝、高温等极端气候事件出现的必然性。研究结果表明 :(1 )近 50年来安徽夏季温度呈下降趋势 ,降水则呈增加趋势 ,两者变化是相协调的。目前夏季温度处于较低的气候基本态 ,降水处于高基本态。 (2 )无论是温度还是降水 ,其变率都在 2 0世纪80年代中后期开始上升 ,目前均处于高气候变率时期。降水的“两高”(高基本态和高气候变率 )结合决定了 2 0 0 3年夏季洪涝出现的必然性 ;温度的较低基本态决定了“凉夏”背景 ,但由于基本态的回升和变率的加大 ,仍会出现像 2 0 0 3年夏季的若干高温天气。 (3)最大熵谱估计表明 ,安徽夏季降水变化的主周期为 2 5年 ,反映了降水的准两年振荡特征     

冬小麦遥感冠层温度监测土壤含水量的试验研究

在冬小麦主要生育期(2002年4月初到5月底),对不灌溉的冬小麦测定了冠层温度、地温、气温以及土壤含水量,计算了冠气温差且分析了冠层温度和冠气温差与不同土层厚度的土壤含水量相关关系。结果表明:14:00的冠层温度能较好地反映20cm土层的土壤含水量变化,但与其它各土层相关性有较大的波动性;14:00的冠气温差能较好地反映40cm以上土层的土壤含水量变化,二者的相关性很高,在20cm、40cm土层,两者相关系数R2分别为0.98866、0.99389,这为用区域遥感数据反演主要生育期冬小麦的冠气温差进而监测区域40cm土壤含水量提供了实验性的依据;拔节期和灌浆期,用14:00冠气温差来拟合各土壤层的土壤含水量有较高的精度,从而为用区域遥感数据监测区域土壤含水量提供了经验性的模型。     

Effects of temperature and humidity upon the transport of sedimentary particles by wind

Wind tunnel simulations of aeolian transport carried out over a range in mean temperature between 32 °C and ?9 °C suggest that cold airflows support higher mass transport rates (Q) than very warm air. The magnitude of this increase is larger than expected, so that analytical and semi‐empirical models underestimate Q. Extrapolation of the results suggests that, at ?40 °C, as for example in the dry valleys of Antarctica in winter, Q may be as much as 70% higher than for the equivalent wind speed in hot deserts at air temperatures of 40 °C. Temperature‐dependent changes in air density and turbulence contribute to this result. The decreased tension of water adsorbed onto particle surfaces at low temperatures is postulated to reduce interparticle cohesion and, thus, to increase the elasticity of particle impacts on cold beds. Definition of the roles that temperature and humidity play in aeolian transport is relevant to studies of palaeoenvironmental reconstruction and extraterrestrial (or planetary) geology. Investigation of present‐day, cold climate features and of climate change effects also requires knowledge of these fundamental relations.     

Meteorological Office, Pune-411 005

Natural disasters like floods, tornadoes, tropicalcyclones, heat and cold wavewreak havoc and cause tremendous loss ofproperty all over the world. Most ofthe natural disasters are either dueto weather or are triggered due toweather related processes.Extreme weather events claimed thousands oflives and caused damage on vastscale. Recent super cyclone which affectedOrissa in 1999, Bangladesh cyclone of1970 and Hurricane Andrew in 1992 areexamples of some of the more damagingtropical cyclones which affected developingas well as the developed world. Heatand cold waves are also extreme events,which cause enormous losses in terms oflives lost and human discomfort and ailmentsarising out of them. The heat waveof 1995 and 1998 are still fresh in the mindof the Indian public. The estimated lossof human lives due to heat wave in 1998 was morethan 15,000. Economic losses asa result of these disasters and in particular inassociation with tropical cyclones haveincreased enormously over the last three decades.During 1961–1991, total loss oflives from drought alone was 1,333,728 overthe whole world. In terms of economiclosses, there is 8–10 fold increase from thebase figure of 1960. The socio-economicimpact of natural disaster is complex dependingupon the vulnerability of the placeand mitigation strategies that are put in place.Meteorology plays a crucial role in forewarningpeople about the severe/extremeweather systems and a constant endeavour by themeteorological services worldover has gone a long way towards minimizing thelosses caused by natural disasters.The paper summarises the natural disasterstatistics over south Asia and the possibleprediction strategies for combating theirsocio-economic impacts.     

Impacts of Previous Winter Kuroshio SSTA on Summer Rainfall in China

1. IntroductionAs well known, Kuroshio is a famous and strongwest boundary current in the North Pacific. It trans-fers enormous energy from the low latitudes to themid-high latitudes and releases huge heat flux to theatmosphere above (Hsiung, 1985). The variation ofKuroshio exerts great influence on weather and cli-mate in East Asian.During 1950-60s, Lü (1950, 1964) found that thewestern North Pacific SSTA had a close relation withsummer rainfall in China. In the 1970s, evidencesshowed…     

Small inflation sources producing seismic and infrasonic pulses during the 2000 eruptions of Miyake-jima, Japan

During the 2000 activity of Miyake-jima volcano, Japan, we detected long period seismic signals with initial pulse widths of 1-2 s, accompanied by infrasonic pulses with almost the same pulse widths. The seismic signals were observed from 13 July 2000, a day before the second summit eruption. The occurrences of the seismic signals were intermittent with a gradual increase in their magnitudes and numbers building toward a significant explosive eruption on 18 August. After the eruption, the seismic and infrasonic events ceased. The results of a waveform inversion show that the initial motions were excited by an isotropic inflation source beneath the south edge of the caldera at a depth of 1.4 km. On the other hand, the sources of the infrasonic pulses were located in the summit caldera area. The times at which the infrasonic pulses were emitted at the surface were delayed by about 3 s from the origin times of the seismic events. It is suggested that small isotropic inflations excited seismic waves in the crust and simultaneously caused acoustic waves that traveled in the conduit and produced infrasonic pulses at the crater bottom. Considering the observed time differences and gas temperatures emitted from the vent, the conduit should have been filled with vapor mixed with SO₂ gas and volcanic ash. The change of the time differences between the seismic and infrasonic signals suggests that the seismic source became shallower within half a day before the August 18 explosive eruption. We interpret the source process as a fragmentation process of magma in which gas bubbles burst and quickly released part of the pressure that had been sustained by the tensional strength of magma.     

Cause of winter gravity wave spectrum saturation

Gravity waves play a significant role in establishing the large-scale circulation and structure of the middle atmosphere. Through gravity wave saturation proc-esses, such motions are believed to cause turbulence, resulting in divergence of momentum flux and the diffusion of heat and constituents in the meso-sphere[1,2]. The mechanisms that contribute signifi-cantly to the gravity wave saturation are thought to be the dynamical and convective instabilities[3]. However, it is difficult to distin…