Large-Eddy Simulations of the Baroclinic Mixed Layer

The effects of baroclinicity, imposed on the dry mixed layer by the presenceof large-scale, horizontal temperature gradients, have been investigated basedon a large-eddy simulation model. The purpose of this investigation is to examinesimultaneous impacts of thermal stratification and shear in the atmospheric boundarylayer. For this purpose, five cases are considered – one barotropic, and four baroclinic.Based on the performed simulations, a new parametrization of the interfacial layer isproposed. The parameterization employs new interfacial scaling, which is valid at thetop of the mixed layer. In terms of new scales, dimensionless moments characterizingturbulence at the top of the shearless mixed layer are universal constants. In the shearedcase, dimensionless statistics of turbulence are shown to be functions of the interfacialRichardson number.     

Problems in determining spatial inhomogeneity of <Superscript>137</Superscript>Cs fallout for estimating rates of erosion-accumulative processes

The issues of assessing variability of ¹³⁷Cs fallout of global and Chernobyl origin at reference sites are discussed with a purpose to use this isotope as a tracer for estimating the rates of erosion-accumulative processes. It is shown that local variability of soil contamination by ¹³⁷Cs at reference sites is within 7–20%, which makes it possible to use the isotope as a tracer. When studies are conducted within drainage basins, the available trend of the atmospheric ¹³⁷Cs fallout should be taken into account in assessing the soil and sedimentation redistribution.     

From impacts assessment to adaptation priorities: the shaping of adaptation policy

Abstract

Under the United Nations Framework Convention on Climate Change (UNFCCC), adaptation has recently gained importance, yet adaptation is much less developed than mitigation as a policy response. Adaptation research has been used to help answer to related but distinct questions. (1) To what extent can adaptation reduce impacts of climate change? (2) What adaptation policies are needed, and how can they best be developed, applied and funded? For the first question, the emphasis is on the aggregate value of adaptation so that this may be used to estimate net impacts. An important purpose is to compare net impacts with the costs of mitigation. In the second question, the emphasis is on the design and prioritisation of adaptation policies and measures. While both types of research are conducted in a policy context, they differ in their character, application, and purpose. The impacts/mitigation research is orientated towards the physical and biological science of impacts and adaptation, while research on the ways and means of adaptation is focussed on the social and economic determinants of vulnerability in a development context. The main purpose of this paper is to demonstrate how the national adaptation studies carried under the UNFCCC are broadening the paradigm, from the impacts/mitigation to vulnerability/adaptation. For this to occur, new policy research is needed. While the broad new directions of both research and policy can now be discerned, there remain a number of outstanding issues to be considered.     

Estimating Global Distribution of Evapotranspiration and Water Balance Using Complementary Methods

ABSTRACT

The authors propose a modified complementary method to estimate regional evapotranspiration (ET) under different climatic and physical conditions using only meteorological data. The purpose of this study is to investigate the applicability of the modified complementary method for estimating global ET distribution and corresponding water balance. Gridded data from the Climate Research Unit, University of East Anglia, with 30 min spatial resolution and monthly time steps are used. Using the Thornthwaite water budget, monthly maps of global water surplus (precipitation minus ET) are produced. The results show good agreement with many previous studies. The average annual precipitation, ET, and water surplus are 690, 434, and 256?mm, respectively. The results show that the modified model can predict regional ET using meteorological data and can be used to assess global water resources. Consequently, the proposed method has strong potential for projecting water resource balance under future climate change.     

Gas chromatographic determination of peroxyacetyl nitrate: Two convenient calibration techniques

Two procedures for the calibration of an electron capture detector (ECD) for peroxyacetyl nitrate (PAN) are discussed. One is based on the first-order decay rate of the the PAN mixing ratio in conditioned glass storage vessels. The other method makes use of the photochemical generation of PAN in mixtures of acetone and NO₂ in air. For this purpose a Penray Hg lamp was inserted into a glass vessel filled with 1 atmosphere of air containing 10 ppm NO₂ and 1% acetone. After 3 min of irradiation, the average PAN mixing ratio formed was 8.87±0.25 ppmv as determined in six separate runs.     

The measurement of hait at ground level

Abstract

The purpose of this study was to measure, with the help of a sensor measuring the impact of hailstones, the physical characteristics of hailfalls point‐by‐point, and to extend these measurements to a larger surrounding area.

The results of calibrations and data‐handling methods, applying to a type of hailpad used in France and in Switzerland, are presented. The sources of error due to the pad, to the natural variability of the hailfalls and to the integration of the data over area are then reviewed.     

DJM10湿度检定箱加湿不能自控的原因浅析

详细介绍了新型湿度检定箱内部气路原理及升降湿外围控制原理，并给出故障检修实例 ,供设备检定人员在维修工作中参考。     

The use of an index-based regression model for precipitation analysis on the Iberian peninsula

Summary  A large number of atmospheric circulation classification techniques have been developed in the investigation of synoptic controls on regional rainfall. Often the rationale is to aid efforts to downscale GCM output for the purpose of producing more confident climate change impact scenarios. Discrete weather typing techniques, although proven to be successful do not capture weather type intensity and within-type variability can often be high. In this study an objective indexing method, developed for Egypt and the British Isles area is applied to the Iberian peninsula. Air flow index values are then used as predictor variables in simple linear regression models to estimate monthly mean grid point rainfall amounts. Separate models are evaluated for the winter and summer halves of the year and also for surface and mid-tropospheric flow (500 hPa). The models are evaluated and compared indicating that the index values provide good estimation of rainfall but variability in performance between season and site is noted. Received February 10, 2000     

Insolation in terms of Earth's orbital parameters

Summary The solar insolation at any point on the Earth can be expressed in terms of the latitude and longitude of that point and the parameters of the Earth's orbit. The derivation of such an equation is given here. One purpose of the equation is to gain theoretical insights into how the insolation varies on the time scales of the Milankovitch cycles. The most easily attained insights are that neither the main pacemaker of the ice agese, nor Milankovitch's precession indexe sin appear as terms in the equation (e is the eccentricity of the Earth's orbit and is the argument of perihelion.) Obliquity does appear. These results are already well-known, but are easily derived when the insolation is formulated as given here. The equation also suggests expressing the Earth's albedo in the same form as the insolation. When this is done a term which looks likee sin can be made to appear, for example, multiplied by an albedo coefficient and lagged in phase. However, the term is small, of the order ofe ². Besides theoretical insights, a second purpose of the equation is to provide a convenient formula for computing insolation when using numerical climate models. Its usefulness to this end is yet to be established.With 3 Figures     

On the Origin of Near-Surface Streaks in the Neutrally-Stratified Planetary Boundary Layer

The dynamics of near-surface streak formation in the neutrallystratified, rotating planetary boundary layer areinvestigated. The purpose of this note is to compare large-eddysimulation results to theoretical predictions suggesting thatstreaks are associated with non-normal mode optimal perturbations.Streaks are regions near the surface of alternating high and lowspeed fluid organized into nearly linear bands, with horizontalspacing of several hundred metres, oriented up to 30° relativeto the geostrophic wind, that evolve through a continuous cycle ofgeneration, growth, decay and reformation. We find that the earlystages of streak formation and growth are consistent with thelinear theory.     

The reliability of global and hemispheric surface temperature records

The purpose of this review article is to discuss the development and associated estimation of uncertainties in the global and hemispheric surface temperature records. The review begins by detailing the groups that produce surface temperature datasets. After discussing the reasons for similarities and differences between the various products, the main issues that must be addressed when deriving accurate estimates, particularly for hemispheric and global averages, are then considered.These issues are discussed in the order of their importance for temperature records at these spatial scales: biases in SST data,particularly before the 1940s; the exposure of land-based thermometers before the development of louvred screens in the late 19th century; and urbanization effects in some regions in recent decades. The homogeneity of land-based records is also discussed; however, at these large scales it is relatively unimportant. The article concludes by illustrating hemispheric and global temperature records from the four groups that produce series in near-real time.     

A postulate of electric multipoles in growing ice crystals: Their role in the formation of ice crystal aggregates

This paper describes the basis of the postulate of electric multipoles in growing ice crystals. The postulate was initially developed to describe the orientation of aggregated ice crystals, for the purpose of learning about rate-determining forces involved in the initiation of ice crystal aggregation.A series of laboratory experiments were undertaken to test the postulate. A 6.7-m³ controlled-temperature chamber was used to investigate the aggregation of growing ice crystals. The results show that small changes in dissolved salts are important in the orientation of initial ice crystal aggregates. We interpret these results to strongly support our hypothesis of electric multipoles in growing ice crystals.     

Mean stresses and velocities in the neutral,barotropic planetary boundary layer

The purpose of the paper is to find the mean velocities and stresses in the turbulent, neutral, barotropic planetary boundary layer (PBL). Correction functions are introduced similar to those used by Millikan and Hinze in discussions of flows in a pipe and in a turbulent boundary layer. The functions for the PBL are determined semi-empirically and, with a choice of constants, the resulting velocity distributions are in reasonable agreement with the Leipzig profile. The paper also discusses the correction functions for pipe and boundary-layer flows and for plane Couette flow. The results are in excellent agreement with observations.     

基于农业物联网技术的农田“四情”感知决策体系的构建

围绕可持续的绿色精准农业这一目标,针对农田"四情"(苗情、墒情、病虫情、灾情)监测的物联网应用,从农作物生产过程的信息获取、传输、处理、服务4个层面上构建物联网应用系统,内容涉及农田的苗情、墒情、病虫情和灾情的感知,低功耗低成本自组织的无线传输网络,强大处理能力的云服务支撑平台和农作物生产管理决策系统,实现实时监测预警,病虫害防治和灾情评估等功能,为提升农业综合生产能力、抵御自然灾害风险,发展优质高产高效现代农业提供技术支撑.     

Design rainfall depth estimation through two regional frequency analysis methods in Hanjiang River Basin, China

Hydrological predictions in ungauged basins are of significant importance for water resources management. In hydrological frequency analysis, regional methods are regarded as useful tools in estimating design rainfall/flood for areas with only little data available. The purpose of this paper is to investigate the performance of two regional methods, namely the Hosking’s approach and the cokriging approach, in hydrological frequency analysis. These two methods are employed to estimate 24-h design rainfall depths in Hanjiang River Basin, one of the largest tributaries of Yangtze River, China. Validation is made through comparing the results to those calculated from the provincial handbook approach which uses hundreds of rainfall gauge stations. Also for validation purpose, five hypothetically ungauged sites from the middle basin are chosen. The final results show that compared to the provincial handbook approach, the Hosking’s approach often overestimated the 24-h design rainfall depths while the cokriging approach most of the time underestimated. Overall, the Hosking’ approach produced more accurate results than the cokriging approach.     

Uncertainty analysis for estimation of landfill emissions and data sensitivity for the input variation

Results of research and practical experience confirm that stabilization of GHG concentrations will require a tremendous effort. One of the sectors identified as a significant source of methane (CH₄) emissions are solid waste disposal sites (SWDS). Landfills are the key source of CH₄ emissions in the emissions inventory of Slovakia, and the actual emission factors are estimated with a high uncertainty level. The calculation of emission uncertainty of the landfills using the more sophisticated Tier 2 Monte Carlo method is evaluated in this article. The software package that works with the probabilistic distributions and their combination was developed with this purpose in mind. The results, sensitivity analysis, and computational methodology of the CH₄ emissions from SWDS are presented in this paper.     

Does the Aral sea merit heritage status?

In November 1972, the United Nations developed the World Heritage Convention in recognition of the need for protecting valuable cultural and natural sites of global importance. The convention was designed to identify and protect heritage sites worldwide. Although the Aral Sea has not yet been proposed by any of the Central Asian states as a world heritage site, it meets many of the criteria designated by the Convention as a site meriting such status. The purpose of this paper is threefold. First, the notion of heritage and its application to world heritage status are discussed. Second, this notion is applied to the Aral Sea Basin in Central Asia in an attempt to answer the question, ‘Does the Aral Sea merit heritage status?’. Finally, ‘environmental Justice’ issues, which might arise as a result of such a designation, are discussed.     

Societal response to CO2-induced climate change: Opportunities for research

How might a climate change, induced by increased CO₂ in the atmosphere, affect societies? What is the range of existing and potential mechanisms for societal response? And how might research contribute to a reduction of the adverse impact (or enhancement of the unique opportunities) of a climate change by providing greater understanding of the processes involved in climate and society interaction? This paper reflects an initial effort to shed light on these questions. It offers first a framework for identifying key issues in climate-society interaction; eight major questions are suggested by the framework. A discussion of each major question is then presented with the purpose of reviewing the current state of knowledge, identifying the gaps in understanding, and offering opportunities for research to fill those gaps. In all, twenty-two research needs are outlined and are summarized at the conclusion of the paper. The perspective is inter-disciplinary, but the review draws heavily from the geographic literature, reflecting the disciplinary bias of the authors.     

卡尔曼滤波的初值计算方法及其应用

文章从气象应用角度论述了卡尔曼滤波在天气预报业务系统中应用的理论原理和计算方法。介绍了不同季节的试验结果，并分析了卡尔曼滤波的适应数值模式变化的能力和它的稳定性、可用性，展示了它的优越性和应用前景。