The steady‐state structure of the natural stratosphere and ozone distribution in a 2‐D model incorporating radiation and O‐H‐N photochemistry and the effects of stratospheric pollutants

A mean meridional circulation model of the stratosphere, incorporating radiative heating and photochemistry of the oxygen‐hydrogen‐nitrogen atmosphere, is used to simulate the meridional distributions of O₃, HO_X, N₂O,NO_X, temperature and the three components of mean motion for the summer and winter seasons under steady‐state conditions. The results are generally in good agreement with the available observations in the normal stratosphere. The model has been applied to assess the effects of water vapour and nitrogen oxide perturbations resulting from aircraft emissions in the stratosphere. It is found that a fleet of 500 Boeing‐type sst's, flying at 20 km and 45°N in the summer hemisphere and inserting NO_x at a rate of 1.8 megatons per year, has the effect of reducing the global total ozone by 14.7%. Similar calculations for 342 Concorde/TU‐114's, cruising at 17 km and injecting NO_x at a rate of 0.35 megatons per year, show a global‐average total‐ozone reduction of 1.85%. Although water vapour is considered important, because of its ability to convert NO₂ into HNO₃, the direct effect on global‐average total‐ozone reduction resulting from the 100% increase in the stratospheric water content is less than 1%. The changes in the chemical structure (HO^NO^), temperature, and mean motions associated with the ozone reduction are also investigated in the case of the 1.8‐megaton‐per‐year NO_X perturbation. It is shown that the reduced meridional temperature gradient in the middle and upper stratosphere resulting from the NO_x perturbation leads to the weakening of the tropical easterly jet in the summer hemisphere and mid‐latitude westerlies in the winter season.

The sensitivity of the model solutions to an alternate choice of input parameters (diffusion coefficients and solar photodissociation data) is tested and the main deficiency of the model is pointed out.     

A cloud layer‐sunshine model for estimating direct,diffuse and total solar radiation

A previous study (Suckling and Hay, 1976a) described a method for calculating hourly values of the direct and diffuse solar radiation for cloudless sky conditions. This paper presents an extension which incorporates the effects of clouds through the use of hourly values of cloud amount and type for up to four layers and hourly bright sunshine totals. The latter data provide a more accurate measure of the length of time the direct radiation of the sun is not attenuated by cloud. On an average, the cloud layer‐sunshine (CLS) model estimated daily total solar radiation at five Canadian locations to within ±15 per cent of the measured values. This was an improvement over an earlier model (Davies et al., 1975) based on cloud data alone, but the relative advantage, as well as the overall errors themselves, were diminished as the averaging period was increased to five and ten days. The CLS model has the additional advantage of calculating the separate direct and diffuse components of the total solar radiation.     

A statistical relationship between solar radiation,’ sunshine and relative humidity in the tropics

A correlation of solar radiation i n tropical countries has been established based on parameters more usually measured than solar radiation itself. The following empirical relationships between solar radiation Q, ratio of hours of bright sunshine to twelve hours, S, and relative humidity of the environment, R, have been obtained by statistical methods applied to the available data:

Q = 490S^0.357R^‐0.262

Q = 460e^0.607(S‐R)

Q = 464 + 265S ‐ 248R

with limits on R and S as defined in the text. It is found that these equations give better estimates of solar radiation than the single‐parameter relationship like

Q = a + bS

where a and b are statistical coefficients.     

Drought in Northeast Brazil—past,present, and future

This study provides an overview of the drought situation in Northeast Brazil for the past, present, and future. Droughts affect more people than any other natural hazard owing to their large scale and long-lasting nature. They are recurrent in the region and while some measures have been taken by the governments to mitigate their impacts, there is still a perception that residents, mainly in rural areas, are not yet adapted to these hazards. The drought affecting the Northeast from 2012 to 2015, however, has had an intensity and impact not seen in several decades and has already destroyed large swaths of cropland, affecting hundreds of cities and towns across the region, and leaving ranchers struggling to feed and water cattle. Future climate projections for the area show large temperature increases and rainfall reductions, which, together with a tendency for longer periods with consecutive dry days, suggest the occurrence of more frequent/intense dry spells and droughts and a tendency toward aridification in the region. All these conditions lead to an increase in evaporation from reservoirs and lakes, affecting irrigation and agriculture as well as key water uses including hydropower and industry, and thus, the welfare of the residents. Integrating drought monitoring and seasonal forecasting provides efficient means of assessing impacts of climate variability and change, identifying vulnerabilities, and allowing for better adaptation measures not only for medium- and long-term climate change but also for extremes of the interannual climate variability, particularly droughts.

     

The self-organizing methods of long-term forecasting (I) — GMDH and GMPSC model

Summary First, the Group Method of Data Handling (GMDH) algorithm, a self-organizing method for constructing higher order regression, is applied to build a model for long-term forecasting. Then, the Group Method of Phase Space Component (GMPSC) model is set up based on chaos theory and GMDH. Several case studies show that both GMDH and GMPSC provide an efficient and potentially useful tool for non-linear time series modeling.Supported by the NKPFR Climate Dynamics and Climate Prediction Theory.     

Solar dimming and its impact on estimating solar radiation from diurnal temperature range in China, 1961–2007

The relationship of prolonged dry spells in Eastern Mediterranean with large-scale surface and upper circulation is investigated on seasonal basis with the aid of the Singular-Value Decomposition Analysis (SVDA) for the period 1958–2000. The study was based on daily precipitation data of 56 stations, evenly distributed over Eastern Mediterranean region. Extreme dry spells are defined using the CDD index (maximum number of consecutive dry days). It was found that teleconnection patterns centered over Northern Atlantic and northern Europe seem to affect the duration of the longest dry spells over the Eastern Mediterranean, while surface synoptic scale systems in Northern Africa play a substantial role. The SVDA results compare well with the corresponding results of Canonical Correlation Analysis (CCA), mainly for the surface circulation during winter and summer.     

Contributions of individual variation in temperature, solar radiation and precipitation to crop yield in the North China Plain, 1961–2003

An understanding of the relative impacts of the changes in climate variables on crop yield can help develop effective adaptation strategies to cope with climate change. This study was conducted to investigate the effects of the interannual variability and trends in temperature, solar radiation and precipitation during 1961–2003 on wheat and maize yields in a double cropping system at Beijing and Zhengzhou in the North China Plain (NCP), and to examine the relative contributions of each climate variable in isolation. 129 climate scenarios consisting of all the combinations of these climate variables were constructed. Each scenario contained 43 years of observed values of one variable, combined with values of the other two variables from each individual year repeated 43 times. The Agricultural Production Systems Simulator (APSIM) was used to simulate crop yields using the ensemble of generated climate scenarios. The results showed that the warming trend during the study period did not have significant impact on wheat yield potential at both sites, and only had significant negative impact on maize yield potential at Beijing. This is in contrast with previous results on effect of warming. The decreasing trend in solar radiation had a much greater impact on simulated yields of both wheat and maize crops, causing a significant reduction in potential yield of wheat and maize at Beijing. Although decreasing trends in rainfed yield of both simulated wheat and maize were found, the substantial interannual variability of precipitation made the trends less prominent.     

On the relationship between cloud–radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model

We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed.     

Greenhouse effect and altitude gradients over the Alps – by surface longwave radiation measurements and model calculated LOR

Summary The greenhouse effect has been investigated predominantly with satellite measurements, but more than 90% of the greenhouse radiative flux affecting Earths surface temperature and humidity originates from a 1000 meter layer above the surface. Here we show that substantial improvements on surface longwave radiation measurements and very good agreement with radiative transfer model calculations allow the clear-sky greenhouse effect be determined with measured surface longwave radiation and calculated longwave outgoing radiation at the top of the atmosphere. The cloud radiative forcing is determined by measured net longwave fluxes and added to the clear-sky greenhouse effect to determine the all-sky greenhouse effect. Longwave radiation measurements at different altitudes were used to determine the clear-sky and all-sky annual and seasonal greenhouse effect and altitude gradients over the Alps. Linear altitude gradients are measured for clear-sky situations, whereas the all-sky greenhouse effect is strongly influenced by varying, cloud amounts at different altitudes. Large diurnal and seasonal variations show the importance of surface heating and cooling effects and demonstrate the strong coupling of the greenhouse effect to surface temperature and humidity.     

A new building energy model coupled with an urban canopy parameterization for urban climate simulations—part I. formulation, verification, and sensitivity analysis of the model

The generation of heat in buildings, and the way this heat is exchanged with the exterior, plays an important role in urban climate. To analyze the impact on urban climate of a change in the urban structure, it is necessary to build and use a model capable of accounting for all the urban heat fluxes. In this contribution, a new building energy model (BEM) is developed and implemented in an urban canopy parameterization (UCP) for mesoscale models. The new model accounts for: the diffusion of heat through walls, roofs, and floors; natural ventilation; the radiation exchanged between indoor surfaces; the generation of heat due to occupants and equipments; and the consumption of energy due to air conditioning systems. The behavior of BEM is compared to other models used in the thermal analysis of buildings (CBS-MASS, BLAST, and TARP) and with another box-building model. Eventually, a sensitivity analysis of different parameters, as well as a study of the impact of BEM on the UCP is carried out. The validations indicate that BEM provides good estimates of the physical behavior of buildings and it is a step towards a modeling tool that can be an important support to urban planners.     

The Kwinana Coastal Fumigation Study: I – Program Overview, Experimental Design and Selected Results

Fumigation under sea-breeze conditions is a major feature of the air pollution meteorology in the coastal industrial region of Kwinana, south of Perth in Western Australia. An intensive field experiment on fumigation was carried out in the region in early 1995 with the objective of using the measured data to develop and test a shoreline fumigation model. Fumigation of plumes from the Kwinana Power Station was studied using an instrumented research aircraft, radiosonde balloons, meteorological stations, a lidar, a mobile surface sampler, and sonic anemometers. The study has yielded a detailed and high quality data set as a result of both the range of observations undertaken and of the regularity of the sea-breeze conditions under scrutiny. The details of the experiment are summarised in this paper and some typical results are presented.     

Further analysis of singular vector and ENSO predictability in the Lamont model—Part I: singular vector and the control factors

In this study, singular vector analysis was performed for the period from 1856 to 2003 using the latest Zebiak–Cane model version LDEO5. The singular vector, representing the optimal growth pattern of initial perturbations/errors, was obtained by perturbing the constructed tangent linear model of the Zebiak–Cane model. Variations in the singular vector and singular value, as a function of initial time, season, ENSO states, and optimal period, were investigated. Emphasis was placed on exploring relative roles of linear and nonlinear processes in the optimal perturbation growth of ENSO, and deriving statistically robust conclusions using long-term singular vector analysis. It was found that the first singular vector is dominated by a west–east dipole spanning most of the equatorial Pacific, with one center located in the east and the other in the central Pacific. Singular vectors are less sensitive to initial conditions, i.e., independence of seasons and decades; while singular values exhibit a strong sensitivity to initial conditions. The dynamical diagnosis shows that the total linear and nonlinear heating terms play opposite roles in controlling the optimal perturbation growth, and that the linear optimal perturbation is more than twice as large as the nonlinear one. The total linear heating causes a warming effect and controls two positive perturbation growth regions: one in the central Pacific and the other in the eastern Pacific; whereas the total linearized nonlinear advection brings a cooling effect controlling the negative perturbation growth in the central Pacific.     

Editorial Statement——Action and Policy

On 16 March 2004, we received an appeal from Dr. Qing WANG of the United States‘ Naval Postgraduate School questioning the legitimacy of the paper entitled, Modeling Marine Stratocumulus with a Detailed Microphysical Scheme, that was published by ZHAO Chunsheng and Yutaka Ishizaka in the January 2004 issue of the Advances in Atmospheric Sciences (AAS). She pointed out that the model described in the paper was developed by her group in which the first author, Dr. Zhao, worked as a visiting scholar during February 1997-February 1998.     

南海夏季风撤退期的气候特征I——40年平均

近年来广州地区的气溶胶污染日趋严重,灰霾天气主要出现在10月～次年4月。大气灰霾导致能见度恶化。自1980年代初开始,该地区的能见度急剧恶化,灰霾天气显著增加,其中有3次大的波动,分别代表广州地区经济发展相伴随的粉尘污染、硫酸盐加粉尘污染、光化学过程的细粒子加硫酸盐加粉尘的复合污染时期。雾和轻雾造成的低能见度的长期变化趋势,没有由于人类活动影响或经济发展影响带来的趋势性变化,其波动主要反映了气候波动固有的年际和年代际变化。广州地区能见度的恶化主要与细粒子有关,PM10有一半季均值超过国家二级标准的日均值浓度限值,而PM2.5季均值全部超过美国国家标准的日均值浓度限值,细粒子浓度甚高。另外PM2.5占PM10的比重非常高,可达62%～69%,尤其是旱季比雨季更高。     

Downward longwave radiation estimates for clear and all-sky conditions in the Sertãozinho region of São Paulo, Brazil

The accurate estimate of the surface longwave fluxes contribution is important for the calculation of the surface radiation budget, which in turn controls all the components of the surface energy budget, such as evaporation and the sensible heat fluxes. This study evaluates the performance of the various downward longwave radiation parameterizations for clear and all-sky days applied to the Sertãozinho region in São Paulo, Brazil. Equations have been adjusted to the observations of longwave radiation. The adjusted equations were evaluated for every hour throughout the day and the results showed good fits for most of the day, except near dawn and sunset, followed by nighttime. The seasonal variation was studied by comparing the dry period against the rainy period in the dataset. The least square linear regressions resulted in coefficients equal to the coefficients found for the complete period, both in the dry period and in the rainy period. It is expected that the best fit equation to the observed data for this site be used to produce estimates in other regions of the State of São Paulo, where such information is not available.     

时间依赖的多尺度背景误差协方差研究I——构造

为了在资料同化中更好地应用多尺度同化技术,针对当前GRAPES多尺度3D-Var同化系统中背景误差协方差设置的缺陷,探讨如何引入随时间演变的多尺度信息的方法。首先,基于GRAPES模式集合预报系统,利用集合预报结果构造了新型的背景误差协方差,该新型协方差的标准差与相关关系能随着时间演变而发生变化,即具有时间依赖特征。然后,为了考虑背景误差协方差的多尺度特征,针对不同尺度背景场将该新型协方差进行不同程度的缩放,即假设不同尺度的背景误差单变量标准差与相关尺度以及多变量相关系数与原估计值之间存在一定的比例关系。通过选择不同的缩放系数,其对应的分析增量将产生不同量值与尺度的变化,即可对相应的分析场进行多尺度调整。      

Impacts of greenhouse gases and aerosol direct and indirect effects on clouds and radiation in atmospheric GCM simulations of the 1930–1989 period

Among anthropogenic perturbations of the Earths atmosphere, greenhouse gases and aerosols are considered to have a major impact on the energy budget through their impact on radiative fluxes. We use three ensembles of simulations with the LMDZ general circulation model to investigate the radiative impacts of five species of greenhouse gases (CO₂, CH₄, N₂O, CFC-11 and CFC-12) and sulfate aerosols for the period 1930–1989. Since our focus is on the atmospheric changes in clouds and radiation from greenhouse gases and aerosols, we prescribed sea-surface temperatures in these simulations. Besides the direct impact on radiation through the greenhouse effect and scattering of sunlight by aerosols, strong radiative impacts of both perturbations through changes in cloudiness are analysed. The increase in greenhouse gas concentration leads to a reduction of clouds at all atmospheric levels, thus decreasing the total greenhouse effect in the longwave spectrum and increasing absorption of solar radiation by reduction of cloud albedo. Increasing anthropogenic aerosol burden results in a decrease in high-level cloud cover through a cooling of the atmosphere, and an increase in the low-level cloud cover through the second aerosol indirect effect. The trend in low-level cloud lifetime due to aerosols is quantified to 0.5 min day^–1 decade^–1 for the simulation period. The different changes in high (decrease) and low-level (increase) cloudiness due to the response of cloud processes to aerosols impact shortwave radiation in a contrariwise manner, and the net effect is slightly positive. The total aerosol effect including the aerosol direct and first indirect effects remains strongly negative.