Historical effects of temperature and precipitation on California crop yields

For the 1980–2003 period, we analyzed the relationship between crop yield and three climatic variables (minimum temperature, maximum temperature, and precipitation) for 12 major Californian crops: wine grapes, lettuce, almonds, strawberries, table grapes, hay, oranges, cotton, tomatoes, walnuts, avocados, and pistachios. The months and climatic variables of greatest importance to each crop were used to develop regressions relating yield to climatic conditions. For most crops, fairly simple equations using only 2–3 variables explained more than two-thirds of observed yield variance. The types of variables and months identified suggest that relatively poorly understood processes such as crop infection, pollination, and dormancy may be important mechanisms by which climate influences crop yield. Recent climatic trends have had mixed effects on crop yields, with orange and walnut yields aided, avocado yields hurt, and most crops little affected by recent climatic trends. Yield-climate relationships can provide a foundation for forecasting crop production within a year and for projecting the impact of future climate changes.     

Impact of temperature and precipitation variability on crop model predictions

Future climate changes, as well as differences in climates from one location to another, may involve changes in climatic variability as well as changes in means. In this study, a synthetic weather generator is used to systematically change the within-year variability of temperature and precipitation (and therefore also the interannual variability), without altering long-term mean values. For precipitation, both the magnitude and the qualitative nature of the variability are manipulated. The synthetic daily weather series serve as input to four crop simulation models. Crop growth is simulated for two locations and three soil types. Results indicate that average predicted yield decreases with increasing temperature variability where growing-season temperatures are below the optimum specified in the crop model for photosynethsis or biomass accumulation. However, increasing within-year variability of temperature has little impact on year-to-year variability of yield. The influence of changed precipitation variability on yield was mediated by the nature of the soil. The response on a droughtier soil was greatest when precipitation amounts were altered while keeping occurrence patterns unchanged. When increasing variability of precipitation was achieved through fewer but larger rain events, average yield on a soil with a large plant-available water capacity was more affected. This second difference is attributed to the manner in which plant water uptake is simulated. Failure to account for within-season changes in temperature and precipitation variability may cause serious errors in predicting crop-yield responses to future climate change when air temperatures deviate from crop optima and when soil water is likely to be depleted at depth.     

热带太平洋海表温度年际变化对降水季节内振荡的影响

根据 １９８２—１９９２年期间的日平均 ＭＳＵ（Ｓｐｅｎｃｅｒ, １９９３）海洋降水和 ５天平均的ＣＭＡＰ（Ｘｉｅ＆ Ａｒｋｉｎ, １９９７）降水观测资料,分析了热带太平洋大气季节内振荡（ＭＪＯ）的年际变化特征。在太平洋海表温度（ＳＳＴ）年际变化的正常年份（１９８２—８３年, １９８６—８８年, １９９１—９２年）,均有明显的ＭＪＯ信号传到日界线以东并在中、东太平洋维持数月。热带ＭＪＯ活动强度的年际变化与局地ＳＳＴ的变化存在正相关。中、东太平洋降水的季节内振荡的年际变化与热带太平洋ＳＳＴ的最强正相关在Ｎｉｎｏ３区附近。以观测ＳＳＴ场强迫ＣＣＭ３大气模式的数值试验基本上真实地再现了１１年期间热带太平洋降水季节内振荡的年际变化总趋势,但模拟季节内振荡的强度较观测平均偏弱。对比分别采用周平均和月平均ＳＳＴ强迫场的积分结果,发现在中、东太平洋,二个积分模拟的降水季节内振荡强度的年际变化接近并且趋势与观测基本一致,而在西太平洋二个积分的模拟结果差别较大。这表明在热带中、东太平洋,ＳＳＴ强迫的年际变化对ＭＪＯ强度的变化有强的制约。而在ＭＪＯ总体活跃的热带西太平洋,ＳＳＴ强迫场的季节变化对模拟ＭＪＯ活动也有较大影响。ＣＣＭ３模拟     

Impacts of irrigation on dry season precipitation in India

There is a lack of observed data-based studies examining the role of enhanced soil moisture conditions (due to irrigation) on the prevailing precipitation. Therefore, in the present study, we have examined the impacts of the Green Revolution (GR) related expansion of irrigation and changes in dry season (the rabi (November to May) and the zaid (March to June)) precipitation in India. The results for some regions indicated decreasing and increasing trend in precipitation during the pre- and post-GR periods, respectively. For example, in eastern Madhya Pradesh, the pre- and post-GR precipitation trends for the zaid season were ?0.45 and 2.40?mm?year^?1, respectively. On the other hand, some regions reported lower rate of decline in precipitation during the post-GR period. This paper suggests that both positive and lower declining trend during the post-GR period were linked to increased precipitation due to the introduction of irrigation. The study has found up to 69?mm (121%) increase in total amount of precipitation for growing seasons during the post-GR period. Moreover, a 175% increase in average precipitation was also recorded. All irrigated regions show a notable increase in precipitation during post-GR growing seasons. It was found that differences in growing season average precipitation between the pre- and post-GR periods were statistically significant for most of the regions. For further verification of results, the MM5 and Noah land surface model were applied. These applications show changes in precipitation and various precipitation controlling factors due to changes in soil moisture.     

Impacts of increased variability in precipitation and air temperature on net primary productivity of the Tibetan Plateau: a modeling analysis

We analyzed interannual variability (IAV) of precipitation and air temperature over a 40-year period (1969–2008) for 11 sites along a precipitation gradient on the Tibetan Plateau. The observed IAV for both precipitation and air temperature decreases with increasing mean annual precipitation. Using Biome-BGC, a process-based ecosystem model, we simulated net primary production (NPP) along this gradient and find that the IAV of NPP is positively correlated to the IAV of precipitation and temperature. Following projected climate change scenarios for the Tibetan Plateau, our simulations suggest that with increasing IAV of precipitation and temperature, the IAV of NPP will also increase and that climate thresholds exist that, if surpassed, lead to ecosystem die-off. The impacts of these changes on ecosystem processes and climate-vegetation feedbacks on the rapidly warming Tibetan Plateau are potentially quite significant.     

Impacts of aerosol chemical composition on microphysics and precipitation in deep convection

Aerosols affect precipitation by modifying cloud properties such as cloud droplet number concentration (CDNC). Aerosol effects on CDNC depend on aerosol properties such as number concentration, size spectrum, and chemical composition. This study focuses on the effects of aerosol chemical composition on CDNC and, thereby, precipitation in a mesoscale cloud ensemble (MCE) driven by deep convective clouds. The MCE was observed during the 1997 department of energy's Atmospheric Radiation Measurement (ARM) summer experiment. Double-moment microphysics with explicit nucleation parameterization, able to take into account those three properties of aerosols, is used to investigate the effects of aerosol chemical composition on CDNC and precipitation. The effects of aerosol chemical compositions are investigated for both soluble and insoluble substances in aerosol particles. The effects of soluble substances are examined by varying mass fractions of two representative soluble components of aerosols in the continental air mass: sulfate and organics. The increase in organics with decreasing sulfate lowers critical supersaturation (S_c) and leads to higher CDNC. Higher CDNC results in smaller autoconversion of cloud liquid to rain. This provides more abundant cloud liquid as a source of evaporative cooling, leading to more intense downdrafts, low-level convergence, and updrafts. The resultant stronger updrafts produce more condensation and thus precipitation, as compared to the case of 100% sulfate aerosols. The conventional assumption of sulfate aerosol as a surrogate for the whole aerosol mass can be inapplicable for the case with the strong sources of organics. The less precipitation is simulated when an insoluble substance replaces organics as compared to when it replaces sulfate. When the effects of organics on the surface tension of droplet and solution term in the Köhler curve are deactivated by the insoluble substance, S_c is raised more than when the effects of sulfate on the solution term are deactivated by the insoluble substance. This leads to lower CDNC and, thus, larger autoconversion of cloud liquid to rain, providing less abundant cloud liquid as a source of evaporative cooling. The resultant less evaporative cooling produces less intense downdrafts, weaker low-level convergence, updrafts, condensation and, thereby, less precipitation in the case where organics is replaced by the insoluble substance than in the case where sulfate is replaced by the insoluble substance. The variation of precipitation caused by the change in the mass fraction between the soluble and insoluble substances is larger than that caused by the change in the mass fraction between the soluble substances.     

Impacts of extreme precipitation on tree plantation carbon cycle

Extreme precipitation events are expected to increase in frequency and magnitude in future due to global warming, but relevant impacts on tree plantation ecosystem carbon cycle are unknown. In this study, we use an atmosphere–vegetation interaction model (AVIM2) to estimate the likely impacts of extreme precipitation events on carbon fluxes and carbon stocks of a tree plantation in south China. Our results indicate that shifting from moderate precipitation events to extreme precipitation events whilst keeping monthly precipitation unchanged could decrease the tree plantation carbon accumulation. Tree plantation net primary productivity, net ecosystem productivity, soil carbon stock and vegetation carbon stock could decrease by 4.2, 28, 4.3 and 1.4 % during the studying period of 1962–2004, respectively. Though reductions in net primary productivity and net ecosystem productivity are relatively smaller than their annual variations, our sensitivity test shows that the tree plantation carbon stock could decrease by 3.3 % if the assumed extreme precipitation regime lasts for 500 years. Observed and simulated gross primary productivity, ecosystem respiration and net ecosystem productivity have significant positive correlation with soil water content (SWC), especially the deep SWC. The mechanism for the extreme precipitation effect is that the increase in extreme precipitation events will cause SWC to decrease, consequently, reducing carbon fluxes and stocks.     

Distribution of surface ozone concentration in the clean areas of china and its possible impact on crop yields

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台风环流对远距离暴雨水汽输送影响研究

利用NCEP再分析资料,结合WRF模式对2008年7月17—19日发生在山东省的台风远距离暴雨水汽输送过程进行分析。结果表明：台风环流不仅有利于低纬度西太平洋水汽输送到山东内陆地区,而且迫使来自孟加拉湾的气流强度和方向发生变化,进而对远距离降水强度和持续时间产生重大影响;台风环流对鲁东南地区的水汽贡献远大于鲁西南地区,移除台风环流能间接地增强鲁西南地区的水汽供应;台风环流使远距离降水区水汽辐合范围集中,辐合强度增强,从而增强降水强度。     

Impacts of crop residue at the earth-atmosphere interface: Introduction

Summary Crop residues have been an under-valued resource in many agricultural systems. This collection of papers presents a sampling of new research and applications of new knowledge to improve our understanding of crop residue properties and impacts. Development and implementation of improved crop residue management offers opportunities to manipulate hydrologic, radiative, and energy balance processes. I hope the readers of Theoretical and Applied Climatology will be stimulated with new ideas. Collectively our new ideas can advance understanding of crop residue management and help us achieve sustainability in agricultural systems.     

Impact of urbanization on recent temperature and precipitation trends in the Korean peninsula

Urbanization has a significant impact on climate in urban areas. In this study, we investigate urbanization impacts on temperature and precipitation trends in Korean peninsula based on statistical relationship between these trends and local population growth. We found that there is a significant positive correlation between temperature rise and local population growth, indicating that urbanization has a significant contribution to temperature increase in city climate. As for temperature, the population growth in Korean cities is positively correlated with precipitation trend. The positive correlation is higher during summer time when small-scale convective activity is dominant. Furthermore, it is demonstrated that the correlation is significantly increased when stations in rural areas and small cities are excluded. Such nonlinear relation between precipitation and urbanization is also discussed.     

Assessing the site-specific impacts of climate change on hydrology, soil erosion and crop yields in the Loess Plateau of China

Climate changes may have great impacts on the fragile agro-ecosystems of the Loess Plateau of China, which is one of the most severely eroded regions in the world. We assessed the site-specific impacts of climate change during 2010?C2039 on hydrology, soil loss and crop yields in Changwu tableland region in the Loess Plateau of China. Projections of four climate models (CCSR/NIES, CGCM2, CSIRO-Mk2 and HadCM3) under three emission scenarios (A2, B2 and GGa) were used. A simple spatiotemporal statistical method was used to downscale GCMs monthly grid outputs to station daily weather series. The WEPP (Water and Erosion Prediction Project) model was employed to simulate the responses of agro-ecosystems. Compared with the present climate, GCMs projected a ?2.6 to 17.4% change for precipitation, 0.6 to 2.6°C and 0.6 to 1.7°C rises for maximum and minimum temperature, respectively. Under conventional tillage, WEPP predicted a change of 10 to 130% for runoff, ?5 to 195% for soil loss, ?17 to 25% for wheat yield, ?2 to 39% for maize yield, ?14 to 18% for plant transpiration, ?8 to 13% for soil evaporation, and ?6 to 9% for soil water reserve at two slopes during 2010?C2039. However, compared with conventional tillage under the present climate, conservation tillage would change runoff by ?34 to 71%, and decrease soil loss by 26 to 77% during 2010?C2039, with other output variables being affected slightly. Overall, climate change would have significant impacts on agro-ecosystems, and adoption of conservation tillage has great potential to reduce the adverse effects of future climate changes on runoff and soil loss in this region.     

基于WRF的积云对流参数化方案对中国夏季降水预报的影响研究

为了研究WRF(Weather Research and Forecasting)中尺度模式中积云对流参数化方案对夏季降水预报的影响,基于水平分辨率为9 km的WRF模式,采用Kain-Fritsch(KF)、尺度适应的KF、Tiedtke、new Tiedtke和尺度适应的new Tiedtke方案等5种积云对流参数...     

Spatial impact of projected changes in rainfall and temperature on wheat yields in Australia

Climate projections over the next two to four decades indicate that most of Australia’s wheat-belt is likely to become warmer and drier. Here we used a shire scale, dynamic stress-index model that accounts for the impacts of rainfall and temperature on wheat yield, and a range of climate change projections from global circulation models to spatially estimate yield changes assuming no adaptation and no CO₂ fertilisation effects. We modelled five scenarios, a baseline climate (climatology, 1901–2007), and two emission scenarios (“low” and “high” CO₂) for two time horizons, namely 2020 and 2050. The potential benefits from CO₂ fertilisation were analysed separately using a point level functional simulation model. Irrespective of the emissions scenario, the 2020 projection showed negligible changes in the modelled yield relative to baseline climate, both using the shire or functional point scale models. For the 2050-high emissions scenario, changes in modelled yield relative to the baseline ranged from ?5 % to +6 % across most of Western Australia, parts of Victoria and southern New South Wales, and from ?5 to ?30 % in northern NSW, Queensland and the drier environments of Victoria, South Australia and in-land Western Australia. Taking into account CO₂ fertilisation effects across a North–south transect through eastern Australia cancelled most of the yield reductions associated with increased temperatures and reduced rainfall by 2020, and attenuated the expected yield reductions by 2050.     

降水和风对泰安地区PM2.5浓度的影响及区域传输研究

利用泰安市2018—2019年降水、风和PM2.5逐小时观测数据,分析了降水和风对PM2.5浓度的影响,并对PM2.5进行了源解析.结果表明:降水对PM2.5有一定清除作用,降雨日PM2.5平均质量浓度较非降雨日平均降低约7.2％,秋冬季节最为显著.降水对PM2.5的清除率与降水强度、降水前PM2.5初始浓度及降水时间...     

CWRF对青藏高原气温和降水模拟效果的综合评估

利用CWRF(Climate-Weather Research and Forecasting model)对中国区域气候的31 a多物理集合模拟试验,分析了该模式对青藏高原气温和降水的模拟效果及其对水平分辨率和物理过程参数化方案的敏感性.结果表明:1)CWRF降尺度全面改善了全球模式对高原气温和降水的模拟,使气温年循...     

Impacts of climate change on crop evapotranspiration with ensemble GCM projections in the North China Plain

As one of the key grain-producing regions in China, the agricultural system in the North China Plain (NCP) is vulnerable to climate change due to its limited water resources and strong dependence on irrigation for crop production. Exploring the impacts of climate change on crop evapotranspiration (ET) is of importance for water management and agricultural sustainability. The VIP (Vegetation Interface Processes) process-based ecosystem model and WRF (Weather Research and Forecasting) modeling system are applied to quantify ET responses of a wheat-maize cropping system to climate change. The ensemble projections of six General Circulation Models (GCMs) under the B2 and A2 scenarios in the 2050s over the NCP are used to account for the uncertainty of the projections. The thermal time requirements (TTR) of crops are assumed to remain constant under air warming conditions. It is found that in this case the length of the crop growth period will be shortened, which will result in the reduction of crop water consumption and possible crop productivity loss. Spatially, the changes of ET during the growth periods (ET_g) for wheat range from ?7 to 0 % with the average being ?1.5?±?1.2 % under the B2 scenario, and from ?8 to 2 % with the average being ?2.7?±?1.3 % under the A2 scenario/consistently, changes of ET_g for maize are from ?10 to 8 %, with the average being ?0.4?±?4.9 %, under the B2 scenario and from ?8 to 8 %, with the average being ?1.2?±?4.1 %, under the A2 scenario. Numerical analysis is also done on the condition that the length of the crop growth periods remains stable under the warming condition via breeding new crop varieties. In this case, TTR will be higher and the crop water requirements will increase, with the enhancement of the productivity. It is suggested that the options for adaptation to climate change include no action and accepting crop loss associated with the reduction in ET_g, or breeding new cultivars that would maintain or increase crop productivity and result in an increase in ET_g. In the latter case, attention should be paid to developing improved water conservation techniques to help compensate for the increased ET_g.     

Sensitivity of crop yields and land resource potential to climatic change in Ontario,Canada

Increasing concentrations of atmospheric CO₂ and other greenhouse gases are expected to contribute to a global warming. This paper examines the potential implications of a climatic change corresponding to a doubling of atmospheric concentrations of CO₂ on crop production opportunities throughout Ontario, a major food producing region in Canada. The climate is projected to become warmer and drier, but the extent of these shifts are expected to vary from region to region within Ontario. The effect of this altered climate on crop yields and the area of land capable of supporting specific crops varies according to region, soil quality and crop type. Most notable are the enhanced opportunities for grains and oilseeds in the northern regions, and the diminished production prospects for most crops in the most southerly parts of Ontario.