A Modeling Study of Climate Change and Its Implication for Agriculture in China Part II: The Implication of Climate Change for Agriculture in China

The potential CO2-induced impacts on the geographical shifts of wheat growth zones in China were studied from seven GCMs outputs. The wheat growth regions may move northward and westward under the condition of a doubling CO2 climate. The wheat cultivation features and variety types may also assume significant changes. Climatic warming would have a positive influence in Northeast China, but high temperature stress may be produced in some regions of central and southern China. Higher mean air temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing and more heat-tolerant cultivars.     

MM5 Simulations of the China Regional Climate During the LGM.Ⅰ: Influence of CO2 and Earth Orbit Change

Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative Last Glacial Maximum (LGM) climate response to different mechanisms over China. Model simulations of the present day (PD) climate and the LGM climate change are in good agreement with the observation data and geological records, especially in the simulation of precipitation change. Under the PD and LGM climate, changes of earth orbital parameters have a small influence on the annual mean temperature over China.However, the magnitude of the effect shows a seasonal pattern, with a significant response in winter. Thus,this influence cannot be neglected. During the LGM, CO2 concentration reached its lowest point to 200 ppmv. This results in a temperature decrease over China. The influences of CO2 concentration on climate show seasonal and regional patterns as well, with a significant influence in winter. On the contrary, CO2concentration has less impact in summer season. In some cases, temperature even increases with decreasing in CO2 concentration. This temperature increase is the outcome of decrease in cloud amount; hence increase the solar radiation that reached the earth's surface. This result suggests that cloud amount plays a very important role in climate change and could direct the response patterns of some climate variables such as temperature during certain periods and over certain regions. In the Tibetan Plateau, the temperature responses to changes of the above two factors are generally weaker than those in other regions because the cloud amount in this area is generally more than in the other areas. Relative to the current climate, changes in orbital parameters have less impact on the LGM climate than changes in CO2 concentration. However,both factors have rather less contributions to the climate change in the LGM. About 3%-10% changes in the annual mean temperature are contributed by CO2.     

Simulated Spatiotemporal Characteristics of Climate Change in China during the Han Dynasty(1–200 A.D.)

In this study,a 2000-year simulation forced by transient,external forcings is carried out with the Community Earth System Model.The authors investigate the spatiotemporal features of climate change in the Han Dynasty(1–200 A.D.)using the empirical orthogonal function(EOF)method.The leading EOF mode of the annua mean temperature anomalies shows a uniform variation of temperature over the whole of China,while the second EOF mode indicates opposite variations of temperature between western and eastern China.For the annual mean precipitation anomalies,the first EOF mode indicates a meridional dipole pattern over eastern China,with increased(decreased)precipitation to the south of the Yangtze River and decreased(increased)precipitation to the north.The leading mode of the 850 h Pa winds and sea level pressure in summer exhibits a southwesterly(northeasterly)anomaly over South China,which is associated with a strengthened(reduced)meridional sea level pressure gradient.Compared to reconstructions,the model can capture the majority of features of climate changes in the Han Dynasty,though it underestimates the magnitude.     

MM5 Simulations of the China Regional Climate During the LGM.Ⅱ: Influence of Change of Land Area, Vegetation, and Large-scale Circulation Background

Using a regional climate model MM5 nested to an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate the relative LGM climate response to changes of land-sea distribution, vegetation, and large-scale circulation background over China.Model results show that compared with the present climate, the fluctuations of sea-land distribution in eastern Asia during the LGM result in the temperature decrease in winter and increase in summer. It has significant impact on the temperature and precipitation in the east coastal region of China. The impact on precipitation in the east coastal region of China is the most significant one, with 25%-50% decrease in the total precipitation change during the LGM. On the other hand, the changes in sea-land distribution have less influence on the climate of inland and western part of China. During the LGM, significant changes in vegetation result in temperature alternating with winter increase and summer decrease, but differences in the annual mean temperature are minor. During the LGM, the global climate, i.e., the large-scale circulation background has changed significantly. These changes have significant influences on temperature and precipitation over China. They result in considerable temperature decreases in this area, and direct the primary patterns and characteristics of temperature changes. Results display that, northeastern China has the greatest temperature decrease, and the temperature decrease in the Tibetan Plateau is larger than in the eastern part of China located at the same latitude. Moreover, the change of large-scale circulation background also controls the pattern of precipitation change. Results also show that, most of the changes in precipitation over western and northeastern parts of China are the consequences of changing large-scale circulation background, of which 50%-75% of precipitation changes over northern and eastern China are the results of changes in large-scale circulation background. Over China, the LGM climate responses to different mechanisms in order of strength from strong to weak are, the large-scale circulation pattern, sea-land distribution, vegetation, CO2 concentration, and earth orbital parameters.     

The life cycle of the intense IOP‐14 storm during CASPII. Part I: Analysis and simulations

Abstract

In this study, a 5‐day life‐cycle of the IOP‐14 storm during CASP II is examined using conventional observations and numerical simulations with a mesoscale version of the Canadian Regional Finite‐Element (RFE) model. Observational analysis reveals that the IOP‐14 storm forms from a lee trough, occurring along a strong baroclinic zone with an intense frontogenetic deformation, that interacts with an upper‐level travelling short‐wave trough across the Canadian Rockies. Then the storm experiences a slow, but nearly steady, growth while traversing the North American continent. It deepens explosively as it moves into the Atlantic Ocean. It appears that i) the enhanced large‐scale baroclinicity due to land‐sea temperature contrasts, ii) the tremendous latent heat release due to the transport of high‐θ_e air from the marine boundary layer, Hi) the decrease of surface drag and iv) the favourable westward tilt of the low with an amplifying trough all contribute to the explosive deepening of the storm.

Two consecutive simulations covering a total of 102 h during the storm development are carried out with a grid size of 50 km. The RFE model reproduces very well the formation of the surface low on the lee side of the Rockies, the track and deepening rates, the explosive development and decay of the storm, and various mesoscale phenomena (e.g., a “bent‐back” warm front, a “T‐bone” thermal pattern, a cold frontal “fracture”, an upper‐level “eye” and warm‐core structures), as verified by conventional observations, satellite imagery, flight‐level and dropsonde data from a research aircraft. It is found from potential vorticity (PV) analysis that the storm reaches its peak intensity as the upper‐level dry PV anomaly, the low‐level moist PV anomaly and surface thermal warmth are vertically superposed. PV inversions reveal that these anomalies contribute about 60%, 30% and 10%, respectively, to the 900‐hPa negative height perturbation. It is shown that the warm‐core structure near the cyclone centre is produced by advection of warmer air ahead of the cold front, rather than by adiabatic warming associated with subsidence.     

The Wave Train Characteristics of Teleconnection Caused by the Thermal Anomaly of the Underlying Surface of the Tibetan Plateau. Part Ⅰ: Data Analysis

探讨了前期青藏高原下垫面热力结构异常对后期长江中下游地区降水的影响。通过资料分析揭示出长江中下游地区夏季降水异常前期冬、春季青藏高原下垫面三维热力结构强信号特征,即长江中下游夏季旱涝前期高原南部和北部各层次的地温距平呈反位相分布。从地面0cm到地下320 cm的地温距平分布为:涝年高原偏南部(30°N以南)为正,中部和北部(30°N以北)为负,旱年时相反。其中地温距平的大值区在 40 cm到160 cm层之间。同时揭示了北半球环流型对青藏高原下垫面热力异常可能产生遥响应,并形成季尺度低频波的传播,从而影响长江中下游地区后期的降水,反映了遥相关是区域性旱涝形成的一个动力机制。资料分析结果表明前期青藏高原下垫面三维热力结构异常是后期长江中下游地区降水异常的重要原因之     

Comment on “Trends and low frequency variability of extra-tropical cyclone activity in the ensemble of twentieth century reanalysis” by Xiaolan L. Wang,Y. Feng,G. P. Compo,V. R. Swail,F. W. Zwiers,R. J. Allan,and P. D. Sardeshmukh,Climate Dynamics, 2012

The main subject of this article is to comment on the issue of storminess trends derived from the twentieth century reanalysis (20CR) and from observations in the North Atlantic region written about in Wang et al. (Clim Dyn 40(11–12):2775–2800, 2012). The statement that the 20CR estimates would be consistent with storminess derived from pressure-based proxies does not hold for the time prior to 1950.     

On the Use of the Jesuit Order Private Correspondence Records in Climate Reconstructions: A Case Study from Castille (Spain) for 1634–1648 A.D.

This work analyses the climatic information content of more than 1000 letters belonging to the private correspondence of the Jesuit order during the period 1634–1648. The information obtained mainly originates in Castille, and it was codified to obtain quantitative indices representative of the evolution of the thermal and rainfall anomalies. The results show that intense rainfall and cold air waves predominated during the study period, in accordance with other results on the climatic evolution of the Iberian Peninsula during the Little Ice Age.