Vol.27, NO.5, 2016

Display Method:
An Overview of Wintertime Snow Cover Characteristics over China and the Impact of Eurasian Snow Cover on Chinese Climate
Zhang Renhe, Zhang Ruonan, Zuo Zhiyan
2016, 27(5): 513-526. DOI: 10.11898/1001-7313.20160501
The progress on researches concerning wintertime snow cover over China is reviewed in the first part of the article. This part includes the spatial climatological distribution of snow cover and its seasonal, interannual and decadal variability, features of wintertime snowfall, effects of meteorological factors on the snow mass balance, and roles played by external forcing and atmospheric circulation system in the formation of snow cover China. Then, researches on simultaneous and lagged impacts of wintertime and springtime Eurasian snow cover upon climate over China are summarized. It illustrates climate anomalies over China are in association with Eurasian snow cover anomalies, as well as related physical mechanisms. The Eurasian snow cover anomalies can alter the soil moisture, surface air temperature and net radiation, which trigger abnormal mid-latitude atmospheric circulations over the Eurasian continent and thus affect the climate over China. By applying hindcast results of the climate forecast system version 2 (CFSv2) of National Center for Environmental Prediction (NCEP), the predictability of Eurasian snow cover and its relations with climate over China is analyzed. It demonstrates that hindcasts of CFSv2 can well reproduce the springtime interannual and decadal variability of Eurasian snow cover and associated summer rainfall anomalies in China. Although many meaningful results have been obtained on the linkage of Eurasian snow cover with the climate variability over China, some questions still remain unsolved. In the end, some issues concerning the snow cover and its climate effect are listed, which need further investigation.
Advances in the International Action and Agricultural Measurements of Adaptation to Climate Change
Zhou Guangsheng, He Qijin, Ji Yuhe
2016, 27(5): 527-533. DOI: 10.11898/1001-7313.20160502
Taking robust adaptation measures to climate warming is a consensus of the international community. Advances in international negotiation of adaptation to climate change and existing agricultural adaptation measures to climate change are reviewed. Several essential factors are analyzed, such as the serious shortages including funds, technology research and development, application and transfer, the action capacity, and the lack of systematic theoretical research and application demonstration of agricultural measurements adaptive to climate change. In order to improve measurements of agricultural adaptation to climate change and ensure the sustainable development of agriculture in China, the future research tasks of China's agriculture adaptation to climate change are put forwards, including new characteristics of agricultural meteorological disaster process and risk management, big-data based decision support system for agricultural adaptation to climate change, and division of agriculture adaptive to climate change and key technology for agricultural disaster reduction.
Advances in Techniques of Quantitative Precipitation Forecast
Bi Baogui, Dai Kan, Wang Yi, Fu Jiaolan, Cao Yong, Liu Couhua
2016, 27(5): 534-549. DOI: 10.11898/1001-7313.20160503
The quantitative precipitation forecast (QPF) is a core operation of weather forecast. Modern technological processes of the QPF include numerical weather forecast, verification and evaluation, objective calibration and integration, forecaster's subjective modification and gridding post-processing. Domestic and international research work covering these five aspects are investigated and summarized, to provide reference for development of the quantitative precipitation forecast.In the aspect of numerical weather forecast, the forecast skill of the operational global model for precipitation has been improving continuously (a gain of about 1 forecast day per decade), and developments of the high resolution model (especially the convection-permitting model) contribute to describing characteristics of the convective precipitation, while the ensemble models provide uncertainty information and the most possible outcome of the forecast. These two techniques are the main way to improve the fine level and accuracy of QPF, and improvement of short-term precipitation forecast by developing operational high-resolution model ensembles is the international tendency. Objective calibration and integration as well as gridding post-processing make up the statistical post-processing technique of the QPF, which now reach a level that applies multiple approaches of data mining to extract and integrate more useful information from massive data, and the emergence of reforecast dataset will further promote the development of statistical post-processing. In terms of verification and evaluation, to solve new problems in assessing the fine level and accuracy of the QPF, a variety of new verification approaches are developed and applied, such as the new score for verifying the precipitation forecast of different climate backgrounds, extremes and multiple types, spatial verification methods for avoiding dual punishments of traditional methods, as well as the probability verification methods for verifying the stability, sharpness, and resolution of the probability forecast. In the aspect of forecaster's subjective modification, although the value added to model and post-processing methods become more and more limited, forecasters still play a core role, gradually changing to help users make decision. The development of QPF techniques still face challenges of solving scientific problems such as the observation of atmosphere moisture and data assimilation methods, as well as heavy rain forecast in warm section and complex topography.
The Application of High Performance Computing Technology in Meteorological Field
Zhao Licheng, Shen Wenhai, Xiao Huadong, Wang Bin, Sun Jing, Wei Min, Li Juan, Shen Yu
2016, 27(5): 550-558. DOI: 10.11898/1001-7313.20160504
High performance computing (HPC), as one of fastest growing branches of information technology, solves complex computational problems via the usage of super-computer and parallel processing. The newest edition of the TOP500 list of the world's top supercomputers shows full entry into PFLOPS era. Most of them adopt cluster structure, with internal nodes interconnected by Infiniband technology. The Intel processor chip and Linux operating system occupy the dominant position. Leading HPC vendors have begun to explore ExaFlops supercomputers.Meteorology is one of the key areas on the application of HPC. Whether for short-term numerical weather forecast systems or for long-term numerical climate prediction systems, it is inseparable from the powerful computing and storage capacity support. Numerical weather prediction services have been timeliness requirement, and HPC technology overcomes efficiently restrictions of high-resolution, high-precision numerical models, and thus plays an essential supporting role. For decades, due to strong demands for HPC resources from numerical weather prediction research and operations, high performance computers and application see a rising requirement and rapid development in CMA and foreign meteorological department. Requirement for computing capabilities and system reliability is rising sharply. 22 high performance computer systems on the TOP500 list are used for the weather and climate fields. The development of meteorological numerical forecast models is characterized by higher resolution, more complicated physical processes, ensemble forecasts and model couplers. HPC capability building is especially important, as well as optimizing processor architecture, operating system, compiler and parallel environment, scientific computing library, etc. HPC resources for meteorological fields are always scarce, therefore, future management will be gradually transitioned from the current local pre-allocation way to the unified scheduling and sharing of local and remote resources. If HPC resources in the operational center of CMA headquarters and regional centers is put into unified management, monitoring, and sharing, it will solve resources integration, sharing and collaborative management, and other problems.HPC technology and weather prediction applications will be even more closely integrated, and expect innovative development in the future. In order to keep pace with numerical weather prediction research and operations, CMA will upgrade HPC capabilities and be committed to optimizing system deployment and managing computing resources to maximize efficiency.
A Review of Studies on Prefrontal Torrential Rain in South China
He Lifu, Chen Tao, Kong Qi
2016, 27(5): 559-569. DOI: 10.11898/1001-7313.20160505
The torrential rain forecast during pre-summer flood season in South China attracts a lot of research interests. The rainstorm occurring in prefrontal zone strong shows abrupt and significant regional characteristics, and it's especially difficult to solve in operational forecast, due to its inapparent synoptic scale baroclinity forcing, rich moisture content, strong environmental atmospheric thermodynamic instability, complex triggering mechanism in boundary-layer, external forcing effect of special terrain and land-sea thermal difference. For the torrential rain occurs in prefrontal district, forecasting capabilities of various global numerical weather prediction models used in China Meteorological Administration are very limited, and forecast results of high-resolution meso-scale numerical models are also disappointing. Most of results on torrential rain during pre-summer flood season in South China since the 1970s are reviewed. The unique synoptic and dynamics characteristics are systematically analyzed, such as the first proposing of the rainstorm occurs in prefrontal zone in South China and its typical synoptic scale background, the relationship between the rainstorm in prefrontal zone and the low level jet (LLJ), the formation and propagation of meso-scale convective system (MCS) produced, and triggering mechanisms of the torrential rain. Finally, according to these studies and practical experiences of China Central Meteorological Observatory, synoptic system configurations and triggering factors for torrential rain in prefrontal zone in South China are summarized as three types: The pattern of boundary layer convergence lines, the pattern of southerly wind convergence and the pattern of stronger southwest jet, and scientific problems which require further in-depth study are proposed.
The Effect Research on Ionosphere in Response to Lightning Discharge During Thunderstorm
Zhang Yijun, Zhang Yang
2016, 27(5): 570-576. DOI: 10.11898/1001-7313.20160506
Large current, strong electrostatic field and radiation field generated by lightning discharges during thunderstorm activity not only cause severe natural disaster, such as oil depot explosion, forest fire and personnel casualties on the earth surface, but also exert great effects on ionosphere which leads to the perturbation of electron intensity distribution. Lightning discharge affects ionosphere in two patterns: Direct coupling and indirect coupling. The direct coupling, which shows fast very low frequency (VLF) events in VLF reflected signal, is caused by the action of quasi-electrostatic field and electro-magnetic field generated by lightning, while the indirect coupling, which exhibits lightning induced electron precipitation (LEP) in the radiation belt, is caused by the interaction between the low frequency (LF) electromagnetic wave generated by lightning and the magnetosphere during the propagation. The amplitude of LEP is related with the current of return stroke and flash rate. The lightning discharge in thunderstorm can change the distribution of electron density from D layer to F layer, and can affect the electric field between the ionosphere and troposphere. As a result, some transient glowing, such as elves and sprite can be caused. The research of transient glowing in the middle and upper atmosphere is a hot topic. The VLF reflected signal during the electro-magnetic signal propagation of lightning discharge can be used to measure the change of ionosphere density, which is a common method to detect ionosphere disturbance. The strength of ionosphere disturbance is related with lightning discharge parameters and lightning discharge types. Many results show that positive cloud-to-ground flashes, negative cloud-to-ground with large return stroke current and discharges with large transferred charge often lead to obvious ionosphere change. Nowadays, the effect research on ionosphere in response to lightning discharge often focuses on the ionosphere bottom (often called D layer), but the observation and mechanism research of the effect on ionosphere E and F layers are still limited. As for ionosphere D, the analysis is mainly based on single point observation and simulation research, and the large scale 3-D imaging of ionosphere disturbance caused by lightning discharge needs further investigation. Effect researches on ionosphere in response to lightning discharge during thunderstorm in recent years are investigated, and the direct coupling and indirect coupling between the lightning discharge and ionosphere are introduced in detail, as well as the related phenomenon caused by the interaction between lighting discharge and ionosphere.
Recent Research Advances on the Interannual-interdecadal Variations of Drought/Flood in South China and Associated Causes
Li Weijing, Zhang Ruonan, Sun Chenghu, Ren Hongchang, Liu Jingpeng, Zuo Jinqing, Li Xiang
2016, 27(5): 577-591. DOI: 10.11898/1001-7313.20160507
Based on changes of spatial-temporal distribution of flood and drought in South China under global warming, the recent research progress on characteristics of inter-annual and inter-decadal variations of drought/flood and associated causes are reviewed. It's found there will be less precipitation in South China especially for the Yangtze valley in the developing phase of El Niño, while more precipitation in the decay phase. During the above process, the basin wide warming in tropical Indian Ocean are found to intensify the Northwestern Pacific subtropical high and shift it to a more southward position, leading to the occurrence of low-level anticyclone circulation over Northwestern Pacific, which would affect the precipitation of South China through adjusting the southerly and moisture transportation. The snow cover of the Tibet Plateau is also found as a key factor, when more snow cover occurs in spring-winter, the sensible heat flux is too weak to heat troposphere, which would reduce the meridional temperature gradient to cause a weak summer monsoon and more precipitation over the Yangtze valley, and vice versa. For synergistic effects of multi-factors on the occurrence of flood and drought in South China, results indicate it's impacted by multiple factors and cannot be dominated by one single factor. For example, the Philippine anticyclone can be impacted by the winter Tibet Plateau snow cover, El Niño and basin wide warming of tropical Indian Ocean. For the inter-decadal variation of the inter-annual relationship between flood and drought in South China and their influencing factors, strong inter-decadal variation on the relationship between the influencing factors and flood/drought are found, when these factors exhibit a strong inter-decadal variation. For example, the relationship between tropical Pacific Ocean and South China precipitation is found loose in recent decades, while the influence of Indian Ocean sea surface temperature anomaly on South China is intensified. Based on the aforementioned results, it suggests more attentions being focused on the prediction strategy and method for South China to improve the predictability of drought and flood.
A Review of Visible Infrared Imaging Radiometer on Meteorological Satellite
Yang Zhongdong, Liu Jian
2016, 27(5): 592-603. DOI: 10.11898/1001-7313.20160508
The development of visible infrared imaging radiometer that payload on environmental and meteorological satellites for 50 years are reviewed. 12 kinds of instruments are selected as typical representatives from nearly 100 sets of instruments run in orbit at different period. An analysis is done combined instrument functional performance specifications with application requirement. The analysis can be done from the basic strands of historical development, trend of main operational in the future and the direction of innovation and development. The development process can be divided into three stages. The first stage is the early exploration period. It is the first generation of remote sensing instrument on meteorological satellite that createds a precedent for earth observation. The second stage is the initial application period, it basically forms a stable preliminary application situation for three decades. At the same time, Europe and China begin to develop their own environmental meteorological optical remote sensing instruments. The third one is development and stable application stage. It appears a new generation visible infrared optical imaging radiometer. These instruments have some common characteristics, such as more than 20 spectrum channels with narrow bandwidth spectrum. The spectral range covers 0.4-15 μm and radiometricis accuracy. Their spatial resolution is between 200 and 1000 meters in general. Advanced instruments represent trends of visible infrared imaging radiometeron polar orbit meteorological satellite in the future. The visible infrared optical imaging radiometers on geostationary orbit meteorological satellite are characterized by about 15 typical spectral channels with narrow spectral bandwidth and the coverage of spectral range from 0.4 μm to 15 μm. The radiometric is also very high. The spatial resolution is between 500 and 2000 meters. The disk image forming speed can reach minute level and the regional area scanning can be faster.
Observational Study Advances of Haze and Photochemical Pollution in China
Xu Xiaobin
2016, 27(5): 604-619. DOI: 10.11898/1001-7313.20160509
In recent decades, haze pollution and photochemical pollution in China have become severe environment-meteorological disasters, causing broad and deep concern of government and public. Many research projects focusing on China's haze and photochemical pollution have been carried out by Chinese scientists in collaboration with scientists from abroad. A large number of peer-reviewed papers have been published to report results and outcomes from these projects. A review of reported results and outcomes from the study of haze and photochemical pollution in China is given. To limit the length, the paper can only include a concise review of the literature published mainly in the last decade and summarize the outcomes from observations, observation-based analyses, with impact and damage studies. Studies of haze pollution are reviewed, with foci on the haze phenomenon and haze-fog differentiation, the major compositions of haze particles and their sources, meteorological factors influencing haze formation, long-term trends of haze and potential causes. Advances in the study of photochemical pollution are summarized, in terms of characteristics and extent of photochemical pollution, the regional extension of photochemical pollution, the vertical distribution of ozone, factors influencing surface ozone, long-term trends of surface and tropospheric ozone. In addition, it introduces impacts of haze and ozone pollution on human health, impacts of haze on the safety of traffic and electricity transfer, and impacts of ozone pollution on crops, vegetables and natural vegetion. Methods to differentiate haze from fog or mist have been questioned for a long time. The major issue has been the upper limit of relative humidity (RH) for haze, which have influenced the data quality of historical haze and fog records. Recent studies suggest that the RH upper limits for haze (80%) and haze-fog mixture (95%), which are given in the current meteorological standard, should be lowered. Including PM2.5 data may facilitate the haze-fog differentiation. However, more studies are necessary in different regions. Although impacted by mineral dust, the major compositions of PM2.5 are from anthropogenic sources, including organic compounds, sulfate, nitrate, ammonium, etc. Secondary aerosols dominate the formation severe haze. There have been long-term increases in haze days over many regions of China. These trends can more or less be attributed to factors related with climate change, such as lower windspeed, lower RH, lower boundary layer height, etc., but should mainly be caused by increased emissions of air pollutants. After the discovery of photochemical smog in Lanzhou, western China, high levels of surface ozone have been often observed in other cities, particularly those in the North China Plain (NCP), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions. In recent decades, even higher ozone levels have been observed at rural and regional background sites in the above regions, indicating that photochemical pollution in China has become a regional or super-regional phenomenon. Only a few sites in China have been collecting long-term data of surface ozone and ozone profiles are observed only at one site for a longer time. Limited datasets show that levels of ozone in the NCP and PRD regions have been signifcantly increasing, and there has also been an increase trend in surface ozone at Mt Waliguan, a baseline station in western China. Ozone formation at most urban and rural sites in the NCP, YRD and PRD has been found to be more sensitive to VOCs, species that have been increasingly emitted. It implies that photochemical pollution would become even more severe in the above regions and take a long time to control. In future studies, more attention should be paid to photochemical pollution, to interactions between haze and photochemical pollution, and to coupling among pollutants, meteorology, chemistry and ecosystem.
Research Progress on Agricultural Meteorological Disaster Monitoring and Forecasting
Guo Jianping
2016, 27(5): 620-630. DOI: 10.11898/1001-7313.20160510
Agricultural meteorological disaster is one of the main natural disasters affecting crop yield stability in the world. Impacted by monsoon climate, China is one of the most seriously affected countries by agricultural meteorological disaster in the world. China's great disaster variety, high strength, high frequency, wide influence range, and severe yield losses have great impacts on sustainable development of agricultural production. Agricultural meteorological disaster monitoring and forecasting is the basis and premise of disaster assessment and prevention. Accurate monitoring and timely forecast of disasters is possible for effective prevention of agricultural meteorological disasters, and makes yield losses decrease to a minimum extent. Therefore, corresponding research has long been a key fields of agrometeorological research.Based on a systematic review on the research progress and achievements of agricultural meteorological disaster monitoring and prediction technology, some problems are found to be quite vital: The fundamental research of agricultural meteorological disaster is still insufficient, commonly-used agricultural meteorological disaster index doesn't fully consider hazard-formative factors, agricultural meteorological disaster monitoring isn't fine enough, early warning technology is short, and the new pattern of agricultural disaster under climate change are not revealed enough. Therefore, some efforts should be strengthened in the future, i.e., a more comprehensive disaster index, advanced forecasting technology, real-time warning system, three-dimensional and dynamic monitoring system, the evaluation of disaster risk under climate change, and the application technology of meteorological and climate forecast information in the prediction of agricultural meteorological disasters.
Progress on Mechanism and Prediction Methods for Persistent Extreme Precipitation in the Yangtze-Huai River Valley
Zhai Panmao, Li Lei, Zhou Baiquan, Chen Yang
2016, 27(5): 631-640. DOI: 10.11898/1001-7313.20160511
Persistent extreme precipitation (PEP) results in severe floods in China, especially in the Yangtze-Huai River Valley (YHRV), making it one of the main weather disasters in China. There exists an urgent need to enhance understandings on the formation mechanism and developing rules of PEP and extend forecast valid time of the PEP for the scientific decision of government.In recent years, progress has been achieved from related studies on the formation mechanism and forecast method of PEP in the YHRV which has caught wide attention. The method of automatically identifying regional PEP events is established which is named as RePEEI (Regional Persistent Extreme Event Identifier). Conceptual model is established on the large-scale circulation patterns responsible for PEP events, revealing that concurrent anomalies of the key influential systems are important causes for the occurrence and maintenance of PEP, and precursor signals (about 1-2 weeks prior to the onset of PEP) are investigated. Taking East Asia/Pacific teleconnection pattern (EAP) as a point of penetration, the mechanism of its effects on PEP is explored. Moreover, it indicates that whether the PEP will occur in YHRV is decided by the north-south location of high systems at low latitudes. Schematics for precursor circulation features of typical EAP patterns responsible for persistent extreme precipitation events in the YHRV is established. And corresponding precursor signals are also obtained, the feasibility of predicting PEP on the use of EAP is discussed. Furthermore, based on the key influential systems and precursor signals found above in characteristic large-scale circulation patterns, the physical statistical forecast model for the prediction of PEP is established, which is named as KISAM (Key Influential Systems based Analog Model), with the idea of parameter optimization method and ensemble mean introduced, using different predictors and cosine angular analog method with weight assigned.However, the forecast of PEP is still a challenge, especially when the forecast lead time extends to medium range or even extended range. The performance of numerical models in predicting the occurrence and location of PEP still leaves much to be solved. How to further improve direct outputs of numerical models and combine model outputs with physical statistical methods to improve the forecast of PEP is a research area that needs much more study.