应用气象学报

2016, 27(6)

[FullText](3754) [PDF 1097KB](354)

Abstract:

Research and Application of Operational MJO Monitoring and Prediction Products in Beijing Climate Center

Wu Jie, Ren Hongli, Zhao Chongbo, Zhang Peiqun, Wu Yujie

2016, 27(6): 641-653. DOI: 10.11898/1001-7313.20160601

[FullText HTML] (1113) [PDF 3851KB](586)

Abstract:
Both Madden-Julian oscillation (MJO) and the boreal summer intra-seasonal oscillation (BSISO) have great impacts on the global weather and climate events, which are the most important predictability source of sub-seasonal to seasonal (S2S) prediction. However, the monitoring of MJO/BSISO in China National Climate Center/Beijing Climate Center (NCC/BCC) entirely depends on external data, and the prediction skill of the introduced statistical forecast model is also much lower than dynamic mode, and the practical real-time operation ability has not been established. Therefore, based on CMA (China Meteorological Administration) global analysis data of T639 model, OLR (outgoing long-wave radiation) data of FY-3B satellite and the real-time forecast data of BCC atmospheric general circulation model system (BCC_AGCM2.2), applying the real-time multivariate MJO (RMM) index and BSISO index, BCC develops the MJO real-time monitoring and forecast technology, and establishes the trial ISV (intra-seasonal variability)/MJO prediction system (IMPRESS1.0).In comparison, monitoring results based on T639 wind analysis and FY-3B OLR data is generally consistent with the operational products from other centers, suggesting the capability of characterizing the oscillation and evolution of MJO/BSISO index accurately. Case study for the typical strong MJO event in March 2015 indicates that the amplitude peak of RMM index based on T639 and FY-3B OLR data is weaker than monitoring results based on NCEP and NOAA OLR data. Further analysis for three variables U850 (zonal wind at 850 hPa), U200 (zonal wind at 200 hPa) and OLR show that the convection monitored by FY-3B satellite is more consistent with NOAA's result, while the projection amplitude of the U850 based on T639 analysis against MJO mode is slightly weaker than NCEP/NCAR reanalysis data, which leads to weaker RMM index amplitude. The forecast skill verification shows the IMPRESS1.0 is able to provide correct evolution and intensity information of MJO at least 16 days in advance, and the skill of operational forecast in 2015 reach 18 days. The rolling prediction skill could be improved continually as the evolution of MJO event, and the predicted RMM index phase space track is closer to reality. Meanwhile, the verification of hindcasts by using correlation skill (COR), root mean square error (RMSE) and mean square skill score (MSSS) shows that the IMPRESS1.0 has useful prediction skill for about 12 days for MJO index and 8 days for BSISO1 and BSISO2 index, respectively. The case study for BSISO event in July 2015 also shows prediction skill, the reconstructed anomaly circulation and convection against BSISO index clearly demonstrate the dominant mode and northward propagation of BSISO. Therefore, the unified monitoring and forecast productions based on IMPRESS1.0 can provide important references for extended-range prediction, and offer certain help for operation and research.

Model Assessment of Dynamical Atmospheric Pollution Control Schemes Based on Sensitive Source Zone Analysis

Xu Jing, Zhang Xiaoling, Cai Xuhui, Zhao Xiujuan, Su Jie, Zhang Ziyin, Wen Wei

2016, 27(6): 654-665. DOI: 10.11898/1001-7313.20160602

[FullText HTML] (1072) [PDF 6174KB](326)

Abstract:
In recent years, the atmospheric environment in parts of China has become significantly degraded and the need for emission controlling has become urgent. As more international events have been carried out, and more serious pollution weather happens frequently, it is important to implement air quality assurance targeted at significant events held during specific periods. A representative pollution episode, 6 November to 11 November in 2014 is chosen and simulations are carried out setting urban area of Beijing as the target region. By using the method of footprint analysis, the sensitive source zones that have the greatest impact on the air quality of the Beijing urban area are determined. Regional chemical and transportation model WRF-Chem is used to establish emission reduction tests for the focus source zones and for specific sensitive source zones within and around Beijing. Results show that two kinds of tests have significant effects on PM_2.5 concentration decreasing in the emission reduction local with high intensity of emission source. Besides, the effect could also result in the decrease of pollutant concentration in downwind area under the transportation function. But only in terms of the target area, initiating a moderate emission reduction for specific sensitive source zones is more effective on the air quality of urban Beijing than initiating the same strength emission reduction for focus source zones. In certain cases when the PM_2.5 direct emission reduction for the specific sensitive source zones accounts for less than 20% of focus source zones, the PM_2.5 concentration reduction amount in Beijing urban area can reach the level when the sensitive source zones reduction scheme accounts for about 60%-90% of focus source zones. This ratio maintains stable through all pollution process. Thus the daily dynamical emission reduction measures developed based on the sensitive source zones analysis, can help cut the emission control costs and improve the emission reduction efficiency. In addition, results from different study cases in different pollution degree further prove the above conclusions, indicating the reliable applicability of the dynamical emission reduction scheme in the guidance of emission reduction measures. Therefore, when enacting emission reduction schemes, cooperating with surrounding provinces and cities, as well as narrowing the reduction scope to specific sensitive source zones prior to unfavorable meteorological conditions, can help reduce emission control costs and improve the efficiency and maneuverability of emission reduction schemes.

Application of the Correction Algorithm to Mass Conservation in GRAPES_GFS

Su Yong, Shen Xueshun, Zhang Qian

2016, 27(6): 666-675. DOI: 10.11898/1001-7313.20160603

[FullText HTML] (1086) [PDF 5847KB](269)

Abstract:
The conservation of mass is very important for the dynamic core of numerical model, especially for climate simulation or medium and long term prediction. For the traditional semi-Lagrangian dynamic core, it is difficult to satisfy the mass conservation theoretically, the finite volume method can be used in the semi-Lagrangian continuous equation to satisfy the mass conservation in theory, but the practical application is more complex, and no operational center adopt the method at this time. On the other hand, the traditional semi-Lagrangian method combined with a simple and easy mass correction algorithm is also a good choice.The GRAPES_GFS (Global-Regional Assimilation and PrEdiction System, Global Forecast System) of Numerical Prediction Center of CMA (China Meteorological Administration) faces a problem that the mass loss is obviously in the process of long term integration. The global mean sea level pressure drops about 1 hPa in 10-day run, due to the choice of the continuity equation and the calculation accuracy of the dynamical core. In the early times of development, there is a very simple mass correction algorithm in GRAPES_GFS, however, in the process of batch testing of the system in 2013, it is found that this algorithm will lead to the increase of the height bias at the top level of the model, so the algorithm is closed.Ideas of C-CAM (Climate-Community Atmosphere Model) model are drawn on, to achieve mass conservation through the correction of surface pressure. A method is developed adjusting mass in each grid box according to different weight coefficient, with the basic idea of modifying more in the grid boxes which have larger changes in mass while less in those with smaller changes. The feasibility of this method is verified by a series of experiments, including ideal test, real case prediction and a batch of cycle prediction, illustrating that the method can effectively reduce the bias of height field under the premise of ensuring the mass conservation, and alleviate the problem of underestimating weather systems. It shows that this method has a certain application value in actual operational forecast, and be further studied in calculating the weight coefficient of each point. It can reduce the bias of the height field at the top level of the model, as well as the high latitude in the Southern Hemisphere.

Comparative Analysis on Precipitation Forecasting Capabilities of Two Ensemble Prediction Systems Around Qinling Area

Pan Liujie, Xue Chunfang, Zhang Hongfang, Chen Xiaoting, Wang Jianpeng

2016, 27(6): 676-687. DOI: 10.11898/1001-7313.20160604

[FullText HTML] (1067) [PDF 2839KB](519)

Abstract:
Using precipitation forecast data of ECMWF and NCEP ensemble prediction systems, hourly rainfall data fusion by CMORPH (NOAA Climate Prediction Center Morphing Method) satellites and 30000 automatic weather stations, the precipitation and precipitation probability forecasting capability of ECMWF and NCEP ensemble prediction systems around Qinling area are comparatively analyzed from June to October in 2013 and 2014, mainly based on classic skill score and ROC (relative operating characteristic) statistical method. Results show that the precipitation spatial distribution pattern can be better described by both ECMWF and NCEP ensemble prediction systems with the disadvantages that forecasted high value center is larger and the precipitation amplitude is small; the correlation coefficient of ECMWF control forecast and perturb forecast with observations is higher, the standard deviation ratio is close to 1.0 in previous 10 days, which is better than NCEP, but NCEP forecast skill score has better performance than ECMWF in 264-360 hours.The ensemble mean skill score for heavy rain of ECMWF ensemble prediction system is better than NCEP in 0-120 hours. The forecast skill score of ensemble mean is lower than control forecast and perturb forecast for both two systems. Ensemble mean significantly reduces the standard deviation of precipitation amplitude and this is not conducive to the accuracy of synoptic scale precipitation prediction. Ensemble mean significantly increases forecast bias of light rain and increases the false rate, while the forecast bias of heavy rain and the fail rate decrease. This phenomenon is more remarkable when ensemble mean contains more perturb members and forecast skill is roughly the same between different members, and this makes ECMWF ensemble mean skill scores for light rain lower than NCEP.Overall, ECMWF probability forecast effect is better than NCEP. When precipitation threshold increases, BS score of both two models increases sharply while the forecast capacity significantly reduces, for storms, the ROC area is smaller than climate probability sometimes. The ROC analysis show that as the forecast probability improves, ECMWF ensemble prediction system slightly decreases the hit rate and significantly reduces the false rate, however, NCEP have a high false rate and higher hit rate. So depending on user's requirements, different model can be chosen as reference.

Application of Lagrange Water Vapor Source Diagnosis Method to the Three-river Source Area

Quan Chen, Chen Bin, Zhao Tianliang, Zhou Bingrong, Han Yongxiang

2016, 27(6): 688-697. DOI: 10.11898/1001-7313.20160605

[FullText HTML] (1186) [PDF 7318KB](323)

Abstract:
The Three-river Source (TRS) region locating at the Tibet Plateau hinterland, contains a huge resources, gives birth to several world famous rivers, and supplies fresh water resources for East Asia. Identification of the regional moisture source is of great significance for understanding of regional water budget and improving the ability of water resources management. Ensemble modeling method is used with the three-dimensional Lagrangian transport model FLEXPART (Flexible Particle Model), driven by the GFS (Global Forecast System) reanalysis data (four times one day) from NCEP/NCAR. Then, the water vapor transport and source identification technology is used to identify the main moisture source for TRS region, with consideration of the spesific humidity changes along their transport pathways. The result indicates that a large number of air parcels experience several surface-atmosphere water vapor cycle process before reaching the TRS region. Dominated by the moisture transport form the prevailing westerlies and the central Asia strong evaporation, moisture sources characterized by relative short time transport (less than 6 days) mainly come from the Tibetan Plateau and its northwest edge, while the moisture sources with longer time (8-10 days) can be traced backward to the Arabian Sea, the Bay of Bengal, and so on. The water vapor reaching the TRS region transport can roughly be categorized to two pathways: The first is along the Somali to the Arabian Sea water vapor transport across the equator, and the second is the west path controlled by the west wind, transport from central Asia and west Asia to TRS region. Quantitative analysis shows that the moisture source also exhibits obvious sub-seasonal variability during the summer, characterized by the leading source area located in the west side of TRS region in June, and the Arabian Sea in July. However, the contribution from the Arabian Sea decreases and the contribution from the Bay of Bengal increases in August. Throughout the summer, the North of the Plateau maintains a stable water vapor transport.

An Improvement of Brightness Temperature Simulation of FY-3 IRAS Infrared Water Vapor Channel

Cao Yueyao, Zhang Peng, Ma Gang, Bai Wenguang, Liao Mi

2016, 27(6): 698-708. DOI: 10.11898/1001-7313.20160606

[FullText HTML] (1107) [PDF 3146KB](372)

Abstract:
Forward modeling of satellite atmospheric sounding instruments is the foundation of satellite data assimilation and inversion. Currently, more uncertainties on the accuracy of infrared water vapor channel are still exist compared with temperature detection channel. A method based on the group training of profiles which are classified by their water content of air column is used, to try to improve the forward modeling accuracy in the water vapor channel. Determination of threshold value is based on principles of basic balance profile numbers after group classification. Many threshold values are utilized to classify profiles, only results of threshold for 0.045 kg·m^-2 are detailed and analyzed, which lead to quite similar experiment results. TIGR 43 profile library is used as the training sample to get coefficients for fast radiative transfer computation and NESDIS 35 profile library is used to test the precision improvement as the independent sample.Different coefficients got from the group training are used to establish RTTOV forward model of FY-3 IRAS and the channel brightness temperature is calculated using the corresponding profile and coefficients. The forward modeling accuracy of the FY-3 IRAS brightness temperature is get by comparison with line-by-line results, which are considered as accurate and reliable. Research results show accuracy improvement of the brightness temperature after group training. Improvement shows better in the low water content profile case, which up to 0.17 K in the 0.045 kg·m^-2 threshold experiment. Further analysis is executed to find the cause for the improvement in the group training experiment. The layer water vapor predictor optical depth of channel 11-13 are calculated and comparison is done between the forward model with and without group training. Results show better consistency of water vapor absorption and channel weighting function distribution, besides, the absorption of water vapor line and continuum is adjusted more reasonable considering the weighting function height. These provide positive influence on the improvement of forward modeling results.It puts forward a method which can improve the fast radiative calculation accuracy of infrared water vapor channel, further work should be done in respect of bias caused by the precision of water vapor molecule absorption line parameters and the input water vapor profile self error. Furthermore, it merely considers the water content of air column, the potential influence caused by the shape of the profile is out of consideration, which may be the cause for the negative effect in channel 13 and research direction of future work.

In-orbit Performance Analysis on Monitoring Typhoon with FY-3B/MWHS

He Jieying, Zhang Shengwei

2016, 27(6): 709-715. DOI: 10.11898/1001-7313.20160607

[FullText HTML] (1075) [PDF 1636KB](390)

Abstract:
Fengyun 3B meteorological satellite (FY-3B) is the second generation polar-orbiting meteorological satellite, which is launched on 5 Nov 2010. Microwave humidity sounder (MWHS) is one important sensor onboard FY-3B and begins to work since 11 Nov 2011. MWHS is a five-channel total power microwave radiometer, which has 3 channels operating at 183 GHz and two dual-polarized channels working at 150 GHz (window frequencies).For channels of 150 GHz and 183.31 GHz, the angle resolution is 1.1°, making the resolution 15 km at nadir pixel. One motor drives two separated reflectors for 5 channels, and the scanning period is 2.667 s. Main beams of the antenna scan over the observing swath (±53.35° from nadir, 2600 km) at a constant periodicity of 1.71 s. During each period, two-point calibration is performed to calibrate the receiver gain and noise.A quantitative evaluation on the stability of the MWHS post-launch performance is carried out, which indicates the MWHS onboard FY-3B is improved comparing with that on FY-3A. Case assessment shows the MWHS can provide typhoon information, including the procedure of generating, developing and weakening as well as the rainfall caused by typhoon. During typhoon Linfa, Chan-hom and Nangka in 2015, high quality data are achieved, and the typhoon eye areas are clearly monitored with the aid of FY-3B MWHS.For precipitation, the scattering at frequencies around 150 GHz (dual-polarized) and 183 GHz result in significant brightness temperature depressions. According to the distributions of brightness temperature differences of channel 1 minus channel 5, channel 1 minus channel 2, and channel 3 minus channel 5, the precipitation and rain detection can be derived using neural network method. These quantitative assessment may provide reference for application of MWHS observations.

Characteristics and Simulation of Artificially Triggered Lightning Precursor Current Pulse

Qian Yong, Zhang Yang, Zhang Yijun, Chen Lüwen, Lü Weitao, Zheng Dong, Chen Shaodong, Yan Xu, Xu Liangtao

2016, 27(6): 716-724. DOI: 10.11898/1001-7313.20160608

[FullText HTML] (1601) [PDF 1077KB](602)

Abstract:
During summers from 2010 to 2014, two kinds of rocket are used for artificially triggered lightning experiments in Guangzhou Field Experiment Site for Lightning Research and Testing. Based on the analysis upon current data of 25 classical rocket-and-wire triggered lightings, it can be confirmed that the unipolar precursor pulse is generated from the lightning triggered by copper wire, while the unipolar precursor pulse is generated from the lightning triggered by steel wire. As for the unipolar precursor pulse, the geometric mean (GM) values of peak current, rise time, duration of waveform and charge transfer are 26 A, 0.33 μs, 2.3 μs and 27 μC, respectively. While for the bipolar precursor pulse, the corresponding values are 67 A, 0.24 μs, 2.1 μs and 54 μC, respectively. The GM value of peak current for bipolar precursor pulse is close to 2.6 times that of the unipolar precursor pulse, however, GM values of duration and rise time are similar. Furthermore, the channel base current waveforms generated from copper and steel line are simulated by using the transmission line model. The simulated waveform is consistent with the observed one. The channel base current waveforms exhibit a bipolar oscillation, which can be caused by the obviously small characteristic impedance for copper wire than the grounding block. It is confirmed that the two forms of current waveform are caused by the difference between characteristics impedance of transmission line and grounding system. Precursor pulses are known that can be attributed to the superposition between the channel top current pulses and the bottom reflected current pulses. The current flows into the grounding system. If the characteristic impedance of transmission line doesn't match with the characteristic impedance of grounding system, the current will reflect at the connecting point between the transmission line and grounding system. With larger difference between the characteristic impedance of transmission line and grounding system, the reflection is more obvious. As a contrast, the characteristic impedance of steel wire is close to that of grounding system, which leads to weak reflection. Therefore, the current at the channel bottom generated from triggered lightning with steel wire is the same as the top current. The current pulses generated by the upward leader initial discharge at the top of the transmission line are unipolar. The conclusion is also verified by simulation results.

Lightning Channel Image Recognition Based on Line Support Region

Li Feng, Lü Weitao, Li Qingyong, Zhang Ge, Ma Ying, Yang Jun

2016, 27(6): 725-733. DOI: 10.11898/1001-7313.20160609

[FullText HTML] (1043) [PDF 1528KB](257)

Abstract:
Lightning channel coordinates in digital images are often manually extracted to analyze the development and morphology of lightning channels, but this method is not efficient and its result is often subjective. Therefore, more and more researchers start to investigate approaches to recognize lightning channel information automatically. In general, lightning channel images are complex and diverse because of low contrast, occlusion of clouds, and interference of other environmental factors, so most traditional lightning channel segmentation algorithms do not work well for such lightning images.A new lightning channel segmentation algorithm named LLSR is brought forward based on line support regions. First, Gauss matched filtering and contrast stretching method are applied to enhance the contrast of lightning channels, according to the gray distribution characteristics of cross section of lightning channels. Second, line support regions, which include lightning channels within a minimum enclosing rectangle, are extracted as foreground area by a line segment detection method. In addition, line support regions are expanded in both the main direction and its perpendicular direction. In general, a line support region contains a segment of a lightning channel. Furthermore, it has better contrast between lightning channel and background. Finally, Otsu thresholding method is applied in each line support region to extract lightning channels, because the gray level distribution of each line support region is bimodal. Therefore, lightning channels are segmented from complicated background.A dataset including various types of lightning channel images, are constructed and manually marked to evaluate the proposed algorithm LLSR. Compared with traditional algorithms, global thresholding method (GThres), local thresholding method (LThres), and Canny thresholding method (CThres), the proposed LLSR has higher precision for lightning channel segmentation, and it obtains a better balance between recall rate and false positive rate. Besides, experiment results show that traditional algorithms are not robust enough for all types of lightning images, but the new method demonstrates better generality. LLSR can recognize not only the lightning channels with low contrast but also the lightning channels with complicated background, and the segmentation result is visually consistent with human eyes.

Characteristics of Raindrop Falling Process at the Mount Huang

Yuan Ye, Zhu Shichao, Li Aihua

2016, 27(6): 734-740. DOI: 10.11898/1001-7313.20160610

[FullText HTML] (1068) [PDF 477KB](436)

Abstract:
Utilizing raindrop spectrum data recorded by PARSIVEL of April-Octomber from 2011 to 2012 at the top and foot of the Mount Huang, 17 precipitation cases are collected, which divided into convective cloud precipitation and stratiform cloud precipitation. Characteristics of raindrop spectrum in different height and cloud from 17 precipitation cases are analyzed.Observed results show that the average concentration of raindrops at the top of the mountain is higher than that at the foot of the mountain in both convective cloud and stratiform cloud precipitation, the average peak diameter and the average mass median diameter both increase during falling process, but average intensity and radar reflectivity both have a smaller change. Neither convective cloud nor stratiform cloud raindrop spectrum distribution broadens from top to foot of the Mount Huang, but the spectrum shapes of raindrop change from M-P (Marshall-Palmer) to Gamma. Raindrop loses at most bins when falling from top to foot of the mountain, the maximum loss appears at the third bin of raindrop spectrum, with the loss percentage exceeding 50%. The concentration of bigger raindrop of stratiform cloud begins at the 11th bin (with feature diameter of 1.375 mm) and convective cloud raindrop begin at the 13th bin (with feature diameter of 1.875 mm) increase during falling process. The increase amplitude is lower than 10% except the 12th bin (with features diameter of 1.625 mm) and the 13th bin of stratiform cloud raindrop, and the increase at these two bins are 10.8% and 11.9%, respectively. Evaporation accompanies with the whole falling process, which has bigger effects on small raindrops than big ones, leading to lower concentration of smaller raindrop at the foot of the mountain. These losses gradually reduce along with raindrop diameter increasing due to effects of coagulation process of raindrop become stronger along with raindrop diameter increasing. Therefore, these changes occurring during falling process may be caused by both evaporation and coagulation process of raindrop.

Auto-analysis of Trough System at 500 hPa Based on Gradient Algorithm

Yan Changjian, Hu Wendong, Zhang Chunmei, Wang Shigong, Yang Youlin, Ren Hao, Lü Changwei

2016, 27(6): 741-749. DOI: 10.11898/1001-7313.20160611

[FullText HTML] (1089) [PDF 2049KB](561)

Abstract:
As the forecast products are increasing rapidly and the efficiency of manual process remains pretty low at present, the demand for intelligent assistant computer system of weather forecast is very urgent. It is the fundamental way to improve the automatic level of operational forecast in order to release the working pressure for detail forecast. The study on auto-analysis technology of weather systems is conducted as it is the key to build an intelligent forecast computer software with the thinking way of human kind. Based on synoptic notion and graphic features of trough system, under the guidance of computer graphics theory, trough system at 500 hPa are analyzed.The mathematic relations between gradient of geopotential height, its perpendicular direction and the nodes of trough system are proven by analysis of trough system conception, synoptic and graphics characteristics. The algorithm of trough system auto-analysis is developed under the strict constrain of atmospheric dynamic theory taking gradient of geopotential height as key element, and searching the relative minimal in its perpendicular direction within an optimal neighborhood which is determined by contrastive analysis. A set of software is developed using the geopotential height field of European Centre for Medium-Range Weather Forecasts at 500 hPa in format 4 of MICAPS which is the operational standard of China Meteorological Administration to meet the need of forecast centers at all levels of the country. The technical problems such as gradient calculating, direction zoning, neighborhood designating, primary nodes selecting, noise filtering, cluster analyzing are solved. Some fake troughs and over flow points can be identified with positioning according to the synoptic principals and basic experience, while the indices of density and location of primary nodes are applied to eliminate different noises, which concentrated in some certain areas. The multiple trough lines are merged by clustering and axial direction averaging. The auto-analysis technology and process of both westerly trough and traverse trough lines are developed and products are output in format 14 of MICAPS for forecasters. The algorithm and corresponding software system of auto-analysis of troughs is evaluated with parameters such as offset, length and general inclination angle. Recent experiments on cold wave samples in Ningxia show that the algorithm and the relevant software are stable, the effect in general is satisfying, and the method shows a better performance, especially in areas of middle and high latitudes. Through trail run, the efficiency of trough auto-analysis is improved further, and shortages of contour pursuing method are eliminated.

Impacts of Global Climate Change on China's Climate Security

Wang Yujie, Zhou Botao, Ren yuyu, Sun Chenghu

2016, 27(6): 750-758. DOI: 10.11898/1001-7313.20160612

[FullText HTML] (1821) [PDF 726KB](500)

Abstract:
Global warming hiatus phenomenon has been a hot topic of climate research and public concern in recent years. To analyze the climate change during different periods and the trend of extreme climate events, monthly mean land-surface air temperature, daily land-surface air maximum temperature, daily precipitation and mean maximum wind speed of tropical cyclones landed in China are examined. Results reveal that taking the years of 1961-1990 as reference period, the global decade mean land-surface air temperature anomalies are-0.052℃ for 1961-1970, -0.066℃ for 1971-1980, 0.116℃ for 1981-1990, 0.274℃ for 1991-2000, 0.49℃ for 2001-2010 and 0.541℃ for 2011-2015, in which obvious increasing trend can be easily found. And the years of 2011-2015 are the warmest five years for global and Asia since mid-to-late 19th Century. Under the background of climate change, the average high temperature days and heavy rain days increase by 28.4% and 8.2% in China over the last 55 years. Frequencies of extreme climate events increases obviously, leading to increasing climate risks and significant changes of climate capacity. In order to ensure the climate safety, strategies are list as follows: Strengthening the scientific research, and improving the understanding of public and decision maker on climate change, climate safety and climate risk; according to the national and local conditions, taking appropriate adaptation actions, strengthening disaster risk management, to reduce the adverse effects that have occurred and will occur; taking measures to control greenhouse gas emissions against long-term climate risk.At present, the research on climate risk of our country needs more attention, and the public's climate security awareness still needs strengthening. Participating in the Global Framework of Climate Service (GFCS) and Future Earth (FE) operations should be made a priority to improve the scientific understanding and strengthen disaster risk management. More steps should be taken to actively adapt climate change, accelerate the adjustment of economic structure focused on green-low-carbon, and finally effectively reduce climate risks and ensure climate safety.

Vol.27, NO.6, 2016