Current Issue

 

• Review of Advances in World Arid Climate Research (Ⅰ):Development and Contribution of Some Main Dryland Countries and the UN
• QIAN Zheng'an;SONG Minhong;WU Tongwen;CAI Ying
• 2017 Vol. 36 (6): 1433-1456.  DOI:10.7522/j.issn.1000-0534.2017.00075
• Abstract ( ) HTML PDF (1393KB) ( )
• To review the development status and advances in world dryland climate investigation in the past 70 years, first of all, the companion paper (Ⅰ) introduces the development status and contribution of some main dryland countries and the UN. The main points are as follows:(1) In the 20^th century, there were two major drought events occurring:one was "the dust bowl drought of 1930", US. Another one was southern Sahel long term one from 1968-1999. (2) The US is the strongest county in the dryland climate research in past century. Its dry climate studies begin earlier, act the leading role almost in the each branch field of its, especially in putting award and using of drought indices and the causes of the arid climate forming. (3) As a developing country, China dry climate research begin something late, but some encouraging pregresses in China-Mongolia dry climate have been already made since 1980 then, say the summer water vapor transform in the center area of Northwest China dar climate, the spring dust storm in China-Mongolia zone and the dryland climate forming. (4) And also Australia, British, Japan and the UN have an important contribution to world dryland climate investigation and combating global warming.

• Review of Advances in World Dryland Climate Research (Ⅱ):Main Investigation Progress
• QIAN Zheng'an;SONG Minhong;WU Tongwen;CAI Ying
• 2017 Vol. 36 (6): 1457-1476.  DOI:10.7522/j.issn.1000-0534.2017.00076
• Abstract ( ) HTML PDF (6102KB) ( )
• As the continued paper of the review (Ⅰ), the paper (Ⅱ) will further review the main progresses in world dryland climate, including drought indices, arid-and semiarid-zone dividing and their distribution, dryland climate changes, forming causes and projecting. The main points are as follows:(1) More than dozens availability drought "indices" have already put out in various countries, they are well-used in home and abroad. Say, the PDSI, SPI and NDVI indices and so on in the US. (2) Nowdays more researchers utilize the "moisture availability as the "criteria" in dividing the dry areas. Among nearly 10 existed arid-and semiarid-zone maps have been published, the map of Hulme and Marsh is more closer to the real world. On the average, the arid-and semiarid-area make totally up 35% of the global land area, they cover the 8 major arid areas:ie, the North Africa, Australia and China-Mongolia ones and so on; there are the home of about 20 billion people of the globe. (3) The global climate changes in past 1 000 (especially in the recent 100) years are mainly characterized by global warming of the surface air temperature and the larger temporal-and spatial-changes of precipitation climate. Due to the increased CO₂ and CH₄ greenhouse gasses, the global mean temperature increased 0.56~0.92℃ in the past 100 years. In contrast, beyond the East Asia and North Africa, the precipitation climate change links among other dry zones are not so close to each other. There are two combination partterns for temperature and precipitation change in various dry zone in the past. (4) There are many ways for the drought causes across the world arid zones. From the recent discussions about North Africa and China-Mongolia drought causes, it is seemely that the global arid climate forming may classified briefly in two types only:namely global tropical warm SST and mountain topography impact ones. North Africa and China-Mongolia arid areas are the respectively representation of the two types. The discussions show:for the former, it is caused by mainly the global warm SST, especially in the tropical zone and secondly by the land-air interaction; for the latter, by mainly the Qinghai-Xizang Plateau topography and secondly by the circulation. (5) The key point of the arid climate prediction is the one of the decodal drought. There are long road to go for the arid climate prediction.

• Climatic Characteristics of Rainfall Change over the Qinghai-Tibetan Plateau from 1980 to 2013
• HAN Yizhe;MA Weiqiang;WANG Bingyun;MA Yaoming;TIAN Rongxiang
• 2017 Vol. 36 (6): 1477-1486.  DOI:10.7522/j.issn.1000-0534.2016.00125
• Abstract ( ) HTML PDF (4570KB) ( )
• Precipitation is an important factor in reflecting climatic characteristics. In this paper, Chinese ground climate data was used, 20 sites which represent the Qinghai-Tibetan Plateau area were selected and their precipitation days and precipitation data were recorded for analysis. Mann-Kendall test analysis method (MK-test) and wavelet analysis was used to analyze temporal and spatial features and evolution of precipitation days and precipitation on the Qinghai-Tibetan Plateau. The result shows that from 1980 to 2013, there was an opposite trend between the average annual precipitation changes in Qinghai-Tibetan Plateau and the precipitation days. While the average annual rainfall increased, the average annual precipitation days decrease at the same time. Wavelet analysis by the regional annual average precipitation days of the Qinghai-Tibetan Plateau revealed that the number of precipitation days from 1980 to 2013 exist fluctuation cycle changes of 8 years. From the wavelet analysis of the Qinghai-Tibetan Plateau we can see that 5 years and 11 years is the period of fluctuation in the average annual precipitation average annual rainfall wavelet. At the same time it can be found that precipitation increase from northwest to southeast and the days of precipitation and precipitation gradually increase, too. This regional distribution shows a same trend. The average annual precipitation days in Tibet is larger while compared to Qinghai, and the average annual rainfall is also greater than the average annual rainfall in Qinghai.

• Construction and Applicaion of a New Index about the Qinghai-Tibetan Plateau Heating
• BEN Hairong;ZHOU Shunwu;QIAO Yu;SHAN Xing;LI Qiang
• 2017 Vol. 36 (6): 1487-1498.  DOI:10.7522/j.issn.1000-0534.2017.00009
• Abstract ( ) HTML PDF (4310KB) ( )
• Based on the ERA-Interim reanalysis data of monthly mean temperature in recent 36 years (1979-2014), distributions of zonal deviation temperature in the mid-upper troposphere (500~150 hPa) are analyzed. According to the distributions, a new index by averaging in the zonal temperature deviation over the Qinghai-Tibetan Plateau (QTP) from 500 to 150 hPa is introduced to measure the thermal forcing of the plateau. The index is called Plateau Heating Index (short for PHI). And seasonal variations of the index and its relationships with the circulation are also studied. The results show that the warm center of zonal temperature deviation in the mid-upper troposphere changes monthly. The main regular pattern shows that the warm center moves rapidly from Western Pacific to Qinghai-Tibetan Platea in spring, then moves to Western Pacific rapidly in autumn again. Changes of monthly PHI show a single maximum, which appears in July. And except the time from November to next February, the value of the PHI is always positive. Additionally, using monthly mean zonal winds and the potential height from ERA-Interim reanalysis data in recent 36 years (1979-2014), some patterns between the PHI and circulation in East Asia are found and they are also interesting. For the zonal winds in East Asia, the boundary of the positive and negative correlation coefficients between the zonal winds with PHI is located near 30°N in latitude. For specific performance, the correlation coefficients are positive in the north of the border and negative in the south of the border. Refer to the thermal wind relationship, the characteristic means that the westerly winds strengthen in the north of QTP and the westerly winds weaken in the south of QTP when PHI is strong, and vice versa. That is to say that the strong PHI benefits the strength of the subtropical westerly jets. Besides, the correlation coefficients between PHI and the potential height on 200 hPa over QTP are always positive, which indicates the heating in the troposphere in favorable to the increase of potential height over QTP. For further interpretation, the abnormality of PHI in summer can characterize the change of the South Asia High. When the value of PHI in summer is high (low), the anomaly of potential height over the plateau is positive (negative), and the South Asia High is strong (weak).

• Relationship between Ural Blocking and the North Atlantic Oscillation and Their Influence on Winter Weather over China
• XIAO Yiqing
• 2017 Vol. 36 (6): 1499-1511.  DOI:10.7522/j.issn.1000-0534.2016.00109
• Abstract ( ) HTML PDF (45136KB) ( )
• A case study on persistent snow-ice weather over South China from January to February in 2008 was investigated. It is shown that two Ural blocking (UB) events that have important influence on this extreme cold weather for different location, are associated with positive North Atlantic Oscillation events (NAO⁺). So NAO⁺ related UB events (NAO⁺ UB) are classified to four patterns as a result of their different locations, according to statistical analysis for location of UB in winter from 1979 to 2014, which are northward, southward, eastward, and westward UB events. Composited analysis reveals that the influence of southward and eastward UB events on winter cold events over China is more intense than that of the northward and westward UB events. A further study shows the NAO⁺ UB events are lag the NAO⁺ events by 3~6 days for their different locations. The result shows that the variety of zonal wind anomalies over Ural regions may be the main cause that lead to different location for NAO⁺ UB at the occurrence condition of NAO⁺. Furthermore, a statistical result for UB events and NAO events in winter from 1979 to 2014 shows that most UB events can be associated with NAO events, especially NAO⁺ UB events are far more than NAO^- related UB (NAO^- UB), and NAO⁺ pattern is more in favore of UB events. Therefore, the intensity of NAO^- UB is stronger than NAO⁺ UB, and lead to more intense cold weather over China. Moreover, it is shown that the impact of NAO⁺ and NAO^- events being absent with UB events on winter air temperatures over China is extremely weak. This hints that the UB events may be a bridge that links the winter weather over China and NAO events.

• Interannual and Interdecadal Variations Analysis of the Spring Southwest Vortex
• LI Li;LIU Haiwen;Lü Shihua
• 2017 Vol. 36 (6): 1512-1520.  DOI:10.7522/j.issn.1000-0534.2017.00016
• Abstract ( ) HTML PDF (4431KB) ( )
• Based on the four times a day ERA-Interim reanalysis data provided by ECMWF in the spring (March to May) of 1979-2013, the long-term trends, interannual variability and interdecadal variability of the number of spring southwest vortex are analyzed by using the methods of synthetic analysis, trend analysis and others. The result shows that the spring southwest vortex appeared 262 times in total and the annual average is 7.5 in 1979-2013. The number of the spring southwest vortex decline significantly in the 35 years, and the correlation coefficient with time is -0.652, which past the significance level of 0.001. There are also obvious interannual and interdecadal variations characteristics of the spring southwest vortex. The years with more spring southwest vortex are 1979, 1980, 1982, 1984, 1987 and 1988. The years with less spring southwest vortex are 2000, 2004, 2008, 2009 and 2011. The number of the spring southwest vortex appears as interdecadal significant mutation in 1989, shifts from more to less. The characteristics of atmospheric circulation which have effect on the number of spring southwest vortex are similar in both interannual scales and interdecadal scales. On the interannual scale, no matter the atmospheric circulation of the years of more (or less) spring southwest vortex or the most (or the least) year of it, in the lower troposphere, the geopotential height difference value distribution which is low in the northern Qinghai-Tibetan Plateau but high in the southern plateau and which is low in Lake Baikal but high in the sea of Japan are conducive to form the west wind difference value in the southern plateau and the south wind difference value in the eastern plateau. They are in favor of the formation of the cyclonic circulation near the Sichuan basin, and this cyclonic circulation can promote the generation and maintenance of the spring southwest vortex. On the decadal scale, because the positive geopotential height decadal difference value near Lake Baikal and negative geopotential height decadal difference value near the Ural Mountains can against the north cold air invading Sichuan province in China, combined with the positive geopotential height difference center near the Qinghai-Tibetan Plateau, which is unfavorable to the occurrences of spring southwest vortex, the two are the important reasons of the decadal reduction of the spring southwest vortex in 1989.

• Rainstorm and Flood Disaster Characteristics and Analysis of Circulation Background in Main Flood Season in Sichuan
• DENG Guowei;SUN Jun;RUAN Guibin;MA Zhenfeng
• 2017 Vol. 36 (6): 1521-1532.  DOI:10.7522/j.issn.1000-0534.2016.00099
• Abstract ( ) HTML PDF (11814KB) ( )
• Using the investigation data of heavy rainstorm-induced economic damage in Sichuan province area during 1984-2010, the characteristics of rainstorm-induced flood disaster in the last 30 years were studied. The population exposure and vulnerability index have been derived and used to do potential analysis of flood and economy damage. The disaster associated rainstorm was analyzed with the gauge stations observed daily rainfall data from China Meteorological Agency (CMA). Then we analyzed the atmospheric circulation for the heavy rainstorm which has caused flood and economic damage for Sichuan province using National Centers for Environmental Prediction (NCEP) reanalysis data from June to September (the main rainfall and rainstorm seasons) during 1981-2010. The results showed that the population affected due to rainstorm and flood disaster was increased during last 30 years. The increasing rate was more significant after the year of 1999. The population and economy potential damage analysis show that Chengdu city has a high exposure index value, but with a low vulnerability index. The exposure index of Ganzi/Aba area was the lowest in the province. The big city has a high population intensity influenced by the flood disaster, while the undeveloped area has a low population disaster intensity. The indices of population vulnerability and economic vulnerability of Sichuan were shown with an oscillation period of 2 years. The impact of heavy rains and flooding on Mianyang and Bazhong city, which was located in the rainstorm center of Sichuan province would be further exacerbated, and the cities, whose indices of population vulnerability and economic vulnerability were among the forefront of the province were mainly located in East Sichuan Area. In addition, circulation background characteristics of heavy rain in main raining seasons was analyzed to show that:South Asian High was "Western-type" and its intensity was weaker than annual average; Subtropical High was showed with a significantly quasi biweekly oscillation from July; Atmospheric circulation of the middle and upper troposphere in East Asia has a low frequency oscillation of 20~30 days in the mid-high latitude; Plateau vortex was showed with about 22 days of the oscillation cycle and Southwest flow in low latitudes was continuously transported to high latitudes. The flood associated heavy rainstorm maybe closely related these atmospheric circulation patterns.

• Variation Characteristics of Precipitation and Its Affecting Factors in Northwest China over the Past 55 Years
• LIU Weicheng;ZHANG Qiang;FU Zhao
• 2017 Vol. 36 (6): 1533-1545.  DOI:10.7522/j.issn.1000-0534.2017.00081
• Abstract ( ) HTML PDF (12760KB) ( )
• Based on the in-situ observations of precipitation at 128 stations in Northwest (NW) China and the NCEP reanalysis data from 1961 to 2015, regional changing trend and its regional distribution characteristics of annual and seasonal precipitation amount and number of rainy days were investigated. Furthermore, affecting factors of annual precipitation were also analyzed using the correlationship related to the average temperature and climatic indices. The results showed that:For annual precipitation, an increasing trend was observed with value around 0.1%·(10a)^-1~10.0%·(10a)^-1 in the middle-western part of NW while a decreasing trend was detected with value almost less than 5%·(10a)^-1 in the eastern part of NW. The seasonal precipitation showed an increasing trend in the western part of NW and showed a decreasing trend in the eastern part of NW in spring, summer and autumn. However, almost all parts of NW had an increasing trend in winter. Similarly, variation trend for number of rainy days in annual and seasonal time scales had the same pattern as precipitation. There was a negative correlation coefficient between annual precipitation and annual mean temperature in the western Hexi Corridor, side slope of the Qinghai Plateau and the eastern NW while a positive correlation was found in the Qinghai Plateau. In addition, the number of annual precipitation days is negatively correlated with the annual mean temperature in the most parts of NW. For the relationship between the annual mean variability of precipitation and temperature, a negative correlation with large value was detected in the south part of 37°N in the eastern NW and Xinjiang, while a positive value was found in the rest parts of NW. In terms of atmospheric circulation the westerly belt affected annual precipitation in most parts of NW and the East Asian monsoon and the South Asian monsoon mainly influenced the annual precipitation in the middle-north and south parts of NW.

• Research Review on Calculation Methods and Influential Factors on Areal Precipitation of Alpine Mountains
• WANG Lei;CHEN Rensheng;SONG Yaoxuan
• 2017 Vol. 36 (6): 1546-1556.  DOI:10.7522/j.issn.1000-0534.2017.00007
• Abstract ( ) HTML PDF (2199KB) ( )
• Areal precipitation is important for many branches of subjects, such as atmospheric sciences, ecology, hydrology and cryosphere science. The barriers of obtaining accurate areal precipitation are less precipitation data and the lack of relative research. The aim is to provide a research review on calculation methods and influential factors on areal precipitation in alpine mountains, and to indicate the likely research direction to obtain accurate precipitation data in alpine mountains. Nowadays, the main methods to obtain areal precipitation are ground observation, spatial interpolation, atmospheric numerical model and remote sensing. However, the precipitation observation stations are sparsely distributed and mainly distributed in low elevation areas because of the various conditions and severe weather conditions in alpine mountains. In addition, the sparse observation points and complex terrain conditions limit the use of spatial interpolation and atmospheric numerical model. When these two methods are used to calculate the distribution of precipitation, the results are too poor to apply to the study of hydrological processes. Ground-based radar is affected by terrain shading and defect of its structure significantly, and satellite remote sensing is limited by radar performance, spatial resolution and satellite transit. Hence, the applicability to the precipitation distribution, especially the regional precipitation in mountainous areas, is not ideal. The distribution of precipitation and amount of precipitation in alpine mountains are influenced by source of water vapor, slope, altitude, topography and different underlying surface. The terrain and the atmospheric circulation act on the precipitation, which leads to a great variability of the temporal and spatial distribution of precipitation, and also increase the difficulty of obtaining accurate areal precipitation data. Therefore, the further research on distribution of precipitation in alpine mountains should be carried out in many aspects. For those reasons, small range encryption observation, remote sensing spatial grid matrix observation and wide range net observation that had been carried out at Hulu watershed located in upstream of Heihe River. All of those are the important foundation of precipitation researches. At the same time, the research of satellite application in precipitation will improve the accuracy of satellite precipitation data and launch an efficient satellite remote sensing data assimilation research. In terms of numerical simulation, strengthen the study on refinement and downscaling atmospheric numerical model are also the ways to improve the accuracy of precipitation simulation.

• Fine-scale Characteristics of Rainfall in Erhai Lake Basin under Continuous Drought Conditions
• XU Anlun;LI Yu;YANG Fan;SU Jinlan;DONG Baoju;SUN Jihua
• 2017 Vol. 36 (6): 1557-1566.  DOI:10.7522/j.issn.1000-0534.2017.00014
• Abstract ( ) HTML PDF (5310KB) ( )
• Based on the 2010-2015 hourly rainfall data from 22 automatic weather stations in Erhai Lake basin, the fine-scale characteristics of rainfall was analyzed under continuous drought conditions. The results show that the temporal distribution of rainfall in Erhai Lake basin is uneven, which means that the rainfall is mainly concentrated in summer and autumn, and the nocturnal rainfall is obvious. The peaks of rainfall amount, rainfall intensity and rainfall hours appear around 06:00, 04:00 and 06:00 respectively, and their valleys around 13:00, 23:00 and 11:00 (Beijing time) respectively. The contributed percentage is the biggest for long duration rainfall events to the accumulated rainfall amount, bigger for medium duration rainfall events, the smallest for short duration rainfall events. The spatial distribution of rainfall in Erhai Lake basin is significant difference, which means that annual rainfall amount in west is more than that in east of the Erhai Lake area. The rainfall amount, and rainfall hours and different magnitude rainfall days are larger in spring, summer, autumn, winter and in whole year along Diancangshang Mountains line, and their largest values often appear in Yinqiao town, Dali city, Yunnan province. This largest values region is located in the upwind of prevailing wind (east wind), the second prevailing wind (east southeast wind) and in the downwind of the third prevailing wind (west northwest wind). In addition, the temporal and spatial distribution of rainfall in Erhai Lake basin is closely related to the monsoon climate, complex terrain, prevailing wind effect and so on.

• The Exploratory Research of Thresholds Value Causing Urban Waterlogging of Short Diachronic Strong Precipitation in Shanghai
• HE Fangfang;YANG Hanwei;MU Haizhen;XU Weizhong;XU Jialiang
• 2017 Vol. 36 (6): 1567-1575.  DOI:10.7522/j.issn.1000-0534.2017.00005
• Abstract ( ) HTML PDF (8561KB) ( )
• The hourly critical rainfall of short diachronic strong precipitation for urban waterlogging was calculated by inverse operation of SCS-CN model, which could simulate the runoff process of city rainfall combining with the runoff curve number and drainage ability in Shanghai. In the simulation, the downtown of Shanghai was divided to 284 drain units; the suburb was divided to 114 drain units. Also, the submergence depth of 5 cm was set as a critical value to judge whether the rainfall caused urban waterlogging. For a certain unit, when it appears strong rainfall in an hour, one certain point in the unit is submerged, and its depth is 5 cm, this precipitation is called the critical value causing urban waterlogging for this unit. Based on the conservation of water volume, this precipitation could be calculated by inverse operation of SCS-CN model. Besides, four typical examples of short diachronic strong precipitation was chosen, which led to serious disaster with more 110 urban waterlogging alarms. According to the relationship between hourly precipitation and 110 urban waterlogging alarms of four typical example, the result calculated by SCS-CN model could be verified. The results of inversion calculation of SCS-CN model and verification of four typical examples indicated that it may appear the waterlogging area and 110 alarms in downtown and most parts of suburb when the hourly rainfall is 30~40 mm·h^-1 (appearing disasters). The waterlogging area will expand to new-built town of suburb and 110 alarms will increase obviously when the rainfall is more than or equal to 50 mm·h^-1 (worse disasters). The waterlogging area will also appear in regions which are in higher ground of downtown and with stronger drainage ability in new-built town near the downtown, the 110 alarm was intensive and waterlogging area will appear in any regions of Shanghai when the rainfall is more than or equal to 70 mm·h^-1 (appearing heavy disasters). Rainstorm is the main meteorological disaster of Shanghai in summer half year. Rainstorm of Shanghai had turned to strong, local, extremely short-time change trend and the short diachronic strong precipitation had been one of the most destructive meteorological disasters from May to September of Shanghai since 1995, it was an important reason of water disasters and the serious water disasters was caused by it in Shanghai. Thus, research fruit on the critical value of short diachronic strong precipitation causing urban waterlogging could provide reliable scientific basis to draw up measure for effective prevention of urban waterlogging in Shanghai but the research reports with respect to the critical value of short diachronic strong precipitation were less.

• A Case Study of the Northern Hemisphere Stratospheric Sudden Warming in the Winter of 2009
• LI Yafei;HU Jinggao;REN Rongcai
• 2017 Vol. 36 (6): 1576-1586.  DOI:10.7522/j.issn.1000-0534.2017.00003
• Abstract ( ) HTML PDF (11767KB) ( )
• Based on 1979-2015 NECP/NCAR daily reanalysis data, this paper analyzed the evolution of circulation and the dynamical characteristics during the major Stratospheric Sudden Warming (SSW) in the winter of 2009, and revealed the precursory signal in troposphere before the occurrence of this SSW. The results showed that the stratospheric polar night jet quickly weakened in mid-January, meanwhile the polar stratospheric temperature rapidly increased. On 24 January, the 10 hPa zonal mean zonal wind averaged over 60°N-70°N reversed from westerly to easterly wind, indicating the onset of this major SSW. The easterly wind lasted until the end of February. By diagnosing planetary wave anomalies, it is found that the extratropical planetary wavenumber 2 component of geopotential height anomalies on 10 hPa rapidly increased from 10 days before the SSW onset. But the planetary wavenumber 1 component reduced in the corresponding period. The magnitude of the increase of planetary wavenumber 2 overwhelms the decrease of the planetary wavenumber 1. The vertical component of Eliassen-Palm (EP) flux anomalies by planetary wavenumber 2 reached the maximum value 5 days before the SSW onset. All these indicate that this SSW is a typical vortex splitting event driven by planetary wavenumber 2. This major SSW caused the strongest planetary wavenumber 2 EP flux anomalies in the winter of 2009 during the period 1979-2015. Further analyses on geopotential height anomalies on 500 hPa showed that the positive anomalies that located in the northeastern Pacific and western North America were highly in phase with the Alaska ridge of the climatological stationary waves before SSW onset. This distribution strongly enhanced the propagation of planetary wavenumber 2 from extratropical troposphere to stratosphere and thus acted as the strongest tropospheric precursory signal for the occurrence of this SSW. It is noted that although there are some other anomalous height centers that interfere with climatological stationary waves, they do not have significantly positive impacts on the SSW occurrence. For example, the negative height center that locates in the north Atlantic and eastern North America is in phase with the climatological trough over eastern North America and out of phase with the climatological ridge over Western Europe. It enhances the planetary wavenumber 2 but weakens planetary wavenumber 1 simultaneously. The net effect of this anomalous center on the stratospheric planetary wave activities is less obvious than that of the positive anomalies that locate in the northeastern Pacific and western North America.

• The Variation of Relative Humidity in the East of Chinese Mainland and Its Association with Sea-Land Thermal Contrast
• QI Qinghua;CAI Rongshuo
• 2017 Vol. 36 (6): 1587-1594.  DOI:10.7522/j.issn.1000-0534.2017.00018
• Abstract ( ) HTML PDF (10408KB) ( )
• Relative humidity is one of the most key environmental meteorological parameters for the formation and transformation of the fog and haze, and it can impact the atmosphere visibility. Sea-land thermal contrast is the important climatic background for the fog and haze weather in the eastern and coastal China. Considering the geographical environment and the sea-land temperature difference in the east of Chinese mainland, the multi-scale spatio-temporal variations of the relative humidity (RH) and the associated thermodynamic causes and mechanisms were tentatively analyzed from the perspective of changes in atmospheric circulation, water vapor transport and the precipitation. The results show that the sea-land thermal contrast mainly formed in the south area of Yangtze river and the east sea area of Kuroshio (mainly include the Kuroshio at source area and in East China Sea) in recent 50 years. Thus the sea-land temperature deference (SLTD) indicator was built by the subtraction of averaged temperature between the two areas. And this zonal sea-land thermal contrast was subject to an obvious long-term increasing trend superposed by distinct interannual (quasi-4a and quasi-7a) and interdecadal (about 17a) changes. The correlation analysis indicated that the SLTD had a close relationship with the RH anomalies in the band areas that including the middle reaches of Yangtze river, the Huanghuai area, the North China and the coastal zones east of it (negative correlation area) and the South China (positive correlation area). Regression analysis found that the weakened (enhancement) of the zonal sea-land thermal contrast in winter mainly results in the southwest (northeast) anomalies of the monsoon circulation, which tends to regulate the water vapor transport from the eastern bay of Bengal and the South China Sea (the east China seas) to the east of Chinese mainland, and then it can impact the changes of RH at above areas through the restricttion in the form of water vapor transportation and precipitation. In addition, the strengthening of the SLTD was likely to cause the RH decrease in the North China, while significantly increase in the South China, and vice versa. The analysis above is attempted to provide an important scientific basis for figuring out the RH variation and its relationship with the occurrence of the fog and haze in the hotspot areas as well as the evolution in the future, which is very significant to the scientific adaptation to the climate and environment changes in development areas in the eastern China.

• Analysis of Atmospheric Circulation Characteristics and Mechanism of Heat Wave and Drought in Summer of 2013 over the Middle and Lower Reaches of Yangtze River Basin
• WANG Wen;XU Jinping;CAI Xiaojun;SUN Chang
• 2017 Vol. 36 (6): 1595-1607.  DOI:10.7522/j.issn.1000-0534.2016.00129
• Abstract ( ) HTML PDF (20970KB) ( )
• Based on the daily temperature and precipitation data of 90 stations from 1981 to 2013 in the middle and lower reaches of Yangtze River (MLRYR) in China, the NCEP/NCAR daily reanalysis data and monthly NOAA Extended Reconstructed Sea Surface Temperature v4 (ERSSTv4) data, the general characteristics and effect mechanism of the continuous hot-dry weather occurred in MLRYR during the summer of 2013 had been investigated. The results were shown as follows:(1) The rainfall was less 49.43% than the historical average. A drought was started in the middle and last dekad of July and then developed gradually, the most severe drought was happened in the first and middle dekad of August while the whole MLRYR was caught in moderate to severe drought, some local areas of MLRYR were reached special drought with the daily mean temperature on the high side 5℃. (2) Affected by the negative phase of EAP (East Asia Pacific)/PJ (Pacific Japan) teleconnection, WPSH (western Pacific subtropical high) was larger, stronger and the position was westward than normal, controlled MLRYR for a long time, which was one of the most direct reasons for why the heat wave and drought happened. Because of the strong EASM (East Asian summer monsoon) and northward EASWJ (East Asian subtropical westerly jet), the warm-moist and cold-dry air did not match in MLRYR, combined with the descending motion effects, which was not conducive to the formation of precipitation. (3) By the influence of "Silk Road"teleconnection from August 1st to 2nd pentad, Rossby waves originated from the North Atlantic along the westerly jet stream waveguide dispersed to East Asia-Pacific region, enhanced two height anomaly centers at middle and high latitude of the negative phase of EAP/PJ teleconnection, which played an important role in the maintenance and development of its morphology, and prompted the abnormal development of the WPSH to the peak period. (4) The high SST anomaly in the warm pool of the Western Pacific is the main reason for the long-term maintenance of negative EAP/PJ teleconnection. While the anomalous high SST in the North Atlantic Ocean in July is closely related to the westerly jet anomaly, which is an another possible cause for the configuration of the East Asian monsoon system.

• Characteristic and Correlation Between Surface Temperature and 0℃ Isotherm Height Derived from ERA-Interim Reanalysis and Radiosonde Data
• CAO Yang;CHEN Hongbin;LI Jun;SU Debin
• 2017 Vol. 36 (6): 1608-1618.  DOI:10.7522/j.issn.1000-0534.2017.00011
• Abstract ( ) HTML PDF (5549KB) ( )
• In this study, The correlation coefficient (R), bias (B_ias), and mean absolute deviation (M_ad) were calculated between the surface temperature and 0℃ isotherm height by using the ERA-Interim reanalysis data and station observation data of Beijing. The correlation of surface temperature and 0℃ isotherm height was analyzed. The fitting linear relationship of surface temperature and 0℃ isotherm height was obtained, and the usefulness of the relationship also was proved by using other set of observation data. The results indicate that there is a good correlation between ERA-Interim reanalysis data and site observation data for both surface temperature and 0℃ isotherm height in four seasons and 10 years studied with R larger than 0.89; R values for the surface temperature and 0℃ isotherm height from the reanalysis data are little lower than those from the site observation data and the bias are mostly less than 2℃ and 200 m. The surface temperature and 0℃ isotherm height exhibit the similar characteristics of seasonal variation with R larger than 0.8, both from the reanalysis data and observation data, and R at 20:00 (Beijing time) is slightly larger than that at 08:00, which all have passed the statistically significant level at 0.01. the correlation coefficient R between the calculated and observed 0℃ isotherm height is very high with the acceptably small B_ias, and M_ad. So, 0℃ isotherm height calculated with the relationship between the surface temperature and 0℃ isotherm height can be applied to other practical use.

• Evaluation and Correction for the Deviation of the Surface Air Temperature based on 24 CMIP5 Models over China for 2006-2015
• ZHANG Bei;DAI Xingang
• 2017 Vol. 36 (6): 1619-1629.  DOI:10.7522/j.issn.1000-0534.2016.00136
• Abstract ( ) HTML PDF (16641KB) ( )
• The deviation of surface air temperature projected by 24 models of the Coupled Model Inter-comparison Project phase five (CMIP5) over China from 2006 to 2015 under the Representative Concentration Pathways (RCPs) scenarios was revealed and corrected. Compared with the data from NCEP/NCAR, the differences of projected temperature among the 24 models are more obvious in the east than the west over China. The annual and seasonal mean model-ensemble temperature are both underestimated in most parts of China, while the deviation is larger in the western region and it is largest in Tibet Plateau. In summer, the uncertainty of projected temperature is lower than other seasons. However, the phenomenon of underestimating temperature is enhanced obviously in winter. In addition, the higher emission intensity would enhance the underestimation of temperature in the most parts of China and the impact is more evident to the western regions, but the deviation would be lower in Tibet Plateau and Yunnan-Kweichow Plateau. Furthermore, the inter-annual differences of the temperature deviations are similar, except in the northeastern regions, and the patterns of the deviations are similar between El Niño years and La Niña years. After the terrain correction, the deviation of model temperature could reduce about 20%, and the deviation of the complex terrain region is effectively correction. The EOF indicates that historical simulation temperature by CMIP5 models has climate drift and the deviation is associated with topographic deviation. By deducting the climate drift, the effect of topographic and interpolation can be eliminated. The deviation of annual temperature would decrease about 72%. The models temperature is still underestimated and the deviations are about ±1℃ in most parts of China. However, this method makes the deviation turn to warmer in western region in summer and it is still colder in eastern region in winter. This suggests that the areas where the temperature deviations of models are lower would be vulnerable to the impact of deviation rate. Therefore, except the climate drift of models, the temporal evolution characteristics of deviations must be considered in the more detailed error correction methods.

• Review on Modeling Evapotranspiration of Land Surface Based on the Evapotranspiration Models and Micro-Meteorological Data
• GAO Guanlong;FENG Qi;ZHANG Xiaoyou;YU Tengfei
• 2017 Vol. 36 (6): 1630-1637.  DOI:10.7522/j.issn.1000-0534.2016.00115
• Abstract ( ) HTML PDF (480KB) ( )
• Evapotranspiration (ET) is the key component of water cycles and energy balance. This paper summarized and analyzed the structures, meanings of parameters, application conditions, and improvement and application of the most commonly used models. Results indicated that:The P model is only suitable for calculating potential ET; The P-M model, without partitioning evaporation and transpiration, is not suitable for sparse vegetation. There are two ways for calculating r_c of the P-M model, namely using the Katerji-Perrier (K-P) model and the Todorovic (T) model; The P-T model can always give the most accurate estimates by calibrating α value despite its simple structure; The M-B model was proposed on the basis of fir forests and without considering the influence of r_a on ET, so its application is restricted; The S-W model is suitable for sparse vegetation, and researchers have mainly focused on improving the model accuracy under specific conditions. However, the complexity and number of parameters were also increased; The S-S-W model has a simpler structure, which reduces the number of parameters and improves the opplicability of a dual-source model. However, the applicability needs to be tested in the future; The C model was rarely used due to the complex structure and a number of parameters. Research in the future will mainly focus on proposing simpler models by calibrating and coupling the ET models, which are on the basis of accurate measurements of the parameters in different natural ecosystems and under various environmental conditions.

• Comparative Analysis of Structure Characteristics of MCC over the Yellow River Midstream between the Spring and the Summer
• ZHAO Guixiang;WANG Xiaoli;WANG Yijie
• 2017 Vol. 36 (6): 1638-1654.  DOI:10.7522/j.issn.1000-0534.2016.00138
• Abstract ( ) HTML PDF (16219KB) ( )
• Based on observational data, encryption data of automatic station, NCEP reanalysis and satellite data, the structure characteristics of MCC occurred on 1 April and 2 August 2015 over the Yellow River midstream was comparatively analyzed. The results are as follows:(1) The formation stage of spring MCC was fast and mature was slow. It has forward propagation feature. Precipitation was stable, rain clusters moved slowly, and the rainstorm was mainly caused by long duration of precipitation. While the formation stage of summer MCC was slow and mature was rapid. It has backward propagation feature. It was mainly convective precipitation, rain clusters were mobility, and heavy rainfall mainly caused by short-period strong precipitation. Maximum hourly rainfall occurred in different areas at different stages of their life time. (2) The spring MCC was formed under the background of the southwest airflow at the whole layers and strong baroclinic property. The spatial structure characteristics of the divergence field was vertical. But the summer MCC was formed under the background of flat westerly circulation on 500 hPa, front of anticyclone on 200 hPa, and the weak baroclinic property. The spatial structure characteristics of the divergence field was declining. In their later development, there were significant differences in water vapor, thermal and dynamic structure. (3) Two MCC were formed and developed in the coexistence region of conditional, convective, and symmetric instability. The formation of MCC was related to the instability and the unstable energy, but their development were more closely related to the continuous increase of the unstable energy, and continuous enhancement of symmetric instability, especially in midsummer. (4) Intrusion of dry cold air at middle and upper layer, continuous strengthening of convergent ascending motion caused by the curvature vorticity at the whole layers, and symmetric instability were important triggering mechanisms of MCC in spring. Mesoscale convergent ascending motion at lower layer caused by shear vorticity, symmetric instability, and gravity wave propagation were the main triggering mechanisms of MCC in midsummer.

• The Characteristics of Cloud Properties in Deep Convective Clouds across China with the CloudSat Dataset
• YANG Bingyun;WU Xiaojing;GUO Zheng
• 2017 Vol. 36 (6): 1655-1664.  DOI:10.7522/j.issn.1000-0534.2017.00006
• Abstract ( ) HTML PDF (9081KB) ( )
• The deep convective clouds are important regulators of the earth-atmosphere system and also closely relate to the formation of many extreme weathers such as downbursts, storms and lightning. The measurement of cloud profile radar (CPR) from CloudSat has the advantage in detecting the accurate properties in deep convective clouds in different altitudes. The spatial and temporal variations of the probability and cloud microphysical properties in deep convective clouds, for exemple, the ice water content (IWC), liquid water content (LWC), ice water path (IWP) and liquid water path (LWP), were analyzed across eleven sub-regions in China based on the CloudSat dataset during 2007-2010 and 2013-2014. The results indicate that the probability of deep convective clouds decreased from southeast to northwest parts generally. The high values were mainly concentrated over the southeast of Northwest China, the southeast of Tibet, the east and south of Southwest China, the west and south of Huanghuai, Jianghan, Jianghuai, Jiangnan, and South China. Generally, it can be demonstrated that the deep convective clouds are more likely to occur in summer. For each area in different seasons, the highest value of the probability of deep convective clouds in total altitudes was 10.34% over Jiangnan in summer. The value of probability was much larger over Jiangnan, Jianghan, Jianghuai or Huanan than other areas, while it was lower over Northwest China. Moreover, among the different altitudes, the probabilities were located below 18 km and the maximum reached 11.31% at roughly 4.08~4.56 km over Jiangnan. The maximum value of IWP and LWP occurred over South China in summer and Huanghuai in autumn, respectively. Over Tibet, the value of IWP was much larger than that of LWP in the deep convective clouds, because the average altitude of Tibet was relatively high and the ice clouds were formed much easily than liquid clouds. Vertically, the maximum IWC with a magnitude of 1 018.87 mg·m^-3 occurred near the altitude of 19.44 km over Jiangnan in summer. Two peaks of IWC were detected at 6~8 km, and 14~18 km where the significant seasonal difference occurred. In addition, the maximum LWC was 411.50 mg·m^-3 at the altitude of 9.36 km over Jianghuai in winter and the peak of LWC in the vertical height occurred from 2 km to 6 km. The results in this work can explain climatic features of deep convective clouds and provide an observational basis for weather modification and simulations of deep convective clouds in models.

• A Study on the Consistency and Deviation Correction of the Radar Reflectivity Factor of Three Ground-based Radars in Southern Jiangsu
• HAN Jing;CHU Zhigang;WANG Zhenhui;XU Fen;LI Nan;ZHU Yiqing;ZHANG Hanyun
• 2017 Vol. 36 (6): 1665-1673.  DOI:10.7522/j.issn.1000-0534.2016.00137
• Abstract ( ) HTML PDF (10848KB) ( )
• With the development of sophisticated meteorological equipment, weather radar is becoming an effective tool for monitoring and providing early warning of severe weather, especially small-scale disaster weather events. China new generation of weather Radar can be used for quantitative precipitation estimation (QPE) in large area, but the inconsistency between the data of adjacent radars may affect the networking application, especially in terms of Multi-Radar precipitation evaluations, data assimilation, cloud and precipitation physics research. In this paper, Precipitation Radar (PR) data, collected by the tropical rainfall measuring mission (TRMM) satellite, was used as a unified reference to analyze the consistency of 7 matched events of the PR and three Ground-based Radars (GRs) in southern Jiangsu (Nanjing, Changzhou and Nantong) during the period from June to July, 2010. Through the following seven-steps pretreatment:(1) PR and GR data match-up, (2) GR data azimuth adjustment, (3) GR data terrain blocking analysis, (4) GR data radial distance selection, (5) GR data vertical height selection, (6) Ku-adjusted, (7) NUBF analysis, the available best comparable data were used to establish a revisions relationship, the error correction and analysis was carried out. The results show that:(1) the reflectivity of Nanjing radar was about 3.5 dB smaller than that of Changzhou radar, while the reflectivity of Changzhou radar is about 0.9 dB smaller than that of Nantong rador, 3 km height of echo intensity mosaics obvious discontinuity; (2) after deviation correction, the difference of reflectivity between Nanjing and Changzhou, Changzhou and Nantong were reduced to 0.3 and 0.2 respectively, mosaics effect was significantly improved. The method may be applied to improve the quality of precipitation data products from the GR network and their quantitative application for the southern region. It can also be used for the further development of spaceborne PR and GR network data analyses, and provide an important reference value for the accuracy of multi-radar joint precipitation estimates and the application of radar networking mosaics.

• The Analysis on an Infrequent Southerly Gust of Beijing in Summer
• YU Bo;JING Hao;SUN Jisong;ZHANG Wenlong
• 2017 Vol. 36 (6): 1674-1681.  DOI:10.7522/j.issn.1000-0534.2016.00142
• Abstract ( ) HTML PDF (13012KB) ( )
• The infrequent southerly gust in Beijing in 2014 summer was analyzed by using observational data, NCEP/NCAR reanalysis data, Doppler radar data and VDRAS data. Under the unfavorable weather condition, there was 6~8 grade southerly gust in most area of Beijing in the midnight on 14 July 2014. The causes of the gust can be concluded in two aspects. Firstly, the local heavy precipitation between southeast of Hebei province and north of Shandong province caused local temperature decrease and pressure surge, therefore, the outflow of cold air was formed. Because of weak northerly wind, warm air in the north of cold pool and topography, the outflow turned to the southerly wind. Secondly, the positive effect between southerly wind and local precipitation in Pinggu District, which is in the northeast of Beijing, was beneficial to convergence for precipitation. With the development of southerly wind, the ascending motion also strengthened. Consequently, the pumping action of precipitation promoted the acceleration of southerly wind.

• Climate Change Characteristics of Atmospheric Environmental Capacity in Hebei Province during 1972-2013
• XU Qihui;FAN Yinqi;JING Yuanyuan;DU Kangyun;ZHANG Jinlong;LIU Jinping
• 2017 Vol. 36 (6): 1682-1692.  DOI:10.7522/j.issn.1000-0534.2016.00133
• Abstract ( ) HTML PDF (11421KB) ( )
• Based on wind, cloud and precipitation data of 79 meteorological stations over the Hebei province, the atmospheric environmental capacity (AEC) was calculated by applying A value method, climate change characteristics and trends of AEC were analyzed. The time points of abrupt change for AEC was tested by Mann-Kendall and Moving-T technique. Based on EOF analysis, the temporal and spatial variation features of AEC were studied. Results show that the climatic value of seasonal spatial distribution characteristics of AEC is relatively consistent, northwest of Zhangjiakou and Chengde area is significantly greater than the other parts, and Hebei Piedmont is lower than the surrounding, climatic value of AEC changed from high to low throughout the year. From 1972 to 2013, the annual and seasonal AEC have been observably decreasing in most part of Hebei and the abrupt change point is spring in 1983, summer and autumn both in 1998, winter in 1988. The first 2 eigenvector of EOF reflect the most characteristics of annual and seasonal spatio-temporal distribution of AEC from 1972 to 2013, the first eigenvector of contribution rate is more than 43%, reflects holistic characteristics in the whole province, the corresponding time coefficient indicates that there is an interdecadal weakening trend of AEC.

• Investigation on Norm of Haze Identification based on Hourly Auto-monitored Visibility
• SHI Chun'e;ZHANG Hao;MA Jinghui;WU Biwen;WANG Xing;CHEN Rulong;YANG Yuanjian
• 2017 Vol. 36 (6): 1693-1702.  DOI:10.7522/j.issn.1000-0534.2016.00130
• Abstract ( ) HTML PDF (2537KB) ( )
• At present, auto-monitored visibility was adopted by more and more meteorological stations in China.At the same time, some weather phenomena were not recorded by observer any longer.It is necessary and urgent to set up a reasonable norm of haze identification using auto-monitored meteorological parameters, so that not only it contains information of air quality, maintains the continuity of annual haze days, but also the method is easy to put into application.In this paper, through summarizing of norms and some references related to haze identification, basic parameters were chosen for haze diagnosis.Based on analysis of relationship between PM_2.5 concentration and relative humidity using hourly meteorological data at observatories of six cities in Anhui province, together with hourly PM_2.5 concentrations published by environment department, four initial schemes were proposed, that are, auto-monitored visibility lower than 5 km, adopting critical relative humidity (RH_c) as 90% (or 95%), considering PM_2.5 concentration or not.Then, hourly and daily hazes of 2015 were re-diagnosed for those cities based on those schemes.Some rules were considered in the investigation of objective standards for haze identification, e.g., haze being indicator of air pollution, maintaining the continuity of annual haze days.The results indicated that hourly haze can be identified as "excepting hourly rainfall over 0.1mm, the auto-monitored visibility no more than 5 km with the RH lower than 90% (RH_c=90%), neglecting PM_2.5 concentration".A day with consecutive 6 h haze can be defined as a haze day.The annual haze days obtained by this method were reasonable and a good indicator of air quality.

• Relationship between Precipitation Shielding and Positive Cloud-to-Ground Lightning Flashes in Thunderstorm Cell
• SHI Haifeng;GUO Fengxia;WANG Haoliang;LU Ganyi;LIU Zupei;BAO Min;LI Yawen
• 2017 Vol. 36 (6): 1703-1712.  DOI:10.7522/j.issn.1000-0534.2016.000128
• Abstract ( ) HTML PDF (6939KB) ( )
• In order to understand if precipitation shielding can cause positive Cloud-to-ground (CG) lightning flashes in thunderstorm cell, a normal tripole charge structure model of thunderstorm, including lightning discharge parameterization, was established and used to study the relationship between precipitation shielding and positive CG lightning flashes in thunderstorm cell through changing altitudes and densities of middle negative and lower positive charge regions.The results indicate, when precipitation occurs in thunderstorm cell, the altitudes and charge densities of the middle negative and lower positive charge region will decrease, which will change the distribution of spatial electrical field and potential and then triggered lightning.When the altitudes of the middle negative and lower positive charge region decrease for the reason of downward flow caused by precipitation, the maximum electrical field strength will decrease and its correspond electrical potential will increase, thereby, the electrical potential difference between the point of the maximum electrical field and ground surface will increase, the positive leader is easier to reach the ground to form positive CG lightning flashes.And when the charge densities of the middle negative and lower positive charge region decrease for the reason of the electric charge adhere to precipitation fell out of the cloud, the maximum electrical field strength will decrease and its correspond absolute value of electrical potential will decrease first and then increase.During the absolute value of electrical potential is decreasing, which is negative and its orientation is vertical upward.It is of course impossible to produce a positive CG lightning flash.But when the densities of middle negative and lower positive charge region decrease to a certain degree, the value of the electrical potential will be positive and its orientation is vertical downward.Then the value of the electrical potential will keep increasing.The electrical potential difference between the point of the maximum electrical field and ground surface will increase too, the positive leader is easier to reach the ground to cause positive CG lightning flashes.So, the hypothesis that precipitation shielding can cause positive CG lightning flashes is reasonable in thunderstorm cell.

• Comparative Analysis on the Applicability of Different Typical Year Generating Methods in Solar Energy Resource Assessment
• CHANG Rui;SHEN Yanbo;GUO Peng
• 2017 Vol. 36 (6): 1713-1721.  DOI:10.7522/j.issn.1000-0534.2017.00013
• Abstract ( ) HTML PDF (5162KB) ( )
• Solar energy development and utilization plays an important role in haze governance and fulfilling the reduction commitments in advance. In order to make accurately optimal design and performance evaluation of the solar energy conversion systems, typical meteorological year (TMY) data are needed. A TMY is a data set of daily values of solar radiation and meteorological elements for a 1-year period in this paper. It consists of months selected from individual years and concatenated to form a complete year. In this paper, the Finkelstein-Schafer statistical method, which was initially developed by Sandia national laboratories, is firstly applied by analyzing a 30-year period (1985-2014) daily measured datasets which include global solar radiation, wind speed, relative humidity, air temperature, pressure and dew temperature (an intermediate variable) in order to generate typical meteorological year (TMY) for nine representative meteorological stations in China. Therefore, the TMY data sets obtained here represent conditions judged to be typical over a long period of time (30 years). Meanwhile, the annual global horizontal irradiations (GHI) are also calculated by the normal distribution method and the max probability density method, which are the widely used in the engineering practice. Then, the emphasis is placed on the comparison between Sandia method, the normal distribution method and the max probability density method. It is found that:(1) annual global horizontal irradiations (GHI) calculated from Sandia and normal distribution methods matched well with each other, and it showed a significant deviation in GHI calculated from the max probability density method; (2) despite of the similar annual GHI, significant variations exist in the monthly GHI difference between Sandia and normal distribution methods which was supposed to be connect with the complexity of the local weather conditions; (3) the Sandia method is of the good representative of the typical atmospheric conditions but requires a lot of meteorological observations during the calculation process; (4) the normal distribution method is suitable for quick and effective application since only solar radiation observation is required during the calculation, but it is lack of representative of the local climatic conditions. It is worth noting that because the TMY dataset represents typical case rather than extreme conditions, it is not suited for designing systems and its components to meet the worst condition occurring at a local area. These findings in this paper will be very useful for the performance evaluation of solar energy conversion systems, heating, ventilation and other solar energy dependent systems.