ISSN 1000-0526
CN 11-2282/P

Volume 41,Issue 4,2015 Table of Contents

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  • 1  Numerical Simulation Analysis on Impact of Taihang Mountain and Vapor Sensitivity on the 21 July 2012 Extremely Severe Rainstorm in Beijing
    WANG Yuhong XU Guoqiang JIA Lihong ZHAO Yang
    2015, 41(4):389-400. DOI: 10.7519/j.issn.1000-0526.2015.04.001
    [Abstract](1897) [HTML](218) [PDF 11.53 M](1360)
    Using the GRAPES_Meso model, the numerical simulation, topographic sensitivity experiments and vapor sensitivity experiments are carried out for the extremely severe rainfall that happened in Beijing Region from 21 to 22 July 2012. The conclusions are as follows. In the process of the severe rainstorm, the convergence of upward current and vapor is reinforced by the terrain effect of Taihang Mountain, thus reinforcing the intensity of precipitation. Due to the convergence of southeast, southwest and north winds in the lower troposphere, the intensity of cyclonic vorticity is strengthened, which is helpful for the vortex to stay above Beijing for about 5 hours. The topographic relief and altitude of mountain have great influence on rainfalls, and the effect of topographic relief is greater than the altitude. In the process of the rainstorm, small changes of the vapor condition lead to significant difference in vapor transportation. The vapor condition influences the rainfalls markedly.
    2  Analysis of the Common Effect of Vortex and Subtropical High on Rainstorm Fall Area
    SUN Xingchi GUO Junjian WANG Yehong HOU Shumei
    2015, 41(4):401-408. DOI: 10.7519/j.issn.1000-0526.2015.04.002
    [Abstract](1446) [HTML](184) [PDF 5.46 M](1325)
    By using conventional observation data and NCEP 1°×1° reanalysis data, analysis on the common effect of vortex and subtropical high on rainstorm process is done. It is found that the heavy rainstorm fall area is not consistent with the vortex location and path. So, it is not always reasonable to forecast the rainstorm fall area following the location and path of vortexes. Forecasters should do some analysies on the spatial structurs of impact systems, the developing stages and the evolution characteristics of surface situation. When the impact system is frontal system, the initial convection system is often trigger by the frontal surface. Therefore, the fisrt rainstorm fall area tends to appear near the frontal suface, and then heavy rain in warm zone triggered by the cold front follows, not needing the strong dynamic convergence conditions. The heavy rains may fall far away from the vortex center, but is located in the high temperature and wet tongue on the edge of subtropical high. In addition, more attentions should be paid to the primary convective clouds on the surroundings and the heavy rain brought by the convective clouds.
    3  Diagnostic Analysis of Two Westbound Tropical Cyclones Affecting Yunnan
    ZHONG Aihua ZHOU Hong ZHAO Fuzhu YANG Suyu YAN Zhihui
    2015, 41(4):409-417. DOI: 10.7519/j.issn.1000-0526.2015.04.003
    [Abstract](1116) [HTML](76) [PDF 6.16 M](1138)
    The real time typhoon subjective positioning data from National Meteorological Centre, precipitation observation data from 124 national weather stations in Yunnan Province and the NCEP reanalysis data with 1.0°×1.0° horizontal resolution and 6 h temporal resolution are used to analyze the influence of No.1213 TC “Kai tak” and No. 1309 TC “Jebi” on Yunnan. The characteristics of the tropical cyclone (TC) moving path, circulation field, cloud, water vapor, dynamic conditions are analyzed. The results show that while “Kai tak” influences Yunnan, the position of Qinghai Tibet high pressure is by west and the subtropical high is zonal. TC lies in the southeast to easterly wind of the southwest side of the subtropical high, so the path of TC is the west path. But when “Jebi” affects Yunnan, the position of Qinghai Tibet high pressure is by east and the subtropical high is massive. TC is in the southerly wind of the west side of the subtropical high, so the path of TC is the northwest path, and the central part of Yunnan is in cyclonic wind field where the southwestern airflow and the subtropical high periphery south airflow gather creating heavy rainfalls there. When the two TCs affect Yunnan, the lower troposphere has a larger transport of water vapor. The water vapor mainly comes from TC, the South Sea of China and the Bay of Bengal. Moisture convergence center is in the front of the low pressure inverted trough, impacting the central and southern part of Yunnan from east to west along with the weather system. Heavy precipitation zone has convergence in lower level and divergence in higher level. Strong upward motion provides favorable dynamic mechanism for precipitation and releases unstable energy. Therefore, the forecasting of the shapes and positions of the Tibetan high and subtropical high is beneficial to forecasting the moving path of tropical low after its landing so that the forecast of rainfall intensity and location can be more accurate.
    4  Contrast Analysis of Two Snowfall Events in Hubei 2013
    ZHANG Pingping WU Cuihong QI Haixia WANG Xiaoling ZHANG Ning
    2015, 41(4):418-426. DOI: 10.7519/j.issn.1000-0526.2015.04.004
    [Abstract](1385) [HTML](97) [PDF 5.40 M](1321)
    Based on conventional weather chart, NCEP reanalysis data, microwave radiometer products and Doppler radar observations, the water vapor, thermal and dynamic conditions, temperature and humidity stratification during 7-8 (dry snow) and 18-19 (wet snow) February 2013 are comparatively analyzed. The results show that: (1) The vapor transportation branch in dry snow process is weak southwest air current at 700 hPa, but the vapor transportation branch in wet snow process is the strong southwest air current at 700 hPa and the southeast air current at 850 hPa with sufficient moisture. (2) There is strong cold advection and stable atmospheric layer in dry snow process. However, strong warm advection exits in wet snow process in which cold and warm flow intersection makes atmospheric instability enhanced. (3) The southwest current ascends on the cooling cushion in dry snow process with convergence at middle high levels, and the secondary circulation inhibits ascending motion. In wet snow process, the cold air inserts the bottom of warm flow, making warm flow lifted, and the secondary circulation supplies a continuous and powerful updrafts. (4) The temperature is lower than 0℃ at all levels with cold inversion layer and low vapor density, liquid water content and water vapor content at all levels in dry snow, and the level of -10℃ is found at 925 hPa. On the contrary, warm inversion layer exists in wet snow with high vapor density, liquid water content and water vapor content at all levels, and the level of -10℃ is at 500 hPa. Finally, three dimensional physical model for the formation of dry snow and wet snow is built based on the above researches. The model reflects the main environmental background difference of temperature and humidity air stratification, which has certain reference significance for dry and wet snow forecasting.
    5  Characteristics of Three Sustained Dense Fog Events Across the North China Plain
    ZHAO Yuguang LI Jiangbo LI Qingchun
    2015, 41(4):427-437. DOI: 10.7519/j.issn.1000-0526.2015.04.005
    [Abstract](1750) [HTML](559) [PDF 11.10 M](3031)
    Based on conventional observation, the NCEP reanalysis data (1°×1°), regional automatic meteorological station, data and L band sounding data, three persistent heavy fog events lasting over 10 days across the North China Plain in 2000-2013 are analyzed. The results show that all the three sustained dense fog events occur in the background of zonal circulation. The geopotential height field, humidity field, tempereture field and sea level pressure during the events are very similar. The surface weather conditions at the beginning of and during the dense fog events are also similar. The sustained dense fogs in the North China Plain are caused by the long term static and stable synoptic pattern which is attributed to blocking function of Mountain Taihang and Mountain Yanshan to cold airs in the zonal circulation setting. Several upper short wave troughs mobiling to the North China Plain and large scale sinking movement lead to the maintenance and enhancement of fog. Topographic convergence line caused by Mountain Taihang and moderately stable inversion which is formed by west current crossing Mountain Taihang also play an important role in the enhancement and maintain of the dense fog events.
    6  Characteristics and Forecasting Focus of Sea Fog in Ningbo
    ZHOU Fu QIAN Yanzhen JIN Liang SUN Junbo
    2015, 41(4):438-446. DOI: 10.7519/j.issn.1000-0526.2015.04.006
    [Abstract](1831) [HTML](103) [PDF 2.53 M](1225)
    Based on conventional meteorological data of Shipu Station from 1971 to 2011 and NCEP reanalysis data, characteristics of atmospheric environmental elements and weather backgrounds during the sea fog generation in Ningbo was analyzed. The results show that in most cases, the sea fog occurs in the period from April to June, mainly between 23:00 BT and the next 11:00 BT (especially from 23:00 BT to the next 02:00 BT), usually dissipating after 11:00 BT every day. The southwest and northeast winds in 2-3 grades are greatly conducive to the occurrence of sea fog. When relative humidity is 90%-95% and station pressure is 990-1002 hPa, frequency of sea fog increases with the increase of humidity and the decrease of pressure. However, when it comes to severe dense fog (visibility ≤50 m), relative humidity is 92%-95% and station pressure is 990-999 hPa, and the frequency increases with the increase of humidity and pressure. Weather systems including Jianghuai cyclone, Meiyu front and cold air can influence the occurrence and development of sea fog. Frontal fog usually occurs 2-3 days before weather system transits the area and when the upper air in the local area is influenced by southwest warm wet air. The upper air is in front of the southwest vortex when advection fog occurs. Under this condition, temperature difference between sea and air is 0-1.5℃ and -0.5-0℃ between dew point and sea underlying surfaces. Severe dense fog or dense fog occur under stable atmospheric stratification and in long standing and thick warm wet air flows, and meanwhile, cold ocean current from north continuously pours into the sea near Ningbo. Besides, sea fog intensity is related to warm advection and cold ocean current to some extent. All the above discussed perform an important role for the forecasting of sea fog and its intensity in Ningbo.
    7  Slant Path Water Vapor Retrieval with GPS and Application in Rainstorm Analysis
    WAN Rong FU Zhikang LI Wujie CHEN Bo YU Shengjie ZOU Qian
    2015, 41(4):447-455. DOI: 10.7519/j.issn.1000-0526.2015.04.007
    [Abstract](1440) [HTML](120) [PDF 3.82 M](1128)
    Slant path water vapor (SWV) contains the information of the nonisotropic distribution of water vapor in space, and it is the main data source for the 3D water vapor density analysis. The SWV time series obtained by observing stations directly the uneven distribution and changes of water vapor surrounding the station receiver. SWV algorithms is established by using the zenith precipitable total precipitable water vapor (PWV) inversion techniques, the wet mapping function, horizontal gradient function of wet atmospheric and the residual processing technology. By comparing the observations of GPS and microwave radiometer, we find the average deviation of SWV is 5.8 mm, and RMS is 4.4 mm in 50°-90° elevation range. In comprehensive analysis, the products of SWV time series that are combined with rainstorm observation cases by radar and microwave radiometer can better express the detailed features of the water vapor surrounding the station, such as the accumulation and the reduction of water vapor before and after the precipitation respectively, is which would be new reference information for the warning and forecasting of severe convection weather and related mechanism research.
    8  Understanding of the Fundamental Concept of Atmospheric Data Assimilation
    ZHU Guofu
    2015, 41(4):456-463. DOI: 10.7519/j.issn.1000-0526.2015.04.008
    [Abstract](1675) [HTML](905) [PDF 394.04 K](1556)
    What is it that makes atmospheric data assimilation come to be a discipline with its own theoretically mathematical foundation and formalism? In this article it is highlighted that the random variable is the fundamental concept of atmospheric data assimilation. This lies in two aspects. First, probability theory and mathematical statistics, which are oriented to random variables, can be used as the mathematical foundation of atmospheric data assimilation, and thus atmospheric data assimilation is equipped with its mathematical formalism which is derived from its criterion for an optimal estimate on the basis of estimation theory. So in this sense the essence of science for atmospheric data assimilation is built on the concept of random variable. Second, data under the concept of random variable can find a way to understand the clear step by step expansion of useful information contents used during the historical progress of atmospheric data assimilation, which helps to know a simple cognitional intrinsic logic of development of atmospheric data assimilation.
    9  Preliminary Study About the Forecasting of Winter Precipitation Types in Dalian
    SUI Yuxiu YANG Jingtai WANG Jian ZHOU Meie XIAO Jian WANG Lina BIAN Ruobin
    2015, 41(4):464-473. DOI: 10.7519/j.issn.1000-0526.2015.04.009
    [Abstract](1181) [HTML](125) [PDF 763.22 K](1075)
    Using the surface and air sounding observation data of winter precipitation in Dalian from 2003 to 2012, we obtained the maximum and minimum factors which were used to judge the precipitation types and classified as “MAX class” and “MIN class” to analyse and discuss the precipitation process dynamically. During the process of discussing the factors which affect the precipitation types in winter of Dalian, the method of the mean temperature of layers was used to research the precipitation types. Comparing it with the method before, which use the temperature of single layer or the thickness of layer, we considered the evaluation results of all factors, and found using the factors which belong to the category of mean temperature are better than the factors of other categories. The mean temperature of the conventional isobaric surfaces is easy to compute, suitable for the operation of weather forecasting. In addition, we also designed a “step expel method” and use it to validate the winter precipitation types in Dalian 2013, on the basis of the surface and air sounding data of Dalian, and have obtained ideal results. Then we used the GSM grid data of Japanese mathematical forecast in 2013 to simulate the weather prediction, getting good results.
    10  Study on Identification Criterion for Precipitation Phase in Winter Kunming
    XU Meiling LIANG Hongli JIN Shaohua MA Zhimin NIU Fabao MIN Ying
    2015, 41(4):474-479. DOI: 10.7519/j.issn.1000-0526.2015.04.010
    [Abstract](1434) [HTML](143) [PDF 635.75 K](1200)
    Based on precipitation and weather phenomena data from Kunming Station in winter from 1952 to 2013, the climatic characteristics of winter snowfall in Kunming are analyzed. In addition, using surface and upper air data, six physical quantities such as temperature at 500 and 700 hPa, 0℃ level height, geopotential thickness between 500 and 700 hPa, daily lowest and average temperature at surface are selected. The phase of precipitation and snow is analyzed, by using the principle of highest TS score to determine physical quantities’ threshold range. Different weights are offered to each criterion, using weight linear method to set synthetic criterion of snowfall, through different combined experiments on snowfall criterion of six physical quantities, and considering the operational application of synthetic criterion. Finally, three single criterions are selected, that is, temperature at 700 hPa, geopotential thickness between 500 and 700 hPa and daily lowest temperature at surface, and combined into synthetic criterion. In addition the precipitation phases during 13 rainfall weather processes in 2014 are tested by using WRF model. The results show that synthetic criterion could provide valuable reference for objective forecast of precipitation phase in winter, Kunming.
    11  Climatic Characteristics over China in 2014
    HOU Wei ZOU Xukai WANG Pengling YE Dianxiu ZHOU Bing HUANG Dapeng LI Ying ZHAO Lin WANG Youmin ZHU Xiaojin ZHAO Shanshan WANG Yang ZHONG Hailing
    2015, 41(4):480-488. DOI: 10.7519/j.issn.1000-0526.2015.04.011
    [Abstract](1530) [HTML](255) [PDF 11.38 M](1754)
    In 2014, the annual mean air temperature over China was 0.5℃ above normal making the year become the sixth warmest year together with 1999 since 1961. Temperatures were above normal in spring, summer, autumn and winter for the whole country as a whole. The mean of annual total precipitation in 2014 in China was 636.2 mm, which was near normal with 3% less than that in 2013. In 2014, the temporal and spatial distribution of precipitation was uneven. The first rainy season in South China began earlier with a larger amount of precipitation than normal. The rainy season in Southwest China started later and ended earlier with a smaller amount of precipitation than normal. The precipitation in Meiyu region was more in the south but less in the north while the Jianghuai Region missed Meiyu during this summer. The rainy season in North China was not evident. The beginning of autumnal rain of Huaxi (Western China) started earlier and ended later with a larger amount of precipitation than normal. In 2014, some regions of South China suffered a large number of heavy rains and floods, and autumnal rainfall in Huaxi and Huanghuai Regions was frequent, but the weather and climatic extreme events happened less frequently than that in 2013, with less disasters caused by torrential rainfall, floods and droughts. The death toll and disaster hit areas were significantly less than normal. In general, 2014 was a year with less meteorological disasters.
    12  Anomalies of Ocean and Atmospheric Circulation in 2014 and Their Impacts on Climate over China
    WANG Pengling ZHOU Bing LIU Yanju LI Qingquan WANG Dongqian
    2015, 41(4):489-496. DOI: 10.7519/j.issn.1000-0526.2015.04.012
    [Abstract](1073) [HTML](173) [PDF 1.97 M](1334)
    Based on the real time, historical observation data and NCEP/NCAR reanalysis data, anomalies of ocean and atmospheric circulation are analyzed and their impacts on climatic anomalies in 2014 over China are discussed. The results show that the intensity of East Asian winter monsoon and the Siberian high were weaker than normal during the 2013/2014 winter, with the center of polar vortex located in the Western Hemisphere, leading to the higher temperature than normal over China. While the East Asian winter monsoon exhibited intraseasonal variations, the surface air temperature over China had two stage variations last winter, warmer in the early winter and colder in late winter. It is found that a new El Ni〖AKn~D〗o event formed in the eastern and central equatorial Pacific in 2014, and significant positive phase persisted in the index of Basin Wide SSTA variation in the tropical Indian Ocean (IOBW) after March of 2014. As a response of circulations to above warm ocean conditions, the West Pacific subtropical high was stronger and extended further southward to its normal situation during summer and autumn, leading to the “more in South and less in North” feature for total precipitation over eastern China during the rainy season. In 2014, onset of the South China Sea summer monsoon was extremely later than normal, and its intensity was weaker than normal. The East Asian summer monsoon was weaker than normal, favorable for the main rain belt over the eastern China to hover southward and more precipitation in Meiyu season was seen over the Jiangnan and the middle and lower reaches of the Yangtze River while less precipitation was in most of the northern China during the summer 2014.
    13  Global Major Weather and Climate Events in 2014 and the Possible Causes
    LI Qingquan WANG Anqian ZHOU Bing LIU Yanju SUN Chenghu WANG Dongqian WANG Pengling
    2015, 41(4):497-507. DOI: 10.7519/j.issn.1000-0526.2015.04.013
    [Abstract](1371) [HTML](388) [PDF 2.75 M](1241)
    The global average surface temperature in 2014 was about 0.57 ℃ higher than the mean value of 1961-1990. The year is the warmest year on records since 1850.Sea surface temperatures (SSTs) in the eastern and central equatorial Pacific Ocean mostly maintained warm conditions. Global average SSTs in 2014 were warmer than any previous years in the historical records. During the year, sea ice extent in the Arctic was still at one of the lowest levels on records while the Antarctic sea ice extent reached a new record again. Affected by the anomalous atmospheric circulation combined with the external forcing factors of ocean and sea ice, notable climate anomalies and extreme events occurred worldwide in 2014. Especially, the precipitation in most of the southwest part of the United States of America in January-April 2014 was 20%-60% less than normal, with mean rainfall amount being the least since 1981.The drought developed and persisted, and severe drought even hit some regions. During the first and second dekads of June 2014, the average air temperature in India was 31.2℃, 1.2℃ higher than normal. The temperature in some locations was even above 4℃ higher than normal, which is recorded as the highest temperature in the corresponding period since 1961. The maximum temperature was 47.8℃ in New Delhi of India on 8 June, creading a new record in the city for the past 62 years. Further analysis results show the continual domination of the ridge in the upper troposphere and the severe shortage of water vapor transportation from the Northeast Pacific and the Gulf of Mexico were the immediate causes for the drought in the southwestern part of the United States from January to April. The slow northward advances of Indian summer monsoon and the sustainable control of high ridge were the major causes for the high temperature in India in June 2014.
    14  Causality Analysis of Autumn Rainfall Anomalies in West China 2014
    SI Dong SHAO Xie SUN Leng WANG Qiyi LI Duo
    2015, 41(4):508-513. DOI: 10.7519/j.issn.1000-0526.2015.04.014
    [Abstract](1390) [HTML](104) [PDF 6.49 M](1243)
    During the autumn of 2014, mean precipitation over China was above normal, especially in West China with strong intraseasonal variations. Analysis shows that the positive precipitation anomaly over West China is possibly caused by the warming over the tropical Indian Ocean. The warming of the tropical Indian Ocean enhances the low level anticyclonic anomaly over the Northwest Pacific and southeast water vapor transportation to West China, and also intensifies the convectional activity over Indian Ocean and southwest water vapor transportation to West China. At the mid high latitude, abnormal trough maintains over the Lake Baikal, which is prone to guide the cold air down to West China. At the same time, the intensified western Pacific subtropical high (WPSH), whose high ridge extends more westward, also brings more water vapor from the low latitude to West China. As a result, the intensified water vapor and the northwestward cold air flow leads to the positive precipitation anomaly over West China during autumn of 2014. Furthermore, the intraseasonal variation of the autumn precipitation over West China is influenced by the WPSH.
    15  Analysis of the January 2015 Atmospheric Circulation and Weather
    YIN Shan HE Lifu
    2015, 41(4):514-520. DOI: 10.7519/j.issn.1000-0526.2015.04.015
    [Abstract](1443) [HTML](93) [PDF 11.01 M](1342)
    The main characteristics of general atmospheric circulation in January 2015 are as follows: There were two polar vortex centers in the Northern Hemisphere with weaker strength than normal years. The circulation in Eurasian mid high latitudes showed a three wave pattern and mainly performed in zonal circulation. The strength of Western Pacific subtropical high and the south branch trough were near climatological normal. The monthly mean temperature was (-3.1℃) higher than normal (-5.0℃) by 1.9℃, which is the highest in record since 1961. The monthly mean precipitation was up to 14.4 mm, 9.1% more than normal (13.2 mm). However, the distribution of precipitation was quite uneven during the study period. The amount was more than normal in Southwest China, Northwest China and the south of South China. In contrast, it was significantly less than normal from North China to Jiangnan Region and there was almost no precipitation in Beijing and some other places. There was only one cold air process nationwide in this month which occurred in the first dekad, while five rainfall processes happened during the same time. At the late stage of first dekad, record breaking heavy rain and snow event occurred in Yunnan Province and the meteorological drought was significantly alleviated. At the end of this month, large scale cryogenic rain and snow weather dominated the central and eastern part of China, which was the first time since this winter, and freezing rain was seen in Guizhou Province. Meanwhile, three wide range fog and haze processes occurred in the central and eastern part of China.

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