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28 December 2018, Volume 37 Issue 6   
  • Construction and Applications of Time Series of Monthly Precipitation at Weather Stations in the Central and Eastern Qinghai-Tibetan Plateau
  • LIU Tian;YANG Kun;QIN Jun;TIAN Fuqiang
  • 2018 Vol. 37 (6): 1449-1457.  DOI:10.7522/j.issn.1000-0534.2018.00060
  • Abstract ( ) HTML PDF (6519KB) ( )
  • Weather stations can provide high-accuracy local precipitation information, but individual stations usually have different time series, which may have a significant influence on the precipitation trend analysis and relevant studies. This impact may be particularly severe in the Qinghai-Tibetan Plateau, where the stations are very sparse and are hard for operations. The number of available China Meteorological Administration (CMA) stations decreased from 146 to 130 in the central and eastern Qinghai-Tibetan Plateau during 1979—2015, mainly due to the deactivation of some stations and the change of station types. In this study, an upscaling theory method based on the Bayesian linear regression was used to establish the mathematical relationship for precipitation value between a station with missing data and its adjacent stations with available data. The method is then used to interpolate and extend the monthly precipitation time series. It was constructed the time series of monthly precipitation at 148 stations in the central and eastern Qinghai-Tibetan Plateau and its surrounding areas during the period of 1979-2015. Cross-validation, using 29 time series complete stations, displays the constructed time series after interpolation and extension can generally restore the seasonal variation of the precipitation at stations with missing data. The new method is superior to several commonly used interpolation methods to a certain extent, including inverse distance weighted (IDW), local polynomial (LP), and kriging method. To illustrate the value of reconstructed precipitation data, two preliminary applications of the data were introduced, including satellite precipitation correction and regional precipitation trend analysis. The fusion of satellite precipitation (Tropical Rainfall Measurement Mission, TRMM) and gauge precipitation after interpolation and extension, indicates that the introduction of interpolation stations data can change the local precipitation distribution characteristics. To a certain extent, increasing the number of available stations helps to improve interpolation accuracy of grid precipitation. The interpolation and extension are helpful to quantify the spatial distribution and the temporal variation of precipitation in central and eastern Qinghai-Tibetan Plateau. Improving the precipitation grid interpolation accuracy in particular, the constructed time series then demonstrates that annual precipitation decreased significantly in the Southeast Qinghai-Tibetan Plateau after about 1998 but jumped slightly to a higher-level in the Northeast Qinghai-Tibetan Plateau since 2002, while no decadal change is seen in the transitional zone between the Southeast and Northeast Qinghai-Tibetan Plateau. This spatial difference in precipitation can roughly explain the spatial pattern of regional water cycles (glacier mass balances, lake water volume changes, and river runoff changes).
  • Climatic Characteristics of Surface Radiation Flux over the Qinghai-Tibetan Plateau
  • GU Xingyue;MA Yaoming;MA Weiqiang;SUN Fanglin
  • 2018 Vol. 37 (6): 1458-1469.  DOI:10.7522/j.issn.1000-0534.2018.00051
  • Abstract ( ) HTML PDF (1236KB) ( )
  • In this paper, we used observational radiation data from the Amdo Center Station (The following is the Amdo Station, with 19 years of surface radiation observations), BJ Station (with 17 years of surface radiation observations), D105 Station (with 17 years of surface radiation observations) and NPAM (Also known as the MS3478 Site, with 17 years of surface radiation observations) Station on the Northern Qinghai-Tibetan Plateau in the GAME/Tibet[GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Qinghai-Tibetan Plateau] and the CAMP/Tibet[CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Qinghai-Tibetan Plateau], and the Qomolangma Station for Atmosphere and Environment Observation and Research of the Chinese Academy of Sciences (The following is the Qomolangma Station, with 12 years of surface radiation observations) and Nam Co Station for Multisphere Observation and Research of the Chinese Academy of Sciences (The following is the Nam Co Station, with 12 years of surface radiation observations). There are about 10 to 20 years of observational radiation data, calculated the daily average value at 10:00 to 18:00 on sunny days, and counted monthly average value. Finally, use these average value to find out the annual average value of observational surface radiation fluxes (short wave downward radiation, short wave upward radiation, long wave downward radiation, long wave upward radiation, net radiation flux and albedo) from the above sites. Based on the analysis of the annual variations of short wave downward radiation, short wave upward radiation, long wave upward radiation, long wave downward radiation, net radiation and albedo of the typical underlying surface (plateau meadows with a height of 5 cm, plateau meadows with a height of 10 cm, sparse plateau meadows, plateau meadows with a height of 15 cm, gobi, and plateau meadows near the lake), the long-term climate change characteristics of surface radiation fluxes of the Qinghai-Tibetan Plateau were obtained. It was found that the short wave downward radiation flux at most sites on the Qinghai-Tibetan Plateau has a decreasing trend of varying degrees of annual change. Moreover, the long wave upward radiation flux by all the stations has an increasing trend of varying degrees, and the long wave downward radiation flux by all the stations has an increasing trend of varying degrees. The annual variation of the net radiation flux at most stations in the Qinghai-Tibetan Plateau region is basically consistent with the annual change in the short wave downward radiation. And the albedo at most sites on the Qinghai-Tibetan Plateau decreases year by year to varying degrees.
  • The Characteristics Analysis on the Summer Atmospheric Boundary Layer Height and Surface Heat Fluxes over the Qinghai-Tibetan Plateau
  • SU Yanru;Lü Shihua;FAN Guangzhou
  • 2018 Vol. 37 (6): 1470-1485.  DOI:10.7522/j.issn.1000-0534.2018.00040
  • Abstract ( ) HTML PDF (16359KB) ( )
  • The atmospheric boundary layer (ABL) is also known as the planetary boundary layer (PBL) which is directly influenced by its contact with the planetary surface. Surface heat fluxes usually include the sensible heat flux (SHF) and the latent heat flux (LHF), which have a great influence on the PBL. With the reanalysis data sets of planetary boundary layer height from NECP-FNL and the surface heat fluxes data from NCEP/DOE (NECP2), the temporal, spatial distribution and the variation trend of the planetary boundary layer height (PBLH), the sensible heat flux (SHF) and the latent heat flux (LHF) over the Qinghai-Tibetan Plateau have been studied with regional average. The mutation test was carried out by sliding T-test. The influence factors of boundary layer height and surface energy transport in plateau region were determined by correlation analysis and correlation coefficient test. The research time is the summer (June-August) from 2000 to 2016. The results showed that the HPBL of the whole Plateau during 2000-2016 is on the decline, the SHTFL is on the rise. The LHTFL from 2000 to 2009 is increase, but from 2009 to 2016 is decrease. The year of 2009 is the climate change time point of HPBL, at the same time the trend of other physical quantities also changed in 2009. The variation trend distributions have obvious regional differences. By the 91°E line, the plateau can be divided into two parts as the eastern and the western regions. The temporal, spatial characteristics from each part are obvious difference, and the year of 2009 is an abrupt change point of climate, also is a turning point of the annual variation tendency. The distribution of the temporal trend about the latent heat flux in the eastern and western regions is basically on the contrary between the period before and after the mutation. The impact factors of the eastern and the western region over the Qinghai-Tibetan Plateau are multiple, the main factor influenced the HPBL, SHTFL and LHTFL in the western region are the soil moisture from surface to 10 cm and the wind speed of 10 m, in contrast, the most important reason affects in the eastern region is the total cloud cover. Before and after the mutation-2009, the influence factors have big difference, for example the wind speed of 10 m has become the influence factor of surface latent heat flux in the eastern region after the abrupt climate change. The Heat Low develop in the plateau at surface layer over land and the South Asian High in the upper atmosphere, which provide the dynamic conditions for the development of the atmospheric boundary layer, it's good for the ascent. The air flow in the ascending motion can transfer the condensation latent heat released by the water vapor phase to the upper troposphere, which is beneficial to the positive feedback of latent heat flux and South Asian High.
  • Climatic Characteristics of the Diurnal Variation Boundary Layer Height over the Qinghai-Tibetan Plateau Based on CERA-20C
  • WANG Qianru;FAN Guangzhou;GE Fei;CHENG Yixuan;ZHU Yi
  • 2018 Vol. 37 (6): 1486-1498.  DOI:10.7522/j.issn.1000-0534.2018.00042
  • Abstract ( ) HTML PDF (35043KB) ( )
  • Based on the CERA-20C global atmospheric boundary layer height (BLH) reanalysis data from 1981 to 2010, this paper focused on the diurnal variation characteristics of the BLH data, including seasonal variation, chronological change and interannual variation of the Qinghai-Tibetan Plateau. The statistic showed that the BLH large value areas include areas above 5 000 m and some desert areas, Nyima is the source of the high-value area in boundary layer. BLH increases most dramatic from 03:00 (UTC, the same as after) to 06:00 and decreases from 09:00 to 12:00, the increase of the BLH can reach 948.67 m·(3h)-1 with a decrease of 760.02 m·(3h)-1, and reaching to the maximum value at 09:00. This is a bit later than the non-plateau area whose maximum time is 06:00. The average maximum value during thirty years can reach to 1982.764 m, and the maximum daily variation is up to 2901.21 m, both manifesting a high volume during the day and low volume at night. The maximum value of BLH is the largest in spring while the smallest in summer, but the minimum of BLH lies in summer and the smallest in autumn. The BLH of Plateau West Slope reaches a maximum in spring and autumn, but in hinterland it's in winter. The BLH of Plateau East Slope is quite low and steady. At 03:00, the BLH changed monthly in a single peak characteristic. In addition to the steady change of inter-annual variability in spring, autumn and winter, the BHL of these three seasons all feature great fluctuation in the mid of 1980s, late 1990s and early 21st century. The BLH in winter has gradually increased in the past 30 years, especially in the early 21st century. In spring, the plateau hinterland of the Qinghai-Tibetan plateau above 5 000 m is in snow melting period, and the snow takes away the surface heat, making the surface temperature lower in spring. The BLH in spring is negatively correlated with the surface temperature, at the same time, the summer relative humidity is wavy distribution, and the minimum relative humidity gradient corresponds to the top of the boundary layer, and the height of boundary layer is higher in spring than in summer. When the boundary layer is highly developed, the elevation boundary and the subsidence movement are usually alternately in the plateau boundary layer, which provides some dynamic conditions for the development of the boundary layer.
  • Model Estimation and Validation of the Surface Energy Fluxes at Typical Underlying Surfaces over the Qinghai-Tibetan Plateau
  • HU Yuanyuan;ZHONG Lei;MA Yaoming;ZOU Mijun;HUANG Ziyu;XU Kepiao;FENG Lu
  • 2018 Vol. 37 (6): 1499-1510.  DOI:10.7522/j.issn.1000-0534.2018.00045
  • Abstract ( ) HTML PDF (5707KB) ( )
  • The surface energy fluxes occur near the ground and are pivotal parameters for studying land-atmosphere interaction. The Qinghai-Tibetan Plateau is one of the most sensitive regions in response to global climate change. Its thermal and dynamic effects on the atmosphere are mainly achieved through the exchange of heat and water vapor between the land surface and the atmosphere. The estimation and validation of the surface energy fluxes over the Tibetan Plateau have great significance on the study of energy and water cycle in the Qinghai-Tibetan Plateau and its surrounding regions. The surface energy balance system (SEBS) model provides an effective method for studying the surface energy fluxes over the heterogeneous underlying surface. In order to further explore applicability of the model estimation for the typical underlying surface over the Tibetan Plateau, based on in-situ radiation data and Atmospheric Boundary Layer (ABL) tower data (Nagqu Station of Plateau Climate and Environment (BJ), Nam Co Station for Multisphere Observation and Research (Nam Co) and Qomolangma Station for Atmospheric Environmental Observation and Research (QOMS), Chinese Academy of Sciences (CAS)) and combined with MODIS data in 2008, the SEBS model was used to estimate the surface energy fluxes which were validated with the in-situ measurements. The results showed that the sensible heat flux and soil heat flux estimated by the model were in good agreement with the in-situ measurements, and the estimation accuracy of sensible heat flux and soil heat flux was obviously better than that of latent heat flux. The estimation accuracy of the sensible heat flux was the highest, and their root mean square error (stations BJ, Nam Co and QOMS) were 54.98 W·m-2, 37.37 W·m-2, 27.10 W·m-2, respectively. The error of the latent heat flux of the model estimated is relatively large, which is caused by the energy closure problem in the in-situ measurements. Taking the imbalance of energy closure prevails in most surface energy fluxes measurements into account, the latent heat flux measurements were corrected by using the Bowen ratio correction method. Results showed that the Bowen ratio correction method could significantly improve the energy imbalance problem. The closure ratios of surface energy balance (stations BJ, Nam Co and QOMS) were increased by 19.4%、21.4%、19.1%, respectively. Accordingly, the corrected latent heat flux had better consistency with model estimation results. The root mean square error of estimated latent heat flux decreased by 6.78 W·m-2(BJ), 33.48 W·m-2(Nam Co), 29.30 W·m-2(QOMS), respectively.
  • Analysis on Moving Characteristics and Thermodynamic Causes of MCC over Eastern Qinghai-Tibetan Plateau in Rainy Season
  • Lü Yiying;YIN Yan;CHEN Jinghua;KUANG Xiang;HAO Jian;ZHANG Xin
  • 2018 Vol. 37 (6): 1511-1527.  DOI:10.7522/j.issn.1000-0534.2018.00056
  • Abstract ( ) HTML PDF (42547KB) ( )
  • Based on the TBB data from Fengyun-2 stationary meteorological satellite and the reanalysis data ERA_Interim from ECMWF from May to September during 2012-2016, we conducted a contrastive analysis on the moving characteristics of mesoscale convective complex(MCC) over Qinghai-Tibetan Plateau(QTP) in rainy season. The results showed that MCC over the QTP can be divided into three types according to its moving characteristics, which are MCC that move out of the QTP in northeast direction(NE-MCC) and in east direction (E-MCC) and decay locally over the QTP(L-MCC). NE-MCC are usually born in the middle of the QTP while E-MCC and L-MCC are in the southern slope of the QTP. Generally, MCC that can move out of the QTP are not that strong due to its location and lifespan, while MCC that with moderate convective intensity and longer lifespan shows obvious eastward or north-eastward moving feature. Compared with NE-MCC and E-MCC, L-MCC is with the smallest cloud cover, the strongest TBB, the highest IWC and LWC and the maximum divergence difference between two levels that can lead to intense updrafts to enhance the development of L-MCC and at the same time forming a positive feedback mechanism. Compared with E-MCC, NE-MCC have longer lifetime and located in the lower relative humidity place. At the height of 500 hPa, the movement of NE-MCC is affected by the southwest airflow from the cyclonic circulation while E-MCC is affected by the westerly air flow at the bottom of the shortwave trough and L-MCC is located in the cyclonic circulation. The three types of MCC are located at the high temperature center or nearby, which may be derived from the contribution of the summer plateau heat source. It is beneficial for the development of MCC if the environmental configuration field has been convergence and positive vorticity in the low level coupled with divergence and negative vorticity or its gradient in the high level. The divergence gradient direction in the vertical section of the system center shows the movement trend of the system. The effect of topography prevents the L-MCC from moving north.
  • Study on the Climate Characteristics of Precipitation in Emei Mountain and Its Surrounding Area
  • Lü Jing;LI Zhongxian;LI Yueqing;ZOU Bingjun;JIANG Nan;LI Xuefeng
  • 2018 Vol. 37 (6): 1544-1562.  DOI:10.7522/j.issn.1000-0534.2018.00049
  • Abstract ( ) HTML PDF (4689KB) ( )
  • Based on the daily precipitation data of Emei Mountain, Emei City, Leshan City and Jiajiang County meteorological stations from 1959 to 2016 and their hourly precipitation data during June-September from 1964 to 2016, the multiple time scale variation characteristics of the amount of precipitation, rain days and precipitation frequency in Emei Mountain and its surrounding area were studied by statistical analysis and diagnosis methods. The result shows that the decadal precipitation and rain days decrease in Emei Mountain and its surrounding area in the past few decades, and the decrease degree of high-altitude Emei Mountain is stronger than that of low-altitude surrounding area. The annual precipitation and annual rain days decrease significantly in Emei Mountain and its surrounding area after the 1990s, and the annual rain days in Emei Mountain decreases faster. In flood season, the variations of amount of precipitation and rain days in Emei Mountain and its surrounding area are stronger than their interdecadal and interannual variations, and it is more prominent than the other periods. Except in spring, the precipitation in high-altitude Emei Mountain in other three seasons reduces significantly, and it obviously reduces in summer and autumn in low-altitude surrounding area. The decrease of rain days in all seasons is more obvious in Emei Mountain than in its surrounding area. The reduction of monthly precipitation and rain days in Emei Mountain is more obvious that that in its surrounding area. The diurnal variation of precipitation in high-altitude Emei Mountain has single-peaked and single-valley distribution, but the second peak appears in the morning in low-altitude Emei City. The precipitation of Emei Mountain and its surrounding area is much larger in the night than that in the daytime. The peak time of precipitation in Emei Mountain and Emei City occurs earlier than before. The time of maximum hourly precipitation frequency has significantly advancing feature in Emei Mountain. But Emei City has the variation of being delayed. Under the global warming, the precipitation in Emei Mountain and its surrounding area significantly decreases, especially in Emei Mountain. The consistency and difference of regional climate response in Emei Mountain and its surrounding area may be related to regional temperature responses and water vapor conditions.
  • The Synergy between the East Asian Summer Monsoon and the South Asian Summer Monsoon and Its Relations with Anomalous Rainfall in Southern China
  • HUAN Yu;LI Yueqing
  • 2018 Vol. 37 (6): 1563-1577.  DOI:10.7522/j.issn.1000-0534.2018.00044
  • Abstract ( ) HTML PDF (41877KB) ( )
  • Using the precipitation data in China and the reanalysis data from European Centre for Medium-Range Weather Forecasts (ECMWF) during the period of 1979-2014, the index for the interface between the East Asian summer monsoon and the Indian summer monsoon (ⅡEI) was calculated, and the interannual variation of ⅡEI, the feature of its positive-anomaly and negative-anomaly years, as well as the relations between ⅡEI and China's regional precipitation were also analyzed on the basis of the comparison of ⅡEI and the indices of East Asian summer monsoon and the Indian summer monsoon by Empirical Orthogonal Function (EOF), correlation analysis, wavelet analysis, composite analysis and differential analysis. The results showed that the ⅡEI has positive correlation with the index of East Asian summer monsoon and negative correlation with the Indian summer monsoon. Meanwhile, there are negative correlation between ⅡEI and precipitation in most of the southern China. In the positive-anomaly years of ⅡEI, the East Asian summer monsoon is stronger than Indian summer monsoon, the intensity of South Asian high is weaker and its position is both by south and by west, and the intensity of West Pacific subtropical high is weaker and the location is both by east and by north. The south China is controlled by the northeastern winds. And it is the northerly wind at the low level of the South China Sea that inhibits the transport of water vapor to the southern China. The sinking movement results in the less precipitation in most southern China and causes drought easily. In negative-anomaly years of ⅡEI, the East Asian monsoon is weaker than the South Asian monsoon. The intensity of South Asian high is stronger and its position is by east, and the strength of the West Pacific subtropical high is stronger and its position is both by west and by south. The southern China is controlled by the southwest wind. And it is the southerly wind at the low level of the South China Sea that transports the water vapor from the Arabian Sea and the Bay of Bengal to the vast areas of the southern China, and meets with the dry-cool airflow from the north. Because of the anomalous upward movement, it brings much more precipitation to the southern China and cause floods easily. Therefore, the synergistic evolution of the East Asian monsoon and the South Asian monsoon is the important reason for the anomalous precipitation in the southern China.
  • Analysis of the Characteristic of Ground-Based Microwave Radiometer Data before Convective-Cloud Precipitation
  • ZHANG Qiuchen;WANG Jun;LI Xue
  • 2018 Vol. 37 (6): 1578-1589.  DOI:10.7522/j.issn.1000-0534.2018.00098
  • Abstract ( ) HTML PDF (2510KB) ( )
  • Using brightness temperature and instability indices, such like K Index (KI), Lifting Index (LI), Showalter Index (SI), Total Total Index (TTI) and Convective available potential energy (CAPE) from14-channel ground-based microwave radiometer named RPG-HATPRO-G3, variation tendency before 9 convective-cloud precipitation events in 2015-2016 were analyzed, and compared with which in non-precipitation days. The results showed that in non-precipitation days, brightness temperature at 22 GHz and 58 GHz and 5 instability indices exhibited diurnal variation, and the variation of brightness temperature at 22 GHz was more apparent than that of 58 GHz. The diurnal variation difference of 5 instability indices was larger in summer and autumn than that in winter and spring. Continuous increase of brightness temperature at 22 GHz was observed 34 minutes before the beginning of 9 convective-cloud precipitation events, and the duration of increasing was earlier than continuous decline of brightness temperature at 58 GHz. Moreover, the value and the diurnal variation difference of brightness temperature at 22 GHz were larger than those in non-precipitation days of all four seasons that means brightness temperature at 22 GHz was more indicative than brightness temperature at 58 GHz for the beginning of convective-cloud precipitation events. KI, TTI and CPAE were observed to continuous increase, and the values were larger than mean values in non-precipitation days of all four seasons. On the contrary, LI and SI observed to continuous decline, and the values were smaller than mean values in in non-precipitation days of all four seasons. The value of 5 instability indices can provide references for the threshold of the beginning of convective-cloud precipitation. KI, TTI, LI and SI change duration was observed about 40 minutes before the beginning of convective-cloud precipitation, which was earlier than that of CPAE. The range of brightness temperature at 22 GHz time rate of change was in -1.12~1.12 K·s-1 1 h before 9 convective-cloud precipitation events, and the percentage of which lager than 0.28 K·s-1 gradually increased with being close to the precipitation. It was also noticed that the proportion of large negative time rate in -10~0 min was also higher than that of other periods. In -10~0 min, KI, SI and CPAE time rate of change were in the range of 0.025~0.05 K·s-1, -0.04~0.02 and -12~12 J·kg-1·s-1 respectively. The percentage of the largest KI time rate of change was larger in -10~0 min than that in other time, the same phenomenon could be found in SI and CPAE. But the percentage of largest KI and SI time rate of change were larger than that of CPAE. Considering the time of continuous increase and largest time rate of change, KI and SI were more indicative than CPAE.
  • Spatiotemporal Distribution and Trend of Cloud Water Content in China Based on ERA-Interim Reanalysis
  • LIU Juju;YOU Qinglong;ZHOU Yuquan;MA Qianrong;CAI Miao
  • 2018 Vol. 37 (6): 1590-1604.  DOI:10.7522/j.issn.1000-0534.2018.00059
  • Abstract ( ) HTML PDF (31170KB) ( )
  • Based on the next-generation global resolution ERA-Interim reanalysis data released by the European Centre for Medium-Range Weather Forecasts (ECMWF), the spatial and temporal distribution characteristics of cloud water (The general designation of cloud water content, cloud liquid water content, and cloud ice water content) in China from 1979 to 2016 have been analyzed by applying the methods of nine-point smoothing and one-dimensional linear regression. The results were shown as follows:(1) Cloud liquid water content and cloud water content in China are mainly located in the eastern part of Sichuan-Hunan, located at 850~500 hPa in the vertical direction, with the amount of 0.015~0.045 g·kg-1. This distribution is closely related to the enrichment of stratus over the area. The large value of cloud ice water content is mainly located in the middle and eastern part of China (27°N-35°N, 97°E-110°E), located at 500~250 hPa in the vertical direction, with the amount of 0.006~0.025 g·kg-1. The small values are all located in the western part of the Northwest China. (2)There is no obvious annual trend of the vertical integral of cloud water in China. The seasonal average cloud water in spring is slightly decreased, and the cloud water is increased slightly in autumn and winter. There is no obvious cloud water trend in summer. In addition, cloud water content in China has obvious interannual variation characteristics, with smallest variation in summer. The interannual variability of cloud liquid water content in arid and semiarid regions is greater than that in wet regions. In contrast, the interannual variability of cloud ice water content in arid and semiarid regions is less than that in wet regions. The spatial variation of cloud water is increased in the west of China and decreased in the east of China. (3) The more cloud liquid water content and cloud ice water content are corresponded to stronger water vapor convergence and an uplift motion in the lower layer. This indicates that the water vapor flux divergence in the middle and lower troposphere can characterize the value of cloud water content. This study aims to provide a basis for understanding the impact of climate change on water resources in China.
  • Analysis of the Causes of one Sustained Enter-the-Sea Plateau Vortex Accompanied by Southwest Vortex
  • XIAO Yuhua;YU Shuhua;GAO Wenliang;XIAO Dixiang;XIAO Hongru;SHI Ri
  • 2018 Vol. 37 (6): 1616-1627.  DOI:10.7522/j.issn.1000-0534.2018.00043
  • Abstract ( ) HTML PDF (11307KB) ( )
  • Based on NCEP/NCAR reanalysis data, history synoptic chart and the Plateau Vortex and Shear Line Yearbook, by using synoptic analysis and diagnose method, an enter-the-sea Plateau Vortex (Qumalai vortex, named from its generation site) accompanied by a Southwest Vortex during 410 June 2013, was studied in terms of the vorticity, nonadiabatic heating and potential vorticity. In order to reveal the cause that why Qumalai Vortex can move eastward far away till onto the sea and sustain for 6 days, the function of downward spread of larger vorticity and potential vorticity from the upper air jet, nonadiabatic heating during the different life phases of Qumalai Vortex were studied, as well as the influence of encountering Southwest Vortex on Qumalai Vortex's maintenance and development. The results showed that the location and the intensity change of the upper air jet were of great importance for Qumalai Vortex to move eastward and maintain. Apart from leading Qumalai Vortex movement, as taking along larger vorticity and potential vorticity, the upper air jet provided Qumalai Vortex with vorticity and potential vorticity by way of downward spread, which gave support to Qumalai Vortex in energy continually. As Qumalai Vortex about to the sea, although the upper air jet just above Qumalai Vortex was disconnected, a trough was generated there. The downward spread of plentiful vorticity and potential vorticity in the trough into Qumalai Vortex enabled Qumalai Vortex to develop intensively, while encountering even overlapping with the Southwest Vortex made Qumalai Vortex stepping in a period of its great prosperity. Once Qumalai Vortex lost the support from the upper air, it decayed and died out soon. Unlike Qumalai Vortex, Southwest Vortex, even if without the aid of larger vorticity and potential vorticity from upper air, could still be strongly powerful and prosperous on account of nonadiabatic heating. Furthermore, the contrastive analysis of apparent heat source in their each life phase between Qumalai and Southwest Vortexes was conducted. The results indicated that over the first stage of formation, nonadiabatic heating was important for both Qumalai and Southwest Vortexes in the same way that heat was transported upward, resulting in the nonadiabatic heating profile of "bulging towards the right" which was very in favor of vorticity increase. Later, the function of nonadiabatic heating was little for Qumalai Vortex, but still crucial for Southwest Vortex. Nonadiabatic heating decided not only the length of Southwest Vortex life, but also the highest level of intensity.
  • The Developmental Characteristics of the Structure of a Stationery Cold Southwest Vortex
  • CHEN Guichuan;SHEN Yun;WANG Xiaofang;ZHU Yan;LI Qiang;ZHANG Yong
  • 2018 Vol. 37 (6): 1628-1642.  DOI:10.7522/j.issn.1000-0534.2018.00093
  • Abstract ( ) HTML PDF (52856KB) ( )
  • By using data from conventional soundings and surface observation, NCEP reanalysis, radar, satellite and regional automatic stations, an incessant heavy rainstorm from 16 to 18 August 2015 in Sichuan Basin was systematically analyzed. The results showed that being blocked by the West Pacific Subtropical High (WPSH), the positive vorticity advection to the eastern side of the plateau vortex and the northwestern side of the WPSH provide the dynamic conditions for the Southwest Vortex(SV), the front temperature trough superimposed on the middle and low warm shallow synoptic systems strengthens the convective instability, the cold air invading slowly results in the stationery cold SV sustainable development. The precipitation in SV is enhanced by condensation latent heat release. In the maturation stage of SV, the vertical positive vorticity column at all levels is almost vertically coupled. The horizontal flow pattern approximately forms as a circle, while the temperature, moisture and energy fields at 700 hPa asymmetrically shape as "S". It is beneficial to maintain the heat and moisture transport mechanism to the northeast region of Chongqing at lower level, which is a crucial factor explaining why horizontal precipitation is stronger than that of meridian. Located in the basin area, the precipitation results from the stable development of central MCSs twice, clustering to the southern side of the warm shear of the SV, near the stationery front on the surface. In contrast, meridian precipitation is the outcome of MCSs triggered by cold front twice, located ahead of the trough of SV. The life history of MCSs could be divided into eight stages. With the maintenance of dynamic pump, the MCSs to the southern side of SV inhibits the evolution of central MCSs by influencing vapor transfer, resulting in the "see-saw" feature of the development of precipitation to the northeast and southeast of SV.
  • The Impact of the Thermal Differences over the East Asian and the Pacific Ocean on East Asian Monsoon
  • XU Tiantian;FAN Guangzhou;ZHANG Yongli;LAI Xin;WANG Bingyun
  • 2018 Vol. 37 (6): 1643-1654.  DOI:10.7522/j.issn.1000-0534.2018.00053
  • Abstract ( ) HTML PDF (19435KB) ( )
  • By using NCEP/NCAR monthly and daily reanalysis data from 1951 to 2014 and the data of Climate Prediction Center Merged Analysis of Precipitation(CMAP) from 1979 to 2014, the thermal contrast over the key regions and the thermal differences over these areas in summer were analyzed, using synthetic analysis to discuss the impact of thermal conversion over the key regions on the onset of the East Asian subtropical monsoon, and the impact of thermal difference on the intensity of the East Asian subtropical monsoon. The conclusions were summarized as follows:When the time of thermal conversion between East Asian and Western Pacific Ocean is early(late), the onset time of East Asian subtropical monsoon is early(late), the retreat time of the East Asian subtropical monsoon is late(early), the duration of East Asian subtropical monsoon is long(short), and the onset time of tropical monsoon is late(early). The onset time of East Asian subtropical monsoon and the time of thermal conversion between East Asian and Western Pacific Ocean are consistent. And the onset of the tropical monsoon can promote the intensity of the East Asian subtropical monsoon. The thermal effect of the Qinghai-Tibetan Plateau has more impacts on East Asian subtropical monsoon than tropical monsoon. When the thermal difference between continent and ocean is bigger(smaller), the position of the subtropical ridge is southward(northward), the wind is southern(northern) anomaly at the East Asian subtropical region, the wind is westerly(easterly) anomaly at low latitude, the ascending motion at the Qinghai-Tibetan Plateau and the East Asian continent is stronger(weaker) than average state, the ascending motion at the Western Pacific Ocean is weaker(stronger) than average state. Moreover, when the thermal difference is bigger, the northwest wind from north area and the south wind from Western Pacific Ocean meet at the subtropical areas about 30°N have positive effect on the precipitation in this area. The thermal difference between East Asian including the Qinghai-Tibetan Plateau and the Western Pacific Ocean has more influence on height field, wind field and vertical velocity field than the thermal difference between East Asian excluding the Qinghai-Tibetan Plateau and the Western Pacific Ocean. The thermal difference in summer has influence on the distribution of temperature and precipitation in China.
  • Comparative Analysis of Abnormal Relationship between Two Types of Decadal Characteristics of Extreme Low Temperature in Spring and the Eurasian Circulation
  • XU Weiping;ZHANG Jie;CHEN Zhiheng
  • 2018 Vol. 37 (6): 1655-1670.  DOI:10.7522/j.issn.1000-0534.2018.00058
  • Abstract ( ) HTML PDF (17489KB) ( )
  • Based on daily temperature data from 501 stations in northern China, the reanalyze data from European Centre for Medium-Range Weather Forecasts (ECMWF) and the sea temperature data from Hadley Center (Hadley), this paper investigated the temporal and spatial characteristics of extreme low temperature in spring in North China and compared the characteristics of atmospheric abnormal circulation between the two types of decadal extreme low temperature in the around 1980s and the 21st century. The results indicated that the situation of extreme low temperature circulation in 21st century presents a "quasi-2-wave" structure from the North Atlantic to Eurasia, with longer wavelength, better stability, longer duration at low temperature, and obvious wave trains structure at mid-high latitudes; However, the extreme low temperature circulation in the around 1980s presents a "3-wave" structure, with shorter wavelength, poorer stability, shorter duration at low temperature, and less obvious wave trains structure at mid-high latitudes. The North Atlantic sea surface temperature has a significant turning point in 1997. Before 1997, the energy of the North Atlantic near the south of Greenland was propagated eastwards, and the Eurasian wave train (EU) was excited through the key West Siberia area. The cyclonic abnormal circulation was enhanced, which was conductive to the maintenance and development of low temperature. There may be two sources of energy dispersion reason, making the EU wavelength of the 1980s shorter than the 21st century. However, after 1997, the ocean surface east of Greenland became the key forcing source. The energy propagated to the east is in favor of EU strengthening. The trough in southwestern part of Lake Baikal was strengthened to form a cyclonic abnormal center, which was conductive to the maintenance of low temperature. On the eastern side of Greenland, the sea surface temperature anomalies thermal forcing can stimulate EU teleconnection, form warm ridges on the downstream Eurasian continent, strengthen to the north and then contract with the Okhotsk Sea ridge directly, resulting in a Cyclone anomaly to strengthen and the circulation prone to maintain stability, making the North China temperature drop, prone to extreme low temperature events. The results reflect the interdecadal characteristics of extreme low temperatures in North China and some causes of the abnormal of the two types of extreme low temperature circulation, to extract certain signal for predicting extreme low temperature events.
  • Analysis of Mesoscale Feature of a Heavy Rainstorm Caused by Typhoon Residual Vortex in the Northern Part of Northeast China
  • REN Li;ZHAO Ling;MA Guozhong;LIN Jia'nan
  • 2018 Vol. 37 (6): 1671-1683.  DOI:10.7522/j.issn.1000-0534.2018.00036
  • Abstract ( ) HTML PDF (15493KB) ( )
  • Based on the conventional observational data, satellite cloud images, radar echo data, automatic weather stations rainfall and NCEP/NCAR reanalysis data (0.25°×0.25°), the mesoscale features of a heavy rainstorm by the residual circulation of Typhoon Haitang in the northern part of Northeast China from 3 to 4 August 2017 were analyzed. The major conclusions were as follow:The residual circulation of typhoon had been strengthened again after it was moved into Northeast China. The negative pressure center on the ground was located at the inverted trough shear on the north side of the cyclone. The rapid development of cyclone and the enhancement of the convergence of the variable pressure wind resulted in the lower level convergence and heavy rains. The zonal distribution in the rainstorm area showed a tendency to increase northward, and there were obvious mesoscale features in the space-time distribution. Precipitation had the characteristics of strong intensity, sudden strength and short duration. The rainstorm zone was linear, with a horizontal width of 50 km and a length of 300 km, which had typical characteristics of the mesoscale-β. The sounding analysis showed that the atmosphere was in an unstable state, which was advantageous to the convection development with short time heavy rainfall. Heavy rains were caused by the mesoscale convection systems (MCS) activities. Each time the heavy precipitation was corresponding to the black body temperature (TBB) low value center, and the delay was about 1 h. In the process of convective cloud spreading from south to north, heavy rain occurred mainly in the area of cold cloud area or the TBB gradient at the posterior edge of the cloud cluster. The backward propagation of radar echo caused the strong echo activity in the rainstorm zone, and the precipitation lasted for a long time. Heavy precipitation was a warm cloud precipitation which led to high precipitation efficiency and strong rainfall. The mesoscale convective system which caused torrential rain, had a deep vertical motion. The deep vertical motion strengthened the lower layer heat and water vapor transmission. The positive vortex column of middle and lower level was enhanced rapidly, and the water vapor convergence was enhanced, which strengthened the development and duration of mesoscale convective systems. The middle and upper layer had dry air activity, which not only triggered convection, but also greatly reduced the atmospheric stability and provided favorable conditions for the occurrence and development of convection.
  • Study on the Causes for a Typhoon Torrential Rain over the East Coast of Shandong Peninsular
  • LIU Yichen;ZHOU Weican;CHANG Yu;QU Xuebin
  • 2018 Vol. 37 (6): 1684-1695.  DOI:10.7522/j.issn.1000-0534.2018.00113
  • Abstract ( ) HTML PDF (28732KB) ( )
  • As one of the regions with high frequent typhoon and heavy rain in China, Shandong Peninsula annually has July, August and September as its peak season of typhoons. Based on the data from the NCEP reanalysis (1°×1°), the FY-2E satellite cloud pictures and the data from 123 automatic meteorological stations in Shandong province, the rainstorm process of Typhoon "Chan-hom" over the east coast of Shandong Peninsula in mid July 2015 is analyzed. The research shows that the high latitude circulation interaction with typhoon circulation is the main cause of the typhoon heavy rain. To be specific, after the dry cold air in the east upper trough of high latitudes meets the warm humid air outside the west of the typhoon over the Shandong Peninsula, the surface cold pressure field there comes across a cold front invasion, resulting in favorable synoptic-scale atmospheric circulation conditions for the rainstorm over the east coast of the Peninsula. In the early period of precipitation, the water vapor source is abundant, but its transportation condition is poor. This condition improves with typhoon circulation, and so makes it possible to maintain heavy precipitation in the rainfall area. In the course of Typhoon Chan-hom moving northward, high energy tongue extends to the north and interacts with the dry and cold air in the north, leading to a large pseudo-equivalent potential temperature gradient. This large gradient area just covers the east side of the coastline of the Shandong Peninsula, which favors the generation of heavy rain. Moreover, the high and low air jet coupling as a strong dynamic condition accounts for the rainstorm occurrence. Moreover, on the north of the typhoon the convective cloud with its TBB under -40℃ develops but maintains for a long time, and the wind speed pulsates in the low-level jet. These phenomenon are crucial causes for the continuous heavy rainfall during the storm. Another reason for this heavy rain fall lies in the friction convergence caused by the sea-land difference on the east coast of the Peninsula. In this paper, the cases of typhoon "Muifa" No. 9 in 2011 and typhoon "Matmo" No. 10 in 2014 were compared with the case of typhoon "Chan-hom". Based on the study of rainstorm cases, it can be concluded that the coupling area of upper and lower-level jets can assist in predicting whether the heavy rainfall area is on the left front or the right front in the typhoon moving direction.
  • Characteristics of the First Rainstorm Happened in Warm Area in Shandong Province in 2017
  • ZHANG Qin;WANG Hongming;ZHANG Xiuzhen;YUAN Jing;WANG Shanfang;ZHOU Shuhua
  • 2018 Vol. 37 (6): 1696-1704.  DOI:10.7522/j.issn.1000-0534.2018.00052
  • Abstract ( ) HTML PDF (15199KB) ( )
  • Using the conventional meteorological observation data, the sounding data, NCEP 1°×1° reanalysis data and the satellite data, The large-scale circulation background, vertical structural features and triggering mechanism of the first rainstorm rainstorm in Shandong rainy season from 6-7 July 2017 were analyzed. The results showed that:This warm-season rainstorm process is that the westerly belt system on the northwestern side of the subtropical high interacts with the warm-humid southwest flow from low latitudes, and is accompanied by the advantageous background of low-altitude and ultra-low-altitude south-west winds, shear lines and thermal low ground pressure. During the heavy rains, the atmosphere was in a truly unstable state, with deep wet and warm clouds, low cloud heights, and high precipitation efficiency. The torrential rain also experienced a process of vertical wind shear changed from weak to strong. The rapid strengthening and downward propagation of the southwest wind stream in the lower troposphere triggers the release of unstable energy, which provides trigger conditions for the occurrence of heavy rainfall. High-level westerly jet stream provides a strong "suction" effect, forming a strong upward movement. The top of the cloud-blackbody bright temperature (TBB) zone corresponds to heavy precipitation. Water vapor and infrared cloud images can effectively reveal the occurrence, development and demise of the weather system as well as the dynamic and vapor characteristics of the upper troposphere. The effect of warm advection on vertical movement is even more pronounced. The prediction of low-altitude and ultra-low-level jet streams can be used as a forecast point for daily warm-storm events.
  • Statistical Characteristics of the Northward Extratropical Cyclone Snowstorm Affecting Northeast China
  • FU Liang;ZHAO Yu;YANG Chengfang;ZHAO Ling
  • 2018 Vol. 37 (6): 1705-1715.  DOI:10.7522/j.issn.1000-0534.2018.00099
  • Abstract ( ) HTML PDF (13552KB) ( )
  • This paper investigated the statistical characteristics of snowstorms affected by northward extratropical cyclones in Northeast China by using the conventional observation data, station precipitation data and NCEP 1°×1° reanalysis data from 2000 to 2016.Snowstorms were classified into low vortex, shallow trough and deep trough patterns according to circulation patterns at 500 hPa. In addition, cyclone tracks, intensity change and associated precipitation distribution, water vapor transport and thermodynamic characteristics of snowstorms were analyzed in detail. The results showed that cyclones of low vortex and deep trough patterns moved northeastward while those of shallow trough pattern moved east-northeastward. Intensity change and precipitation distribution of all types of cyclone snowstorms resulted from moving paths of cyclones. Low vortex and deep trough pattern existed a low vortex at 700 hPa and 850 hPa whereas shallow though pattern exhibited a low trough at 700 hPa as the snowfall was at its peak. Water vapor flux convergence region of low vortex and deep trough pattern snowstorms were related to the convergence of cyclonic circulation and those of shallow trough pattern were mainly associated with convergence in front of troughs in low level. Snowstorms of low vortex and deep trough pattern occurred in warm tongue of pseudo-equivalent potential temperature while that of shallow trough pattern concentrated in relatively flat pseudo-equivalent potential temperature field. Front zone of deep trough and shallow trough pattern were more intensive than that of low vortex pattern. Low vortex and deep trough pattern snowstorm had one and two branches of upper level jet streams respectively, while shallow trough pattern had one or two upper level jet streams. The snowstorm centers were located on the right side to the entrance area of north branch or left side to the exit area of the south branch of upper jet stream. Conceptual model of snowstorms produced by northward extratropical cyclones in Northeast China was proposed finally.
  • Characteristics of Precipitation Particles in a Hailstorm Process in Weibei Area of Shaanxi Province
  • YUE Zhiguo;LIANG Gu
  • 2018 Vol. 37 (6): 1716-1724.  DOI:10.7522/j.issn.1000-0534.2018.00023
  • Abstract ( ) HTML PDF (6170KB) ( )
  • It is very important for the study of hail cloud and its suppression to learn the characteristic parameters of hail such as number concentration, the maximum diameter, terminal velocity. Based on the data collected by Parsivel precipitation particle spectrometer in a hail process occurred on 22 May 2013 in Weibei area of Shaanxi Province, combing the data of radar reflectivity and minute precipitation data from the automatic station, the temporal evolution of physical parameters was analyzed that include the rainfall intensity, rainfall amount, maximum hail diameter, number concentration, spectral distribution and hail velocity. The results are shown as follows:(1)The average particle spectrum distributions of rain and hail were calculated for this hail process, and fitted by the Marshall-Palmer exponential distribution. The correlation coefficient of fitting is 0.95 for raindrop with diameter of 0.3~4.75 mm, and 0.99 for hail with diameter of 5.5~11 mm; (2) The number concentrations of hail are 0.3% of the total precipitation particles, and its precipitation accounts for 37% of the total precipitation; (3) During the hail process, the number concentration of raindrop and hail increases or decreases simultaneously. The maximum number concentrations of hail and raindrop are 5 m-3 and 1 423 m-3 in one minute, respectively; (4) This is the first time that the terminal velocity of hail was measured in situ in China. The empirical formula of the average hail velocity is obtained by fitting the measured terminal velocities with the hail diameter, and its relative error is 2.8% in respect to the measured average terminal velocity of hail. This study will be a firm foundation for the further learning the features of hailstorm and the effect of artificial hail suppression in this area, and will be a good reference for the development of explicit cloud physics scheme of numerical model.
  • The Spatial and Temporal Characteristics and Causes of the Frequency of Warm Winter Days in China from 1951 to 2014
  • ZHONG Shanshan;LI Yuan;ZHANG Xinchang
  • 2018 Vol. 37 (6): 1725-1736.  DOI:10.7522/j.issn.1000-0534.2018.00095
  • Abstract ( ) HTML PDF (11533KB) ( )
  • In this paper, the frequency of warm winter days (FWWD) in China (the number of days that high temperature lasts over 6 days) was defined using the observed daily maximum near-surface temperature of HadGHCND from Hadley centre in the UK, and then its variation and possible causes were discussed. There are two main modes for the FWWD. One is a uniform variation pattern, with the maximum mainly located between the north of Yangtze River and north China. When FWWD increases uniformly, the geopotential height shows a dipole distribution with positive and negative anomaly overlying the middle and high latitudes in the eastern hemisphere. The increase of gradient of the geopotential height between the middle and high latitude, leads to the enhancement of the abnormal westerly wind, weakening the meridional circulation between the middle and high latitudes. Therefore, the circulation is dominated by zonal westerly, and the activities of strong cold air are confined near its source. Accordingly, it is difficult for cold air to invade China, resulting in the increase of FWWD. The other is an asymmetric pattern of north-south out of phase, with the maximum located at the steep slope in the southeast of the Qinghai-Tibetan Plateau. When the FWWD is less in the north and more in the south in China, the geopotential height anomalies are arranged orderly as "+-+" southward from the pole. This distribution is similar to the combination of Arctic Oscillation (AO) and Western Pacific (WP) teleconnection pattern. In winter, the Qinghai-Tibetan Plateau, as a elevated cold source, forms a cold high near the surface due to thermal effect, and the anomalous anticyclonic circulation over the Qinghai-Tibetan Plateau strengthens the divergence of airflow, causing the atmosphere subsidence and increase the temperature near the plateau, which is favourable for the maintenance of warm days near the plateau, and more FWWD. The anomalous warm SSTA in China's adjacent sea and warm tongue in the Kuroshio extension area are closely related to the above two main patterns. For the uniform variation pattern, the strongest signal of SSTA is concentrated in the north of the Yangtze River, and for the asymmetric pattern of north-south out of phase, strongest signal of SSTA is located in the south of the Yangtze River. These signals are continuous and have the premonitory significance to the seasonal prediction of the FWWD. In addition, the topography of Qinghai-Tibetan Plateau and the thermal effects as cold source in winter have important effect on the variation of the FWWD around the plateau.
  • Cloud Microphysical Properties of a Tornado Revealed by FY-2G Geostationary Satellite
  • XU Xiaohong;YU Xing;ZHU Yannian;LIU Guihua;DAI Jin
  • 2018 Vol. 37 (6): 1737-1748.  DOI:10.7522/j.issn.1000-0534.2018.00041
  • Abstract ( ) HTML PDF (24066KB) ( )
  • A case of severe convective weather event of tornado occurred in Yancheng, Jiangsu Province on 23 June 2016 was analyzed by using the methodologies of satellite retrieval based on the FY-2G geostationary satellite data. The analyses were focused on cloud microphysical properties, and signals to identify severe convection. The results revealed that:(1) The RGB composition of FY-2G can visualize the cloud microphysical properties and their evolutions. The development and evolution of convective cloud cluster 2 is the main cause of tornado, meanwhile, it is enhanced by its emergence with other clusters. (2) The microphysical properties and signals of severe convection such as tornado are summarized as follows:Cloud top is high with overshooting, whose temperature can reach -83℃. Effective radius (Re) at cloud top is relatively small due to domination by small ice particles with obvious texture of anvils. The Re decreases with decreasing temperature at the upper part of clouds. The glaciation temperature (Tg) is low, which can reach the homogeneous freezing level with small Re. At 08:00 (BJT), FY-2 satellite shows cloud clusters 1, 2, 4 all have potential to develop as severe convection by the above summarized microphysical properties and signals of severe convection, but cloud cluster 2 was found the main one that caused the severe convection via tracking evolution of these 3 cloud clusters. The monitor of this cluster can be as early warning of severe convection. These analyses suggest that the retrieved cloud microphysical properties with signal of severe convection can provide a new way for early warning of severe weather event.
  • Detection of Fog at Night by Using the New Geostationary Satellite Himawari-8
  • WANG Hongbin;ZHANG Zhiwei;LIU Duanyang;YUAN Chengsong;ZHOU Linyi;QIAN Wei
  • 2018 Vol. 37 (6): 1749-1764.  DOI:10.7522/j.issn.1000-0534.2018.00037
  • Abstract ( ) HTML PDF (28683KB) ( )
  • Himawari-8 is the new geostationary satellite of the Japan Meteorological Agency (JMA) and carries the Advanced Himawari Imager (AHI), which is greatly improved over past imagers in terms of its number of bands and its temporal/spatial resolution. In this work, two different methods for the detection of the different levels of fog at night by using the Himawari-8 were developed in China. The two different methods are the method of the difference between the 11.2 μm and 3.9 μm brightness temperatures (BTD3.9~11.2) and the method of 3.9 μm Pseudo-Emissivity (ems3.9). The 3.9 μm Pseudo-Emissivity is the ratio of the observed 3.9 μm radiance and the 3.9 μm blackbody radiance calculated using the 11.2 μm brightness temperature. We identified the parameters optimal threshold at the 2 400 stations and the grid points using the BTD3.9~11.2 and ems3.9 for different levels of fog. Results on land and sea from the two methods were compared with surface observations from 2 400 weather stations in China and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) VFM (Vertical Feature Mask) products. The results showed that both the method of BTD3.9~11.2 and the method of ems3.9 can accurately identify the different levels of fog and the accuracy of ems3.9 method is slightly better than the BTD3.9~11.2. The accuracy of two methods has increased significantly and the false alarm rate has significantly decreased with the decrease of the visibility. When the visibility was less than 50 m, the HR, FAR and KSS of the BTD3.9~11.2 method (the ems3.9 method) were 0.89 (0.90), 0.15 (0.15) and 0.74 (0.75), respectively. When mid-or high-level clouds were removed using surface temperature of the ground observations, the HR and KSS of two methods for the different levels of fog has increased significantly, and the FAR has significantly decreased. When the visibility was less than 1 000 m, the HR of the BTD3.9~11.2 method (the ems3.9 method) was increased to 0.81(0.85) from 0.71 (0.74), the FAR was decreased to 0.12 (0.13) from 0.27 (0.28), and the KSS was increased to 0.69 (0.72) from 0.44 (0.46). The KSS of two method increased by 0.23 and 0.26, respectively. Three cases analysis showed that the fog area can be clearly identified by using the BTD3.9~11.2, ems3.9 and RGB composite image. The results of the detection of sea fog by using Himawari-8 data and using CALIPSO VFM products have consistency.