ISSN 1000-0526
CN 11-2282/P

Volume 46,Issue 12,2020 Table of Contents

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  • 1  Verification on Surface Wind Speed Forecast of Shanghai Meteorological Service-WRF ADAS Rapid Refresh System (SMS-WARR)
    XUE Wenbo YU Hui TANG Shengming HUANG Wei JIANG Wendong ZHOU Xiangxian LU Yi
    2020, 46(12):1529-1542. DOI: 10.7519/j.issn.1000-0526.2020.12.001
    [Abstract](178) [HTML](255) [PDF 7.94 M](824)
    In order to evaluate the wind speed forecast ability of Shanghai Meteorological Service-WRF ADAS Rapid Refresh System (SMS-WARR), the 10 m wind was divided into three levels to analyze the error characteristics and corresponding causes of formation, especially during the period of typhoon influence. The results show that the SMS-WARR model overestimates the wind weaker than Grade 6 and underestimates the wind stronger than or equal to Grade 6 in each lead time. The wind speed forecast score decreases for the wind weaker than Grade 6 and increases for the wind stronger than or equal to Grade 6 with the increase of lead time. The forecast and observed wind speeds are obviously linearly correlated between 5%-90% quartiles. During the period of typhoon influence, the area of strong wind (Grade 6) is much larger than the area where the strong wind was actually measured. The area of large deviation is mainly distributed in the area of forecast strong wind. These error characteristics may be related to the scheme setting of the cold and hot starting of the model and the model’s weak predictability to the wind field during the rapid strengthening phase of typhoons.
    2  Radar Climatology Analysis of Warm Season Afternoon Convective Storm over Shanghai
    GUAN Li DAI Jianhua ZHAO Yuanming TIAN Hongjun QIN Nannan
    2020, 46(12):1543-1554. DOI: 10.7519/j.issn.1000-0526.2020.12.002
    [Abstract](176) [HTML](211) [PDF 10.06 M](1560)
    During the warm season (June-September) from 2014 to 2018, the sounding parameters and indices of convention as well as the spatial characteristics and distributions of the afternoon convective storms in Shanghai under weak synoptic-scale forcing were documented using atmospheric sounding data, storm tracking identification (STI) and storm structure (SS) products. The STI product provides storms’ current position and the historical position. Intending to reveal the trigger mechanism in Shanghai under weak synoptic-scale forcing, storm frequency statistics in different regions were made utilizing the storm position firstly, then the spatial distribution of storm track was analyzed based on storm historical position. The convective storms in afternoon were classified into three types including storm from other places, localized moving storm and localized anchoring storm according to storm position and historical routes. The corresponding storm structure was introduced to reveal the differences of storm life cycle as well as the storm structure characters. The results show that the afternoon convective storms that affect Shanghai in warm season mainly occur in the region from urban to the Yangtze River Estuary, which is mainly due to the urban heat island effect and the northern sea breeze. There are significant differences among the three types storms in life cycle, centroid height, vertical integral liquid, maximum reflectivity and height of maximum reflectivity.
    3  Application of Statistical Downscaling Model to Autumn Rainfall Forecasting over Southwest China
    WU Yao TANG Hongyu LIU Ying DONG Xinning GUO Qu
    2020, 46(12):1555-1564. DOI: 10.7519/j.issn.1000-0526.2020.12.003
    [Abstract](154) [HTML](198) [PDF 4.34 M](651)
    A statistical downscaling model for forecasting autumn rainfall at stations over Southwest China was established in this study based on real-time prediction of numerical products from the Climate Forecast System (CFS) and observation data. The autumn 500 hPa geopotential height from CFS and summer sea surface temperature from reanalysis data, which are relatively clear in physics for autumn rainfall over Southwest China, were selected as the two predictors. The key regions of the two predictors are 10°S-50°N/70°-180°E and 30°S-30°N/30°-120°E. There exist high correlations of time coefficient of first leading SVD modes between predictors and observation. The correlation coefficients have passed the 0.01 significance level test on the 500 hPa geopotential height field and the 0.001 significance level test on the sea surface temperature field. The statistical downscaling hindcast for the 1982-2017 result shows that the spatial correlation coefficient can improve the performance of prediction compared with that of the original CFS, and multi-year mean is increased from -0.06 to 0.38 with the maximum getting up to 0.7. The root mean square error decreases in comparison with the output of original CFS at most stations with the maximum being 40%. At the same time, the statistical downscaling hindcasts on spatial pattern of extreme minimum and maximum are fine.
    4  On the Use of Small Unmanned Aircraft System for the Atmospheric Surface Layer Measurements over the Urbanized Areas
    FU Xinshu WANG Xiaofeng LEI Ming DU Mingbin XIA Weizu CHEN Zhe ZHANG Zilong
    2020, 46(12):1565-1574. DOI: 10.7519/j.issn.1000-0526.2020.12.004
    [Abstract](159) [HTML](119) [PDF 1.50 M](547)
    This study is to demonstrate whether the accurate and high spatio-temporal resolution thermodynamic profiles of the lower atmospheric boundary layer (ABL) over the urbanized areas could be obtained by small unmanned aircraft system (sUAS). Twenty flights in total were conducted in Shanghai during winter (in December 2018) and spring (in March 2019) months, and 19 profiles (surface-200 m) of temperature and relative humidity were collected. Measurements from automatic weather station (AWS) and radiosonde at the same site were used to evaluate these profiles. The results showed that surface temperature and relative humidity observed by sUAS are close to those from AWS, with the mean differences of -0.5℃, 4.9% for winter flights and 0.9℃, -5.9% for spring flights. The general features of temperature and relative humidity profiles obtained by sUAS are consistent with those from radiosonde, such as temperature inversion near the ground and so on. These findings indicate that sUAS is capable of revealing detailed structures and variations of the lower ABL over the urbanized areas.
    5  Applicability of FY-4A Surface Solar Irradiance Products in the Loess Plateau of Shanxi
    LIANG Jinqiu SHEN Yanbo HU Liqin WU Lindong SHI Zhanjun
    2020, 46(12):1575-1584. DOI: 10.7519/j.issn.1000-0526.2020.12.005
    [Abstract](153) [HTML](144) [PDF 3.56 M](627)
    In this paper, the Loess Plateau of Shanxi was selected as the research area, and the quality of FY-4A surface solar irradiance (SSI) was comparatively tested by using the minutely global irradiance data of three national meteorological stations in the region.The results show that SSI is highly correlated with ground observation data in Loess Plateau of Shanxi, which can better reflect the influence of meteorological factors on solar radiation. The global irradiance is generally high, and the relative error decreases with the increase of the global irradiance observed on the ground. The morning and evening errors are large but the noon errors are small. From the transverse comparison of Datong, Taiyuan and Houma stations, the higher the annual global radiation exposure, the smaller the relative errors. The critical value of sunset zenith angle is set at 70° in FY-4A SSI algorithm, resulting in about 1/3 of the whole year’s non observed time in daytime. The total radiation exposured in winter is lower than that in summer, which makes the monthly global radiation exposure lower in winter but higher in summer. The above characteristics of SSI are basically derived from its algorithm or parameter settings, so it has universality. Due to the strong regularity of relative errors, it is possible to revise the data and reduce the error level substantially in the next step.
    6  Preliminary Experimental Study on Improving Cloud Computing Process with Satellite Data
    ZHAO Chenyang XU Guoqiang HUANG Shouyou
    2020, 46(12):1585-1595. DOI: 10.7519/j.issn.1000-0526.2020.12.006
    [Abstract](177) [HTML](201) [PDF 71.30 M](805)
    The GRAPES_Meso model was used to simulate two rainfall processes in 2018. The relevant cloud variables of model calculation and satellite observation were compared and analyzed. The results show that in the existing cloud computing scheme of GRAPES_Meso model, there is excessive high cloud cover in some places and deficit cloud cover in the mid- and low-level dense-closed cloud region. The cloud top temperature simulated by GRAPES_Meso model is obviously lower and the cloud top height is obviously higher. To address these issues, the principles and formulas of the cloud computing scheme are interpreted, and the calculation for-mula is optimized. After adopting the improved cloud computing scheme, the excessive high cloud cover is greatly alleviated, and the low cloud top temperature and high cloud top height are greatly optimized. Based on satellite observation data, the preliminary exploration and test on the optimization of cloud computing scheme provides a new means for researching and optimizing cloud computing scheme.
    7  Mechanism Analysis of a Rare “Thunder Snow” Process in Semi-Arid Area
    LIU Xiaoyue YU Haipeng SHENG Xia ZHU Changquan ZHAO Qingyun MA Yuxia GOU Shang
    2020, 46(12):1596-1607. DOI: 10.7519/j.issn.1000-0526.2020.12.007
    [Abstract](175) [HTML](175) [PDF 11.70 M](1211)
    In this paper, the meteorological observation data, NCEP reanalysis data, Himawari-8 satellite data were used to analyze a rare thunderstorm in the northwest semi-arid region from 8 to 9 October 2017. Its causes and mechanisms were discussed. The results show that the rare thunderstorm process originated from the eastern part of the Qinghai-Tibet Plateau, developed in the background of a ground warm center in front of the trough, and had the characteristics of surface-based convection. The thunderstorms seen in Lanzhou, about 150 km away from the surface front, occurred with a deep and stable cold air cushion. There were obvious inversion layers in the middle and lower layer, and warm and humid air with conditional instability above the inversion layer, which had the structural characteristics of elevated thunderstorms. This elevated thunderstorm process was different from the thunderstorm in the eastern humid area. In terms of its development and evolution, this elevated thunderstorm was actually the continuation and development of the surface-based thunderstorm in the Qinghai-Tibet Plateau, moving to the cold air cushion in lower elevation. In terms of the structural characteristics, the heights corresponding to each feature level (cold air cushion, inversion layer, etc.) in this process were significantly higher than those in the low-altitude areas in the east, but there was no significant difference in the thickness of each corresponding layer. In terms of the formation mechanism of the cold air cushion, the land-atmosphere energy exchange in the semi-arid area of the northwest was dominated by the sensible heat. With the combined effect of the unique underlying surface and strong cold air, the Loess Plateau with complex topography can also form a relatively stable cold air cushion. From the perspective of instability mechanism, the surfaced-based thunderstorm in east of the Qinghai-Tibet Plateau and the elevated thunderstorm were both caused by conditional instability. The structure of “cold and dry in the upper level, warm and wet in the lower level” was observed in the east of the Qinghai-Tibet Plateau. The updraft was induced under the combined action of high-altitude jet and 500 hPa high-level trough. In Lanzhou, the strong warm-wet advection in the middle troposphere enhanced the conditional instability above the inversion layer. The convergence effect of 700 hPa shear line cooperating with the synoptic-scale forcing of 500 hPa trough triggered the ascending motion and released the unstable energy, providing favorable conditions for the maintenance and development of vertical convection that moved eastward from the plateau to the cold air cushion.
    8  Dual-Polarization Radar Characteristic Analysis of the Evolution of Heavy Hail Supercell in Southern Fujian
    PAN Jiawen WEI Ming GUO Lijun RUAN Yue LUO Changrong WU Linghan
    2020, 46(12):1608-1620. DOI: 10.7519/j.issn.1000-0526.2020.12.008
    [Abstract](164) [HTML](134) [PDF 9.64 M](769)
    Investigating the evolution of the polarimetric signatures, dynamical and microphysical characteristics in the heavy hail supercell are beneficial to understanding the physical processes that lead to heavy hail formation, determining possible precursive signatures associated with heavy hail formation and growth, and improving warnings for heavy hail supercell. A supercell accompanied by heavy hail in southern Fujian on 22 April 2019 which was detected by the Xiamen S-band dual-polarization radar was analyzed using the dual-Doppler radars wind field retrieval and hydrometeor classification algorithm. The study reveals that the differential reflectivity (Zdr) at the beginning portion of the three-body scatter signature (TBSS) was very high, located radially behind the horizontal reflectivity (Zh) core. It was also found that the cross-correlation coefficient (CC) is very low in the TBSS. Polarimetric signatures associated with TBSS are good indicators of heavy hail aloft. The polarimetric signatures of the heavy hail region manifested as high values of Zh collocated with near-zero value of Zdr. However, during the heavy hail descent, Zdr increased and CC decreased on the periphery of the hail core. The increased Zdr and decreased CC due to the increasing presence of water coating on the melting hailstones. At low level, an area of enhanced specific differential phase (Kdp) was observed within the Zh core of supercell, which was called the Kdp foot. Kdp was less sensitive to heavy hail and thus was a better indicator of melting hail. Therefore, the Kdp foot may be a favorable index of the downdraft zone which was driven by melting of hail. The horizontal wind field showed a distinct double vortex developing in the supercell. The double vortex structure contributed to the development of supercell and the circulation growth of heavy hail. On the northeast of the mesocyclone, a zone of modest Zh, low Zdr, and high CC were observed, called the graupel belt. The hydrometeor classification algorithm suggests that graupel is the dominant hydrometeor type. Because of the proximity to the mesocyclone, some of the graupel were entrained into the updraft, serving as hail embryos. The schematic diagrams of polarimetric signatures and three-dimensional wind field structure of the heavy hail supercell are given based on these analyses.
    9  Analysis on the Environment Conditions of Afternoon Thunderstorm in Hangzhou
    FAN Limiao YU Xiaoding
    2020, 46(12):1621-1632. DOI: 10.7519/j.issn.1000-0526.2020.12.009
    [Abstract](145) [HTML](117) [PDF 2.55 M](715)
    In this paper, 28 cases of afternoon thunderstorm in Hangzhou from June to August in 2013-2018 were selected for research. There are four main paths (from more to less frequent): northwest moving to eastward, southwest to northeast, southeast to northward, and locally generated in Hangzhou. From the evolution of dual-polarization radar echo, three key areas of thunderstorm can be seen, including northwest, southwest and northeast. Three types of thunderstorm conceptual model are: cold advection forcing category, warm advection forcing category and quasi-barotropic category, of which, the quasi-positive pressure type in Hangzhou Area is mostly combined with boundary layer convergence line and east wind belt system. The near-surface meso-scale convergence line is the lifting trigger mechanism, which is related to boundary weak cold air invasion, subtropical high control, land and sea distribution, topography and other factors. The characteristics of the T-lnp diagram are: a moderate intensity CAPE, dry air in mid and high level, a shallow wet layer in the lower layer, the lapse rate of atmospheric temperature in the lower atmosphere, close to dry adiabatic, and an inverted “V” shape, shown by the temperature and dew point profile under the wet layer. The average values of CAPE and DCAPE are above 1 〖KG-*5〗000 J·kg-1. The average temperature-dewpoint difference of middle layer and the maximum temperature-dewpoint difference of single layer can well represent the dry air of middle layer. In summer, thunderstorms usually occur under the condition of weak vertical wind shear. The wind index has some indication.
    10  Comprehensive Analysis on the Conditions of Artificial Precipitation Enhancement During a Precipitation Weather Process in Henan Province
    BAI Ting HUANG Yimei FAN Qi
    2020, 46(12):1633-1640. DOI: 10.7519/j.issn.1000-0526.2020.12.010
    [Abstract](138) [HTML](144) [PDF 16.21 M](978)
    Based on the NCEP/NCAR reanalysis data, satellite, radar and aircraft observation data, the artificial precipitation enhancement conditions of the 5 November 2018 precipitation process in Hennan Pro-vince were analyzed. The results show that the precipitation process was mainly affected by the low-level shear line and the surface cold front. The operational area of the aircraft had a better water vapor condition and a thick ice surface supersaturated layer, and the dynamic conditions were conducive to promoting the development of precipitation. The aircraft operating area was almost full of stratified hybrid clouds, and the cloud system was in a developing stage. In addition, the relationship between the supercooled water area of satellite inversion and the number concentration of the aircraft detection particles was emphatically analyzed. It was found that when using the FY-4A satellite visible light channel, 3.7 μm channel and infrared channel data to conduct the three-color synthesis analysis on the supercooled water in the cloud, the number concentration of particles detected by the aerosol particle probe is also greater than 20 cm-3. They have a good correspondence, indicating that the method analyzing supercooled water in the cloud by the three-color synthesis could be applied to one of the selection conditions of the artificial precipitation enhancement area.
    11  Evolution Characteristics of Continuous Drought in Late Summer and Autumn in the Middle and Lower Reaches of Yangtze River Valley in 2019
    LI Jun YUAN Yuan WANG Zunya ZHAO Wei YUAN Huihui YU Hongdi
    2020, 46(12):1641-1650. DOI: 10.7519/j.issn.1000-0526.2020.12.011
    [Abstract](125) [HTML](204) [PDF 7.46 M](664)
    In the late summer and autumn of 2019, the most severe meteorological drought struck the middle and lower reaches of the Yangtze River Valley (MLRYRV) in the past 50 years, bringing serious adverse effects on agriculture, ecology and water resources in seven provinces located in the MLRYRV. Using datasets of daily temperature and precipitation at stations in China and daily meteorological drought composite index, this paper analyzed the main characteristics of this severe drought in the seven provinces (Hubei, Hunan, Anhui, Jiangxi, Jiangsu, Zhejiang and Fujian) in 2019. The spatio-temporal evolution of the drought was also briefly compared with the spring drought in 2011, which was the most serious drought in spring of recent decade. The analysis showed that from late July to autumn in 2019 (from 20 July to 30 November), the regional average precipitation was the lowest in the same period of recent 50 years, and the average dry days and the average temperature were respectively the second most and the highest during the same period since 1961. The continuous high temperature and few rainfall in this area led to the rapid development of meteorological drought. The average and maximum area above the severe drought level have reached the largest in the same period of history since 1961, making it the most seriously continuous drought in late summer and autumn during the past 50 years. The significant characteristics of this severe drought are as follows: the drought had a wide range of influence and great intensity; the drought started from the lower reach of Yellow River and Huai River and terminated in the regions south of the Yangtze River Valley, where it persisted for a very long time and caused the most serious drought disaster; the drought vibrated from east to west and oscillated from north to south in longitudes and latitudes, respectively; and its averaged intensity and duration in each stage showed a wave characteristic with roughly reversed phase.
    12  Analysis of the September 2020 Atmospheric Circulation and Weather
    WANG Haiping XU Yinglong
    2020, 46(12):1651-1656. DOI: 10.7519/j.issn.1000-0526.2020.12.012
    [Abstract](145) [HTML](256) [PDF 6.27 M](795)
    The main characteristics of the general atmospheric circulation in September 2020 are as follows. The polar vortex of Northern Hemisphere presented a single-pole pattern, while the westerlies presented a four-wave pattern in middle-high latitudes. The western Pacific subtropical high was distributed in the east-west direction, more eastward and southward than normal. The monthly mean precipitation amount was 88.1 mm, which is more than its normal value by 34.9%, being the most accumulated precipitation in the same period since 1961. The monthly mean temperature was 17.2℃, 0.6℃ higher than the climatological mean (16.6℃). The number of landing typhoons generated is less than normal, but Typhoons Maysak and Haishen brought severe gales and rainstorms to Northeast China, making the daily rainfall in many places exceeded the local historical maximum in September.

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