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THE IMPACT OF MOUNTAIN TO BASIN WINDS ON THE DIURNAL VARIATION IN FOG OVER THE SICHUAN BASIN, china

Journal of Tropical meteorology 2019年第2期25卷 257-268页

作者： ZHANG Fu-ying LIU Hai-wen ZHU Yu-xiang ZHAO Liang DUAN Bo-long FU Ning Nanjing University of Information Science & Technology Department of Aviation meteorology Civil Aviation University of china CMA Training Center china meteorological administration LASG institute of Atmospheric Physics Chinese Academy of Sciences lanzhou Central meteorological Observatory

There is an increased demand for the accurate prediction of fog events in the Sichuan Basin(SCB) using numerical methods. A dense fog event that occurred over the SCB on 22 December 2016 was investigated. The results show that this dense fog event was influenced by the southwest of a low pressure with a weak horizontal pressure gradient and high relative humidity. This fog event showed typical diurnal variations. The fog began to form at 1800 UTC on 21 December 2016(0200 local standard time on 22 December 2016) and dissipated at 0600 UTC on 22 December 2016(1400 local standard time on 22 December 2016). The Weather Research and Forecasting model was able to partially reproduce the main features of this fog event and the diurnal variation in the local mountain to basin winds. The simulated horizontal visibility and liquid water content were used to characterize the fog. The mountain to basin winds had an important role in the diurnal variation of the fog event. The positive feedback mechanism between the fog and mountain to basin winds was good for the formation and maintain of the fog during the night. During the day, the mountain to basin wind displayed a transition from downslope flows to upslope flows. Water vapor evaporated easily from the warm, strong upslope winds, which resulted in the dissipation of fog during the day. The topography surrounding the SCB favored the lifting and condensation of air parcels in the lower troposphere as a result of the low height of the lifting condensation level.

关键词： mountain to basin winds fog events weather research and forecasting simulations Tibetan Plateau

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A Case Study on the Rapid Rain-to-Snow Transition in Late Spring 2018 over Northern china:Effects of Return Flows and Topography

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Journal of meteorological Research 2022年第1期36卷 107-127页

作者： Wenlong ZHANG Xiaopeng CUI Bolong DUAN Bo YU Runxia GUO Haiwen LIU institute of Urban meteorology China Meteorological AdministrationBeijing 100089 Key Laboratory of Cloud-Precipitation Physics and Severe Storms Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 lanzhou Central meteorological Observatory Lanzhou 730020 Beijing Weather Forecast Center Beijing 100089 Department of Aviation meteorology Civil Aviation University of ChinaTianjin 300300 University of Chinese Academy of Sciences Beijing 100049

Phase changes in the precipitation processes of early winter and late spring in midlatitude regions represent challenges when forecasting the timing and magnitude of *** 4 April 2018,a heavy snow process occurred in Beijing and northwestern Hebei Province,becoming the most delayed occurrence of heavy spring snow ever recorded over Beijing in the last 30 *** paper uses observational and numerical simulation data to investigate the causes for the rapid rain-to-snow(RRTS)phase transition during this *** following results are obtained.(1)Return flows(RFs),an interesting type of easterly wind,including those at 1000,925,and 800 hPa,played an important role in this heavy snow process and presented a characteristic"sandwich"*** RFs,complex topography,and snow particles that dominated the clouds,were the three key factors for the RRTS transition.(2)The RRTS transition in the plains was directly related to the RF at 925 hPa,which brought about advective cooling initiated approximately 4-6 h before the onset of ***,the RF played a role of diabatic cooling when snow particles began to fall at the onset of precipitation.(3)The RRTS transition in the northern part of the Taihang Mountains was closely related to the relatively high altitude that led to a lower surface temperature owing to the vertical temperature lapse *** immediately before and after the onset of precipitation,the snow particles in clouds entrained the middle-level cold air downward,causing the melting layer(from surface to the 0℃-isotherm level)to become very thin;and thus the snow particles did not have adequate time to melt before falling to the ground.(4)The rapid RRTS over the Yanqing mountainous area in the northwest of Beijing could have involved all the three concurrent mechanisms:the advective cooling of RF,the melting cooling of cloud snow particles,and the high-altitude *** with that in the plain area with less urbanization the duration

关键词： midlatitude heavy snow return flow phase transition Bohai Sea cold pool complex terrain numerical simulation

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The Influences of Thermodynamic Characteristics on Aerodynamic Roughness Length over Land Surface

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Acta meteorologica Sinica 2013年第2期27卷 249-262页

作者：张强姚彤岳平张立阳曾剑 institute of arid meteorology of CMA Key Laboratory of arid Climatic Change and Disaster Reduction of Gansu Province Key Open Laboratory of arid Climatic Change and Disaster Reduction of CMA meteorological Bureau of Gansu College of Atmospheric Sciences Lanzhou University

It has previously been shown that aerodynamic roughness length changes significantly along with near- surface atmospheric thermodynamic state; however, at present, this phenomenon remains poorly understood, and very little research concerning this topic has been conducted. In this paper, by using the data of different underlying surfaces provided by the Experimental Co-observation and Integral Research in Semi-arid and arid Regions over North china, aerodynamic roughness length （z0） values in stable, neutral, and unstable atmospheric stratifications are compared with one another, and the relationship between z0 and atmospheric thermodynamic stability （（） is analyzed. It is found that z0 shows great differences among the stable, neutral, and unstable atmospheric thermodynamic states, with the difference in z0 values between the fully thermodynamic stable condition and the neutral condition reaching 60% of the mean z0. F^trthermore, for the wind speed range in which the wind data are less sensitive to z0, the surface z0 changes more significantly with （, and is highly correlated with both the Monin-Obukhov stability （4o） and the overall Richardson number （Rib）, with both of their correlation coefficients greater than 0.71 and 0.47 in the stable and unstable atmospheric stratification, respectively. The empirical relation fitted with the experimental observations is quite consistent with the Zilitinkevich theoretical relation in the stable atmosphere, but the two are quite distinct and even show opposite variation tendencies in the unstable atmosphere. In application, however, verification of the empirical fitted relations by using the experimental data finds that the fitted relation is slightly more applicable than the Zilitinkevich theoretical relation in stable atmospheric stratification, but it is much more suitable than the Zilitinkevich relation in unstable atmospheric stratification.

关键词： near-surface atmosphere thermodynamic characteristics aerodynamic roughness length Zil- itinkevich theoretical relationship parametric relations

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Climatic Warming and Humidification in the arid Region of Northwest china: Multi-Scale Characteristics and Impacts on Ecological Vegetation

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Journal of meteorological Research 2021年第1期35卷 113-127页

作者： Qiang ZHANG Jinhu YANG Wei WANG Pengli MA Guoyang LU Xiaoyun LIU Haipeng YU Feng FANG lanzhou institute of arid meteorology of china meteorological administration(CMA)/Key Laboratory of arid Climate Change and Disaster Reduction of Gansu Province/Key Open Laboratory of arid Climate Change and Disaster Reduction of CMA Lanzhou 730020 Gansu meteorological Bureau China Meteorological AdministrationLanzhou 730020 lanzhou Regional Climate Center China Meteorological AdministrationLanzhou 730020 Northwest institute of Eco-Environment and Resources/Key Laboratory of Land Surface Process and Climate Change in Cold and arid Regions Chinese Academy of SciencesLanzhou 730000

The climatic warming and humidification observed in the arid region of Northwest china(ARNC) and their impacts on the ecological environment have become an issue of concern. The associated multi-scale characteristics and environmental responses are currently poorly understood. Using data from satellite remote sensing, field observations, and the Coupled Model Intercomparison Project phase 6, this paper systematically analyzes the process and scale characteristics of the climatic warming and humidification in the ARNC and their impacts on ecological vegetation. The results show that not only have temperature and precipitation increased significantly in the ARNC over the past 60 years, but the increasing trend of precipitation is also obviously intensifying. The dryness index, which comprehensively considers the effects of precipitation and temperature, has clearly decreased, and the trend in humidification has increased. Spatially, the trend of temperature increase has occurred over the entire region, while 93.4% of the region has experienced an increase in precipitation, suggesting a spatially consistent climatic warming and humidification throughout the ARNC. Long-term trends and interannual changes in temperature and precipitation dominate the changes in climatic warming and humidification. Compared to interannual variations in temperature, the trend change of temperature contributes more to the overall temperature change. However, the contribution of interannual variations in precipitation is greater than that of the precipitation trend to the overall precipitation change. The current climatic warming and humidification generally promote the growth of ecological vegetation. Since the 1980 s,82.4% of the regional vegetation has thrived. The vegetation index has a significant positive correlation with precipitation and temperature. However, it responds more significantly to interannual precipitation variation, although the vegetation response varies significantly u

关键词： arid region of Northwest china(ARNC) climatic warming and humidification ecological vegetation multi-scale synergistic effect

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Characteristics of land surface thermal-hydrologic processes for different regions over North china during prevailing summer monsoon period

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Science china Earth Sciences 2012年第9期55卷 1872-1880页

作者： ZHANG Qiang ZENG Jian ZHANG LiYang institute of arid meteorology of CMA Key laboratory of Arid Climatic Change and Reducing Disaster of Gansu ProvinceKey Open Laboratory of Arid Climatic Change and Disaster Reduction of CMALanzhou 730020China meteorological Bureau of Gansu Lanzhou 730020China Beijing meteorological Bureau Beijing 100089China College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China

The observation stations of Northern china are divided into three regions:the arid Northwest china,the Loess Plateau,and the cool Northeast *** consistencies,differences,and associated mechanisms of land surface thermal-hydrologic processes among the three regions were studied based on the normalization of major variables of land surface thermal-hydrologic processes,using data collected during prevailing summer monsoon period(July and August,2008).It is shown that differences of surface thermal-hydrologic processes are remarkable among the three regions because of different impacts of summer *** their soil wet layers occur at different depths,and the average albedo and its diurnal variations are distinctly *** net short-wave radiation in the Loess Plateau is close to that in the cool Northeast china,but its surface net long-wave radiation is close to that in the arid Northwest *** the ratio of net radiation to global solar radiation in the cool Northeast china is higher than the other two regions,though its temperature is *** are obvious regional differences in the ratios of surface sensible and latent heat fluxes to net radiation for the three regions because of distinct contribution of sensible and latent heat fluxesto land surface energy *** three regions are markedly different in the ratio of water vapor flux to pan evaporation,but they are consistent in the ratio of water vapor flux to *** results not only indicate different influences of climate and environmental factors on land surface thermal-hydrologic processes in the three regions,but also show that summer monsoon is important in the formation and variation of the pattern of land surface thermal-hydrologic processes.

关键词： different regions of North china prevailing summer monsoon period coordinated experiment land surface thermalhydrologic processes influence factors

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RIVER DISCHARGE CHANGES IN THE QINGHAI-TIBET PLATEAU

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Chinese Science Bulletin 2006年第5期51卷 594-600页

作者： CAO Jianting QIN Dahe KANG Ersi LI Yuanyuan Laboratory for Climatic Studies China Meteorological Administration Beijing 100081 China General institute for Water Resources and Hydropower Planning and Design Ministry of Water Resources Beijing 100011 China china meteorological administration Beijing 100081 China Cold and arid Regions Environmental and Engineering Research institute Chinese Academy of Sciences. Lanzhou 730000 China

Annual mean discharge data of the five large rivers in the exorheic region of the Qing- hai-Tibet Plateau from 1956 to 2000 are analyzed for trends with the Mann-Kendall nonparametric trend test. The results reveal that though in general no in- creasing trends exist in the total river discharges, significant regional differences of river discharge ex- ist, reflecting the decreasing trends of discharge in the Yellow River and the Tongtian River (upper Changjiang River), an increasing trend in Yalong River, and inverted change in the Lancang River and Yarlung Zangbo River. Based on analyses of the seasonal discharge, it is found that climatic change had a significant effect on the seasonal variation of river discharge in the Qinghai-Tibet Plateau. In spring (from March to May) the discharge increased signifi- cantly, especially in the source area of the Yellow River. Together with the analyses on data of the mean temperature in the Northern Hemisphere and climatic data within the river basins, the relationship between discharges and mean temperature of the Northern Hemisphere is explored, which indicates that there is no increase in the stream discharge in the Qinghai-Tibet Plateau with global warming. It is probably the increasing evaporation, caused by rising temperature that offsets the hydrological effect of increasing precipitation.

关键词：河流流量曼-肯德尔试验水循环青藏高原全球变暖

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Diurnal Variation Characteristics of Precipitation in the Shiyang River Basin of Northwest china in Summer

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Atmospheric and Climate Sciences 2017年第4期7卷 558-576页

作者： Weicheng Liu Qiang Zhang Lingping Li lanzhou Central meteorological Observatory Lanzhou China institute of arid meteorology China Meteorological Administration Key Laboratory of Arid Climatic Change and Disaster Reduction of China Meteorological Administration/Key Laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province Lanzhou China Gansu Provincial meteorological administration Lanzhou China Wuwei meteorological Bureau Wuwei China

Based on the hourly precipitation data from 32 regional meteorological stations and 5 automatic meteorological stations in summer (from June to August) over the Shiyanghe River basin from 2009 to 2013, we analyzed the diurnal variation characteristics of precipitation over the Shiyanghe River basin, by using four precipitation indices (hourly precipitation, hourly precipitation frequency, hourly precipitation intensity, and different duration precipitation). The results show that the spatial distribution of hourly precipitation, hourly precipitation frequency in summer declines from upstream to downstream over the Shiyanghe River basin because of geographical position, altitude, latitude and weather systems, and the spatial distribution of hourly intensity is complex. The precipitation, the precipitation frequency and the precipitation intensity over the Shiyanghe River basin present a diurnal pattern of double-peak distribution, with the peak periods at 01:00-09:00 and 14:00-23:00, strong precipitation present single-peak with the peak period at 14:00-23:00. Total precipitations and precipitation frequencies of 1 - 3 h short-time rainfall are more than long time rainfall continued more than 10 h over the Shiyanghe River Basin. The short-time rainfall continuing within 1 - 6 h often occurs from afternoon to evening, the long time rainfall continuing more than 6 h often occurs from evening to early morning or late afternoon to evening.

关键词： Shiyanghe River Basin Hourly Precipitation Different Duration Precipitation Diurnal Variation

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Debating about the climate warming

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Progress in Natural Science:Materials International 2006年第1期16卷 1-6页

作者： WANG Shaowu1, LUO Yong2, ZHAO Zongci2, DONG Wenje2 and YANG Bao3 (1.Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871, china 2. Laboratory for Climate Studies, china meteorological administration, Beijing 100081, china 3. institute of Cold and arid Regions Environmental and Engineering, Chinese Academy of Sciences, lanzhou 730000, china) Department of Atmospheric Sciences School of Physics Peking University Beijing 100871 China Laboratory for Climate Studies China Meteorological Administration Beijing 100081 China institute of Cold and arid Regions Environmental and Engineering Chinese Academy of Sciences Lanzhou 730000 China

Debating about the climate warming is reviewed. Discussions have focused on the validity of the temperature reconstruction for the last millennium made by Mann et al. Arguments against and for the reconstruction are introduced. Temperature reconstructions by other authors are examined, including the one carried out by Wang et al. in 1996. It is concluded that: (1) Ability of reproducing temperature variability of time scale less than 10 a is limited, so no sufficient evidence proves that the 1990s was the warmest decade, and 1998 was the warmest year over the last millennium. (2) All of the temperature reconstructions by different authors demonstrate the occurrence of the MWP (Medieval Warm Period) and LIA (Little Ice Age) in low frequency band of temperature variations, though the peak in the MWP and trough in LIA varies from one reconstruction to the others. Therefore, terms of MWP and LIA can be used in studies of climate change. (3) The warming from 1975 to 2000 was significant, but we do not know if it was the strongest for the last millennium, which needs to be proved by more evidence.

关键词： climate warming MWP LIA the 20th century.

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Carbonaceous particles in the atmosphere and precipitation of the Nam Co region, central Tibet

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Journal of Environmental Sciences 2010年第11期22卷 1748-1756页

作者： Jing Ming Cunde Xiao Junying Sun Shichang Kang Paolo Bonasoni State Key Laboratory of Cryospheric Sciences Cold and Arid Region Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China National Climate Center China Meteorological Administration Beijing 100081 China Laboratory for Atmospheric Chemistry Centre for Atmosphere Watch & Services China Meteorological Administration Beijing 100081 China institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China institute for Atmospheric Sciences and Climate CNR Bologna Italy

A continuous air and precipitation sampling for carbonaceous particles was conducted in a field observatory beside Nam Co, Central Tibetan Plateau during July of 2006 through January of 2007. Organic carbon （OC） was the dominant composition of the carbonaceous particles both in the atmosphere （1660 ng/m ^3 ） and precipitation （476 ng/g） in this area, while the average elemental carbon （BC） concentrations in the atmosphere and precipitation were only 82 ng/m 3 and 8 ng/g, respectively. Very high OC/BC ratio suggested local secondary organic carbon could be a dominant contribution to OC over the Nam Co region, while BC could be mainly originated from Southern Asia, as indicated by trajectory analysis and aerosol optical depth. Comparison between the BC concentrations measured in Lhasa, those at ＂Nepal Climate Observatory at Pyramid （NCO-P）＂ site on the southern slope of the Himalayas, and Nam Co suggested BC in the Nam Co region reflected a background with weak anthropogenic disturbances and the emissions from Lhasa might have little impact on the atmospheric environment here, while the pollutants from the Indo-Gangetic Basin of Southern Asia could be transported to the Nam Co region by both the summer monsoon and the westerly.

关键词： carbonaceous particle elemental carbon organic carbon Nam Co Tibetan Plateau

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Classified Early Warning and Forecast of Severe Convective Weather Based on LightGBM Algorithm

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Atmospheric and Climate Sciences 2021年第2期11卷 284-301页

作者： Xinwei Liu Haixia Duan Wubin Huang Runxia Guo Bolong Duan lanzhou Central meteorological Observatory Lanzhou China lanzhou institute of Drought meteorology China Meteorological Administration Lanzhou China

Severe convective weather can lead to a variety of disasters, but they are still difficult to be pre-warned and forecasted in the meteorological operation. This study generates a model based on the light gradient boosting machine (LightGBM) algorithm using C-band radar echo products and ground observations, to identify and classify three major types of severe convective weather (i.e., hail, short-term heavy rain (STHR), convective gust (CG)). The model evaluations show the LightGBM model performs well in the training set (2011-2017) and the testing set (2018) with the overall false identification ratio (FIR) of only 4.9% and 7.0%, respectively. Furthermore, the average probability of detection (POD), critical success index (CSI) and false alarm ratio (FAR) for the three types of severe convective weather in two sample sets are over 85%, 65% and lower than 30%, respectively. The LightGBM model and the storm cell identification and tracking (SCIT) product are then used to forecast the severe convective weather 15 - 60 minutes in advance. The average POD, CSI and FAR for the forecasts of the three types of severe convective weather are 57.4%, 54.7% and 38.4%, respectively, which are significantly higher than those of the manual work. Among the three types of severe convective weather, the STHR has the highest POD and CSI and the lowest FAR, while the skill scores for the hail and CG are similar. Therefore, the LightGBM model constructed in this paper is able to identify, classify and forecast the three major types of severe convective weather automatically with relatively high accuracy, and has a broad application prospect in the future automatic meteorological operation.

关键词： Severe Convective Weather Machine Learning LightGBM Early Warning and Forecast

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