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  • Spatio-Temporal Changes of Key Climatic Elements in the Upper Yellow River Water Conservation Area in Recent 60 Years
  • Zihan ZHANG, Xuejia WANG, Meixue YANG, Lanya LIU, Jichun LI, Guoning WAN
  • 2023, 42 (6): 1372-1385. DOI: 10.7522/j.issn.1000-0534.2023.00011
  • Abstract (2034) PDF (2797KB)(166)
  • The upper Yellow River water conservation area is an important section for ecological protection and high-quality social-economic development in the Yellow River Basin.The impact of climate change on the spatio-temporal distribution of its water resources will exacerbate the occurrence of natural disasters, which in turn will affect China's regional ecology and even the living environment of human beings.Based on the CN05.1 gridded air temperature, precipitation, and wind speed data from 1961 to 2016 and the actual evaporation data of GLEAM V3.5a from 1981 to 2020, this paper analyzed the changes of key climatic elements in the water conservation area of the upper Yellow River Basin in the past 60 years.The results are as follows: (1) The air temperature in the research area increased significantly, the variation trend of the air temperature can reach 0.34 °C·(10a)-1, and the largest temperature rise occurred in winter.Maqu county and surrounding areas in Heihe region have seen the most dramatic warming.(2) The regional precipitation increased as a whole, the variation trend of the precipitation is about 9.3 mm·(10a)-1.The growth rate was relatively rapid in spring and summer, and the slowest occurred in winter.The growth trend gradually decreased from the northwest to the southeast, with a significant increase in the arid regions of the west, and a relative decreasing trend in the humid regions of the southeast.(3) After experienced an anomalous rise in the early 1970s, the near-surface wind speed continued to decline, the variation trend of it is about -0.11 m·s-1·(10a)-1, and the wind speed decreased in most regions of the study area, especially in the northern Datong River area.(4) The actual evaporation showed an increasing trend, the variation trend of it is 11.89 mm·(10a)-1, of which the relatively large increases occurred in spring and winter, and the growth rate showed a trend of gradual increasing from east to west.Among them, the increase of the actual evaporation in Zhaling Lake, Eling Lake area and the western part of Datong River area was the most significant, and only a few places in the middle and southeast decreased.(5) From the perspective of precipitation and evaporation, the growth rate of precipitation is slightly higher than that of the actual evaporation during the same period (from 1981 to 2016), therefore the water conservation area in the upper reaches of the Yellow River Basin also has the trends of warming and wetting as the climate warms.

  • Comparative Analysis of Coupling Relationship Between Land Surface Processes and Atmospheric Boundary Layer Evolution in Nagqu Area in Different Seasons
  • Guantian WANG, Zeyong HU, Genhou SUN, Yaoxian YANG, Lianglei GU, Chunwei FU, Weiwei FAN, Di WU, Ruijia NIU, Hongyu LUO
  • 2023, 42 (6): 1361-1371. DOI: 10.7522/j.issn.1000-0534.2023.00020
  • Abstract (2025) PDF (4389KB)(186)
  • The coupling relationship between land surface processes and atmospheric boundary layer is one of the key links and difficulties in understanding the thermal effect over the Qinghai-Xizang Plateau.Based on the surface and radiosonde observation data of Nagqu Plateau Climate and Environment Observation and Research Station in May, July and October 2019, this paper analyzes the surface energy budget, the daily and seasonal variations of vertical profile of atmospheric temperature and humidity, in Nagqu Area of the Qinghai-Xizang Plateau, and discusses the evolution law of the atmospheric boundary layer height in different seasons in this region.The results show that the convective boundary layer is 2842 m high in sunny days due to the influence of diurnal net radiation intensity during the observation period in May.It is 1481 m high in cloudy day, which is relatively low, and the strong convective weather may change it into a stable boundary layer.In the meanwhile, the exchange between the sensible heat and the latent heat in the near surface atmosphere provides energy support for the maintenance and development of the atmospheric boundary layer.The vertical profile of potential temperature and specific humidity can correctly reflect the seasonal difference of atmospheric boundary layer height in gqu Area.The height of the convective boundary layer is highest in May, less high in October and the lowest in July while the stable boundary layer is highest in July, less high in May and lowest in October.

  • Progress of the Evolutionary Characteristics of Autumn Rain in Western China and Its Anomalous Mechanism for the Past 20 Years
  • Yinuo LI, Yueqing LI
  • 2024, 43 (1): 1-15. DOI: 10.7522/j.issn.1000-0534.2023.00028
  • Abstract (2000) PDF (1341KB)(262)
  • Autumn rain in western China is a unique and complex precipitation phenomenon that takes place during the autumn season in the western region of China, which is closely related to various aspects of economy, society and human life.This natural phenomenon has a profound impact on agriculture, transportation and other aspects of social production and life, sometimes even causes the phenomenon of autumn flood, which deserves full attention.Based on the basic understanding of the phenomenon in the 20th century, this paper compares and reviews the main research achievements of autumn rain in western China over the past 20 years from multiple perspectives.First of all, the spatial distribution range and temporal extent and precipitation intensity of autumn rain in West China are thoroughly explored, quantitative criteria and indexes such as ARI (Autumn Rain Index), DARI (Daily Autumn Rain Index) and MARI (Modified Autumn Rain Index)are also proposed.In addition to this, the significant interannual differences, the "positive - negative - positive" interdecadal variations and the 4~8 years cycle of autumn rain in western China fully demonstrate its complexity and inhomogeneity.Secondly, the different but important influences of atmospheric circulation systems at low, middle, and high latitudes, tropical sea temperature forcing including Pacific Ocean, Indian Ocean, and Atlantic Ocean as well as the Qinghai-Xizang (Tibet) Plateau effect and other aspects on the autumn rain in western China are pointed out.These different factors all play significant roles in the evolution of the phenomenon, but the mechanisms are different.This leads to the recognition of the significance of the multi-system and multi-factor synergistic effect on the anomalous evolution of autumn rain in western China, which enriches the understanding of the autumn rain and its impact.Finally, according to the current cognition of autumn rain in western China, the main problems that exist in the combination of different monsoon systems like Indian monsoon, East Asian monsoon and Plateau monsoon, cold and warm air currents, evolution causes, weather processes, night rain characteristics, regional responses to the global warming and other aspects are pointed out.These problems highlight the challenges that researchers face in studying this complex phenomenon.However, despite the challenges, there are several promising areas for future research.The main development trend in the future about the research of autumn rain in western China is the comprehensive and elaborate analysis of the multi-scale synergy of autumn rain in western China and its physical mechanism under the complex and important topography of Qinghai-Xizang (Tibet) Plateau.

  • Influence of Different Development Periods of the Strong and Weak South Asian Monsoon on the Vertical Circulation over the Qinghai-XizangTibetanPlateau
  • Yufei PEI, Minhong SONG, Shaobo ZHANG
  • 2023, 42 (6): 1402-1415. DOI: 10.7522/j.issn.1000-0534.2023.00022
  • Abstract (1987) PDF (8435KB)(114)
  • In order to explore the role of the changes in the strength and weakness of the South Asian monsoon on the vertical circulation of the Qinghai-Xizang (Tibetan) Plateau, the South Asian monsoon index WYI was calculated using the high-resolution JRA55 reanalysis data for the past 30 years from 1990 to 2019 and the strong and weak years of the South Asian monsoon were selected, and the effects of the changes in the strength and weakness of the South Asian monsoon on the vertical circulation of the Qinghai-Xizang (Tibetan) Plateau were analyzed by comparing the three different periods of the pre-monsoon outbreak, outbreak period and late outbreak.The following main conclusions were obtained: (1) The strength and extent of updrafts on the southern side of the plateau in May in WYI strong years are greater than in weak years, the intensity of updrafts on the main and southern sides of the plateau increases in July, and the difference between strong and weak years is not obvious.(2) In May and October, both mass and energy converge to the plateau from the south and north sides of the plateau, while in July, it turns to dissipate mass and energy from the plateau to the north and south sides.the intensity of the upper-level radiation dispersion in the south side of the plateau in the WYI strong year is greater than that in the weak year, and the difference of the irradiation intensity in the lower level is smaller.The difference in the intensity of energy and mass transfer between WYI strong and weak years is greatest in May and least in July.(3) In the WYI strong year, the 100 hPa South Asian high pressure shifts to the western type in October, and the 500 hPa West Pacific subalpine lifts northward, so the wind field on the southern side of the plateau shifts and raises the high altitude temperature, while in the WYI weak year this phenomenon occurs in May, indicating that the South Asian monsoon changes the horizontal circulation situation at high altitude and thus affects the vertical circulation of the plateau.The surface temperature of the main body of the plateau in May, July and October in WYI strong years is greater than that in weak years, indicating that under the influence of the warm and humid airflow brought by the South Asian monsoon, the updraft from the southern side of the plateau lifts to the plateau, and the surface temperature of the plateau increases significantly, and the surface heat of the plateau increases which in turn affects the vertical circulation of the plateau.

  • Multi-Scenario Projection of Future Precipitation over the Qinghai-XizangTibetanPlateau Based on CMIP6 Model Assessment Results
  • Boyuan LI, Qin HU
  • 2024, 43 (1): 59-72. DOI: 10.7522/j.issn.1000-0534.2023.00029
  • Abstract (1964) PDF (9440KB)(110)
  • As a climate-sensitive region, precipitation over the Qinghai-Xizang (Tibetan) Plateau significantly impacts the water cycle and the climate of East Asia.Therefore, it is important to study its changes.Precipitation is an important variable in the global hydrological cycle and one of the major climate systems affected by climate change.To investigate the ability of the global climate models to simulate precipitation over the Qinghai-Xizang (Tibetan) Plateau and examine possible changes in future precipitation under the new model and scenarios, this paper uses the latest monthly precipitation data from the 31 climate models of the Coupled Model Intercomparison Project 6 (CMIP6) and the CN05.1 precipitation observation data set provided by the National Climate Center to evaluate the ability of the CMIP6 model to simulate precipitation over the Qinghai-Xizang (Tibetan) Plateau.Furthermore, better models are selected to project the future precipitation of the Qinghai-Xizang (Tibetan) Plateau under different Shared Socioeconomic Pathway (SSP) scenarios.The results show that the model distribution of observed precipitation over the Qinghai-Xizang (Tibetan) Plateau from 1995 to 2014 is characterized by a decrease from southeast to northwest and a summer precipitation concentration.Most of the models can simulate the precipitation distribution and seasonal trend, but almost all of them overestimate the precipitation phenomenon, and the average precipitation of multiple modes is 102% higher than that observed.In general, the latest model of CMIP6 has a poor ability to simulate precipitation over the Qinghai-Xizang (Tibetan) Plateau, and the average relative deviation index of the model from the observation is 102%, indicating that most of the models are not satisfactory, and EC-Earth3-Veg-LR, MPI-ESM1-2-LR, EC-Earth3-Veg, and MRI-ESM2-0 are selected as the better modes after quantitative analysis of all the models, which can roughly reflect the precipitation characteristics of the Qinghai-Xizang (Tibetan) Plateau.Climate models show the slowest increase of precipitation over the Qinghai-Xizang (Tibetan) Plateau under the SSP1-2.6 scenario and the fastest increase under SSP5-8.5.From SSP1-2.6 in the small radiative forcing scenario to SSP5-8.5 in the large scenario, the recent (from 2021 to 2040) precipitation increase on the plateau is difficult to find a large difference in each scenario, but there is a significant increase in the mid (from 2041 to 2060) and late (from 2081 to 2100) scenarios, indicating that carbon emission intensity has a small impact in the short term and a large impact in the long term.The future increase in precipitation mainly occurs in the area south of the Nianqing Tanggula Mountains, from a seasonal point of view, the summer increase is the largest, followed by spring and autumn, the smallest increase is in winter, so we should pay attention to the future summer and spring precipitation changes over the Qinghai-Xizang (Tibetan) Plateau and take coping measures.

  • Temporal and Spatial Variation Characteristics of Daytime and Nighttime Precipitation in Monsoon and Westerly Regions of the Loess Plateau from 1961 to 2020
  • qi REN, Yuanfa GONG, Xueyu LIU
  • 2023, 42 (6): 1444-1456. DOI: 10.7522/j.issn.1000-0534.2023.00009
  • Abstract (1888) PDF (10739KB)(157)
  • Based on the day and night precipitation data of 64 stations in the Loess Plateau of China from 1961 to 2020 from the National Meteorological Information Center, the Loess Plateau is divided into two regions (monsoon region and westerly region).The variation characteristics of daytime and nighttime precipitation days and precipitation in the two regions in two seasons (wet-season and dry-season) were analyzed using methods such as linear trend and t test.The main conclusions are as follows: There are significant seasonal differences in daytime and nighttime precipitation between the monsoon region and the westerly region of the Loess Plateau.The number of daytime and nighttime precipitation days in the wet-season (May-September) in the monsoon region accounts for 60% of the whole year, and the precipitation is more than 75%.In the westerly region, the proportion of daytime and nighttime precipitation in the whole year is nearly 70%, and the precipitation is more than 80%.The Loess Plateau tends to get wet in the westerly area and dry in the monsoon area.Among them, the most prominent feature is that in the westerly region, The number of stations which measured increase in daytime accounts for 77.8% of the total.in the wet-season, and more than 50% in the dry-season.In the monsoon area, the number of stations in daytime and nighttime which measured decrease in precipitation days and precipitation account for more than 80% and 50% respectively in the wet-season, and more than 95% and 80% respectively in the dry-season.

  • Comparative Analysis of Convection Permitting Model and Cumulus Parameterization for Simulation of Summer Precipitation over Qinghai-XizangTibetanPlateau
  • Ying CHEN, Xianyu YANG, Yaqiong LÜ, Jun WEN, Jianing ZHU
  • 2023, 42 (6): 1429-1443. DOI: 10.7522/j.issn.1000-0534.2023.00016
  • Abstract (1874) PDF (8759KB)(95)
  • The Qinghai-Xizang (Tibetan) Plateau is known as the Asian water tower.The change of its water resources has an important impact on the weather and climate in the lower reaches.Precipitation is a key role in the water cycle.Therefore, it is of great significance to accurately simulate plateau precipitation for water resources security in China.In recent years, some studies have found that the convection-permitting model (the cumulus parameterization scheme could be turned off when grid scale is less than 4 km) could improve the precipitation simulation over the Qinghai-Xizang (Tibetan) Plateau.However, the previous studies only selected 1~3 cumulus parameterization schemes for comparison.It is still unknown whether convection-permitting model is superior to any cumulus parameterization scheme.In this paper, the ability of nine cumulus parameterization schemes in WRF and convection-permitting model (CPM) in simulating the precipitation over the Qinghai-Xizang (Tibetan) Plateau in the summer of 2009 was evaluated.The results showed that the simulations overestimate the summer precipitation over Qinghai-Xizang (Tibetan) Plateau in 2009, and the error was about 0.4~2 mm·d-1.The over simulation of CAPE and latent heat flux in Qinghai-Xizang (Tibetan) Plateau may be one of the reasons for the overestimations.Among all simulations, the G3 cumulus parameterization scheme has the best simulation of the mean precipitation the mean precipitation and the dinural cycles precipitation and it can can better capture the precipitation intensity, spatial distribution, precipitation area and diurnal cycles of the mean precipitation.CPM showed overall the second best precipitation simulation following G3 cumulus parameterization scheme, which can not effectively improve the simulation of diurnal cycles of precipitation, but can improve the simulation of precipitation frequency.In different plateau ecological regions, all simulations cannot reasonably simulate the precipitation in the desert area and the southern foot of the Himalaya, but compared with the cumulus parameterization schemes, CPM can greatly reduce the error in the desert area.In other regions, CPM and Tiedtke cumulus parameterization scheme performed well.Considering the mean precipitation and precipitation frequency, the CPM, Tiedtke and G3 cumulus parameterization scheme have the minimum simulation error for precipitation in different regions and intensity.Therefore, we recommend to adopt G3 or Tiedtke cumulus parameterization schemes in simulating summer precipitation over the Qinghai-Xizang (Tibetan) Plateau, and when the computational resources are allowed, the high-resolution CPM can be considered to improve the precipitation frequency simulations.

  • A Comparative Study on the Impact of MWHS-2 and MHS Data Assimilation on the Simulation of Rainstorm in the Three Rivers Source Area
  • Xu CHEN, Lei WANG, Xiehui LI, Haobin ZHONG, Xuhui DENG
  • 2023, 42 (6): 1386-1401. DOI: 10.7522/j.issn.1000-0534.2023.00024
  • Abstract (1869) PDF (6056KB)(86)
  • Based on the mid-scale WRF (Weather Research and Forecasting) numerical model, this study uses the direct assimilation module data from the FY-3C satellite MWHS-2 (Micro-Wave Humidity Sounder 2), and the WRF-3DVAR (Three Dimensional Variation) method to conduct assimilation comparison experiments on two precipitation processes in the Three Rivers Source area.Moreover, this study extensively compares the effects of two assimilation data sets on simulation results: data from the MWHS-2 (microwave humidity instrument carried by FY-3C) and data from the MHS (Microwave Humidity Sounder) carried by NOAA-18 (National Oceanic and Atmospheric Administration-18).Results of the study show consistent simulation results for MWHS-2 and MHS data assimilation.For instance, regardless of whether assimilation is conducted or not, the simulated precipitation range is overestimated for precipitations less than 30 mm.However, the simulated range and amount are underestimated for precipitations higher than 30 mm.Furthermore, data assimilation strengthens the 500 hPa southwest wind field, increases the intensity of water vapour transport, shifts the high-altitude trough to the southwest, and strengthens the 300 hPa wind field disturbance, all of which increase the precipitation range above 30 mm and, to a certain extent, improve the precipitation level results.However, compared to the actual situation, the precipitation area is biased southward.Satellite data assimilation significantly improves the range of the water vapour flux field and specific humidity field precipitation areas, but its effects on the intensity improvement are not obvious.At the same time, changes in the water vapour flux field and specific humidity field change the precipitation forecast area and intensity.As for the temperature field, the WRF simulation includes significant errors.Satellite data assimilation shows a certain improvement effect on the temperature field and a more significant improvement effect on the humidity field.In other words, MWHS-2 or MHS satellite data assimilation improves the precipitation forecast in the Three Rivers Source area.These conclusions provide significant guidance for improving the precision of precipitation forecasting in the Three Rivers Source area.

  • Influence of Developing Phase of Eastern Pacific El Niño Events on the Autumn Extreme Precipitation in China
  • Yuli PU, Juan FENG, Jianping LI
  • 2023, 42 (6): 1457-1467. DOI: 10.7522/j.issn.1000-0534.2023.00004
  • Abstract (1854) PDF (7905KB)(120)
  • Using the daily surface precipitation data and NCEP/NCAR monthly reanalysis data over the period of 1961 -2020, the impacts and possible physical mechanism of the developing phase of eastern Pacific El Ni?o on the autumn extreme precipitation in China were examined.The results indicated that the eastern Pacific El Ni?o events exhibit significant impacts on the extreme precipitation over the central and southern China during the developing autumn, resulting in increased extreme precipitation in southern China and decreased extreme precipitation in central China.The involved physical process is explored.The result indicated that when the eastern Pacific El Ni?o is in the developing autumn, significant positive sea surface temperature anomalies (SSTA) are seen in the central and eastern Pacific, which are associated with anomalous ascent in the tropical central and eastern Pacific and anomalous sinking in the western Pacific.Associated with the SSTA, southern China is controlled by anomalous convergence, which creates favorable dynamic conditions for precipitation.In addition, anomalous anticyclonic circulation is observed from the South China Sea to the western Pacific, and the water vapor transport via the southwest flow is enhanced, which promotes the occurrence of extreme precipitation in southern China.As to the central China, however, it is characterized with anomalous northerlies wind and water vapor divergence, which is not conducive to the occurrence of precipitation.These results provide scientific clues for understanding the physical mechanism of extreme precipitation events in eastern China.

  • The Impact of Assimilating Himawari-8 Radiance Data on the Prediction of a Severe Storm over Sichuan-Chongqing Region
  • Hao LIANG, Dongmei XU, Aiqing SHU, Xuewei ZHANG, Lixin SONG
  • 2023, 42 (6): 1478-1491. DOI: 10.7522/j.issn.1000-0534.2022.00112
  • Abstract (1847) PDF (14688KB)(109)
  • Himawari-8 is a new generation of stationary orbit imager, AHI (Advanced Himawari Imager) onboard is able to is able to provide observations with high spatial and temporal resolution to detect weather systems continuously over Sichuan - Chongqing Region.In this study, a numerical simulation is conducted for a severe regional storm event over Sichuan-Chongqing region on April 19, 2019 based on the weather Research and Forecasting (WRF) model.Furtherly, several radiance data assimilation experiments were performed for the storm with the WRF data assimilation (WRFDA) system from Himawari-8 AHI water vapor channels.Infrared radiance quality control and cloud detection procedures are conducted firstly.Cycling data assimilation schemes are further designed to investigate the impact of assimilating AHI radiance on the analyses and prediction of the weather system.The results show that the simulated brightness temperature of AHI water channels based on the radiative transfer model of CRTM in the analysis is more consistent with the observed brightness temperature than the those simulated from the background.It is also found that that assimilation of Himawari-8 AHI water vapor channels contributes to better describing the model initial conditions including the wind field, the water vapor field, and the radar reflectivity on multiple levels.Compared to the control experiment without any data assimilation, the forecast skill is enhanced in terms of predicting the main patterns of the precipitation after assimilating the AHI water vapor radiance data.To be specific, the assimilation experiment could capture the position of the main rainband and the center of heavy precipitation better.Through the AHI water vapor data assimilation, the heavy precipitation centers that are missed in the control experiment are successfully predicted.In addition, AHI radiance data assimilation experiment effectively improves the overestimated heavy precipitation from the control experiment in eastern Sichuan and southeastern Gansu for both the range and intensity.This study aims to provide the useful reference for the pretreatment and assimilation of geostationary infrared radiance data in the rainstorm system in numerical models over Sichuan-Chongqing Region.

  • Action Mechanism of Tibetan Plateaus Eastern Slope Topography on the PLV Affecting Yunnan Precipitation
  • Yu HE, Li ZHU, Guoping LI, Jiaxu XIE, Wenqian MA, Li TAO, Wanchen ZHANG
  • 2024, 43 (1): 42-58. DOI: 10.7522/j.issn.1000-0534.2023.00037
  • Abstract (1841) PDF (9357KB)(194)
  • Using radiosonde and ground mapping data from conventional observations, FNL analysis data (1°×1°) and quality controlled hourly precipitation data of Yunnan regional automatic station, diagnosed the function of the Qinghai-Xizang Plateau’s eastern slope topography in the PLV (plateau vortex) affected precipitation in Yunnan during 2-3 July 2017.While the latest WRFv4.0 numerical model is used to conduct the topographic sensitivity test of this process.The results show that PLV which generated in the Yajiang region of Sichuan province (NO.C1735) is an important system influenced on this heavy rainfall in Yunnan; This low-vortex system maintain warm core structure in the middle and high altitude during the process period, corresponding with remarkable alternately distribution of ascending and descending movements; Distribution of process accumulated rainfall present two obvious NW-SE rain belts parallel to the mountain trend and the precipitation on the rain belt have intensity interlaced fluctuation characteristics; The heavy rainfall mainly occurred within two periods: one from afternoon to evening and other at the first half of the night, and all located besides the terrain slope (the east and south slopes), especially in areas with steep terrain, large slopes, and trumpet-shaped topography, and then propagates downstream alone with the PLV; The South Asian High, northwest divergent airflow, Western Pacific subtropical high and Yunnan-Myanmar high provides favorable upper flow field for the eastward movement and development of the PLV, besides the position of 500 hPa positive vorticity and 700 hPa water vapor flux convergence can well indicates the heavy rainfall area; There exist β-mesoscale gravity wave during the period of precipitation, which stimulated by the Qinghai-Xizang Plateau’s eastern slope, and propagate between 300~200 hPa; Non geostrophic equilibrium motion and vertical wind shear at high-altitude are beneficial to the occurrence and propagation of gravity wave; The gravity wave propagate downstream before the PLV and precipitation, its wave ridge corresponds to the upward motion and divergence center, whereas the wave trough corresponds to the descending motion and convergence center, the heavy precipitation and the wave ridge are all located at the southwest side of PLV, the area of strong convergence and upward movement; After reduced the terrain height, its mechanical blocking and lifting effect weakened, the gravity wave and PLV disappears, leading to significant changes in the intensity and spatial distribution of the rain belt; Thus, the topography of the eastern slope of the Plateau plays important role both on the formation and development of PLV and precipitation in Yunnan under the influence of PLV.

  • A Comparative Study on the Summer Raindrop Size Distribution Among Areas over the Central and Eastern Qinghai-XizangTibetanPlateau and the Western Sichuan Basin
  • Yanxia LIU, Jun WEN, Xiaolin XIE
  • 2024, 43 (1): 28-41. DOI: 10.7522/j.issn.1000-0534.2023.00033
  • Abstract (1836) PDF (7079KB)(153)
  • To promote the understanding of precipitation microphysical characteristics and differences in the central and eastern Qinghai-Xizang (Tibetan) Plateau and the Sichuan Basin, disdrometer measurements collected at Naqu, Yushu, Linzhi, Batang, Luding, and Chengdu from July to August 2019 and 2020 are utilized to comprehensively investigate the characteristics and differences of raindrop size distributions (RSDs) among the six different areas.Meanwhile, local empirical relations between the Gamma shape parameter and slope parameter and between the reflectivity factor and rain rate are proposed and compared.The results show that RSDs in the basin and adjacent areas (Chengdu and Luding) are generally wider and have higher number concentrations of medium-to-large raindrops (diameter ≥1.0 mm) than those in the plateau areas (Naqu, Yushu, Linzhi, and Batang) due to the contribution of more strong convective precipitation.In contrast, RSDs in the plateau areas are narrower and possess higher number concentrations of small raindrops (diameter <1.0 mm) due to more occurrences of stratiform and weak-convective precipitation.RSDs gradually become wider with higher number concentrations as the increase of rainfall intensity both in the six observation areas.The RSD differences among the six observation areas can also change with the rain rate.Specifically, when the rain rate exceeds 0.1 mm·h-1, the increase of the number concentration of small raindrops with increasing rain rate is significantly greater in Naqu and Linzhi than in other areas, and can gradually exceed that in Chengdu.When the rain rate exceeds 5 mm·h-1, the differences in the number concentrations of medium-to-large raindrops between Chengdu and Luding and other plateau areas also gradually become larger.With the same shape parameters, the slope parameters in Chengdu and Luding are smaller than in other areas, indicating that they possess a slower decreasing rate of raindrop number concentration with increasing particle size than that in other plateau areas.Under the same radar echo intensities (reflectivity factor), rain rates of stratiform precipitation in Naqu and Linzhi are greater than in other regions.The rain rate of convective precipitation in Linzhi is also greater than that in other areas when the radar echo is below 40 dBZ, but the rain rate of convective precipitation in Naqu can be smaller than that in other areas when the radar echo is greater than 40 dBZ.

  • Water and Heat Flux Characteristics of Alpine Wetland and Alpine Steppe under Grazing Enclosure on the Northern Xizang
  • Zhuangzhuang WANG, Yaqiong LÜ, Da WEI, Yahui QI, Xiaodan WANG
  • 2023, 42 (6): 1416-1428. DOI: 10.7522/j.issn.1000-0534.2023.00005
  • Abstract (1824) PDF (6132KB)(71)
  • Grazing enclosure has been extensively employed as a direct and effective management measure for grassland restoration on the Qinghai-Xizang Plateau.Enclosures significantly increased vegetation coverage and affected the water and heat exchange between the land surface and the atmosphere.However, there is still a lack of quantitative research on how enclosures regulates water and heat fluxes in typical alpine ecosystems.Based on continuous data observed from eddy covariance system from July 2019 to June 2021 at alpine steppe and alpine wetland of the Northern Xizang, the changes of surface energy flux after enclosure was analyzed by using the eddy covariance method.The results show that: The water and heat fluxes in alpine steppe and alpine wetland shows significant unimodal diurnal variations.The exchange of land-atmosphere in alpine steppe is mainly dominated by sensible heat (Bowen ratio: 1.60) except in Summer, while wetland mainly transfers energy to the atmosphere by latent heat (Bowen ratio: 0.31) whole year.Grazing enclosure decreased the surface fluxes in alpine steppe, the sensible heat flux reduced by 5.99 W·m-2 and the latent heat flux increased by 4.84 W·m-2.Grazing enclosures increased the surface fluxes in alpine wetland, the sensible and latent heat raised by 3.04 W·m-2 and 30.95 W·m-2, respectively.The daily and average sensible and latent heat fluxes decreased in alpine steppe but increased in alpine wetland.The effect of enclosure on surface energy fluxes was stronger during the day and weaker at night.The collected literature data demonstrated that fencing decreased soil temperature and increased soil water holding capacity.Given the data of soil temperature, soil moisture, latent heat flux, and sensible heat flux, our study shows the cooling potential of enclosure on alpine steppe and alpine wetland.

  • Mesoscale Numerical Simulation and Cloud Microphysical Characteristics of the Warm Zone Blizzard in Northern Xinjiang
  • Anbei LI, Chenxiang JU, Yaman ZHOU, Man LI, Ruqi LI
  • 2024, 43 (1): 127-140. DOI: 10.7522/j.issn.1000-0534.2023.00040
  • Abstract (1694) PDF (12108KB)(118)
  • The warm zone blizzard are both infrequent and highly destructive, making their accurate prediction a challenging and crucial focus.This study utilized four distinct cloud microphysics schemes (Lin, Thompson, WDM6, and WSM6) within the WRF mesoscale model to conduct a numerical simulation of a typical warm zone blizzard process in the northern Xinjiang in the middle of November 2016.The research objectives encompassed the evaluation of the model's capacity to simulate the warm zone blizzard, the selection of an optimal parameterization scheme, an analysis of the vertical distribution and evolution of hydrometeors during the snowstorm, and an exploration of the developmental patterns of related mesoscale systems contributing to the snowstorm.The analysis yielded the following key findings: (1) Among the diverse cloud microphysics parameterization schemes tested, the Lin scheme demonstrated the most favorable performance, effectively simulating snowfall magnitudes, spatial distributions, and trends.(2) In the cloud, all kinds of water condensate particles are active in the lower and middle troposphere, with graupel and snow being the most.Ice crystals, snow, cloud water and graupel particles are distributed from the upper layer to the lower layer.Near the windward slope of Altai Mountain is the center of the large concentration of each water condensate particle.The vertical alignment of the high value center of the four kinds of cloud water condensate particles in the strong snowfall area is conducive to the transformation of each particle.(3) High-humidity systems upstream moved westward, with the intensification of low-level southward jet streams resulting in pronounced moisture convergence.The western foothills of the Altai Mountains acted as a barrier, promoting moisture convergence by blocking the windward side; The low-level southerly jet also provides a continuous updraft and unstable condition for the generation of the blizzard.Strong snowfall is located in a wide updraft area between two groups of secondary circulations.The explosive growth of vertical movement is conducive to triggering the release of unstable energy, providing strong dynamic lifting conditions for the development and maintenance of the blizzard.

  • Evaluation of Winter Near-surface 2 m Temperature around the Hengduan Mountains in Southwest China Simulated by ECMWF
  • Shimei WU, Na TANG, Yuqi LIANG, Xuyang OU, Haijie LI, Haoming CHEN
  • 2024, 43 (1): 88-98. DOI: 10.7522/j.issn.1000-0534.2023.00049
  • Abstract (1677) PDF (7805KB)(107)
  • Based on the hourly product of CLDAS (CMA Land Data Assimilation System) in 2021, this study is to evaluate the prediction capacity of the global high-resolution deterministic numerical prediction product ECMWF (European Center for Medium Weather Forecasting) for winter mean near-surface 2 m temperature of complex terrain region around the Hengduan mountains in southwest China by starting from winter average temperature, daily variation, and diurnal temperature range.And this study compares the temperature deviation characteristics of near-surface 2 m temperature in different topographic regions by distinguishing between high terrain region (the Western Sichuan Plateau) and low terrain region (the southern Sichuan Basin).The results show that: (1) The ECMWF model can reasonably predict the spatial distribution characteristics of the winter mean near-surface 2 m temperature around the Hengduan mountains in southwest China, but the deviation distribution is related to the terrain height.With the increase of the terrain height, the prediction deviation tends to increase.(2) The ECMWF model well reproduces the daily variation characteristics of winter mean near-surface 2 m temperature around the Hengduan mountains in southwest China, with the peak time appearing at 14:00 (Beijing Time).The prediction deviation of temperature at various times varies at different terrain heights.The maximum negative deviation of the western Sichuan Plateau and the Hengduan mountain regions occurs in the afternoon, while the maximum negative deviation of the south Sichuan Basin occurs in the morning.At the same time, the prediction deviation at each moment in high terrain areas is greater than the prediction deviation at each moment in low terrain areas.(3) The ECMWF model can reasonably predict for the spatial distribution of winter mean near-surface 2 m temperature over different terrain at various times during the day, but the deviations have diurnal variation characteristics.Especially in the high terrain region of the Hengduan mountain regions, there are different characteristics of cold and warm deviations at various times.(4) The area with large forecast bias of diurnal temperature range is generally the area with frequent Quasi-stationary front activities in Kunming.For the days (A total of 90 days, from December 1, 2021 to February 28, 2022) with large diurnal temperature range, the prediction deviation of winter mean near-surface 2 m temperature in this area is greater than the days with small diurnal temperature range.What’s more, the prediction deviation of diurnal temperature range is relatively unstable in the area with large forecast bias of diurnal temperature range.

  • Analysis of the Dynamical Structure and Genesis of Two Different Life-History Eastward Moving Plateau
  • Nini TU, Shuhua YU, Yueqing LI
  • 2024, 43 (1): 73-87. DOI: 10.7522/j.issn.1000-0534.2023.00048
  • Abstract (1657) PDF (24025KB)(722)
  • The NCEP reanalysis data were utilized to diagnose the structural characteristics and evolutionary mechanisms of two plateau vortex processes that moved eastward out of the plateau on June 25-27, 2008 and June 4-10, 2013.The data were also used to explore the structural characteristics of the two long and short track plateau vortex processes and the influencing factors that caused their different life histories.The results show that: (1) During the Zhaduo vortex activity with a short path, the South Asian high pressure is flattened, the upper-level jet stream is southward and the plateau vortex moves out of the plateau in the slump trough.During the Qumalai vortex activity with a long path, the South Asian high pressure has a north arch, the plateau vortex is in the northwest airflow under the South Asian high-pressure ridge, the subtropical high is southward and the plateau vortex is strengthened with the eastward movement of the trough, accompanied by the eastward movement of the southwest vortex.(2) The two plateau vortex processes exhibit distinct structural characteristics, especially when the Zhaduo vortex is strengthened on the plateau and when the Qumalai vortex is strengthened again after coupling with the southwest vortex.The former vortex is in the deeper positive vorticity and upward motion layer at 600~350 hPa and also has the structural characteristics of strong divergence in the upper troposphere.The latter has the structural characteristics of high, middle, and low positive vorticity penetration in the troposphere, ascending movement in the troposphere, and weak divergence in the troposphere.(3) The diagnosis of total vorticity budget shows that the change of divergence term plays a decisive role in the change of total vorticity variability of low vortices.The strength change of Zhaduo vortex is consistent with the divergence term change.The influence of vertical transport term and horizontal advection term are strengthened during the accompaniment of Qumalai vortex with the southwest vortex.(4) Regarding the budget analysis of the 500 hPa positive vorticity variability in the central region of the vortex, the results show that when there is no activity of the southwest vortex, the plateau vortex contributes mainly to the 500 hPa positive vorticity variability of the plateau vortex due to convergence.When there is activity of the southwest vortex, the vertical transport of positive vorticity becomes more important with the superposition and companionship with the southwest vortex in the vertical direction.

  • Study on Precipitation Observation and Retrieval Methods of X-band Phased Array Polarization Weather Radar in Motuo, Xizang
  • Haoran CHEN, Fei GENG, Liping LIU, Hua YANG
  • 2024, 43 (1): 99-113. DOI: 10.7522/j.issn.1000-0534.2023.00039
  • Abstract (1633) PDF (8650KB)(112)
  • The variation in precipitation in Motuo is closely associated with the transport of water vapor from the India Ocean and the Bay of Bengal to inland China, the Asia summer monsoon, and the progression of the rain band in eastern China.A rain band with an average annual precipitation of more than 2000 mm has been formed due to the interaction of the distinctive topography of Motuo and the southwest air flow.However, it has been challenging to observe precipitation in Motuo due to the peculiar topography, insufficient electricity, and inadequate traffic conditions.An X-band dual-polarization phased array radar (XPAR) is installed during the Second Qinghai-Xizang Plateau Scientific Expedition and Research Program.The advanced dual-polarization phased array radar is used to continuously observe the precipitation in Motuo and is of great significance to the research of the local ecological environment and cloud water resources, and the impact on downstream.Based on XPAR data collected for the period from June to August 2020, we selected the radial precipitation echoes using a statistical method, and after integrating the precipitation echoes, we created the hybrid elevation angle that tallied with the topography of Motuo.Using DSD data from Motuo in 2019, we calculated radar parameters and obtained the localized QPE (Quantitative Precipitation Estimation) formulas of X-band weather radar.We selected three processes of precipitation with different cumulative precipitation, duration, and average rain rate from July to August 2020, calculated Φ DP (Differential Propagation Phase Shift) using the linear programming method, K DP (Differential Propagation Phase Shift Rate) using the ordinary least square method, and corrected Z H (Reflectivity Factor) using the “ZPHI” rain profiling algorithm.Using Z H and K DP as thresholds, we estimated precipitation piecewise utilizing RZ H) and RK DP), and contrasted results with the QPE results from the RZ H) and RK DP) methods, respectively.And explored the relationship between precipitation distribution and the topography of Motuo based on the QPE results.The quality of Z H and K DP had been significantly improved.The hybrid elevation angle constructed using a statistical method had a larger echo area than the hybrid elevation angle constructed using STRM1 v3.0 data.The PPI (Plane Position Indicator) diagrams of three precipitation (radar parameters at typical times, and average radar parameters) processes can show the relationship between the variation in precipitation and the topography of Motuo.The QPE formulas and Piecewise Estimation Method (PEM) used in the research functioned well, and each evaluation parameter performed well.The following conclusions are drawn: (1) The hybrid elevation angle constructed using the statistical method outperformed the hybrid elevation angle constructed using topography data in QPE, due to the drastic variation of the topography around the XPAR in Motuo; (2) The data quality control method, the QPE formulas, and the PEM utilized in the research all performed well at precipitation retrieval.The estimation error of the QPE results was significantly reduced, without causing significant changes in CC and RMSE; (3) Precipitation in Motuo may occur and grow as a result of the lifting of the southwest air flow by northern slopes of the valley.Clouds with higher rain rates and smaller drops are found near the level bottom of the valley.

  • Analysis of Flood Season Precipitation and Extreme Precipitation in Gansu Province Based on Data from Different Types of Meteorological Stations
  • Feng FANG, Jing WANG, Weiping LIU, Youheng WANG, Xin WANG, Jingjing LIN, Xing WANG
  • 2023, 42 (6): 1468-1477. DOI: 10.7522/j.issn.1000-0534.2023.00008
  • Abstract (1468) PDF (3894KB)(181)
  • In this paper, the data quality control of the flood season precipitation and extreme precipitation of the regional meteorological stations and national meteorological stations in Gansu Province from 2011 to 2020 has been carried out, and 1253 regional meteorological stations and 75 national meteorological stations have been selected to analysis the precipitation characteristics.The results show that the average precipitation amount of the regional meteorological stations in Gansu Province is very close to that of the national meteorological stations, and there is no significant difference.The average precipitation of the regional meteorological stations in flood season in Gansu province is 382.9 mm, and that of the national meteorological stations is 379.7 mm.The average monthly precipitation of regional meteorological stations distributes from 31.7 mm to 87.1 mm, and that of national meteorological stations distributes from 30.4 mm to 86.4 mm.However, there are significant differences in the extremes of precipitation between the two types of meteorological stations.The maximum of total precipitation at regional meteorological stations in flood season even reaches 917.5 mm, the maximum monthly precipitation reaches 776 mm, and the maximum number of rainstorm days reaches 46 d·(10a)-1.However, those of national meteorological stations is 710.7 mm, 541 mm and 17 d·(10a)-1, respectively.The spatial locations of precipitation maxima of regional meteorological stations and national meteorological stations are close to each other, but the numerical values of regional stations are significantly higher than those of national stations.The spatial trends of precipitation at the two stations are very consistent, and the correlation coefficient of flood season precipitation of two types stations is 0.95, the correlation coefficient of monthly extreme precipitation is 0.92.Moreover, regional meteorological stations show many higher and less value centers of small patches than national stations; the spatial precipitation difference between the two types of meteorological stations are clearly in the east and south of Gansu Province.Overall, the regional meteorological stations describe the precipitation characteristics of Gansu Province in a more detailed way.More extreme precipitation events are monitored in those regions with complex terrain, and the extreme value of precipitation is larger than that of national meteorological stations.The rainstorm and flood disaster prevention in these regions should be based on the data of regional meteorological stations to enhance the disaster risk prevention ability.

  • Review on Developments and Improvements in Vertical Coordinates for Numerical Prediction Models
  • Rui CHENG, Rucong YU, Youping XU, Jing HUANG, Xiaojing SHEN
  • 2024, 43 (1): 16-27. DOI: 10.7522/j.issn.1000-0534.2023.00042
  • Abstract (1445) PDF (846KB)(101)
  • As we know, the atmosphere is mainly characterized by its baroclinicity and stratification.The vertical coordinate is crucial for the description of 3D atmospheric motion and thermal-dynamic condition of the static atmosphere.Furthermore, the vertical coordinate is foundation of numerical prediction model construction.Different atmospheric dynamic cores, such as height, pressure and potential temperature-based frames are usually established depending on different vertical coordinate modes.The development of vertical coordinates always contributes to major version update and considerable upgrade of the numerical prediction model.In this paper, we briefly review the history of vertical coordinates for the numerical model.Then, we mainly demonstrate the design art for hybrid vertical coordinates in some operational non-hydrostatic models at home and abroad.Additionally, this paper presents some suggestions on how to select model vertical resolution and prediction variables vertical distribution style.Finally, the progress on arrangement and application of the vertical coordinate for numerical prediction models is summarized and its development tendency is also illustrated.

  • Analysis of Water Vapor Transport Reduction in the Yarlung Tsangpo Grand Canyon Region: a Trajectory Tracking Approach
  • Dengxv ZHANG, Hongru YAN, Yunfei MIAO, Min ZHANG
  • 2024, 43 (1): 114-126. DOI: 10.7522/j.issn.1000-0534.2023.00050
  • Abstract (1349) PDF (3953KB)(117)
  • The Yarlung Tsangpo River Grand Canyon region serves as a main water vapor entrance for the Tibetan plateau.However, the region has been experiencing a persistent decline in both water vapor convergence and precipitation since 1979, which has an important impact on the water storage over the Tibetan Plateau.In order to investigate the reasons behind this reduction in water vapor transport in the area, ERA5 hourly reanalysis data were utilized to drive the LAGRANTO model to derive the backwards water vapor transport trajectories in the region during the boreal summer (June to August) of typical dry and wet years, facilitating a comparative analysis of alterations in moisture flux along these trajectories.It was found that the water vapor sources primarily originating from four oceanic regions: the Bay of Bengal in the southern plateau, the Arabian Sea on the southwest side of the plateau, the Indian Ocean around south of the equator, and the South China Sea.The water vapor transportation in these regions is predominantly governed by the South Asian and Indian summer monsoons and influenced by the Somalia cross-equatorial jet.By comparing the characteristics of water vapor transport trajectories in dry and wet years, it is evident that trajectory patterns remain largely unchanged, with the exception of the South China Sea source.Furthermore, moisture flux along these trajectories diminishes as elevation increases, and the moisture loss during wet years consistently proves to be lower than that during dry years.Additionally, the trajectories originating from the Bay of Bengal source are supplemented by water vapor from the ocean surface, resulting in significant increased water vapor flux in wet years.This finding is supported by comparing the evaporation, precipitation, and circulation fields between dry and wet years.Ultimately, during wet years, the moisture flux reaching the boundaries of the Yarlung Tsangpo Grand Canyon region surpasses that of dry years, notably marked by a particularly significant increase in moisture entering through the southern boundary.This highlights that the depletion processes during water vapor transport, in addition to contributions from moisture sources and the influence of large-scale monsoonal circulation, play a critical role in determining the moisture equilibrium within the Yarlung Tsangpo Grand Canyon region.