Plateau Meteorology

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28 December 2020, Volume 39 Issue 6   
  • Review of Climate Change and Its Environmental Influence on the Three-River Regions
  • Xianhong MENG;Hao CHEN;Zhaoguo LI;Lin ZHAO;Bingrong ZHOU;Shihua Lü;Mingshan DENG;Yumeng LIU;Guangwei LI
  • 2020 Vol. 39 (6): 1133-1143.  DOI:10.7522/j.issn.1000-0534.2019.00144
  • Abstract ( ) HTML ( ) PDF (2119KB) ( )
  • The Three-river sources regions （TRSR）， located on the Qinghai-Xiang Plateau （QXP）， are the source regions of Yangtze， Yellow and Lancang River.Under the background of global climate change， the QXP was considered as the “sensitive region” and the “promoter region” of climate change， which will definitely affect the regional climate， environment， and water resources on the TRSR.This paper reviews the facts of variations of climate， environment and water resources in the recent 5~6 decades.The main conclusions are as follows： （1） Air temperature increased on the TRSR with a trend of 0.33 ℃·（10a）-1， which is 1.2 times of the rate on QXP.（2） Precipitation increased on the TRSR with a trend of 6.653 mm·（10a）-1， but the trend was 71% of the QXP.（3） The minimum and maximum air temperature increased significantly， with the trend in the cold seasons higher than the warm seasons.（4） Snow days on the south of the TRSR increased， but decreased on the source region of the Yellow river.（5） Under the climate warming， the permafrost degraded， in combing with the precipitation enhancement， the lakes and the wetlands were developed.（6） Although precipitation on the TRSR enhanced， runoff shows different trends， with it increased on the sources of Yangtze river （the trend of runoff in Zhimenda station is 6.69×108 m3·（10a）-1）， and decreased on the Yellow river （the trend of runoff in Xiangda station is 1.1×108 m3·（10a）-1）.At last， the water cycle changes under the warming and its influences on water resources were discussed， according to which it is important to do more investigations on the multi-sphere interactions to distinct the contribution to water resources from climate change and human activities.These kinds of knowledge will benefit for the TRSR to adapt climate change and supply references for the TRSR park construction.
  • Vertical Characteristics on Temperature and Humidity of Surface Layer Air during Snow Processes in the Hinterland of Sanjiangyuan
  • Juan ZHANG;Weizhen WANG;Ji LIANG
  • 2020 Vol. 39 (6): 1155-1166.  DOI:10.7522/j.ssn.1000-0543.2019.00138
  • Abstract ( ) HTML ( ) PDF (5796KB) ( )
  • Snow is one of the biggest errors in the balance of water resources in the world.The rising and falling process of snow depth will change the interaction between the ground and the atmosphere.In this paper， based on the snow field observation station in Gande area in the hinterland of Sanjiangyuan， and using the air temperature and humidity at 2， 4， 8 and 16 m every 30-min， the radiation data at 2 m and the snow surface temperature， combined with the synchronous snow depth observation data， we analyzed the vertical variation characteristics of temperature and humidity in the near-surface layer during the two heavy snow cover processes from January to May 2018.The results show that： （1） In the period of rising snow depth， the phenomenon of inverse humidity appeared first and then inverse temperature appeared in February， but there was no phenomenon of inverse temperature and inverse humidity in April.During the period of rapid increase of snow depth， warm and wet phenomena appeared at the height of 4m in both processes.（2） During the period of falling snow depth， the phenomena of temperature inversion and humidity inversion appeared in both processes， and the occurrence time and fading time were inconsistent， and the phenomenon of temperature inversion first appeared after humidity inversion.During the two processes， the phenomenon of 4 m warmer appeared during the day and night when the snow depth increased， but only during the day when the snow depth decreased.（3） In the period of falling snow depth， the snow surface temperature is more sensitive to short-wave radiation than air temperature， and the correlation between snow depth and radiation is different at different depths.In February， the order of influencing factors of snow depth decline was snow surface temperature>short wave radiation>air temperature， while in April， the order was air temperature>snow surface temperature>short wave radiation.
  • Analysis of Simulated Temperature Difference between Lake Surface and Air and Energy Balance of Three Alpine Lakes with Different Depths on the Qinghai-Xizang Plateau during the Ice-Free Period
  • Juan DU;Lijuan WEN;Dongsheng SU
  • 2020 Vol. 39 (6): 1181-1194.  DOI:10.7522/j.issn.1000-0534.2019.00133
  • Abstract ( ) HTML ( ) PDF (6770KB) ( )
  • Lake-atmosphere temperature difference （?T） plays an important role in the heat exchange between lake surface and overlying atmosphere during the ice-free period.However， due to the difficulty of carrying out field observation experiments on the Qinghai-Xizang Plateau （QXP）， the characteristics of the ?T remains poorly understood.And also， there are few studies on the radiation and energy budget of the alpine lakes at present.In this study， the characteristics of ?T， radiation and energy balance at three larger and deeper alpine lakes with different depths （Ngoring， Bangong Co and Nam Co） were studied by using the China Meteorological Forcing Dataset （ITPCAS） and the one-dimensional lake module of the Community Land Model（CLM-Lake）.Verification of model results achieved with remote sensing data and observed data from meteorological station indicate that the lake model has a good ability in simulating the seasonal variations of the lake surface temperature on the QXP.As a result of the lower temperature and the stronger solar radiation caused by high altitude on the QXP， the ?T of Ngoring （23 m deep） and Nam Co （95 m deep） were always positive during the ice-free period and continued to increase from the late spring or early summer to the late autumn or early winter.Available observations and the simulations in our study showed that the Bangong Co lake， with a depth of 37 m， has a negative ?T in June and July， which may ascribed to a warmer and drier air in Bangong Co lake region in June and July， lead to a stronger evaporation over the lake surface， and more energy of the lake was released in the form of latent heat.As a result， the warming of the lake surface was weakened and slower than air temperature， eventually a negative ?T formed.This phenomenon is different from other lakes in QXP during the ice-free period where the ?T is generally positive.However， it should be noted that the observed lake water temperature at Bangong Co is 5 m below the lake surface and air temperature is over the land surface 10 km away from the lake， so more accurate data is needed for the further verification.The trend of the simulated sensible heat flux over surface of the three lakes was similar to that of ?T， and the simulated latent heat flux was positive all year round meaning that the lake was constantly sending water vapor to the atmosphere.
  • Spatial-Temporal Variation Characteristics and Climate Driving Force Analysis of Longbao Alpine Wetland in Recent 32 Years
  • Feifei SHI;Bingrong ZHOU;Liangdong YAN;Donglin QI;Bin QIAO;Mingming SHI;Qi CHEN
  • 2020 Vol. 39 (6): 1282-1294.  DOI:10.7522/j.issn.1000-0534.2019.00139
  • Abstract ( ) HTML ( ) PDF (5308KB) ( )
  • Wetland is a unique ecosystem formed by the interaction between water and land， which is extremely easy to be affected by the climate change.Taking Longbao， a typical wetland in source region of the Yangtze River， as the target domain， the study applied the random forests method to extract information about the surface type of Longbao from 1986 to 2017 and also analyzed the characteristics of spatial-temporal variations of it.Meanwhile， from a climate perspective， methods such as principal component analysis were employed to quantitatively identify the major climate drivers affecting the wetland evolution.At last， the study built a model for the response relation between the wetland area and the climate change， which could be utilized to predict the evolvement rule of wetland in the future.The following results are summarized： （1） In the past 32 years， there was a spatial nonuniformity in the features of Longbao wetland evolvement because of the long-term influence of terrain； there was a general downtrend in the time dimension， but a change from increasing to decreasing was presented near 2002.Wetland was usually in a steady succession with the Alpine meadow； （2） In the past 32 years， temperature， wind speed and evaporation of Longbao region was in a significant uptrend， while the increase of precipitation is not significant.That would certainly decrease the relative humidity and shorten the days with snow cover.Surface temperature was in a dramatic uptrend， therefore the maximum depth of frozen soil in this region was gradually becoming shallower year by year.In late 2002， an obvious warming and drying trend appeared in the Longbao region； （3） The evolution of the Longbao wetland area has a high response relationship with wind speed， temperature， surface temperature and relative humidity， respectively.
  • Evaluation of Simulated Performance of CLM4.5 in Alpine Meadow over the Qinghai-Xizang Plateau based on Measured Soil Properties
  • Youqi SU;Yu ZHANG;Minhong SONG;Shaoying WANG;Lunyu SHANG;Ke ZHOU
  • 2020 Vol. 39 (6): 1295-1308.  DOI:10.7522/j.issn.1000-0534.2019.000136
  • Abstract ( ) HTML ( ) PDF (8844KB) ( )
  • In order to improve the simulation ability of the land surface model CLM4.5（Community Land Model） to the alpine meadow on the Qinghai-Xizang Plateau， we used the observation data from June to September of three typical alpine meadow research stations， i.e.Maqu Station， Arou Station and Naqu Station， especially the measured soil properties， to run a single-point numerical simulation test of alpine meadow in summer half year， which provides a basis for improving the parameterization schemes of the model.The main conclusions are as follows： （1） CLM4.5 model can well reproduce the seasonal changes of soil temperature and moisture， radiation flux and surface energy flux on the underlying surface of alpine meadow.The simulation results after modifying soil properties was obviously better than that before modification， but there was still some deviation from the observed.（2） After modified soil properties， the simulation of soil moisture of each layer at Maqu Station and Naqu Station was closer to the observed， and the shallow soil moisture at Arou Station was better than that at deep layer.After modified soil properties， although the model’s land surface conditions were closer to the actual， the improvement of the simulated soil temperature was not obvious.（3） Although the simulated values of reflected radiation before and after modification of soil properties were low at all three stations， the simulated values after modification of soil properties were better than those before modification.However， there was no significant improvement in the simulation of surface long wave radiation， and the correlation between the simulated values and the observed values at Arou Station was higher and the deviation was smaller.（4） The sensible heat flux simulation values of CLM 4.5 model for each station was higher， and after modified soil properties， it was closer to the observed.After modified soil properties， the simulated and observed latent heat flux at Maqu and Naqu station were closer.
  • Study on Information Extraction Method of Alpine Wetland in Qinghai- Xizang Plateau based on Remote Sensing Data of GF-1 Satellite
  • Shuaiqi ZHANG;Bingrong ZHOU;Feifei SHI;Qi CHEN;Shulan SU
  • 2020 Vol. 39 (6): 1309-1317.  DOI:10.7522/j.issn.1000-0534.2019.00131
  • Abstract ( ) HTML ( ) PDF (3877KB) ( )
  • The Qinghai-Xizang Plateau contains the most typical and diverse types of alpine wetlands.In order to explore the degradation of alpine wetlands， it is necessary to extract accurate information of alpine wetlands.Research methods Selects growing season images of GF1-WFV in Maduo County and uses hierarchical classification method.Chose the 50-segmentation scale to segment the image， and then the wetlands are identified by means of single band threshold and slope threshold.Comprehensive uses of these methods， including spectral relation method， mixed water index method， normalized differential water index method and single band threshold method.Finally， the information and distribution status of the alpine wetland types in Maduo County， Qinghai Province were obtained， combines with non-growing season images， according to the class III classification standard of alpine wetland remote sensing classification system.Research results Firstly， the sample points were randomly selected and the accuracy of the image was evaluated by the method of confusion matrix.The classification accuracy of this study reaches 88.59%， and the Kappa coefficient is 0.8637， the classification accuracy passes the test.The classification results show that the hierarchical classification technique combining image texture features and spectral features is superior to other traditional methods in the extraction of alpine wetland information， and it is able to achieve Information extraction and analysis of alpine wetland refinement.Secondly， the area of alpine wetland in Maduo County is more in the east than in the west， more in the north and less in the south， and the main types of wetlands are concentrated in the central and northern regions.The largest area of the permanent freshwater lake is 1685.58 km2， accounting for 69.05% of the total alpine wetland area of Maduo County， followed by herbaceous swamps and permanent rivers/streams， with an area of 495.56 km2 and 94.81 km2， accounting for 20.34% and 3.88%， respectively.The wetland area of seasonal saltwater lakes， seasonal freshwater lakes， intermittent rivers/streams， flooded wetlands， mud marshes， scrub swamps， inland salt marshes and glacial snow cover wetlands is within 1.25~73.23 km2， accounting for less than 1%， of which seasonal saltwater lakes and seasonal freshwater lakes are the smallest.Thirdly， the high-score data is not affected by the high-altitude resolution in the information extraction of alpine wetland in Qinghai-Xizang Plateau， so it has more feasibility and application， especially choosing the image of growth season and non-growth season with different time resolution， which has more advantages in obtaining seasonal alpine wetland type information.Lastly， the classification result shows that among the types of alpine wetlands in Maduo County， the area of lakes tends to increase， but the area of rivers and flooded wetlands tends to decrease.If protective measures are not taken timely and effectively， the wetlands in Maduo County may continue to degrade.
  • Comprehensive Application of Multi-source Data in the Analysis of a Low-level Wind Shear Process over Plateau Airport
  • Yuqian YAN;Weidong TIAN;Jinhai LI;Binghong HAN
  • 2020 Vol. 39 (6): 1329-1338.  DOI:10.7522/j.issn.1000-0534.2020.00035
  • Abstract ( ) HTML ( ) PDF (8507KB) ( )
  • In order to improve the prediction and early waning ability of the wind shear over Xining Airport.ERA-Interim reanalysis data， airport automatic meteorological observation station data， wind profile radar data and laser wind radar data was used in this paper， and analyzed the process of low altitude wind shear caused by micro-downburst in Xining Airport on 26 April 2018， comprehensively.The results showed the low-level wind shear occurred in Xining Airport Runway 11， which was a horizontal wind shear during the sudden change of wind speed.Before the occurrence of low-level wind shear， the study area was in the front of the transverse trough， mainly was controled by northwest air flow； The sky over Xining Airport was cloudy with low convective clouds， the condition of surface humidity was good（t-td≤4 ℃）； The middle layer contains dry air， which was conducive to the development of convective activities.The wind profile radar showed that there was a strong sinking motion at the time of landing， and appeared low-level precipitation in addition to， there was strong turbulence over 1000 m when 10~20 min before low-level wind shear process.The laser wind radar indicated at 13:25（Beijing Time， after the same）， a cyclonic vortex appeared at the landing track line 4.05 km away from the runway entrance and 475 m high， which was the early signal of low-level wind shear.A micro-downburst and thunderstorm high pressure are formed at 13:29-13:30， as well as a moderate divergence 441 m away from the runway entrance， 81 m high which induces horizontal wind shear and leads to low altitude missed approach of the aircraft.The research results of this paper provided a certain reference for understanding the information of the convection system by using the multi-source detection data， and it is important to guide significance for the prediction and early warning of the wind shear over the airport， and provide scientific and technological support for the timely response measures of the aircraft in the wind shear.

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