Plateau Meteorology

Current Issue

28 August 2020, Volume 39 Issue 4   
  • Characteristics of Temperature Variation in Warm Season over the Northern Hemisphere during the Global Warming Hiatus
  • Wen LUO;Xiaodan GUAN;Yongli HE;Ruixia GUO;Zhaolin LI;Chenyu CAO
  • 2020 Vol. 39 (4): 673-682.  DOI:10.7522/j.issn.1000-0534.2019.00031
  • Abstract ( ) HTML ( ) PDF (3197KB) ( )
  • The carbon dioxide in the atmosphere has increased monotonically over the past century.However, global mean surface air temperature did not rise significantly since the late 1990s.This decadal signal of cooling phenomenon drew the attention of the public and was named global warming hiatus.Most of studies have explored the mechanisms of the temperature variation in cold season during the warming hiatus.However, investigation on the temperature variation in warm season during the warming hiatus has received limited attention.In this paper, using the monthly temperature data from 1901 to 2015 provided by CRU (Climatic Research Unit) and adopting the methods of linear regression analysis and ensemble empirical mode decomposition (EEMD), the spatial and temporal distribution characteristics of warm season temperature variation over the Northern Hemisphere (NH) during the global warming hiatus were analyzed.The results show that the temperature in warm season continued to rise during the global warming hiatus, which exhibited the opposite trend contrast with cold season.In addition, the temperature changes in warm season present obvious regional difference in NH land, such as a significant warming in the northern North America and southeastern Europe while cooling in central Eurasia.In order to explore the reason why there are different decadal temperature variations over above three regions, the multi-scale analysis was applied on times series of temperature variation by the method of EEMD.The results indicated that a synergy effect between the long-term trend and the decadal modulated oscillation (DMO) in different phases leads to different temperature change in above three regions, and temperature in southeastern Europe has the fastest rising due to the fact that the long-term trend and DMO rose simultaneously.Considering the close relationship between the DMO and atmospheric circulation, it is founded that the geopotential height increased over northern North America and southeastern Europe during the global warming hiatus, and the corresponding blocking frequency increased, which led to extremely high temperature events and accelerated local temperature rising.On the contrary, it was the opposite situation in the central Eurasia.Therefore, this study concluded that the regional difference of temperature change in NH land during global warming hiatus was dominated by atmospheric circulation.This study provided a new dynamic mechanism for decadal temperature variation from the point of atmosphere circulation, which helps climatologists to better understand the climate change.
  • Spatio-temporal Patterns of Extreme Precipitation Events over China in Recent 56 Years
  • Shan LU;Zeyong HU;Baipeng WANG;Pei QIN;Li WANG
  • 2020 Vol. 39 (4): 683-693.  DOI:10.7522/j.issn.1000-0534.2019.00058
  • Abstract ( ) HTML ( ) PDF (6119KB) ( )
  • Using the daily precipitation datasets of 693 observational stations during the period of 1961 -2016, this paper analyzed the spatio-temporal patterns and variations of the extreme precipitation events, persistent extreme precipitation events and their start and end dates in China.The results showed that the extreme precipitation events increased significantly in the past 56 years in China, and the increasing trends of the amounts and days of extreme precipitation were observed at about 68% of the stations, which were mainly located in the southeastern coastal and Western China.The largest increase of extreme precipitation amounts was observed in Eastern China, with an increasing trend up to 18.2 mm·(10a)-1, while the most significant increase of extreme precipitation days was observed in Northwestern China, with an increasing trend of 0.37 d·(10a)-1.The variation of persistent extreme precipitation events averaged over China was characterized by insignificant increasing trend.The significant increasing trends of the amounts and frequencies of persistent extreme precipitation at the 99% confidence level were only observed over the Northwestern China, while the Northern China and Southwestern China showed insignificant decreasing trends.The start and end dates of extreme precipitation events averaged over China showed obvious advance and delay trend, respectively.The significant advance of start dates was found in Northwestern China, Qinghai-Tibetan Plateau and Northeastern China, and the significant delay of end dates was observed in Northwestern China, which led to an increase in the duration of extreme precipitation events in Northwestern China, with the largest rate of 10.4 d·(10a)-1.
  • Temporal and Spatial Characteristics of Ground Surface Soil Heat Flux over the Qinghai-Tibetan Plateau
  • Cheng YANG;Tonghua WU;Jimin YAO;Ren LI;Changwei XIE;Guojie HU;Xiaofan ZHU;Junming HAO;Jie NI;Xiangfei LI;Wensi MA;Amin WEN;Chengpeng SHANG
  • 2020 Vol. 39 (4): 706-718.  DOI:10.7522/j.issn.1000-0534.2020.00022
  • Abstract ( ) HTML ( ) PDF (3765KB) ( )
  • We have collected the measured data of 9 observation stations on the Qinghai-Tibetan Plateau.The measured data of these sites on the Qinghai-Tibetan Plateau were used to analyze the seasonal and daily variation characteristics of ground surface soil heat flux, and we discussed the reasons for the differences in the temporal characteristics of ground surface soil heat flux between stations.Then MODIS data (including the Terra Moderate Resolution Imaging Spectroradiometer vegetation indices version 6 data MOD13Q1 and the surface spectral reflectance of Terra Moderate Resolution Imaging Spectroradiometer bands 1 through 7 product MOD09CMG), daily land surface temperature dataset in Western China under all-sky condition with 1 km spatial resolution, and assimilation data (ITPCAS-SRad and ITPCAS-LRad) were applied to simulate the spatial distribution of ground surface soil heat flux over the Qinghai-Tibetan Plateau by the scheme Ma on 12 July and 16 October 2014, 1 January and 7 April 2015.The results shown that: The amplitude of ground surface soil heat flux varies with the season, the summer is larger, the winter is the smallest, and the amplitude between the stations is different from the underlying surface.The higher the coverage of the underlying surface, the smaller the amplitude; ground surface soil heat flux is positive in spring and summer and throughout the year, while ground surface soil heat flux in autumn and winter is negative.Ground surface soil heat flux is greater than 0, which means that the underground soil absorbs heat from the surface, otherwise, the underground soil releases heat.Ground surface soil heat flux on the the Qinghai-Tibetan Plateau shows an obvious daily variation curve of inverted U-shape, and its change of the night is relatively flat compared with the daytime.There is a significant seasonal difference in the duration of the daily variation curve of ground surface soil heat flux.The order of the four seasons is: summer > spring > autumn >winter.There is a good positive correlation between the spatial distribution characteristics of ground surface soil heat flux and that of land surface temperature on the the Qinghai-Tibetan Plateau.Station data shows that for every 1 °C increase in land surface temperature, ground surface soil heat flux will increase by 2 ~ 5 W·m-2.This study further deepens the understanding of ground surface soil heat flux over the Qinghai-Tibetan Plateau, in order to provide basis and help for the prediction of frozen soil evolution, accurate estimation of evapotranspiration and geogas interaction.
  • Analysis of the Turbulent Fluxes of Water & Heat Exchange between the Zoige Alpine Wetland and Atmosphere
  • Xuancheng LU;Jun WEN;Hui TIAN;Yue YANG;Aoli YANG
  • 2020 Vol. 39 (4): 719-728.  DOI:10.7522/j.issn.1000-0534.2019.00073
  • Abstract ( ) HTML ( ) PDF (6373KB) ( )
  • The water & heat exchange fluxes between wetland and atmosphere have significant impact on the land surface process and even the weather and climate change.It is of great significance to accurately quantify the water & heat exchange fluxes between the wetland and the atmosphere.By using the observation data of the eddy-covariance system in the Zoige alpine wetland Land Surface Process and Climate Change Observatory (hereinafter referred to as “Flower Lake Observatory”) of the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, from March 2017 to March 2018.The diurnal cycle characteristics of the sensible heat flux and latent heat flux in the Zoige wetland were analyzed by selecting three fully cloud-free days each season, and inter-compared to the observed values of Ngoring lake and Maqu grassland.The energy closure ratio over the Zoige alpine wetland was calculated.The results show that there are evident diurnal cycles in the water & heat exchange fluxes between the Zoige alpine wetland and the atmosphere.The diurnal variation cycle of sensible heat flux and latent heat flux are unimodal, reaching a maximum at 14:00 to 15:00 (Beijing time).The daily average of sensible heat flux in the cold and dry season is 18.0% larger than that in the warm and humid season; While the daily average of latent heat flux in the warm and humid season is 68.7% higher than that in the cold and dry season.The observed sensible heat flux and latent heat flux are also compared to the ones of the Maqu grassland and the Ngoring lake surface.It is found that the sensible heat and latent heat transported to the atmosphere from the surface of Zoige wetland is similar to that from the surface of Ngoring lake in summer.The diurnal cycle of the wetlands is much larger than that of the lake surface, which is around 4 to 7 times that of the lake surface.The diurnal cycle of sensible heat flux in the Maqu grassland is about 1.5 times of that in the Zoige wetland, while the total latent heat flux of the wetland in summer is about 1.2 times that of the grassland.Among the energy transported upwards from the surface, the proportion of energy imbalance is 27.7% in spring, 22.7% in summer, 15.7% in autumn, and 19.4% in winter.The wetland mainly transfers energy to the atmosphere in the form of latent heat throughout the whole year.The proportion of latent heat flux to the effective energy reaches 58.0% in summer.
  • Different Cloud Microphysics Parameterization Schemes on a Strong Convection Simulation under Weak Synoptic-Scale Forcing
  • Xinglu REN;Shuwen ZHANG;Lan WANG;Rui SHI
  • 2020 Vol. 39 (4): 750-761.  DOI:10.7522/j.issn.1000-0534.2020.00026
  • Abstract ( ) HTML ( ) PDF (8905KB) ( )
  • Five typical cloud microphysics parameterization schemes, i.e.NSSL 1-momlfo scheme, Morrison 2-moment scheme, Thompson scheme, WDM6(WRF Double-Moment 6-class) and HUJI spectral bin microphysics (FAST), in the WRF (Weather Research and Forecasting) model were used to simulate a severe convective process under weak synoptic-scale forcing in the north of Jiangsu Province on July 26, 2016.The results show that only the NSSL 1-momlfo scheme can reproduce this severe convective process well, including the location, the intensity of the strong convective echo region and the stratiform cloud region, while the simulated radar echoes with Morrison, Thompson, WDM6 and HUJI schemes significantly differ from the real observations.The reason for the differences is investigated by comparing the effects of different schemes on the dynamic and thermodynamic structure of strong convection and the spatial distribution of hydrometeors and latent heat.It is found that the NSSL scheme shows the strongest updraft, although low-level wind convergence is simulated with the NSSL, WDM6 and HUJI schemes.Meanwhile, more concentrated cold pool is found out with the NSSL scheme, while the cold pool distributes over a large area in both the WMD6 and HUJI scheme, which is consistent with wider and stronger simulated radar echo.Conversely, the cold pool is distributed in a narrow region in the Morrison scheme and Thompson scheme, especially in the Morrison scheme, where almost no cold pool is found out.Furthermore, the distribution of hydrometeors with the NSSL scheme is concentrated in a horizontal narrow area, with more rainwater in the middle and lower layers and more snow particles and graupel particles in the middle and upper layers.The distribution of hydrometeors in the rest four schemes is quite different from that in the NSSL scheme: almost no rain, cloud droplets and ice in the Morrison scheme; except for snow distributed in a larger area, no ice and graupel, and almost no rain and cloud droplets in the Thompson scheme; the wide distribution of rain, snow and graupel with several large value centers but almost no cloud ice in the WDM6 scheme; a wide distributed snow and ice in HUJI scheme.Meanwhile, the NSSL scheme produces the most latent heat, resulting in a strengthened updraft, while the latent heat in the other four schemes is less than the NSSL scheme in both intensity and spatial distribution.And furthermore, it is the least in the Morrison scheme.
  • Variation Features of Hourly Precipitation in Xinjiang Province During 1991 -2018
  • Xia YANG;Hongkui ZHOU;Keming ZHAO;Zheng TANG;Yizhou ZHAO
  • 2020 Vol. 39 (4): 762-773.  DOI:10.7522/j.issn.1000-0534.2019.00114
  • Abstract ( ) HTML ( ) PDF (8170KB) ( )
  • Based on the hourly precipitation data from sixteen stations in Xinjiang Province during 1991 -2018， the spatio-temporal and diurnal variation characteristics of hourly extreme rainfalls in Xinjiang during summer were analyzed.The results showed that the hourly extreme precipitation and frequency in North Xinjiang are higher than that in South Xinjiang， and that in mountain area is higher than that in plain.The intensity of hourly extreme precipitation in the northern Xinjiang and the southern piedmont of Tianshan Mountain is larger in the West than in the East， and that in the Northern Piedmont of Kunlun Mountain is larger in the east than in the West.The contribution rate of hourly extreme heavy rainfall to summer total precipitation in South Xinjiang (25.0%) is larger than that in North Xinjiang (23.0%).The maximum hourly extreme precipitation and frequency were in July in Northern Xinjiang and June in most of Southern Xinjiang.The high value period of hourly extreme precipitation and frequency is from afternoon to the first half of the night， the low value period is from morning to morning in Northern Xinjiang， and from noon to afternoon in southern Xinjiang.The precipitation and frequency in July of Northern Xinjiang is the largest， 19：00 (Beijing time, the same as after) -01：00 is the high value period； in June of Southern Xinjiang is the largest， 18：00 -22：00 is the high value period； in July of southern and Northern Xinjiang， the precipitation intensity is the largest， 16：00 -22：00 is the relatively high value period.The trend of hourly extreme precipitation， frequency and intensity is not significant.The precipitation in Yili River valley plain area， the West and east section of the north slope of Tianshan Mountain and the West and east of South Xinjiang showed an increasing trend， especially in the east of South Xinjiang.The precipitation intensity in the southern mountainous area of Ili River Valley and the southern part of Southern Xinjiang showed a significant weakening trend.The trend of hourly precipitation from the late midnight to the early morning in southern and Northern Xinjiang is opposite， and it is the same in the evening.The average hourly extreme precipitation in Xinjiang decreased significantly at 20：00.The frequency of precipitation decreased significantly at 18：00 in Northern Xinjiang and increased significantly at 06：00 in southern Xinjiang.The intensity of precipitation increased significantly at 09：00 and 10：00 in the north and 07：00 in the south of Xinjiang.
  • Analysis on Mesoscale Impact System and Atmospheric Vertical Structure of Two Types of Heavy Rains in Urumqi
  • Yong ZENG;Lianmei YANG
  • 2020 Vol. 39 (4): 774-787.  DOI:10.7522/j.issn.1000-0534.2019.00070
  • Abstract ( ) HTML ( ) PDF (15933KB) ( )
  • Based on the conventional observational data, the TBB data of FY-2G satellite, data of Doppler weather radar, wind profiler radar, ground-based microwave radiometer, and NCEP/NCAR reanalysis data with 1°×1° spatial resolution, the mesoscale system and atmospheric vertical structure of three typical heavy rain processes occurred on 9 June, 27 June 2015 and from 2 to 3 October 2016 (referred to as Process 1, Process 2 and Process 3, respectively) in Urumqi were studied.The results are as follows: Process 1 and Process 2 were the strong convective storm, which were generated in the southwest airflow before the high-pressure ridge and the southwest airflow in the front of the low-value system with short-term heavy precipitation, respectively; Process 3 was the steady rainstorm, which was the longer and smoother occurred in the westward airflow in front of the trough.Process 1 and Process 2 were more favorable for the occurrence of short-term heavy precipitation during heavy rain due to more unstable and more humid at the lower atmosphere than Process 3.The strong convective storm were caused by β-mesoscale convective clouds, which were relatively isolated, small in scale, rapid in generation and development, and short in life history as well as the γ-mesoscale convective system, which were small in scale, fast in growth and rapid in movement, and there were convergence of wind speed at intermediate and low-level and convergence at low-level and divergence at high-level in radial velocity; The steady rainstorm was caused long-term and large-scale laminated hybrid cloud, echoes of stratified hybrid cloud and shear lines.Wind profiler radar and microwave radiometer could meticulously describe the evolution of wind field and humidity during heavy rain, the high and low wind fields showed reverse and clockwise rotation with height, and the cold and warm advection enhanced the instability of the atmosphere before the start of heavy rain;When the rainstorm is approaching 0.5~1 h, the obvious increase of wind speed at different altitudes and the sharp development of relative humidity could be used as the early warning for the beginning of heavy rain; vertical wind shear was obvious during the rainstorm and the water vapor saturation zone developing in the form of fluctuations; horizontal wind field and relative humidity change more severely during the strong convective rainstorm.At the same time, when the water vapor saturation zone developing to the highest position in the heavy rain process, short-term heavy precipitation occurred.
  • Statistical Characteristics and Trend Change of Different Duration Short-Duration Heavy Rainfall in Shanxi Province
  • Aimei MIAO;Hongxia WANG;Jie WU
  • 2020 Vol. 39 (4): 796-807.  DOI:10.7522/j.issn.1000-0534.2019.00069
  • Abstract ( ) HTML ( ) PDF (7427KB) ( )
  • Based on the short-duration heavy precipitation data of 109 stations in Shanxi Province from 1981 to 2018, the extreme value, frequency, day, month and interdecadal trend changes of heavy precipitation in different diachronic periods of 12 hours were analyzed by using trend coefficient, climatic tendency rate, normalization and mesoscale weather analysis methods.The results show that： (1) The spatial distribution of the extreme value is higher over the mountain area than the basin and greater over the south than the north of Shanxi.The shorter duration of the extreme value, the stronger local distribution of the extreme value.(2) Within 12 hours, the occurrence frequency of heavy precipitation in different diachronic periods has the spatial distribution characteristics of being high in the south and low in the north, higher in the mountain area than in the basin area, higher in the eastern mountain area than in the western mountain area, and obviously concentrated in the southeast.(3) Severe precipitation with different diachronic periods occurs in July-August every year, and the frequency of short-duration heavy precipitation with 1 h ≥0 mm is the highest.(4) The intra-day distributions of heavy precipitation with 1 hour rainfall (≥20 mm), 3 hours rainfall (≥30 mm) and 12 hours rainfall (≥50 mm) are single peak curves, while the intra-day distribution of heavy precipitation with 6 hours rainfall (≥50 mm) is double peak curve.(5) The growth rates of the annual occurrence times variation of 1 hour, 3 hours, and 6 hours short-duration heavy precipitation are the highest in southeastern Shanxi Province, which is the largest in the eastern and western mountain areas of Shanxi Province of 12 hour short duration heavy precipitation.(6) The main influence systems of 6 hours and 12 hours short duration heavy precipitation are obviously different from the systems of 1 hour and 3 hours short duration heavy precipitation.61% of 6 hours and 12 hours short duration heavy precipitation cases are caused by the combination of systematic precipitation and multiple mesoscale heavy precipitation.
  • Analysis of the Relationship between Structures of a Cold Vortex Process and Rainfall over the Northeast China
  • Duo QI;Meiying YUAN;Yihan ZHOU;Bing HAN
  • 2020 Vol. 39 (4): 808-818.  DOI:10.7522/j.issn.1000-0534.2019.00078
  • Abstract ( ) HTML ( ) PDF (14017KB) ( )
  • Based on conventional observations and the FNL reanalysis data, this paper analyzes the relationship between the rainfall characteristics and the circulation of a cold vortex during different phases for the strongest cold vortex associated rainstorm in recent 10 years over the northeast China.In general, the rainfall distribution is closely related to the dynamical and thermal conditions and water vapor distribution in a cold vortex process.The cold vortex process can be divided into four phases, the formation, developing, mature, and dissipating phase, respectively.In the formation phase, the precipitation is mainly confined in the area with strong vertical movement, but the precipitation rate is small.In the developing phase, the baroclinic condition is strong.Over the front part of the cold vortex there are strong dry and cold advections in the upper level and warm and wet advections in the lower level.Intensive rainfall is mainly distributed in the front of the cold vortex where the convergence is the strongest.The precipitation rate shows a direct proportional relationship to the strength and vertical velocity of the convergence center in the lower level.In the mature phase, the cold vortex is quasi-barotropic.The intensity and range of the vertical velocity are the largest, the precipitation is widely distributed in the center and front of the cold vortex.The precipitation center moves towards the center of the cold vortex, and its intensity is similar to that during the developing phase.The precipitation distribution is more related to the distribution of unstable energy and dry cold air than to the dynamical conditions.In the dissipating phase, the precipitation is scattered and its intensity decreases rapidly, and its relationship with circulation and other conditions is no longer significant.For this case, the convergence of water vapor from the south, west and east played an essential role in the evolution of the cold vortex.The inflow of water vapor from the south was the main water vapor source for the strong rainstorm.There was significant positive correlation between the net inflow of water vapor and the intensity of precipitation.
  • Preliminarily Evaluate the Applicability of Satellite Precipitation Products over the Taihang Mountains
  • Linfei YU;Yongqiang ZHANG;Jiahua ZHANG;Yonghui YANG
  • 2020 Vol. 39 (4): 819-829.  DOI:10.7522/j.issn.1000-0534.2020.00007
  • Abstract ( ) HTML ( ) PDF (3825KB) ( )
  • High-resolution satellite precipitation products (SPPs) provide forcing inputs for hydrologic applications.Complex mountain terrains have a significant effect on the occurrence and intensity of precipitation.In this study, ground-based observations were adopted as the benchmark to evaluate accuracy and precipitation detection capability of three SPPs (bias-corrected Climate Prediction Center morphing method, CMORPH CRT; Tropical Rainfall Measuring Mission, TRMM 3B42V7; and Integrated Multi-satellite Retrievals for Global Precipitation Measure, GPM IMERG) was validated by 104 rain gauges from 1 January 2016 to 31 December 2017 in different time scales (1 h, 3 h, 6 h, 12 h and 24 h) based on different precipitation intensity (light rain, moderate rain, heavy rain, very heavy rain and extreme rain) over the Taihang Mountains.Eight statistical metrics were utilized to quantitative analysis in this research.These indices include Correlation Coefficient (R), Root Mean Square Error (RMSE), Bias ratio (β), Variability ratio (γ), Kling-Gupta efficiency (KGE'), Probability of Detection (POD), False Alarm Ratio (FAR) and Critical Success Index (CSI).Results show that: (1) The accuracy performance of each SPP gradually stabilizes after the precipitation accumulate to 3 h, and the KGE' basically remains unchanged after 3 h time scale.In terms of the precipitation detection performance of SPPs, POD of three SPPs increase with the accumulation of precipitation time (POD range from 0.5 to 0.8), and FAR of CRT and 3B42 products decrease with the accumulation of precipitation time (FAR range from 0.5 to 0.75).(2) In terms of the accuracy analysis of different precipitation intensity ranges, there is a weak correlation between precipitation observations by SPPs and precipitation observations on the ground (R<0.4).RMSE increase with the increase of precipitation intensity for all SPPs, POD of all SPPs decrease with the increase of precipitation intensity over the Taihang Mountains, ranging from 0.4 to 0.65, and FAR of all SPPs increases with the increase of precipitation intensity, ranging from 0.6 to 0.85.(3) In terms of Probability density distribution (PDF), IMERG product underestimates the rain event of P<0.1 mm in all time scales.To varying degree, IMERG product overestimates the rain event of P≥0.1 mm over the Taihang Mountain.CRT product shows an overestimation of heavy rain and very heavy rain events at 1 h, 6 h, 12 h and 24 h.The PDF of 3B42 product in different precipitation intensity ranges are closer to the actual observed precipitation on the ground in study areas, but the observation of moderate rain events is underestimated by this product in all time scales.Our results not only demonstrate the superiority of different products at different time scales and precipitation intensity ranges, but also provide suggestions for further improvement of the SPPs especially for complex terrains.
  • The Transitional Change of Climate in the East of Northwest China
  • Pengli MA;Jinhu YANG;Guoyang LU;Biao ZHU;Weiping LIU
  • 2020 Vol. 39 (4): 840-850.  DOI:10.7522/j.issn.1000-0534.2019.00093
  • Abstract ( ) HTML ( ) PDF (7281KB) ( )
  • In the past half century, the eastern of Northwest China has experienced a warm and dry trend. In this century, this trend is to continue to maintain or change? For this issue, based on the latest observations from the National Meteorological Information Center, the variations of annual precipitation and mean temperature in the eastern of Northwest China were reanalyzed using some statistical methods. From the long-term trend, the winter precipitation in the eastern of Northwestern region is weakly increasing, and there is no obvious trend in summer, but the spring and autumn are decreasing. So it is the decreasing trend of spring and autumn that makes the annual precipitation decrease. Although the changes in precipitation in the year and the four seasons are not completely consistent, they have shown an increasing trend in the past 20 years since the beginning of this century, especially since 2010, the precipitation is more obvious. For the average temperature, the eastern of Northwestern region shows a significant warming trend, and it is more significant in the 1990s. In addition, the characteristics of the south and north regions of 36°N are not completely consistent. Since the beginning of this century, the region north of 36°N has shown a stage of cooling, while the area south of 36°N continues to show warming, but the warming rate is obviously slowed down. In terms of seasons, the average temperature of the four seasons in eastern of Northwestern has increased in the past 58 years. Compared with the south of the region from the mid-1980s to the end of the 1990s, the temperature increase in the north of 36°N is greater than south of 36°N. In the north of 36°N, the warming rate in the spring and summer of the first 10 years of this century has slowed down noticeably. Autumn and winter temperature has shown a stage of cooling, and the same as annual temperature. In the south of 36°N, the spring, summer and autumn have not shown obvious cooling in the past century, but they showed a stage of cooling in the late 1990s. The staged cooling makes the annual average temperature have no obvious change trend in the first 10 years of this century. In addition, whether it is north or south of 36°N, the temperature increase characteristic of the average temperature has changed from the beginning of this century, the temperature increase has slowed down, and even the stage has become cold. Therefore, the annual precipitation and average temperature in the eastern of Northwest China have undergone a turning point since the beginning of this century. Preliminary analysis found that this transitional change with increased precipitation, slower temperature increase and even phased cooling may be related to the conversion of PDO from warm phase to cold phase.
  • Study on the Cycles of Sunspots in the Earth’s Land-Ocean Temperature Index Since 1880
  • Jijun GUO;Zhilong GUO;Ninglian WANG
  • 2020 Vol. 39 (4): 851-858.  DOI:10.7522/j.issn.1000-0534.2020.00038
  • Abstract ( ) HTML ( ) PDF (2729KB) ( )
  • Several cycles exist in time series in the earth's surface temperature.Solar radiation with some cycles is the external driving force of the earth's climate system which modulates the earth's surface temperature and its modulation role to the earth's surface temperature is also one of the basic research contents of climate prediction.The cycles of the earth's land-ocean temperature index since 1880 are analyzed by Morlet complex-valued wavelet transform method, and the 22-year cycle was identified in the earth's land-ocean temperature index.Using the method of moving average to improve the analysis method of air temperature anomalies, the amplitude of the 22-year cycle of the earth's land-ocean temperature index is obtained, and then combined with the MATLAB function fitting program, on the basis of the period, phase, amplitude, etc.The fitting results indicate that the 22-year cycle of the earth's land-ocean temperature index is positively correlated with the 22-year cycle of the sunspots.When the 22-year cycle of sunspot activity is in a positive phase, the surface temperature of the earth is in a warmer phase; when the 22-year cycle of sunspots is in a negative phase, the surface temperature of the earth is in a relatively low temperature phase.The temperature on the earth's surface fluctuates in the form of a quasi-sine function around its 22-year moving average.The long-period temperature of the earth's surface reflects the decadal climate background of the earth's surface temperature, and the short-period change process reflects the temperature change process under the long-period climate background.Multiple cycles overlap each other, forming a complex temperature fluctuation.Sunspot activity is not strictly a one-to-one correspondence with the Earth's surface temperature.The Earth's surface temperature is not only restricted by the factors affecting the long-term scale, but also affected by other short periods.Further analyses show that the 22-year magnetic cycle of sunspots may be a driving factor of the 22-year cycle in the earth's land-ocean temperature index.The amplitude of the 22-year cycle of the earth's land-ocean temperature index is up to about 0.21 °C under constrained by a 99% confidence level, which may have an important impact on the assessment of global warming.The 22-year cycle is an important factor for climate simulation and assessment research and provided some new evidences for quantitative research and driving mechanism of global climate.
  • The Regional Sea Air Coupled Model（RIEMS2.0-POM2K） Simulated the Affecting of Black Carbon Aerosol on the Spring and Summer Climate over East Asia
  • Min LUO;Jian WU
  • 2020 Vol. 39 (4): 870-888.  DOI:10.7522/j.issn.1000-0534.2019.00064
  • Abstract ( ) HTML ( ) PDF (5644KB) ( )
  • The radiative forcing of black carbon aerosol (BC) and its effects on the climate of East Asia still have significant uncertainties.Moreover, little attention has been paid to the ocean in the study of climate effects of BC.In order to quantitavely analyze the direct radiative forcing of BC and its effect on East Asia summer monsoon through the sea air interactions, here the sensitivity experiments of the off-line simulation of BC was carried out by using the regional air sea coupling model.The results of sensitivity experiments show that the clear sky net direct radiative forcing under clear-sky conditions over East Asia is 1.58 W·m-2 at the top of atmosphere (TOA) and -2.75 W·m-2 at the surface in spring respectively, and 1.68 W·m-2 on TOA and -2.62 W·m-2 on the surface in summer respectively.Effected by the radiative effects of BC, the atmosphere gets warmer, the thermal stability of atmosphere increases, while the cloud cover decreases.In spring, the “Elevated Heat Pump” effect of BC causes the increased precipitation over the South China (SC) and the advanced summer monsoon.In summer, the radiative effects of BC cause a cooling effect on the Bengal Bay and then reinforce the South Trough, which results in the increased precipitation over SC; Furthermore, the increased meridional temperature gradient around the middle latitude can enhance the force of cold air and the divergence of water vapor, which can induce the decreasing of the precipitation over the North China (NC).The positive anomaly of the precipitation over SC and the negative anomaly of the precipitation over NC favor the "southern flood and northern drought".The radiative effects of BC can raise the tropical sea surface temperature (SST) while decrease the meridional SST gradient and the sea land thermal contrast through the sea air interactions, that will lead to a weak summer monsoon.In addition, the radiative effects of BC can also enhance the local Hadley circulation and the northerly wind, and then weaken the summer monsoon.

NewsDownloadMore+More+

DynamicsVideo InformationMore+More+

Links E-journal More+ More+

Official Wechat

QQ Group Chat

The system is designed and developed by Beijing magtec Technology Development Co., Ltd. with technical support: support@magtech.com.cn