Spatial Variation in CO_(2) Concentration Improves the Simulated Surface Air Temperature Increase in the Northern Hemisphere

The increasing concentration of atmospheric CO_(2) since the Industrial Revolution has affected surface air temperature.However,the impact of the spatial distribution of atmospheric CO_(2) concentration on surface air temperature biases remains highly unclear.By incorporating the spatial distribution of satellite-derived atmospheric CO_(2) concentration in the Beijing Normal University Earth System Model,this study investigated the increase in surface air temperature since the Industrial Revolution in the Northern Hemisphere(NH) under historical conditions from 1976-2005.In comparison with the increase in surface temperature simulated using a uniform distribution of CO_(2),simulation with a nonuniform distribution of CO_(2)produced better agreement with the Climatic Research Unit(CRU) data in the NH under the historical condition relative to the baseline over the period 1901-30.Hemispheric June-July-August(JJA) surface air temperature increased by 1.28℃ ±0.29℃ in simulations with a uniform distribution of CO_(2),by 1.00℃±0.24℃ in simulations with a non-uniform distribution of CO_(2),and by 0.24℃ in the CRU data.The decrease in downward shortwave radiation in the non-uniform CO_(2) simulation was primarily attributable to reduced warming in Eurasia,combined with feedbacks resulting from increased leaf area index(LAI) and latent heat fluxes.These effects were more pronounced in the non-uniform CO_(2)simulation compared to the uniform CO_(2) simulation.Results indicate that consideration of the spatial distribution of CO_(2)concentration can reduce the overestimated increase in surface air temperature simulated by Earth system models.

Understanding the factors influencing cloud-core vertical accelerations during deep convection formation in the WRF model

本文将扰动气压利用一个线性诊断关系代替,重新推导了WRF模式框架地形追随坐标系下的垂直动量方程,建立了垂直加速与对流触发(DCI)影响因子(如温度,水汽等)的直接联系.研究发现,DCI过程与对流核垂直加速相关,三维副散,扰动位势在垂直方向的二阶非均匀性,扰动位温垂直梯度,比湿及其垂直梯度,水凝物拖曳,均是能够直接影响垂直加速和对流触发的物理因子,这些量与模式基本预报量相关,通过解析基本预报量对对流发展的直接影响,可能有助于理解模式对DCI过程预测失败的原因.

Phosphorus Limitation on Carbon Sequestration in China under RCP8.5

Currently,there is a lack of understanding regarding carbon(C)sequestration in China arising as a result of phosphorus(P)limitation.In this study,a global land surface model(CABLE)was used to investigate the response of C uptake to P limitation after 1901.In China,P limitation resulted in reduced net primary production(NPP),heterotrophic respiration,and net ecosystem production(NEP)in both the 2030s and the 2060s.The reductions in NEP in the period2061–70 varied from 0.32 Pg C yr^(-1)in China to 5.50 Pg C yr^(-1)at the global scale,translating to a decrease of 15.0%for China and 7.6%globally in the period 2061–70,relative to the changes including C and nitrogen cycles.These ranges reflect variations in the magnitude of P limitation on C uptake(or storage)at the regional and global scales.Both in China and at the global scale,these differences can be attributed to differences in soil nutrient controls on C uptake,or positive feedback between NPP and soil decomposition rates,or both.Our results highlight the strong ability of P limitation to influence the pattern,response,and magnitude of C uptake under future conditions(2030s–2060s),which may help to clarify the potential influence of P limitation when projecting C uptake in China.

Convective Bursts Episode of the Rapidly Intensified Typhoon Mujigae(2015)

Convective burst(CB) characteristics at distinct stages of a rapidly intensified Typhoon Mujigae(2015), are investigated based on a 72-h simulation. The spatial features show that almost all CB elements develop in the eyewall. The number of CBs in the inner-core region within a 100 km radius—which account for a large proportion of the total CBs, with a sharp increase about 6 h before the onset of rapid intensification(RI)—provides some indication of the RI of the typhoon. The CBs during pre-RI and RI are examined from dynamic and thermodynamic viewpoints. The combination of lower-level convergent inflow and upper-level divergent outflow pushes a relay-race-like transmission of convective activity, favorable for the development of deep convection. A double warm-core structure is induced by the centripetal outflow sinking and warming associated with CBs, which directly accelerates RI by a sudden decrease in hydrostatic pressure. By utilizing the convection activity degree(CAD) index derived from the local total energy anomaly, a correlation formula between CBs and CAD is deduced.Furthermore, an intense CAD(ICAD) signal threshold(with a value equal to 100) to predict CBs is obtained. It is verified that this ICAD threshold is effective for estimating the occurrence of a CB episode and predicting RI of a typhoon. Therefore,this threshold may be a valuable tool for identifying CB episodes and forecasting rapidly intensified typhoons.

Trends in carbon sink along the Belt and Road in the future under high emission scenario

Over the past three decades,the drawdown of atmospheric CO_(2) in vegetation and soil has fueled net ecosystem production(NEP).Here,a global land-surface model(CABLE)is used to estimate the trend in NEP and its response to atmospheric CO_(2),climate change,biological nitrogen(N)fixation,and N deposition under future conditions from 2031 to 2100 in the Belt and Road region.The trend of NEP simulated by CABLE decreases from 0.015 Pg carbon(C)yr^(-2) under present conditions(1936–2005)to−0.023 Pg C yr^(-2) under future conditions.In contrast,the trend in NEP of the CMIP6 ensemble changes from 0.014 Pg C yr^(-2) under present conditions to−0.009 Pg C yr^(-2) under future conditions.This suggests that the trend in the C sink for the Belt and Road region will likely decline in the future.The significant difference in the NEP trend between present and future conditions is mainly caused by the difference in the impact of climate change on NEP.Considering the responses of soil respiration(RH)or net primary production(NPP)to surface air temperature,the trend in surface air temperature changes from 0.01℃ yr^(-1) under present conditions to 0.05℃ yr^(-1) under future conditions.CABLE simulates a greater response of RH to surface temperature than that of NPP under future conditions,which causes a decreasing trend in NEP.In addition,the greater decreasing trend in NEP under future conditions indicates that the C-climate-N interaction at the regional scale should be considered.It is important to estimate the direction and magnitude of C sinks under the C neutrality target.

On the rapid intensification for Typhoon Meranti(2016):convection,warm core,and heating budget

Through a cloud-resolving simulation of the rapid intensification(RI)of Typhoon Meranti(2016),the convections,warm core,and heating budget are investigated during the process of RI.By investigating the spatial distributions and temporal evolutions of both convectivestratiform precipitation and shallow-deep convections,we find that the inner-core convections take mode turns,from stratiform-precipitation(SP)dominance to convectiveprecipitation(CP)prevalence during the transition stages between pre-RI and RI.For the CP,it experiences fewer convections before RI,and the conversion from moderate/moderate-deep convections to moderate-deep/deep convections during RI.There is a clear upper-level warm-core structure during the process of RI.However,the mid-lowlevel warming begins first,before the RI of Meranti.By calculating the local potential temperature(0)budget of various convections,the link between convections and the warm core(and further to RI via the pressure drop due to the warming core)is established.Also,the transport pathways of heating toward the center of Meranti driven by pressure are illuminated.The total hydrostatic pressure decline is determined by the mid-low-level warm anomaly before RI,mostly caused by SP.The azimuthal-mean diabatic heating is the largest heating source,the mean vertical heat advection controls the vertical downwards transport by adiabatic warming of compensating downdrafts above eye region,and then the radial 6 advection term radially transports heat toward the center of Meranti in a slantwise direction.Accompanying the onset of RI,the heating efficiency of the upper-level warming core rises swiftly and overruns that of the mid-low-level warmanomaly, dominating the total pressure decrease and beingmainly led by moderate-deep and deep convections. Asidefrom the characteristics in common with SP, for CP, theeddy component of radial advection also plays a positiverole in warming the core, which enhances the centripetaltransport effect and accelerates the RI of Meranti.