Estimated supply of RED credits 2011–2035

Previous attempts to estimate the supply of greenhouse gas emission reductions from reduced emissions from deforestation (RED) have generally failed to incorporate policy developments, country-specific abilities and political willingness to supply offsets for developed countries’ emissions. To address this, we estimate policy-appropriate projections of creditable emission reductions from RED. Two global forest carbon models are used to examine major assumptions affecting the generation of credits. The results show that the estimated feasible supply of RED credits is significantly below the biophysical mitigation potential from deforestation. A literature review identified an annual RED emission reduction potential between 1.6 and 4.3 Gt CO₂e. Feasible RED supply estimates applying the OSIRIS model were 1.74 Gt CO₂e annually between 2011 and 2020, with a cumulative supply of 17.4 Gt CO₂e under an ‘own-efforts’ scenario. Estimates from the Forest Carbon Index were very low at $5/t CO₂e with 8 million tonne CO₂e annually, rising to 1.8 Gt CO₂e at $20/t CO₂e. Cumulative abatement between 2011 and 2020 was 9 billion Gt CO₂e ($20/t CO₂e). These volumes were lower, sometimes dramatically, at prices of $5/t CO₂e suggesting a non-linear supply of credits in relation to price at a low payment level. For policy makers, the results suggest that inclusion of RED in a climate framework increases abatement potential, although significant constraints are imposed by political and technical issues.     

Modulation of the Intraseasonal Variability of Pacific–Japan Pattern by ENSO

This study investigates how the El Ni?o–Southern Oscillation(ENSO) modulates the intraseasonal variability(ISV) of Pacific–Japan(PJ) teleconnection pattern. The PJ index during boreal summer is constructed from the empirical orthogonal function(EOF) of the 850-hPa zonal wind(U850) anomalies. Distinct periods of the PJ index are found during El Ni?o and La Ni?a summers. Although ISV of the PJ pattern is significant during 10–25 days for both types of summers, it peaks on Days 30 and 60 in El Ni?o and La Ni?a summers respectively. During El Ni?o summers, the 30-day ISV of PJ pattern is related to the northwestward propagating intraseasonal oscillation(ISO) over the western North Pacific(WNP), which is originated from the tropical Indian Ocean(IO). During La Ni?a summers,the 60-day ISV of PJ pattern is related to the northeastward propagating ISO from the tropical IO. The low-frequency ISV modes in both El Ni?o and La Ni?a summers are closely related to the boreal summer ISO(BSISO), and the high-frequency ISV modes over WNP are related to the quasi-biweekly oscillation. The underlying mechanisms for these different evolutions are also discussed.     

Analysis of the interannual variations and influencing factors of wind speed anomalies over the Beijing–Tianjin–Hebei region

风场对京津冀地区雾霾的产生和消散起着决定性作用。本文利用站点观测数据,研究了京津冀地区冬季风场的年际变化及其影响因素。研究表明,京津冀地区的冬季平均风速为2.0 m s~(-1),每年降幅为0.01 m s~(-1)。大多数情况下,强风年对应热带太平洋东部的负海温异常,而弱风年份相反。此外,京津冀地区冬季风场的年际变化还受到包括北半球中高纬度气压梯度、欧亚大陆地表温度、菲律宾东部热带太平洋海面温度等多重因素的影响。     

Improvement of the Mellor–Yamada–Nakanishi–Niino Planetary Boundary-Layer Scheme Based on Observational Data in China

The Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer (PBL) scheme is a second-order turbulence closure model that is an improved version of the Mellor–Yamada scheme based on large-eddy simulation data. It simulates PBL structure and evolution well, particularly over the ocean surface. However, when used with various underlying surfaces in China, the scheme overestimates the turbulent momentum flux and the sensible heat flux. Based on observations of surface fluxes in China, we attempt to improve the MYNN model by modifying the parameters and representation of the turbulence scale. Closure constants and empirical expressions in the diagnostic equation are chosen first, and an additional component of the turbulent heat flux is considered in the potential temperature prognostic equation to improve the surface heat-flux modelling. The modified MYNN scheme is incorporated into a three-dimensional mesoscale model and is evaluated using various underlying surface observations. Amelioration of the surface turbulent fluxes is confirmed at five observational sites in China over different land-use types.     

Conditions of generation of extremely high water content of Primorye rivers in autumn–winter 2012

Analyzed are the synoptic and hydrological conditions of the generation of extremely high water content of Primorye rivers in the autumn of 2012. Revealed are the general features of atmospheric circulation, precipitation, water content, and hydrological regime of rivers. Presented are quantitative parameters characterizing the extremity of observed events. The expert assessment of the probability of such combination of events demonstrates that its return period is about 500–1000 years if there is assumption on the stationarity of processes. Taking into account the revealed facts and available assessments of climate changes it can be supposed that the analyzed event rather indicates real changes in the hydrological regime of the region than represents a rare random phenomenon.     

Thermal Structure of a Coastal–Urban Boundary Layer

We use various temperature profilers located in and around New York City to observe the structure and evolution of the thermal boundary layer. The primary focus is to highlight the spatial variability of potential-temperature profiles due to heterogeneous surface forcing in an urban environment during different flow conditions. Overall, the observations during the summer period reveal the presence of thermal internal boundary layers due to the interaction between the marine atmospheric boundary layer and the convective urban environment. The summer daytime potential-temperature profiles within the city indicate a superadiabatic layer is present near the surface beneath a mildly stable layer. Large spatial variability in the near-surface (0–300 m) potential temperature is detected, with the thermal profile in the lower atmosphere uniquely determined by the underlying surface forcing and the distance from the coast. The summer and winter average night-time potential-temperature profiles show that the atmosphere is still convective near the surface. The seasonal averages of mixing ratio show large variability in the vertical direction.     

Representation of the Madden–Julian Oscillation in CAMS-CSM

The Madden–Julian Oscillation(MJO) has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting. We evaluate the ability of the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM) to represent the MJO by using the diagnostic method proposed by the US Climate Variability and Predictability Program(CLIVAR) MJO Working Group(MJOWG). In general,the model simulates some major characteristics of MJO well, such as the seasonality characteristics and geographical dependence, the intensity of intraseasonal variability(ISV), dominant periodicity, propagation characteristics, coherence between outgoing longwave radiation(OLR) and wind, and life cycle of MJO signals. However, there are a few biases in the model when compared with observational/reanalyzed data. These include an overestimate of precipitation in the convergence zone of the North and South Pacific, a slightly weaker eastward propagation, and a shift in the dominant periodicity toward lower frequencies with slower speeds of eastward propagation. The model gives a poor simulation of the northward propagation of MJO in summer and shows less coherence between the MJO convection and wind. The role of moistening in the planetary boundary layer(PBL) in the eastward/northward propagation of MJO was also explored. An accurate representation of the vertical titling structure of moisture anomalies in CAMS-CSM leads to moistening of the PBL ahead of convection, which accounts for the eastward/northward propagation of MJO. Poor simulation of the vertical structure of the wind and moisture anomalies in the western Pacific leads to a poor simulation of the northward propagation of MJO in this area. Budget analysis of the PBL integral moisture anomalies shows that the model gives a good simulation of the moisture charging process ahead of MJO convection and that the zonal advection of moisture convergence term has a primary role in the detour of MJO over the Maritime Continent.     

Improvement of a Snow Albedo Parameterization in the Snow–Atmosphere–Soil Transfer Model:Evaluation of Impacts of Aerosol on Seasonal Snow Cover

The presence of light-absorbing aerosols(LAA) in snow profoundly influence the surface energy balance and water budget.However,most snow-process schemes in land-surface and climate models currently do not take this into consideration.To better represent the snow process and to evaluate the impacts of LAA on snow,this study presents an improved snow albedo parameterization in the Snow–Atmosphere–Soil Transfer(SAST) model,which includes the impacts of LAA on snow.Specifically,the Snow,Ice and Aerosol Radiation(SNICAR) model is incorporated into the SAST model with an LAA mass stratigraphy scheme.The new coupled model is validated against in-situ measurements at the Swamp Angel Study Plot(SASP),Colorado,USA.Results show that the snow albedo and snow depth are better reproduced than those in the original SAST,particularly during the period of snow ablation.Furthermore,the impacts of LAA on snow are estimated in the coupled model through case comparisons of the snowpack,with or without LAA.The LAA particles directly absorb extra solar radiation,which accelerates the growth rate of the snow grain size.Meanwhile,these larger snow particles favor more radiative absorption.The average total radiative forcing of the LAA at the SASP is 47.5Wm~(-2).This extra radiative absorption enhances the snowmelt rate.As a result,the peak runoff time and "snow all gone" day have shifted 18 and 19.5 days earlier,respectively,which could further impose substantial impacts on the hydrologic cycle and atmospheric processes.     

Analysis of the Trends of Thunderstorms in 1951–2007 in Jiangsu Province

Based on the 1951–2007 thunderstorms in Jiangsu, a study is conducted for their climate trends, periodicity, spatiotemporal patterns, and the distributions of the first and last days of the thunderstorms at different guarantee rates (GRs) using climate tendency rate, wavelet analysis, and GR for diagnosis. Results suggest that the inter-annual number of thunderstorm days (TSDs) exhibits a decreasing trend in this province. The trend is displayed mainly in the decreasing TSD number in summer and autumn except in spring, when the variation is not significant in the study period. In this province, the TSD number declines by ~2 days per 10 years. On an inter-annual basis, the pronounced positive departures of the number take place chiefly in the early 1960s, the late 1960s to the early-mid-1970s, the late 1980s, and the late 1990s compared with the negative anomalies dominant in the late 1970s to the mid-1980s, the mid-to-late-1990s, and the late 1990s to 2007. There are vast differences in the initial and ending days at diverse GRs in different areas of the province. At 50% GR, the earliest (last) days occur from mid-March to early April (early to late September) while at 80% GR, the initial (last) days are from late March to early May (early to late October). For the distribution of periods, the periods >8–10 years are relatively stable for the entire province. Based on 1951–2007 period analysis, the region north (south) of the Huaihe River experiences TSDs less (more) than normal days in recent years.     

Spatiotemporal Variability of Surface Wind Speed during 1961–2017 in the Jing–Jin–Ji Region,China

Wind speed variations are influenced by both natural climate and human activities. It is important to understand the spatial and temporal distributions of wind speed and to analyze the cause of its changes. In this study, data from 26 meteorological stations in the Jing–Jin–Ji region of North China from 1961 to 2017 are analyzed by using the Mann–Kendall(MK) test. Over the study period, wind speed first decreased by-0.028 m s-1 yr-1(p 0.01) in1961–1991, and then increased by 0.002 m s1-yr1-(p 0.05) in 1992–2017. Wind speed was the highest in spring(2.98 m s-1), followed by winter, summer, and autumn. The largest wind speed changes for 1961–1991 and1992–2017 occurred in winter(-0.0392 and 0.0065 m s-1 yr1-, respectively); these values represented 36% and 58%of the annual wind speed changes. More than 90.4% of the wind speed was concentrated in the range of 1–5 m s-1,according to the variation in the number of days with wind speed of different grades. Specifically, the decrease in wind speed in 1961–1991 was due to the decrease in days with wind speed of 3–5 m s-1, while the increase in wind speed in 1992–2017 was mainly due to the increase in days with wind speed of 2–4 m s-1. In terms of driving factors,variations in wind speed were closely correlated with temperature and atmospheric pressure, whereas elevation and underlying surface also influenced these changes.     

Evaluation of the Madden–Julian oscillation in HiRAM

The aim of this study was to understand the cause of Madden–Julian oscillation (MJO) bias in the High Resolution Atmospheric Model (HiRAM) driven by observed SST through process-oriented diagnosis. Wavenumber-frequency power spectrum and composite analyses indicate that HiRAM underestimates the spectral amplitude over the MJO band and mainly produces non-propagating rather than eastward-propagating intraseasonal rainfall anomalies, as observed. Column-integrated moist static energy (MSE) budget analysis is conducted to understand the MJO propagation bias in the simulation. It is found that the bias is due to the lack of a zonally asymmetric distribution of the MSE tendency anomaly in respect to the MJO convective center, which is mainly attributable to the bias in vertical MSE advection and surface turbulent flux. Further analysis suggests that it is the unrealistic simulation of MJO vertical circulation anomalies in the upper troposphere as well as overestimation of the Rossby wave response that results in the bias.摘要本研究评估了高分辨率大气环流模式HiRAM模拟的MJO. 结果表明, HiRAM模拟的MJO东传很弱. 我们通过计算整层积分的湿静力能 (MSE) 收支来诊断MJO东传模拟偏差的原因. 结果发现, MSE倾向相对于MJO对流中心的纬向非对称分布很弱是导致东传模拟偏弱的原因, 这主要是由MSE垂直平流和地表湍流通量的模拟偏差造成的. 进一步研究表明, 对流层上层MJO垂直环流结构的模拟偏差和MJO对流西侧的Rossby波环流偏强共同导致了模式的偏差. 本研究中指出的MJO传播模拟偏差的原因与之前基于多模式结果的结论不同, 这意味着要想了解特定模式的模拟偏差, 有必要对该模式进行具体分析.     

Modeling the climatic effects of urbanization in the Beijing–Tianjin–Hebei metropolitan area

In this analysis, the weather research and forecasting model coupled with a single-layer urban canopy model is used to simulate the climatic impacts of urbanization in the Beijing–Tianjin–Hebei metropolitan area, which has experienced significant expansion in its urban areas. Two cases examining current landscapes and the sensitivity test of urban areas replaced by cropland have been carried out to explore the changes in the surface air and atmospheric boundary structure. The impact of urbanization on annual mean surface air temperature has been found to be more than 1 °C in urban areas, and the maximum difference is almost 2 °C. The change in near-surface level temperature is most pronounced in winter, but the area influenced by urbanization is slightly larger in summer. The annual mean water vapor mixing ratio and wind speed are both reduced in the urban area. The effect of urbanization can only heat the temperature inside the urban boundary layer, below 850 hPa. The modeling results also indicate that the underlying surface thermal forces induced by the “urban heat island” effect enhance vertical air movement and engenders a convergence zone over urban areas. The convergence at low level together with the moisture increases in the layer between 850 and 700 hPa triggered the increase of convective precipitation.     

Characterization of Stratospheric Aerosol Distributions during the Volcanically Quiescent Period of 1998–2004

The Stratospheric Aerosol and Gas Experiment （SAGE） II aerosol extinction profiles at 1020 nm were used to study the distribution characteristics of stratospheric aerosols during the volcanically quiescent period of 1998-2004. The stratospheric aerosol distributions exhibited hemispheric asymmetry between the Northern Hemisphere （NH） and the Southern Hemisphere （SH）. In the lower stratosphere below 20 km, the zonal averaged aerosol optical depths in the NH were higher than those of the corresponding SH; whereas at higher altitudes above 20 km, the optical depths in the SH-- except the equatorial region--were higher than those of the NH. At 0-10°N and 10-20°N, the stratospheric aerosol optical depth （SAOD） exhibited larger values in boreal winter and lower values in the spring and summer; at 0-10°S and 10-20°S, the SAOD presented small seasonal variations. At 30-40°N, the SAOD presented larger values in the boreal fall and winter and lower values in the spring and summer; while at 30-40°S, the SAOD exhibited larger values in the austral winter and early spring and lower values in the summer and fall. These characteristics can mainly be attributed to the seasonal cycle of the dynamic transport, and the effects of the buildup and breakdown of the polar vortex. At 50-60°S, the SAOD exhibited extremely high values during austral winter associated with the Antarctic polar vortex boundary; at 50-60°N, the SAOD also exhibited larger values during the boreal winter, but it was much less obvious than that of its southern counterpart.     

Causes of November cooling of the 1980s–1990s in European Russia

In the 1980s–1990s, a widespread November cooling occurred in European Russia against the background of global warming. Analysis showed that the observed cooling was caused by anomalous cold advection at the eastern edge of the area of positive sea-level pressure and geopotential anomaly centered over Scandinavia and the Gulf of Bothnia. This November circulation pattern is related to the positive phase of the Arctic Oscillation in the preceding winter. It is concluded that the observed November cooling was caused by the prevalence of the positive phase of the wintertime Arctic Oscillation and North Atlantic Oscillation in the last two decades of the 20th century.     

Application of the Hilbert–Huang Transform to the Estimation of Air-Sea Turbulent Fluxes

The Hilbert–Huang transform (HHT) is applied to analyzing the turbulent time series obtained within the atmospheric boundary layer over the ocean. A method based on the HHT is introduced to reduce the influence of non-turbulent motions on the eddy-covariance based flux by removing non-turbulent modes from the time series. The scale dependence of the flux is examined and a gap mode is identified to distinguish between turbulent modes and non-turbulent modes. To examine the effectiveness of this method it is compared with three conventional methods (block average, moving-window average, and multi-resolution decomposition). The data used are from three sonic anemometers installed on a moored buoy at about 6, 4 and 2.7 m height above the sea surface. For each method, along-wind and cross-wind momentum fluxes and sensible heat fluxes at the three heights are calculated. According to the assumption of a constant-flux layer, there should be no significant difference between the fluxes at the three heights. The results show that the fluxes calculated using HHT exhibit a smaller difference and higher correlation than the other methods. These results support the successful application of HHT to the estimation of air-sea turbulent fluxes.