大气模式估算的东亚区域人为硫酸盐和黑碳气溶胶辐射强迫及其时间变化特征   总被引：2，自引：0，他引：2       下载免费PDF全文

李剑东  毛江玉  王维强 《地球物理学报》2015,58(4):1103-1120

本文利用大气环流模式及大气化学模式所得气溶胶资料,估算了相对1850s时期硫酸盐和黑碳气溶胶引起的全球及东亚区域人为辐射强迫,重点分析其在东亚区域的季节和长期变化特征.结果表明,就当前全球年平均全天空而言,人为硫酸盐气溶胶对大气顶的直接和云反照率强迫分别为-0.37和-0.98 W·m-2,黑碳气溶胶对大气顶和整层大气的辐射强迫值为0.16和0.47 W·m-2;中国东部区域是目前上述气溶胶辐射强迫最强的区域,硫酸盐的直接和间接辐射强迫分别超过-2.0和-4.0 W·m-2,黑碳对大气顶和整层大气的直接辐射强迫分别可达2.0和5.0W·m-2;估算的东亚区域上述气溶胶辐射强迫仍在不断增强,峰值预计出现在2010s时段,而且中国东部较强的辐射强迫还可能维持至2030s左右;在未来中、高排放情景下,东亚区域以上两种气溶胶预计对全球气溶胶辐射强迫有更大的贡献.分析还表明,夏季东亚区域较强的水汽会增强吸湿性硫酸盐气溶胶的光学厚度和晴空直接辐射强迫;云的作用一方面会强化东亚区域全天空条件下大气顶黑碳的辐射强迫,另一方面会影响硫酸盐气溶胶间接云反照率强迫的季节变化;上述气候特征的差异使得东亚区域的气溶胶辐射强迫表现出与欧美区域有所不同的特征.本文所用的气溶胶资料与模式气象场的偏差会给气溶胶辐射强迫计算带来一些不确定性,进一步改进气候模式中气溶胶过程、水汽和云等气象场的模拟将有助于获得更为合理的区域气溶胶辐射强迫估算结果.  相似文献   

A STUDY ON THE IMPACTS OF LATENT HEAT PARAMETERIZATION SCHEME ON PREDICTION SKILL OF ENSO WITH A SIMPLE OCEAN-ATMOSPHERE COUPLED     

岳彩军  陆维松  李小凡 《热带气象学报(英文版)》2010,16(1):10-19

This study revises Weare’s latent heat parameterization scheme and conducts an associated theoretic analysis. The revised Weare’s scheme is found to present potentially better results than Zebiak’s scheme. The Zebiak-Cane coupled ocean-atmosphere model, initialized by the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalysis of wind stress anomaly at 925 hPa, is referred to as the ZCW coupled model. The atmosphere models of the ZCW coupled model that use Zebiak’s scheme and the revised Weare’s scheme are referred to as the ZCW0 and ZCWN atmosphere models, respectively. The coupled ocean-atmosphere models that use Zebiak’s scheme and the revised Weare’s scheme are referred to as the ZCW0and ZCWN coupled models, respectively. The simulations between the ZCW0 and ZCWN atmosphere models and between the ZCW0 and ZCWN coupled models are analyzed. The results include: (1) The evolution of heat, meridional wind and divergence anomalies simulated by similar ZCW0 and ZCWN atmosphere models, although the magnitudes of the former are larger than those of the latter; (2) The prediction skill of the Ni?o3 index from 1982 to 1999 by the ZCWN coupled model shows improvement compared with those by the ZCW0 coupled model; (3) The analysis of El Ni?o events in 1982/1983, 1986/1987, and 1997/1998 and La Ni?a events in 1984/1985, 1988/1989, and 1998/2000 suggests that the ZCWN coupled model is better than the ZCW0 coupled model in predicting warm event evolution and cold event generation. The results also show the disadvantage of the ZCWN coupled model for predicting El Ni?o  相似文献   

极端高温天气对玉米产量的影响及其与大气环流和海温的关系   总被引：1，自引：0，他引：1  

周梦子  王会军  霍治国 《气候与环境研究》2017,22(2):134-148

高温热害已成为玉米生长过程中的一个重要威胁。本文中,我们定量分析了省份尺度上夏季极端高温日数对玉米产量的影响,结果表明在中国不同省份,当高温指数增加一个标准差时,玉米减产范围为-1.56%~-15.06%,其中以东北、华北地区减产最为严重。进一步分析表明,在1990年代中后期东北、华北极端高温日数显著增加,发生突变。当东北、华北上空500 h Pa位势高度场出现正异常时,天气比较晴朗,入射太阳辐射增加,使得地面温度升高,有利于极端高温天气的出现;而风场上,东北地区尤其是黑龙江盛行西风,经向环流减弱,冷空气不易入侵,使得该区温度偏高,华北地区则以偏南风为主,来自中国内陆的温暖气流被带到该地,为极端高温天气的发生创造有利条件。影响东北极端高温天气的关键海域位于黑潮地区,而ENSO对华北极端高温日数的影响更大,当ENSO指数异常偏高时,西太平洋副热带高压偏东,华北水汽输送通道受阻,水汽辐散,且盛行下沉运动,华北地区易出现高温、干旱天气。  相似文献   

Hydrological effects of within-catchment heterogeneity of drainage density     

《Advances in water resources》2015

Local drainage density (dd) has been traditionally defined as the inverse of twice the distance one has to walk before encountering a channel. This formalization easily allows to derive raster-based maps of dd extracted straight off from digital elevation model data. Maps of local dd, which are continuous in space, are able to reveal the appearance of strong heterogeneities in the geological and geomorphological properties of natural landscapes across different scales. In this work we employ the information provided by these spatial maps to study the potential effects of the within-catchment variability of dd on the hydrologic response. A simple power law relationship between runoff yield at the local scale and the value of dd has been adopted; the hypothesis is supported by a large number of past empirical observations and modeling. The novel framework proposed (ddRWF) embeds this spatially variable runoff weight in the well-known Rescaled Width Function (RWF) framework, based on the more general geomorphological theory of the hydrologic response. The model is applied to four sub-basins in the Cascade Range Region (Oregon, USA) where strong contrasts in dissection patterns due the underlain geology have been broadly addressed in previous literature. The ddRWF approach is compared with the classic RWF in terms of shape, moments and peak of the simulated hydrograph response. Results hint that the variability of runoff yield due to the heterogeneity of dd (i.e. of hillslope lengths) determines a more rapid concentration of runoff, which implies shorter lag times, larger skewness and higher peak floods, especially in the case hillslope velocity is much smaller than channel velocity. The potential of the proposed framework relies on accounting for spatially variable losses related to geomorphologic heterogeneity in lumped rainfall–runoff models, still keeping the simple and robust structure of the IUH approach.  相似文献   

A neural network-based ionospheric model for the auroral zone     

《Journal of Atmospheric and Solar》2007,69(12):1459-1470

A new empirical model for the lower ionosphere in the auroral zone, called IMAZ, has been developed, tested and refined for use in the International Reference Ionosphere (IRI) global model. Available ionospheric data have been used to train neural networks (NNs) to predict the high latitude electron density profile. Data from the European Incoherent Scatter Radar (EISCAT), based near Tromsø, Norway (69.58°N, 19.23°E), combined with rocket-borne measurements (from 61° to 69° geomagnetic latitude) make up the database of reliable D- and E-region data.NNs were trained with different combinations of the following input parameters: day number, time of day, total absorption, local magnetic K index, planetary Ap index, 10.7 cm solar radio flux, solar zenith angle and pressure surface. The output that the NNs were trained to predict was the electron density for a given set of input parameters. The criteria for determining the optimum NN are (a) the root mean square (RMS) error between the measured and predicted output values, and (b) the ability to reproduce the absorption they are meant to represent. An optimum input space was determined and then adapted to suit the requirements of the IRI community. In addition, the true quiet electron densities were simulated and added to the database, thus allowing the final model to be valid for riometer absorptions down to 0 dB.This paper discusses the development of a NN-based model for the high-latitude, lower ionosphere, and presents results from the version developed specifically for the IRI user community.  相似文献   

Modulation of decadal ENSO-like variation by effective solar radiation     

《Dynamics of Atmospheres and Oceans》2015

Prediction of the Pacific sea surface temperature (SST) anomaly in the coming decades is a challenge as the SST anomaly changes over time due to natural and anthropogenic climate forcing. The climate changes in the mid-1970s and late-1990s were related to the decadal Pacific SST variability. The changes in the mid-1970s were associated with the positive phase of decadal El Niño-Southern Oscillation (ENSO)-like SST variation, and the changes in the late-1990s were related to its negative phase. However, it is not clear whether this decadal SST variability is related to any external forcing. Here, we show that the effective solar radiation (ESR), which includes the net solar radiation and the effects of volcanic eruption, has modulated this decadal ENSO-like oscillation. The eastern Pacific warming (cooling) associated with this decadal ENSO-like oscillation over the past 139 years is significantly related to weak (strong) ESR. The weak ESR with strong volcanic eruption is found to strengthen the El Niño, resulting in an El Niño-like SST anomaly on the decadal time scale. The strong eruptions of the El Chicho’n (1982) and Pinatubo (1991) volcanoes reduced the ESR during the 1980s and 1990s, respectively. The radiation reduction weakened the Walker circulation due to the “ocean thermostat” mechanism that generates eastern Pacific warming associated with a decadal El Niño-like SST anomaly. This mechanism has been confirmed by the millennium run of ECHO-G model, in which the positive eastward gradient of SST over the equatorial Pacific was simulated under the weak ESR forcing on the decadal time scale. We now experience a reversal of the trend in the ESR. The strong solar radiation and lack of strong volcanic eruptions over the past 15 years have resulted in strong ESR, which should enhance the Walker circulation, leading to a La Niña-like SST anomaly.  相似文献   

Diagnosing the spatiotemporal diversity of westerly wind events in the tropical Pacific     

《Dynamics of Atmospheres and Oceans》2019

Westerly Wind Events (WWEs) over the tropical Pacific are characterized by their spatiotemporal diversity and classified into six types based on their different locations and durations. Various types of WWEs exhibit quite different characteristics in terms of their amplitudes. The long events with a 10–30-day duration are stronger than the short events with a 6–10-day duration, and the maximum amplitudes of the Central-Pacific (C) type and Eastern-Pacific (E) type of long events are larger than the Western-Pacific (W) type of long ones. The evolutions of these six types of WWEs are also quite different. The W-type short and long events and the C-type long events show a distinct eastward propagation, whereas the C-type short events and the E-type short and long events have no apparent propagation direction. We demonstrate that such a difference in the eastward propagation of WWEs can be significantly associated with the Madden-Julian Oscillation (MJO). The W-type events are more influenced heavily by the MJO, as indicated by their more distinct eastward propagation patterns, than the two other types of WWEs. In addition to the MJO, the convectively coupled Kelvin waves are also associated with the WWEs, especially for the short events.  相似文献   

Editorial Board     

《Advances in water resources》1991,14(1):IFC

  相似文献   

Isochron 26Al/10Be burial dating of the Lantian hominin site at Gongwangling in Northwestern China     

《Quaternary Geochronology》2017

The site of Gongwangling is among the most important early hominin sites in China due to the discovery of a partial Homo erectus cranium. Until recently the cranium has been widely accepted as ∼1.15 Ma (million years) in age based on magnetostratigraphy and loess/paleosol correlation. However, a revised magnetostratigraphic and pedostratigraphic study assigned a much older age of 1.63 Ma, making Gongwangling the second oldest hominin cranium-bearing site in Eurasia. Here we apply the isochron burial dating method as an independent check for the magnetostratigraphy. Samples from the top of a gravel bed ∼7 m below the fossil-bearing layer give an isochron burial age of 1.82 ± 0.12 Ma, in excellent agreement with the Olduvai subchron in the revised magnetostratigraphy, supporting the antiquity of the cranium.  相似文献   

1948—2015年北半球平流层爆发性增温的统计特征和月际环流差异          下载免费PDF全文

王华曌  饶建  生宸  王博 《大气科学学报》2019,42(6):880-891

利用NCEP/NCAR第1套再分析资料,分析过去68 a(1948—2015年)平流层爆发性增温(Stratospheric Sudden Warming,SSW)频次、强度和环流特征的月际差异。统计结果表明:1948—2015年北半球共发生30次SSW,其集中发生在11—3月,而1—2月发生频次尤为集中,且SSW发生频次表现出显著的年代际变化特征。11—12月SSW比1—3月SSW的持续时间长。而3月SSW事件的强度最弱,持续时间最短。1月和3月SSW纬向平均信号下传得较深,而11月、12月和2月的环流信号仅能传到200 hPa。11—3月SSW爆发前1～2周500 hPa均观测到西太平洋遥相关型(Western Pacific,WP)的负位相;太平洋-北美遥相关型(Pacific-North America,PNA)的正位相仅仅出现在11月、12月和3月SSW爆发前。SSW爆发后1～2周,仅有11月、1月和3月的事件对应着负位相的北大西洋涛动(North Atlantic Oscillation,NAO)。  相似文献