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71.
本文阐述平流层气溶胶的光学常数在不同温度下取值时,用Mie散射理论对不同浓度的平流层气溶胶红外波段的辐射特性进行的计算和分析。分析结果表明:在卫星遥感中,由温度引起的平流层气溶胶光学常数的变化对某些红外波段的平流层气溶胶辐射特性的影响是不容忽视的。 相似文献
72.
Based on the observations of a squall line on 11 May 2020 and stratiform precipitation on 6 June 2020 from two X-band dual-polarization phased array weather radars(DP-PAWRs) and an S-band dual-polarization Doppler weather radar(CINRAD/SA-D), the data reliability of DP-PAWR and its ability to detect the fine structures of mesoscale weather systems were assessed. After location matching, the observations of DP-PAWR and CINRAD/SA-D were compared in terms of reflectivity(ZH), radial velocity(V), dif... 相似文献
73.
74.
Naifang BEI Xia LI Qiyuan WANG Suixin LIU Jiarui WU Jiayi LIANG Lang LIU Ruonan WANG Guohui LI 《大气科学进展》2021,38(7):1141-1152
The effects of aerosol–radiation interactions(ARI) are not only important for regional and global climate, but they can also drive particulate matter(PM) pollution. In this study, the ARI contribution to the near-surface fine PM(PM2.5)concentrations in the Guanzhong Basin(GZB) is evaluated under four unfavorable synoptic patterns, including "northlow", "transition", "southeast-trough", and "inland-high", based on WRF-Chem model simulations of a persistent heavy PM pollution episode in January 2019. Simulations show that ARI consistently decreases both solar radiation reaching down to the surface(SWDOWN) and surface temperature(TSFC), which then reduces wind speed, induces sinking motion,and influences cloud formation in the GZB. However, large differences under the four synoptic patterns still exist. The average reductions of SWDOWN and daytime TSFC in the GZB range from 15.2% and 1.04°C in the case of the"transition" pattern to 26.7% and 1.69°C in the case of the "north-low" pattern, respectively. Furthermore, ARI suppresses the development of the planetary boundary layer(PBL), with the decrease of PBL height(PBLH) varying from 18.7% in the case of the "transition" pattern to 32.0% in the case of the "north-low" pattern. The increase of daytime near-surface PM2.5 in the GZB due to ARI is 12.0%, 8.1%, 9.5%, and 9.7% under the four synoptic patterns, respectively. Ensemble analyses also reveal that when near-surface PM2.5 concentrations are low, ARI tends to lower PM2.5 concentrations with decreased PBLH, which is caused by enhanced divergence or a transition from divergence to convergence in an area. ARI contributes 15%–25% toward the near-surface PM2.5 concentrations during the severe PM pollution period under the four synoptic patterns. 相似文献
75.
76.
Sediment infiltration can clog salmon nests and reduce egg survival. As a countermeasure, environmental managers often deploy infiltration traps to monitor sediment infiltration. Traps provide a repeatable means of measuring infiltration and enable comparisons to be made between sites. Results from infiltration rates measured with traps have also been used to estimate infilling rates into salmon nests. Application of these data is questionable, as the composition of the bed and the amount of fine sediment within the bed is known to affect infiltration rates. Thus, infiltration rates measured with infiltration traps may differ from the infiltration rates occurring in redd and riffle gravels. To examine how relationships between sediment infiltration rates varied between four watersheds, we continuously monitored suspended sediment transport, shear stress and infiltration rates at four sites over 5 months. We also compared infiltration rates measured with infiltration traps with changes in the hydraulic conductivity and subsurface grain size distribution of adjacent artificially constructed salmon nests and natural riffle gravels. Among the four watersheds, clear differences in sediment infiltration rates were observed. The differences correlated with the subsurface silt content but no strong relationship existed between land‐use or basin physiography/geology. Despite observing an average of 30 kg m−2 of sediment finer than 2 mm being deposited in the infiltration traps during the study, no change in redd or riffle substrate was observed. If the deposition rates measured with the traps reflect the processes in redds, enough sediment would have been deposited to inhibit egg emergence. However, no reduction in egg survival to the eyed stage was observed. In summary, our results show that infiltration traps with clean gravels can be used to detect intersite differences in sediment transport regimes. Extrapolations of sediment infiltration rates measured with such collectors to estimate infiltration rates in redds or riffles is, however, flawed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
77.
王义文 《吉林大学学报(地球科学版)》1989,(3)
华北地台北缘东段金矿带主要类型金矿床的矿石硫同位素组成受矿源层破同位素背景值制约,成矿与不同时代花岗岩侵入或混合岩化作用引起的成矿物质活化作用有关。深成作用过程中的硫同位素平衡分馏效应使矿石硫稍富S~(34)。热变质过程中的硫同位素扩散分馏效应使矿石流稍富S~(32)。该区太古代层状岩系为金的潜在矿源,具有发现新矿化集中区和新类型金矿床的巨大潜力。根据金矿床硫同位素变化规律可进行深部成矿预测。 相似文献
78.
洛川黑木沟黄土剖面发育了一套完整的黄土地层。据剖面百余块标本粒度资料阐述了Kd=(粉砂(0.05-0.01mm%))/(粘粒(<0.005mm)%)的地质及物理意义。它反映了受风化的粉尘粒组与次生粒组之间的消长关系,Kd值变化既受风尘来源区干湿状况或生物气候条件的制约,又受风化成壤作用的制约。因此,Kd值可视为黄土、古土壤生成环境的一个指标。据Mφ(平均值)由粗到细的变化划为一个粒度旋回,全剖面共分11个旋回。每个旋回反映了一定的岩性地层组合及生物气候环境的变化。 相似文献
79.
Nitrogen and sulfur species in Antarctic aerosols at Mawson,Palmer Station,and Marsh (King George Island) 总被引:4,自引:0,他引:4
D. L. Savoie J. M. Prospero R. J. Larsen F. Huang M. A. Izaguirre T. Huang T. H. Snowdon L. Custals C. G. Sanderson 《Journal of Atmospheric Chemistry》1993,17(2):95-122
High volume bulk aerosol samples were collected continuously at three Antarctic sites: Mawson (67.60° S, 62.50° E) from 20 February 1987 to 6 January 1992; Palmer Station (64.77° S, 64.06° W) from 3 April 1990 to 15 June 1991; and Marsh (62.18° S, 58.30° W) from 28 March 1990, to 1 May 1991. All samples were analyzed for Na+, SO
4
2–
, NO
3
–
, methanesulfonate (MSA), NH
4
+
,210Pb, and7Be. At Mawson for which we have a multiple year data set, the annual mean concentration of each species sometimes vary significantly from one year to the next: Na+, 68–151 ng m–3; NO
3
–
, 25–30 ng m–3; nss SO
4
2–
, 81–97 ng m–3; MSA, 19–28 ng m–3; NH
4
+
, 16–21 ng m–3;210Pb, 0.75–0.86 fCi m–3. Results from multiple variable regression of non-sea-salt (nss) SO
4
2–
with MSA and NO
3
–
as the independent variables indicates that, at Mawson, the nss SO
4
2–
/MSA ratio resulting from the oxidation of dimethylsulfide (DMS) is 2.80±0.13, about 13% lower than our earlier estimate (3.22) that was based on 2.5 years of data. A similar analysis indicates that the ratio at Palmer is about 40% lower, 1.71±0.10, and more comparable to previous results over the southern oceans. These results when combined with previously published data suggest that the differences in the ratio may reflect a more rapid loss of MSA relative to nss SO
4
2–
during transport over Antarctica from the oceanic source region. The mean210Pb concentrations at Palmer and Marsh and the mean NO
3
–
concentration at Palmer are about a factor of two lower than those at Mawson. The210Pb distributions are consistent with a210Pb minimum in the marine boundary layer in the region of 40°–60° S. These features and the similar seasonalities of NO
3
–
and210Pb at Mawson support the conclusion that the primary source regions for NO
3
–
are continental. In contrast, the mean concentrations of MSA, nss SO
4
2–
, and NH
4
+
at Palmer are all higher than those at Mawson: MSA by a factor of 2; nss SO
4
2–
by 10%; and NH
4
+
by more than 50%. However, the factor differences exhibit substantial seasonal variability; the largest differences generally occur during the austral summer when the concentrations of most of the species are highest. NH
4
+
/(nss SO
4
2–
+MSA) equivalent ratios indicate that NH3 neutralizes about 60% of the sulfur acids during December at both Mawson and Palmer, but only about 30% at Mawson during February and March. 相似文献
80.