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1.
Abstract

Ground‐based measurements of stratospheric NO2, using absorption spectroscopy of twilight sky in the spectral region 437–451 nm, have been made at Calgary (51.08°N, 114.13°W), Alberta, Canada, during the period December 1978‐March 10, 1979. The NO2 showed a rather steady behaviour in the month of December when there was no stratospheric warming in progress; the monthly average of the afternoon vertical column abundance for December was 1.7 × 1015 cm2. In the rest of the observation period the NO2 showed a complex behaviour, but this behaviour appears to be explicable in terms of the stratospheric circulation changes taking place in that period due to the occurrence of a stratospheric warming event.  相似文献   

2.
Heavy summer rainfall is a primary natural disaster affecting lives and properties in the Korean Peninsula. This study presents a satellite-based rainfall rate retrieval algorithm for the South Korea combining polarization-corrected temperature (PCT) and scattering index (SI) data from the 36.5 and 89.0 GHz channels of the Advanced microwave Scanning Radiometer 2 (AMSR-2) onboard the Global Change Observation Mission (GCOM)-W1 satellite. The coefficients for the algorithm were obtained from spatial and temporal collocation data from the AMSR-2 and groundbased automatic weather station rain gauges from 1 July - 30 August during the years, 2012-2015. There were time delays of about 25 minutes between the AMSR-2 observations and the ground raingauge measurements. A new linearly-combined rainfall retrieval algorithm focused on heavy rain for the PCT and SI was validated using ground-based rainfall observations for the South Korea from 1 July - 30 August, 2016. The validation presented PCT and SI methods showed slightly improved results for rainfall > 5 mm h-1 compared to the current ASMR-2 level 2 data. The best bias and root mean square error (RMSE) for the PCT method at AMSR-2 36.5 GHz were 2.09 mm h-1 and 7.29 mm h-1, respectively, while the current official AMSR-2 rainfall rates show a larger bias and RMSE (4.80 mm h-1 and 9.35 mm h-1, respectively). This study provides a scatteringbased over-land rainfall retrieval algorithm for South Korea affected by stationary front rain and typhoons with the advantages of the previous PCT and SI methods to be applied to a variety of spaceborne passive microwave radiometers.  相似文献   

3.
Factors influencing the18O content of stratospheric H2O are reviewed in order to provide a theoretical framework for the interpretation of measurements of this quantity, which are now becoming available. Depletions in18O of 5–10% in stratospheric H2O are expected based on the known correlation between that of D and18O in tropospheric H2O and observed measurements of large (typically 50%) depletions of D in stratospheric H2O. H2O formed in the stratosphere as a result of oxidation of CH4 can be expected to reflect primarily the18O content of stratospheric O2, which is the same as that of tropospheric O2 (slightly enhanced with respect to standard mean ocean water). Thus, a reduction in the18O depletion is expected with increasing altitude, but not a large enhancement in18O in upper stratospheric H2O as found in recent far infrared measurements. The observed large enhancement of18O in stratospheric O3 is not expected to be reflected in stratospheric H2O. Necessary laboratory data for the improved quantification of these effects are reviewed.  相似文献   

4.
Changes in the frequency of precipitation as a result of a changing climate, as well as anthropogenic induced deposition of nitrogen (N), both have the potential to alter grassland productivity and diversity. Central U.S. weather patterns are dominated by three major air mass trajectories including regional sources from the Gulf of Mexico (marine tropical, Mt), the Pacific Northwest (mild pacific, mP), and the Desert Southwest (continental tropical, Ct). In this work, the Hybrid Single Particle Lagrangian Integrated Trajectory model was used to determine trends in the proportion of precipitation events from these air mass sources from 1983 to 2006 relative to Konza Prairie Biological Station (KPBS), KS. The annual volume-weighted mean (VWM) concentrations and wet deposition of a variety of precipitation dissolved solutes were linked to source regions north or south of KPBS. The proportion of precipitation events from Mt significantly increased, while the proportion of events from Ct and mP decreased significantly over the study period. The annual VWM concentrations of most solutes were typically higher from precipitation sourced to the north of KPBS. However, wet deposition of four ecologically relevant solutes (NH4+, NO3?, H+, and SO4?2) was higher from events from the southern region, likely due to higher precipitation amounts. The proportion of reduced N increased significantly over the study period but was not affected by source region despite the higher use of fertilizers for agriculture in the northern source region. Given the location of this site relative to three dominant air mass paths, future shifts in these patterns will likely impact wet nutrient deposition.  相似文献   

5.
Results of a field experiment on studying solar radiation passing in the visible wavelength range are described with the model aerosol media created in the surface atmosphere. High-efficiency thermocondensation generators were used for creating model aerosol media. The index of refraction and an average size of the aerosol particles formed are close to those characteristic of the natural stratospheric aerosol. The composition and technical characteristics of the equipment complex used in the experiments to control aerosol optical and microphysical parameters and meteorological conditions of the experiment are considered. The Gaussian model of impurity dispersion in the boundary layer is used for the analysis and interpretation of measurement results. It is found that with a number concentration of aerosol particles of ～102–103 cm?3 (which corresponds to the aerosol density in the deposited layer of about 1–10 mg/m2 with the layer thickness along the ray path of about 100 m) the solar radiation attenuation with artificial aerosol layers accounts for 1 to 10%. Model estimates are in satisfactory agreement with the measurement results.  相似文献   

6.
Wang  Yuwei  Huang  Yi 《Climate Dynamics》2020,55(9-10):2343-2350

Whether the stratospheric radiative feedback amplifies the global warming remains under debate. The stratospheric water vapor (SWV), one of the primary feedbacks in the stratosphere, is argued to be an important contributor to the global warming. On the other hand, the overall stratospheric feedback, which consists of both the SWV feedback and the stratospheric temperature (ST) feedback, does not amount to a significant value. The key to reconciling these seemingly contradictory arguments is to understand the ST change. Here, we develop a method to decompose the ST change and to quantify the decomposed feedbacks. We find that the SWV feedback, which consists of a 0.04 W m−2 K−1 direct impact on the top-of-the-atmosphere radiation and 0.11 W m−2 K−1 indirect impact via ST cooling, is offset by a negative ST feedback of − 0.13 W m−2 K−1 that is radiatively driven by the tropospheric warming. This compensation results in an insignificant overall stratospheric feedback.

  相似文献   

7.
The radiative impacts of the stratosphere in global warming simulations are investigated using abrupt CO2 quadrupling experiments of the Coupled Model Inter-comparison Project phase 5 (CMIP5), with a focus on stratospheric temperature and water vapor. It is found that the stratospheric temperature change has a robust bullhorn-like zonal-mean pattern due to a strengthening of the stratospheric overturning circulation. This temperature change modifies the zonal mean top-of-the-atmosphere energy balance, but the compensation of the regional effects leads to an insignificant global-mean radiative feedback (?0.02 ± 0.04 W m?2 K?1). The stratospheric water vapor concentration generally increases, which leads to a weak positive global-mean radiative feedback (0.02 ± 0.01 W m?2 K?1). The stratospheric moistening is related to mixing of elevated upper-tropospheric humidity, and, to a lesser extent, to change in tropical tropopause temperature. Our results indicate that the strength of the stratospheric water vapor feedback is noticeably larger in high-top models than in low-top ones. The results here indicate that although its radiative impact as a forcing adjustment is significant, the stratosphere makes a minor contribution to the overall climate feedback in CMIP5 models.  相似文献   

8.
Rainfall variability and seasonality in northern Bangladesh   总被引：1，自引：1，他引：0  
This paper aimed at the analysis of rainfall seasonality and variability for the northern part of South-Asian country, Bangladesh. The coefficient of variability was used to determine the variability of rainfall. While rainfall seasonality index (SI ) and mean individual seasonality index (\( \overline{SI_i} \)) were used to identify seasonal contrast. We also applied Mann-Kendall trend test and sequential Mann-Kendall test to determine the trend in seasonality. The lowest variability was found for monsoon among the four seasons whereas winter has the highest variability. Observed variability has a decreasing tendency from the northwest region towards the northeast region. The mean individual seasonality index (0.815378 to 0.977228) indicates that rainfall in Bangladesh is “markedly seasonal with a long dry season.” It was found that the length of the dry period is lower at the northeastern part of northern Bangladesh. Trend analysis results show no significant change in the seasonality of rainfall in this region. Regression analysis of \( \overline{SI_i} \) and SI, and longitude and mean individual seasonality index show a significant linear correlation for this area.  相似文献   

9.
Beryllium-7 Deposition and Its Relation to Sulfate Deposition   总被引：2，自引：0，他引：2  
Deposition of 7Be, a cosmogenic radionuclide, was observed at the Meteorological Research Institute in Tsukuba, Japan from 1986 to 1993 and compared with those of several chemical species observed in Tsukuba over the same period. We found a correlation between the monthly depositions of 7 Be and SO 4 2 -, a major acidic species. The correlation was especially strong for late spring and fall, when both species had high depositional fluxes. This correlation was also observed in precipitation samples collected daily in 1992 at the same site. The cause of this correlation is discussed in connection with the fact that the stratospheric aerosol is composed largely of SO 4 2 -. 7 Be is produced in the upper atmosphere, and detection of 7Be, especially in spring and fall in Japan, can be regarded as detection of stratospheric aerosol. However, we conclude that the bulk of the SO 4 2 - observed did not have a stratospheric or an upper tropospheric origin. The correlation, therefore, may present a new question regarding acidic deposition: Why does the deposition of stratospheric aerosol in Japan coincide with that of nss-SO 4 2 - originally from anthropogenic sources on the Earth's surface?  相似文献   

10.
The levels of PM.25 PAHs at Mt. Halla site, Jeju Island, a background site in Korea were observed between March 1999 and March 2002. A seasonal variation was observed for the particulate PAHs concentrations with high levels during cold season similar to Gosan, a nearby coastal background site, due to the seasonal variations of fossil fuel usage in Asia. The total average concentration of ambient particulate PAHs was 404 ± 579 pg m− 3, about one order lower than the ambient level at Gosan. However, the ratios of the anthropogenic inorganic ion concentrations between Mt. Halla and Gosan were smaller, 1.5 for non sea-salt (nss) sulfate and 2.7 for nitrate. Two possible explanations for these characteristics are (1) two sites measured different air parcels and/or (2) the effect of local emissions were different at two sites. Based on the Bep/BaP ratio result, upper air wind direction data, backward trajectory analysis, and LIDAR measurement data at Gosan, it was found that the degree of the effects of local emissions to the sampling sites be the major reason for the different PAHs levels at two sites though, in some cases, the air parcels arriving at Mt. Halla were different from those arriving at Gosan. For secondary aerosol such as nss sulfate, the lower concentration difference indicates both site are affected by regional transport. It points that the measurement result for directly emitted species such as PAHs at Gosan might be significantly influenced by local emissions.  相似文献   

11.
Cloud events whose wet deposition is comparable to that shown to trigger negative health symptoms in trees constitute environmentally significant episodes of wet deposition. They accounted for approximately one fourth of all cloud events that traversed the Mt. Mitchell State Park, NC, during the summer field seasons of 1986–1988 and 1993. The environmentally significant episodes of wet deposition most frequently occurred during the month of June. The June occurrence is equivalent to the frequency of acid mist treatments shown to initiate health related decline in Red Spruce. The slightly more than three seasons of data were analyzed for a possible relationship between cloudwater acidity, liquid water content, wind speed and wind direction. The data analysis shows: (i) A scatter plot of the liquid water flux versus the H+ ion flux differentiates between environmentally significant and non-environmentally significant cloud events of wet deposition. (ii) The synoptic and resulting local wind speed and direction are important in determining whether a cloud event will be environmentally significant or not, since they are related to the origin and the approach of the airflow into the Mt. Mitchell site. (iii) A characteristic 850 mb height field associated with the most frequently occurring environmentally significant cloud only event of wet deposition. Further investigation of wet acidic deposition episodes capable of damaging Red Spruce in the Mt. Mitchell State Park  相似文献   

12.
Grain yields of wheat and maize were obtained from national statistics and simulated with an agricultural system model to investigate the effects of historical climate variability and irrigation on crop yield in the North China Plain (NCP). Both observed and simulated yields showed large temporal and spatial variability due to variations in climate and irrigation supply. Wheat yield under full irrigation (FI) was 8?t?ha?1 or higher in 80% of seasons in the north, it ranged from 7 to 10?t?ha?1 in 90% of seasons in central NCP, and less than 9?t?ha?1 in 85% of seasons in the south. Reduced irrigation resulted in increased crop yield variability. Wheat yield under supplemental irrigation, i.e., to meet only 50% of irrigation water requirement [supplemental irrigation (SI)] ranged from 2.7 to 8.8?t?ha?1 with the maximum frequency of seasons having the range of 4?C6?t?ha?1 in the north, 4?C7?t?ha?1 in central NCP, and 5?C8?t?ha?1 in the south. Wheat yield under no irrigation (NI) was lower than 1?t?ha?1 in about 50% of seasons. Considering the NCP as a whole, simulated maize yield under FI ranged from 3.9 to 11.8?t?ha?1 with similar frequency distribution in the range of 6?C11.8?t?ha?1 with the interval of 2?t?ha?1. It ranged from 0 to 11.8?t?ha?1, uniformly distributed into the range of 4?C10?t?ha?1 under SI, and NI. The results give an insight into the levels of regional crop production affected by climate and water management strategies.  相似文献   

13.
A programme of ground-based stratospheric and total NO2 column measurements was instituted at the Laboratory of Atmospheric Physics (40.5° N, 22.9° E) in August 1985. We present here the results of the first two years of measurements with a modified Canterbury filter photometer, details of which are given in the text. The stratospheric NO2 column, obtained at twilight during low local NO2 levels, shows the seasonal variation with monthly mean values of about 6×10-15 molec. cm-2 in the summertime to about 2.2×10-15 molec. cm-2 in the wintertime. These measurements compare well with measurements obtained with different instruments by other groups at similar latitudes (about 40° N) but in different places. Also, the asymmetry of the evening-to-morning stratospheric NO2 over Thessaloniki was found to be on the average equal to 1.58. Total NO2 column over Thessaloniki has a pronounced seasonal variation with amplitude of 0.68 matm. cm which can be explained partly from measured local NO2 sources which discharge in the mixing layer and partly from photolysis of the NO2 reservoir species.  相似文献   

14.
利用中尺度大气化学模式WRF/Chem对2013年3月6日华南地区一次平流层入侵事件及其对对流层低层臭氧的影响进行模拟研究。通过加入UBC（Upper Boundary Condition）上边界处理方案,弥补WRF/Chem模式未考虑平流层臭氧化学反应的不足。结合臭氧探空廓线资料、地面O3、CO、NOx、相对湿度、温度和风速等观测资料以及再分析资料对模拟结果进行定量评估,结果表明模式能较为真实地模拟本次平流层入侵过程。模拟分析进一步揭示:（1）副热带高空急流是本次平流层入侵的主要原因。当华南地区处在副热带急流入口区左侧下沉区域时,平流层入侵将富含臭氧的干燥空气输送到对流层中低层。（2）本次平流层入侵对对流层低层臭氧收支有重要影响,导致香港地区近地层臭氧体积混合比浓度明显上升,如塔门站夜间臭氧浓度升高21.3 ppb（1 ppb=1×10-9）。地面气象场和化学物种的分析进一步确认了平流层入侵的贡献。（3）采用动力学对流层顶高度时零维箱式模型和Wei公式计算得到的平流层入侵通量相当,分别为-1.42×10-3 kg m-2 s-1和-1.59×10-3 kg m-2 s-1,这一结果与前人研究相吻合,且与采用热力学对流层顶高度计算所得到的结果具有可比性。  相似文献   

15.
During a series of flights in the winters 1991/92 to 1994/95 total stratospheric NO2 was measured by means of the DOAS (Differential Optical Absorption Spectroscopy) technique on board a C160 (Transall) aircraft. In an area covering 60°W to 60°E, and 16°N to 86°N, the total stratospheric NO2 was observed to vary markedly with latitude and season (winter and spring). In the mid-winter Arctic vortex extremely low total stratospheric NO2 (< 3.1014/cm2) was always found, generally larger amounts of NO2 occurred outside the vortex in winter and towards the spring both inside and outside the vortex. This behaviour of stratospheric NO2 can be explained by the denoxification of the wintertime polar stratosphere. Ambient to the vortex in mid-winter however, sudden increases of total stratospheric NO2 by about a factor of 3 were observed. These sudden increases in stratospheric NO2 coincide with a change in the wavenumber 2 of the geopotential height at 60°N, which indicates that most likely the events are caused by planetary waves efficiently transporting air masses rich in NOx from lower to higher latitudes. The monitoring of stratospheric NO2, during latitudinal traverses ranging from the Arctic (80°N) to the Subtropics (18°N) in spring also unexpectedly showed a large variability in total stratospheric NO2 at mid-latitudes. Since photochemistry almost certainly can be excluded, it is proposed that the observed variability may be due to the planetary wave activity of the stratospheric surf zone, known to dynamically connect the tropical and the polar stratosphere.  相似文献   

16.
New laboratory measurements of NO2 absorption cross-section were performed using a Fourier transform spectrometer at 2 and 16 cm-1 (0.03 and 0.26 nm at 400 nm) in the visible range (380–830 nm) and at room temperature. The use of a Fourier transform spectrometer leads to a very accurate wavenumber scale (0.005 cm-1, 8×10-5 nm at 400 nm). The uncertainty on the new measurements is better than 4%. Absolute and differential cross-sections are compared with published data, giving an agreement ranging from 2 to 5% for the absolute values. The discrepancies in the differential cross-sections can however reach 18%. The influence of the cross-sections on the ground-based measurement of the stratospheric NO2 total amount is also investigated.  相似文献   

17.
Near real-time measurements of PM2.5 ionic compositions were performed at the summit of the highest mountain in the central-eastern plains in the spring and summer of 2007 in order to characterize aerosol composition and its interaction with clouds. The average concentrations of total water soluble ions were 27.5 and 36.7 μg?m?3, accounting for 44% and 62% of the PM2.5 mass concentration in the spring and summer, respectively. A diurnal pattern of SO 4 2- , NH 4 + and NO 3 - was observed in both campaigns and attributed to the upslope/downslope transport of air mass and the development of the planetary boundary layer (PBL). The average SO2 oxidation ratio (SOR) in summer was 57% (±27%), more than twice that in spring 24% (±16%); the fine nitrate oxidation ratio (NOR) was comparable in the two seasons (9?±?6% and 11?±?10% in summer and spring, respectively). This result indicates strong summertime production of sulfate aerosol. A principal component analysis shows that short-range and long-range transport of pollution, cloud processing, and crustal source were the main factors affecting the variability of the measured ions (and other trace gases and aerosols) at Mt. Tai. Strong indications of biomass burning were observed in summer. Cloud scavenging rates showed larger variations for different ions and in different cloud events. The elevated concentrations of the water soluble ions at Mt. Tai indicate serious aerosol pollution over the North China plain of eastern China.  相似文献   

18.
This case study investigates a stratospheric intrusion event down to the earth’s surface (near sea-level pressure) of the greater area of Athens (23.43°E 37.58°N), which occurred on 9 October 2003 and caused a remarkable increase in surface ozone concentrations not related to photochemical production. This event is among the rare case studies investigating, on the one hand, a deep stratospheric intrusion down to the earth’s surface at near sea-level pressure and, on the other, an event affecting the near surface ozone of a megacity such as Athens. The synoptic situation is described by a deep upper lever trough at 300 and 500 hPa extending over Greece, which is related to a deep tropopause fold as revealed by vertical cross sections of potential vorticity, relative humidity, divergence and vertical velocity. The analysis of potential vorticity at several isentropic levels indicates a hook-shaped streamer of high PV values (greater than 4 pvu at the 315 K isentropic level) over southeast Europe, which coincides with a streamer of dry air as observed from satellite images of water vapor. The aforementioned structure characterizes a textbook case study of stratosphere-to-troposphere transport. The Lagrangian particle dispersion model FLEXPART was used to calculate the trajectories of air particles reaching the receptor site and the fraction of particles with stratospheric origin. It reveals an important direct stratospheric impact within 1 day related to the tropopause fold described in this study with the fraction of stratospheric particles reaching maximum values of 1.9 and 4.5% for threshold values of the dynamical tropopause 2 and 1.5 pvu, respectively. Furthermore, a larger indirect aged stratospheric contribution is also revealed 4 to 5 days prior to the release, related to stratospheric intrusion events at the western Atlantic Ocean, reaching maximum values of 2.5 and 6.9% of particles crossing the 2 and 1.5 pvu potential vorticity surfaces, respectively.  相似文献   

19.
对1980～2014年中国中东部地区324个台站的持续性霾天气的时空变化和相关气象影响因子进行分析，结果表明:中东部地区年平均持续性霾事件和其在所有霾事件的贡献比例逐年增加，增长率分别为0.79 (10 a)-1和2.7% (10 a)-1。主要表现为3个大值区:华北平原地区（包括山西省、京津冀地区）、长江三角洲和四川盆地东部，增加最显著的区域位于黄淮地区，增长率分别为6.3 (10 a)-1、13.95 d (10 a)-1。1月是持续性霾事件的高发月，月均2.56 d。夏季和秋季持续性霾事件增加最为明显，增长率分别为0.38 (10 a)-1和0.46 (10 a)-1。不利的气象条件，如静风日数的增加，风速和大风日数的减少，以及不利的环流形势，如东亚冬季风的减弱，都可能造成持续性霾天气的增加和异常维持。  相似文献   

20.
The effects of E1Nifio Modoki events on global ozone concentrations are investigated from 1980 to 2010 E1 Nifio Modoki events cause a stronger Brewer-Dobson （BD） circulation which can transports more ozone-poor air from the troposphere to stratosphere, leading to a decrease of ozone inthe lower-middle stratosphere from 90~S to 90~N. These changes in ozone concentrations reduce stratospheric column ozone. The reduction in stratospheric column ozone during E1 Nifio Modoki events is more pronounced over the tropical eastern Pacific than over other tropical areas because transport of ozone-poor air from middle-high latitudes in both hemispheres to low latitudes is the strongest between 60°W and 120°W. Because of the decrease in stratospheric column ozone during E1 Nifio Modoki events more UV radiation reaches the tropical troposphere leading to significant increases in tropospheric column ozone An empirical orthogonal function （EOF） analysis of the time series from 1980 to 2010 of stratospheric and tropospheric ozone monthly anomalies reveals that： E1 Nifio Modoki events are associated with the primary EOF modes of both time series. We also found that E1 Nifio Modoki events can affect global ozone more significantly than canonical E1 Nifio events. These results imply that E1 Nifio Modoki is a key contributor to variations in global ozone from 1980 to 2010.  相似文献   

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