Vertical fluxes and micrometeorology during aerosol particle formation events

Fluxes of aerosol particles with sizes larger than 10 nm together with fluxes of momentum, sensible and latent heat and CO₂ were measured 10 m above a Scots pine forest with the eddy covariance method. During days when nucleation events were observed particle size distribution measurements showed particle growth from 3 nm sizes to the Aitken mode. Analysis of the experimental data showed systematic differences in fluxes during the days when new particle production was observed compared to other days. During the nucleation events the particle flux measurements showed downward aerosol particle transport, i.e., indicating an elevated source, with respect to the measurement level, of particles larger than 10 nm. Furthermore the turbulence intensity and the heat fluxes were observed to be significantly higher. Evidences of mesoscale circulation were observed in wind speed records as well as in turbulent fluxes on nucleation days. The measurement results show that micrometeorology, the synoptic scale conditions and the particle formation are closely related.     

On the vertical extent of atmospheric feedbacks

This study addresses the question: what vertical regions contribute the most to water vapor, surface temperature, lapse rate and cloud fraction feedback strengths in a general circulation model? Multi-level offline radiation perturbation calculations are used to diagnose the feedback contribution from each model level. As a first step, to locate regions of maximum radiative sensitivity to climate changes, the top of atmosphere radiative impact for each feedback is explored for each process by means of idealized parameter perturbations on top of a control (1?×?CO₂) model climate. As a second step, the actual feedbacks themselves are calculated using the changes modelled from a 2?×?CO₂ experiment. The impact of clouds on water vapor and lapse rate feedbacks is also isolated using `clear sky' calculations. Considering the idealized changes, it is found that the radiative sensitivity to water vapor changes is a maximum in the tropical lower troposphere. The sensitivity to temperature changes has both upper and lower tropospheric maxima. The sensitivity to idealized cloud changes is positive (warming) for upper level cloud increases but negative (cooling) for lower level increases, due to competing long and shortwave effects. Considering the actual feedbacks, it is found that water vapor feedback is a maximum in the tropical upper troposphere, due to the large relative increases in specific humidity which occur there. The actual lapse rate feedback changes sign with latitude and is a maximum (negative) again in the tropical upper troposphere. Cloud feedbacks reflect the general decrease in low- to mid-level low-latitude cloud, with an increase in the very highest cloud. This produces a net positive (negative) shortwave (longwave) cloud feedback. The role of clouds in the strength of the water vapor and lapse rate feedbacks is also discussed.     

Observation of regional new particle formation in the urban atmosphere

Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997–December 2006), in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm⁻³ s⁻¹) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h⁻¹). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere.     

Aerosol spectra and new particle formation observed in various seasons in Nanjing

The aerosol number spectrum and gas pollutants were measured and the new particle formation （NPF） events were discussed in Nanjing. The results showed that the size distributions of aerosol number concen- trations exhibited distinct seasonal variations, implying the relations of particle sizes and their sources and sinks. The number concentrations of particles in the nuclei mode （10-30 nm）, Aitken mode （30-100 nm）, accumulation mode （100 -1000 nm） and coarse mode （〉1μm） varied in the order of summer 〉 spring 〉 autumn, summer 〉 autumn 〉 spring, autumn 〉 summer 〉 spring, and spring 〉 autumn 〉summer, re- spectively. The diurnal variation of total aerosol number concentrations showed three peaks in all observed periods, which corresponded to two rush hours and the photochemistry period at noon. In general, the NPF in summer occurred under the conditions of east winds and dominant air masses originating from marine areas with high relative humidity （50%-70%） and strong solar radiations （400 -700 W m-2）. In spring, the NPF were generally accompanied by low relative humidity （14%-30%） and strong solar radiations （400-600 W m-2）. The new particle growth rates （GR） were higher in the summertime in the range of 10- 16 nm h-1. In spring, the GR were 6.8-8.3 nm h-1. Under polluted air conditions, NPF events were seldom captured in autumn in Nanjing. During NPF periods, positive correlations between 10- 30 nm particles and 03 were detected, particularly in spring, indicating that NPF can be attributed to photochemical reactions.     

Study of dynamics of the cumulonimbus anvil of large vertical extent

Results are presented of analysis of development of a cumulonimbus cloud anvil with the top height exceeding 18 km, as observed in Central India. The anvil development is studied using the measurements from Meteosat-5 and with the WR-100 radar. Minimum air temperature measured from the satellite at the cloud top level is −105°C. The rate of cloud top height growth is, on average, 0.5 m/s. Horizontal extent of the anvil in the steering flow direction reached 85 km, and rate of the anvil propagation in horizontal direction was equal to 32.4 km/h. The anvil area, after the satellite data, reached 3675 km². After the radar data, horizontal extent of the anvil reached 50 km, maximum area being 600 km². Analysis of discrepancies between the satellite and radar measurements of the anvil area shows that a significant part of the anvil cannot be detected by the WR-100 radar because its potential is not enough high; the satellite measurement data improve significantly quality of information on the Cb characteristics.     

1961-2010 年东北地区降水事件时空均匀性研究

利用1961-2010年东北三省和内蒙古四盟90个气象站逐日降水资料,分析了中国东北地区降水事件的气候特征及时空分布均匀性变化。结果表明：近50 a来,东北地区年降水量略有减少,但冬、春季降水量显著增加;考虑降水日数,冬、春季降水量增加主要是由于降水强度的增加,夏、秋季降水量减少主要是由于降水频次的减少。气候变暖的大背景下,虽然年降水量线性变化趋势并不明显,但是降水量年际间分布不均匀性增加,降水有向极端化发展的趋势,夏、秋季表现更为明显,各等级降水事件尤其是降雪在近20 a时间分布明显不均匀。降水量空间均匀性在1993年发生转折突变,突变后空间不均匀性增加,降水日数空间均匀性在1986年发生变率突变,突变后振荡加剧。降水事件时空不均匀性的增加一定程度上造成了东北地区旱涝事件发生可能性增加,不同地域旱涝事件同发现象加剧。     

A new criterion of relative homogeneity of climatological series

Summary When investigating, as a random sample, a series of differences between rather relatively homogeneous series of annual temperatures at two places, about 70 miles distant from one another it can be shown that the frequency distribution of the differences can be approximated by a normal distribution.Conversely, a normal distribution of the elements of the series of differences can be taken as a new criterion for the relative homogeneity of two series of average temperatures. This conclusion is verified by the agreement between other criteria for relative homogeneity and the new one.

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Zusammenfassung Die Häufigkeitsverteilung der Differenzen zweier synchroner Reihen von Jahrestemperaturen wurde untersucht. Sie stammten von zwei zirka 110 km voneinander entfernten Orten in einem einheitlichen (kohärenten) Klimagebiet der Atlantischen Küste der Vereinigten Staaten. Die Häufigkeitsverteilung zeigt eine ausgesprochen negative Schiefe (Abb. 1). Kritische Durchsicht der Differenzenreihe, wie sieJ. v. Hann empfiehlt, zeigte außer einigen mehr oder minder vielleicht unbedeutenden Inhomogenitäten zwei Perioden, die durch scharfe (entgegengesetzte) Diskontinuitäten von der übrigen Reihe abgetrennt erschienen. Die aufgezeigten Sprünge ließen sich im nachhinein durch in der Stationsgeschichte angeführte Aufstellungsänderungen der Instrumente erklären. Die Ausschaltung dieser gestörten Perioden reduzierte die 100jährige auf eine 85jährige Differenzreihe. Die von der letzteren abgeleitete Häufigkeitsverteilung ließ sich in zureichender Weise (Abb. 2) durch eine Gaußsche Kurve approximieren.Die vom Autor zur Prüfung relativer Homogenität verwendeten Kriterien (Abbe, Helmert, Met. Z. S. 1925, p. 482) ergaben das Resultat: nichthomogen im Falle der 100jährigen, und annähernd homogen für die 85jährige Reihe. Dieses Resultat führte zu der Annahme, daß das Problem umkehrbar wäre: wenn die Differenzenreihe sich durch eine Gaußsche Kurve annähernd darstellen läßt, können die ursprünglichen Temperaturreihen als relativ homogen angesehen werden. Weitere mathematisch-statistische Untersuchungen in dieser Richtung wären zu begrüßen, besonders wenn auch Quotientenreihen (Niederschlag) einbezogen würden.

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Résumé En étudiant une série de différences dérivées des séries plus ou moins relativement homogènes de températures annuelles à deux endroits l'un de l'autre à peu près 110 kms comme exemple de hasard, on peut démontrer que la distribution de la fréquence des différences peut être approximée par une distribution normale.Au contraire, une distribution normale des éléments des séries de différences pourrait être considérée comme un nouveau critérium de la homogénéité relative de deux séries de la température moyenne. Cette conclusion est vérifiée par l'accordance avec d'autres critériums.De plus, une continuation des études de ces problèmes au moyen de méthodes statistiques est désirable, en particulier, si l'on peut faire usage aussi de séries de quotients (précipitation).

     

Observation of new particle formation and growth under cloudy conditions at Gosan Climate Observatory,Korea

Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed distinct new particle formation and growth (NPF) events from simultaneous co-located measurements of aerosol and cloud profiles, cloud cover, shortwave radiation, and the number concentration and size distribution of aerosols. The high frequency of NPF was observed at GCO under decreased downwelling solar radiation caused by clouds. Although we observed about 15 and 40 % decreases in downwelling surface shortwave radiations, in the presence of thick mid-level (low-level) clouds, on January 28 and 30, 2012, respectively, distinct NPFs with a growth rate of 3.3 (3.9) nm h^?1 were observed. We examined a 4-year series (May 2008 to April 2012) of continuous measurements of the size distribution of aerosol numbers and visually observed cloud cover. We found that approximately 13 % (i.e., 35 days out of 280 days) of total NPF events were observed under cloud-free conditions (i.e., cloud cover of 0/10). About 20 % (i.e., 57 days out of 280 days) of total NPF events occurred under mostly overcast conditions (i.e., cloud cover of 9/10–10/10). Although NPF events occurring under cloudy conditions were also found elsewhere, the frequency of NPF occurring at GCO seems much higher. The average value of relative humidity for the strong-NPF event days is lower than that of the weak and non-NPF event days for all cloud categories. No significant difference in the condensation sink was found among strong-, weak-, and non-NPF days, but the condensation sink showed a slight decreasing tendency with increasing cloudiness. Further investigations on precursor gases and preexisting aerosols under cloudy conditions are needed.     

Exploring the vertical extent of breaking internal wave turbulence above deep-sea topography

A mooring equipped with 200 high-resolution temperature sensors between 6 and 404 m above the bottom was moored in 1890 m water depth above a steep, about 10° slope of Mount Josephine, NE-Atlantic. The sensors have a precision of less than 0.5 mK. They are synchronized via induction every 4 h so that the 400 m range is measured to within 0.02 s, every 1 s. Thin cables and elliptical buoyancy assured vertical mooring motions to be smaller than 0.1 m under maximum 0.2 m s⁻¹ current speeds. The local bottom slope is supercritical for semidiurnal internal tides by a factor of two. Exploring a one-month record in detail, the observations show: 1/semidiurnal tidal dominance in variations of dissipation rate ε, eddy diffusivity K_z and temperature, but no significant correlation between the records of ε and total kinetic energy, 2/a variation with time over four orders of magnitude of 100-m vertically averaged ε, 3/a local minimum in density stratification between 50 and 100 m above the bottom, 4/a gradual decrease in daily or longer averaged ε and K_z by one order of magnitude over a vertical distance of 250 m, upwards from 150 m above the bottom, 5/monthly mean values of <[ε]> = 2 ± 0.5 × 10⁻⁷ m² s⁻³, <[K_z]> = 8 ± 3 × 10⁻³ m² s⁻¹ averaged over the lower 150 m above the bottom.     

中国及周边海域对流云团的水平和垂直尺度

利用2007年1月-2010年12月CloudSat-CALIPSO二级云产品2B-CLDCLASS-LIDAR,统计中国及其周边海域对流云的发生频率,根据对流云发生频率的分布特征将中国及周边海域划分为青藏高原（TP）、东部陆地（EC）、南部海域（SO）和西北太平洋（WP）4个子区域,并研究了4个子区域积云团和深对流云团的水平尺度和垂直尺度。统计结果表明,海洋积云团的水平尺度约为2 km,陆地积云团的水平尺度约为1 km,海洋下垫面热力性质均匀,积云团尺度更大;陆地下垫面非均匀性强,积云团分布更为零散。深对流云团的水平尺度为10-50 km,东部陆地最大,约为45 km,西北太平洋最小,约为30 km。陆地深对流云团水平尺度较海洋上大,且多尺度特征显著,应该与深对流云发生的复杂天气背景有关。积云团的垂直尺度范围为0.24-2 km,4个区域无明显差异。垂直尺度海洋深对流云团大于陆地云团,其中在南部海域地区最大,约为15 km,青藏高原最小,约为10 km。与陆地云团相比,海洋深对流云团表现为水平尺度更小、垂直尺度更大的中尺度对流体特征。      

基于CloudSat-CALIPSO资料的全球不同类型云的水平和垂直分布特征

云是天气与气候变化的重要影响因子,准确估量云顶高度和云量对分析云特性、降水及强天气预报、估算云辐射强迫等都具有重要意义。利用2006-2010年6-8月CloudSat卫星搭载的微波云廓线雷达（CPR,简称微波雷达）和CALIPSO卫星搭载的云-气溶胶偏振激光雷达（CALIOP,简称激光雷达）的探测资料,分析了全球云顶高度及云量的空间分布特征。结果表明,热带地区微波雷达探测云顶高度平均比激光雷达低约4 km,但均超过12 km;副热带洋面云顶高度在4 km以下,且两部雷达探测的云顶高度差异存在地域性。微波雷达对薄云、云砧及云顶高度低于2.5 km的低云存在漏判,对厚云的云顶高度偏低估;微波雷达探测的全球总云量均值为51.1%,比激光雷达少23.3%;两者给出的云量分布也存在显著的海-陆差异,其中洋面云量差异更大,如微波雷达测出局部洋面云量为80%,而激光雷达的探测结果却超过90%。由于激光雷达发射波长短,对云顶微小粒子比较敏感,而微波雷达波长较长,对相对较小粒子的探测存在局限性。因此,激光雷达对云顶高度的探测优于微波雷达。此结果不仅加强了对激光雷达和微波雷达探测原理的认识,而且进一步理解了云的气候特征。     

太阳高能粒子事件起始释放高度研究

对第23太阳周的太阳高能粒子、米波段和DH波段Ⅱ型射电暴的爆发时间和高度进行了统计分析。结果表明:耀斑和日冕物质抛射(coronal mass ejection,CME)产生后,先后爆发米波、DH波Ⅱ型射电暴和高能粒子事件,它们爆发的高度也由低到高。米波、DH波Ⅱ型射电暴的爆发时间和高度同太阳高能粒子事件是否发生并无明显关系,但伴随米波段和DH波段Ⅱ型射电暴的CME有更高的产生太阳高能粒子事件的概率。     

Evolution of aerosol vertical distribution during particulate pollution events in Shanghai

A set of micro pulse lidar(MPL)systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011.Three typical particulate pollution events(e.g.,haze)were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer(PBL)during these pollution episodes.The aerosol vertical extinction coefficient(VEC)at any given measured altitude was prominently larger during haze periods than that before or after the associated event.Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering,leading to different aerosol vertical distribution structures.Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions.Several peaks in aerosol VECs were found at altitudes above 1 km during the dust-and bioburning-influenced haze events.Aerosol VECs decreased with increasing altitude during the local-polluted haze event,with a single maximum in the surface atmosphere.PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events;subsequently,PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages.The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.     

江苏地区雨雾天气特征及成因研究

利用2010—2016年江苏地区雨雾观测资料,对雨雾天气类型分型、气象要素变化以及成因机制等进行了分析。结果表明：江苏地区雨雾天气类型主要分为倒槽型、冷锋前部型、高压底部型,其中倒槽型发生频率最高;低气压、高湿度、低风速、风向由偏东风或东南风转为偏北风以及前期较高的气温等是雨雾形成的重要气象条件;雨雾形成时江苏地区925 hPa上正变温转为弱的负变温,说明弱冷空气促使了雨雾的发生;边界层低层的弱冷平流有利于水汽凝结和逆温形成,逆温最强时段对应能见度最低阶段;雨雾过程中边界层低层上升、下沉运动均可存在且垂直速度较小。     

Numerical model of the cloud particle isotope composition formation

A non-stationary numerical model for isotope composition formation of cloud particles is developed. The improved model consists of three blocks: hydrothermodynamic, microphysical, and isotope. The latter block contains equations for calculation of isotope content in water vapor and in the cloud particles. The results of the study show that the developed approach can be applied to widen resources for interpretation of surface measurements of hail.