Signatures of solar activity variability in meteorological parameters

Solar radiation (both total and in various wavelengths) varies at different time scales—from seconds to decades or centuries—as a consequence of solar activity. The energy received from the Sun is one of the natural driving forces of the Earth's atmosphere and since this energy is not constant, it has been argued that there must be some non-zero climate response to it. This response must be fully specified in order to improve our understanding of the climate system and the impact of anthropogenic activities on it. However, despite all the efforts, if and how subtle variations of solar radiation affect climate and weather still remains an unsolved puzzle. One key element that is very often taken as evidence of a response, is the similarity of periodicities between several solar activity indices and different meteorological parameters. The literature contains a long history of positive or negative correlations between weather and climate parameters like temperature, rainfall, droughts, etc. and solar activity cycles like the 27-day cycle, the prominent 11-year sunspot cycle, the 22-year Hale cycle and the Gleissberg cycle of 80–90 years. A review of these different cycles is provided as well as some of the correlative analyses between them and several stratospheric parameters (like stratospheric geopotential heights, temperature and ozone concentration) and tropospheric parameters (like temperature, rainfall, water level in lakes and river flooding, clouds) that point to a relationship of some kind. However, the suspicion on these relationships will remain as long as an indisputable physical mechanism, which might act to produce these correlations, is not available.     

On possible drivers of Sun-induced climate changes

We tested the validity of two current hypotheses on the dependence of climate change on solar activity. One of them states that variations in the tropospheric temperature are caused directly by changes of the solar radiance (total or spectral). The other suggests that cosmic ray (CR) fluctuations, caused by the solar/heliospheric modulation, affect the climate via cloud formation. Confronting these hypotheses with seven different sets of the global/hemispheric temperature reconstructions for the last 400 years, we found that the former mechanism is in general more prominent than the latter. Therefore, we can conclude that in so far as the Sun–climate connection is concerned tropospheric temperatures are more likely affected by variations in the UV radiation flux rather than by those in the CR flux.     

梅雨与北极涛动及平流层环流异常的关联

平流层过程如何影响气候变化是一个大家关注的科学问题,在WCRP中专门设置了一个研究子计划SPARC.本文的分析研究表明,中国的梅雨异常可能受到平流层大气环流异常的影响,而这种影响是通过北极涛动（AO）的变化来实现的.从分析和计算结果可以看到,二月份北半球30 hPa位势高度的EOF第一主分量对应着副热带和高纬度地区的显著下传异常波作用量,其第三主分量对应着极地地区的显著下传异常波作用量,这些下传的异常波作用量都对三月份AO形势的形成有明显的贡献.三月份的AO则会通过影响东亚地区夏季对流层大气的冷暖状况和环流,在长江中下游地区导致异常垂直运动和辐散辐合形势,从而影响夏季的梅雨降水.     

Stratospheric aerosol dynamics over Kamchatka and its association with geophysical processes

The dynamics of aerosol layers in comparison with geomagnetic and ionospheric data has been studied based on the nighttime single-frequency lidar sounding of the atmosphere over Kamchatka at altitudes of 10 to 90 km. The relation of the aerosol density to solar, magnetic, and ionospheric activity has been studied, and the stratospheric aerosol formation mechanisms have been considered. It has been indicated that variations in the aerosol density correlate with radiowave absorption, perturbations of the ionospheric parameters, and geomagnetic characteristics. The spatial and time scales of aerosol layers have been estimated. The role of stratospheric aerosol as an indicator of geophysical processes is discussed.     

Solar variability and its implications for the human environment

Solar variability can affect human activities in a variety of ways, from changing our climate to disrupting power distribution facilities and shortening the orbital lifetime of satellites. This tutorial paper will be concerned only with effects on the surface environment that can have a direct impact on our everyday life, such as variations in the stratospheric ozone layer that shields us from harmful ultraviolet radiation, and changes in global climate that can hinder or delay the detection of climate changes that might result from our own technological activities. The emphasis is on potential mechanisms, rather than on reported correlations between solar and terrestrial parameters, but reference to certain observations will be made. Realization of a potential impact of solar variability on our local environment has progressed a long way in the last few decades, from denial to partial acceptance, but a complete assessment of its reality and magnitude remains a distant goal.     

青藏高原对流层臭氧含量变化的太阳周期活动信号分析

利用1979~1992年卫星TOR对流层臭氧数据库资料,以及同期太阳辐照度数据序列,考察青藏高原对流层臭氧含量变化与太阳辐射周期变化之间的关系.分析表明,青藏高原对流层臭氧分布表现出与太阳辐照度相同的变化趋势,存在着明显的太阳周期变化特征.逐月线性回归分析表明,太阳辐照度增加导致青藏高原对流层臭氧增加的正效应.在太阳周期内,太阳辐射增加可使青藏高原对流层臭氧、平流层臭氧和臭氧总量分别增加1.31、4.97、6.628DU,或4.07%、2.04%、2.28%.该特征与赤道太平洋地区完全相反,分析产生差异的原因,至少应包括两方面因素：一是背景大气NO_X和水汽含量的差异;二是青藏高原频繁发生的平流层-对流层大气物质交换和输送.     

Solar cycle changes to planetary wave propagation and their influence on the middle atmosphere circulation

Recent observations suggest that there may be a causal relationship between solar activity and the strength of the winter Northern Hemisphere circulation in the stratosphere. A three-dimensional model of the atmosphere between 10–140 km was developed to assess the influence of solar minimum and solar maximum conditions on the propagation of planetary waves and the subsequent changes to the circulation of the stratosphere. Ultraviolet heating in the middle atmosphere was kept constant in order to emphasise the importance of non-linear dynamical coupling. A realistic thermo-sphere was achieved by relaxing the upper layers to the MSIS-90 empirical temperature model. In the summer hemisphere, strong radiative damping prevents significant dynamical coupling from taking place. Within the dynamically controlled winter hemisphere, small perturbations are reinforced over long periods of time, resulting in systematic changes to the stratospheric circulation. The winter vortex was significantly weakened during solar maximum and western phase of the quasi-biennial oscillation, in accordance with reported 30 mb geopotential height and total ozone measurements.     

Solar UV variability: Effects on stratospheric ozone,trace constituents and thermal structure

The effect of long-term (11-year solar cycle) solar UV variability on stratospheric chemical and thermal structure has been studied using a time-dependent one-dimensional model. Previous studies have suggested substantial variations in local and total ozone, and in stratospheric thermal structure from solar minimum to solar maximum. It is shown here that significant variations also occur in some of the trace constituents. Members of the HO _x family and N₂O exhibit the largest variations, and these changes, if detected, may provide additional means of verifying the presence of solar UV variability and its effects. Some of the species show large phase differences with the assumed solar flux variation. The role of chemical and transport time constants on the time variations of the trace species is examined. Comparisons with reported ozone and temperature data show reasonable agreement for the period 1960 to 1972.     

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere

The ionospheric D-region (~60 km up to ~95 km) and the corresponding neutral atmosphere, often referred to as the mesosphere–lower thermosphere (MLT), are challenging and costly to probe in situ. Therefore, remote sensing techniques have been developed over the years. One of these is based on very low frequency (VLF, 3–30 kHz) electromagnetic waves generated by various natural and man-made sources. VLF waves propagate within the Earth–ionosphere waveguide and are extremely sensitive to perturbations occurring in the D-region along their propagation path. Hence, measurements of these signals serve as an inexpensive remote sensing technique for probing the lower ionosphere and the MLT region. This paper reviews the use of VLF narrowband (NB) signals (generated by man-made transmitters) in the study of the D-region and the MLT for over 90 years. The fields of research span time scales from microseconds to decadal variability and incorporate lightning-induced short-term perturbations; extraterrestrial radiation bursts; energetic particle precipitation events; solar eclipses; lower atmospheric waves penetrating into the D-region; sudden stratospheric warming events; the annual oscillation; the solar cycle; and, finally, the potential use of VLF NB measurements as an anthropogenic climate change monitoring technique.     

Variations of solar radiation input to the lower atmosphere associated with different helio/geophysical factors

The influence of helio/geophysical factors on the solar energy input to the lower atmosphere has been studied at the network of actinometric stations of Russia in different latitudinal belts. It was found that there are appreciable changes in the half-yearly values of total radiation associated with galactic cosmic ray (GCR) variations in the 11-yr solar cycle, the increase of GCR flux being accompanied by a decrease of the total radiation at higher latitudes and by its increase at lower latitudes. Auroral phenomena and solar flare activity are likely to affect the solar radiation input to the high-latitudinal belt together with GCR variations, the increase of both these factors resulting in the decrease of total radiation. The changes found in the total radiation fluxes in the lower atmosphere seem to be related to the cloud cover variations associated with the solar and geophysical phenomena under study. The variations of the solar radiation input in the 11-yr-cycle amounting to ±4–6% may be an important factor affecting tropospheric dynamics.     

Studies of variations in the vertical ozone profiles over India

The latitudinal and temporal variations in the vertical profiles of ozone over the Indian subcontinent are discussed. In the equatorial atmosphere represented by Trivandrum (8°N) and Poona (18°N), while tropospheric ozone shows marked seasonal variations, the basic pattern of the vertical distribution of ozone in the stratosphere remains practically unchanged throughout the year, with a maximum at about 28 to 26 km and a minimum just below the tropopause. The maximum total ozone occurs over Trivandrum in the summer monsoon season and the latitudinal anomaly observed over the Indian monsoon area at this time is explained as arising from the horizontal transport of ozone-rich stratospheric air from over the thermal equator to the southern regions.In the higher latitudes represented by New Delhi (28°N), the maximum occurs at 23 km. Delhi, which lies in the temperate regime in winter, shows marked day-to-day variations in association with western disturbances and the strong westerly jet stream that lies over north and central India at this time.Although the basic pattern of the vertical distribution of ozone in the equatorial atmosphere is generally the same in all seasons, significant though small changes occur in the lower stratosphere and in the troposphere. There are small perturbations in the ozone and temperature structures, distinct ozone maxima being always associated with temperature inversions. There are also large perturbances not related to temperature, ozone-depleted regions normally reflecting a stratification of either destructive processes or materials such as dust layers or clouds at these levels. Particularly interesting are the upper tropospheric levels just below the tropopause where the ozone concentration is consistently the smallest, in all seasons and at all places where soundings have been made in India.     

A discussion of the chemistry of some minor constituents in the stratosphere and troposphere

A discussion is given of atmospheric reactions in the H₂O–CH₄–O₂–O₃–NO _x system. In the lower troposphere such reactions may lead to significant production of ozone. Their role in the odd hydrogen balance, especially of the troposphere and lower stratosphere, is discussed. CH₃OH may be an intermediate in the oxidation cycle of methane, especially in the cold stratosphere. Its photodissociation into H₂ and CH₂O may consequently provide an important source for stratospheric H₂. Catalytic photochemical chains of reactions involving NO _x and HO _x may also lead to tropospheric destruction of ozone. Due to lack of knowledge it is not possible at present to evaluate the importance of the before-mentioned reactions.With the aid of model calculations it is indicated that stratospheric ozone is most sensitive to changes in the adopted lower boundary values of N₂O and that an increase in water vapour concentrations in the lower stratosphere will indeed cause some increase in ozone as predicted.Fluctuations in the flux of solar radiation near 190 nm may cause significant variations in stratospheric ozone concentrations.     

The geomagenetic storm effect in the middle atmosphere — First results

Summary Geomagnetic storms belong to the most important phenomena of solar origin which affect the ionosphere and atmosphere. We study the responses of the lower ionosphere, middle stratospheric ozone, total ozone and the troposphere (vorticity area index at 500 hPa) to isolated and major geomagnetic storms. The expected positive effect is observed in the lower ionosphere. No observable effect is detected in the middle stratospheric ozone. An effect (not very significant) can be found in the total ozone and the troposphere.Contribution No, 109/90, Geophysical Institute, Czechosl. Acad. Sci., Prague.     

Influence of short-term changes in solar activity on baric field perturbations in the stratosphere and troposphere

Influence of short-term changes in solar activity on baric (pressure) field perturbations is studied using such characteristics as the Sazonov index (IS), describing the intensity of meridional transfer, the Blinova index (IB), describing the intensity of zonal transfer, and ‘vorticity area index’ (VAI) describing the tropospheric cyclonic perturbations. The epoch superposition method is used to reveal effects of the solar central meridian (CM) passage of active regions, the Forbush decreases (FD) in galactic cosmic rays, and the solar proton (SP) events. The results of the analysis show that influence of short-term changes in the solar activity on baric field perturbations is the most evident in the stratosphere (30 mbar-level). The meridional circulation in case of the FD and SP events begin to increase about 5–7 days before the key date, reaches maximum nearby the key date and decays after the key date. The meridional circulation in case of the solar CM passage of active regions starts to increase after the key date and reaches the maximum by 5–6 days. Fluctuations of baric field within periods of 5–7 days typical of meridional and zonal transfers in troposphere (500 mbar-level) are evidently connected with internal dynamics of the atmosphere, not with the effects of solar activity. VAI characterizing cyclonic activity in the troposphere, shows the striking correspondence to changes of the meridional circulation in the stratosphere. Comparison of changes in the stratospheric perturbations with behavior of the UV irradiance in course of the FD and SP events show their full correspondence at the initial stage of these processes. The conclusion is made that growth of baric perturbations observed in the stratosphere in associations with the FD and SP events before the key date is caused by the solar UV irradiance increase, whereas decay of the baric perturbations after the key date is related to direct influence of the solar energetic corpuscular fluxes on the stratosphere.     

Regional millennial trend in the cosmic ray induced ionization of the troposphere

Long-term trends in the tropospheric cosmic ray induced ionization on the multi-millennial time scale are studied using the newly released paleomagnetic reconstruction models. Spatial and temporal variations of the tropospheric ionization has been computed using the CRAC:CRII model and applying the paleomagnetic CALS7k.2 reconstruction. It has been shown that long-term variations of the tropospheric ionization are not spatially homogeneous, and they are defined not only by solar (i.e., covariant with solar irradiance) changes but also by the geomagnetic field. The dominance of the two effects is geographically separated, which makes it possible to distinguish between direct and indirect solar–terrestrial climate effects. Possible climate applications are considered.     

The impact of moderate-scale explosive eruptions on stratospheric gas injections

Volcanic gases such as SO ₂, H ₂S, HCl and COS emitted during explosive eruptions significantly affect atmospheric chemistry and therefore the Earth's climate. We have evaluated the dependence of volcanic gas emission into the atmosphere on altitude, latitude, and tectonic setting of volcanoes and on the season in which eruptions occurred. These parameters markedly influence final stratospheric gas loading. The latitudes and altitudes of 360 active volcanoes were compared to the height of the tropopause to calculate the potential quantity of volcanic gases injected into the stratosphere. We calculated a possible stratospheric gas loading based on different volcanic plume heights (6, 10, and 15 km) generated by moderate-scale explosive eruptions to show the importance of the actual plume height and volcano location. At a plume height of 15 km for moderate-scale explosive eruptions, a volcano at sea level can cause stratospheric gas loading because the maximum distance to the tropopause is 15–16 km in the equatorial region (0–30°). Eruptions in the tropics have to be more powerful to inject gas into the stratosphere than eruptions at high latitudes because the tropopause rises from ca. 9–11 km at the poles to 15–16 km in the equatorial region (0–30°N and S). The equatorial region is important for stratospheric gas injection because it is the area with the highest frequency of eruptions. Gas injected into the stratosphere in equatorial areas may spread globally into both hemispheres.     

AIRS观测的东亚夏季平流层重力波特征

对流性重力波对中层大气环境有显著影响.重力波活动及重力波源的地理和季节性变化等信息是理解和模拟重力波效应的基础.卫星高光谱红外大气垂直探测器AIRS的4μm和15μm波段可用于识别30~40km高度范围和41km高度附近的重力波,其11μm通道可同步观测对流层深对流.观测个例表明,海面和陆面上空的平流层扰动影响范围均可达1000km,不同高度的扰动强度分布也存在差异.基于2007年6月至8月的AIRS观测资料,分析了东亚区域的对流层深对流活动和平流层的重力波,得到了深对流和重力波发生频率的水平分布.统计结果表明,东亚区域夏季夜间的深对流活动明显少于白天,但AIRS观测到的平流层重力波发生频率和扰动强度均显著大于白天,揭示了夜间对流层深对流诱发的平流层重力波在强度、范围等方面可能与白天存在显著差异.进一步对比分析表明,AIRS观测的平流层扰动高值区与深对流高值区明显不同.平流层重力波与对流层深对流之间的相关分析表明,在36°N以南的区域,41km高度上AIRS观测的重力波中,深对流云诱发的重力波的比例约为30%~100%.在10°N至36°N区间,90%的深对流均可诱发平流层重力波.分析得到的30~40km高度区间和41km高度附近的重力波水平分布对比表明,后一高度上的扰动强度明显大于前一高度,且前一高度在东南亚区域存在强扰动中心而在后一高度则没有.最后,给出了AIRS观测的几种典型形态的东亚区域平流层波动,表明了该区域平流层环境波动形态的复杂性和多样性.     

Empirical model of variations in the emission of the Infrared Atmospheric system of molecular oxygen: 3. Temperature

Rotational temperatures of the 1.58-μm (0–1) band of the Infrared Atmospheric system of molecular oxygen (IRAO₂), measured in Zvenigorod (56° N, 36° E), are systematized and analyzed. An empirical dependence of variations in the temperature of the 1.58-μm emission on the solar zenith angle is derived. The use of parameters of the altitude distribution of emission intensity 1.27 μm of middle atmosphere temperature profiles, received from the AURA satellite, allowed for the study of daily variations in the temperature of the 1.58-μm emission. It is revealed that the behavior of these variations corresponds to daily variations in the atmospheric temperature at altitudes of the radiating layer of IRAO₂, received from the AURA satellite.     

A decadal solar effect in the tropics in July–August

The availability of global gridded precipitation and outgoing long-wave radiation (OLR) data after 1978 makes possible an investigation of the influence of the decadal solar oscillation in the tropics during three solar maxima and two solar minima. The NCEP/NCAR reanalyses starting in the 1950s allows the inclusion of an additional two solar maxima and minima to look for consistency of response across a longer time period. In the northern summer (July–August), the major climatological tropical precipitation maxima are intensified in solar maxima compared to solar minima during the period 1979–2002. The regions of this enhanced climatological precipitation extend from the Indian monsoon to the West Pacific oceanic warm pool and farther eastwards in the Intertropical Convergence Zone of the North Pacific and North American Monsoon, to the tropical Atlantic and greater rainfall over the Sahel and central Africa. The differences between solar maxima and minima in the zonal mean temperature through the depth of the troposphere, OLR, tropospheric vertical motion, and tropopause temperature are consistent with the differences in the rainfall. The upward vertical motion is stronger in regions of enhanced tropical precipitation, tropospheric temperatures are higher, tropopause temperatures are lower, and the OLR is reduced due to higher, colder cloud tops over the areas of deeper convective rainfall in the solar maxima than in the minima. These differences between the extremes of the solar cycle suggest that an increase in solar forcing intensifies the Hadley and Walker circulations, with greater solar forcing resulting in strengthened regional climatological tropical precipitation regimes. These effects are as strong or even more pronounced when warm and cold extremes in the Southern Oscillation are removed from the analyses. Additionally, lower stratospheric temperatures and geopotential heights are higher with greater solar forcing suggesting ozone interactions with solar forcing in the upper stratosphere.