Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004–March 2005 and December 2006–March 2007. Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with low chemical content is 6.2 and of lake water with high chemical content is 6.5. The Na+ and Cl? are the most abundantly occurring ions at Antarctica. Considerable amount of SO42? is also found in the surface snow and the lake water which is attributed to the oxidation of DMS produced by marine phytoplankton. Neutralization of acidic components of snow is mainly done by NH4+ and Mg2+. The Mg2+, Ca2+ and K+ are nearly equally effective in neutralizing the acidic components in lake water. The NH4+ and SO42? occur over the Antarctica region mostly in the form of (NH4)2SO4. 相似文献
The time varying conditions in the near-Earth space environment that may affect space-borne or ground-based technological
systems and may endanger human health or life are referred to as space weather. Space weather effects arise from the dynamic
and highly variable conditions in the geospace environment starting from explosive events on the Sun (solar flares), Coronal
Mass Ejections near the Sun in the interplanetary medium, and various energetic effects in the magnetosphere–ionosphere–atmosphere
system. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent
on technological systems vulnerable to the space weather influences, the understanding and prediction of hazards posed by
these active solar events have grown in importance. In this paper, we review the processes of the Sun–Earth interactions,
the dynamic conditions within the magnetosphere, and the predictability of space weather effects on radio waves, satellites
and ground-based technological systems today. 相似文献
The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged
particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic
ray-cloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases
and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the
production of NOx; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature
through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect
the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical
activity of thunderstorms and lightning discharges in relation to climate are discussed. 相似文献
Physical phenomena observed before strong earthquakes have been reported for centuries. Precursor signals, which include radon anomalies, electrical signals, water level changes and ground lights near the epicenter, can all be used for earthquake prediction. Anomalous negative signals observed by ground-based atmospheric electric field instruments under fair weather conditions constitute a novel earthquake prediction approach. In theory, the abnormal radiation of heat before an earthquake produces fair weather around the epicenter. To determine the near-epicenter weather conditions prior to an earthquake, 81 global earthquake events with magnitudes of 6 or above from 2008 to 2021 were collected. According to Harrison's fair weather criteria, in 81.48% of all statistical cases, the weather was fair 6 h before the earthquake; in 62.96% of all cases, the weather was fair 24 h before the event. Moreover, most of these cases without fair weather several hours before the earthquake were near the sea. Among the 37 inland earthquakes, 86.49% were preceded by 6 h of fair weather, and 70.27% were preceded by fair weather for 24 h. We conclude that the weather near the epicenter might be fair for several hours before a strong earthquake, especially for inland events.
During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at
the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate
magnetic storm activity (Σ KP− = 32, KP index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra
of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain.
In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions.
In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler
mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine
parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions. 相似文献
Surface to atmosphere exchange has received much attention in numerical weather prediction models. This exchange is defined by turbulent parameters such as frictional velocity, drag coefficient and heat fluxes, which have to be derived experimentally from high-frequency observations. High-frequency measurements of wind speed, air temperature and water vapour mixing ratio (eddy covariance measurements), were made during the Integrated Ground Observation Campaign (IGOC) of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) at Mahabubnagar, India (16°44′N, 77°59′E) in the south-west monsoon season. Using these observations, an attempt was made to investigate the behaviour of the turbulent parameters, mentioned above, with respect to wind speed. We found that the surface layer stability derived from the Monin–Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds >4 m s?1; under stable regime for wind speeds <2 m s?1 and under neutral regime for wind speeds in the range of 2–3 m s?1. All the three stability regimes were mixed for wind speeds 3–4 m s?1. The drag coefficient shows scatter variation with wind speed in stable as well as unstable conditions. 相似文献
Measurements of the small-, intermediate-, and large-ion concentrations and the air–earth current density along with simultaneous measurements of the concentration and size distribution of aerosol particles in the size ranges 4.4–163 nm and 0.5–20 μm diameter are reported for a drifting snow period after the occurrence of a blizzard at a coastal station, Maitri, Antarctica. Ion concentrations of all categories and the air–earth current simultaneously decrease by approximately an order of magnitude as the wind speed increases from 5 to 10 ms− 1. The rate of decrease is the highest for large ions, lowest for small ions and in-between the two for intermediate ions. Total aerosol number concentration decreases in the 4.4–163 nm size range but increases in the 0.5–20 μm size range with wind speed. The size distribution of the nanometer particles shows a dominant maximum at ~ 30 nm diameter throughout the period of observations and the height of the maximum decreases with wind speed. However, larger particles show a maximum at ~ 0.7 μm diameter but the height of the maximum increases with increasing wind speed. The results are explained in terms of scavenging of atmospheric ions and aerosols by the drifting snow particles. 相似文献
Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and
mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts
have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena
above an active lightning discharge along with the availability of modern technology both for data collection and data analysis
have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the
electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate.
The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their
morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during
lightning discharges couple the lower atmosphere with the ionosphere/magnetosphere. Hence various features of these waves
from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed. 相似文献