Plasma electron temperature variability in lunar surface potential and in electric field under average solar wind conditions

The Moon is immersed in plasma environment. The most interesting challenge of the lunar plasma– field environment is that it is alternatively dominated by the extended but variable outer atmosphere of the Earth – the magnetosphere – and by the extended but highly variable solar atmosphere – the solar wind. Understanding the plasma environment and its interaction with the lunar surface will be beneficial to both manned and robotic surface exploration activities and to scientific investigations. Presented is a preliminary map of variations of lunar surface electric potential over the day side and night side using probe equations and a discussion on dust dynamics in this E-field structure using the data from Electron Reflectometer in Lunar Prospector spacecraft during 1998–1999. On the day side, potential is around 5 V and on the night side it reaches up to −82 V. On the night side region, only highly energetic electrons can overcome this large negative potential. The variation at electron temperature (T_e) strongly reflects in the surface potential. The potential reaches to a value of −82 V for T_e = 58 eV. Surface charging causes the electrostatic transport of charged dust grains. Dust grain size of 0.1 μm shows a levitation height of 4.92 m on lunar day side, 748 m on terminator region and 3.7 km on the night side. The radius of maximum sized grain to be lofted, R_max, peaks at the terminator region (R_max = 0.83 μm). At the transition region dust levitation is almost absent. This region is most suited for exploration activities as the region is free from hazards caused by lunar dust.     

Surface temperatures at the nearside of the Moon as a record of the radiation budget of Earth’s climate system

Understanding the balance between incoming radiation from the Sun and outgoing radiation from Earth is of critical importance in the study of climate change on Earth. As the only natural satellite of Earth, the Moon is a unique platform for the study of the disk-wide radiation budget of Earth. There are no complications from atmosphere, hydrosphere, or biosphere on the Moon. The nearside of the Moon allows for a focus on the solar radiation during its daytime, and on terrestrial radiation during its nighttime. Additionally, lunar regolith temperature is an amplifier of the terrestrial radiation signal because lunar temperature is proportional to the fourth square root of radiation as such is much more sensitive to the weak terrestrial radiation in nighttime than the strong solar radiation in daytime. Indeed, the long-term lunar surface temperature time series obtained inadvertently by the Heat Flow Experiment at the Apollo 15 landing site three decades ago may be the first important observation from deep space of both incoming and outgoing radiation of the terrestrial climate system. A revisit of the lunar surface temperature time series reveals distinct characteristics in lunar surface daytime and nighttime temperature variations, governed respectively by solar and terrestrial radiation.     

Simultaneous measurements of sea surface temperature by GMS-1 and GMS-2

For accurate measurements of sea surface temperature in the 11 μm window region, it is necessary to eliminate the effect of atmospheric absorption. A technique using observations from different angles is one of the methods of eliminating this atmospheric effect. This technique is not possible at present, using a single satellite; but using two geosynchronous satellites, it is possible to observe a common area from two different elevation angles. To correct for atmospheric effects, therefore, we compared the infrared data obtained from observations at about the same time (less than a minute apart) on the equator using the GMS-1 and GMS-2 satellites which had about 20° longitudinal separation. It was found that if the infrared spectral wavelength channel of one geosynchronous satellite is selected to be different from that of the other, it is possible to improve the two-satellite observation technique of estimating water vapor content in a tropical atmosphere. This technique corresponds to split window measurements by the AVHRR radiometer on board the NOAA-7 satellite.     

Estimation of sea surface temperature, wind speed and water vapor with microwave radiometer data based on simulated annealing

A method for estimation of sea surface temperature, ocean wind speed and water vapor with microwave radiometer data based on simulated annealing is proposed. The proposed method shows about 60% improvement of sea surface temperature estimation accuracy in comparison to the existing method using Newton’s iterative algorithm.     

Plan for the implementation of the world climate research programme

The objectives of the World Climate Research Programme (WCRP) are expressed in terms of increasing time scales, from several weeks to several decades. The Programme calls for substantial developments in modelling the interaction of the global atmosphere with the ocean, land surface and sea-ice, as well as improved computations of radiation transfer in the presence of clouds, aerosols and absorbing gases. These developments require a large variety of space as well as surface based observations, and especially, additional efforts for systematic processing of available data to produce consistent records of significant climatological variables. The forthcoming development of a new generation of ocean observing satellites will be an essential component of the WCRP, as they will provide the data base for the large-scale oceanographic projects, the World Ocewan Circulation Experiment (WOCE) and the study of thew Tropical Ocean and the Global Atmosphere (TOGA).     

Anomalous increase of chlorophyll concentrations associated with earthquakes

Recent studies have shown land, ocean, atmosphere and ionospheric anomalies prior to earthquakes. The optical and microwave sensors onboard satellites are now capable of monitoring land, ocean, atmosphere and ionosphere which provide changes associated with natural hazards. In this paper, we have analyzed remote sensing data of the ocean coasts lying near the epicenters of recent four major earthquakes (Gujarat of January 26, 2001, Andaman of September 13, 2002, Algeria of May 21, 2002 and Bam, Iran earthquake of December 26, 2003), our detailed analysis shows increase of Chlorophyll-a (Chl-a) concentration associated with these recent earthquakes. The increase of Chl-a concentration is due to the change in sea surface temperature (SST) associated with the changes in stress regime in the epicentral region which is responsible for modifying the in situ thermal structure of the water and enhancing the upwelling of nutrient-rich water. The increase of Chl-a concentration also shows one to one relation with the increase of surface latent heat flux (SLHF) which is found to increase significantly prior to the earthquake events. Due to cloud cover, it has not been possible to quantify the effect of the chlorophyll concentrations associated with the earthquake events for each successive day during an event. However, the limited data from the adjacent oceanic regions provide strong evidence of the increase in Chl-a concentration. The monitoring of chlorophyll concentrations with higher spatial and temporal resolutions may provide early information about impending coastal earthquakes.     

Sterilisation properties of the Mars surface and atmospheric environment.

The radiative and chemical conditions at the surface and in the lower Martian atmosphere are computed at various latitudes and seasons combining a 2D photochemical model and radiation simulations. In most situations, the solar UV B and C radiations reach the surface however, suspended dust and, in polar cases, ozone can constitute an effective UV shield. The daytime and night time concentrations of the sterilizing oxidants: OH, H2O2 and O3 are determined, as well as the concentration of the substances which could influence the metabolism of microorganisms. The possible habitats of a remaining Mar's life as well as the possibilities of contamination by resistant earth life forms will be described.     

Seasonal-to-interannual variability of chlorophyll-a bloom timing associated with physical forcing in the Gulf of Cádiz

Seasonal-to-interannual variability of the winter-spring bloom in the Gulf of Cádiz, eastern North Atlantic, has been investigated using chlorophyll-a remote sensing (CHL). These data have been obtained from the GlobColour project; the temporal coverage extends from September 1997 to December 2010. In this study we develop a generic quantitative approach for describing the temporal variability in the shape of the winter-spring bloom within a region. Variability in both the timing and magnitude of the bloom in the basin has been evaluated as a function of physical properties in the water column such as Mixed Layer Depth (MLD, GODAS model), sea surface temperature (SST, from AVHRR radiometers), photosynthetically-active radiation (PAR, from ocean color data) and euphotic depth (Z_eu, from ocean color data). The analysis indicated that the timing, size and duration of the phytoplankton bloom in this area are largely controlled by both meteorological and oceanographic conditions at different scales; this means that it is likely to vary widely from one year to another.     

The effect of aerosols on climate and aerosol climatology on the basis of observations from space

Principal aspects of the effect of aerosols on climate are discussed and the possibilities of obtaining a climatic data set of global aerosols are analyzed. Based on the analysis of space images, new data have been obtained on gigantic dust outbreaks in various regions of the Earth. It has been shown that dust outbreaks can propagate over hundreds and sometimes thousands of kilometers. The western Sahara - Atlantic Ocean is the major region of propagation of these outbreaks. The continent-to-continent trajectories of dust clouds have been discovered (from Africa to the coast of America, from Central Asia to the Pacific Ocean). Maps of the sources of strong dust transformations have been studied and drawn. In particular, an anthropogenic dust source has been found out on the northeastern coast of the Aral Sea. A striped mesostructure of dust formations has been analyzed, determined by both the inhomogeneous surface and peculiarities of the eddy dust transport. The techniques have been discussed in detail for retrieving the parameters of aerosol size distribution and the vertical profiles of the coefficients of aerosol extinction in the stratosphere and lower mesosphere from the data on the brightness of the twilight and daytime horizon as well as occultation measurements of solar radiation attenuation by the atmosphere.The difficulty of reliably predicting possible environmental changes arises both from the problems of estimating complex interactions of numerous processes and from a lack of information concerning various environmental parameters. For example, an important factor in present day climatic changes is the increased dust content of the atmosphere due to man's activities. However, a reliable estimate of this influence is found to be impossible due to the absence of definitive data on the global distribution of atmospheric dust and the properties of dust in various parts of the world [4,5,13–15]. The impact of aerosols on climate has been discussed in detail in a number of monographs [12–15].Observations from space have opened up new possibilities for studying atmospheric dust. For this purpose, both the imagery and spectrometry of the Earth's atmosphere from space are used. Rather attractive are the prospects for laser sounding [1].     

Possible DC electric field in the ionosphere related to seismicity

This paper presents the method for calculation of DC electric field in the atmosphere and the ionosphere generated by model distribution of external electric current in the lower atmosphere. Appearance of such current is associated with enhancement of seismic activity that is accompanied by emanation of soil gases into the atmosphere. These gases transfer positive and negative charged aerosols. Atmospheric convection of charged aerosols forms external electric current, which works as a source of conductivity current in the atmosphere–ionosphere electric circuit. It is shown that DC electric field generated in the ionosphere by this current reaches up to 10 mV/m, while the long-term vertical electric field disturbances excited near the Earth surface do not exceed 100 V/m. Such limitation of the near-ground field is caused by the formation of potential barrier for charged particles at the Earth surface in a process of their transport from soil to atmosphere.     

红外窗口材料的热辐射特性测量方法

飞行器在大气层内高超声速飞行时,高温窗口迅速成为气动热辐射效应的主要因素,气动热辐射效应会降低甚至破坏红外(IR)探测系统的性能.通过分析红外探测窗口热辐射传输特性,提出一种红外窗口材料的热辐射特性测量方法,并测量了应用于中波红外(MWIR)探测系统的某蓝宝石红外窗口材料在高温状态下的透过率和自身辐射等热辐射数据.结果表明:在100~350℃范围内,0.1mm厚蓝宝石材料薄层在中波红外3.7~4.8μm波段的热辐射特性与温度近似呈3次方关系,温度越高,蓝宝石透过率越小,自身辐射越大.强烈的自身辐射极易导致红外探测器局部饱和现象,对探测系统造成的影响比透过率引起的信噪比(SNR)下降要大得多.      

Satellite measurements of tropospheric aerosols

The ability to measure tropospheric aerosols over ocean surfaces has been demonstrated using several different satellite sensors. Landsat data originally showed that a linear relationship exists between the upwelling visible radiance and the aerosol optical thickness (about 90% of this thickness is generally in the lowest 3 km of the atmosphere). Similar relationships have also been found for sensors on GOES, NOAA-5 and NOAA-6 satellites. The linear relationship has been shown theoretically to vary with the aerosol properties, such as size distribution and refractive index, although the Landsat data obtained at San Diego showed little variability in the relationship. To investigate the general applicability of the technique to different locations, a global-scale ground-truth experiment was conducted in 1980 with the AVHRR sensor on NOAA-6 to determine the relationship at ten ocean sites around the globe. The data for four sites have been analyzed, and show excellent agreement between the aerosol content measured by the AVHRR and by sunphotometers at San Diego, Sable Island and San Juan, but at Barbados, the AVHRR appears to overestimate the aerosol content. The reason for the different relationship at the Barbados site has not been definitely established, but is most likely related to problems in interpreting the sunphotometer data rather than to a real overestimation by the AVHRR. A preliminary analysis of AVHRR Channel 1 (0.65 μm) and Channel 2 (0.85 μm) radiances suggest that useful information on the aerosol size distribution may also be obtained from satellite observations.     

基于钠激光雷达观测数据的中间层顶大气温度分布特性研究

作为中间层和热层的边界层,中间层顶存在多种能量交换方式,是大气能量耦合的重要区域。本文利用部署于中国科学院廊坊临近空间大气探测站的钠荧光多普勒激光雷达2013年的观测数据,研究了廊坊上空中间层顶区域大气温度的年度和季节分布特性,并分析了影响温度分布的多种因素。年平均温度廓线图显示,中间层顶位于约97.5 km高度处,温度约191.2 K。受放热化学反应的影响,年平均温度廓线91 km高度处出现了一个198 K的相对温度高点。中间层顶区域大气温度的季节分布受太阳辐射和大气动力学因素综合影响,夏季在大气动力学影响下,中间层顶高度较低,位于88 km高度处,温度也较低,约177 K;冬季太阳辐射起主导作用,中间层顶位于99 km高度处,温度为181 K。通过拟合月平均温度分析了中间层顶区域大气温度年变化和半年变化的振幅和相位特征。结果显示,中间层顶区域上部温度分布主要受太阳辐射的影响;在中间层顶区域下部,大气波动主导了温度分布。      

Total column water vapor estimation over land using radiometer data from SAC-D/Aquarius

The aim of this study is retrieving atmospheric total column water vapor (CWV) over land surfaces using a microwave radiometer (MWR) onboard the Scientific Argentine Satellite (SAC-D/Aquarius). To research this goal, a statistical algorithm is used for the purpose of filtering the study region according to the climate type.A log-linear relationship between the brightness temperatures of the MWR and CWV obtained from Global Navigation Satellite System (GNSS) measurements was used. In this statistical algorithm, the retrieved CWV is derived from the Argentinian radiometer’s brightness temperature which works at 23.8?GHz and 36.5?GHz, and taking into account CWVs observed from GNSS stations belonging to a region sharing the same climate type. We support this idea, having found a systematic effect when applying the algorithm; it was generated for one region using the previously mentioned criteria, however, it should be applied to additional regions, especially those with other climate types.The region we analyzed is in the Southeastern United States of America, where the climate type is Cfa (Köppen - Geiger classification); this climate type includes moist subtropical mid-latitude climates, with hot, muggy summers and frequent thunderstorms. However, MWR only contains measurements taken from over ocean surfaces; therefore the determination of water vapor over land is an important contribution to extend the use of the SAC-D/Aquarius radiometer measurements beyond the ocean surface. The CWVs computed by our algorithm are compared against radiosonde CWV observations and show a bias of about ?0.6?mm, a root mean square (rms) of about 6?mm and a correlation of 0.89.     

Retrieval of aerosol optical characteristics from polarization measurements of reflected solar radiation above the oceans

The reflected near infrared solar radiation observed from space above the oceans is due mainly to the atmosphere scattering, as the ocean surface is nearly black. The molecular Rayleigh contribution is also minimized at infrared wavelengths and it can be evaluated. It is shown that the degree of polarization is much more sensitive to the aerosol properties than the radiance. Measurements of polarization at two wavelengths and with an angular scanning are simulated and an inversion algorithm is proposed. It aims at finding an “equivalent aerosol model,” which reproduces the optical thickness and the asymmetry factor of the actual aerosol at all wavelengths in the solar spectrum.     

后向散射辐射探测大气臭氧总量反演方法的改进

以SBDART模式作为辐射传输计算模式,在各种大气气溶胶存在的情况下利用现有的大气后向散射反演大气臭氧总量的Version7方法,模拟计算得到各种气溶胶存在时的大气臭氧总量,并分析了反演结果误差产生的原因.进一步提出根据斜气柱臭氧总量sΩ0,选择不同连续波长区间测量得到的后向散射强度来对臭氧总量的初估值Ω0进行修正的方法.将得到的结果与Version7的进行比较,证明了新方法的有效性.      

An improved,near real time water vapor path delay correction of Cryosat-2 sea surface height measurements

This paper presents improvements of a method (Stum et al., 2011) aimed at computing the water vapor path delay correction of altimeter sea surface height, using total precipitable water measurements from scanning microwave radiometers. The main interest of this improved method is for the Cryosat-2 mission over the ocean. Focus is made on the applicability of the method in near real time. An experiment to produce an operational path delay correction for Jason-2 and Cryosat-2 Interim Geophysical Data Records (IGDR) has been set up. Results confirm that the new correction, although less accurate than the one attainable with an embarked radiometer, improves the Cryosat-2 sea surface height accuracy.     

GNSS reflectometry and remote sensing: New objectives and results

The Global Navigation Satellite System (GNSS) has been a very powerful and important contributor to all scientific questions related to precise positioning on Earth’s surface, particularly as a mature technique in geodesy and geosciences. With the development of GNSS as a satellite microwave (L-band) technique, more and wider applications and new potentials are explored and utilized. The versatile and available GNSS signals can image the Earth’s surface environments as a new, highly precise, continuous, all-weather and near-real-time remote sensing tool. The refracted signals from GNSS radio occultation satellites together with ground GNSS observations can provide the high-resolution tropospheric water vapor, temperature and pressure, tropopause parameters and ionospheric total electron content (TEC) and electron density profile as well. The GNSS reflected signals from the ocean and land surface could determine the ocean height, wind speed and wind direction of ocean surface, soil moisture, ice and snow thickness. In this paper, GNSS remote sensing applications in the atmosphere, oceans, land and hydrology are presented as well as new objectives and results discussed.     

Influence of solar-geomagnetic disturbances on SABER measurements of 4.3 μm emission and the retrieval of kinetic temperature and carbon dioxide

Thermospheric infrared radiance at 4.3 μm is susceptible to the influence of solar-geomagnetic disturbances. Ionization processes followed by ion-neutral chemical reactions lead to vibrationally excited NO⁺ (i.e., NO⁺(v)) and subsequent 4.3 μm emission in the ionospheric E-region. Large enhancements of nighttime 4.3 μm emission were observed by the TIMED/SABER instrument during the April 2002 and October–November 2003 solar storms. Global measurements of infrared 4.3 μm emission provide an excellent proxy to observe the nighttime E-region response to auroral dosing and to conduct a detailed study of E-region ion-neutral chemistry and energy transfer mechanisms. Furthermore, we find that photoionization processes followed by ion-neutral reactions during quiescent, daytime conditions increase the NO⁺ concentration enough to introduce biases in the TIMED/SABER operational processing of kinetic temperature and CO₂ data, with the largest effect at summer solstice. In this paper, we discuss solar storm enhancements of 4.3 μm emission observed from SABER and assess the impact of NO⁺(v) 4.3 μm emission on quiescent, daytime retrievals of Tk/CO₂ from the SABER instrument.     

Interannual variability of the zonal sea surface slope in the equatorial Atlantic during the 1990s

Altimetry data have proven themselves essential for the early detection, analysis and monitoring of large scale tropical anomalies associated with El Niño in the Pacific. Warm events in the Atlantic are much weaker than in the Pacific and are partially masked by the strong seasonal cycle. Satellite altimetric data permits one to estimate the zonal sea surface slope variations at the equator in the Atlantic with sufficient accuracy for resolving interannual sea surface slope variations. The altimetry-derived slope is here shown to detect Atlantic warm events. For all warm events, anomalies in sea surface slope tend to lead SST. In the mid-1990s’, the equatorial interannual variability is dominated by 17-month period events which exhibit the structure observed in local coupled ocean–atmosphere warm events (zonal wind stress weakening and zonal surface slope relaxation, warm SST, excess precipitation). The frequency of occurrence of these Atlantic warm events is seen to have increased during the mid-1990s.