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1.
INSAT-3D is the new generation Indian satellite designed for improved Earth observations through two payloads – Imager and Sounder. Study was conducted with an aim of simulating satellite level signal over land in the infrared channels of the Imager payload
using a radiative transfer model MODTRAN. Satellite level at-sensor radiance corresponding to all four infrared channels of
INSAT-3D Imager payload is obtained using MODTRAN and sensitivity of at-sensor radiance was inferred as a function of input
parameters namely, surface temperature, emissivity, view angle and atmospheric water vapour, which is helpful in understanding
the signal simulation scheme needed for retrieving a very critical parameter namely, land surface temperature. 相似文献
2.
Starting with an outline of spectral radiance calculation for infrared bands, a simulation study has been presented for 11.1, 8.3, 7.3 and 6.7 μm. Detailed response of the spectral radiance to the meteorological parameters has been studied by generating simulated atmospheric temperature and moisture profiles for Indian atmospheres. It has been found that the responses of the 8.3, 7.3 and 6.7 μm bands are maximum for lower troposphere, middle troposphere and upper troposphere respectively, and these spectral radiances are linearly related to the water vapour content of the relevant layers. The thermal IR window at 11.1 μm is found to be sensitive to not only surface temperature and total water vapour content but also to the boundary layer values of mean temperature and water vapour content.
相似文献3.
4.
A direct linear relationship between water vapour content of lower, middle and upper-middle troposphere respectively with the radiances for 8.3, 7.3 and 6.7 μm spectral observations has been attempted. From the atmospheric simulations such a relationship is found to exist with a good degree of correlation and is seen to be quite insensitive to temperature changes. Such an approach is used to interpret the water vapour imageries obtained from TIROS-N sounder through construction of detailed water vapour distribution maps. 相似文献
5.
NAVEEN R SHAHI NEERAJ AGARWAL ALOKE K MATHUR ABHIJIT SARKAR 《Journal of Earth System Science》2011,120(3):337-345
An atmospheric correction method has been applied on sea surface temperature (SST) retrieval algorithm using Very High Resolution
Radiometer (VHRR) single window channel radiance data onboard Kalpana satellite (K-SAT). The technique makes use of concurrent
water vapour fields available from Microwave Imager onboard Tropical Rainfall Measuring Mission (TRMM/TMI) satellite. Total
water vapour content and satellite zenith angle dependent SST retrieval algorithm has been developed using Radiative Transfer
Model [MODTRAN ver3.0] simulations for Kalpana 10.5–12.5 μm thermal window channel. Retrieval of Kalpana SST (K-SST) has been
carried out for every half-hourly acquisition of Kalpana data for the year 2008 to cover whole annual cycle of SST over Indian
Ocean (IO). Validation of the retrieved corrected SST has been carried out using near-simultaneous observations of ship and
buoys datasets covering Arabian Sea, Bay of Bengal and IO regions. A significant improvement in Root Mean Square Deviation
(RMSD) of K-SST with respect to buoy (1.50–1.02 K) and to ship datasets (1.41–1.19 K) is seen with the use of near real-time
water vapour fields of TMI. Furthermore, comparison of the retrieved SST has also been carried out using near simultaneous
observations of TRMM/TMI SST over IO regions. The analysis shows that K-SST has overall cold bias of 1.17 K and an RMSD of
1.09 K after bias correction. 相似文献
6.
The tropopause height and tropopause temperature are sensitive to temperature changes in troposphere and stratosphere. These
are the measures of global climatic variability. Atmospheric profiles of temperature, refractivity and water vapour are always
needed for communication, navigation and atmospheric modeling studies. The tropopause characteristics over the Indian region
have been studied using radio occultation measurements (CHAMP) on the basis of cold point criterion. Tropopause height shows
large variation in the latitude range ∼30°–40°N during winter. Tropopause temperature less than −82°C, assumed to facilitate
troposphere to stratosphere air transport, is observed at a number of tropical Indian locations and no seasonal pattern is
observed in its occurrence. The bias in temperature and refractivity deduced from radiosonde and radio occultation measurements
is also presented. 相似文献
7.
S. Fadnavis S. Dhomse S. Ghude U. Iyer P. Buchunde S. Sonbawne P. E. Raj 《International Journal of Environmental Science and Technology》2014,11(2):529-542
Ozone trends in the Upper Troposphere and Lower Stratosphere over the Indian region are investigated using three satellite data sets namely Halogen Occultation Experiment (1993–2005), Stratospheric Aerosol and Gas Experiment (1993–2005) II, and Aura Microwave Limb Sounder (MLS, 2005–2011). Estimated ozone trends using multi-variate regression analysis are compared with trends at two Indian ozonesonde stations (Delhi, 28°N, 77°E and Pune, 18°N, 73°E), and a 3-D Chemical Transport Model (CTM, SLIMCAT) for the 1993–2005 time period. Overall, all the observational data sets and model simulations indicate significant increasing trend in the upper troposphere (0–2.5 %/year). In the lower stratosphere, estimated trends are slightly positive up to 30 mb and are negative between 30 and 10 mb. Increasing trends in the upper troposphere is probably due to increasing trends in the tropospheric ozone precursor gases (e.g. CO, NO x , NMHCs). Here, we argue that these contrasting ozone-trend profiles might be partially responsible for insignificant long-term trends in the tropical total column ozone. On seasonal scale, positive trends are observed during all the seasons in the upper troposphere while structure of trend profile varies in lower stratosphere. Seasonal variations of ozone trends and its linkages with stratospheric intrusions and increasing trends in lightning flashes in the troposphere are also discussed. 相似文献
8.
AIRS红外高光谱资料反演大气水汽廓线研究进展 总被引：1，自引：0，他引：1
随着卫星遥感关键技术的突破,卫星光谱分辨率达到了分辨大气成分单个谱线的水平,研究人员开始了大量通道同时反演大气廓线和多种微量成分的研究.针对AIRS(Atmospheric Infrared Sounder)就红外高光谱资料反演大气水汽廓线的研究进展进行了评述,从训练数据、通道信息的提取及降维、反演算法和反演精度改进4个方面对反演晴空大气水汽廓线的研究现状进行了分析与讨论.AIRS资料反演大气水汽廓线的训练数据通常选用威斯康星大学提供的全球晴空反演训练样本集CIMSS (Cooperative Institute for Meteorological Satellite Studies,University of WisconsinMadison)和SARTA(Stand-Alone Radiative Transfer Algorithm)辐射传输模式模拟的亮温辐射值.归纳总结了2种通道信息的提取及降维方法:一是采用有效的方法来完成光谱信息压缩,对常用的主成分分析和独立分量分析方法进行了对比,认为独立分量分析更为可行.二是通道选择,即保留部分含有较多大气廓线信息量的通道,达到降维目的.在进行通道选择时要注意针对不同地区气候类型、下垫面、季节以及即时天气条件,选择不同的通道组合.介绍了3种反演算法:特征向量统计法、牛顿非线性迭代法和神经网络法.对比发现特征向量统计法简单易行,但精度不够理想;牛顿非线性迭代法精度虽高但计算耗时长,因此不适合业务使用;神经网络计算速度快、精度也能达到要求,具有很好的前景.对目前的几种样本分类方法及附加因子进行了对比分析,对反演算法精度的改进提出了一些有益的设想.最后对晴空辐射订正及云天大气水汽廓线反演进行了简要介绍,提出了该领域未来的一些研究方向. 相似文献
9.
Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible
spectrometer over the tropical station Pune (18‡31′, 73‡51′) for the years 2000–2003. These observations are obtained in the
spectral range 462–498 nm for the solar zenith angles (SZAs) varying from 87‡ to 91.5‡. An algorithm has been developed to
retrieve vertical profiles of ozone (O3) and nitrogen dioxide (NO2) from ground-based measurements using the Chahine iteration method. This retrieval method has been checked using measured
and recalculated slant column densities (SCDs) and they are found to be well matching. O3 and NO2 vertical profiles have been retrieved using a set of their air mass factors (AMFs) and SCDs measured over a range of 87–91.5‡
SZA during the morning. The vertical profiles obtained by this method are compared with Umkehr profiles and ozonesondes and
they are found to be in good agreement. The bulk of the column density is found near layer 20–25 km. Daily total column densities
(TCDs) of O3 and NO2 along with their stratospheric and tropospheric counterparts are derived using their vertical profiles for the period 2000–2003.
The total column, stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer
and minimum in the winter season. Increasing trend is found in column density of NO2 in stratospheric, tropospheric and surface layers, but no trend is observed in O3 columns for above layers during the period 2000–2003 相似文献
10.
In this study, retrieval of temperature and humidity profiles of atmosphere from INSAT 3D-observed radiances has been accomplished. As the first step, a fast forward radiative transfer model using an Artificial neural network has been developed and it was proven to be highly effective, giving a correlation coefficient of 0.97. In order to develop this, a diverse set of physics-based clear sky profiles of pressure (P), temperature (T) and specific humidity (q) has been developed. The developed database was further used for geophysical retrieval experiments in two different frameworks, namely, an ANN and Bayesian estimation. The neural network retrievals were performed for three different cases, viz., temperature only retrieval, humidity only retrieval and combined retrieval. The temperature/humidity only ANN retrievals were found superior to combined retrieval using an ANN. Furthermore, Bayesian estimation showed superior results when compared with the combined ANN retrievals. 相似文献
11.
Impact of satellite soundings on the simulation of heavy rainfall associated with tropical depressions 总被引：1，自引：1，他引：0
The present study is carried out to examine the impact of temperature and humidity profiles from moderate resolution imaging
spectroradiometer (MODIS) or/and atmospheric infrared sounder (AIRS) on the numerical simulation of heavy rainfall events
over the India. The Pennsylvania State University–National Centre for Atmospheric Research fifth-generation mesoscale model
(MM5) and its three-dimensional variational (3D-Var) assimilation technique is used for the numerical simulations. The heavy
rainfall events occurred during October 26–29, 2005, and October 27–30, 2006, were chosen for the numerical simulations. The
results showed that there were large differences observed in the initial meteorological fields from control experiment (CNT;
without satellite data) and assimilation experiments (MODIS (assimilating MODIS data), AIRS; (assimilating AIRS data); BOTH
(assimilating MODIS and AIRS data together)). The assimilation of satellite data (MODIS, AIRS, and BOTH) improved the predicted
thermal and moisture structure of the atmosphere when compared to CNT. Among the experiments, the predicted track of tropical
depressions from MODIS was closer to the observed track. Assimilation of MODIS data also showed positive impact on the spatial
distribution and intensity of predicted rainfall associated with the depressions. The statistical skill scores obtained for
different experiments showed that assimilation of satellite data (MODIS, AIRS, and BOTH) improved the rainfall prediction
skill when compared to CNT. Root mean square error in quantitative rainfall prediction is less in the experiment which assimilated
MODIS data when compared to other experiments. 相似文献
12.
Recent research has shown evidence of strong coupling between the atmosphere and lithosphere in coastal regions, associating abnormal atmospheric phenomena to the occurrence of strong earthquakes. Surface latent heat flux (SLHF), total column water vapor (CWV), relative humidity (RH) and total ozone column (TOC), analyzed over the epicentral region of the Denali fault earthquake of November 3, 2002, exhibit anomalous behavior that could be related to the earthquake preparatory process and its occurrence. The complementary nature of the parameters provides strong support that the anomalous values were driven by lithospheric processes, rather than other atmospheric phenomena. Due to the wide availability of remote sensing observations of atmospheric parameters, the detection of anomalies can be used to mitigate the earthquake risks. 相似文献
13.
This paper reports the radiative transfer simulations for the passive microwave radiometer onboard the proposed Indian climate
research satellite Megha-Tropiques due to be launched in 2011. These simulations have been performed by employing an in-house
polarized radiative transfer code for raining systems ranging from depression and tropical cyclones to the Indian monsoon.
For the sake of validation and completeness, simulations have also been done for the Tropical Rainfall Measuring Mission (TRMM)’s
Microwave Imager (TMI) of the highly successful TRMM mission of NASA and JAXA. The paper is essentially divided into two parts:
(a) Radiometer response with specific focus on high frequency channels in both the radiometers is discussed in detail with
a parametric study of the effect of four hydrometeors (cloud liquid water, cloud ice, precipitating water and precipitating
ice) on the brightness temperatures. The results are compared with TMI measurements wherever possible. (b) Development of
a neural network-based fast radiative transfer model is elucidated here. The goal is to speed up the computational time involved
in the simulation of brightness temperatures, necessitated by the need for quick and online retrieval strategies. The neural
network model uses hydrometeor profiles as inputs and simulates spectral microwave brightness temperature at multiple frequencies
as output. A huge database is generated by executing the in-house radiative transfer code for seven different cyclones occurred
in North Indian Ocean region during the period 2001–2006. A part of the dataset is used to train the network while the remainder
is used for testing purposes. For the purpose of testing, a typical scene from the southwest monsoon rain is also considered.
The results obtained are very encouraging and show that the neural network is able to mimic the underlying physics of the
radiative transfer simulations with a correlation coefficient of over 99%. 相似文献
14.
《Comptes Rendus Geoscience》2018,350(7):354-367
In the 1980s, ground-based monitoring of the ozone layer played a key role in the discovery of the Antarctic Ozone Hole as well as in the first documentation of significant winter and spring long-term downward trends in the populated mid-latitude regions. The article summarizes the close-to-hundred-year-long history of ground-based measurements of stratospheric ozone, and more recent observations of constituents that influence its equilibrium. Ozone observations began long before the recognition of the impact of increasing emissions of manmade ozone-depleting substances on ozone and therefore on UV levels, human health, ecosystems and the Earth climate. The historical ozone observations prior to 1980s are used as a reference for the assessments of the state of the ozone layer linked to the enforcement of the Montreal Protocol. In this paper, we describe the worldwide monitoring networks and their ozone observations used to determine long-term trends with an accuracy of a few percent per decade. Since 1989, the ground-based monitoring activities have provided support for the amendments of the Montreal Protocol (MP). They include monitoring of (a) the ozone total column and the vertical distribution at global scale, (b) the ozone-depleting substances (ODS) related to the MP such as chlorofluorocarbons (CFCs), and their decomposition products in the stratosphere, and (c) the atmospheric species playing a role in ozone depletion, e.g., nitrogen oxides, water vapor, aerosols, polar stratospheric clouds. We highlight important accomplishments in the atmospheric monitoring performed by the Global Atmosphere Watch program (GAW) run under the auspices of the World Meteorological Organization (WMO) and by the Network for the Detection of Atmospheric Composition Change (NDACC). We also address the complementary roles of ground-based networks and satellite instruments. High-quality ground-based measurements have been used to evaluate ozone variabilities and long-term trends, assess chemistry climate models, and check the long-term stability of satellite data, including more recently the merged satellite time-series developed for the detection of ozone recovery at global scale, which might be further modified by climate change. 相似文献
15.
P. N. Mahajan 《Journal of Earth System Science》2001,110(3):225-229
Recent algorithms for Special Sensor Microwave/Imager (DMSP-SSM/I) satellite data are used for estimating integrated water
vapour over the Indian seas. Integrated water vapour obtained from these algorithms is compared with that derived from radiosonde
observations at Minicoy and Port Blair islands. Algorithm-3 of Schlussel and Emery (1990) performed best. On the basis of
this algorithm, distribution of integrated water vapour is determined during the monsoon depression (22nd–27th July, 1992)
that formed over the Bay of Bengal. 相似文献
16.
A new stability index based on atmospheric refractivity at ~500 hPa level and surface measurements of temperature, pressure
and humidity is formulated. The new index named here as refractivity based lifted index (RLI) is designed to give similar
results as traditionally used lifted index derived from radiosonde profiles of temperature, pressure and humidity. The formulation
of the stability index and its comparison with the traditional temperature profile based lifted index (LI) is discussed. The
index is tested on COSMIC radio occultation derived refractivity profiles over Indian region. The forecast potential of the
new index for rainfall on 2°×2° latitude–longitude spatial scale with lead time of 3–24 hours indicate that the refractivity
based lifted index works better than the traditional temperature based lifted index for the Indian monsoon region. Decreasing
values of RLI tend to give increasing rainfall probabilities. 相似文献
17.
The aim of this paper is to study the feasibility of deriving vertical wind profiles from current satellite observations.
With this aim, we carried out complex empirical orthogonal function (CEOF) analysis of a large number of radiosonde observations
of wind profiles over the Indian Ocean during the monsoon months. It has been found that the first two CEOFs explain 67% of
the total variance in wind fields. While the first principal component is well correlated with the winds at 850 mb (r = 0:80), the second one is highly correlated with winds at 200 mb (r = 0:89). This analysis formed the basis of a retrieval
algorithm which ensures the retrieval of vertical profiles of winds using satellite tracked cloud motion vector winds. Under
the assumption that accurate measurements of wind are available at the above mentioned levels, the r.m.s. error of retrieval
of each component of wind is estimated to range between 2 ms-1 and 6 ms-1 at different levels, which is much less than the natural variance of winds at these levels. For a better visualization of
retrieval, we have provided retrieved and true wind profiles side by side for four typical synoptic conditions during the
monsoon season. 相似文献
18.
Sethu Raman Devdutta S. Niyogi A. Prabhu S. Ameenullah S. T. Nagaraj Udai Kumar S. Jayanna 《Journal of Earth System Science》1998,107(1):97-105
Surface features such as soil moisture and vegetation have a profound impact on the surface energy balance and the atmospheric
boundary layer. To quantify this effect for a tropical location, a detailed field experiment, VEBEX, was designed and successfully
executed in a tropical site at Bangalore, India. VEBEX was a joint experiment between the North Carolina State University,
Indian Institute of Science (IISc), and the University of Agricultural Science (UAS) at Bangalore, India. Continuous surface
meteorological measurements were taken over an entire crop period (pre-sowing to post-harvest). During different stages of
the plant growth, intensive observations of surface turbulence, and measurements of physiological and soil moisture measurements
were also conducted. The results obtained provide an insight into the unusually strong variability for the tropics. Interpretation
of the observations and an overview of the analysis procedure and future research initiatives are also presented. 相似文献
19.
Sophie Godin-Beekmann 《Comptes Rendus Geoscience》2010,342(4-5):339-348
This article provides an overview of the various satellite instruments, which have been used to observe stratospheric ozone and other chemical compounds playing a key role in stratospheric chemistry. It describes the various instruments that have been launched since the late 1970s for the measurement of total ozone column and ozone vertical profile, as well as the major satellite missions designed for the study of stratospheric chemistry. Since the discovery of the ozone hole in the early 1980s, spatial ozone measurements have been widely used to evaluate and quantify the spatial extension of polar ozone depletion and global ozone decreasing trends as a function of latitude and height. Validation and evaluation of satellite ozone data have been the subject of intense scientific activity, which was reported in the various ozone assessments of the state of the ozone layer published after the signature of the Montreal protocol. Major results, based on satellite observations for the study of ozone depletion at the global scale and chemical polar ozone loss, are provided. The use of satellite observations for the validation of chemistry climate models that simulate the recovery of the ozone layer and in data assimilation is also described. 相似文献
20.
This article reviews the current state-of-the-art and future prospects of the microwave techniques for remote sensing of the
earth’s atmosphere and ocean. Geophysical parameters and their relationship with measured thermal microwave radiation is established
through radiative transfer processes. The atmospheric temperature profile obtained from microwave sounding unit (msu) onboardtiros-N series of satellites is operational and is used for numerical weather prediction. The demonstrated applications of scanning
multichannel microwave radiometer (smmr) onboard most recent and advancedseasat satellite are highlighted.The capability ofseasat active sensors for monitoring ocean parameters have also been indicated. Feasible applications of microwave techniquese.g. moisture profile with advanced moisture sounder (amsu), and surface pressure from multifrequency active microwave pressure sounder (mps) are also described. Finally the recent and advanced microwave limb sounding (mls) technique and its applications to upper atmospheric research has been reviewed. 相似文献