Diurnal variations in AVHRR SST fields: A strategy for removing warm layer effects from daily images

Different methodologies to estimate the amplitude of the sea surface temperature diurnal variation (DV) and remove it from remotely sensed SST images have been proposed in the last years. Among these, the parameterization proposed by [Stuart-Menteth et al., 2004a] and [Stuart-Menteth et al., 2004b] [Stuart-Menteth, A.C., Robinson, I.S., & Weller, R.A. (2004a). Sensitivity of the diurnal warm layer to meteorological fluctuations Part 1: observations, submitted to Journal of Atmospheric and Ocean Science; Stuart-Menteth, A.C., Robinson, I. S., & Donlon, C.J. (2004b). Sensitivity of the diurnal warm layer to meteorological fluctuations Part 2: a new parameterisation for diurnal warming, submitted to Journal of Atmospheric and Ocean Science] and adopted by the GHRSST-PP (Donlon, 2004) [Donlon, C.J., ad the GHRSST-PP Science Team, 2004: The GHRSST-PP data processing specification v1.0 (GDS v1.0, revision 1.5), GHRSST-PP Report N. 17, Published by the International GHRSST-PP Project Office, pp. 241] appeared as the most promising. In fact, it takes into account wind and insolation variations during the day, that effectively drive the SST diurnal cycle.This parameterization has been tested on 6 months of NOAA-16 AVHRR images acquired and processed at CNR with Pathfinder algorithm. The tests evidenced some limits for a correct estimation of the DV in low-wind regimes for any insolation condition, and in high insolation regimes (>600 W/m²) when the wind intensity increases or decreases of more than 2 m/s during the morning. The limits of applicability of the DV correction to NOAA-16 AVHRR data (at least for the Mediterranean area) were thus identified, and data outside these limits were flagged. However, some anomalous heating were not corrected even with these constraints, due to the lack of accuracy in the wind field used for the correction. As a result, a strategy to flag residual outliers in the corrected daily images has been developed, based on the comparison to an optimally interpolated night SST field of the previous day.     

Interannual variations in vegetation activities and climate variability caused by ENSO in tropical rainforests

Interannual variations in terrestrial carbon cycle over tropical rainforests affect the global carbon cycle. Terrestrial ecosystem models show the interannual relationship between climate changes due to El Niño‐Southern Oscillation (ENSO) and net primary production over tropical rainforests. However, we need an independent analysis using satellite‐based vegetation index and climate parameters. In the present study, we extracted the ENSO‐related interannual variations from time‐series in Normalized Difference Vegetation Index (NDVI) and climate data from 1981 to 2000, and analysed their relevance. We detected relationships among NDVI, ENSO, and climate parameters from long‐term data with negative NDVI–ENSO, NDVI–temperature, and positive NDVI–precipitation relations. These correlations suggest that interannual variability in vegetation activities over tropical rainforests could be extracted from NDVI time‐series despite noise components in NDVI data, and that interannual changes in precipitation and temperature caused by ENSO play a more important role in vegetation activities over tropical rainforests than in incoming surface solar radiation.     

The Vernam cipher is robust to small deviations from randomness

The Vernam cipher, or one-time pad, plays an important role in cryptography because it is perfectly secure. In this cipher a key is a sequence of equiprobable independently generated symbols. We show that under small disturbance of these properties the obtained cipher is close to the Vernam cipher in the case where the enciphered plaintext and the key are generated by stationary ergodic sources.

     

Recent approaches to global optimization problems through Particle Swarm Optimization

This paper presents an overview of our most recent results concerning the Particle Swarm Optimization (PSO) method. Techniques for the alleviation of local minima, and for detecting multiple minimizers are described. Moreover, results on the ability of the PSO in tackling Multiobjective, Minimax, Integer Programming and ¹ errors-in-variables problems, as well as problems in noisy and continuously changing environments, are reported. Finally, a Composite PSO, in which the heuristic parameters of PSO are controlled by a Differential Evolution algorithm during the optimization, is described, and results for many well-known and widely used test functions are given.     

Interannual variations of the grassland boundaries bordering the eastern edges of the Gobi Desert in central Asia

The Mongolian Steppe that borders the northern and eastern edges of the Gobi Desert in central Asia is one of the world's largest grasslands, extending across the nation of Mongolia and the Inner Mongolian Autonomous Region (IMAR) of China. Recent findings show that this region has one of the strongest warming signals on Earth since the late 1970s. The objective of this study was to evaluate the relationships between climate and interannual variation of the grassland boundaries in Mongolia and IMAR between 1982 and 1990. The remote sensing data used in this study were the 15–day maximum Normalized Difference Vegetation Index (NDVI) composites derived from the Global Area Coverage of the Advanced Very High Resolution Radiometer (AVHRR). Monthly precipitation, mean monthly temperature, and monthly actual evapotranspiration (AE) were derived from meteorological station records acquired during the study period across the eastern Mongolian Steppe. The occurrence of onset of green–up, as determined with time-series NDVI data, was used to identify vegetated and non-vegetated areas. Great interannual variation of the Gobi boundary position was observed over the study period. This boundary variation was largely controlled by the climate before the growing season (the ‘preseason’ climate). Along the eastern edge of the Gobi desert in central IMAR, preseason AE was the major climatic factor affecting the annual shift of the Gobi boundary, while further north in Mongolia, preseason temperature was the driving climatic factor. Our findings suggest that the response of vegetation communities to climate changes varied as a function of land-use intensity within the ecosystem.     

Interannual vegetation phenology estimates from global AVHRR measurements: Comparison with in situ data and applications

In a previous paper, we described a procedure to correct the directional effects in AVHRR reflectance time series. The corrected measurements show much less high frequency variability than their original counterparts, which makes them suitable to study vegetation dynamics. The time series are used here to estimate the start and ending dates of the growing season for 18 years from 1982 to 1999. We focus on the interannual variations of these phenological parameters.A database of in situ phenology observations is used to quantify the accuracy of the satellite-based estimates. Although based on a limited sampling of the Northern mid and high latitudes, the comparison indicates that i) the satellite phenological product contains meaningful information on interannual onset anomalies; ii) there is a higher degree of consistency over regions covered by Broadleaf Forests, Grasses and cereal Crops than over those covered by Needleleaf Forests or Savannas; and iii) the satellite phenological product is of lower quality in regions with mountainous terrain. In favorable conditions, interannual variations of the onset are captured with an accuracy of a few days.As this satellite-derived product captures the interannual onset variability at ground-truth sites, we confidently use it to larger scales studies. Mapped at a continental scale, the onset anomalies show coherent patterns at the regional (≈ 1000 km) scale for the mid and high latitudes of the Northern hemisphere, which is consistent with a meteorological forcing. In the tropics, there is larger spatial heterogeneity, which suggests more complex controls of the phenology. The relation between vegetation phenology and climate is further investigated over Europe by comparing the variability of the satellite-derived vegetation onset and that of the winter North Atlantic Oscillation index, at a fine spatial scale. The strong correlations observed confirm that this climate forcing parameter explains most of the onset variability over a large fraction of Northern Europe (earlier onsets for positive winter NAO), with lower impact towards the south and opposite effects around the Mediterranean basin. The NAO has a predictive character as the January-February NAO index is strongly correlated with the vegetation onset that occurs around April in Northern Europe.     

Building common ground in global teamwork through re-representation

We explore in this paper the relation between activities, communication channels and media, and common ground building in global teams. We define re-representation as a sequence of representations of the same concept using different communication channels and media. We identified the re-representation technique to build common ground that is used by team members during multimodal and multimedia communicative events in cross-disciplinary, geographically distributed settings. Our hypotheses are as follows: (1) Significant sources of information behind decisions and request for actions are embedded within the fabric of communicative events in which participants use both informal and formal media to express their ideas. Capturing these information sources can facilitate common ground building and accelerate the execution of action requests. (2) Re-representations of concepts, i.e., sequences of representations using diverse media and communication channels, mediate and accelerate common ground building. (3) The use of intra- or interdisciplinary re-representations correlates with high team performance, i.e., effective team process and high product quality. We used AEC Global Teamwork course offered in 2008–2009 as the testbed for our study to validate our hypothesis.     

Monitoring global and local variations in multichannel functional data for manufacturing processes

This study models global and local variations hidden in multichannel functional data (MFD) for the purpose of manufacturing process monitoring. With advances in sensing technology, online measurement of manufacturing process variables could take the shape of multichannel curves. Although MFD contains rich information about process conditions, it is a challenging issue to model and interpret complex variations in MFD for process change detection and process faulty condition discrimination. A new approach was developed in this paper to decompose each channel of functional data into global and local variation components. Based on the extracted patterns, a principal curve regression method was applied to detect and discriminate different process conditions. The method was validated by real data from a forging plant. A simulation study was also conducted to verify the approach for MFD with complex patterns.     

SST derivation from MSG for PUMA Pilot Projects in Fisheries

This study presents the technical and scientific results obtained through a collaboration between the Institute for Environment and Sustainability (Joint Research Centre of the European Commission) and two PUMA Pilot Projects, namely the Western Indian Ocean Satellite Application Project (WIOSAP), and the Monitoring of the Oceanographic and Meteorological Environment in support of the Management of Fisheries in Senegal (SEGEPS). Both projects are aimed at an optimized use of MSG (Meteosat Second Generation) satellite images to improve the management of regional fisheries and the current scientific knowledge on the natural variability of the fish stocks. A Sea Surface Temperature product from MSG is generated operationally at the native SEVIRI resolution (3 km at the sub‐satellite point) and can be used to locate upwelling regions and thermal fronts for the identification of Potential Fishing Zones (PFZs).     

The summer upwelling of the Eastern Aegean Sea detected from MODIS SST scenes from 2003 to 2015

The summer upwelling of the Eastern Aegean Sea is investigated by daily night-time MODerate resolution Imaging Spectroradiometer Sea Surface Temperature scenes in the periods from June to November (extended summer) 2003–2015. The analysis is supported by wind data downloaded from the European Centre for Medium-Range Weather Forecasts Re-Analysis archive. On average over these summers, upwelling and Etesian wind occurred 69% and 78% of time, respectively. The highest correlation between upwelling and wind was found from June to September, with the beginning of the upwelling events shifted between 24 and 48 h after the start of the Etesian wind. The upwelling always begins in the same areas of the Eastern Aegean coast with the only differences that these areas tesian wind pattern. The largest upwelling events occurred in summers 2003–2009 and not in the following years of the study period. The upwelled cold surface water, still pushed by the persistent Etesian wind, fills part of South-Eastern Aegean and eventually outflows the Aegean Sea through Kassos and Karpathos Straits of the eastern Cretan Arc.     

调频Guassian小波在从NOWCAST图获取SST中的应用

温跃层对于潜艇的水下航行和战斗具有十分重要的意义。由于中国的现状,无法获取大量高精度的SST资料,给研究带来了很大的障碍。该文针对数据获取比较困难和数据精度不高的现状,提出了将图形的颜色表示从RGB空间转换到HIS空间来构造一时间序列,并对此序列用调频Guassian小波来进行分解和重构,其所得的低频信号能很好地还原出颜色变量中所包含地温度信息。经实验证明,该方法比传统的处理方法有了十分明显的提高,所得到的温度数据精度高,能满足温跃层研究的需要。     

Robust estimation of parameters: A simple modification to all non-linear fitting algorithms to convert from minimizing the sum of squares of deviations to minimizing the sum of the absolute deviations

A simple modification has been derived to convert non-linear fitting procedures from minimizing the sum of squares to minimizing the sum of absolute deviations. The modification has been made to the Levenberg-Marquardt non-linear fitting procedure. A number of cases from the literature have been used to demonstrate the method. Minimization of the sum of absolute deviations is shown to be a much safer procedure than least squares since it is inherently resistant to being thrown off by outliers among the data points. Criteria are given for the choice of the robust least absolute deviation minimization scheme over least squares.     

Evolutions of households with every member out-of-home across Japanese cities from 1987 to 2015

Despite the nobody-at-home situation having induced several problems, including home burglaries and home-delivery failure, this situation is not comprehensively understood yet. A recent study has examined and developed temporal profiles of households with the situation of every member out-of-home (HEMO) or nobody-at-home, using household travel surveys. However, the variation of HEMO across different cities over several years remains unclear. This study performs a comparative analysis of the HEMO and individual out-of-home (IO) rates across Japanese cities over several years by using the Nationwide Person Trip Survey data. The result obtained by a single-year (2015) data revealed that the HEMO and IO rates were higher in cities than in towns and villages. The municipalities were then classified according to the temporal HEMO profiles. The results obtained by multi-year (1987, 1992, 2005, and 2015) data revealed that the variation of the HEMO rate was marginal in comparison to the reduction in the IO rate during 1987–2015. The minimal variation of HEMO was attributed to the opposing effects of the changes in the household size distribution and the changes in the HEMO rate for households of each size. The temporal profiles of the HEMO rates, obtained by the multi-year data, were also classified. Their transition patterns were demonstrated and analyzed. Household travel survey data can thus be used to plot temporal profiles, which can be useful for analyzing and understanding cities.     

Minimizing deviations of input and output weights from their means in data envelopment analysis

In this paper, we propose a model that minimizes deviations of input and output weights from their means for efficient decision-making units in data envelopment analysis. The mean of an input or output weight is defined as the average of the maximum and the minimum attainable values of the weight when the efficient decision making unit under evaluation remains efficient. Alternate optimal weights usually exist in the linear programming solutions of efficient decision-making units and the optimal weights obtained from most of the linear programming software are somewhat arbitrary. Our proposed model can yield more rational weights without a priori information about the weights. Input and output weights can be used to compute cross-efficiencies of decision-making units in peer evaluations or group decision-making units, which have similar production processes via cluster analysis. If decision makers want to avoid using weights with extreme or zero values to access performance of decision-making units, then choosing weights that are close to their means, may be a rational choice.     

Australian water mass variations from GRACE data linked to Indo-Pacific climate variability

Time-variable gravity data from the Gravity Recovery And Climate Experiment (GRACE) mission are used to study total water content over Australia for the period 2002-2010. A time-varying annual signal explains 61% of the variance of the data, in good agreement with two independent estimates of the same quantity from hydrological models. Water mass content variations across Australia are linked to Pacific and Indian Ocean variability, associated with El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), respectively. From 1989, positive (negative) IOD phases were related to anomalously low (high) precipitation in southeastern Australia, associated with a reduced (enhanced) tropical moisture flux. In particular, the sustained water mass content reduction over central and southern regions of Australia during the period 2006-2008 is associated with three consecutive positive IOD events.     

通过Foxmail接收Hotmail邮件

4月9日,博大公司推出了最新的Foxmail4.1。使用该版本的Foxmail,你可以很方便地接收到Hotmail邮箱中的邮件,从而弥补以前你无法使用电子邮件软件接收Hotmail邮件的遗憾。在此,笔者就如何在Foxmail接收Hotmail邮件略述于下,希望对你能够有所帮助。     

Interannual variability of smoke and warm cloud relationships in the Amazon as inferred from MODIS retrievals

Aerosol and cloud data from the MODerate resolution Imaging Spectroradiometer (MODIS) onboard the Earth Observing System (EOS) Aqua are used to investigate interannual variability of smoke and warm cloud relationships during the dry-to-wet transition season (August-October) over the Amazon for two years and its association with meteorological conditions. In one year (2003), smoke aerosols are associated with an increase of cloud fraction and a decrease of cloud effective radius. These effects amplify the cooling at the surface and at the top of the atmosphere (TOA) caused by the aerosol extinction. However, in another year (2002) the cloud fraction decreases with increasing aerosol optical depth. Such a decrease of cloud fraction could offset the effect of increased reflection of solar radiation by the aerosols both at the surface and at TOA. The changes in radiative fluxes between these years would contribute to interannual changes of surface energy fluxes and radiative balance at the top of the atmosphere and influence variability of the wet season onset in the basin. In 2003, the atmosphere was more humid and less stable. These conditions may be relatively favorable for the activation of aerosol particles into cloud condensation nuclei and hence cloud droplets. In 2002, the clouds were less extensive and thinner in a relatively dry atmosphere and presumably dissipated more easily. This study suggests that the aerosol-cloud relation can be influenced by atmospheric structure and convective motions, in addition to changes in aerosols properties. An adequate characterization of aerosol-cloud relationship would require a longer time series of data that includes a variety of climate conditions. The caveat of this analysis is that differences in aerosol absorption and its vertical distribution may have contributed to the observed interannual change of smoke-cloud relationship but could not be determined due to lack of adequate measurements.     

Modelling temporal variations in microwave backscattering from reed marshes

A full understanding of radar backscattering characteristics and their seasonal variations is one of the important ways to analyse the growth conditions in wetlands. This research simulated seasonal C-band and L-band synthetic aperture radar (SAR) backscattering from reed marshes using a refined version of the electromagnetic (REM) model, which was first validated by time series of multimode SAR observations at the experimental site used. Then, two factors including sensor parameters and vegetation structure, which influence the temporal evolution of the radar response from reed marshes, were assessed. The results demonstrate that the radar response is closely related to growth processes in the reed marsh. At the early growth stage when reed marshes are sparse, the double-bounce mechanism was dominant at all the incidence angles of C-band radar, but for L-band radar, strong specular reflection was produced from the smooth water if the incidence angle is lower than 25°. It was also found that the sensitivity to the density and height of reed marshes is greater for L-band radar than at the C-band, indicating that L-band backscattering may be useful for reed marsh biomass retrieval.