Csaba Ferencz

Yield estimation for corn and wheat in the Hungarian great plain using Landsat MSS data

Abstract Models for the forecasting of crop yields using remotely-sensed satellite data are studied intensively worldwide. After reviewing the experience gained by other researchers in this field, we selected procedures which might be suitable for the estimation of corn and wheat yields in Hungary. In order to study the relations between various remotely-sensed spectral data (and their combinations) and the actually measured final yields we investigated archived agricultural and Landsat MSS spectral data for 1984. A linear relation has been sought and found between the yield data for 47 corn and 55 wheat fields in Hajdu-Bihar county and various weighted and summed spectral quantities. Among the vegetation indices derived from satellite data and corrected for atmospheric effects the most promising were the spectral indices sensitive to the green biomass. The latter, summed over a certain period in the growing season, exhibited a regression of 45-86 per cent, depending on the crop and the period of summatio...

Whistler doublets and hyperfine structure recorded digitally by the signal analyzer and sampler on the active satellite

The signal analyzer and sampler (SAS) experiment was placed on the Active spacecraft as a collaborative effort between the Eotvos University (Budapest), the Technical University of Budapest, and IZMIRAN (Moscow). The scientific objective of the experiment was to study whistler/VLF ducted propagation, VLF duct structure, and the hyperfine structure of whistlers. Digitally sampled waveforms of several field components were transmitted in real time by the SAS telemetry system at 460.4 MHz. For the transmission 900-Hz wide bands were selected between 0.5 and 21.5 kHz or a single 5 kHz wide band was transmitted. Data were received in Budapest, Hungary and at Wallops Island, Virginia. Although the obtained data were processed for various purposes, here some results concerning the hyperfine structure of whistlers are presented. The studied whistlers, recorded as several pairs of closely spaced traces (doublets), were interpreted as ducted whistlers escaping at a high altitude from a single or two closely spaced narrow ducts and reaching the satellite directly from above or after reflection from below. The whistler traces were processed by a sophisticated matched filter technique which enabled us to obtain very high resolution dynamic (frequency-time-amplitude) spectra. The hyperfine structure of traces revealed by this technique demonstrates the complexity of whistler propagation. The observed splitting of traces may be explained, for example, in terms of a number of guided modes (waveguide mode splitting) or by the superposition of closely spaced ducting structures (duct splitting).

Surface models including direct cross-radiation: a simple model of furrowed surfaces.

Abstract In the interpretation of measured reflectance data it is important to consider those surface radiation effects which make a significant contribution to the overall irradiation pattern. A model was constructed for furrowed bare soil surfaces which includes the direct cross-radiation effect between the surface elements. According to the model computations performed the direct cross-radiation plays a significant role in the measured, reflected signal intensity. The computational method developed is suitable for including the direct cross-radiation effect in surface radiation models in the optical region.

The Study of Electromagnetic Parameters of Space Weather, Micro-Satellite “Chibis-M”

Plasma-wave experiment on the micro-satellite “Chibis-M” is aimed at the solution of fundamental problem – a study of the interrelation of the plasma- wave processes connected with the manifestation in the ionosphere of solar – magnetosphere – ionosphere – atmosphere connections and the parameters of space weather. Specific fundamental problem is the search for universal laws governing transformation and dissipation of plasma-wave energy in the magnetosphere-ionosphere system. The solution of this problem will be achieved employing the coordinated Procedure: (1) Study in situ of the fluctuations of electrical and magnetic field, the parameters of thermal and epithermal plasma in the ionosphere near layer F during different helio- and geomagnetic conditions. (2) Study of the geomagnetic and geophysical parameters on the ground-based observatories with the time scales from 10–1 to 10–3 s. (3) Study of the interrelation of electromagnetic phenomena (spectra of ULF/VLF- waves) in different regions of near-earth space by means of via the comparative analysis of the wave measurements of those carry out simultaneously on different spacecrafts and ground geophysical stations. Micro-satellite “Chibis-M” now designed in IKI. Total mass of “Chibis-M” with support systems construction and scientific instruments is 40 kg.

Yield estimation and forecasting for winter wheat in Hungary using time series of MODIS data

ABSTRACT Wheat is one of the most important crops in Hungary, which represents approximately 20% of the entire agricultural area of the country, and about 40% of cereals. A robust yield method has been improved for estimating and forecasting wheat yield in Hungary in the period of 2003–2015 using normalized difference vegetation index (NDVI) derived from the data of the Moderate Resolution Imaging Spectroradiometer. Estimation was made at the end of June – it is generally the beginning of harvest of winter wheat in Hungary – while the forecasts were performed 1–7 weeks earlier. General yield unified robust reference index (GYURRI) vegetation index was calculated each year using different curve-fitting methods to the NDVI time series. The correlation between GYURRI and country level yield data gave correlation coefficient (r) of 0.985 for the examined 13 years in the case of estimation. Simulating a quasi-operative yield estimation process, 10 years’ (2006–2015) yield data was estimated. The differences between the estimated and actual yield data provided by the Hungarian Central Statistical Office were less than 5%, the average difference was 2.5%. In the case of forecasting, these average differences calculated approximately 2 and 4 weeks before the beginning of harvest season were 4.5% and 6.8%, respectively. We also tested the yield estimation procedure for smaller areas, for the 19 counties (Nomenclature of Territorial Units for Statistics-3 level) of Hungary. We found that, the relationship between GYURRI and the county level yield data had r of 0.894 for the years 2003–2014, and by simulating the quasi-operative forecast for 2015, the resulting 19 county average yield values differed from the actual yield as much as 8.7% in average.

Automatic retrieval of plasmaspheric electron densities: First results form Automatic Whistler Detector and Analyzer Network

There is an increasing ‘demand’ for plasmaspheric electron density data for plasmasphere models in Space Weather related investigations, particularly in modeling charged particle accelerations and losses in Radiation Belts. The global Automatic Whistler Detector and Analyzer (AWDA) system network detects millions of whistlers in a year. But the analysis of the whistlers to extract the plasmaspheric electron density information has thus far proved to be slow and time consuming. A recently developed whistler inversion model opened the way for an automated process of whistler analysis, not only for single whistler events but for complex analysis of multiple-path propagation whistler groups. An automatic analyzer algorithm was also developed and a practical implementation of such a system on a PC cluster is done. The prototype of AWDA runs on the cluster in quasi-realtime mode, the analysis of a whistler group take a few minutes. In this paper we present the first results of test runs processing whistlers from our archive database. We are planning to install this algorithm on AWDANet nodes in the near future to archive the quasi-realtime mode of operation in providing plasmaspheric electron densities.

Ducted and free-space UWB propagation of transient signals in space environment

In this paper a new solving method is presented, using the method of inhomogeneous basic modes (MIBM), that avoids all the former monochromatic ways of thinking in the description of UWB signals, in order to obtain the complete solution of Maxwells equations for real impulses. The paper presents new and general solutions for ducted electromagnetic waves in wave-guides filled by vacuum or anisotropic plasma. The theoretical results are presented in comparison with the data-base measured by DEMETER satellite.

Methods of Signal Analysis

The method using whistlers (impulse-generated signals) is one of the small number of techniques which yield reliable data on morphology and dynamics of the medium traversed by the signal, e.g. of plasmasphere, on magnetospheric electric fields and of ionosphere-magnetosphere coupling fluxes of the Earth and other planets. On the other hand studying the signal waveform, their amplitude-frequency behaviour the better understanding of the wave propagating in the upper atmospheric plasma can be achieved.

Application of the Method for Different Propagation Situations

The method presented in Chapter 1 can be used not only in cases in which the media in space-segments are homogeneous between the boundary surfaces — see Fig. 1.1 —, but also in cases in which the media in these space-segments are weakly inhomogeneous (quasi-homogeneous) or inhomogeneous (e.g. Ferencz, 1995b) and the gradient of the inhomogeneous medium parameters is limited only by the validity-condition of the method (Ferencz, 1978a). In the following let us generalise the method of solution — presented in point 1.1 and applied in point 1.3 — for the cases in which the media in the space-segments are quasi-homogeneous and inhomogeneous between the boundary surfaces.

Measuring of General Shape Electromagnetic Signals of Natural Environment

In this chapter we will consider ELF-VLF waves because of the following reasons: The speed of the generally available electronic components, namely the commercially available analogue-to-digital converters, the computation speed of the computers and in space experiments the effective capacity of the typical telemetry-systems prevents us from dealing with high resolution detailed time-domain analyses of higher frequency e.m. waves in the routine monitoring of electromagnetic environment. In the Earth’s upper atmosphere the propagation factor of these low frequency waves makes the analyses possible. All the results obtained from the analyses of ELF-VLF waves are valid to other higher frequency signals propagating in similar media (see point 2.4.3).