Péter Steinbach

Crop yield estimation by satellite remote sensing

Two methods for estimating the yield of different crops in Hungary from satellite remote sensing data are presented. The steps of preprocessing the remote sensing data (for geometric, radiometric, atmospheric and cloud scattering correction) are described. In the first method developed for field level estimation, reference crop fields were selected by using Landsat Thematic Mapper (TM) data for classification. A new vegetation index (General Yield Unified Reference Index (GYURI)) was deduced using a fitted double-Gaussian curve to the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data during the vegetation period. The correlation between GYURI and the field level yield data for corn for three years was R 2=0.75. The county-average yield data showed higher correlation (R 2=0.93). A significant distortion from the model gave information of the possible stress of the field. The second method presented uses only NOAA AVHRR and officially reported county-level yield data. The county-level yield data and the deduced vegetation index, GYURRI, were investigated for eight different crops for eight years. The obtained correlation was high (R 2=84.6–87.2). The developed robust method proved to be stable and accurate for operational use for county-, region- and country-level yield estimation. The method is simple and inexpensive for application in developing countries, too.

Temporal variability of the descent of high-altitude NOx inferred from ionospheric data

In this study we investigate periods of enhanced ionization in the mesosphere during Northern Hemisphere wintertime. Long-lasting ionization enhancements (days) are typically produced by solar proton events or by the descent of thermospheric NOX during periods of sustained downward vertical transport associated with a strong underlying polar vortex. Using a new application of ground-based low-frequency radio wave remote sensing, we study the mesospheric ionization conditions during the Northern Hemisphere winters spanning 2003-2004, 2004-2005, and 2005-2006. The winter 2003-2004 subionospheric radio wave propagation data from a transmitter in Iceland shows signatures of the descent of NOX through 80 km altitude starting on 13 January 2004, during the occurrence of a strong polar vortex, indicating a thermospheric source for the NOX. Similar analysis of radio wave propagation data in the Northern Hemisphere winter of 2004-2005 does not show a NOX descent event passing through the mesosphere, due to a lack of downward vertical transport as a result of a weak underlying polar vortex, despite the occurrence of significant solar proton ionization during January 2005. In 2005-2006 there were no significant ionization events and also no descent of significant amounts of thermospheric NOX, despite a strong polar vortex and strong vertical transport. We model the signature of the descent of NOX seen in the radio wave propagation data using the Sodankyla Ion Chemistry model, confirming that the levels of NOX in the mesosphere are similar to 100 times the usual background levels. The combination of strong NOX sources in the thermosphere and also a strong polar vortex is required for NOX to descend into the stratosphere with significant concentration levels.

Correlation between global lightning and whistlers observed at Tihany, Hungary

Although the generation and propagation mechanisms for whistlers are fairly well understood, the location and extent of the lightning source region for the whistlers observed at a given station are ...

Systematic deviations in source direction estimates of Q‐bursts recorded at Nagycenk, Hungary

Q-bursts are globally detectable extremely low frequency (ELF, 3-3000Hz) band wave packets produced by intense lightning discharges. Q-bursts recorded in the Szechenyi Istvan Geophysical Observatory (NCK, 16.7°E, 47.6°N), Hungary, on 1 and 2 August 2012 have been analyzed to find azimuths of their sources. The location of parent lightning strokes of 320 and 205 Q-bursts on the 2days, respectively, have been identified in the records of the World Wide Lightning Location Network (WWLLN) using the detection times at NCK. ELF data-based source azimuths were found to differ systematically from source azimuths obtained from WWLLN lightning locations. The difference between the corresponding azimuth values depends on the azimuth of the source. This variation of the source azimuth error mirrors the symmetry of the conductance of the Earths crust inferred from magnetotelluric measurements around NCK. After correction for the azimuthal dependence, the variation of the residual error shows a diurnal pattern with positive azimuth deviations occurring near midnight, local time. Fullekrug and Sukhorukov (1999) suggested that the anisotropic conductivity in the Earths crust below the observatory and the different daytime and nighttime conductivities in the lower ionosphere, respectively, may cause the identified error terms. Our results emphasize the substantial effect of anisotropic conductivity in the Earths crust around the recording station on the accuracy of ELF direction finding. The need for theoretical approach and more measurements is pointed in understanding the underlying mechanisms quantitatively and in investigating whether ELF observations can be used in geophysical prospecting.

Yield forecasting for wheat and corn in Hungary by satellite remote sensing

We have developed an advanced version of our yield estimation method [Ferencz et al., 2004, Crop yield estimation by satellite remote sensing. International Journal of Remote Sensing, 25, pp. 4113–4149], that is able to provide reliable forecasts for corn and wheat, several weeks before the harvest. The forecasting method is based on the data of the Advanced Very High Resolution Radiometer (AVHRR) instruments of the National Oceanic and Atmospheric Administrations (NOAA) Polar Orbiting Environmental Satellites (POES). The method was applied to Hungary between the years 1996 and 2000. The forecasted yield values are all within 5% reliability with respect to the actual yield data produced by classic (non-satellite based) methods and provided by the Hungarian Statistical Office, with the exception of 1997, where the absolute error is about 8%.

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.