G. Heygster | University of Bremen (original) (raw)

Papers by G. Heygster

Bulletin of the American Meteorological Society

Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to t... more Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project has been established in 2016 (http://www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, ship-borne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities du...

Соционика, ментология и психология личности, 2018

Optik, 1994

A theory for surface structure imaging is presented, which allows the computation of optical tran... more A theory for surface structure imaging is presented, which allows the computation of optical transfer functions (OTF) of the scanning acoustic microscope (SAM). The model describes the monitor image in terms of the reflectivity of the specimen, thus including the influence of the confocal lens system and subsequent signal processing. Amplitude and phase contrast imaging in SAM are defined, and the corresponding OTF computed for different focus positions are shown to be in good agreement with measurements. Based on the theoretical OTF, an image restoration scheme for phase contrast imaging is developed. Combining images of a focal series, the imaging properties of SAM for phase contrast can be improved

2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016

Sea ice is an important quantity for the radiation budget of the Earth's climate system. In t... more Sea ice is an important quantity for the radiation budget of the Earth's climate system. In this paper we present a comparison of SMAP and SMOS measured brightness temperatures and translate a validated retrieval algorithm for the thickness of thin sea ice from SMOS to SMAP radiometer observations. For October to December all observations of SMAP in forward and backward direction are compared as daily averages and found with low RMSD of 2.25K and 2.42K in TB,v and TB,h, respectively. The mean of forward and backward observations from SMAP are mapped to SMOS equivalent brightness temperatures using a linear regression. SMAP was found to yield lower brightness temperatures compared to SMOS by about 5K in both polarizations while difference decreases with increasing brightness temperatures. An existing ice thickness retrieval for SMOS using averaged brightness temperatures in the incidence angles range of 40° to 50° is transferred to SMAP using another linear regression. Ice thickn...

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014

ABSTRACT The Dutch, German, and Danish Wadden Sea is one of the largest tidal flats in the world ... more ABSTRACT The Dutch, German, and Danish Wadden Sea is one of the largest tidal flats in the world which has been left in a nearly natural state. Several studies generated the topography of this valuable area, but presented only single maps, which covered partial regions of the Wadden Sea. The objectives of this paper are 1) to use the waterline method to analyze SAR images in order to generate annual topographic maps of the northern parts of the German Wadden Sea for the years 1996-1999 and 2006-2009 and 2) to quantitatively estimate and monitor the development of the tidal flats. The waterlines are detected by a wavelet-based edge detection algorithm, geocoded in Gauss-Krueger coordinates, assigned with water level information, and interpolated into topographic maps. Our results show the development of the tidal flats over the 8 years and illustrate three of the most changing regions: Tertiussand, Gelbsand, and Medemsand. Their area, shape, and sediment volume have changed significantly due to the tide, wave, wind, and river discharge influences. The waterline method is an efficient and economical way to monitor large tidal flat areas, which allows an estimation of long-term morphological development. One potential application is to assimilate the results into morphodynamic models in order to give finer morphological predictions.

IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Development, 1997

ABSTRACT A method to retrieve the total water vapor in the cloudless atmosphere using SSM/T2 chan... more ABSTRACT A method to retrieve the total water vapor in the cloudless atmosphere using SSM/T2 channels is proposed based on a unique property of three contiguous channels situated on the flank of the water vapor absorption line at 183.31 GHz. One of its advantages is its independence to the surface emission, which is the main disturbing factor in retrieving atmospheric parameters from passive satellite measurements. Due to the high sensitivity of the SSM/T2 channels to water vapor, this method is suitable to the total water vapor retrieval for dry polar atmospheres. An algorithm is constructed for austral winter cases through model simulation using radiosonde profiles

ABSTRACT In this paper we present the newly developed analytical description of the radiative tra... more ABSTRACT In this paper we present the newly developed analytical description of the radiative transfer in the sea ice in visible and near IR region and the idea and first results of the retrieval of the melt pond fractions from data of a satellite spectral sensor. This retrieval is based on the analytical description of the optical properties of sea ice as a scattering medium.

2014 IEEE Geoscience and Remote Sensing Symposium, 2014

The influence of sea ice thickness brightness temperatures and ice concentrations retrieved from ... more The influence of sea ice thickness brightness temperatures and ice concentrations retrieved from passive microwave observations is quantified, using horizontally homogeneous sea ice thickness retrievals from ESA's SMOS sensor observations at high incidence angles. Brightness temperatures are influenced by thickness below 18 cm (89GHz) and 50 cm (1.4 GHz). Ice concentration retrievals reduced by ice thickness below 0.17 m and 0.33 m, with higher frequency algorithms being less influenced.

Eos, Transactions American Geophysical Union, 2008

Journal of the Meteorological Society of Japan, 2004

IEEE Transactions on Geoscience and Remote Sensing, 2008

Journal of Hydrometeorology, 2009

Satellite-retrieved data of total water vapor (TWV) over the Arctic are patchy, with large areas ... more Satellite-retrieved data of total water vapor (TWV) over the Arctic are patchy, with large areas of missing data because of various limitations of the retrieval algorithms. To overcome these observational difficulties, a new retrieval algorithm has been developed that allows for monitoring the TWV over the Arctic during most of the year. This method retrieves TWV from satellite microwave radiometer data [the Advanced Microwave Sounding Unit B (AMSU-B)]. These new data have been made available for 4 yr (2000–03) and have been used to evaluate high-resolution simulations with the Arctic regional atmospheric climate model HIRHAM at daily, monthly, and seasonal time scales. The strong dynamic TWV variability on the daily time scale, linked with moisture transport by weather systems, is discussed for selected case studies. Both the simulated climatological seasonal mean patterns and the variability on interannual and decadal time scales are in agreement with those of the 40-yr European C...