E. V. Zabolotskikh

New Possibilities for Geophysical Parameter Retrievals Opened by GCOM-W1 AMSR2

The new Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the GCOM-W1 satellite has additional - comparatively to its predecessor AMSR-E - two channels working in C-band. It is demonstrated in this paper that the measurements at these additional channels can be effectively used for rain pixel identification and rain rate (RR) estimation. It is shown that the rain radiation constituent to the total microwave radiation measured at C- and X-band channels can be calculated. After the rain radiation constituent having been excluded from the brightness temperature, sea surface wind speed (SWS) is possible to be retrieved as if it were no rain, using the retrieval algorithms, developed for non-rain conditions using physical modeling of brightness temperatures. The suggested approach has been applied to several case studies of tropical typhoons including Haiyan case. Sea surface wind speeds retrieved from AMSR2 have been compared with those from Soil Moisture and Ocean Salinity (SMOS) instrument. High correlation has been detected indicating the great potential of AMSR2 SWS retrievals in hurricanes.

Polar low climatology over the Nordic and Barents seas based on satellite passive microwave data

A new climatology of polar lows over the Nordic and Barents seas for 14 seasons (1995/1996–2008/2009) is presented. For the first time in climatological studies of polar lows an approach based on satellite passive microwave data was adopted for polar low identification. A total of 637 polar lows were found in 14 extended winter seasons by combining total atmospheric water vapor content and sea surface wind speed fields retrieved from Special Sensor Microwave/Imager data. As derived, the polar low activity in the Norwegian and Barents Seas is found to be almost equal, and the main polar low genesis area is located northeastward of the North Cape. For the Barents Sea, a significant correlation is found between the number of polar lows and mean sea ice extent. Individual indicative polar low characteristics (i.e., diameter, lifetime, distance traveled, translation speed, and maximum wind speed) are also presented.

A New Generation of Tropical Cyclone Size Measurements from Space

AbstractWind radii estimates in tropical cyclones (TCs) are crucial to helping determine the TC wind structure for the production of effective warnings and to constrain initial conditions for a num...

Geophysical Model Function for the AMSR2 C-Band Wind Excess Emissivity at High Winds

Measurements of the Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the Global Change Observation Mission-Water 1 (GCOM-W1) satellite at 6.925 and 7.3 GHz and both linear polarizations over tropical cyclones (TCs) during 2012-2014 are used to derive a new geophysical function relating the brightness temperature to the sea surface wind speed (SWS) in extreme conditions. Similar sensitivity to the SWS at close C-band frequencies allowed correcting for the atmospheric contributions to the microwave radiance and estimating the brightness temperature (TB) at the surface under TCs, combining theoretical modeling and measured TB analyses. Estimated oceanic TBs were regressed against the wind speeds from the Best Track Archive to derive a new geophysical model function for the wind speed excess emissivity at AMSR2 C-band microwave frequencies.

Sea surface wind and Sea ice in the Barents Sea using microwave sensing data from Meteor-M N1 and GCOM-W1 satellites in January–March 2013

Application of satellite passive microwave sensing for the retrieval of key climatic parameters in the Barents Sea is considered. Fields of surface wind, atmosphere water vapor content and cloud liquid water content were found from MTVZA-GY radiometer onboard the Meteor-M N1 satellite and AMSR2 onboard the GCOM-W1 satellite with the use of original algorithms. The fields are in a good agreement with the ancillary remote and in situ measurements, which follows from the analysis of the evolution of the extra tropical and polar cyclones and cold air outbreaks with storm winds leading to intense air-sea interaction, and the formation and drift of sea ice.

Neural network-based method for the estimation of the rain rate over oceans by measurements of the satellite radiometer AMSR2

The rain rate (RR) retrieval method for the RR estimation over ice-free areas of the ocean is presented. Measurements of the Japanese Advanced Microwave Scanning Radiometer 2 (AMSR2) on board the satellite GCOM-W1 are used. The method is based on the results of the numerical modeling of brightness temperatures of the outgoing microwave radiation of the ocean–atmosphere system and their subsequent conversion into the RR using neural networks. A simplified form of the transfer equation is used. Its errors for the considered wavelengths do not exceed 1 K at an RR of less than 20 mm/h. The method is verified by comparison with the Tropical Rainfall Measuring Mission’s (TRMM) Microwave Instrument (TMI) RR product. As a result of the comparison, the rain rate retrieval error within the range of 20 mm/h is found to be 1 mm/h.

A Pilot Satellite-Based Investigation of the Impact of a Deep Polar Cyclone Propagation on the Phytoplankton Chlorophyll Spatial and Temporal Dynamics in the Arctic Ocean

A pilot satellite-based investigation of modulations exerted upon mixed-layer phytoplankton fields by deep cyclones is performed for the first time across the northern hemisphere polar region, viz. the Arctic Ocean. Resorting to a synergistic approach, polar cyclones were first identified from NCEP/NCAR data for the summer time period during 2002–2005, and their propagation throughout the Barents Sea was further traced down. The above water wind force was retrieved from QuikSCAT data. These data were further accompanied by ocean colour data from SeaWiFS, and MODIS to examine the spatial and temporal distributions of surficial phytoplankton chlorophyll concentration dynamics along the trajectory of the cyclone’s footprint across the sea. When the wind speed, bathymetric features and cloud conditions proved conjointly favorable, appreciable increases in phytoplankton chlorophyll concentration (for basically oligotrophic waters of the Arctic Ocean) have been observed following the cyclone passage with a time lag of about 5 days. This implies that with the ongoing amplification of climate warming at high northern latitudes, the increase in chlorophyll discussed above is potentially capable of boosting the primary production in the Arctic Ocean. However, further studies are certainly required to extend the observational data up to 2012 and further on in order to statistically and phenomenologically underpin and further our understanding of the actual mechanisms of changes in the Arctic Ocean ecosystem functioning.

Contemporary methods for retrieving the integrated atmospheric water-vapor content and the total cloud liquid-water content

A review of contemporary methods for determining integrated parameters of the water content in the atmosphere―atmospheric water-vapor content and cloud liquid-water content―is presented. Fields of these parameters can only be mapped spatially on the basis of using data of satellite measurements. The least errors of the retrieval of atmospheric water-vapor content and cloud liquid-water content is provided by methods based on using measurements of the satellite-borne scanning multichannel microwave radiometers over the ice-free ocean areas in the absence of precipitation. Most methods for retrieving the atmospheric water-vapor content and cloud liquid-water content from the data of microwave radiometers are based on results of numerical simulation of brightness temperatures of the upwelling microwave radiation of the ocean–atmosphere system. The evolution of satellite-borne microwave radiometers and methods for the retrieval of integrated parameters of water content is presented.

Statistical characteristics of polar lows over the Nordic Seas based on satellite passive microwave data

In this study polar lows over the Nordic Seas for the period of 1995–2008 have been detected and studied using the Special Sensor Microwave Imager (SSM/I) data. A new methodology for polar low detection and monitoring based on the analysis of the total atmospheric water vapor content (WVC) fields retrieved from SSM/I was used. Lifetimes, diameters, translation speeds, distances traveled, and intensities were estimated for the detected polar lows using SSM/I WVC, sea surface wind speed fields and infrared imagery. Over the Norwegian and Barents Seas, the polar low activity was found to be almost equal. A positive tendency in the total number of polar lows for the time period of 1995–2008 was detected.

New areas of polar lows over the Arctic as a result of the decrease in sea ice extent

Three mesocyclones (MCs) over the Russian (Eastern) Arctic are investigated using multispectral satellite remote sensing data, surface analysis maps, and reanalysis data. Advanced retrieval algorithms are used for estimating the geophysical parameter from satellite passive microwave measurements. These methods allow reconstructing in full the geophysical parameter fields characterizing polar lows. Synoptic analysis along with cloud image, atmospheric water vapor content, cloud liquid water content, and sea surface wind speed field analysis show that, while the Arctic sea ice retreats, new areas of open water appear where MCs can arise. A detailed study of several polar low cases reveals the typical conditions of their formation and development. Further studies are in demand due to the danger of MC extreme events for navigation, transport, and fishery operations in these unexplored regions.