Tropical Cyclone Intensity and Position Analysis Using Passive Microwave Imager and Sounder Data

Satellite based Tropical Cyclone (TC) intensity estimates are critical for TC warning centers and global Numerical Weather Prediction (NWP) Models due to the lack of in-situ observations of mean sea-level pressure and TC winds. Passive microwave instruments on polar-orbiting weather satellites are useful for estimating the intensity of TCs because upwelling microwave radiation can generally penetrate clouds. The upwelling radiation is converted to brightness temperatures and used to measure the intensity of the TC\u27s warm core, precipitation, and ice particle formation via the emitted radiation absorption and scattering signatures. Currently, operational TC prediction centers rely on intensity estimates derived from Polar-orbiting Operational Environmental Satellite (POES) Advanced Microwave Sounding Unit (AMSUA) brightness temperatures. This study compares the performance of a variety of TC intensity estimation techniques using both the imaging and sounding channels from AMSUA, the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager and Sounder (SSMI/S), and the Suomi-National Polar-orbiting Partnership (S-NPP) Advanced Technology Microwave Sounder (ATMS) for a sample of 28 North Atlantic storms from the 2011 through 2013 TC seasons

Satellite Remote Sensing of Tropical Cyclones

This chapter provides a review on satellite remote sensing of tropical cyclones (TCs). Applications of satellite remote sensing from geostationary (GEO) and low earth orbital (LEO) platforms, especially from passive microwave (PMW) sensors, are focused on TC detection, structure, and intensity analysis as well as precipitation patterns. The impacts of satellite remote sensing on TC forecasts are discussed with respect to helping reduce the TC\u27s track and intensity forecast errors. Finally, the multi‐satellite‐sensor data fusion technique is explained as the best way to automatically monitor and track the global TC\u27s position, structure, and intensity

An Overview of the TROPICS NASA Earth Venture Mission

The Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission was selected by NASA as part of the Earth Venture-Instrument (EVI-3) program. The overarching goal for TROPICS is to provide nearly all-weather observations of 3D temperature and humidity, as well as cloud ice and precipitation horizontal structure, at high temporal resolution to conduct high-value science investigations of tropical cyclones. TROPICS will provide rapid-refresh microwave measurements (median refresh rate better than 60 min for the baseline mission) which can be used to observe the thermodynamics of the troposphere and precipitation structure for storm systems at the mesoscale and synoptic scale over the entire storm life cycle. TROPICS comprises six Cube-Sats in three low-Earth orbital planes. Each CubeSat will host a high-performance radiometer to provide temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapour profiles using three channels near the 183 GHz water vapour absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher-resolution water vapour channels), and a single channel near 205 GHz which is more sensitive to precipitation-sized ice particles. This observing system offers an unprecedented combination of horizontal and temporal resolution to measure environmental and inner-core conditions for tropical cyclones on a nearly global scale and is a major leap forward in the temporal resolution of several key parameters needed for assimilation into advanced data assimilation systems capable of utilizing rapid-update radiance or retrieval data.Launch readiness is currently projected for late 2019

Methodology to Analyze Tropical Cyclone Intensity from Microwave Imagery

Satellites with microwave remote sensing capabilities can be utilized to study atmospheric phenomena through high-level cloud cover (particularly cirrus), an advantage over visible and infrared bands, which only sense cloud tops. This unique capability makes microwave imagery ideal for studying the cloud structures of tropical cyclones (TCs) in detail, and relating these features to TC intensity. Techniques to estimate the intensity of TCs using infrared imagery, such as the Dvorak technique, have been used in TC forecasting for 40 years. However, due to the inherent temporal limitations of microwave imagery, no such similar technique exists for the microwave spectrum. This study utilizes pattern recognition to develop a subjective technique for estimating TC intensity using microwave imagery. The dataset includes TC composite imagery from the Special Sensor Microwave Imager (85 GHz), Advanced Microwave Scanning Radiometer-Earth Observing System (89 GHz), Advanced Microwave Scanning Radiometer 2 (89 GHz), and the Special Sensor Microwave Imager/Sounder (91 GHz) from the Atlantic basin, and aircraft reconnaissance data are used for verification. The composite imagery is binned into four categories to facilitate detection of common patterns for TCs of similar size and estimated intensity. This analysis provides the foundation for a new method to estimate TC intensity when aircraft data are unavailable. Multiple techniques are applied to explore relationships between brightness temperature values and TC intensity, and ten test cases in the Western Pacific basin are presented to validate the results. Five out of the ten TCs were classified correctly applying the microwave intensity techniques developed by this analysis

RETRIEVAL OF ICE CLOUD PARAMETERS USING DMSP SPECIAL SENSOR MICROWAVE IMAGER/SOUNDER

Clouds exert a profound influence on both the water balance of the atmosphere and the earth's radiation budget (Stephens 2005; Stephens and Kummerow 2007). Among the global distribution, 30% of them are ice clouds (Riedi et al. 2000). It is important to improve our knowledge of the ice cloud properties in order to determine their influence to the global ecosystem. For ice clouds with millimeter-size ice particles, which are generally found in anvil cirrus and deep convections, microwave and millimeter wave length satellite measurements are suitable for the ice cloud microphysical property retrieval because of its strong ability to penetrate deeper into dense ice clouds. For these types of ice clouds, brightness temperatures at the top of the atmosphere are analytically derived as a function of vertically integrated ice water content (i.e. ice water path), effective particle diameter, and bulk volume density. In general, three brightness temperature measurements are needed to retrieve the three ice cloud microphysical parameters. A two-stream radiative transfer theory was applied to data from the Advanced Microwave Sounding Unit (AMSU) and the Moisture Humidity Sensor (MHS) in order to generate global ice water paths operationally. This research further applied the model and theory to derive ice water path (IWP) from the Special Sensor Microwave Imager/Sounder (SSMIS) onboard the Defense Meteorological Satellite Program (DMSP) F-16 satellite. Compared to AMSU/MHS, which have field of views (FOV) varying with scan position, SSMIS scans the Earth's atmosphere at a constant viewing angle of 53o and therefore offers a uniform FOV within each scan. This unique feature allows for improved global mapping and monitoring of ice clouds so that a more accurate and realistic IWP and ice particle effective diameter distribution is expected. A direct application of SSMIS-derived ice water path is its relationship with surface rain rate as derived previously for AMSU and MHS instruments. Here, SSMIS-derived rain rate was compared to the AMSU and MHS rainfall products and hourly synthetic precipitation observations from rain gauges and surface radar. Results show that SSMIS surface precipitation distribution is spatially consistent and does not have apparent artificial boundary near coastal zones as previously seen in other algorithms. Also, the ice water path associated with a severe storm reasonably delineates the strong convective precipitation areas and has a spatial variation consistent with surface precipitation. From retrieved instantaneous surface precipitation, a tropical and subtropical oceanic precipitation anomaly time series is constructed from 5 year's worth (2005-2009) of SSMIS data. This data record is also linked to the previous constructed SSM/I 15-year (1992-2006) data record to provide a longer term climate study by satellite observations. In future studies, refined algorithms for the estimate of ice cloud base temperature and ice particle bulk volume density are going to be developed to improve the accuracy of IWP retrieval under various cloud vertical distributions. Meanwhile, a better inter-sensor cross calibration scheme is the key to make satellite measurements more useful in climate change study

IMPROVED SATELLITE MICROWAVE RETRIEVALS AND THEIR INCORPORATION INTO A SIMPLIFIED 4D-VAR VORTEX INITIALIZATION USING ADJOINT TECHNIQUES

Microwave instruments provide unique radiance measurements for observing surface properties and vertical atmosphere profiles in almost all weather conditions except for heavy precipitation. The Advanced Microwave Scanning Radiometer 2 (AMSR2) observes radiation emitted by Earth at window channels, which helps to retrieve surface and column integrated geophysical variables. However, observations at some X- and K-band channels are susceptible to interference by television signals transmitted from geostationary satellites when AMSR2 is scanning regions including the U.S. and Europe, which is referred to as Television Frequency Interference (TFI). It is found that high reflectivity over the ocean surface is favorable for the television signals to be reflected back to space. When the angle between the Earth scene vector and the reflected signal vector is small enough, the reflected TV signals will enter AMSR2’s antenna. As a consequence, TFI will introduce erroneous information to retrieved geophysical products if not detected. This study proposes a TFI correction algorithm for observations over ocean. Microwave imagers are mostly for observing surface or column-integrated properties. In order to have vertical temperature profiles of the atmosphere, a study focusing on the Advanced Technology Microwave Sounder (ATMS) is included. A traditional AMSU-A temperature retrieval algorithm is modified to remove the scan biases in the temperature retrieval and to include only those ATMS sounding channels that are correlated with the atmospheric temperatures on the pressure level of the retrieval. The warm core structures derived for Hurricane Sandy when it moved from the tropics to the mid-latitudes are examined. Significant improvements have been obtained for the forecasts of hurricane track, but not intensity, especially during the first 6-12 hours. In this study, a simplified four-dimensional variational (4D-Var) vortex initialization model is developed to assimilate the geophysical products retrieved from the observations of both microwave imagers and microwave temperature sounders. The goal is to generate more realistic initial vortices than the bogus vortices currently incorporated in the Hurricane Weather Research and Forecasting (HWRF) model in order to improve hurricane intensity forecasts. The case included in this study is Hurricane Gaston (2016). The numerical results show that the satellite geophysical products have a desirable impact on the structure of the initialized vortex

Satellite microwave observations of polar lows

Includes bibliographical references

Objectively estimating tropical cyclone intensity and wind structure using the advanced microwave sounding unit

Includes bibliographical references.Estimating tropical cyclone (TC) intensity and structure is becoming increasingly important in light of population expansion along coastal regions. The two most commonly used techniques for estimating TC intensity, the Dvorak Technique and the Objective Dvorak Technique (ODT), utilize visible and infrared satellite imagery. However, both have limitations, as do observing techniques of TC wind structure. Satellite-borne passive microwave radiometers provide an opportune alternative for near real-time assessments of TC maximum sustained winds and wind radii. The first Advanced Microwave Sounding Unit (AMSU), aboard the NOAA-15 polar orbiting satellite, is the first NOAA instrument with sufficient resolution to do so. In this study, data derived from AMSU temperature, pressure, and wind retrievals are used to make objective intensity and wind radii estimates for tropical disturbances in the Atlantic and East Pacific basins. To approximate TC maximum sustained winds and azimuthally averaged wind radii of 34, 50, and 64 kt winds, algorithms are developed via correlations and multiple linear regressions from AMSU data from the 1999 tropical season; they then are tested independently on the 2000 tropical season data Additionally, the AMSU-derived estimates of the azimuthally averaged wind radii are used with a modified Rankine vortex model to assess the wind radii asymmetrically, specifically in the northeast (NE), northwest (NW), southeast (SE), and southwest (SW) quadrants of the TC. Validation data are from the National Hurricane Center (NHC) best track data for the intensity estimates, and from the NHC operational forecast advisories for the average and asymmetric wind radii estimates. Results show the objective AMSU algorithm is comparable to the ODT for estimating TC intensity in the Atlantic, with a root mean square error (RMSE) of 13 kts. The RMSE increases slightly to 16 kts for both basins combined. In general, the AMSU algorithm has a tendency to over (under) approximate the intensity of weak (strong) TCs. For the AMSU-estimated azimuthally averaged 34, 50, and 64 kt wind radii, the mean absolute errors (MAE) are 16, 17, and 8 nautical miles (nm), respectively. With respect to the average radii of each, these correspond to errors of 14.4 percent, 24.6 percent, and 17.8 percent. As with the intensity estimation algorithm, there is a tendency toward over (under) estimation of small (large) azimuthally averaged wind radii by the AMSU. Additionally, the wind radii estimates in the NE, SE, SW, and NW quadrants capture the asymmetric structure well, generally comparing favorably with the NHC operational advisory estimates. In some cases, the AMSU estimates may even be superior to NHC estimates, especially in the Eastern Pacific. Finally, the 1999 and 2000 AMSU data are combined to refine the TC intensity and azimuthally averaged wind radii estimation algorithms. The two-year based algorithms currently are being tested on AMSU data received from the Atlantic and East Pacific basins during the 2001 tropical season.Funding for this research is supplied in part by an American Meteorological Society Graduate Student Fellowship, sponsored by GTE Government Systems, and also by the United States Weather Research Program, NOAA grant NA67RJ0152