scholarly journals Validation and Development of Melting Layer Models Using Constraints by Active/Passive Microwave Observations of Rain and the Wind-Roughened Ocean Surface

2007 ◽  
Vol 24 (4) ◽  
pp. 543-563 ◽  
Author(s):  
Shannon T. Brown ◽  
Christopher S. Ruf
Keyword(s):  
Wind Speed ◽  
Brightness Temperature ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Forward Model ◽  
Dual Frequency ◽  
Layer Model ◽  
Atmospheric Absorption ◽  
Melting Layer ◽  
Stratiform Rain

Abstract A physically based method is developed to estimate the microphysical structure of the melting layer in stratiform rain using airborne observations by a dual-frequency radar and a 10.7-GHz radiometer. The method employs a nonlinear optimal estimation approach to find two parameters of the gamma drop size distribution (DSD) at each radar range gate from the Ku/Ka-band reflectivities. The DSD profile is used to determine the atmospheric absorption/extinction profile, which enables the surface contribution to the measured brightness temperature to be estimated. The surface wind speed is estimated from the surface emissivity by inverting the forward model, which relates the two. Retrievals in stratiform precipitation require a model to describe the thermodynamic and electromagnetic properties of melting hydrometeors. The melting layer can contribute a majority of the total atmospheric absorption, making it a key component for accurate retrievals in stratiform rain. Several melting layer models were evaluated based on their fit to the dual-frequency reflectivity measurements in the melting layer. A candidate model is selected and tuned to match the radar measurements. The melting layer model is then incorporated into the full forward model for the brightness temperature observed by the radiometer. The surface wind speed assumed in the forward model is forced by the radiometer observations. If the actual surface wind speed is known, this approach provides a powerful constraint on the possible melting layer model. A case study is presented from an airborne campaign over areas of precipitation off the coast of Vancouver Island, British Columbia, Canada. The estimated wind speeds are found to be uncorrelated with the reflectivity and their average value is within 1 m s−1 of that retrieved in a clear area adjacent to the rain.

scholarly journals Satellite Microwave Surface Observations in Tropical Cyclones

2010 ◽  
Vol 138 (2) ◽  
pp. 421-437 ◽  
Author(s):  
Yves Quilfen ◽  
Bertrand Chapron ◽  
Jean Tournadre
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
Rain Rate ◽  
Microwave Radiometer ◽  
Surface Wind ◽  
Tropical Rainfall Measuring Mission ◽  
Heavy Rain ◽  
Surface Wind Speed ◽  
Microwave Measurements ◽  
Dual Frequency

Abstract Sea surface estimates of local winds, waves, and rain-rate conditions are crucial to complement infrared/visible satellite images in estimating the strength of tropical cyclones (TCs). Satellite measurements at microwave frequencies are thus key elements of present and future observing systems. Available for more than 20 years, passive microwave measurements are very valuable but still suffer from insufficient resolution and poor wind vector retrievals in the rainy conditions encountered in and around tropical cyclones. Scatterometer and synthetic aperture radar active microwave measurements performed at the C and Ku band on board the European Remote Sensing (ERS), the Meteorological Operational (MetOp), the Quick Scatterometer (QuikSCAT), the Environmental Satellite (Envisat), and RadarSat satellites can also be used to map the surface wind field in storms. Their accuracy is limited in the case of heavy rain and possible saturation of the microwave signals is reported. Altimeter dual-frequency measurements have also been shown to provide along-track information related to surface wind speed, wave height, and vertically integrated rain rate at about 6-km resolution. Although limited for operational use by their dimensional sampling, the dual-frequency capability makes altimeters a unique satellite-borne sensor to perform measurements of key surface parameters in a consistent way. To illustrate this capability two Jason-1 altimeter passes over Hurricanes Isabel and Wilma are examined. The area of maximum TC intensity, as described by the National Hurricane Center and by the altimeter, is compared for these two cases. Altimeter surface wind speed and rainfall-rate observations are further compared with measurements performed by other remote sensors, namely, the Tropical Rainfall Measuring Mission instruments and the airborne Stepped Frequency Microwave Radiometer.

Attenuation Correction over Ocean for the HIWRAP Dual-Frequency Airborne Scatterometer

2019 ◽  
Vol 36 (10) ◽  
pp. 2015-2030
Author(s):  
R. Meneghini ◽  
L. Liao ◽  
G. M. Heymsfield
Keyword(s):  
Wind Speed ◽  
Attenuation Correction ◽  
Cross Section ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Calibration Error ◽  
Dual Frequency ◽  
Near Surface ◽  
Ka Band ◽  
The Difference

AbstractAn important objective in scatterometry is the estimation of near-surface wind speed and direction in the presence of rain. We investigate an attenuation correction method using data from the High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) dual-frequency scatterometer, which operates at Ku and Ka band with dual conical scans at incidence angles of 30° and 40°. The method relies on the fact that the differential normalized surface cross section, δσ0 = σ0(Ka) − σ0(Ku), is relatively insensitive to wind speed and direction and that this quantity is closely related to the magnitude of the differential path attenuation, δA = A(Ka) − A(Ku), arising from precipitation, cloud, and atmospheric gases. As the method relies only on the difference between quantities measured in the presence and absence of rain, the estimates are independent of radar calibration error. As a test of the method’s accuracy, we make use of the fact that the radar rain reflectivities just above the surface, as seen along different incidence angles, are approximately the same. This yields constraint equations in the form of differences between pairs of path attenuations along different lines of sight to the surface. A second validation method uses the dual-frequency radar returns from the rain just above the surface where it can be shown that the difference between the Ku- and Ka-band-measured radar reflectivity factors provide an estimate of differential path attenuation. Comparisons between the path attenuations derived from the normalized surface cross section and those from these surface-independent methods generally show good agreement.

scholarly journals 3DVAR assimilation of SSM/I data over the sea for the IOP2b MAP case

2005 ◽  
Vol 2 ◽  
pp. 229-235 ◽  
Author(s):  
C. Faccani ◽  
D. Cimini ◽  
R. Ferretti ◽  
F. S. Marzano ◽  
A. C. Taramasso
Keyword(s):  
Wind Speed ◽  
Brightness Temperature ◽  
Initial Conditions ◽  
Surface Wind ◽  
Precipitable Water ◽  
Surface Wind Speed ◽  
Large Variability ◽  
Brightness Temperatures ◽  
Initial Dataset ◽  
Microwave Imager

Abstract. Data assimilation by 3DVAR of data from the Special Sensor Microwave/Imager (SSM/I) has been performed to study the IOP2b case (19-21 September 1999) of the Mesoscale Alpine Programme (MAP). Only data over the sea surface are used to avoid the contamination of the surface emissivity. Moreover, the rainy data are filtered out because the assimilation algorithm of 3DVAR does not take into account the scattering processes. SSM/I data are assimilated in two different ways: as Brightness Temperature directly, or as Precipitable Water and surface wind speed retrieved from the Brightness Temperature. The effect of the thinning of the observations has been studied and a set of sensitivity test cases has been carried out; the one by one removal of the SSM/I frequencies from the initial dataset allows to evaluate their impact on the Initial Conditions. A few experiments are performed using these new Initial Conditions to initialize the MM5 (PSU/NCAR) model. The results show that the assimilation of the retrieved quantities, i.e. Precipitable Water and surface wind speed, does not produces large improvement in the Initial Conditions. Vice versa, the assimilation of the Brightness temperatures produces a large variability of the Initial Conditions. The forecast experiments show that the model is very sensitive to the 22GHz and 37GHz frequencies.

scholarly journals A dual-frequency approach for retrieving sea surface wind speed from TOPEX altimetry

2002 ◽  
Vol 107 (C12) ◽  
pp. 19-1-19-10 ◽  
Author(s):  
Ge Chen ◽  
Bertrand Chapron ◽  
Robert Ezraty ◽  
Douglas Vandemark
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Surface ◽  
Dual Frequency ◽  
Sea Surface Wind Speed ◽  
Sea Surface Wind

Recurrence Characteristics Analysis of Near-Surface Wind Speed Signal with Different Sampling Frequencies

2014 ◽  
Vol 599-601 ◽  
pp. 1605-1609 ◽  
Author(s):  
Ming Zeng ◽  
Zhan Xie Wu ◽  
Qing Hao Meng ◽  
Jing Hai Li ◽  
Shu Gen Ma
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Recurrence Plot ◽  
Sampling Frequency ◽  
Near Surface ◽  
Gas Leakage ◽  
Time Period ◽  
Characteristics Analysis ◽  
Quantification Analysis

The wind is the main factor to influence the propagation of gas in the atmosphere. Therefore, the wind signal obtained by anemometer will provide us valuable clues for searching gas leakage sources. In this paper, the Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are applied to analyze the influence of recurrence characteristics of the wind speed time series under the condition of the same place, the same time period and with the sampling frequency of 1hz, 2hz, 4.2hz, 5hz, 8.3hz, 12.5hz and 16.7hz respectively. Research results show that when the sampling frequency is higher than 5hz, the trends of recurrence nature of different groups are basically unchanged. However, when the sampling frequency is set below 5hz, the original trend of recurrence nature is destroyed, because the recurrence characteristic curves obtained using different sampling frequencies appear cross or overlapping phenomena. The above results indicate that the anemometer will not be able to fully capture the detailed information in wind field when its sampling frequency is lower than 5hz. The recurrence characteristics analysis of the wind speed signals provides an important basis for the optimal selection of anemometer.

Ocean surface wind speed retrieval from C-band quad-polarized SAR measurements at optimal spatial resolution

2020 ◽  
Vol 12 (2) ◽  
pp. 155-164
Author(s):  
He Fang ◽  
William Perrie ◽  
Gaofeng Fan ◽  
Tao Xie ◽  
Jingsong Yang
Keyword(s):  
Wind Speed ◽  
Spatial Resolution ◽  
Surface Wind ◽  
Ocean Surface ◽  
Surface Wind Speed ◽  
Ocean Surface Wind
Sign in / Sign up

Export Citation Format

Share Document