Identification of rainy periods from ground based microwave radiometry

Abstract

In this paper the authors present the results of a study aiming at detecting rainy data in measurements collected by a dual band ground-based radiometer. The proposed criterion is based on the ratio of the brightness temperatures observed in the 20-30 GHz band without need of any ancillary information. A major result obtained from the probability density of the ratio computed over one month of data is the identification of threshold values between clear sky, cloudy sky and rainy sky, respectively. A linear fit performed by using radiometric data and concurrent rain gauge measurements shows a correlation coefficient equal to 0.56 between the temperature ratio and the observed precipitation.

On the Use of Microwave Radiometers for Deep Space Mission Applications by Means of a Radiometric-Based Scalar Indicator

“…SSI is defined as the ratio between the brightness temperatures observed at 23.8 and 31.4 GHz, and it is employed to discriminate among LOS sky conditions (clear sky, cloudy, or rainy) to select the most reliable path delay retrievals in the tropospheric correction algorithm. The discriminating aspects of performance within SSI were tested in previous works [18], [26] with radiometric observations mainly at zenith or at fixed elevation angles [27]. Here, the method has been further developed for its application to deep-space probes radio tracking, with SSI being parameterized as a function of the elevation angle to be commanded by a radiometer equipped with a steering mechanism.…”

“…The present study aims at addressing the use of the AMC approach with respect to the TSAC through the implementation of an atmospheric index, a scalar quantity named sky status indicator (SSI) [18], based on the radiometer measurements. The SSI capability of validating the use of AMC retrieved path delay in the calibration of the deep space navigation observables is addressed by analyzing the quality of Cassini's range 1939-1404 © 2015 IEEE.…”

The role of both location and radiometer accuracy on the SSI performance in discriminating the atmospheric conditions

“…In this context, ground-based microwave radiometers (MWR) are exploited for their ability to sense the atmospheric thermodynamic features of a satellite channel [Tanner and Riley, 2003;Ware at al., 2003;Crewell et al, 2009]. Based on brightness temperature values T b (f), measured by a MWR at 20/30 GHz band, the authors developed a scalar indicator, the Sky Status Indicator (SSI), that can help in discriminating among clear, cloudy and rainy sky conditions [Bosisio and Capsoni, 1995;Bosisio et al, 2012]. A dataset of T b (f) values, collected in Cabauw (NL) by the ESA ATPROP System [Rose, 2008] along zenithal (θ=90°) and slant path (at θ=69.6°), was used to compute the SSI as the ratio of T b (f) values at 31.4 and 23.8 GHz, properly modified to subtract the contribution of the gaseous dry emission (mainly due to O 2 ) of the Earth atmosphere [Bosisio et al, 2012].…”

“…Based on brightness temperature values T b (f), measured by a MWR at 20/30 GHz band, the authors developed a scalar indicator, the Sky Status Indicator (SSI), that can help in discriminating among clear, cloudy and rainy sky conditions [Bosisio and Capsoni, 1995;Bosisio et al, 2012]. A dataset of T b (f) values, collected in Cabauw (NL) by the ESA ATPROP System [Rose, 2008] along zenithal (θ=90°) and slant path (at θ=69.6°), was used to compute the SSI as the ratio of T b (f) values at 31.4 and 23.8 GHz, properly modified to subtract the contribution of the gaseous dry emission (mainly due to O 2 ) of the Earth atmosphere [Bosisio et al, 2012]. Afterwards, the SSI discrimination capabilities were assessed against rain gauge precipitation measurements demonstrating the good performances of the proposed indicator to discriminate the three above mentioned sky propagation conditions [Bosisio et al, 2013a[Bosisio et al, , 2013b.…”

Atmospheric Propagation at 100 and 300 Ghz: Assessment of a Method to Identify Rainy Conditions During Radiosoundings

“…Considering that RAOBs data do not provide a direct numerical parameter allowing events to be classified as rainy or non-rainy, the main goal of the present paper is to propose and assess a method using information extracted from RAOBs and colocated synoptical observations of weather (SYNOP reports), in order to identify and filter out those radiosoundings. The issue of detecting rainy periods is relevant in propagation campaigns and has already been discussed by other authors, using with this purpose measurements of sky brightness temperature collected by dualfrequency radiometers [12,24].…”