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Proceedings ArticleDOI

Radiometric measurements of cloud attenuation over Earth-space path at a tropical location

01 Aug 2017-pp 1-3

TL;DR: In this paper, real time estimates of cloud attenuation have been made using ground-based microwave radiometric observations of Liquid Water Content at a tropical location, and it is found that the significant amount of clouds attenuation occurs during monsoon season.

AbstractIn this study, real time estimates of cloud attenuation have been made using ground based microwave radiometric observations of Liquid Water Content at a tropical location. It is found that the significant amount of cloud attenuation occurs during monsoon season. Individual case study additionally shows that cloud attenuation can contribute significantly to the overall signal degradation at various frequency bands.

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Citations
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Dissertation
18 Nov 2015

7 citations


Cites background from "Radiometric measurements of cloud a..."

  • ...20 extensively demonstrated to work favourably with data from tropical areas with high rainfall rates [Awang and Din, 2004; Das et al., 2010]....

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  • ...However, there are concerns about this method as it appears that it leads to the under-estimation of specific attenuation in tropical locations [Das et al., 2010] and overestimation in subtropical locations [Alonge and Afullo, 2012b]....

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  • ...The lognormal DSD model is most preferred model in the descriptive statistics of rainfall DSD in tropical areas around the world because it works well at regions with high rainfall rate occurrence [Ong and Shan, 1997; Awang and Din, 2004; Das et al., 2010]....

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  • ...The lognormal model has been proposed in several studies as the foremost model useful for rainfall DSD estimation in tropical and subtropical locations from measurements [Ajayi et al., 1996; Das et al., 2010]....

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  • ...The first two models have been Queueing Theory Approach to Rain Fade Analysis at Microwave and Millimeter Bands in Tropical Africa 20 extensively demonstrated to work favourably with data from tropical areas with high rainfall rates [Awang and Din, 2004; Das et al., 2010]....

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Journal ArticleDOI
TL;DR: In this article, the authors examined the cloud parameters over few stations in India for one year from October 2016 to September 2017 and found that cloud base height from WVP-NTU model matches well with METAR data.
Abstract: An effort is made to examine the cloud parameters over few stations in India for one year from October 2016 to September 2017. This study includes the investigation of cloud base height, cloud top height, zero degree isotherm height, number of cloud layers, cloud thickness, number of days cloud detected, cloud liquid water content and cloud attenuation at 6 GHz, 12.5 GHz and 24 GHz. Salonen Uppala (SU) model and Water Vapor Pressure-Nanyang Technological University (WVP-NTU) model are used for cloud detection using the radiosonde data at Bangalore, Hyderabad, Mumbai, Thiruvananthapuram and Chennai. The cloud parameters found using both the models are compared. WVP-NTU model shows enhanced values for most of the cloud parameters over SU model. Cloud base height calculated using these models are compared with METAR data and found that Cloud base height from WVP-NTU model matches well with METAR data. Cloud liquid water content and cloud attenuation values are calculated using the ITU-R model. The cumulative distributions (CDF) of cloud attenuation for one year are compared for the places considered. The seasonal CDFs of cloud attenuation using the WVP model are compared with the rain statistics. In this study, the maximum cloud attenuation of 1.67 dB/km is measured in Hyderabad by WVP-NTU combined ITU-R model at 24 GHz.

1 citations


References
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Journal ArticleDOI
TL;DR: In this article, a microwave radiometer was used for nowcasting of heavy rain events at Kolkata (22.65°N, 88.45°E), a tropical location.
Abstract: Summary Nowcasting of heavy rain events using microwave radiometer has been carried out at Kolkata (22.65°N, 88.45°E), a tropical location. Microwave radiometer can produce the temperature and humidity profiles of the atmosphere with fairly good accuracy. Definite changes are observed in temperature and humidity profiles before and at the onset of heavy rain events. Concurrent changes in the brightness temperatures (BT) at 22 GHz and 58 GHz are found to be suitable to nowcast rain. The time derivatives of brightness temperatures at 22 GHz and 58 GHz are used as inputs to the proposed nowcasting model. In addition, the standard deviation of the product of these time derivatives is also considered. The model has been developed using the data of 2011 and validated for rain events of 2012–2013 showing a prediction efficiency of about 90% with alarm generated about 25 min in advance.

26 citations


"Radiometric measurements of cloud a..." refers background in this paper

  • ...From the above figure, it has been shown that for monsoon, the LWP value is high in the afternoon which may be due to convective activities at the present tropical location [7-9]....

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Journal ArticleDOI
TL;DR: In this article, the effectiveness of nowcasting convective activities using a microwave radiometer has been examined for Kolkata (22.65° N, 88.45° E), a tropical location.
Abstract: In the present study, the effectiveness of nowcasting convective activities using a microwave radiometer has been examined for Kolkata (22.65° N, 88.45° E), a tropical location. It has been found that the standard deviation of brightness temperature (BT) at 22 GHz and instability indices like Lifting Index (LI), K Index (KI) and Humidity Index (HI) has shown definite changes before convective events. It is also seen that combination of standard deviation of BT at 22 GHz and LI can be most effective in predicting convection. A nowcasting algorithm is prepared using 18 isolated convective events of 2011 and in all cases, a marked variation of these parameters has been seen an hour before the event. Accordingly, a prediction model is developed and tested on convective events of 2012 and 2013. It is seen that the model gives reasonable success in predicting convective rain about 7075 min in advance with a prediction efficiency of 80%.

22 citations


"Radiometric measurements of cloud a..." refers background in this paper

  • ...From the above figure, it has been shown that for monsoon, the LWP value is high in the afternoon which may be due to convective activities at the present tropical location [7-9]....

    [...]

Journal ArticleDOI
TL;DR: In this article, some features of cloud liquid water content with respect to rain and water vapor are presented and the variation of daily total rainfall with LWC shows a positive relationship indicating the role of LWC in controlling the rainfall.
Abstract: In this paper, some features of cloud liquid water content with respect to rain and water vapor are presented. Cloud liquid water density profile is obtained from radiosonde observation with Salonen's model and Karsten's model at Kolkata, a tropical location in the Indian region. Cloud liquid water contents (LWC) are obtained from these profiles which show a prominent seasonal variation. The monsoon months exhibit much higher values of LWC than in other months. However Salonen's model yields higher LWC values than that obtained with Karsten's model. The variation of daily total rainfall with LWC shows a positive relationship indicating the role of LWC in controlling the rainfall. Also the variation pattern of LWC with integrated water vapor (IWV) content of the atmosphere indicates that a threshold value of water vapor is required for cloud to form and once cloud is formed LWC increases with IWV.

19 citations


"Radiometric measurements of cloud a..." refers methods in this paper

  • ...The retrieval of liquid water content using Karsten and Salonen model have already been done [1]....

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Proceedings ArticleDOI
01 Aug 2014
TL;DR: In this paper, the effects of the convective rain on various atmospheric parameters have been investigated at Kolkata (22.57°N, 88.37°E), India, during pre-monsoon and monsoon period of 2013.
Abstract: The effects of the convective rain on various atmospheric parameters have been investigated at Kolkata (22.57°N, 88.37°E), India, during pre-monsoon and monsoon period of 2013. Various parameters like cloud base height and depth, liquid water content, rain rate and rain drop size distribution (DSD) are observed concurrently. The atmospheric electric field measured with an electric field monitor and the attenuation and depolarisation of satellite signals measured by a Ku-band receiving system are also studied during rain events. The instability indices obtained from radiometric measurements and the rain height profiles from micro rain radar are used to classify rain into two types, namely, convective and stratiform. The signatures of rain events on multi-technique observations are studied to indicate the various aspects of convective processes at a tropical location.

17 citations


"Radiometric measurements of cloud a..." refers background in this paper

  • ...From the above figure, it has been shown that for monsoon, the LWP value is high in the afternoon which may be due to convective activities at the present tropical location [7-9]....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a technique by which the diversity gain can be estimated for a site utilizing the propagation data obtained at a single station, which is crucial in estimating diversity parameters in the absence of multi-station data.
Abstract: The present study proposes a technique by which the diversity gain can be estimated for a site utilizing the propagation data obtained at a single station. The technique is crucial in estimating diversity parameters in the absence of multi-station data. The rain decay parameter, as defined in the Simple Attenuation Model (SAM), is used to derive the rain rate and consequently rain attenuation at different distances from the single receiving site. The tropical location has been found to experience a wide variability of rain features during different periods of the year causing strong seasonal variations in the diversity gain. A comparison of the diversity gain obtained from the present propagation data and the ITU-R model indicates the necessity of modifying the model parameters of the ITU-R model. The modified model incorporates the seasonal variation and exhibits better prediction capability than the ITU-R model as related to the tropical location.

11 citations


"Radiometric measurements of cloud a..." refers methods in this paper

  • ...The disdrometer has been used to estimate the rain rate [3-5]....

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