A simple biota removal algorithm for 35 GHz cloud radar measurements

A simple biota removal algorithm for 35 GHz cloud radar measurements

Cloud radar reflectivity profiles can be an important measurement for the investigation of cloud vertical structure (CVS). However, extracting intended meteorological cloud content from the measurement often demands an effective technique or algorithm that can reduce error and observational uncertai...

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Bibliographic Details
Published in:Atmospheric measurement techniques Vol. 11; no. 3; pp. 1417 - 1436
Main Authors: Kalapureddy, Madhu Chandra R, Sukanya, Patra, Das, Subrata K, Deshpande, Sachin M, Pandithurai, Govindan, Pazamany, Andrew L, Ambuj K., Jha, Chakravarty, Kaustav, Kalekar, Prasad, Devisetty, Hari Krishna, Annam, Sreenivas
Format: Journal Article
Language:English
Published: Katlenburg-Lindau Copernicus GmbH 12-03-2018
Copernicus Publications
Subjects:
Algorithms
Biota
Boundary layers
Cloud height
Cloud investigations
Clouds
Clouds (Meteorology)
Cumulus clouds
Depolarization
Doppler sonar
Dynamic meteorology
Echoes
Error reduction
Filtration
Hydrometeors
Insects
Mathematical models
Measurement
Mixed layer
Profiles
Properties
Radar
Radar clutter
Radar echoes
Radar polarimetry
Radar reflectivity
Rainmaking
Reflectance
Removal
Screening
Sensitivity
Statistical methods
Statistical tests
Summer monsoon
Turbulence
Vertical profiles
Weather
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Summary:Cloud radar reflectivity profiles can be an important measurement for the investigation of cloud vertical structure (CVS). However, extracting intended meteorological cloud content from the measurement often demands an effective technique or algorithm that can reduce error and observational uncertainties in the recorded data. In this work, a technique is proposed to identify and separate cloud and non-hydrometeor echoes using the radar Doppler spectral moments profile measurements. The point and volume target-based theoretical radar sensitivity curves are used for removing the receiver noise floor and identified radar echoes are scrutinized according to the signal decorrelation period. Here, it is hypothesized that cloud echoes are observed to be temporally more coherent and homogenous and have a longer correlation period than biota. That can be checked statistically using ∼ 4 s sliding mean and standard deviation value of reflectivity profiles. The above step helps in screen out clouds critically by filtering out the biota. The final important step strives for the retrieval of cloud height. The proposed algorithm potentially identifies cloud height solely through the systematic characterization of Z variability using the local atmospheric vertical structure knowledge besides to the theoretical, statistical and echo tracing tools. Thus, characterization of high-resolution cloud radar reflectivity profile measurements has been done with the theoretical echo sensitivity curves and observed echo statistics for the true cloud height tracking (TEST). TEST showed superior performance in screening out clouds and filtering out isolated insects. TEST constrained with polarimetric measurements was found to be more promising under high-density biota whereas TEST combined with linear depolarization ratio and spectral width perform potentially to filter out biota within the highly turbulent shallow cumulus clouds in the convective boundary layer (CBL). This TEST technique is promisingly simple in realization but powerful in performance due to the flexibility in constraining, identifying and filtering out the biota and screening out the true cloud content, especially the CBL clouds. Therefore, the TEST algorithm is superior for screening out the low-level clouds that are strongly linked to the rainmaking mechanism associated with the Indian Summer Monsoon region's CVS.
ISSN:1867-8548
1867-1381
1867-8548
DOI:10.5194/amt-11-1417-2018