Detection of Rain/Cloud Pixels by Ka-band AltiKa Altimeter over the Tropical Region: Development of a Rain/Cloud Flag Algorithm and its Validation
A rain/cloud flagging algorithm for the AltiKa waveform is developed. For this purpose, Mean Power Count between 13 and 40 gates
absolute value of off-nadir angle of Altika waveform are utilized against the backdrop of Liquid Water Content (LWC) > 0.25 kg m−2.
It is observed that parameter is also affected by strong low-level jet. During the validation phase at near simultaneous time scale with 3B42
rainfall over the Indian Ocean, Probability of Detection (POD) and False Alarm Ratio (FAR) of Flag 1 (for LWC > 0.25 kg m−2) are found to be 0.76 and 0.19, respectively. Similarly POD and FAR of Flag 0 (for LWC ≤ 0.25 kg m−2) are found to be
0.90 and 0.11, respectively. Over the tropics during March 2013 to February 2014, the developed algorithm has detected 6.88% of Flag 1, of which 4.41% are due to rain/cloud, and the remaining 2.48% of flags are primarily due to strong low-level jet. Overall correlation coefficient between
occurrence of Flag 1 due to rain/cloud and 3B42 rainfall is found to be 0.76. The developed algorithm is reasonably robust for detecting rain/cloud pixels.
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Document Type: Research Article
Affiliations: 1: Kohima Science College, Jotsoma, Kohima, Nagaland, India 2: Meteorology and Oceanography Group, Space Application Centre, Ahmedabad, India
Publication date: September 10, 2015