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Onset of Indian summer monsoon over Gadanki (13.5°N, 79.2°E): Study using lower atmospheric wind profiler
Author(s) -
Jagannadha Rao V. V. M.,
Roja Raman M.,
Venkat Ratnam M.,
Narayana Rao D.,
Bhaskara Rao S. Vijaya
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl031592
Subject(s) - wind profiler , wind speed , monsoon , westerlies , environmental science , atmospheric sciences , radar , climatology , meteorology , geology , physics , telecommunications , computer science
The onset of Indian summer monsoon (ISM) over Gadanki (13.5°N; 79.2°E) is identified using variations in signal‐to‐noise ratio (SNR), wind speed, wind direction and vertical velocity at 1.5 km (∼850 hPa) using lower atmospheric wind profiler (LAWP). Strengthening of the low level wind speed attaining 8 ms −1 with directional change from south‐easterlies to south‐westerlies defines the beginning of the monsoon. Enhancement in SNR few days before with noticeable magnitude of 5–10 dB at the time of onset combined with clear‐air vertical velocity reversal from downward to upward few days before onset and persisting during monsoon activity supplements the wind speed criteria in identifying onset. Hydrometeor velocity shows large downward values exceeding more than 1 ms −1 indicating occurrence of rainfall. It is proposed that UHF radar at a location can be used to identify the onset of ISM based on wind speed without considering rainfall separately.