M Roxy Indian Institute of Tropical Meteorology, Pune, India 1. SST - Precip. relationship 2. Spatial variability of SST - Precip. relationship 3. Linearity: Threshold, Quantification Spatial and temporal dimensions of SST-precipitation relationship during the Asian summer monsoon
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M Roxy Indian Institute of Tropical Meteorology, Pune, India 1. SST - Precip. relationship 2. Spatial variability of SST - Precip. relationship 3. Linearity:
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M RoxyIndian Institute of Tropical Meteorology, Pune, India
Spatial and temporal dimensions of SST-precipitation relationship during the Asian summer monsoon
Waliser, D. E., Graham, N. E. & Gautier, C. Comparison of the Highly Reflective Cloud and Outgoing Longwave Radiation Datasets for Use in Estimating Tropical Deep Convection. Journal of Climate 6, 331-353 (1993).
Gadgil, S., Joshi, N. V. & Joseph, P. V. Ocean-atmosphere coupling over monsoon regions. Nature 312, 141-143 (1984).
SST-precipitation relationship over tropics- the upper threshold and
CAPE
Upper threshold of 28.5 - 29.5℃
Explanation given:Precipitation tends to occur where positive convective available potential energy (CAPE) exists
-> the occurrence of deep convection will tend to squelch CAPE?
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SST-precipitation relationship over Indian Ocean
- the upper threshold and CAPE
Sabin, T., Babu, C. & Joseph, P. SST–convection relation over tropical oceans. International Journal of Climatology (2012).
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SST-precipitation relationship over West Pacific- negative relationship at temperatures > 29℃?
Rajendran, K., Nanjundiah, R. S., Gadgil, S. & Srinivasan, J. How good are the simulations of tropical SST–rainfall relationship by IPCC AR4 atmospheric and coupled models? J. Earth System Science, 1-16 (2012).
Latent heat flux (-ve upward) anomalies enhance precipitation by enhancing the moist static energy (Kemball-Cook and Wang 2001)
Mean monsoon winds are westerly !
Roxy & Tanimoto, 2007
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Holt and Raman, 1987.Mean profile of virtual potential temperature θv, for 0600 GMT on 2 June (pre-monsoon) and 11-14 June (onset) from MONEX 79 ship data over Arabian Sea.
SST influence on the destabilization of lower atmospheric column:Virtual potential temperature (θv) over Arabian Sea during pre-active phase
Pre
ssure
θ v (oC)
June
Atmospheric soundings between June 2-14
June 11: pre-active phase
(a) θe1000 anomalies (b) θe700 anomalies
Roxy and Tanimoto 2007
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TMI
Precip. lags SST days Precip. leads SST
The SST-precipitation relationship have different lead-lags over the Arabian Sea and the Bay of Bengal/South China Sea
Spatial variability of SST – Precipitation relationshipresponse time difference of 1 week!
5 days12 days
Ocean -> Atmosphere | Atmosphere -> Ocean
The magnitude of the correlation refers to the intensity of the driving force, and the corresponding lag (lead) time denotes how quickly the atmosphere responds to the SST anomalies and vice versa.
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Role of surface convergence on the response time
Relatively stronger surface convergence over the Arabian Sea accelerates the uplift of the moist air, resulting in a relatively faster response in the local precipitation anomalies