scholarly journals Interactions among deep convection, sea surface temperature and radiation in the Asian monsoon region

MAUSAM ◽  
2021 ◽  
Vol 52 (1) ◽  
pp. 83-96
Author(s):  
M. RAJEEVAN
Keyword(s):  
Indian Ocean ◽  
Radiative Forcing ◽  
Asian Monsoon ◽  
Deep Convection ◽  
Ocean Basin ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Cloud Radiative Forcing ◽  
Convective Clouds ◽  
The Indian Ocean

The climatic interactions among deep convection, sea surface temperature and radiation in the Asian monsoon region have been examined using various satellite-derived data sets of the period 1983-90. Annual average Frequency of Deep Convection (FDC) is maximum over the equatorial east Indian ocean and adjoining west Pacific and Indonesian region. Maximum FDC zone shifts to Bay of Bengal during the monsoon (June-September) season.   There is weak relationship between the variations in FDC and SST in the Indian ocean. Deep convective activity was suppressed over most of the tropical Indian ocean during El Nino of 1987 in spite of warmer SSTs. The pattern of inter-annual variation between FDC and SST behaves differently in the Indian ocean basin as compared to the Pacific ocean basin. Deep convective clouds interact with radiation very effectively in the Asian monsoon region to cause large net negative cloud radiative forcing. Variation in FDC explains more than 70% of the variation in surface short-wave cloud radiative forcing (SWCRF) and long wave cloud radiative forcing (LWCRF) in the atmosphere.   On inter-annual scale, warmer SSTs may not necessarily increase deep convection in the Indian ocean. However, the inter-annual variation of deep convective clouds influences significantly the radiative budget of the surface-atmosphere system in the Asian monsoon region. The satellite observations suggest that warmer SSTs in the Indian ocean might have resulted from an increase in the absorbed solar radiation at the surface due to a reduction in deep convective cloud cover.

Role of vertical structure of cloud microphysical properties on cloud radiative forcing over the Asian monsoon region

2015 ◽  
Vol 45 (11-12) ◽  
pp. 3331-3345 ◽  
Author(s):  
V. Ravi Kiran ◽  
M. Rajeevan ◽  
H. Gadhavi ◽  
S. Vijaya Bhaskara Rao ◽  
A. Jayaraman
Keyword(s):  
Radiative Forcing ◽  
Vertical Structure ◽  
Asian Monsoon ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Cloud Radiative Forcing ◽  
Microphysical Properties

scholarly journals Ten Years of Measurements of Tropical Upper-Tropospheric Water Vapor by MOZAIC. Part I: Climatology, Variability, Transport, and Relation to Deep Convection

2007 ◽  
Vol 20 (3) ◽  
pp. 418-435 ◽  
Author(s):  
Zhengzhao Luo ◽  
Dieter Kley ◽  
Richard H. Johnson ◽  
Herman Smit
Keyword(s):  
Water Vapor ◽  
Asian Monsoon ◽  
Deep Convection ◽  
Seasonal Migration ◽  
Specific Humidity ◽  
Tropical Atlantic ◽  
Monsoon Region ◽  
Tropical Africa ◽  
Asian Monsoon Region ◽  
The Mean

Abstract Ten years (1994–2004) of measurements of tropical upper-tropospheric water vapor (UTWV) by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) are investigated over three regions—the tropical Atlantic, tropical Africa, and the Asian monsoon region—to determine the UTWV climatology and variability on multiple scales and to understand them in relation to moisture transport and deep convection. The seasonal migration of upper-tropospheric humidity (UTH) keeps pace with that of the ITCZ, indicating the convective influence on UTH distribution. Some significant regional differences are identified with the tropical Africa and the Asian monsoon regions being moister than the tropical Atlantic. UTH generally increases with height by 10%–20% relative humidity with respect to ice (RHi) from about 300 to 200 hPa, and the differences are larger in the deep Tropics than in the subtropics. The probability density functions of tropical UTH are often bimodal. The two modes stay rather constant; differences in the mean value are largely due to the variations in the proportion of the two modes as opposed to changes in the modes themselves. In the deep Tropics, the moisture level frequently reaches ice supersaturation, the most notable case being the near-equatorial Asian monsoon region during the wet season when ice supersaturation is observed 46% of the time. Interannual variations are observed in association with the 1997–98 ENSO event. A warming of about 1–2 K is observed for all three regions equatorward of roughly 15°. Specific humidity also increases somewhat for the tropical Atlantic and tropical Africa, but the increase in temperature outweighs the increase in specific humidity such that RH decreases by 5%–15% RHi. In addition to the ENSO-related variation, MOZAIC also sees increases in both RH and specific humidity over tropical Africa from 2000 onward. Moisture fluxes are computed from MOZAIC data and decomposed into contributions from the mean circulation and from eddies. The flux divergence, which represents the moisture source/sink from horizontal transport, is also estimated. Finally, the MOZAIC climatology and variability are revisited in relation to deep convection obtained from the International Satellite Cloud Climatology Project (ISCCP).

Linking Observations of the Asian Monsoon to the Indian Ocean SST: Possible Roles of Indian Ocean Basin Mode and Dipole Mode

2010 ◽  
Vol 23 (21) ◽  
pp. 5889-5902 ◽  
Author(s):  
Jianling Yang ◽  
Qinyu Liu ◽  
Zhengyu Liu
Keyword(s):  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Summer Monsoon ◽  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Ocean Basin ◽  
Indian Ocean Basin Mode ◽  
Basin Mode ◽  
The Indian Ocean ◽  
Asian Summer

Abstract The authors investigate the relationship between sea surface temperature (SST) in the tropical Indian Ocean (TIO) and the seasonal atmosphere circulation in the Asian monsoon region (AMR) using the maximum covariance analyses (MCAs). The results show that the Asian monsoon circulation is significantly correlated with two dominant SST anomaly (SSTA) modes: the Indian Ocean Basin mode (IOB) and the Indian Ocean dipole mode (IOD). The peak SSTA of the IOB appears in spring and has a much stronger relationship with the Asian summer monsoon than the peak of the IOD does, whereas the peak SSTA for the IOD appears in fall and shows a stronger link to the Asian winter monsoon than to the Asian summer monsoon. In addition, the IOB in spring has a relatively stronger link with the atmospheric circulation in summer than in other seasons. The large-scale atmospheric circulation and SSTA patterns of the covariability of the first two dominant MCA modes are described. For the first MCA mode, a warm IOB, persists from spring to summer, and the atmospheric circulation is enhanced by the establishment of the climatological summer monsoon. The increased evaporative moisture associated with the warm IOB is transported to South Asia by the climatological summer monsoon, which increases the moisture convergence toward this region, leading to a significant increase in summer monsoon precipitation. For the second MCA mode, a positive IOD possibly corresponds to a weaker Indian winter monsoon and more precipitation over the southwestern and eastern equatorial TIO.

Intercomparison of Deep Convection over the Tibetan Plateau–Asian Monsoon Region and Subtropical North America in Boreal Summer Using CloudSat/CALIPSO Data

2011 ◽  
Vol 24 (8) ◽  
pp. 2164-2177 ◽  
Author(s):  
Yali Luo ◽  
Renhe Zhang ◽  
Weimiao Qian ◽  
Zhengzhao Luo ◽  
Xin Hu
Keyword(s):  
North America ◽  
Tibetan Plateau ◽  
Asian Monsoon ◽  
Deep Convection ◽  
Local Environment ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Cloud Tops

Abstract Deep convection in the Tibetan Plateau–southern Asian monsoon region (TP–SAMR) is analyzed using CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data for the boreal summer season (June–August) from 2006 to 2009. Three subregions are defined—the TP, the southern slope of the plateau (PSS), and the SAMR—and deep convection properties (such as occurrence frequency, internal vertical structure, system size, and local environment) are compared among these subregions. To cast them in a broader context, four additional regions that bear some similarity to the TP–SAMR are also discussed: East Asia (EA), tropical northwestern Pacific (NWP), and western and eastern North America (WNA and ENA, respectively). The principal findings are as follows: 1) Compared to the other two subregions of the TP–SAMR, deep convection over the TP is shallower, less frequent, and embedded in smaller-size convection systems, but the cloud tops are more densely packed. These characteristics of deep convection over the TP are closely related to the unique local environment, namely, a significantly lower level of neutral buoyancy (LNB) and much drier atmosphere. 2) In a broader context in which all seven regions are brought together, deep convection in the two tropical regions (NWP and SAMR; mostly over ocean) is similar in many regards. A similar conclusion can be drawn among the four subtropical continental regions (TP, EA, WNA, and ENA). However, tropical oceanic and subtropical land regions present some significant contrasts: deep convection in the latter region occurs less frequently, has lower cloud tops but comparable or slightly higher tops of large radar echo (e.g., 0 and 10 dBZ), and is embedded in smaller systems. The cloud tops of the subtropical land regions are generally more densely packed. Hence, the difference between the TP and SAMR is more of a general contrast between subtropical land regions and tropical oceanic regions during the boreal summer. 3) Deep convection over the PSS possesses some uniqueness of its own because of the distinctive terrain (slopes) and moist low-level monsoon flow. 4) Results from a comparison between the daytime (1:30 p.m.) and nighttime (1:30 a.m.) overpasses are largely consistent with researchers’ general understanding of the diurnal variation of tropical and subtropical deep convection.

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