Observations of the thermodynamic structure of marine atmospheric boundary layer over Bay of Bengal, Northern Indian Ocean and Arabian Sea during premonsoon period

Alappattu, Denny P.; Kunhikrishnan, P. K.

doi:10.1016/j.jastp.2010.07.011

Cited by 12 publications

(8 citation statements)

References 35 publications

(54 reference statements)

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“…One of the important thermodynamic structures is the prevalence of fair-weather clouds, especially during the monsoon season, over the Indian region. These FWBLs are characterized by a sharp decrease in the humidity (RH and q) and θ v and an increase in the θ es , similar to trade wind inversions over the ocean (Subrahamanyam and Ramachandran, 2003;Ramana et al, 2004;Alappattu and Kunhikrishnan, 2010). We have shown that the FWBL can also be identified by the local minimum in the N .…”

Section: Discussionsupporting

confidence: 70%

“…The thermodynamic structure of the CBL is still poorly known, especially over land in the Indian monsoon region (Parasnis and Goyal, 1990). Over the adjoining sea, extensive studies have been conducted to understand the thermodynamic structure of the marine ABL (Subrahamanyam and Ramachandran, 2003;Ramana et al, 2004;Alappattu and Kunhikrishnan, 2010). Since routine radiosonde basically covers the morning (05:30 IST) and evening (17:30 IST) transition phase, the well-developed CBL cannot be studied using these observations.…”

Section: Discussionmentioning

confidence: 99%

“…Cloudiness and rainfall are generally associated with the monsoon trough. Over the ocean the trade wind inversions are a permanent feature and have been observed over the Atlantic (Augstein, 1978;Schubert et al, 1995), tropical eastern Pacific (Schubert et al, 1995;Johnson et al, 1996), and Indian oceans (Ramana et al, 2004), the Arabian Sea (Subrahamanyam and Ramachandran, 2003;Alappattu and Kunhikrishnan, 2010), and the Bay of Bengal (Alappattu and Kunhikrishnan, 2010), which is one of the characteristics of the marine boundary layer. In close analogy to the trade wind inversion layer over the ocean, the fair-weather boundary layer (FWBL) with a CBL below shallow cumulus is gen-erally observed over land (Medeiros et al, 2005).…”

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confidence: 99%

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Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

et al. 2017

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Abstract. Spatial and temporal variability in the convective boundary layer (CBL) height for the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) study period are examined using the data collected from high-resolution radiosondes during May-September 2009 over the Indian monsoon region. In total, 57 radiosonde launchings were carried out at ∼ 11:00-17:00 IST over six different stations covering a large geographical region, ranging from latitude ∼ 13 to 32 • N and longitude 73 to 92 • E. Of the total 57 launchings, 17 were made during cloudy conditions during which relative humidity (RH) was found to be greater than 83 % for an ∼ 1.0 km layer at various altitudes below 6 km. Within the layer the difference between saturated equivalent potential temperature and equivalent potential temperature is small, and it satisfies the condition that RH > 83 % for about 1 km is considered as the cloudy layer. There are eight cases when the cloud-topped boundary layer (CTBL) and 19 cases when fair-weather boundary layer (FWBL) is observed. The CBL heights are obtained using thermodynamic profiles, which vary from ∼ 0.4 to 2.5 km a.g.l. The formation of the cloud layers above the boundary layer generally lowers the CBL height and is responsible for its day-to-day variability. The development of the cloud beneath the boundary layer generally elevates the CBL, which is also responsible for the large day-to-day variability in the CBL. The FWBL identified using relative invariance of the thermodynamic profiles varies from ∼ 2.0 to 5.5 km, which is clearly marked by a local minimum in the refractivity gradient. During cloudy days, the CBL is found to be shallow and the surface temperature lower when compared to clear-sky days. The CBL and the lifting condensation level (LCL) heights are randomly related and are found to be at a lower height during cloudy days when compared to clear-sky days. Finally, the typical comparison between the CBL height obtained using thermodynamic profiles and backscattering profiles using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is examined.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

et al. 2017

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“…Other authors, however, differentiate the TWI layer from the inversion produced at the top of the mixing layer Sempreviva and Gryning 2000) where the largest relative humidity gradient is observed (Ma et al 1996;Philander et al 1996;Von Engeln et al 2005;Cao et al 2007). This idea is mainly supported by a double structure that has been observed in stability (dT/dz) in typical trade-wind soundings Rouault et al 1999;Sempreviva and Gryning 2000;Von Engeln et al 2005;Zhang et al 2009;Alappattu and Kunhikrishnan 2010;Rémillard et al 2012). Johnson et al (1995) found high stability in layers centred near the 925-, 800-and 550-hPa levels, and suggested that the stability peak near 925 hPa represented the inversion above the mixing layer, and that the stability layer around 800 hPa was associated with the TWI.…”

Section: Introductionmentioning

confidence: 76%

Characterization of the Marine Boundary Layer and the Trade-Wind Inversion over the Sub-tropical North Atlantic

Carrillo

Guerra

Cuevas

et al. 2015

Boundary-Layer Meteorol

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The stability of the lower troposphere along the east side of the sub-tropical North Atlantic is analyzed and characterized using upper air meteorological long-term records at the Canary Islands (Tenerife), Madeira (Madeira) and Azores (Terceira) archipelagos. The most remarkable characteristic is the strong stratification observed in the lower troposphere, with a strengthening of stability centred at levels near 900 and 800 hPa in a significant percentage of soundings (ranging from 17 % in Azores to 33 % in Güimar, Canary Islands). We show that this double structure is associated with the top of the marine boundary layer (MBL) and the trade-wind inversion (TWI) respectively. The top of the MBL coincides with the base of the first temperature inversion (≈900 hPa) where a sharp change in water vapour mixing ratio is observed. A second temperature inversion is found near 800 hPa, which is characterized by a large directional wind shear just above the inversion layer, tied to the TWI. We find that seasonal and latitudinal variations of the height and strength of both temperature inversions are driven by large-scale subsiding air from the upper troposphere associated with the descent branch of the Hadley cell. Increased general subsidence in summertime enhances stability in the lower troposphere, more markedly in the southern stations, where the inversion-layer heights are found at lower levels enhancing the main features of these two temperature inversions. A simple conceptual model that explains the lower tropospheric inversion enhancement by subsidence is proposed. Electronic supplementary materialThe online version of this article (

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“…In addition to modern detection methods, such as sodar and radar acoustic sounding systems, tethered balloon observations are still being conducted in some areas to determine ABL structures (Neff et al, 2008;Hanna et al, 2006;Emeis et al, 2004;Alappattu and Kunhikrishnan, 2010). Data from tethered balloon observations show that light wind and lower inversion at nighttime in urban areas are important factors that contribute to poor air quality (Kolev et al, 2000;Sang et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Observational studies of the meteorological characteristics associated with poor air quality over the Pearl River Delta in China

Fan

et al. 2013

Atmos. Chem. Phys.

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Abstract. The structure of the atmospheric boundary layer (ABL) and its influence on regional air quality over the Pearl River Delta (PRD) were examined through two intensive observations in October 2004 and July 2006. Analytical results show the presence of two types of typical weather conditions associated with poor air quality over the PRD. The first is the warm period before a cold front (WPBCF) and the second is the subsidence period controlled by a tropical cyclone (SPCTC). Two typical low air quality situations, which are affected by WPBCF and SPCTC, and one high air quality situation were analysed in detail. Results showed that continuously low or calm ground winds resulted in the accumulation of pollutants, and sea-land breezes had an important role during low air quality conditions. Data on recirculation factors showed that recirculation was significant during low air quality conditions, and steady transportation occurred during high air quality conditions. The ventilation index and the 24 h average ventilation index during high air quality conditions were significantly higher than those during low air quality conditions. Deep and stable inversion layers inside the ABL remarkably affected low air quality. Surface and low-altitude inversions were usually observed during WPBCF, contrary to during SPCTC, during which only the low-altitude inversion appeared frequently.

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Observations of the thermodynamic structure of marine atmospheric boundary layer over Bay of Bengal, Northern Indian Ocean and Arabian Sea during premonsoon period

Cited by 12 publications

References 35 publications

Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

Thermodynamic structure of the convective boundary layer (CBL) over the Indian monsoon region during CAIPEEX campaigns

Characterization of the Marine Boundary Layer and the Trade-Wind Inversion over the Sub-tropical North Atlantic

Observational studies of the meteorological characteristics associated with poor air quality over the Pearl River Delta in China

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