Thermodynamic features of the atmospheric boundary layer during the summer monsoon

Parasnis, Surendra S.; Goyal, S.S.

doi:10.1016/0960-1686(90)90275-r

Cited by 18 publications

(8 citation statements)

References 18 publications

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“…Thermal and wind structures of the boundary layer during the monsoon seasons were extensively studied using radiosonde and sodars [Parasnis and Goyal, 1990;Rajkumar et al, 1996]. In one of the interesting studies, Kusuma et al [1991] reported boundary layer heights over the monsoon trough region during active and break phases.…”

Section: Introductionmentioning

confidence: 99%

L band wind profiler observations of convective boundary layer over Gadanki, India (13.5°N, 79.2°E)

Kumar

Jain

2006

Radio Science

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[1] Results from a convection campaign, which was carried out during May-August 1999 using VHF/L band wind profiler, optical rain gauge, and radiosonde flights at National MST Radar Facility, Gadanki (13.5°N, 79.2°E), are discussed. During this period, L band wind profiler observations have been made for a total of 110 days, and radiosonde observations have been made during 19 July to 14 August 1999. L band wind profiler-derived refractive index structure constant profiles have been used to estimate the convective boundary layer (CBL) height and are compared with radiosonde observations. Comparison has shown a good agreement with a regression coefficient of 0.84 between these two independent measurements. Radiosonde observations are also used to estimate the level of free convection, which are used for studying the triggering of convection. An attempt has been made to study the evolution of the CBL in dry convection (nonprecipitating) and precipitation days. Precipitation days comprise both premonsoon and monsoon seasons. In the present study, premonsoon days are defined as the dry to wet transition period and monsoon days as the early monsoon period. The intriguing result from these studies is the distinguishable CBL evolution observed in the preconvective environments of premonsoon and monsoon periods. These observations provide evidence for the use of wind profilers to closely monitor the onset of convective instability. Furthermore, observations of the boundary layer at various geographical locations using multiplatform instruments are sought to strengthen the results depicted here. However, the results discussed here nevertheless prove the potential of the L band wind profiler as an important tool for operational meteorology and provide new insights on the usage of wind profiler observations.

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Section: Introductionmentioning

confidence: 99%

L band wind profiler observations of convective boundary layer over Gadanki, India (13.5°N, 79.2°E)

Kumar

Jain

2006

Radio Science

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“…These stations cover a large geographical region, ranging from latitude ∼ 13 to 32 • N to longitude 73 to 92 • E. Using routine radiosonde (at 05:30 and 17:30 IST), the CBL has been extensively studied (Seidel et al, 2010). 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).…”

Section: Discussionmentioning

confidence: 99%

“…The Indian summer monsoon is dominated by synoptic-scale cloudiness and precipitations associated with a cycle of active and break spells (Webster et al, 1998;Goswami, 2005). There have been several studies on the ABL characteristics over the Indian region during summer monsoon season (Holt and Raman, 1987;Parasnis and Goyal, 1990;Raman et al, 1990;Kusuma et al, 1991;Joseph and Sijikumar, 2004;Roja Raman et al, 2011;Satyanarayana Mohan and Narayana Rao, 2012;Sandeep et al, 2014Sandeep et al, , 2015Mehta et al, 2017). In general, the CBL is shallower during the active monsoon conditions when compared to break monsoon conditions (Satyanarayana Mohan and Narayana Rao, 2012;Sandeep et al, 2014).…”

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confidence: 99%

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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“…In that period the monsoon trough was aligned with the Gangetic plains on the 15th and 16th of July and protruded over the Head of the Bay of Bengal. This positioning of the trough usually leads to an active monsoon period, which is usually associated with widespread rainfall over the Indian region (see, e.g., Parasnis and Goyal, 1990). The trough off the west coast of India persisted during the period of observations with a well marked embedded vortex near the coast (at 15" N).…”

Section: Location Of Observations and Meteorological Conditionsmentioning

confidence: 99%

Observations of reversal of mixing ratio in the atmospheric boundary layer over the Arabian sea

Parasnis

1992

Boundary-Layer Meteorol

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Analysis of the radiosonde observations over the Arabian sea region during MONSOON-77 and MONEX-79 has revealed a reversal in the mixing ratio (QR) above the inversion/stable layer in the atmospheric boundary layer. The reversal could be attributed to the detrainment of cloudy air originating in the deep moist convection which has penetrated the inversion layer in nearby areas. It was noticed that the soundings in which a reversal of mixing ratio was not observed, were associated with meteorological conditions favourable for deep convection.

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Thermodynamic features of the atmospheric boundary layer during the summer monsoon

Cited by 18 publications

References 18 publications

L band wind profiler observations of convective boundary layer over Gadanki, India (13.5°N, 79.2°E)

L band wind profiler observations of convective boundary layer over Gadanki, India (13.5°N, 79.2°E)

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

Observations of reversal of mixing ratio in the atmospheric boundary layer over the Arabian sea

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