A study on the characteristics of temperature inversions in active and break phases of Indian summer monsoon

Muraleedharan, P.M.; Mohankumar, K.; Sivakumar, K.

doi:10.1016/j.jastp.2012.11.006

Cited by 15 publications

(16 citation statements)

References 12 publications

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“…These results are in agreement with earlier studies (e.g. Muraleedharan et al , ). Similarly, anomalous easterly flow is observed at upper level over subtropical belt resulting in anomalous cyclonic vorticity over east central India (Figure S3(b)).…”

Section: Resultssupporting

confidence: 94%

“…Ramamurthy, ; Gadgil and Joseph, ; Vellore et al , ). Also an anomalous westerly flow prevails over northern India resulting in anomalous anticyclonic vorticity over central India (see also Ramamurthy, ; Rajeevan et al , ; Muraleedharan et al , ). At the upper level, the easterly jet is slightly stronger and broader than usual and is elongated from peninsular India westwards with zonal wind flow (Figure S3(c), see also Sathiyamoorthy et al , ; Vellore et al , ).…”

Section: Resultsmentioning

confidence: 99%

“…In the observations, the position of the active composite monsoon trough is distinct from its composite positions on the lag and lead days especially over west India and the entire length of the trough is located over central India, south of its normal position (Muraleedharan et al, 2013), with roughly east-west orientation (Figure 7(a), also see Choudhury and Krishnan, 2011), which is conducive for precipitation enhancement over the core monsoon zone and suppression in other regions. Also, lows and depressions frequently form over BoB and move across the core monsoon zone in this phase (Rajeevan et al, 2010).…”

Section: Progression Of the Composite Monsoon Troughmentioning

confidence: 96%

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Added value of a high‐resolution regional climate model in simulation of intraseasonal variability of the South Asian summer monsoon

Karmacharya

New

Jones

et al. 2016

Intl Journal of Climatology

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The South Asian summer monsoon (SASM) exhibits large variability in the intraseasonal scale, and active and break cycles of monsoon constitute dominant mode of this variability. This has been subject of many model‐based studies as improved simulation of intraseasonal features also leads to better representation of the seasonal mean characteristics. We evaluate a recent Hadley centre regional climate model's performance, at low and high resolutions and forced by a reanalysis, in simulating various characteristics associated with intraseasonal variability of SASM. In particular, we compare the spatial patterns of precipitation and upper level circulation composites for active and break spells and, timing, frequency and duration of those spells. We found improvements in simulation of active and break composite precipitation in the high‐resolution simulation. These improvements probably come from improved position of the monsoon trough particularly over west India for active composite and improved low‐level flow particularly south of the Himalaya for break composite. Moreover, enhanced capacity of the model at high resolution to resolve atmospheric motions and interaction of moisture laden low‐level flow with the steep Himalayan orography is likely to contribute in reduction of excess precipitation over Indo‐Gangetic plain. Similarly, improvements over east Nepal for break spells are likely to come from model's ability to effectively capture precipitation enhancements that arise from orographic‐forced and mid‐tropospheric ascending motions. However, mixed results are obtained for temporal statistics associated with occurrence of active and break events. We also compare the model performance in simulating precipitation extremes over Nepal. The timing of extreme precipitation occurrence in relation to peak monsoon months and break spells, and contribution of the extreme cumulative precipitation to the seasonal total are improved in the high‐resolution simulation.

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Section: Resultssupporting

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Progression Of the Composite Monsoon Troughmentioning

confidence: 96%

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Added value of a high‐resolution regional climate model in simulation of intraseasonal variability of the South Asian summer monsoon

Karmacharya

New

Jones

et al. 2016

Intl Journal of Climatology

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“…() identified that summer shamal winds lifts the dust from the Tigris–Euphrates Basin, Kuwait and Arabian Peninsula and transports it in the southeastwards direction. The occurrence of shamal winds in the Arabian Sea during summer has obvious links with break‐monsoons; that is, the monsoonal winds become weaker during the dominance of shamals (Aboobacker et al ., ; Glejin et al ., ; Muraleedharan et al ., ).…”

Section: Introductionmentioning

confidence: 97%

The climatology of shamals in the Arabian Sea—Part 1: Surface winds

Aboobacker¹,

Shanas²

2018

Intl Journal of Climatology

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This study describes the climatology of shamal winds in the Arabian Sea using recent 30 years of ERA-Interim winds. The shamal events were distinguished based on the typical directions, duration and intensity of the winds. Three potential zones of shamal winds were identified in the northwestern Arabian Sea, which are the areas where the predominant shamal swells have been generated. The number of events, duration and intensity of shamal winds were estimated for various months and years. The climatology and trends of shamal winds were derived and the spatial extent of the winds was assessed. The results show that the number of events and the duration of shamals decrease in the northwestern Arabian Sea. Contrasting trends have been observed in the shamal intensities-significant positive trends in the Gulf of Oman and significant negative trends along the east coast of Oman. The trends of the total winds are in contrast with those of the shamals winds.

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“…It was observed that both the LLJ and CBL were elevated during afternoon hours on the non-rainy (dry episode) days over Gadanki (13.45 • N, 79.2 • E). The lower tropospheric temperature inversions at about 2-3 km (generally representing the CBL) are observed to be weak during the break phase due to weakening of the LLJ (Muraleedharan et al, 2013). Raman et al (1990) reported the distinct thermal structure of the ABL during premonsoon and monsoon months.…”

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confidence: 97%

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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A study on the characteristics of temperature inversions in active and break phases of Indian summer monsoon

Cited by 15 publications

References 12 publications

Added value of a high‐resolution regional climate model in simulation of intraseasonal variability of the South Asian summer monsoon

Added value of a high‐resolution regional climate model in simulation of intraseasonal variability of the South Asian summer monsoon

The climatology of shamals in the Arabian Sea—Part 1: Surface winds

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

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