Characteristics of monsoon inversions over the Arabian Sea observed by satellite sounder and reanalysis data sets

Abstract

Abstract. Monsoon inversion (MI) over the Arabian Sea (AS) is one of the important characteristics associated with the monsoon activity over Indian region during summer monsoon season. In the present study, we have used 5 years (2009-2013) of temperature and water vapour measurement data obtained from satellite sounder instrument, an Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp satellite, in addition to ERA-Interim data, to study their characteristics. The lower atmospheric data over the AS have been examined first to identify the areas where MIs are predominant and occur with higher strength. Based on this information, a detailed study has been made to investigate their characteristics separately in the eastern AS (EAS) and western AS (WAS) to examine their contrasting features. The initiation and dissipation times of MIs, their percentage occurrence, strength, etc., has been examined using the huge database. The relation with monsoon activity (rainfall) over Indian region during normal and poor monsoon years is also studied. WAS T values are ∼ 2 K less than those over the EAS, T being the temperature difference between 950 and 850 hPa. A much larger contrast between the WAS and EAS in T is noticed in ERA-Interim data set vis-à-vis those observed by satellites. The possibility of detecting MI from another parameter, refractivity N, obtained directly from another satellite constellation of GPS Radio Occultation (RO) (COSMIC), has also been examined. MI detected from IASI and Atmospheric Infrared Sounder (AIRS) onboard the NOAA satellite have been compared to see how far the two data sets can be combined to study the MI characteristics. We suggest MI could also be included as one of the semipermanent features of southwest monsoon along with the presently accepted six parameters.

Variability of monsoon low‐level jet and associated rainfall over India

“…The MLLJ is formed primarily from the cross‐equatorial flow induced by differential heating in the summer hemisphere (between the latitudes 20°N and 20°S), which creates pressure gradient forces of heat lows over the Indian subcontinent and Mascarene High (Krishnamurti and Bhalme, ; Murakami, ; Hart, ). MLLJ winds blow primarily at heights between 1,000 and 4,000 m, with a core of jet at around 1,500 m above mean sea level (Boos and Emanuel, ), transport moisture from the Southern to Northern Hemisphere (Cadet and Reverdin, ; Roxy et al ., ), and also control the formation and maintenance of monsoon inversion layers over the western central Arabian Sea (Sathiyamoorthy et al ., ; Dwivedi et al ., ). The MLLJ also plays a major role in modulating the amount of rainfall over the Indian subcontinent (Wu et al ., ), in the active‐break monsoon rainfall spells, and intra‐seasonal oscillations of the ISM (Sam and Vittal Murty, ; Joseph and Sijikumar, ).…”

“…For instance, the passage of warm, dry, and dust‐laden Shamal winds (from the east Arabian Peninsula) and Levar winds (through mountains gaps in the southeast Iran) over the cold and moist monsoonal air mass triggers the development of positive lapse rates and creates the thermal inversion layers over the western Arabian Sea (Narayanan and Rao, ). The formation of the thermal inversion layers, called monsoon inversion, plays a major role in controlling the moisture budget in the lower and mid‐troposphere over the WAS, and also in transporting moisture towards the Indian subcontinent (Narayanan and Rao, ; Dwivedi et al ., ; Ramaswamy et al ., ). The monsoonal winds funnelled through gaps of the East Africa region (ISM winds from the Tokar gap) strongly constitute to the actual strength and spatial extent of MLLJ over the western Arabian Sea.…”

World marine fog analysis based on 58‐years of ship observations

“…A fifth upwelling zone is located along southeast Arabia during the summer monsoon, with winds toward the northeast (Schott and McCreary, 2001;Tomczak and Godfrey, 2003). Here, surface divergence causes subsiding air and an air temperature inversion (Ramage, 1971, Dwivedi et al, 2016. For all five zones, there is a This article is protected by copyright.…”

Enhanced Simulation of the Indian Summer Monsoon Rainfall Using Regional Climate Modeling and Continuous Data Assimilation

“…The monsoon low-level jet (MLLJ), a southwesterly wind-flow confined to a narrow region over the western Arabian Sea, is a prime indicator of the ISM circulation (Joseph and Raman, 1966;Findlater, 1969). The MLLJ originates from cross-equatorial flow and acts as an important driver for transporting moisture toward the Indian region, controlling the monsoon inversion layers over the west central Arabian Sea (Dwivedi et al, 2016(Dwivedi et al, , 2021. The MLLJ further feeds moisture to the monsoon depressions formed over the Bay of Bengal (BoB) (Nagar et al, 2009;Walker et al, 2015) and modulate the rainfall over India (Roxy et al, 2017;Viswanadhapalli et al, 2020).…”

“…This also influences the exchange of moisture and energy between the ocean surfaces (Narayanan and Rao, 1981). The difference in temperature between the pressure levels of 850 and 950 hPa [ T = T 850hPa -T 950hPa )] is used here to identify the MI (Dwivedi et al, 2016(Dwivedi et al, , 2021 for all WRF downscaling experiments during the three studied monsoon seasons and is compared with that of ERA5 (Figure 8). Muraleedharan et al (2013) revealed that higher (lower) MI values over the western Arabian Sea are associated with the active (break) phases of the ISM.…”